Influence of ultrasonic activation of the photodynamic therapy photosensitizer on the bond strength of gutta-percha/bioceramic sealer and fiberglass posts/self-adhesive cement

Influence of ultrasonic activation of the photodynamic therapy photosensitizer on the bond strength of gutta-percha/bioceramic sealer and fiberglass posts/self-adhesive cement | 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 Influence of ultrasonic activation of the photodynamic therapy photosensitizer on the bond strength of gutta-percha/bioceramic sealer and fiberglass posts/self-adhesive cement Alexia Trento, Matheus Albino Souza, Vitor Hugo Sanches Menchik, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7643161/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Introduction the role of endodontic treatment is to eliminate microorganisms without compromising adjacent tissues and adhesion. The aim of present study was to evaluate the influence of ultrasonic activation (US) of the photodynamic therapy (PDT) photosensitizer on the bond strength of filling and restorative material. Methods sixty single-rooted teeth were used. After coronal sectioning, 30 roots were used to assess the bond strength of filling material and 30 to assess the bond strength of restorative material. After complete chemomechanical preparation, the roots were randomly divided into three groups in both evaluations (n = 10), according to PDT and US protocol: G1(negative control)–distilled water; G2–conventional PDT; G3–PDT + US. Then the roots were filled with gutta-percha/Bio-C bioceramic sealer in the first evaluation, and with fiber glass posts/Rely-X U200 self-adhesive cement in the second evaluation. In both evaluations, the roots were sectioned to obtain 1 mm thick dentin discs containing the filling/restorative material, and the push-out test was performed. Failure patterns were observed under optical microscope. Specific statistical analysis was performed in both evaluations (α 5%). Results in both evaluations, bond strength was significantly lower in groups 2(PDT) and 3(PDT + US) compared to control group (p 0.05). Regarding the failure patterns, no statistically significant difference was found between groups (p > 0.05), with a predominance of cohesive failure in all groups. Conclusion US of the PDT photosensitizer did not influence the bond strength of gutta-percha/bioceramic sealer and fiber glass posts/self-adhesive cement to root dentin when compared to conventional PDT. bioceramic sealer bond strength photodynamic therapy photosensitizer self-adhesive cement ultrasonic activation INTRODUCTION Some bacteria are resistant to conventional intra-canal managements. It creates conditions for proliferation, leading to the development of persistent infections in the root canal system [ 1 ]. Therefore, the use of auxiliary decontamination resources is mandatory in endodontic treatment. The photodynamic therapy (PDT) involves the ability of a photosensitizer to absorb light-energy and to react with oxygen, generating reactive oxygen species. As a consequence, this reactive oxygen adheres and penetrates the bacterial cell wall, precipitating the cytoplasmic content and inducing damage to the DNA of the bacterial cell [ 2 ]. On the other hand, ultrasonic activation (US) has also contributed to greater decontamination, due to the increase in temperature and hydrostatic pressure of the irrigant agents which are used into the root canals [ 3 ]. According to Ghinzelli et al. [ 4 ], the use of US over the photosensitizer of PDT resulted in higher elimination of bacteria from the root canal space. Although this association presents significant aid in the decontamination process, this therapeutic modality can compromise the adhesion of filling and restorative materials to the root canal walls. The photosensitizers presents hydrophilic nature, low molecular weight, and high viscosity. It creates a chemical smear layer that adheres strongly to the canal walls and dentinal tubules [ 5 ], reducing the bond strength of filling and restorative materials [ 6 , 7 ]. In addition, the US can induce greater impulse and impregnation of the photosensitizer to the canal walls, further compromising adhesion. However, there are no studies in the literature revealing the impact of the association of PDT and US on the bond strenght of new filling and restorative materials to the root canal walls. Recent research in the field of endodontics has demonstrated scientific evidence for the use of bioceramic sealers as filling materials. Bioceramic sealers exhibit biocompatibility [ 8 ] and bioactivity [ 9 ]. It releases hydroxyl ions, promoting an alkaline pH [ 10 ], capable of contributing to antimicrobial activity against persistent infections.4 Among other properties, it also demonstrates adequate bond strength to dentin, reducing the interface between the filling material and root canal walls [ 11 ]. When the coronal portion presents extensive loss, the use of self-adhesive resin cement has been recommended to promote better bond strength of glass fiber posts (GFP) to the root dentin, resulting in effective polymerization and preservation of the bonding interface [ 12 ]. Considering the development of new decontamination protocols, as well as the diversity of alternatives for filling and restoration, it is essential to evaluate their relationship to provide support for their clinical use. Thus, the aim of present study is to evaluate the influence of US of the PDT photosensitizer on the bond strength of filling material composed by gutta-percha and bioceramic sealer, and restorative material composed by GFP and self-adhesive cement. The hypotheses of this study were that US of the PDT photosensitizer (i) decreases the bond strength of filling and (ii) restorative materials to root dentin. MATERIAL AND METHODS This study was appreciated and approved by the local Ethics Commission. Sample collection and preparation Sixty hundred single-rooted extracted human teeth were used in the present study. All teeth were obtained from the Biobank of the School of Dentistry of the University of Passo Fundo (Passo Fundo, RS, Brazil). Dental crowns were sectioned with a rotary diamond disc (#911H, Brasseler, Savannah, GA, United States) so that all roots retained a length of 15 mm. The root length of 15 mm was measured with a ruler, a mark was made on each root in the measurement of 15 mm and the cut was performed at this length, standardizing the length of all roots. After this, 30 roots were prepared by single operator, using the same protocol for pulp tissue removal and standardization of the root canal diameter. The working length (WL) was established by introducing a K-file #10 (Dentsply-Maillefer, Ballaigues, Switzerland) into the canal until its tip was visualized at the apical foramen. From this measurement, 1 mm was subtracted to obtain the WL. Each tooth was fixed in a portable lathe machine, in order to maintain the tooth secured during the root canal preparation. The roots were enlarged to WL using the ProTaper system (Dentsply- Maillefer), following the sequence S1 to F3. Distilled water (DW) (Natupharma, Passo Fundo, RS, Brazil) was used as irrigant solution and renewed at each instrument change. The ProTaper files (Dentsply-Maillefer) were used in a 16:1 gear reduction handpiece powered by a torque-controlled electric motor (X-Smart Plus - Dentsply-Maillefer, Ballaigues, Switzerland) at a constant rotation speed of 300 rpm in a crown-down manner according to the manufacturer’s instructions, by using a gentle in-and-out digital motion. The remaining 30 roots were flared at their coronal and middle thirds using Gates Glidden drills no. 2, 3 and 4 to a depth of 10 mm, to provide adequate space for cementation of GFP. The Gates Glidden drills were used in a low speed handpiece powered by micro electric motor at a constant rotation speed of 10.000 rpm in a crown-down manner, by using a gentle in-and-out digital