Marginal and Internal Adaptation of Different Flowable Composite Restorations in Class V Cavities after Thermomechanical Cyclic Loading: In vitro study

Marginal and Internal Adaptation of Different Flowable Composite Restorations in Class V Cavities after Thermomechanical Cyclic Loading: In vitro study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Marginal and Internal Adaptation of Different Flowable Composite Restorations in Class V Cavities after Thermomechanical Cyclic Loading: In vitro study Sahar A. Saleh, Maha M. Ebaya, Ashraf I. Ali This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7446404/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 09 Dec, 2025 Read the published version in BMC Oral Health → Version 1 posted 10 You are reading this latest preprint version Abstract Objective: This study aimed to evaluate and compare marginal and internal adaptation of different flowable composite restorations in class V cavities after thermomechanical cyclic loading. Material and methods: One hundred freshly extracted human premolars with class V cavities on the facial surface were randomly assigned into five main groups (n=20) according to the type of restoration materials. Group I was restored with short fiber-reinforced flowable, group II with self-adhesive flowable, group III with ORMOCER-based bulkfill flowable, group IV with resin-based bulkfill flowable, and group V with injectable flowable. Each group was divided into two equal subgroups (n=10) according to the examination state at Non-Thermomechanical cyclic loading (N-TMC) and after thermomechanical cyclic loading (TMC). However, the TMC subgroup was evaluated after thermomechanical cyclic loading, which involved 5000 thermal cycles (5°±1℃ to 55°±1℃) and simultaneous mechanical stress applied with 100,000 load cycles at 100 N and 4 Hz, and evaluated for marginal and internal adaptation using a scanning electron microscope. The data were statistically analyzed using the Monte Carlo test to compare the studied groups, and the McNemar test was used to compare N-TMC and TMC results, with a statistically significant level set at (P≤0.05). Results: There were no statistically significant differences at N-TMC and TMC results for marginal adaptation when comparing between groups with P = 1.0 and 0.08, respectively. In other ways, there were statistically significant differences when comparing both states in the same groups, with P= 0.007 for group I and P ≤ 0.001 for all other groups. Additionally, there was a statistically significant difference in N-TMC results for internal adaptation when comparing groups with P<0.001, and no statistically significant difference between the groups in the delayed state p = 1.0. Finally, there was a statistically significant difference when comparing N-TMC with TMC in all groups with p <0.001 except group V, where there was no statistically significant difference with P=1.0. Conclusions : Different flowable composite restorations exhibited good marginal and internal adaptation in class V cavities. Short fiber-reinforced flowable composite restorative system had better adaptation than other restorations. Thermomechanical cyclic loading exerted a negative effect on both marginal and internal adaptation Class V cavity Flowable Composite Internal adaptation Marginal adaptation Thermomechanical Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Restoring class V cavities is a common clinical dental procedure, yet it can be technically demanding due to its proximity to the gingiva and challenges with moisture control. This can result in inadequate bonding to the cavity walls and gaps between the restoration material and the tooth. Additionally, the shrinkage forces of resin-based composites can cause interfacial microleakage, potentially leading to marginal discoloration, secondary caries, or loss of retention.[ 1 ] The variations in filler content of resin composites influence whether the material is sculptable or flowable. Flowable composites have a lower filler load and viscosity, which reportedly enhances wettability and adhesion to cavity surfaces and walls. Moreover, these composites feature a lower elastic modulus, leading to increased flexibility and better resistance to flexural stress at the tooth cervix.[ 1 ] However, in the past years, bulk-fill resin-based composites (BF-RBCs) have been introduced to the dental market to address challenges associated with the incremental technique for posterior teeth. Initially, the term bulk-fill referred to resin composites that permitted 4–5 mm increments, suitable for full-body and base bulk-fill techniques.[ 2 ] Additionally, dental restoration adaptation and thermomechanical cycling are crucial for restorative materials' long-term success, impacting durability and function. However, thermomechanical cycling, subjecting materials to temperature changes and mechanical stress, can affect their performance. These cycles cause thermal expansion and contraction, potentially creating gaps between the restoration and tooth structure and leading to wear and fatigue in the material.[ 3 ] This degradation compromises the seal, causes discomfort, or leads to the failure of restoration.[ 4 ] Clinical evaluations of restorations present challenges due to ethical considerations and are costly and time-intensive.[ 5 ] In vitro studies that simulate oral conditions have been conducted to estimate restoration longevity The marginal seal of composite restorations represents an increasing concern. Over the years, in vitro evaluations of the performance of resin adhesives revealed that microleakage and gap formation, mainly at the dentin-composite interface, did not improve at the same rate as did bond strength values Independent of the bonding capacity of an adhesive system, it seems that adhesive restorations are far from assuring a perfect marginal seal, with degradation in time occurring regardless of the product used.[ 6 , 7 ] Marginal and internal integrity results from several parameters related to the forces created by curing contraction, as bond strength alone could not be correlated to the adaptation.[ 8 ] Finally, according to the author's knowledge, there are few studies concerning the marginal and internal adaptation of bulkfill-flowable composite restorative systems after thermomechanical cycling have been published, and more data are still required. Therefore, evaluating the marginal and internal adaptation of different flowable composite restorative systems in class V cavities will be valuable after thermomechanical cyclic loading (TMC). This study was designed to test the null hypothesis that there would be no significant difference in the marginal and internal adaptation of different flowable composite restorative systems in class V cavities Materials This study was done after obtaining ethical approval from the faculty of dentistry's ethical committee under No. (A03012023CD). The sample size calculation was based on a previous study on marginal adaptation.[ 9 ] Using the G power program version 3.1.9.7 to calculate sample size based on an effect size of 1.7, a 2-tailed test, α error = 0.05, and power = 85.0%, the total estimated sample size is 7 in each subgroup, which was increased to 10 for a more valuable result. Specimen selection and preparation: One hundred freshly extracted human premolars from the oral surgery clinic, Faculty of Dentistry, Mansoura University, were selected for this study. They were extracted for orthodontic reasons. The teeth were carefully inspected using light to ensure they were free from caries, restorations, cracks, or other defects. Soft tissue remnants were removed using a hand scaler (Zeffiro; Lascod, Florence, Italy). Teeth were stored in 1% chloramine-T for 48 hours and in distilled water that was changed weekly until usage. Class V cavity with measurements 3 mm mesiodistal (width), 3 mm occluso-gingival (height), and 2 mm axial (depth) was prepared on the facial surface of each tooth, with surface angles kept at 90 degrees without bevel designs. [ 10 , 11 ]. The outline of the cavities was standardized using a stainless steel matrix band, Figure (1) and preparation was performed with a straight-fissure diamond bur no. (SF-41 MANI Ltd., Utsunomiya, Japan) with a water-cooled high-speed handpiece (30,000–50,000 rpm, NSK, Shinagawa City, Japan). Bur was replaced after every five preparations.[ 11 ] All restoration steps were done according to the manufacturer's instructions, and then specimens were randomly divided into five groups based on restorative materials (n = 20) using an online randomizing program ( www.randomizer.com ). Group I was restored with NovaPro Flow (Nanova, Columbia, MO, USA), Group II with Vertise Flow (Kerr, USA), Group III with Admira Fusion X-base (Voco GmbH, Cuxhaven, Germany), Group IV with Venus Bulk Flow One (Kulzer GmbH, Germany), and Group V with G-ænial Universal Injectable (GC Co., Tokyo, Japan). Groups were further divided into two subgroups (n = 10) based on thermomechanical cycling: Subgroup I was examined at non-thermomechanical cycling (N-TMC), and Subgroup II was examined after thermomechanical cycling (TMC) with 5,000 cycles at 5°±1℃ and 55°±1℃, with dwell times of 60 seconds and transfer times of 15 seconds. Using the thermocycling machine (SD Mechatronic thermocycler) and for mechanical stimulation, a total of 100,000 cycles of an occlusal load at 100 N and 4 Hz were applied (SD Mechatronic CS-4, Germany), which represents 6 months in the oral environment.[ 12 ] Figure.(2) Evaluation Marginal Adaptation All teeth are mounted on aluminum stubs and then coated with gold using a sputter coater (Sputter Coating Evaporator, SPI Supply, USA). They were examined under a Scanning electronic microscope (JSM-6510LV, JEOL Ltd., Tokyo, Japan) at magnification x25-200.[ 13 , 14 ] All SEM examinations and measurements were conducted by a single operator experienced in quantitative margin analysis and unaware of the restorative materials. Detectable gaps were checked and calculated at ×200, and images were analyzed using image analysis software (SEM Control User Interface Ver 3.10, JEOL Ltd.). The interface between each material and the substrate was also quantitatively analysed. The marginal adaptation was scored 0 if the interface between the restoration and tooth was continuous and exhibited less than 1 µm gap and scored 1 if the interface had gaps more than 1 µm wide. [ 15 ] Internal Adaptation Evaluation Teeth were sectioned longitudinally with a slow-speed diamond saw (Isomet 4000-Buehler, Lake Bluff, IL, USA) with water coolant in a buccolingual direction. Each specimen received 1 cut to produce 2 slices per specimen. Then, it was mounted on aluminum stubs and coated with gold using a sputter coater (Sputter Coating Evaporator, SPI Supply, USA). The inner side of each slice's material/ dentin interface was evaluated for internal adaptation using SEM using the same technique and parameters mentioned in the marginal adaptation part. The inner side of the restorative material/dentin interface was evaluated for internal adaptation using SEM using the same technique and parameters mentioned in marginal adaptation.[ 13 ] Statistical analysis: Data analysis was performed using SPSS software, version 26 (Chicago: SPSS Inc.). Qualitative data were described using numbers and percentages. The significance of the obtained results was judged at a P.≤ 0.05. The Monte Carlo test was used to compare between studied groups, and the MC Nemar test was used to compare N-TMC and TMC results. Results Marginal Adaptation Examining marginal integrity with SEM in N-TMC or delayed subgroups for comparison among different groups, we observe gaps with all materials of varying sizes in the following order: short fiber-reinforced flowable with very small gaps, followed by resin-based bulk-fill flowable, ORMOCER-based BFF, self-adhering flowable and lastly, conventional flowable composite. These observations were reported as 100% across all groups in the baseline state, with no statistically significant differences (p = 1) with a gap 1 µm. In other ways, these gaps are statically represented when comparing the materials in the same groups, both at N-TMC and in TMC state. A clear and significant difference exists across all groups, indicating an increase of more than 1 µm gaps. All groups show 100%, except for the short fiber-reinforced flowable group, which has 80% with a gap greater than 1 µm and 20% with an intact margin of less than 1 µm, and this supported the SEM finding. As shown in Table (1) and Figure (3). Table 1 Comparison of the marginal adaptation between studied groups between N-TMC versus TMC. Marginal margin ORMOCER-based BFF N = 10 (%) Short fiber reinforced F N = 10(%) BFF N = 10(%) Self-adhering flowable N = 10(%) Injectable flowable composite N = 10(%) Test of significance (Monte Carlo test) N-TMC 1 µm 10(100) 0 10(100) 0 10(100) 0 10(100) 0 10(100) 0 P = 1.0 TMC 1 µm 0 10(100) 2(20) 8(80) 0 10(100) 0 10(100) 0 10(100) Mc = 8.33 P = 0.08 MC Nemar test P < 0.001* P = 0007* P < 0.001* P < 0.001* P < 0.001* *Statistically significant Internal Adaptation Examining internal adaptation integrity with SEM at N-TMC or TMC subgroups for comparison among different groups, we observe gaps with all materials of varying sizes in the following order: short fiber-reinforced flowable with very small gaps, followed by bulk-fill flowable, ORMOCER-based BFF, self-adhering flowable and lastly, injectable flowable composite. These observations were reported as 100% in all groups except injectable flowable composite 10% in the N-TMC examination, with statistically significant differences (P < 0.001*) with a gap of less than 1 µm. Furthermore, no statistically significant difference exists between groups in the TMC state, with P = 1.0 and more than 1 µm gaps. In other words, when comparing the material in the same group N-TMC and the TMC examination, there is a clear significant difference across the first four groups with P < 0.001*, indicating a gap increase of more than 1 µm. At the same time, with injectable flowable composite, there is no statistically significant difference with P = 1.0, and these support the SEM finding. As shown in Table 2 and Figure.(4) Table 2 Comparison of internal adaptation between studied groups and between N- TMC versus TMC Internal adaptation ORMOCER-based BFF N = 10 (%) Short fiber reinforced F N = 10(%) BFF N = 10(%) Self-adhering flowable N = 10(%) Injectable flowable composite N = 10(%) Test of significance (Monte Carlo test ) N-TMC 1 µm 10(100) 0 10(100) 0 10(100) 0 10(100) 0 1(10) 9(90) Mc = 43.90 P < 0.001* TMC 1 µm 0 10(100) 0 10(100) 0 10(100) 0 10(100) 0 10(100) P = 1.0 MC Nemar test P < 0.001* P < 0.001* P < 0.001* P < 0.001* P = 1.0 *Statistically significant Discussion Class V cavities are characterized by their location on the gingival third of the teeth. This poses unique challenges for restorative dentistry, including moisture control, adhesion to enamel, and the potential for high mechanical and thermal stresses due to their proximity to the gingival tissues.[ 16 ] Restoration success in a class V cavity depends mainly on the material's ability to adapt marginally and internally to the cavity walls, ensuring a durable seal that prevents microleakage and secondary caries.[ 17 ] Restorative materials must also withstand occlusal and lateral forces while maintaining biocompatibility and esthetics in this visible dentition area. Advances in restorative materials, particularly bulk-fill flowable composites, have shown promise in overcoming these challenges by improving ease of application, adaptation properties, and mechanical performance.[ 18 ] Selecting an appropriate resin composite and adhesive system in the class V cavity is crucial for restoration success. The main challenge in restoring this type of cavities is ensuring proper marginal adaptation.[ 19 ] Polymerization shrinkage (PS) during resin curing induces internal stress at the tooth-restoration interface, weakening the bond in flexible, porous dentin. This can cause marginal gaps or microleakage, allowing fluids or bacteria to enter, leading to inflammation, secondary caries, or pulp issues. Shrinkage-induced stress can weaken the adhesive and tooth bond, especially when the dentin is too wet.[ 17 ] Bulk-fill flowable materials in class V cavities improve clinical outcomes by reducing postoperative sensitivity and extending restoration longevity. BFF materials address challenges in class V restorations with lower PS, minimizing marginal gaps and reducing the risk of fractures or adhesive failure. Their flowable properties allow close conformation to cavity wall margins.[ 20 ] This enhances internal adaptation and reduces the need for multiple layers, minimizing voids that could weaken the restoration. BFF materials streamline the process, lowering error rates and increasing efficiency. Advanced BFF matches the mechanical properties of traditional composites, making them suitable for stress-bearing areas of class V cavities.[ 21 ] This study used a box-shaped preparation to standardize experimental groups. The consistent cavity configuration minimized variations in preparation techniques, ensuring restorations were evaluated under similar conditions. This approach facilitated reliable comparisons by controlling for differences in cavity geometry that could affect restorative procedure outcomes. [ 22 ]. In Class V cavities, achieving ideal adaptation is particularly challenging due to the higher C-factor inherent in these designs. Scanning Electron Microscopy (SEM) is a vital tool for assessing the marginal adaptation of dental materials. It generates high-resolution images of the tooth-restoration interface, allowing detailed examination of gaps and defects by evaluating the fit, surface morphology, and bonding quality. This helps to identify issues that may affect longevity.[ 23 ] Direct sample analysis using SEM is preferred over replicas, as it avoids replication artifacts and ensures an accurate interface representation.[ 24 , 25 ] This method provides relevant data by examining the materials without alterations from the replica-making process. Overall, SEM accurately evaluates the restoration’s performance, including potential gaps and bacterial or saliva penetration risk.[ 26 ] Gaps of less than 1 µm are generally associated with better marginal and internal adaptation.[ 15 ] This reduces bacterial penetration and longer-lasting restorations. However, even gaps at this small scale should be minimized to prevent long-term risks. More significant gaps (greater than 1 µm) significantly increase the potential for bacterial penetration, leading to secondary caries, marginal breakdown, and restoration failure. Therefore, achieving precise marginal and internal adaptation during restorative procedures is essential for the durability and success of dental restorations.[ 27 ] Gloria Kang GJ et al. [ 27 ] Investigated the effect of bacterial penetration into gaps. It was shown that smaller gap samples had less bacterial penetration. When more significant gaps exist, bacteria easily penetrate to the full depth of the gap, regardless of loading conditions, increasing the incidence of secondary caries formation. This study executed 5,000 thermal cycles to evaluate the direct correlation with the increase in marginal gaps at the dental restoration interface.[ 28 , 29 ] After that, specimens underwent 100,000 cycles of 100 N occlusal load at 4 Hz.[ 29 ] This equates to six months of clinical functionality, assuming that these cycles happen 10 to 25 times a day, as many studies suggest.[ 28 , 30 ] The mechanical simulator provides insights into a material’s performance during prolonged use and how dental restorations react to complex forces in the oral cavity by simulating stress distribution, fatigue, wear, and crack propagation. The simulator considers the physiological traits of human chewing and the direction of jaw movements.[ 12 ] Thermal cycling affects the bonding agent's or adhesive's properties, while mechanical cycling, such as forces from chewing, may stress the bond interface.[ 31 ] This study showed that all groups tested at baseline achieved 100% marginal adaptation integrity without significant differences between groups. Short fiber-reinforced flowable composites (SFRC-F) showed the best results among groups, which may be due to the content of hydroxyapatite fibers, which are particularly beneficial in enhancing bioactivity and mineralization. Hydroxyapatite, a primary component of tooth enamel, can chemically interact with the enamel surface, providing stronger interfacial adhesion due to its similar composition. The presence of hydroxyapatite fibers helps improve the chemical bonding between the composite and enamel, providing excellent initial bond strength. In the BFF resin-based composite group, the matrix comprises multifunctional methacrylate monomers, UDMA, EBADMA, and Bis-EMA. These monomers can achieve a good bond with enamel through the chemical interaction of the monomers with enamel's hydroxyapatite. Also, its flowability allows the composite to fill micro-irregularities in the enamel and cavity walls, ensuring micromechanical retention. This helps the material bond more effectively with the tooth surface by getting into tiny pores or grooves and creating a strong mechanical lock. ORMOCER-based BFF inorganic component is chemically incorporated into the organic polymer, meaning that the material is inherently a hybrid and the two phases (organic and inorganic) are more interconnected at a molecular level, leading to enhanced properties such as reduced shrinkage and more substantial marginal adaptation. The organic resin portion allows the material to bond to the enamel through functional monomers with acid-functional groups such as Bis-EMA, aliphatic dimethacrylate, and UDMA., which can interact with enamel. These monomers can bond chemically to the enamel's mineral content, creating a chemical adhesive bond between the ORMOCER composite and the tooth structure. At the same time, the silicon oxide nanofillers and glass ceramics filler give the material additional durability, strength, and wear resistance, which is crucial for achieving a tight marginal seal. These materials are designed to form substantial, well-sealed restoration with excellent marginal adaptation, reducing the risk of bacterial infiltration and ensuring the long-term success of the restoration. Furthermore, Self-adhesive flowable composites are designed with chemicals that allow them to bond to enamel surfaces chemically. These materials contain functional monomers (like carboxyl and phosphoric acid groups) capable of interacting with the mineral components in enamel, even without the need for etching. These monomers help form a bond with the tooth structure by chemically interacting with hydroxyapatite, the main component of enamel.[ 32 ] Injectable flowable material had good marginal adaptation integrity, possibly due to its high flow, meaning low viscosity. This allows it to adapt to enamel surfaces and fill intricate cavities easily. It also penetrates micro-irregularities and creates close contact with the enamel while maintaining a smooth surface. Also, Agarwal et al. [ 33 ] Finds that all tested materials showed acceptable marginal adaptation in enamel before TMC. Unfortunately, this level of adaptation declined after TMC. In addition, Tonetto et al. [ 12 ] Demonstrated that TMC obstructed the marginal adaptation of enamel in every group compared to the initial conditions, and both agreed with our findings. Furthermore, this aligns with the results of Abdelwahed et al. [ 34 ] Who stated that no group, regardless of the restorative materials utilized, achieved 100% continuous margins. According to the SEM assessment after TMC group, the SFRC-BFF group showed less discontinuous margin to the enamel, followed by the BFF group, then the ORMOCER-based BFF group, then self-adhesive flowable, and finally injectable flowable. However, there was no statistically significant difference among groups in the delayed examination. Only the SFRC-BFF maintained marginal integrity, with 20% of specimens exhibiting this quality. This may be due to the incorporation of short fibers in flowable composites significantly reducing PS. The presence of short fibers helps the resin retain its structural integrity during the curing process, minimizing the shrinkage process.[ 35 ] SFRC-BFF typically have a higher content of fillers. The filler system in this material, usually made from silica and/or barium glass, plays an equally important role in the material’s cyclic aging resistance. These fillers contribute to Wear resistance, providing abrasion resistance and helping the material maintain its integrity during the masticatory cycle. This is especially important for preventing marginal deterioration after the material undergoes repeated mechanical stress. The dimensional stability of inorganic fillers helps maintain the composite’s shape and structure during thermal cycling (heating and cooling), preventing excessive expansion or contraction. This helps avoid forming marginal gaps that could lead to microleakage or secondary caries.[ 36 ] A study by Roggendorf et al. [ 37 ] Stated that gap-free margins were primarily found under thermomechanical stress conditions. And ElAziz et al. [ 38 ] Who evaluated flowable short fiber-reinforced flowable composite restorations compared to conventional packable composites and found no significant differences between the groups, noting an increase in gaps in marginal integrity after 6 and 12 months. The BFF resin-based composite group showed open enamel margins after cyclic aging, likely due to the fluoride-releasing Ytterbium Fluoride (YbF3). Fluoride promotes hydrolytic degradation of the resin matrix, increasing water sorption in the composite over time. This can lead to resin softening and ultimately result in bond degradation at the resin-enamel interface, causing margin failure. Additionally, chemical interactions between fluoride and the composite may further destabilize the bond under long-term moisture exposure and cyclic aging. Moreover, barium glass fillers enhance the mechanical properties of composites but may affect bonding enamel. Fillers can stress the resin-filler interface if poorly bonded to the resin matrix. Cyclic loading, like chewing, may debond fillers, leading to failure at the composite-enamel interface and weakening overall strength adhesion. Moreover, the ORMOCER-based BFF group had large filler particles like glass ceramic fillers with a particle size of 1 µm) which can reduce the material's flexibility, making it more prone to stress concentration. While nanofillers improve surface smoothness and mechanical properties, their presence with larger fillers can reduce adaptability to the enamel surface during polymerization and cyclic loading. High filler loading typically enhances mechanical properties like strength and wear resistance. Still, exceeding a threshold (e.g., 70–80%) can increase the material's viscosity, which may negatively affect the composite's wetting ability on the enamel surface. If the resin fails to wet and adapt to the enamel surface adequately, it may not form a strong bond. Marginal gaps can form due to incomplete interface filling. In addition, the self-adhesive flowable incorporated with pre-polymerized fillers are typically added to improve the composite material's strength and wear resistance. However, their addition can affect the polymerization process and the adaptation to the enamel. If the polymerization of the pre-polymerized fillers is not perfectly coordinated with the surrounding matrix material, it could result in incomplete polymerization or weak spots within the resin matrix. These weak spots can lead to microcracks or debonding at the interface, contributing to the development of marginal gaps. Furthermore, the mechanical loading from chewing forces may exacerbate any pre-existing micro gaps and cause marginal failure. The combination of methacrylate monomers and fillers, particularly YbF3, can also enhance hydrolytic degradation at the enamel-resin interface after extended exposure to moisture, as observed in the oral cavity. Water absorption within the resin matrix produces softening and swelling, which may cause the bond to disintegrate. Cyclic aging, which simulates the thermal and mechanical stresses during mastication, can expedite this process, ultimately forming marginal gaps. Injectable flowable composites with barium and strontium fillers have different thermal expansion coefficients (CTE) than enamel. Thermomechanical cycling, which simulates the changes in temperature (from hot to cold) and the mechanical forces from chewing, can cause both the composite and the enamel to expand and contract at different rates. A CTE mismatch increases stress at the resin-enamel interface during thermal cycling, leading to marginal gaps or debonding. This issue worsens if the composite is overly filled with inorganic materials like barium glass strontium. De Albuquerque Jassé et al. [ 39 ] supported our results when evaluated the marginal adaptation before and after TMC of the BFF and conventional composite resin. A significant improvement in marginal adaptation was observed when BFF was used instead of traditional composite resin before and after TMC. The results of this study confirm that the BFF-RBCs tested have characteristics comparable to or superior to those of conventional resin regarding marginal adaptation. However, only long-term clinical trials can confirm the clinical success of the material. On the other hand, internal adaptation was preserved