motion. All root canals were then filled with 17% EDTA (Biodinâmica, Ibiporã, PR, Brazil), and all roots were put into 10 mL plastic vials containing 17% EDTA, such that there were ten samples per vial, so that the roots remained completely covered by the solution. Each plastic vial was inserted into an ultrasonic cleaning machine (Bio Free, Gnatus, Ribeirão Preto, SP, Brazil) for one minute in order to remove the smear layer formed by root canal preparation. After that, the root canals were irrigated with 5mL of DW and dried with absorbent paper points (Tanari, Manacapuru, AM, Brazil). Classification of treatment protocols The 60 specimens were embedded in epoxy resin (Silaex, São Paulo, SP, Brazil), to facilitate PDT protocols and root canal filling. According to experimental tests, 30 specimens were used for evaluation of bond strength of filling material and the remaining 30 specimens were used for evaluation of bond strength of restorative material. In both evaluations, the 30 specimens were randomly divided in three groups (n = 10): G1 – DW: the root canals were filled with DW until extravasation to the root canal entrance. The DW was retained in the root canal for 5 minutes. Then, all roots were irrigated with 5 mL of DW, followed by the aspiration of root canals. G2 – PDT: the root canals were filled with 0.01% (0.1 mg/mL) methylene blue (Chimio Lux DMC, São Carlos, SP, Brazil) until extravasation to the root canal entrance. The photosensitizer was retained in the root canal for 5 min, as pre-irradiation time. After that, a low intensity laser (Therapy XT® DMC, São Carlos, SP, Brazil) was used at 100mW power and continuous emission in the red part of the spectrum (660–690 nm wavelength), with an intra-canal optical fiber of 600 µm diameter, attached at 2 mm short of the working length. The root canals were irradiated for 90 s, with 9 J of total dose delivery and 320 J/cm2 of energy density, remaining the intra-canal fiber in static position, as recommended by the manufacturer. Then, all roots were irrigated with 5 mL of DW, followed by the aspiration of root canals. G3 – PDT + US: the same procedure was performed as described in group 2. However, in the last minute of pre-irradiation time, the photosensitizer was activated by US. The US was performed using an ultrasonic device (Nac Plus ultrasonics — Adiel, Ribeirão Preto, SP, Brazil), with a stainless-steel endodontic tip, which was inserted 2 mm short of the working length and activated for 1 min. The scale power 2 for endodontics was used to promote the US. Every effort was made to minimise contact of the tip with the root canal walls and promote the agitation of photosensitizer. Then, irrigation with 5 mL of distilled water was performed. Root canal filling In the first evaluation (bond strength of the filling material), the 10 specimens of each group were filled by the lateral compaction technique using gutta-percha points (Dentsply-Maillefer) and Bio-C bioceramic sealer (Angelus, Londrina, PR, Brazil). The sealer was applied along the root canal walls using the insertion point of bioceramic sealer. The gutta-percha ProTaper master cone #F3 (Dentsply-Maillefer) was lightly coated with the bioceramic sealer and inserted to the WL. Then, XF gutta-percha accessory points (Dentsply-Maillefe) were introduced into the root canals with the aid of finger spreaders (Dentsply Maillefer, Ballaigues, Switzerland). The gutta-percha accessory points were used until the finger spreader did not penetrate more than 5 millimeters into the root canal. Then, the excess of filling material was removed by cutting with a #2 heated plugger (SS White Duflex, Rio de Janeiro, RJ, Brazil). The root canal entrance was sealed with temporary restorative material (Vidrion R - SS White, Rio de Janeiro, RJ, Brazil). In the second evaluation (bond strength of the restorative material), the 10 specimens of each group were filled with GFP (Angelus, Londrina, PR, Brazil) and Rely-X U200 self-adhesive cement (3M ESPE, St. Paul, MN, USA). The GFP no. 1 (Angelus) was cleaned with 35% phosphoric acid for 30 s, rinsed for 30 s and gently air-dried. The silane application (3M ESPE) was performed for 1 min, followed by Single-Bond adhesive application (3M ESPE) and light polymerization for 40 s with a halogen light source with a power of 600 mV/cm 2 (Optilux, Demetron Res. Corp, Danbury CT, USA). The Single-Bond adhesive (3M ESPE) was applied in root dentin walls using microbrushes, air-dried for 5 s, and light polymerized for 40 s. Subsequently, Rely-X U200 self-adhesive cement (3M ESPE) was mixed and injected into the root canal of the 10 samples of each group with a suitable Centryx syringe and Acudosse needle (DFL, Rio de Janeiro, RJ, Brazil). The GFP was then covered with the same cement and positioned within the root canal at a 10 mm level, and held under digital pressure for 20 s. After this period, excess cement was removed. The cement was then polymerized using a 600 mW/cm 2 halogen light source (Optilux) for 30 s on each face (buccal, palatal, mesial, distal and occlusal). All procedures and parameters from this section were based in the manufacturer’s instruction. Evaluation on bond strength After the filling procedures, all specimens were stored at 37°C and 95% humidity for 21 days. Subsequently, the roots were sectioned transversely from the root canal entrance into 1 mm thick discs in a metallographic cutter with a diamond disk, at a speed of 350 rpm under cooling. The first disc was discarded, and the next five root discs were selected from each sample, totaling 50 specimens per subgroup (n = 5×10 = 50). Each disc was subjected to the push-out test on a mechanical testing machine (Emic DL 2000, São José dos Pinhais, PR, Brazil) at a speed of 1 mm/min using a stainless steel cylindrical plunger of 0.8 mm dia- meter. The plunger tip was positioned so that it only contacted the filling material. The push-out force was applied in an apico-coronal direction until bond failure occurred, which was manifested by extrusion of the filling material and a sudden drop along the load deflection. The force required to displace the material from the root canal was recorded in Newtons (N) and calculated in megapascals (MPa). After the push-out test, each disc was immediately transported in an Eppendorf tube containing DW to the optical microscope site, in order to calculate the bond strength and evaluate the failure patterns. Each disc was removed from the Eppendorf tube with a tweezer, dried with absorbent paper and positioned in the center of optical microscopy (Zeiss, São Paulo, SP, Brazil), at 50× magnification. The bond strength calculation and the failure pattern evaluation were based on a previous study by Dias et al [ 13 ]. The bond strength (δ) in megapascals was calculated using the formula δ = F/A, in which F is the force (N) used by the test machine and A is the area. To calculate the area, the following equation was applied: A = 2πr × h, in which π is the constant value 3.14, r is the radius of the intra-radicular space, and h is the height (mm). The radius of the intra-radicular space of each disc was measured under optical microscopy, with the aid of a software which provided this mensuration. The height of each disc was measured by using a digital pachymeter. Furthermore, the failure patterns were observed in each disc under optical microscopy (Zeiss, São Paulo, SP, Brazil) at 50× magnification. The classification was established as follows: 1: adhesive, between the dentin and the filling/restorative material, absence of filling/restorative material on the dentin walls of the root canal; 2: cohesive, failure of the filling/restorative material, presence of filling/restorative material on the dentin walls of the root canal; and 3: mixed, both failures (1 and 2) could be observed. All procedures and parameters from this section were based in previous study of Dias et al. [ 13 ]. Statistical analysis The normal distribution of results was confirmed by the Kolmogorov–Smirnov test (p = 0.4015). Bond strength was evaluated using a one-way analysis of variance (ANOVA), followed by the Tukey post-hoc test, enabling a quantitative analysis of these data. The failure mode distribution among the groups was evaluated using the chi-squared test, enabling a descriptive analysis of these data. All tests were set at a 5% level of significance. Data were analyzed using Stat Plus AnalystSoft Inc. version 6.0 (Vancouver, BC, Canada). RESULTS The mean and standard deviation of bond strength of the filling and restorative material to the root canal dentin after tested protocols are presented in Tables 1 and 2 , respectively. In both evaluations, the bond strength was significantly lower in groups 2 (PDT) and 3 (PDT + US) when compared to the control group (p 0.05). In addition, it was not revealed statistically significant differences in failure patterns among the groups (p > 0.05), with a higher predominance of cohesive failure in all groups. Table 1 Mean (standard deviation) of bond strength of filling material to root canal dentin (MPa) and percentage of pattern of failure (%) after tested protocols. Group n Push Out Bond Strength Failure mode Adhesive Mixed Cohesive 1. DW a 30 4.93 (1.19) 3.32 33.34 63.34 2. PDT b 30 2.80 (0.73) 0.00 30.00 70.00 3. PDT + US b 30 2.07 (0.86) 10.00 33.33 56.67 * Different superscript lowercase letters indicate, in the column, statistically significant differences (p < 0.05). ** DW, distilled water; PDT, photodynamic therapy; US, ultrasonic activation. Table 2 Mean (standard deviation) of bond strength of restorative material to root canal dentin (MPa) and percentage of pattern of failure (%) after tested protocols. Group n Push Out Bond Strength Failure mode Adhesive Mixed Cohesive 1. DW a 30 4.62 (1.26) 6.67 19.99 73.34 2. PDT b 30 2.50 (0.28) 10.00 33.33 56.67 3. PDT + US b 30 2.77 (0.49) 13.34 39.99 46.67 * Different superscript lowercase letters indicate, in the column, statistically significant differences (p < 0.05). ** DW, distilled water; PDT, photodynamic therapy; US, ultrasonic activation. DISCUSSION One of the main expectation during the endodontic treatment is to provide the effective microbial reduction from the root canal system. However, due to the resistance of some microbial species, conventional chemical-mechanical preparation may not meet these expectations [ 1 ]. Considering the great reduction in instrumentation time with the use of rotary and reciprocating systems, the contact time of the auxiliary chemical substances with these microbial species also reduced, leading to a reduction in their antimicrobial properties [ 14 ]. Therefore, adjunctive therapies have been introduced into endodontic treatment, with the aim of complementing the antimicrobial action and enabling an effective reduction of microorganisms in the root canal system. In this scenario, PDT and US have presented satisfactory results, contributing to meet this proposal [ 2 , 3 , 4 ]. The conventional PDT protocol involves the insertion of the photosensitizer into the root canal and irradiation with a low-intensity laser. After PDT, irrigation of the root canal with an inert solution is recommended to remove the photosensitizer from the root canal walls. However, this protocol is not enough to promote effective removal of photosensitizer. It occurs because this photosensitizer adheres strongly to the root canal walls and acts as a chemical smear layer [ 5 ]. Its inadequate removal without the use of chelating agents results in the obliteration of dentinal tubules and decreases bond strength of filling and restorative materials to the root canal walls [ 6 , 7 ]. At the same time, the US of photosensitizer is recommended to improve the antimicrobial action of PDT [ 4 ]. Although this benefit, there is a possibility that US may contribute to an even greater impregnation of the photosensitizer on the root dentin. For these reason, the present study evaluated the effects of association of PDT and US on the bond strength of filling and restorative materials to root dentin. Bond strength corresponds to the force required to displace the filling or restorative material adhered to the root dentin. It is essential to maintain this mechanical property, ensuring adequate adhesion to the root canal walls, preventing marginal infiltration, reducing the risk of root fracture, and contributing to the longevity of the endodontically treated tooth [ 15 ]. Therefore, intracanal decontamination protocols performed prior to root canal filling or adhesive cementation of intraradicular posts should not interfere with dentin bond strength. It justifies the need for similar laboratory assays to this performed in the present study. The push-out test has been recommended over time to evaluate the bons strength. It consists of applying a force to the filling/restorative material through a cross-section of the root until this material is displaced. The displacement force is uniform and simulates clinical reality, it can be performed in different thirds of the root canal, it has high reproducibility, and provides a larger tested adhesion area when compared to other tests, such as microtensile and shear tests [ 13 , 16 ]. For these reasons, the push-out test was used in the present study to evaluate the bond strength of the tested materials. Considering that the ability of photosensitizer to impregnate root dentin may interfere with the adhesion of filling and restorative materials, the choice of endodontic sealer and adhesive cement for GFP plays a key role at this stage of endodontic treatment. Bio-C bioceramic sealer is bioactive and releases calcium ions, providing sealing ability through stable chemical bonding, tag-like penetration into the depth of dentinal tubules, and biomineralization stimulation [ 9 , 10 ]. In your turn, the Rely-X U200 self-adhesive resin cement provides recognized micromechanical and chemical retention to root dentin [ 17 ]. Due to these properties, these materials were tested in the present study after the root dentin was subjected to PDT protocols. According to results of present study, the groups 2 (PDT) and 3 (PDT + US) induced significant reduction on the bond strength of filling and restorative materials to root dentin. It confirms all hypotheses of present study. Similar results were found in previous studies, where the PDT protocol reduced the bond strength of epoxy resin-based sealer and calcium silicate-based sealer [ 6 ], as well as reduced the bond strength of GFB cemented with dual resin cement and self-adhesive resin cement to root dentin [ 7 ]. The use of DW is not enough to promote effective removal of the photosensitizer from the root canal walls. Instead, it is possible to observe by microscopy that this photsentizier is is strongly adhered to the root dentin after irrigation with DW, presenting penetration into the dentinal tubules and working as a chemical smear layer [ 5 ]. This condition prevents the penetration of root canal sealers and adhesive cements, helping to explain the results of present study [ 6 , 7 ]. Thus, maximizing the effectiveness of final irrigation protocols is necessary to remove the photosensitizer from root canal walls, providing ideal conditions for adhesion of filling and restorative materials in this environment. The use of 17% EDTA and US corresponds to an effective protocol in this proposal [ 6 , 7 ]. The US acts through the principle of hydrodynamic turbulence, increasing the temperature and hydrostatic pressure of the irrigant agent inserted into the root canal. Then, bubbles and cavitations are generated, and the irrigant agent is propelled more effectively against the root canal walls. It increases its cleaning potential and penetration into the depth of the dentinal tubules [ 18 ]. However, US of the PDT photosensitizer did not result in a more significant reduction in the bond strength of the tested