in all groups during the baseline examination except for the conventional flowable composite. We noted a gap in 90% of specimens in that group at baseline examination, likely due to the inconsistent hybrid layer formation. Low filler content, moisture sensitivity, and limited adhesive penetration into dentin affect traditional flowable composites. Dentin surfaces are treated less intensively, and improper conditioning, such as inadequate smear layer disruption, can prevent optimal bonding. The smear layer can block adhesive penetration and negatively impact bonding. Moreover, low-viscosity flowable composites have higher shrinkage rates due to reduced filler, risking separation from tooth structure and diminishing adhesion and marginal adaptation. The SFRC-BFF group's adhesive's inability to properly penetrate dentin due to a lack of demineralization results in weak bonding to dentin. Several factors can contribute to this, mostly its weak formulation, which is missing many strong adhesive compounds such as MDP and other methacrylates. Its weak acidity also results in poor adhesive penetration. In conjunction with the selective etching technique, this could result in more significant gaps in dentin after thermocycling aging and force loading on the bonding interface. ORMOCER-based BFF group showed internal gaps mainly due to Diethyl amino benzaldehyde (DEAB), used as an accelerator in adhesive polymerization, which can contribute to weakening the dentin bond over time, especially after cyclic aging. One of the key factors is oxidative degradation, as DEAB can undergo oxidation in the presence of oxygen, particularly when exposed to moisture. This oxidation can interfere with the polymerization process, leading to incomplete curing and reduced bond strength. Additionally, DEAB is water-soluble and may leach into the oral environment, causing hydrolytic degradation of the adhesive bond when exposed to saliva and moisture. This leaching can further compromise the bond's durability. Moreover, while DEAB aids in speeding up polymerization, it may not effectively contribute to the crosslinking of the polymer network, resulting in a weaker matrix that is more susceptible to thermal cycling and mechanical stress, ultimately leading to a weakened dentin bond. The BFF resin-based composite group contains hydroxyethyl methacrylate (HEMA), a hydrophilic monomer used in its adhesive system to enhance wetting and penetration into dentin. While HEMA improves initial bond strength, it can pose problems over time, especially under cyclic aging. Due to its hydrophilic nature, HEMA can cause water absorption into the adhesive layer. Over time, this moisture can lead to hydrolytic degradation of the resin-dentin interface and result in marginal leakage. HEMA’s softening effect on the resin can make the bond more vulnerable to mechanical stresses, such as thermal cycling and masticatory forces, weakening the bond over time. Alongside methacryloxyethyltrimellitic acid anhydride (4-META) monomer, which is also used in this adhesive, reacts with dentin to form chemical bonds. However, its sensitivity to moisture can also result in hydrolytic degradation under cyclic aging conditions. Self-adhering flowable showed internal gaps, possibly due to glycerol phosphate dimethacrylate (GPDM), a newer monomer in self-adhering composites. It enhances chemical bonding to dentin by reacting with hydroxyapatite and forming a stable bond to the substrate. However, after cyclic aging, GPDM may contribute to bond failure due to phosphate groups, which are susceptible to hydrolytic degradation when exposed to water over time. Moisture infiltration at the interface can cause the phosphate ester bonds to break down, leading to bond failure at the resin-dentin interface. Ultimately, internal adaptation revealed gaps exceeding 1 µm across all groups during the delayed evaluation. There were statistically significant differences in all groups except conventional flowable composite. Dentin is a porous tissue that contains water and organic materials. The resin matrix formed with Bis-EMA, UDMA, and dimethacrylate monomers is relatively hydrophobic; this moisture could impair the resin’s capacity to create a strong bond with dentin, which resulted in discontinuous internal margins before the aging process. Moreover, cyclic aging typically replicates temperature fluctuations (thermal cycling) and mechanical stress (chewing forces), which can lead to the expansion and contraction of the resin. Consequently, water absorption and demineralization can weaken the adhesive bond over time if the resin is hydrophobic and does not adhere effectively to dentin. Following cyclic aging, the bond may deteriorate further due to water infiltration at the interface. A study by Roggendorf et al. [ 37 ] Agreed with this study and found a larger gap formation internally after TMC. Also Tonetto et al. [ 12 ] Demonstrated that TMC obstructed the adaptation of dentin in every group compared to the initial conditions. In contrast Karabekiroglu et al. [ 6 ] observed that TMC doesn’t have an adverse effect on the dentin bond strength of most adhesive systems in Class V cavities. Also, El Naga et al. [ 40 ], the dentin integrity and BFFs were compared with conventional RBCs, which were used in both bulk filling techniques. The study's results revealed that the BFF restorations demonstrated a similar marginal gap formation to conventional universal RBCs under their research conditions. In the same way as our result, Elhawary et al. and Kamar et al. [ 41 ] A comparison of BFF and conventional flowable composites showed that the BFF composite has lower microleakage scores than the traditional flowable composite at both occlusal and gingival margins. This may be due to the established multifunctional methacrylate monomers, such as UDMA (urethane dimethacrylate) and EBADMA (ethoxyethyl methacrylate), which provide strong bonding to the tooth structure and resistance to stress, both of which are crucial for the longevity of restorations. In contrast to our study, Maj et al. [ 42 ]Conducted a comparative clinical study on the Self-adhering flowable composite and the traditional flowable composite. After six months, they found visible superficial damage to the margins of the filling in almost all cases of the Self-adhering flowable, while most cases with the traditional flowable composite exhibited better marginal integrity simultaneously. These differences may be due to the methodology used. Also, Baltacioğlu et al. [ 43 ] Compared to composite groups with low viscosities, the conventional flowable exhibited the lowest leakage, with no statistically significant difference from the BFF group. The current study's findings on thermomechanical affect all materials' marginal and internal adaptation with statistically significant differences among all groups. This contrasts with Casselli et al. [ 6 ] Evaluated the effect of TMC, margin location, and the adhesive system on the marginal adaptation of Class V cavities restored with micro-hybrid resin composite restorations. They concluded that the TMC did not alter the gap measurements and did not affect marginal adaptation. According to the results of this study the null hypothesis states that the type of restoration didn’t affect the marginal adaptation at baseline examination has been accepted. The type of restoration that did not affect the marginal adaptation during the delayed examination has been rejected. The type of restoration did not affect the internal adaptation during the baseline examination. On the other hand, the type of restoration did not impact the internal adaptation during the delayed examination, and this result has been rejected. The limitations of this study that restorative materials were assessed under laboratory conditions ( in vitro study). The dynamic environment of the oral cavity, influenced by factors like saliva flow, pH variations, and the patient's dietary habits, can yield results differing from those demonstrated in this study. Therefore, conducting further research through clinical trials is essential. Conclusions Different flowable composite restorative systems exhibited good marginal and internal adaptation in class V Cavities. The short fiber-reinforced flowable composite restorative system had better adaptation than other restorative systems, and thermomechanical Cyclic Loading exerted a negative effect on both marginal and internal adaptation Recommendations Different cavity designs and sizes are needed to test the effectiveness of the tested materials and confirm the current study's results. Further research is required, utilizing different thermomechanical cycling durations. More in vivo studies should be conducted to evaluate and compare the clinical performance of the tested materials. Using a 3D tool like micro-CT for measuring marginal and internal gaps can provide a superior assessment compared to 2D techniques. It evaluates not just the width and length of the gaps, but also their depth. Abbreviations BFF Bulk Fill flowable BF-RBCs bulk-fill resin-based composites CEJ cementoenamel junction CM Continuous margin DC degree of conversion DEAB Diethyl amino benzaldehyde EBADMA ethoxyethyl methacrylate Fig. Figure GPDM glycerol phosphate dimethacrylate HEMA hydroxyethyl methacrylate MDP Methacryloyloxydecyl dihydrogen phosphate MA marginal adaptation SEM Scanning electron microscope TMC Thermo-mechanical cycling UDMA urethane dimethacrylate µm micrometer Declarations Acknowledgements Special thanks to my dear husband, who supported me from the very beginning and through each obstacle in this work Funding No funding received. Clinical trial number: not applicable. Author information Authors and Affiliations 1: MSc, Conservative Dentistry Department, Faculty of Dentistry, Mansoura University, Mansoura, Egypt, Email: [email protected] https://orcid.org/0009-0001-5164-4792 2: Lecturer, Conservative Dentistry Department, Faculty of Dentistry, Mansoura University, Mansoura, Egypt, Email: [email protected] https://orcid.org/0000-0001-8120-5830 3: Professor, Conservative Dentistry Department, Faculty of Dentistry, Mansoura University, Mansoura, Egypt : Email: [email protected] https://orcid.org/0000-0002-7776-2308 Correspondence author: Sahar A Saleh, Department of Conservative Dentistry, Faculty of Dentistry, Mansoura University, (E-mail: [email protected] ). mobile: +201559571748 Author contributions All authors contributed to clinical procedures, writing, preparing figures, and reviewing the manuscript. Ethics declarations Ethics approval and consent to participate The current study obtained its approval from the Research Ethics Committee of Faculty of Dentistry, Mansoura University No. (A03012023CD).The procedures were carried out following the relevant laws and regulations. Written informed consent was obtained from all participants or their legal guardians for each donor tooth. Data availability The datasets generated and/or analyzed during the current study are not publicly available [as it is not published yet], but are available from the corresponding author on reasonable request. Consent for publication Not applicable. Competing interests The authors declare no competing interests. References Scepanovic D, Par M, Attin T, Tauböck TT. Marginal adaptation of flowable vs sonically activated or preheated resin composites in cervical lesions. J Adhes Dent. 2022;24:247–57. Van Ende A, De Munck J, Lise DP, Van Meerbeek B. Bulk-Fill Composites: A Review of the Current Literature. J Adhes Dent. 2017;19:95–110. Casselli DSM, Faria-E-Silva AL, Casselli H, Martins LRM. Marginal adaptation of class V composite restorations submitted to thermal and mechanical cycling. J Appl Oral Sci. 2013;21:68–73. Rengo C, Goracci C, Ametrano G, Chieffi N, Spagnuolo G, Rengo S, et al. Marginal leakage of class V composite restorations assessed using microcomputed tomography and scanning electron microscope. Oper Dent. 2015;40:440–8. Versluis A, Tantbirojn D, Lee MS, Tu LS, Delong R. Can hygroscopic expansion compensate polymerization shrinkage? part I. deformation of restored teeth. Dent Mater. 2011;27:126–33. Casselli DSM, Faria-E-Silva AL, Casselli H, Martins LRM. Marginal adaptation of class V composite restorations submitted to thermal and mechanical cycling. J Appl Oral Sci. 2013;21:68–73. Gayatri C, Rambabu T, Sajjan G, Battina P, Priyadarshini MS, Sowjanya BL. Evaluation of Marginal Adaptation of a Self-Adhering Flowable Composite Resin Liner: A Scanning Electron Microscopic Study. Contemp Clin Dent. 2018;9:240–5. Ismail HS, Ali AI, Mehesen RE, Juloski J, Garcia-Godoy F, Mahmoud SH. Deep proximal margin rebuilding with direct esthetic restorations: a systematic review of marginal adaptation and bond strength. Restor Dent Endod. 2022;47:1–18. Al-Atyaa ZT, Majeed MA. Comparative evaluation of the marginal and internal fitness of monolithic cad/cam zirconia crowns fabricated from different conventional impression techniques and digital impression using silicone replica technique : an in vitro study. Biomed Pharmacol J. 2018;11:477–90. Mourouzis P, Koulaouzidou EA, Palaghias G, Helvatjoglu-Antoniades M. Color match of resin composites to intact tooth structure. J Appl Biomater Funct Mater. 2015;13:259–65. Sadeghi M. An in vitro microleakage study of class V cavities restored with a new self-adhesive flowable composite resin versus different flowable materials. Dent Res J (Isfahan). 2012;9:460–5. Tonetto MR, Bandéca MC, De Oliveira Barud HG, Pinto SCS, Lima DM, Borges AH, et al. Influence of artificial aging in marginal adaptation of mixed class V cavities. J Contemp Dent Pract. 2013;14:316–9. Ismail HS, Ali AI, Mehesen R El, Garcia-Godoy F, Mahmoud SH. In vitro marginal and internal adaptation of four different base materials used to elevate proximal dentin gingival margins. J Clin Exp Dent. 2022;14:550–9. Park KJ, Pfeffer M, Näke T, Schneider H, Ziebolz D, Haak R. Evaluation of low-viscosity bulk-fill composites regarding marginal and internal adaptation. Odontology. 2021;109:139–48. Aggarwal V, Singla M, Yadav S, Yadav H. Effect of flowable composite liner and glass ionomer liner on class II gingival marginal adaptation of direct composite restorations with different bonding strategies. J Dent. 2014;42:619–25. Jati AS, Furquim LZ, Consolaro A. Gingival recession: its causes and types, and the importance of orthodontic treatment. Dental Press J Orthod. 