filling and restorative materials when compared to the conventional PDT protocol without US. According to the previously described adhesion characteristics, bioceramic sealers present high bond strength results to root dentin [ 19 ]. Similarly, GFP cemented with self-adhesive resin cement has also demonstrated high adhesion to root dentin, given the optimization of its adhesive characteristics [ 20 ]. It may be possible reasons why no significant differences were found in the ability of groups 2 (PDT) and 3 (PDT + US) to influence bond strength in the present study. After the push-out test in both evaluations, it was possible to observe a higher predominance of cohesive failure in all groups of present study. It can be explained by the high adhesion provided by the tested bioceramic endodontic sealer and self-adhesive resin cement. The Bio-C bioceramic sealer releases calcium and hydroxyl ions, which react with dentin phosphate and form hydroxyapatite at the sealer-dentin interface. Hydroxyapatite crystals penetrate the dentinal tubules, creating micromechanical retention. Furthermore, bioceramic sealers exhibit volumetric expansion that fills microspaces and increases marginal adaptation [ 2 , 9 , 11 , 19 ]. On the other hand, Rely-X U200 self-adhesive resin cement releases acidic monomers that demineralize and infiltrate the dentin substrate, providing micromechanical retention. At the same time, the reaction between the phosphoric acid monomers of the cement and hydroxyapatite of the dentin substrate can offer chemical retention [ 17 , 20 ]. It is known that cohesive failure occurs within the filling or restorative material itself and not at the sealer-dentin or cement-dentin interface. It means that the tested materials present high adhesive strength to root dentin, which justifies the found results of failure pattern in the present study. The PDT is a complementary therapeutic modality to conventional chemo-mechanical preparation in endodontics, aiming to promote even more effective decontamination of the root canal system [ 2 ]. According to the literature, PDT can be optimized by US of the photosensitizer, yielding more effective results in reducing microorganisms within the root canals [ 4 ]. In your turn, the present study demonstrates that US of the PDT photosensitizer reduces the bond strength of the filling/restorative material to the root dentin. It is necessary to understand the extent to which intracanal decontamination protocols affect the dentin structure and the adhesion of the filling/restorative material to this previously decontaminated root dentin. Further studies are needed to assess the influence of the combination of PDT and US on the mechanical properties of root dentin, as well as to evaluate alternatives for effectively removing the photosensitizer adhered to the root canal walls. In this way, it will be possible to propose an auxiliary decontamination protocol with the understanding that the root dentin is preserved, contributing to the adequate sealing of the endodontically treated tooth. CONCLUSIONS Despite the limitations of the present study, it can be concluded that US of the PDT photosensitizer did not influence the bond strength of the filling and restorative material, when compared to conventional PDT without the US of the photosensitizer. However, the US of the PDT photosensitizer decreased the bond strength of the filling and restorative material to the root dentin. Declarations Conflict of Interest : All authors claim no conflicts of interest, no financial affiliation (e.g., employment, direct payment, stock holdings, retainers, consultantships, patent licensing arrangements, or honoraria) or involvement with any commercial organization with a direct financial interest in the subject or materials discussed in this manuscript, nor have any such arrangements existed in the past three years. Any other potential conflict of interest is disclosed. Ethical Approval : All applicable international, national, and/or institutional guidelines were followed. Informed consent : Not applicable. Funding: The work did not receive financial support. 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Microsc Res Tech 76:496–502 Creazzo G, de Barros Ciribelli Alves BM, de Assis HC, Villamayor KGG, de Sousa-Neto MD, Mazzi-Chaves JF, Lopes-Olhê FC (2025) Bond Strength and Adhesive Interface Quality of New Pre-Mixed Bioceramic Root Canal Sealer. Microsc Res Tech 88:1989–2000 Pinto C, França F, Basting RT, Turssi CP, Amaral F (2024) Evaluation of Bond Strength of Three Glass Fiber Post-systems Cemented to Large Root Canals. Oper Dent 49:222–230 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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. 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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-7643161","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":530851170,"identity":"0421b247-4285-49de-bdaa-c19bd68b685d","order_by":0,"name":"Alexia Trento","email":"","orcid":"","institution":"University of Passo Fundo","correspondingAuthor":false,"prefix":"","firstName":"Alexia","middleName":"","lastName":"Trento","suffix":""},{"id":530851173,"identity":"dcfc702b-5834-446d-ab13-a0394bf27728","order_by":1,"name":"Matheus Albino 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15:47:11","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":612054,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7643161/v1/53981a80-2775-48e1-80f9-6e4fdd62d6fe.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Influence of ultrasonic activation of the photodynamic therapy photosensitizer on the bond strength of gutta-percha/bioceramic sealer and fiberglass posts/self-adhesive cement","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eSome bacteria are resistant to conventional intra-canal managements. It creates conditions for proliferation, leading to the development of persistent infections in the root canal system [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Therefore, the use of auxiliary decontamination resources is mandatory in endodontic treatment. The photodynamic therapy (PDT) involves the ability of a photosensitizer to absorb light-energy and to react with oxygen, generating reactive oxygen species. As a consequence, this reactive oxygen adheres and penetrates the bacterial cell wall, precipitating the cytoplasmic content and inducing damage to the DNA of the bacterial cell [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. On the other hand, ultrasonic activation (US) has also contributed to greater decontamination, due to the increase in temperature and hydrostatic pressure of the irrigant agents which are used into the root canals [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAccording to Ghinzelli et al. [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], the use of US over the photosensitizer of PDT resulted in higher elimination of bacteria from the root canal space. Although this association presents significant aid in the decontamination process, this therapeutic modality can compromise the adhesion of filling and restorative materials to the root canal walls. The photosensitizers presents hydrophilic nature, low molecular weight, and high viscosity. It creates a chemical smear layer that adheres strongly to the canal walls and dentinal tubules [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], reducing the bond strength of filling and restorative materials [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. In addition, the US can induce greater impulse and impregnation of the photosensitizer to the canal walls, further compromising adhesion. However, there are no studies in the literature revealing the impact of the association of PDT and US on the bond strenght of new filling and restorative materials to the root canal walls.\u003c/p\u003e\u003cp\u003eRecent research in the field of endodontics has demonstrated scientific evidence for the use of bioceramic sealers as filling materials. Bioceramic sealers exhibit biocompatibility [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] and bioactivity [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. It releases hydroxyl ions, promoting an alkaline pH [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], capable of contributing to antimicrobial activity against persistent infections.4 Among other properties, it also demonstrates adequate bond strength to dentin, reducing the interface between the filling material and root canal walls [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. When the coronal portion presents extensive loss, the use of self-adhesive resin cement has been recommended to promote better bond strength of glass fiber posts (GFP) to the root dentin, resulting in effective polymerization and preservation of the bonding interface [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Considering the development of new decontamination protocols, as well as the diversity of alternatives for filling and restoration, it is essential to evaluate their relationship to provide support for their clinical use.\u003c/p\u003e\u003cp\u003eThus, the aim of present study is to evaluate the influence of US of the PDT photosensitizer on the bond strength of filling material composed by gutta-percha and bioceramic sealer, and restorative material composed by GFP and self-adhesive cement. The hypotheses of this study were that US of the PDT photosensitizer (i) decreases the bond strength of filling and (ii) restorative materials to root dentin.\u003c/p\u003e"},{"header":"MATERIAL AND METHODS","content":"\u003cp\u003eThis study was appreciated and approved by the local Ethics Commission.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eSample collection and preparation\u003c/h2\u003e\u003cp\u003eSixty hundred single-rooted extracted human teeth were used in the present study. All teeth were obtained from the Biobank of the School of Dentistry of the University of Passo Fundo (Passo Fundo, RS, Brazil). Dental crowns were sectioned with a rotary diamond disc (#911H, Brasseler, Savannah, GA, United States) so that all roots retained a length of 15 mm. The root length of 15 mm was measured with a ruler, a mark was made on each root in the measurement of 15 mm and the cut was performed at this length, standardizing the length of all roots.\u003c/p\u003e\u003cp\u003eAfter this, 30 roots were prepared by single operator, using the same protocol for pulp tissue removal and standardization of the root canal diameter. The working length (WL) was established by introducing a K-file #10 (Dentsply-Maillefer, Ballaigues, Switzerland) into the canal until its tip was visualized at the apical foramen. From this measurement, 1 mm was subtracted to obtain the WL. Each tooth was fixed in a portable lathe machine, in order to maintain the tooth secured during the root canal preparation. The roots were enlarged to WL using the ProTaper system (Dentsply- Maillefer), following the sequence S1 to F3. Distilled water (DW) (Natupharma, Passo Fundo, RS, Brazil) was used as irrigant solution and renewed at each instrument change. The ProTaper files (Dentsply-Maillefer) were used in a 16:1 gear reduction handpiece powered by a torque-controlled electric motor (X-Smart Plus - Dentsply-Maillefer, Ballaigues, Switzerland) at a constant rotation speed of 300 rpm in a crown-down manner according to the manufacturer\u0026rsquo;s instructions, by using a gentle in-and-out digital motion.\u003c/p\u003e\u003cp\u003eThe remaining 30 roots were flared at their coronal and middle thirds using Gates Glidden drills no. 2, 3 and 4 to a depth of 10 mm, to provide adequate space for cementation of GFP. The Gates Glidden drills were used in a low speed handpiece powered by micro electric motor at a constant rotation speed of 10.000 rpm in a crown-down manner, by using a gentle in-and-out digital motion.\u003c/p\u003e\u003cp\u003eAll root canals were then filled with 17% EDTA (Biodin\u0026acirc;mica, Ibipor\u0026atilde;, PR, Brazil), and all roots were put into 10 mL plastic vials containing 17% EDTA, such that there were ten samples per vial, so that the roots remained completely covered by the solution. Each plastic vial was inserted into an ultrasonic cleaning machine (Bio Free, Gnatus, Ribeir\u0026atilde;o Preto, SP, Brazil) for one minute in order to remove the smear layer formed by root canal preparation. After that, the root canals were irrigated with 5mL of DW and dried with absorbent paper points (Tanari, Manacapuru, AM, Brazil).\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eClassification of treatment protocols\u003c/h3\u003e\n\u003cp\u003eThe 60 specimens were embedded in epoxy resin (Silaex, S\u0026atilde;o Paulo, SP, Brazil), to facilitate PDT protocols and root canal filling. According to experimental tests, 30 specimens were used for evaluation of bond strength of filling material and the remaining 30 specimens were used for evaluation of bond strength of restorative material.\u003c/p\u003e\u003cp\u003eIn both evaluations, the 30 specimens were randomly divided in three groups (n\u0026thinsp;=\u0026thinsp;10):\u003c/p\u003e\u003cp\u003eG1 \u0026ndash; DW: the root canals were filled with DW until extravasation to the root canal entrance. The DW was retained in the root canal for 5 minutes. Then, all roots were irrigated with 5 mL of DW, followed by the aspiration of root canals.\u003c/p\u003e\u003cp\u003eG2 \u0026ndash; PDT: the root canals were filled with 0.01% (0.1 mg/mL) methylene blue (Chimio Lux DMC, S\u0026atilde;o Carlos, SP, Brazil) until extravasation to the root canal entrance. The photosensitizer was retained in the root canal for 5 min, as pre-irradiation time. After that, a low intensity laser (Therapy XT\u0026reg; DMC, S\u0026atilde;o Carlos, SP, Brazil) was used at 100mW power and continuous emission in the red part of the spectrum (660\u0026ndash;690 nm wavelength), with an intra-canal optical fiber of 600 \u0026micro;m diameter, attached at 2 mm short of the working length. The root canals were irradiated for 90 s, with 9 J of total dose delivery and 320 J/cm2 of energy density, remaining the intra-canal fiber in static position, as recommended by the manufacturer. Then, all roots were irrigated with 5 mL of DW, followed by the aspiration of root canals.\u003c/p\u003e\u003cp\u003eG3 \u0026ndash; PDT\u0026thinsp;+\u0026thinsp;US: the same procedure was performed as described in group 2. However, in the last minute of pre-irradiation time, the photosensitizer was activated by US. The US was performed using an ultrasonic device (Nac Plus ultrasonics \u0026mdash; Adiel, Ribeir\u0026atilde;o Preto, SP, Brazil), with a stainless-steel endodontic tip, which was inserted 2 mm short of the working length and activated for 1 min. The scale power 2 for endodontics was used to promote the US. Every effort was made to minimise contact of the tip with the root canal walls and promote the agitation of photosensitizer. Then, irrigation with 5 mL of distilled water was performed.\u003c/p\u003e\n\u003ch3\u003eRoot canal filling\u003c/h3\u003e\n\u003cp\u003eIn the first evaluation (bond strength of the filling material), the 10 specimens of each group were filled by the lateral compaction technique using gutta-percha points (Dentsply-Maillefer) and Bio-C bioceramic sealer (Angelus, Londrina, PR, Brazil). The sealer was applied along the root canal walls using the insertion point of bioceramic sealer. The gutta-percha ProTaper master cone #F3 (Dentsply-Maillefer) was lightly coated with the bioceramic sealer and inserted to the WL. Then, XF gutta-percha accessory points (Dentsply-Maillefe) were introduced into the root canals with the aid of finger spreaders (Dentsply Maillefer, Ballaigues, Switzerland). The gutta-percha accessory points were used until the finger spreader did not penetrate more than 5 millimeters into the root canal. Then, the excess of filling material was removed by cutting with a #2 heated plugger (SS White Duflex, Rio de Janeiro, RJ, Brazil). The root canal entrance was sealed with temporary restorative material (Vidrion R - SS White, Rio de Janeiro, RJ, Brazil).