2016;21:1–18. Bajabaa S, Balbaid S, Taleb M, Islam L, Elharazeen S, Alagha E. Microleakage evaluation in class V cavities restored with five different resin composites: in vitro dye leakage study. Clin Cosmet Investig Dent. 2021;13:1–15. Torres CRG, Mailart MC, Moecke SE, Matuda AGN, Veloso SM, da Silva Ávila DM, et al. Flowable bulk-fill versus layering restorative material on class II restorations: a randomized clinical trial. J Dent. 2024;148:1–9. Sooraparaju SG, Kanumuru PK, Nujella SK, Konda KR, Reddy KBK, Penigalapati S. A comparative evaluation of microleakage in class v composite restorations. Int J Dent. 2014;2014:1–4. Shadman N, Pezeshki B, Rostami S. Marginal sealing of bulk fill versus conventional composites in class II composite restorations: an in vitro study. Front Dent. 2020;17:1–6. Freitas D, Cia L, Lima D, Rodolfo X, De Azeve LJ, Alonso R, et al. Bonding performance and mechanical properties of flowable bulk-fill and traditional composites in high c-factor cavity models. J Conserv Dent. 2014;8:1–36. Wahab FK, Shaini FJ, Morgano SM. The effect of thermocycling on microleakage of several commercially available composite class v restorations in vitro. J Prosthet Dent. 2003;90:168–74. Ispas A, Moldovan M, Cuc S, Prodan D, Bacali C, Petean I, et al. SEM evaluation of marginal adaptation e-max crowns manufactured by printing-pressed and milling. Diagnostics. 2023;13:1–14. Trifkovic B. Application of replica technique and SEM in accuracy measurement of ceramic crowns. Meas Sci Rev. 2012;4:1–14. Costa AT, Konrath F, Dedavid B, Weber JBB, de Oliveira MG. Marginal adaptation of root-end filling materials: an in vitro study with teeth and replicas. J Contemp Dent Pract. 2009;10:1–12. Gunjal S, Nagesh L, Raju HG. Comparative evaluation of marginal integrity of glass ionomer and resin based fissure sealants using invasive and non-invasive techniques: an in vitro study. Indian J Dent Res. 2012;23:320–5. Gloria Kang GJ, Ewing-Nelson SR, Mackey L, Schlitt JT, Marathe A, Abbas KM SS. Cyclic mechanical loading promotes bacterial penetration along composite restoration marginal gaps. Physiol Behav. 2018;176:139–48. von Fraunhofer JA, Adachi EI, Barnes DM, Romberg E. The effect of tooth preparation on microleakage behavior. Oper Dent. 2000;25:526–33. Soriano-Valero S, Román-Rodriguez JL, Agustín-Panadero R, Bellot-Arcís C, Fons-Font A, Fernández-Estevan L. Systematic review of chewing simulators: reality and reproducibility of in vitro studies. J Clin Exp Dent. 2020;12:1189–95. Morresi AL, D’Amario M, Capogreco M, Gatto R, Marzo G, D’Arcangelo C, et al. Thermal cycling for restorative materials: does a standardized protocol exist in laboratory testing? a literature review. J Mech Behav Biomed Mater. 2014;29:295–08. Angwarawong T, Reeponmaha T, Angwaravong O. Influence of thermomechanical aging on marginal gap of CAD-CAM and conventional interim restorations. J Prosthet Dent. 2020;124:566–77. Jordehi A, Shahabi M, Akbari A. Comparison of self-adhering flowable composite microleakage with several types of bonding agent in class V cavity restoration. Dent Res J (Isfahan). 2019;16:257–63. Agarwal RS, Hiremath H, Agarwal J, Garg A. Evaluation of cervical marginal and internal adaptation using newer bulk fill composites: an in vitro study. J Conserv Dent. 2015;18:56–61. Abdelwahed AG, Essam S, Abdelaziz MM. Marginal adaptation and depth of cure of flowable versus packable bulk-fill restorative materials: an in vitro study. J Med Sci. 2022;10:47–56. Magne P, Carvalho MA, Milani T. Shrinkage-induced cuspal deformation and strength of three different short fiber-reinforced composite resins. J Esthet Restor Dent. 2023;35:56–63. Harp YS, Montaser MA, Zaghloul NM. Flowable fiber-reinforced versus flowable bulk-fill resin composites: degree of conversion and microtensile bond strength to dentin in high c-factor cavities. J Esthet Restor Dent. 2022;34:699–06. Roggendorf MJ, Krämer N, Appelt A, Naumann M, Frankenberger R. Marginal quality of flowable 4-mm base vs. conventionally layered resin composite. J Dent. 2011;39:643–7. ElAziz RHA, ElAziz SAA, ElAziz PMA, Frater M, Vallittu PK, Lassila L, et al. Clinical evaluation of posterior flowable short fiber-reinforced composite restorations without proximal surface coverage. Odontology. 2024;4:1–10. Jassé FF de A, Alencar C de M, Zaniboni JF, Silva AM, Campos EA de. Assessment of marginal adaptation before and after thermo-mechanical loading and volumetric shrinkage: bulk fill versus conventional composite. Int J Odontostomatol. 2020;14:60–6. El Naga MA, Qian F, Denehy GE, Quock RL, Armstrong SR. Marginal adaptation and internal indentation resistance of a Class II bulk-fill resin-based composite. Am J Dent. 2020;33:145–50. Elhawary AA, Elkady AS, Kamar AA. Comparison of degree of conversion and microleakage in bulkfill flowable composite and conventional flowable composite(an in vitro study). Alexandria Dent J. 2016;41:336–43. Maj A, Trzcionka A, Twardawa H, Tanasiewicz M. A comparative clinical study of the self-adhering flowable composite resin vertise flow and the traditional flowable composite resin premise flowable. Coatings. 2020;10:1–16. Baltacioğlu İH, Demirel G, Öztürk B, Aydin F, Orhan K. Marginal adaptation of bulk-fill resin composites with different viscosities in class II restorations: a micro-ct evaluation. BMC Oral Health. 2024;24:1–7. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 09 Dec, 2025 Read the published version in BMC Oral Health → Version 1 posted Editorial decision: Revision requested 19 Sep, 2025 Reviews received at journal 15 Sep, 2025 Reviewers agreed at journal 07 Sep, 2025 Reviewers agreed at journal 04 Sep, 2025 Reviews received at journal 03 Sep, 2025 Reviewers agreed at journal 02 Sep, 2025 Reviewers invited by journal 02 Sep, 2025 Editor assigned by journal 30 Aug, 2025 Submission checks completed at journal 30 Aug, 2025 First submitted to journal 24 Aug, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7446404","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":511459875,"identity":"75a44fb5-979b-4a19-a3ee-bc2b02194d8c","order_by":0,"name":"Sahar A. Saleh","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3UlEQVRIiWNgGAWjYFACHhBhwWDA3gCkDSyI1iLBYMBzAKRFghQtEgkQBkEg3372AOOPGgk5c8nnVzf8KJBg4G/vTsCrxeBMXgIzzzEJY8vZOWU3e4AOkzhzdgN+LQw5BswMbBKJG27npN3gMQC5MBe/Fvn+NwaMP/5J1G+4eSbt5h9itDDcyDFg4G2TSDC4wX7sNlG2GNx4Y3CYt0/CcMOZHLbbMgYSPAT9It+fY/jwxzcbeYPjx5/dfPPHRo6/vZeAw4DgAITiMQCTBJUjAfYHpKgeBaNgFIyCEQQAWmFFDcVu+tgAAAAASUVORK5CYII=","orcid":"","institution":"Mansoura University","correspondingAuthor":true,"prefix":"","firstName":"Sahar","middleName":"A.","lastName":"Saleh","suffix":""},{"id":511459876,"identity":"923963d7-c4f6-4bd1-9b34-82b53e5d4b1f","order_by":1,"name":"Maha M. Ebaya","email":"","orcid":"","institution":"Mansoura University","correspondingAuthor":false,"prefix":"","firstName":"Maha","middleName":"M.","lastName":"Ebaya","suffix":""},{"id":511459877,"identity":"3409c85b-39a4-4bb8-adef-179e26d48e9e","order_by":2,"name":"Ashraf I. Ali","email":"","orcid":"","institution":"Mansoura University","correspondingAuthor":false,"prefix":"","firstName":"Ashraf","middleName":"I.","lastName":"Ali","suffix":""}],"badges":[],"createdAt":"2025-08-24 13:23:16","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7446404/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7446404/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12903-025-07324-0","type":"published","date":"2025-12-09T15:58:25+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":90851917,"identity":"5947ba61-656c-412d-be52-a41fd6add017","added_by":"auto","created_at":"2025-09-09 03:28:03","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":155822,"visible":true,"origin":"","legend":"\u003cp\u003eShowing (A) standardized using a stainless steel matrix band ; (B) cavity measurement mesiodistally (C) depth of prepared cavity.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7446404/v1/b03719c8d1ffb8eee4575efe.png"},{"id":90851923,"identity":"956b4dae-9407-4a0a-90ab-609a30f33b79","added_by":"auto","created_at":"2025-09-09 03:28:03","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":68785,"visible":true,"origin":"","legend":"\u003cp\u003eDiagram that illustrates the experimental design and grouping\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7446404/v1/23d4bde9ca78ccc4142b8e35.png"},{"id":90852311,"identity":"341a5724-c486-4eca-bdce-754533f494b7","added_by":"auto","created_at":"2025-09-09 03:36:03","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":428125,"visible":true,"origin":"","legend":"\u003cp\u003eSEM photomicrographs showing marginal adaptation at the 200X magnification the left picture N-TMC examination; right after TMCال,\u003cstrong\u003eA , B \u003c/strong\u003ethe ORMOCER-based BFF ;\u003cstrong\u003eC,D\u003c/strong\u003e: fiber-reinforceder flowable ; \u003cstrong\u003eE,F\u003c/strong\u003e:bulk-fill flowable ; \u003cstrong\u003eG,H : \u003c/strong\u003eself-adhering flowable ;\u003cstrong\u003eI,J\u003c/strong\u003e:conventional flowable\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7446404/v1/3f0e36bd577403abc5fb1280.png"},{"id":90851920,"identity":"22ecea77-ece2-4326-9714-ecb128d50ad1","added_by":"auto","created_at":"2025-09-09 03:28:03","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":602688,"visible":true,"origin":"","legend":"\u003cp\u003eSEM photomicrographs showing internal adaptation at the 200X magnification the left side at N-TMC examination; right side \u0026nbsp;after TMC ,\u003cstrong\u003eA , B\u003c/strong\u003e the ORMOCER-based BFF;\u003cstrong\u003eC,D\u003c/strong\u003e: short fiber-reinforced \u0026nbsp;F ; \u003cstrong\u003eE,F\u003c/strong\u003e: BFF ; \u003cstrong\u003eG,H\u003c/strong\u003e : self-adhering flowable ;\u003cstrong\u003eI,J\u003c/strong\u003e: injectable flowable\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7446404/v1/d6745064aa5459764f682f18.png"},{"id":98245662,"identity":"1e231d5c-c595-4f8f-9bed-46024b28864c","added_by":"auto","created_at":"2025-12-15 16:18:15","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2158904,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7446404/v1/741c6947-9a5c-432d-817a-11240be57608.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eMarginal and Internal Adaptation of Different Flowable Composite Restorations in Class V Cavities after Thermomechanical Cyclic Loading: In vitro study\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eRestoring class V cavities is a common clinical dental procedure, yet it can be technically demanding due to its proximity to the gingiva and challenges with moisture control. This can result in inadequate bonding to the cavity walls and gaps between the restoration material and the tooth. Additionally, the shrinkage forces of resin-based composites can cause interfacial microleakage, potentially leading to marginal discoloration, secondary caries, or loss of retention.[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eThe variations in filler content of resin composites influence whether the material is sculptable or flowable. Flowable composites have a lower filler load and viscosity, which reportedly enhances wettability and adhesion to cavity surfaces and walls. Moreover, these composites feature a lower elastic modulus, leading to increased flexibility and better resistance to flexural stress at the tooth cervix.[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eHowever, in the past years, bulk-fill resin-based composites (BF-RBCs) have been introduced to the dental market to address challenges associated with the incremental technique for posterior teeth. Initially, the term bulk-fill referred to resin composites that permitted 4\u0026ndash;5 mm increments, suitable for full-body and base bulk-fill techniques.[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eAdditionally, dental restoration adaptation and thermomechanical cycling are crucial for restorative materials' long-term success, impacting durability and function. However, thermomechanical cycling, subjecting materials to temperature changes and mechanical stress, can affect their performance. These cycles cause thermal expansion and contraction, potentially creating gaps between the restoration and tooth structure and leading to wear and fatigue in the material.[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] This degradation compromises the seal, causes discomfort, or leads to the failure of restoration.[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] Clinical evaluations of restorations present challenges due to ethical considerations and are costly and time-intensive.[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e] \u003cem\u003eIn vitro\u003c/em\u003e studies that simulate oral conditions have been conducted to estimate restoration longevity\u003c/p\u003e\u003cp\u003eThe marginal seal of composite restorations represents an increasing concern. Over the years, \u003cem\u003ein vitro\u003c/em\u003e evaluations of the performance of resin adhesives revealed that microleakage and gap formation, mainly at the dentin-composite interface, did not improve at the same rate as did bond strength values Independent of the bonding capacity of an adhesive system, it seems that adhesive restorations are far from assuring a perfect marginal seal, with degradation in time occurring regardless of the product used.[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] Marginal and internal integrity results from several parameters related to the forces created by curing contraction, as bond strength alone could not be correlated to the adaptation.[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] Finally, according to the author's knowledge, there are few studies concerning the marginal and internal adaptation of bulkfill-flowable composite restorative systems after thermomechanical cycling have been published, and more data are still required. Therefore, evaluating the marginal and internal adaptation of different flowable composite restorative systems in class V cavities will be valuable after thermomechanical cyclic loading (TMC). This study was designed to test the null hypothesis that there would be no significant difference in the marginal and internal adaptation of different flowable composite restorative systems in class V cavities\u003c/p\u003e"},{"header":"Materials","content":"\u003cp\u003eThis study was done after obtaining ethical approval from the faculty of dentistry's ethical committee under No. (A03012023CD). The sample size calculation was based on a previous study on marginal adaptation.[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] Using the G power program version 3.1.9.7 to calculate sample size based on an effect size of 1.7, a 2-tailed test, α error\u0026thinsp;=\u0026thinsp;0.05, and power\u0026thinsp;=\u0026thinsp;85.0%, the total estimated sample size is 7 in each subgroup, which was increased to 10 for a more valuable result.