\u003c/p\u003e\u003cp\u003eIn the second evaluation (bond strength of the restorative material), the 10 specimens of each group were filled with GFP (Angelus, Londrina, PR, Brazil) and Rely-X U200 self-adhesive cement (3M ESPE, St. Paul, MN, USA). The GFP no. 1 (Angelus) was cleaned with 35% phosphoric acid for 30 s, rinsed for 30 s and gently air-dried. The silane application (3M ESPE) was performed for 1 min, followed by Single-Bond adhesive application (3M ESPE) and light polymerization for 40 s with a halogen light source with a power of 600 mV/cm\u003csup\u003e2\u003c/sup\u003e (Optilux, Demetron Res. Corp, Danbury CT, USA). The Single-Bond adhesive (3M ESPE) was applied in root dentin walls using microbrushes, air-dried for 5 s, and light polymerized for 40 s. Subsequently, Rely-X U200 self-adhesive cement (3M ESPE) was mixed and injected into the root canal of the 10 samples of each group with a suitable Centryx syringe and Acudosse needle (DFL, Rio de Janeiro, RJ, Brazil). The GFP was then covered with the same cement and positioned within the root canal at a 10 mm level, and held under digital pressure for 20 s. After this period, excess cement was removed. The cement was then polymerized using a 600 mW/cm\u003csup\u003e2\u003c/sup\u003e halogen light source (Optilux) for 30 s on each face (buccal, palatal, mesial, distal and occlusal).\u003c/p\u003e\u003cp\u003eAll procedures and parameters from this section were based in the manufacturer\u0026rsquo;s instruction.\u003c/p\u003e\n\u003ch3\u003eEvaluation on bond strength\u003c/h3\u003e\n\u003cp\u003eAfter the filling procedures, all specimens were stored at 37\u0026deg;C and 95% humidity for 21 days. Subsequently, the roots were sectioned transversely from the root canal entrance into 1 mm thick discs in a metallographic cutter with a diamond disk, at a speed of 350 rpm under cooling. The first disc was discarded, and the next five root discs were selected from each sample, totaling 50 specimens per subgroup (n\u0026thinsp;=\u0026thinsp;5\u0026times;10\u0026thinsp;=\u0026thinsp;50). Each disc was subjected to the push-out test on a mechanical testing machine (Emic DL 2000, S\u0026atilde;o Jos\u0026eacute; dos Pinhais, PR, Brazil) at a speed of 1 mm/min using a stainless steel cylindrical plunger of 0.8 mm dia- meter. The plunger tip was positioned so that it only contacted the filling material. The push-out force was applied in an apico-coronal direction until bond failure occurred, which was manifested by extrusion of the filling material and a sudden drop along the load deflection. The force required to displace the material from the root canal was recorded in Newtons (N) and calculated in megapascals (MPa).\u003c/p\u003e\u003cp\u003eAfter the push-out test, each disc was immediately transported in an Eppendorf tube containing DW to the optical microscope site, in order to calculate the bond strength and evaluate the failure patterns. Each disc was removed from the Eppendorf tube with a tweezer, dried with absorbent paper and positioned in the center of optical microscopy (Zeiss, S\u0026atilde;o Paulo, SP, Brazil), at 50\u0026times; magnification. The bond strength calculation and the failure pattern evaluation were based on a previous study by Dias et al [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The bond strength (δ) in megapascals was calculated using the formula δ\u0026thinsp;=\u0026thinsp;F/A, in which F is the force (N) used by the test machine and A is the area. To calculate the area, the following equation was applied: A\u0026thinsp;=\u0026thinsp;2πr \u0026times; h, in which π is the constant value 3.14, r is the radius of the intra-radicular space, and h is the height (mm). The radius of the intra-radicular space of each disc was measured under optical microscopy, with the aid of a software which provided this mensuration. The height of each disc was measured by using a digital pachymeter. Furthermore, the failure patterns were observed in each disc under optical microscopy (Zeiss, S\u0026atilde;o Paulo, SP, Brazil) at 50\u0026times; magnification. The classification was established as follows: 1: adhesive, between the dentin and the filling/restorative material, absence of filling/restorative material on the dentin walls of the root canal; 2: cohesive, failure of the filling/restorative material, presence of filling/restorative material on the dentin walls of the root canal; and 3: mixed, both failures (1 and 2) could be observed. All procedures and parameters from this section were based in previous study of Dias et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003eStatistical analysis\u003c/h2\u003e\u003cp\u003eThe normal distribution of results was confirmed by the Kolmogorov\u0026ndash;Smirnov test (p\u0026thinsp;=\u0026thinsp;0.4015). Bond strength was evaluated using a one-way analysis of variance (ANOVA), followed by the Tukey post-hoc test, enabling a quantitative analysis of these data. The failure mode distribution among the groups was evaluated using the chi-squared test, enabling a descriptive analysis of these data. All tests were set at a 5% level of significance. Data were analyzed using Stat Plus AnalystSoft Inc. version 6.0 (Vancouver, BC, Canada).\u003c/p\u003e\u003c/div\u003e"},{"header":"RESULTS","content":"\u003cp\u003eThe mean and standard deviation of bond strength of the filling and restorative material to the root canal dentin after tested protocols are presented in Tables\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, respectively. In both evaluations, the bond strength was significantly lower in groups 2 (PDT) and 3 (PDT\u0026thinsp;+\u0026thinsp;US) when compared to the control group (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), with no statistically significant difference between them (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). In addition, it was not revealed statistically significant differences in failure patterns among the groups (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05), with a higher predominance of cohesive failure in all groups.\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\u003eMean (standard deviation) of bond strength of filling material to root canal dentin (MPa) and percentage of pattern of failure (%) after tested protocols.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\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\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eGroup\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003en\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003ePush Out Bond Strength\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c6\" namest=\"c4\"\u003e\u003cp\u003eFailure mode\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eAdhesive\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eMixed\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eCohesive\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1. DW \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.93 (1.19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e33.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e63.34\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2. PDT \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.80 (0.73)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e30.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e70.00\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3. PDT\u0026thinsp;+\u0026thinsp;US \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.07 (0.86)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e33.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e56.67\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e\u003cp\u003e* Different superscript lowercase letters indicate, in the column, statistically significant differences (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e\u003cp\u003e** DW, distilled water; PDT, photodynamic therapy; US, ultrasonic activation.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\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\u003eMean (standard deviation) of bond strength of restorative material to root canal dentin (MPa) and percentage of pattern of failure (%) after tested protocols.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\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\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eGroup\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003en\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003ePush Out Bond Strength\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c6\" namest=\"c4\"\u003e\u003cp\u003eFailure mode\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eAdhesive\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eMixed\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eCohesive\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1. DW \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.62 (1.26)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e19.99\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e73.34\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2. PDT \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.50 (0.28)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e33.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e56.67\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3. PDT\u0026thinsp;+\u0026thinsp;US \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.77 (0.49)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e13.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e39.99\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e46.67\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e\u003cp\u003e* Different superscript lowercase letters indicate, in the column, statistically significant differences (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e\u003cp\u003e** DW, distilled water; PDT, photodynamic therapy; US, ultrasonic activation.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eOne of the main expectation during the endodontic treatment is to provide the effective microbial reduction from the root canal system. However, due to the resistance of some microbial species, conventional chemical-mechanical preparation may not meet these expectations [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Considering the great reduction in instrumentation time with the use of rotary and reciprocating systems, the contact time of the auxiliary chemical substances with these microbial species also reduced, leading to a reduction in their antimicrobial properties [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Therefore, adjunctive therapies have been introduced into endodontic treatment, with the aim of complementing the antimicrobial action and enabling an effective reduction of microorganisms in the root canal system. In this scenario, PDT and US have presented satisfactory results, contributing to meet this proposal [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe conventional PDT protocol involves the insertion of the photosensitizer into the root canal and irradiation with a low-intensity laser. After PDT, irrigation of the root canal with an inert solution is recommended to remove the photosensitizer from the root canal walls. However, this protocol is not enough to promote effective removal of photosensitizer. It occurs because this photosensitizer adheres strongly to the root canal walls and acts as a chemical smear layer [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Its inadequate removal without the use of chelating agents results in the obliteration of dentinal tubules and decreases bond strength of filling and restorative materials to the root canal walls [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. At the same time, the US of photosensitizer is recommended to improve the antimicrobial action of PDT [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Although this benefit, there is a possibility that US may contribute to an even greater impregnation of the photosensitizer on the root dentin. For these reason, the present study evaluated the effects of association of PDT and US on the bond strength of filling and restorative materials to root dentin.\u003c/p\u003e\u003cp\u003eBond strength corresponds to the force required to displace the filling or restorative material adhered to the root dentin. It is essential to maintain this mechanical property, ensuring adequate adhesion to the root canal walls, preventing marginal infiltration, reducing the risk of root fracture, and contributing to the longevity of the endodontically treated tooth [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Therefore, intracanal decontamination protocols performed prior to root canal filling or adhesive cementation of intraradicular posts should not interfere with dentin bond strength. It justifies the need for similar laboratory assays to this performed in the present study. The push-out test has been recommended over time to evaluate the bons strength. It consists of applying a force to the filling/restorative material through a cross-section of the root until this material is displaced. The displacement force is uniform and simulates clinical reality, it can be performed in different thirds of the root canal, it has high reproducibility, and provides a larger tested adhesion area when compared to other tests, such as microtensile and shear tests [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. For these reasons, the push-out test was used in the present study to evaluate the bond strength of the tested materials.\u003c/p\u003e\u003cp\u003eConsidering that the ability of photosensitizer to impregnate root dentin may interfere with the adhesion of filling and restorative materials, the choice of endodontic sealer and adhesive cement for GFP plays a key role at this stage of endodontic treatment. Bio-C bioceramic sealer is bioactive and releases calcium ions, providing sealing ability through stable chemical bonding, tag-like penetration into the depth of dentinal tubules, and biomineralization stimulation [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. In your turn, the Rely-X U200 self-adhesive resin cement provides recognized micromechanical and chemical retention to root dentin [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Due to these properties, these materials were tested in the present study after the root dentin was subjected to PDT protocols.