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eSpecimen selection and preparation:\u003c/h2\u003e\u003cp\u003eOne hundred freshly extracted human premolars from the oral surgery clinic, Faculty of Dentistry, Mansoura University, were selected for this study. They were extracted for orthodontic reasons. The teeth were carefully inspected using light to ensure they were free from caries, restorations, cracks, or other defects. Soft tissue remnants were removed using a hand scaler (Zeffiro; Lascod, Florence, Italy). Teeth were stored in 1% chloramine-T for 48 hours and in distilled water that was changed weekly until usage.\u003c/p\u003e\u003cp\u003eClass V cavity with measurements 3 mm mesiodistal (width), 3 mm occluso-gingival (height), and 2 mm axial (depth) was prepared on the facial surface of each tooth, with surface angles kept at 90 degrees without bevel designs. [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The outline of the cavities was standardized using a stainless steel matrix band, \u003cb\u003eFigure (1)\u003c/b\u003e and preparation was performed with a straight-fissure diamond bur no. (SF-41 MANI Ltd., Utsunomiya, Japan) with a water-cooled high-speed handpiece (30,000\u0026ndash;50,000 rpm, NSK, Shinagawa City, Japan). Bur was replaced after every five preparations.[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAll restoration steps were done according to the manufacturer's instructions, and then specimens were randomly divided into five groups based on restorative materials (n\u0026thinsp;=\u0026thinsp;20) using an online randomizing program ( \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e\u003ca href=\"http://www.randomizer.com\" target=\"_blank\"\u003ewww.randomizer.com\u003c/a\u003e\u003c/span\u003e\u003cspan address=\"http://www.randomizer.com\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e ). Group I was restored with NovaPro Flow (Nanova, Columbia, MO, USA), Group II with Vertise Flow (Kerr, USA), Group III with Admira Fusion X-base (Voco GmbH, Cuxhaven, Germany), Group IV with Venus Bulk Flow One (Kulzer GmbH, Germany), and Group V with G-\u0026aelig;nial Universal Injectable (GC Co., Tokyo, Japan). Groups were further divided into two subgroups (n\u0026thinsp;=\u0026thinsp;10) based on thermomechanical cycling: Subgroup I was examined at non-thermomechanical cycling (N-TMC), and Subgroup II was examined after thermomechanical cycling (TMC) with 5,000 cycles at 5\u0026deg;\u0026plusmn;1℃ and 55\u0026deg;\u0026plusmn;1℃, with dwell times of 60 seconds and transfer times of 15 seconds. Using the thermocycling machine (SD Mechatronic thermocycler) and for mechanical stimulation, a total of 100,000 cycles of an occlusal load at 100 N and 4 Hz were applied (SD Mechatronic CS-4, Germany), which represents 6 months in the oral environment.[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] \u003cb\u003eFigure.(2)\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eEvaluation Marginal Adaptation\u003c/h3\u003e\n\u003cp\u003eAll teeth are mounted on aluminum stubs and then coated with gold using a sputter coater (Sputter Coating Evaporator, SPI Supply, USA). They were examined under a Scanning electronic microscope (JSM-6510LV, JEOL Ltd., Tokyo, Japan) at magnification x25-200.[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] All SEM examinations and measurements were conducted by a single operator experienced in quantitative margin analysis and unaware of the restorative materials. Detectable gaps were checked and calculated at \u0026times;200, and images were analyzed using image analysis software (SEM Control User Interface Ver 3.10, JEOL Ltd.). The interface between each material and the substrate was also quantitatively analysed. The marginal adaptation was scored 0 if the interface between the restoration and tooth was continuous and exhibited less than 1 \u0026micro;m gap and scored 1 if the interface had gaps more than 1 \u0026micro;m wide. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/p\u003e\n\u003ch3\u003eInternal Adaptation Evaluation\u003c/h3\u003e\n\u003cp\u003eTeeth were sectioned longitudinally with a slow-speed diamond saw (Isomet 4000-Buehler, Lake Bluff, IL, USA) with water coolant in a buccolingual direction. Each specimen received 1 cut to produce 2 slices per specimen. Then, it was mounted on aluminum stubs and coated with gold using a sputter coater (Sputter Coating Evaporator, SPI Supply, USA). The inner side of each slice's material/ dentin interface was evaluated for internal adaptation using SEM using the same technique and parameters mentioned in the marginal adaptation part. The inner side of the restorative material/dentin interface was evaluated for internal adaptation using SEM using the same technique and parameters mentioned in marginal adaptation.[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/p\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003eStatistical analysis:\u003c/h2\u003e\u003cp\u003eData analysis was performed using SPSS software, version 26 (Chicago: SPSS Inc.). Qualitative data were described using numbers and percentages. The significance of the obtained results was judged at a P.\u0026le; 0.05. The Monte Carlo test was used to compare between studied groups, and the MC Nemar test was used to compare N-TMC and TMC results.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eMarginal Adaptation\u003c/h2\u003e\u003cp\u003eExamining marginal integrity with SEM in N-TMC or delayed subgroups for comparison among different groups, we observe gaps with all materials of varying sizes in the following order: short fiber-reinforced flowable with very small gaps, followed by resin-based bulk-fill flowable, ORMOCER-based BFF, self-adhering flowable and lastly, conventional flowable composite. These observations were reported as 100% across all groups in the baseline state, with no statistically significant differences (p\u0026thinsp;=\u0026thinsp;1) with a gap\u0026thinsp;\u0026lt;\u0026thinsp;1 \u0026micro;m. Furthermore, no statistically significant difference exists between groups in the delayed state, with p\u0026thinsp;=\u0026thinsp;0.08 and gaps\u0026thinsp;\u0026gt;\u0026thinsp;1 \u0026micro;m.\u003c/p\u003e\u003cp\u003eIn other ways, these gaps are statically represented when comparing the materials in the same groups, both at N-TMC and in TMC state. A clear and significant difference exists across all groups, indicating an increase of more than 1 \u0026micro;m gaps. All groups show 100%, except for the short fiber-reinforced flowable group, which has 80% with a gap greater than 1 \u0026micro;m and 20% with an intact margin of less than 1 \u0026micro;m, and this supported the SEM finding. As shown in \u003cb\u003eTable\u0026nbsp;(1)\u003c/b\u003e and \u003cb\u003eFigure (3).\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eComparison of the marginal adaptation between studied groups between N-TMC versus TMC.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMarginal margin\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eORMOCER-based BFF N\u0026thinsp;=\u0026thinsp;10 (%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eShort fiber reinforced F N\u0026thinsp;=\u0026thinsp;10(%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eBFF N\u0026thinsp;=\u0026thinsp;10(%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eSelf-adhering flowable N\u0026thinsp;=\u0026thinsp;10(%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eInjectable flowable composite N\u0026thinsp;=\u0026thinsp;10(%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eTest of significance\u003c/p\u003e\u003cp\u003e(Monte Carlo test)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eN-TMC\u003c/p\u003e\u003cp\u003e\u0026lt;\u0026thinsp;1 \u0026micro;m\u003c/p\u003e\u003cp\u003e\u0026gt;\u0026thinsp;1 \u0026micro;m\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eP\u0026thinsp;=\u0026thinsp;1.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTMC\u003c/p\u003e\u003cp\u003e\u0026lt;\u0026thinsp;1 \u0026micro;m\u003c/p\u003e\u003cp\u003e\u0026gt;\u0026thinsp;1 \u0026micro;m\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2(20)\u003c/p\u003e\u003cp\u003e8(80)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0\u003c/p\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eMc\u0026thinsp;=\u0026thinsp;8.33\u003c/p\u003e\u003cp\u003eP\u0026thinsp;=\u0026thinsp;0.08\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMC Nemar test\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eP\u0026thinsp;\u0026lt;\u0026thinsp;0.001*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eP\u0026thinsp;=\u0026thinsp;0007*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026lt;\u0026thinsp;0.001*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eP\u0026thinsp;\u0026lt;\u0026thinsp;0.001*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eP\u0026thinsp;\u0026lt;\u0026thinsp;0.001*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"7\"\u003e*Statistically significant\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eInternal Adaptation\u003c/h3\u003e\n\u003cp\u003eExamining internal adaptation integrity with SEM at N-TMC or TMC subgroups for comparison among different groups, we observe gaps with all materials of varying sizes in the following order: short fiber-reinforced flowable with very small gaps, followed by bulk-fill flowable, ORMOCER-based BFF, self-adhering flowable and lastly, injectable flowable composite. These observations were reported as 100% in all groups except injectable flowable composite 10% in the N-TMC examination, with statistically significant differences (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001*) with a gap of less than 1 \u0026micro;m. Furthermore, no statistically significant difference exists between groups in the TMC state, with P\u0026thinsp;=\u0026thinsp;1.0 and more than 1 \u0026micro;m gaps.\u003c/p\u003e\u003cp\u003eIn other words, when comparing the material in the same group N-TMC and the TMC examination, there is a clear significant difference across the first four groups with P\u0026thinsp;\u0026lt;\u0026thinsp;0.001*, indicating a gap increase of more than 1 \u0026micro;m. At the same time, with injectable flowable composite, there is no statistically significant difference with P\u0026thinsp;=\u0026thinsp;1.0, and these support the SEM finding. As shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and \u003cb\u003eFigure.(4)\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eComparison of internal adaptation between studied groups and between N- TMC versus TMC\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"8\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eInternal adaptation\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eORMOCER-based BFF N\u0026thinsp;=\u0026thinsp;10 (%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003eShort fiber reinforced F N\u0026thinsp;=\u0026thinsp;10(%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eBFF N\u0026thinsp;=\u0026thinsp;10(%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eSelf-adhering flowable N\u0026thinsp;=\u0026thinsp;10(%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eInjectable flowable composite N\u0026thinsp;=\u0026thinsp;10(%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eTest of significance\u003c/p\u003e\u003cp\u003e(Monte Carlo test )\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eN-TMC\u003c/p\u003e\u003cp\u003e\u0026lt;\u0026thinsp;1 \u0026micro;m\u003c/p\u003e\u003cp\u003e\u0026gt;\u0026thinsp;1 \u0026micro;m\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e1(10)\u003c/p\u003e\u003cp\u003e9(90)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eMc\u0026thinsp;=\u0026thinsp;43.90\u003c/p\u003e\u003cp\u003eP\u0026thinsp;\u0026lt;\u0026thinsp;0.001*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTMC\u003c/p\u003e\u003cp\u003e\u0026lt;\u0026thinsp;1 \u0026micro;m\u003c/p\u003e\u003cp\u003e\u0026gt;\u0026thinsp;1 \u0026micro;m\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0\u003c/p\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0\u003c/p\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0\u003c/p\u003e\u003cp\u003e10(100)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eP\u0026thinsp;=\u0026thinsp;1.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMC Nemar test\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eP\u0026thinsp;\u0026lt;\u0026thinsp;0.001*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eP\u0026thinsp;\u0026lt;\u0026thinsp;0.001*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003eP\u0026thinsp;\u0026lt;\u0026thinsp;0.001*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eP\u0026thinsp;\u0026lt;\u0026thinsp;0.001*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eP\u0026thinsp;=\u0026thinsp;1.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"8\"\u003e*Statistically significant\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eClass V cavities are characterized by their location on the gingival third of the teeth. This poses unique challenges for restorative dentistry, including moisture control, adhesion to enamel, and the potential for high mechanical and thermal stresses due to their proximity to the gingival tissues.[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] Restoration success in a class V cavity depends mainly on the material's ability to adapt marginally and internally to the cavity walls, ensuring a durable seal that prevents microleakage and secondary caries.[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] Restorative materials must also withstand occlusal and lateral forces while maintaining biocompatibility and esthetics in this visible dentition area. Advances in restorative materials, particularly bulk-fill flowable composites, have shown promise in overcoming these challenges by improving ease of application, adaptation properties, and mechanical performance.[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eSelecting an appropriate resin composite and adhesive system in the class V cavity is crucial for restoration success. The main challenge in restoring this type of cavities is ensuring proper marginal adaptation.[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] Polymerization shrinkage (PS) during resin curing induces internal stress at the tooth-restoration interface, weakening the bond in flexible, porous dentin. This can cause marginal gaps or microleakage, allowing fluids or bacteria to enter, leading to inflammation, secondary caries, or pulp issues. Shrinkage-induced stress can weaken the adhesive and tooth bond, especially when the dentin is too wet.[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eBulk-fill flowable materials in class V cavities improve clinical outcomes by reducing postoperative sensitivity and extending restoration longevity. BFF materials address challenges in class V restorations with lower PS, minimizing marginal gaps and reducing the risk of fractures or adhesive failure. Their flowable properties allow close conformation to cavity wall margins.[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] This enhances internal adaptation and reduces the need for multiple layers, minimizing voids that could weaken the restoration. BFF materials streamline the process, lowering error rates and increasing efficiency. Advanced BFF matches the mechanical properties of traditional composites, making them suitable for stress-bearing areas of class V cavities.[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eThis study used a box-shaped preparation to standardize experimental groups. The consistent cavity configuration minimized variations in preparation techniques, ensuring restorations were evaluated under similar conditions. This approach facilitated reliable comparisons by controlling for differences in cavity geometry that could affect restorative procedure outcomes. [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. In Class V cavities, achieving ideal adaptation is particularly challenging due to the higher C-factor inherent in these designs.\u003c/p\u003e\u003cp\u003eScanning Electron Microscopy (SEM) is a vital tool for assessing the marginal adaptation of dental materials. It generates high-resolution images of the tooth-restoration interface, allowing detailed examination of gaps and defects by evaluating the fit, surface morphology, and bonding quality. This helps to identify issues that may affect longevity.[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] Direct sample analysis using SEM is preferred over replicas, as it avoids replication artifacts and ensures an accurate interface representation.[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eThis method provides relevant data by examining the materials without alterations from the replica-making process. Overall, SEM accurately evaluates the restoration\u0026rsquo;s performance, including potential gaps and bacterial or saliva penetration risk.[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] Gaps of less than 1 \u0026micro;m are generally associated with better marginal and internal adaptation.[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] This reduces bacterial penetration and longer-lasting restorations. However, even gaps at this small scale should be minimized to prevent long-term risks. More significant gaps (greater than 1 \u0026micro;m) significantly increase the potential for bacterial penetration, leading to secondary caries, marginal breakdown, and restoration failure. Therefore, achieving precise marginal and internal adaptation during restorative procedures is essential for the durability and success of dental restorations.[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eGloria Kang GJ \u003cem\u003eet al.\u003c/em\u003e [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] Investigated the effect of bacterial penetration into gaps. It was shown that smaller gap samples had less bacterial penetration. When more significant gaps exist, bacteria easily penetrate to the full depth of the gap, regardless of loading conditions, increasing the incidence of secondary caries formation.\u003c/p\u003e\u003cp\u003eThis study executed 5,000 thermal cycles to evaluate the direct correlation with the increase in marginal gaps at the dental restoration interface.[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] After that, specimens underwent 100,000 cycles of 100 N occlusal load at 4 Hz.[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] This equates to six months of clinical functionality, assuming that these cycles happen 10 to 25 times a day, as many studies suggest.[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] The mechanical simulator provides insights into a material\u0026rsquo;s performance during prolonged use and how dental restorations react to complex forces in the oral cavity by simulating stress distribution, fatigue, wear, and crack propagation. The simulator considers the physiological traits of human chewing and the direction of jaw movements.[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] Thermal cycling affects the bonding agent's or adhesive's properties, while mechanical cycling, such as forces from chewing, may stress the bond interface.[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eThis study showed that all groups tested at baseline achieved 100% marginal adaptation integrity without significant differences between groups.\u003c/p\u003e\u003cp\u003eShort fiber-reinforced flowable composites (SFRC-F) showed the best results among groups, which may be due to the content of hydroxyapatite fibers, which are particularly beneficial in enhancing bioactivity and mineralization. Hydroxyapatite, a primary component of tooth enamel, can chemically interact with the enamel surface, providing stronger interfacial adhesion due to its similar composition. The presence of hydroxyapatite fibers helps improve the chemical bonding between the composite and enamel, providing excellent initial bond strength.\u003c/p\u003e\u003cp\u003eIn the BFF resin-based composite group, the matrix comprises multifunctional methacrylate monomers, UDMA, EBADMA, and Bis-EMA. These monomers can achieve a good bond with enamel through the chemical interaction of the monomers with enamel's hydroxyapatite. Also, its flowability allows the composite to fill micro-irregularities in the enamel and cavity walls, ensuring micromechanical retention. This helps the material bond more effectively with the tooth surface by getting into tiny pores or grooves and creating a strong mechanical lock.\u003c/p\u003e\u003cp\u003eORMOCER-based BFF inorganic component is chemically incorporated into the organic polymer, meaning that the material is inherently a hybrid and the two phases (organic and inorganic) are more interconnected at a molecular level, leading to enhanced properties such as reduced shrinkage and more substantial marginal adaptation. The organic resin portion allows the material to bond to the enamel through functional monomers with acid-functional groups such as Bis-EMA, aliphatic dimethacrylate, and UDMA., which can interact with enamel. These monomers can bond chemically to the enamel's mineral content, creating a chemical adhesive bond between the ORMOCER composite and the tooth structure. At the same time, the silicon oxide nanofillers and glass ceramics filler give the material additional durability, strength, and wear resistance, which is crucial for achieving a tight marginal seal. These materials are designed to form substantial, well-sealed restoration with excellent marginal adaptation, reducing the risk of bacterial infiltration and ensuring the long-term success of the restoration.\u003c/p\u003e\u003cp\u003eFurthermore, Self-adhesive flowable composites are designed with chemicals that allow them to bond to enamel surfaces chemically. These materials contain functional monomers (like carboxyl and phosphoric acid groups) capable of interacting with the mineral components in enamel, even without the need for etching. These monomers help form a bond with the tooth structure by chemically interacting with hydroxyapatite, the main component of enamel.[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eInjectable flowable material had good marginal adaptation integrity, possibly due to its high flow, meaning low viscosity. This allows it to adapt to enamel surfaces and fill intricate cavities easily. It also penetrates micro-irregularities and creates close contact with the enamel while maintaining a smooth surface.\u003c/p\u003e\u003cp\u003eAlso, Agarwal \u003cem\u003eet al.\u003c/em\u003e[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e] Finds that all tested materials showed acceptable marginal adaptation in enamel before TMC. Unfortunately, this level of adaptation declined after TMC. In addition, Tonetto \u003cem\u003eet al.\u003c/em\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] Demonstrated that TMC obstructed the marginal adaptation of enamel in every group compared to the initial conditions, and both agreed with our findings. Furthermore, this aligns with the results of Abdelwahed \u003cem\u003eet al.\u003c/em\u003e[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] Who stated that no group, regardless of the restorative materials utilized, achieved 100% continuous margins.\u003c/p\u003e\u003cp\u003eAccording to the SEM assessment after TMC group, the SFRC-BFF group showed less discontinuous margin to the enamel, followed by the BFF group, then the ORMOCER-based BFF group, then self-adhesive flowable, and finally injectable flowable.\u003c/p\u003e\u003cp\u003eHowever, there was no statistically significant difference among groups in the delayed examination. Only the SFRC-BFF maintained marginal integrity, with 20% of specimens exhibiting this quality. This may be due to the incorporation of short fibers in flowable composites significantly reducing PS. The presence of short fibers helps the resin retain its structural integrity during the curing process, minimizing the shrinkage process.[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e] SFRC-BFF typically have a higher content of fillers. The filler system in this material, usually made from silica and/or barium glass, plays an equally important role in the material\u0026rsquo;s cyclic aging resistance. These fillers contribute to Wear resistance, providing abrasion resistance and helping the material maintain its integrity during the masticatory cycle. This is especially important for preventing marginal deterioration after the material undergoes repeated mechanical stress. The dimensional stability of inorganic fillers helps maintain the composite\u0026rsquo;s shape and structure during thermal cycling (heating and cooling), preventing excessive expansion or contraction. This helps avoid forming marginal gaps that could lead to microleakage or secondary caries.[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eA study by Roggendorf \u003cem\u003eet al.\u003c/em\u003e[\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e] Stated that gap-free margins were primarily found under thermomechanical stress conditions. And ElAziz \u003cem\u003eet al.\u003c/em\u003e[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e] Who evaluated flowable short fiber-reinforced flowable composite restorations compared to conventional packable composites and found no significant differences between the groups, noting an increase in gaps in marginal integrity after 6 and 12 months.\u003c/p\u003e\u003cp\u003eThe BFF resin-based composite group showed open enamel margins after cyclic aging, likely due to the fluoride-releasing Ytterbium Fluoride (YbF3). Fluoride promotes hydrolytic degradation of the resin matrix, increasing water sorption in the composite over time. This can lead to resin softening and ultimately result in bond degradation at the resin-enamel interface, causing margin failure. Additionally, chemical interactions between fluoride and the composite may further destabilize the bond under long-term moisture exposure and cyclic aging. Moreover, barium glass fillers enhance the mechanical properties of composites but may affect bonding enamel. Fillers can stress the resin-filler interface if poorly bonded to the resin matrix. Cyclic loading, like chewing, may debond fillers, leading to failure at the composite-enamel interface and weakening overall strength adhesion.\u003c/p\u003e\u003cp\u003eMoreover, the ORMOCER-based BFF group had large filler particles like glass ceramic fillers with a particle size of 1 \u0026micro;m) which can reduce the material's flexibility, making it more prone to stress concentration. While nanofillers improve surface smoothness and mechanical properties, their presence with larger fillers can reduce adaptability to the enamel surface during polymerization and cyclic loading. High filler loading typically enhances mechanical properties like strength and wear resistance. Still, exceeding a threshold (e.g., 70\u0026ndash;80%) can increase the material's viscosity, which may negatively affect the composite's wetting ability on the enamel surface. If the resin fails to wet and adapt to the enamel surface adequately, it may not form a strong bond. Marginal gaps can form due to incomplete interface filling.\u003c/p\u003e\u003cp\u003eIn addition, the self-adhesive flowable incorporated with pre-polymerized fillers are typically added to improve the composite material's strength and wear resistance. However, their addition can affect the polymerization process and the adaptation to the enamel. If the polymerization of the pre-polymerized fillers is not perfectly coordinated with the surrounding matrix material, it could result in incomplete polymerization or weak spots within the resin matrix. These weak spots can lead to microcracks or debonding at the interface, contributing to the development of marginal gaps. Furthermore, the mechanical loading from chewing forces may exacerbate any pre-existing micro gaps and cause marginal failure. The combination of methacrylate monomers and fillers, particularly YbF3, can also enhance hydrolytic degradation at the enamel-resin interface after extended exposure to moisture, as observed in the oral cavity. Water absorption within the resin matrix produces softening and swelling, which may cause the bond to disintegrate. Cyclic aging, which simulates the thermal and mechanical stresses during mastication, can expedite this process, ultimately forming marginal gaps.\u003c/p\u003e\u003cp\u003eInjectable flowable composites with barium and strontium fillers have different thermal expansion coefficients (CTE) than enamel. Thermomechanical cycling, which simulates the changes in temperature (from hot to cold) and the mechanical forces from chewing, can cause both the composite and the enamel to expand and contract at different rates. A CTE mismatch increases stress at the resin-enamel interface during thermal cycling, leading to marginal gaps or debonding. This issue worsens if the composite is overly filled with inorganic materials like barium glass strontium.\u003c/p\u003e\u003cp\u003eDe Albuquerque Jass\u0026eacute; \u003cem\u003eet al.\u003c/em\u003e[\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e] supported our results when evaluated the marginal adaptation before and after TMC of the BFF and conventional composite resin. A significant improvement in marginal adaptation was observed when BFF was used instead of traditional composite resin before and after TMC. The results of this study confirm that the BFF-RBCs tested have characteristics comparable to or superior to those of conventional resin regarding marginal adaptation. However, only long-term clinical trials can confirm the clinical success of the material.\u003c/p\u003e\u003cp\u003eOn the other hand, internal adaptation was preserved in all groups during the baseline examination except for the conventional flowable composite. We noted a gap in 90% of specimens in that group at baseline examination, likely due to the inconsistent hybrid layer formation. Low filler content, moisture sensitivity, and limited adhesive penetration into dentin affect traditional flowable composites. Dentin surfaces are treated less intensively, and improper conditioning, such as inadequate smear layer disruption, can prevent optimal bonding. The smear layer can block adhesive penetration and negatively impact bonding. Moreover, low-viscosity flowable composites have higher shrinkage rates due to reduced filler, risking separation from tooth structure and diminishing adhesion and marginal adaptation.\u003c/p\u003e\u003cp\u003eThe SFRC-BFF group's adhesive's inability to properly penetrate dentin due to a lack of demineralization results in weak bonding to dentin. Several factors can contribute to this, mostly its weak formulation, which is missing many strong adhesive compounds such as MDP and other methacrylates. Its weak acidity also results in poor adhesive penetration. In conjunction with the selective etching technique, this could result in more significant gaps in dentin after thermocycling aging and force loading on the bonding interface.\u003c/p\u003e\u003cp\u003eORMOCER-based BFF group showed internal gaps mainly due to Diethyl amino benzaldehyde (DEAB), used as an accelerator in adhesive polymerization, which can contribute to weakening the dentin bond over time, especially after cyclic aging. One of the key factors is oxidative degradation, as DEAB can undergo oxidation in the presence of oxygen, particularly when exposed to moisture. This oxidation can interfere with the polymerization process, leading to incomplete curing and reduced bond strength. Additionally, DEAB is water-soluble and may leach into the oral environment, causing hydrolytic degradation of the adhesive bond when exposed to saliva and moisture. This leaching can further compromise the bond's durability. Moreover, while DEAB aids in speeding up polymerization, it may not effectively contribute to the crosslinking of the polymer network, resulting in a weaker matrix that is more susceptible to thermal cycling and mechanical stress, ultimately leading to a weakened dentin bond.\u003c/p\u003e\u003cp\u003eThe BFF resin-based composite group contains hydroxyethyl methacrylate (HEMA), a hydrophilic monomer used in its adhesive system to enhance wetting and penetration into dentin. While HEMA improves initial bond strength, it can pose problems over time, especially under cyclic aging. Due to its hydrophilic nature, HEMA can cause water absorption into the adhesive layer. Over time, this moisture can lead to hydrolytic degradation of the resin-dentin interface and result in marginal leakage. HEMA\u0026rsquo;s softening effect on the resin can make the bond more vulnerable to mechanical stresses, such as thermal cycling and masticatory forces, weakening the bond over time. Alongside methacryloxyethyltrimellitic acid anhydride (4-META) monomer, which is also used in this adhesive, reacts with dentin to form chemical bonds. However, its sensitivity to moisture can also result in hydrolytic degradation under cyclic aging conditions.\u003c/p\u003e\u003cp\u003eSelf-adhering flowable showed internal gaps, possibly due to glycerol phosphate dimethacrylate (GPDM), a newer monomer in self-adhering composites. It enhances chemical bonding to dentin by reacting with hydroxyapatite and forming a stable bond to the substrate. However, after cyclic aging, GPDM may contribute to bond failure due to phosphate groups, which are susceptible to hydrolytic degradation when exposed to water over time. Moisture infiltration at the interface can cause the phosphate ester bonds to break down, leading to bond failure at the resin-dentin interface.\u003c/p\u003e\u003cp\u003eUltimately, internal adaptation revealed gaps exceeding 1 \u0026micro;m across all groups during the delayed evaluation. There were statistically significant differences in all groups except conventional flowable composite. Dentin is a porous tissue that contains water and organic materials. The resin matrix formed with Bis-EMA, UDMA, and dimethacrylate monomers is relatively hydrophobic; this moisture could impair the resin\u0026rsquo;s capacity to create a strong bond with dentin, which resulted in discontinuous internal margins before the aging process. Moreover, cyclic aging typically replicates temperature fluctuations (thermal cycling) and mechanical stress (chewing forces), which can lead to the expansion and contraction of the resin. Consequently, water absorption and demineralization can weaken the adhesive bond over time if the resin is hydrophobic and does not adhere effectively to dentin. Following cyclic aging, the bond may deteriorate further due to water infiltration at the interface.\u003c/p\u003e\u003cp\u003eA study by Roggendorf \u003cem\u003eet al.\u003c/em\u003e[\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e] Agreed with this study and found a larger gap formation internally after TMC. Also Tonetto \u003cem\u003eet al.\u003c/em\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] Demonstrated that TMC obstructed the adaptation of dentin in every group compared to the initial conditions. In contrast Karabekiroglu \u003cem\u003eet al.\u003c/em\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] observed that TMC doesn\u0026rsquo;t have an adverse effect on the dentin bond strength of most adhesive systems in Class V cavities. Also, El Naga \u003cem\u003eet al.\u003c/em\u003e[\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e], the dentin integrity and BFFs were compared with conventional RBCs, which were used in both bulk filling techniques. The study's results revealed that the BFF restorations demonstrated a similar marginal gap formation to conventional universal RBCs under their research conditions.\u003c/p\u003e\u003cp\u003eIn the same way as our result, Elhawary \u003cem\u003eet al.\u003c/em\u003e and Kamar \u003cem\u003eet al.\u003c/em\u003e [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e] A comparison of BFF and conventional flowable composites showed that the BFF composite has lower microleakage scores than the traditional flowable composite at both occlusal and gingival margins. This may be due to the established multifunctional methacrylate monomers, such as UDMA (urethane dimethacrylate) and EBADMA (ethoxyethyl methacrylate), which provide strong bonding to the tooth structure and resistance to stress, both of which are crucial for the longevity of restorations.\u003c/p\u003e\u003cp\u003eIn contrast to our study, Maj \u003cem\u003eet al.\u003c/em\u003e [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]Conducted a comparative clinical study on the Self-adhering flowable composite and the traditional flowable composite. After six months, they found visible superficial damage to the margins of the filling in almost all cases of the Self-adhering flowable, while most cases with the traditional flowable composite exhibited better marginal integrity simultaneously. These differences may be due to the methodology used. Also, Baltacioğlu \u003cem\u003eet al.\u003c/em\u003e [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e] Compared to composite groups with low viscosities, the conventional flowable exhibited the lowest leakage, with no statistically significant difference from the BFF group.\u003c/p\u003e\u003cp\u003eThe current study's findings on thermomechanical affect all materials' marginal and internal adaptation with statistically significant differences among all groups. This contrasts with Casselli \u003cem\u003eet al.\u003c/em\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] Evaluated the effect of TMC, margin location, and the adhesive system on the marginal adaptation of Class V cavities restored with micro-hybrid resin composite restorations. They concluded that the TMC did not alter the gap measurements and did not affect marginal adaptation.\u003c/p\u003e\u003cp\u003eAccording to the results of this study the null hypothesis states that the type of restoration didn\u0026rsquo;t affect the marginal adaptation at baseline examination has been accepted. The type of restoration that did not affect the marginal adaptation during the delayed examination has been rejected. The type of restoration did not affect the internal adaptation during the baseline examination. On the other hand, the type of restoration did not impact the internal adaptation during the delayed examination, and this result has been rejected.\u003c/p\u003e\u003cp\u003eThe limitations of this study that restorative materials were assessed under laboratory conditions (\u003cem\u003ein vitro\u003c/em\u003e study). The dynamic environment of the oral cavity, influenced by factors like saliva flow, pH variations, and the patient's dietary habits, can yield results differing from those demonstrated in this study. Therefore, conducting further research through clinical trials is essential.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eDifferent flowable composite restorative systems exhibited good marginal and internal adaptation in class V Cavities. The short fiber-reinforced flowable composite restorative system had better adaptation than other restorative systems, and thermomechanical Cyclic Loading exerted a negative effect on both marginal and internal adaptation\u003c/p\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003eRecommendations\u003c/h2\u003e\u003cp\u003eDifferent cavity designs and sizes are needed to test the effectiveness of the tested materials and confirm the current study's results. Further research is required, utilizing different thermomechanical cycling durations. More \u003cem\u003ein vivo\u003c/em\u003e studies should be conducted to evaluate and compare the clinical performance of the tested materials. Using a 3D tool like micro-CT for measuring marginal and internal gaps can provide a superior assessment compared to 2D techniques. It evaluates not just the width and length of the gaps, but also their depth.\u003c/p\u003e\u003c/div\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eBFF\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eBulk Fill flowable\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eBF-RBCs\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003ebulk-fill resin-based composites\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eCEJ\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003ecementoenamel junction\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eCM\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eContinuous margin\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eDC\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003edegree of conversion\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eDEAB\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eDiethyl amino benzaldehyde\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eEBADMA\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eethoxyethyl methacrylate\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eFig.\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eFigure\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eGPDM\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eglycerol phosphate dimethacrylate\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eHEMA\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003ehydroxyethyl methacrylate\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eMDP\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eMethacryloyloxydecyl dihydrogen phosphate\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eMA\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003emarginal adaptation\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eSEM\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eScanning electron microscope\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eTMC\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eThermo-mechanical cycling\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eUDMA\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eurethane dimethacrylate\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026micro;m\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003emicrometer\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSpecial thanks to my dear husband, who supported me from the very beginning and through each obstacle in this work\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo funding received.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number:\u003c/strong\u003e not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAuthors and Affiliations\u003c/p\u003e\n\u003cp\u003e1: MSc, Conservative Dentistry Department, Faculty of Dentistry, Mansoura University, Mansoura, Egypt, Email: [email protected] https://orcid.org/0009-0001-5164-4792 \u003c/p\u003e\n\u003cp\u003e2: Lecturer, Conservative Dentistry Department, Faculty of Dentistry, Mansoura University, Mansoura, Egypt, Email: [email protected] https://orcid.org/0000-0001-8120-5830 \u003c/p\u003e\n\u003cp\u003e3: Professor, Conservative Dentistry Department, Faculty of Dentistry, Mansoura University, Mansoura, Egypt : Email: [email protected] https://orcid.org/0000-0002-7776-2308 \u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorrespondence author:\u003c/strong\u003eSahar A Saleh, Department of Conservative Dentistry, Faculty of Dentistry, Mansoura University, (E-mail: [email protected]). mobile: +201559571748 \u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors contributed to clinical procedures, writing, preparing figures, and reviewing the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics declarations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe current study obtained its approval from the Research Ethics Committee of Faculty of Dentistry, Mansoura University No. (A03012023CD).The procedures were carried out following the relevant laws and regulations. Written informed consent was obtained from all participants or their legal guardians for each donor tooth.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated and/or analyzed during the current study are not publicly available [as it is not published yet], but are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eScepanovic D, Par M, Attin T, Taub\u0026ouml;ck TT. Marginal adaptation of flowable vs sonically activated or preheated resin composites in cervical lesions. J Adhes Dent. 2022;24:247\u0026ndash;57.\u003c/li\u003e\n \u003cli\u003eVan Ende A, De Munck J, Lise DP, Van Meerbeek B. Bulk-Fill Composites: A Review of the Current Literature. J Adhes Dent. 2017;19:95\u0026ndash;110.\u003c/li\u003e\n \u003cli\u003eCasselli DSM, Faria-E-Silva AL, Casselli H, Martins LRM. Marginal adaptation of class V composite restorations submitted to thermal and mechanical cycling. J Appl Oral Sci. 2013;21:68\u0026ndash;73.\u003c/li\u003e\n \u003cli\u003eRengo C, Goracci C, Ametrano G, Chieffi N, Spagnuolo G, Rengo S, et al. Marginal leakage of class V composite restorations assessed using microcomputed tomography and scanning electron microscope. Oper Dent. 2015;40:440\u0026ndash;8.\u003c/li\u003e\n \u003cli\u003eVersluis A, Tantbirojn D, Lee MS, Tu LS, Delong R. Can hygroscopic expansion compensate polymerization shrinkage? part I. deformation of restored teeth. Dent Mater. 2011;27:126\u0026ndash;33.\u003c/li\u003e\n \u003cli\u003eCasselli DSM, Faria-E-Silva AL, Casselli H, Martins LRM. Marginal adaptation of class V composite restorations submitted to thermal and mechanical cycling. J Appl Oral Sci. 2013;21:68\u0026ndash;73.\u003c/li\u003e\n \u003cli\u003eGayatri C, Rambabu T, Sajjan G, Battina P, Priyadarshini MS, Sowjanya BL. Evaluation of Marginal Adaptation of a Self-Adhering Flowable Composite Resin Liner: A Scanning Electron Microscopic Study. Contemp Clin Dent. 2018;9:240\u0026ndash;5.\u003c/li\u003e\n \u003cli\u003eIsmail HS, Ali AI, Mehesen RE, Juloski J, Garcia-Godoy F, Mahmoud SH. Deep proximal margin rebuilding with direct esthetic restorations: a systematic review of marginal adaptation and bond strength. Restor Dent Endod. 2022;47:1\u0026ndash;18.\u003c/li\u003e\n \u003cli\u003eAl-Atyaa ZT, Majeed MA. Comparative evaluation of the marginal and internal fitness of monolithic cad/cam zirconia crowns fabricated from different conventional impression techniques and digital impression using silicone replica technique : an in vitro study. Biomed Pharmacol J. 2018;11:477\u0026ndash;90.\u003c/li\u003e\n \u003cli\u003eMourouzis P, Koulaouzidou EA, Palaghias G, Helvatjoglu-Antoniades M. Color match of resin composites to intact tooth structure. J Appl Biomater Funct Mater. 2015;13:259\u0026ndash;65.\u003c/li\u003e\n \u003cli\u003eSadeghi M. An in vitro microleakage study of class V cavities restored with a new self-adhesive flowable composite resin versus different flowable materials. Dent Res J (Isfahan). 2012;9:460\u0026ndash;5.\u003c/li\u003e\n \u003cli\u003eTonetto MR, Band\u0026eacute;ca MC, De Oliveira Barud HG, Pinto SCS, Lima DM, Borges AH, et al. Influence of artificial aging in marginal adaptation of mixed class V cavities. J Contemp Dent Pract. 2013;14:316\u0026ndash;9.\u003c/li\u003e\n \u003cli\u003eIsmail HS, Ali AI, Mehesen R El, Garcia-Godoy F, Mahmoud SH. In vitro marginal and internal adaptation of four different base materials used to elevate proximal dentin gingival margins. J Clin Exp Dent. 2022;14:550\u0026ndash;9.\u003c/li\u003e\n \u003cli\u003ePark KJ, Pfeffer M, N\u0026auml;ke T, Schneider H, Ziebolz D, Haak R. Evaluation of low-viscosity bulk-fill composites regarding marginal and internal adaptation. Odontology. 2021;109:139\u0026ndash;48.\u003c/li\u003e\n \u003cli\u003eAggarwal V, Singla M, Yadav S, Yadav H. Effect of flowable composite liner and glass ionomer liner on class II gingival marginal adaptation of direct composite restorations with different bonding strategies. J Dent. 2014;42:619\u0026ndash;25.\u003c/li\u003e\n \u003cli\u003eJati AS, Furquim LZ, Consolaro A. Gingival recession: its causes and types, and the importance of orthodontic treatment. Dental Press J Orthod. 2016;21:1\u0026ndash;18.\u003c/li\u003e\n \u003cli\u003eBajabaa S, Balbaid S, Taleb M, Islam L, Elharazeen S, Alagha E. Microleakage evaluation in class V cavities restored with five different resin composites: in vitro dye leakage study. Clin Cosmet Investig Dent. 2021;13:1\u0026ndash;15.\u003c/li\u003e\n \u003cli\u003eTorres CRG, Mailart MC, Moecke SE, Matuda AGN, Veloso SM, da Silva \u0026Aacute;vila DM, et al. Flowable bulk-fill versus layering restorative material on class II restorations: a randomized clinical trial. J Dent. 2024;148:1\u0026ndash;9.\u003c/li\u003e\n \u003cli\u003eSooraparaju SG, Kanumuru PK, Nujella SK, Konda KR, Reddy KBK, Penigalapati S. A comparative evaluation of microleakage in class v composite restorations. Int J Dent. 2014;2014:1\u0026ndash;4.\u003c/li\u003e\n \u003cli\u003eShadman N, Pezeshki B, Rostami S. Marginal sealing of bulk fill versus conventional composites in class II composite restorations: an in vitro study. Front Dent. 2020;17:1\u0026ndash;6.\u003c/li\u003e\n \u003cli\u003eFreitas D, Cia L, Lima D, Rodolfo X, De Azeve LJ, Alonso R, et al. Bonding performance and mechanical properties of flowable bulk-fill and traditional composites in high c-factor cavity models. J Conserv Dent. 2014;8:1\u0026ndash;36.\u003c/li\u003e\n \u003cli\u003eWahab FK, Shaini FJ, Morgano SM. The effect of thermocycling on microleakage of several commercially available composite class v restorations in vitro. J Prosthet Dent. 2003;90:168\u0026ndash;74.\u003c/li\u003e\n \u003cli\u003eIspas A, Moldovan M, Cuc S, Prodan D, Bacali C, Petean I, et al. SEM evaluation of marginal adaptation e-max crowns manufactured by printing-pressed and milling. Diagnostics. 2023;13:1\u0026ndash;14.\u003c/li\u003e\n \u003cli\u003eTrifkovic B. Application of replica technique and SEM in accuracy measurement of ceramic crowns. Meas Sci Rev. 2012;4:1\u0026ndash;14.\u003c/li\u003e\n \u003cli\u003eCosta AT, Konrath F, Dedavid B, Weber JBB, de Oliveira MG. Marginal adaptation of root-end filling materials: an in vitro study with teeth and replicas. J Contemp Dent Pract. 2009;10:1\u0026ndash;12.\u003c/li\u003e\n \u003cli\u003eGunjal S, Nagesh L, Raju HG. Comparative evaluation of marginal integrity of glass ionomer and resin based fissure sealants using invasive and non-invasive techniques: an in vitro study. Indian J Dent Res. 2012;23:320\u0026ndash;5.\u003c/li\u003e\n \u003cli\u003eGloria Kang GJ, Ewing-Nelson SR, Mackey L, Schlitt JT, Marathe A, Abbas KM SS. Cyclic mechanical loading promotes bacterial penetration along composite restoration marginal gaps. Physiol Behav. 2018;176:139\u0026ndash;48.\u003c/li\u003e\n \u003cli\u003evon Fraunhofer JA, Adachi EI, Barnes DM, Romberg E. The effect of tooth preparation on microleakage behavior. Oper Dent. 2000;25:526\u0026ndash;33.\u003c/li\u003e\n \u003cli\u003eSoriano-Valero S, Rom\u0026aacute;n-Rodriguez JL, Agust\u0026iacute;n-Panadero R, Bellot-Arc\u0026iacute;s C, Fons-Font A, Fern\u0026aacute;ndez-Estevan L. Systematic review of chewing simulators: reality and reproducibility of in vitro studies. J Clin Exp Dent. 2020;12:1189\u0026ndash;95.\u003c/li\u003e\n \u003cli\u003eMorresi AL, D\u0026rsquo;Amario M, Capogreco M, Gatto R, Marzo G, D\u0026rsquo;Arcangelo C, et al. Thermal cycling for restorative materials: does a standardized protocol exist in laboratory testing? a literature review. J Mech Behav Biomed Mater. 2014;29:295\u0026ndash;08.\u003c/li\u003e\n \u003cli\u003eAngwarawong T, Reeponmaha T, Angwaravong O. Influence of thermomechanical aging on marginal gap of CAD-CAM and conventional interim restorations. J Prosthet Dent. 2020;124:566\u0026ndash;77.\u003c/li\u003e\n \u003cli\u003eJordehi A, Shahabi M, Akbari A. Comparison of self-adhering flowable composite microleakage with several types of bonding agent in class V cavity restoration. Dent Res J (Isfahan). 2019;16:257\u0026ndash;63.\u003c/li\u003e\n \u003cli\u003eAgarwal RS, Hiremath H, Agarwal J, Garg A. Evaluation of cervical marginal and internal adaptation using newer bulk fill composites: an in vitro study. J Conserv Dent. 2015;18:56\u0026ndash;61.\u003c/li\u003e\n \u003cli\u003eAbdelwahed AG, Essam S, Abdelaziz MM. Marginal adaptation and depth of cure of flowable versus packable bulk-fill restorative materials: an in vitro study. J Med Sci. 2022;10:47\u0026ndash;56.\u003c/li\u003e\n \u003cli\u003eMagne P, Carvalho MA, Milani T. Shrinkage-induced cuspal deformation and strength of three different short fiber-reinforced composite resins. J Esthet Restor Dent. 2023;35:56\u0026ndash;63.\u003c/li\u003e\n \u003cli\u003eHarp YS, Montaser MA, Zaghloul NM. Flowable fiber-reinforced versus flowable bulk-fill resin composites: degree of conversion and microtensile bond strength to dentin in high c-factor cavities. J Esthet Restor Dent. 2022;34:699\u0026ndash;06.\u003c/li\u003e\n \u003cli\u003eRoggendorf MJ, Kr\u0026auml;mer N, Appelt A, Naumann M, Frankenberger R. Marginal quality of flowable 4-mm base vs. conventionally layered resin composite. J Dent. 2011;39:643\u0026ndash;7.\u003c/li\u003e\n \u003cli\u003eElAziz RHA, ElAziz SAA, ElAziz PMA, Frater M, Vallittu PK, Lassila L, et al. Clinical evaluation of posterior flowable short fiber-reinforced composite restorations without proximal surface coverage. Odontology. 2024;4:1\u0026ndash;10.\u003c/li\u003e\n \u003cli\u003eJass\u0026eacute; FF de A, Alencar C de M, Zaniboni JF, Silva AM, Campos EA de. Assessment of marginal adaptation before and after thermo-mechanical loading and volumetric shrinkage: bulk fill versus conventional composite. Int J Odontostomatol. 2020;14:60\u0026ndash;6.\u003c/li\u003e\n \u003cli\u003eEl Naga MA, Qian F, Denehy GE, Quock RL, Armstrong SR. Marginal adaptation and internal indentation resistance of a Class II bulk-fill resin-based composite. Am J Dent. 2020;33:145\u0026ndash;50.\u003c/li\u003e\n \u003cli\u003eElhawary AA, Elkady AS, Kamar AA. Comparison of degree of conversion and microleakage in bulkfill flowable composite and conventional flowable composite(an in vitro study). Alexandria Dent J. 2016;41:336\u0026ndash;43.\u003c/li\u003e\n \u003cli\u003eMaj A, Trzcionka A, Twardawa H, Tanasiewicz M. A comparative clinical study of the self-adhering flowable composite resin vertise flow and the traditional flowable composite resin premise flowable. Coatings. 2020;10:1\u0026ndash;16.\u003c/li\u003e\n \u003cli\u003eBaltacioğlu İH, Demirel G, \u0026Ouml;zt\u0026uuml;rk B, Aydin F, Orhan K. Marginal adaptation of bulk-fill resin composites with different viscosities in class II restorations: a micro-ct evaluation. BMC Oral Health. 2024;24:1\u0026ndash;7.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Class V cavity, Flowable Composite, Internal adaptation, Marginal adaptation, Thermomechanical","lastPublishedDoi":"10.21203/rs.3.rs-7446404/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7446404/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eObjective: \u003c/strong\u003eThis study aimed to evaluate and compare marginal and internal adaptation of different flowable composite restorations in class V cavities after thermomechanical cyclic loading.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMaterial and methods: \u003c/strong\u003eOne hundred freshly extracted human premolars with class V cavities on the facial surface were randomly assigned into five main groups (n=20) according to the type of restoration materials. Group I was restored with short fiber-reinforced flowable, group II with self-adhesive flowable, group III with ORMOCER-based bulkfill flowable, group IV with resin-based bulkfill flowable, and group V with injectable flowable. Each group was divided into two equal subgroups (n=10) according to the examination state at Non-Thermomechanical cyclic loading (N-TMC) and after thermomechanical cyclic loading (TMC). However, the TMC subgroup was evaluated after thermomechanical cyclic loading, which involved 5000 thermal cycles (5°±1℃ to 55°±1℃) and simultaneous mechanical stress applied with 100,000 load cycles at 100 N and 4 Hz, and evaluated for marginal and internal adaptation using a scanning electron microscope. The data were statistically analyzed using the Monte Carlo test to compare the studied groups, and the McNemar test was used to compare N-TMC and TMC results, with a statistically significant level set at (P≤0.05).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults: \u003c/strong\u003eThere were no statistically significant differences at N-TMC and TMC results for marginal adaptation when comparing between groups with P = 1.0 and 0.08, respectively. In other ways, there were statistically significant differences when comparing both states in the same groups, with P= 0.007 for group I and P ≤ 0.001 for all other groups. Additionally, there was a statistically significant difference in N-TMC results for internal adaptation when comparing groups with P\u0026lt;0.001, and no statistically significant difference between the groups in the delayed state p = 1.0. Finally, there was a statistically significant difference when comparing N-TMC with TMC in all groups with p \u0026lt;0.001 except group V, where there was no statistically significant difference with P=1.0.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions\u003c/strong\u003e: Different flowable composite restorations exhibited good marginal and internal adaptation in class V cavities. Short fiber-reinforced flowable composite restorative system had better adaptation than other restorations. Thermomechanical cyclic loading exerted a negative effect on both marginal and internal adaptation\u003c/p\u003e","manuscriptTitle":"Marginal and Internal Adaptation of Different Flowable Composite Restorations in Class V Cavities after Thermomechanical Cyclic Loading: In vitro study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-09 03:27:59","doi":"10.21203/rs.3.rs-7446404/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-09-19T07:33:25+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-15T08:22:30+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"338750127006502513542699823884407254418","date":"2025-09-07T16:13:23+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"277271223157556018940677195004312790992","date":"2025-09-04T18:42:54+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-03T17:59:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"255589885098340795700925559385337213206","date":"2025-09-02T11:46:43+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-02T11:26:46+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-08-30T09:53:36+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-08-30T09:52:48+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Oral Health","date":"2025-08-24T13:17:05+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"ed3c5836-bf5e-426b-98da-cc9c64e6532f","owner":[],"postedDate":"September 9th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-12-15T16:15:59+00:00","versionOfRecord":{"articleIdentity":"rs-7446404","link":"https://doi.org/10.1186/s12903-025-07324-0","journal":{"identity":"bmc-oral-health","isVorOnly":false,"title":"BMC Oral Health"},"publishedOn":"2025-12-09 15:58:25","publishedOnDateReadable":"December 9th, 2025"},"versionCreatedAt":"2025-09-09 03:27:59","video":"","vorDoi":"10.1186/s12903-025-07324-0","vorDoiUrl":"https://doi.org/10.1186/s12903-025-07324-0","workflowStages":[]},"version":"v1","identity":"rs-7446404","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7446404","identity":"rs-7446404","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}