\u003c/p\u003e\u003cp\u003eAccording to results of present study, the groups 2 (PDT) and 3 (PDT\u0026thinsp;+\u0026thinsp;US) induced significant reduction on the bond strength of filling and restorative materials to root dentin. It confirms all hypotheses of present study. Similar results were found in previous studies, where the PDT protocol reduced the bond strength of epoxy resin-based sealer and calcium silicate-based sealer [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], as well as reduced the bond strength of GFB cemented with dual resin cement and self-adhesive resin cement to root dentin [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The use of DW is not enough to promote effective removal of the photosensitizer from the root canal walls. Instead, it is possible to observe by microscopy that this photsentizier is\u003c/p\u003e\u003cp\u003eis strongly adhered to the root dentin after irrigation with DW, presenting penetration into the dentinal tubules and working as a chemical smear layer [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. This condition prevents the penetration of root canal sealers and adhesive cements, helping to explain the results of present study [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Thus, maximizing the effectiveness of final irrigation protocols is necessary to remove the photosensitizer from root canal walls, providing ideal conditions for adhesion of filling and restorative materials in this environment. The use of 17% EDTA and US corresponds to an effective protocol in this proposal [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe US acts through the principle of hydrodynamic turbulence, increasing the temperature and hydrostatic pressure of the irrigant agent inserted into the root canal. Then, bubbles and cavitations are generated, and the irrigant agent is propelled more effectively against the root canal walls. It increases its cleaning potential and penetration into the depth of the dentinal tubules [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. However, US of the PDT photosensitizer did not result in a more significant reduction in the bond strength of the tested filling and restorative materials when compared to the conventional PDT protocol without US. According to the previously described adhesion characteristics, bioceramic sealers present high bond strength results to root dentin [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Similarly, GFP cemented with self-adhesive resin cement has also demonstrated high adhesion to root dentin, given the optimization of its adhesive characteristics [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. It may be possible reasons why no significant differences were found in the ability of groups 2 (PDT) and 3 (PDT\u0026thinsp;+\u0026thinsp;US) to influence bond strength in the present study.\u003c/p\u003e\u003cp\u003eAfter the push-out test in both evaluations, it was possible to observe a higher predominance of cohesive failure in all groups of present study. It can be explained by the high adhesion provided by the tested bioceramic endodontic sealer and self-adhesive resin cement. The Bio-C bioceramic sealer releases calcium and hydroxyl ions, which react with dentin phosphate and form hydroxyapatite at the sealer-dentin interface. Hydroxyapatite crystals penetrate the dentinal tubules, creating micromechanical retention. Furthermore, bioceramic sealers exhibit volumetric expansion that fills microspaces and increases marginal adaptation [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. On the other hand, Rely-X U200 self-adhesive resin cement releases acidic monomers that demineralize and infiltrate the dentin substrate, providing micromechanical retention. At the same time, the reaction between the phosphoric acid monomers of the cement and hydroxyapatite of the dentin substrate can offer chemical retention [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. It is known that cohesive failure occurs within the filling or restorative material itself and not at the sealer-dentin or cement-dentin interface. It means that the tested materials present high adhesive strength to root dentin, which justifies the found results of failure pattern in the present study.\u003c/p\u003e\u003cp\u003eThe PDT is a complementary therapeutic modality to conventional chemo-mechanical preparation in endodontics, aiming to promote even more effective decontamination of the root canal system [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. According to the literature, PDT can be optimized by US of the photosensitizer, yielding more effective results in reducing microorganisms within the root canals [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. In your turn, the present study demonstrates that US of the PDT photosensitizer reduces the bond strength of the filling/restorative material to the root dentin. It is necessary to understand the extent to which intracanal decontamination protocols affect the dentin structure and the adhesion of the filling/restorative material to this previously decontaminated root dentin. Further studies are needed to assess the influence of the combination of PDT and US on the mechanical properties of root dentin, as well as to evaluate alternatives for effectively removing the photosensitizer adhered to the root canal walls. In this way, it will be possible to propose an auxiliary decontamination protocol with the understanding that the root dentin is preserved, contributing to the adequate sealing of the endodontically treated tooth.\u003c/p\u003e"},{"header":"CONCLUSIONS","content":"\u003cp\u003eDespite the limitations of the present study, it can be concluded that US of the PDT photosensitizer did not influence the bond strength of the filling and restorative material, when compared to conventional PDT without the US of the photosensitizer. However, the US of the PDT photosensitizer decreased the bond strength of the filling and restorative material to the root dentin.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eConflict of Interest\u003c/strong\u003e:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAll authors claim no conflicts of interest, no financial affiliation (e.g., employment, direct payment, stock holdings, retainers, consultantships, patent licensing arrangements, or honoraria) or involvement with any commercial organization with a direct financial interest in the subject or materials discussed in this manuscript, nor have any such arrangements existed in the past three years. Any other potential conflict of interest is disclosed.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cstrong\u003eEthical Approval\u003c/strong\u003e:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll applicable international, national, and/or institutional guidelines were followed.\u003c/p\u003e\n\u003ch2\u003e\u003cstrong\u003eInformed consent\u003c/strong\u003e:\u003c/h2\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003ch2\u003eFunding:\u003c/h2\u003e\n\u003cp\u003eThe work did not receive financial support.\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eAuthor credit statementM.A.S, J.D.C and Y.D.B contributed to conceptualization, methodology and original draft preparation; A.T., V.H.S.M, A.V.C.L., B.A.B., M.E.K., M.D. and K.E.B.M contributed to perform the methodology and all experimental tests;M.A.S, J.D.C and Y.D.B contributed to formal analysis.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eThammasitboon K, Teanpaisan R, Pahumunto N (2024) Prevalence and virulence factors of haemolytic Enterococcus faecalis isolated from root filled teeth associated with periradicular lesions: a laboratory investigation in Thailand. Int Endod J 57:769\u0026ndash;783\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eManoil D, Parga A, Hellesen C, Khawaji A, Brundin M, Durual S, \u0026Ouml;zenci V, Fang H, Belibasakis GN (2022) Photo-oxidative stress response and virulence traits are co-regulated in E. faecalis after antimicrobial photodynamic therapy. J Photochem Photobiol B 234:112547\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003evan der Sluis LW, Versluis M, Wu MK, Wesselink PR (2007) Passive ultrasonic irrigation of the root canal: a review of the literature. Int Endod J 40:415\u0026ndash;426\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGhinzelli GC, Souza MA, Cecchin D, Farina AP, de Figueiredo JA (2014) Influence of ultrasonic activation on photodynamic therapy over root canal system infected with Enterococcus faecalis\u0026ndash;an in vitro study. Photodiagnosis Photodyn Ther 11:472\u0026ndash;478\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSouza MA, Pazinatto B, Bischoff KF, Palhano HS, Cecchin D, de Figueiredo JAP (2017) Influence of ultrasonic activation over final irrigants in the removal of photosensitizer from root canal walls after photodynamic therapy. Photodiagnosis Photodyn Ther 17:216\u0026ndash;220\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSouza MA, Padilha Rauber MG, Zuchi N, Bonacina LV, Ricci R, Dias CT, Bischoff KF, Engelmann JL, Palhano HS (2019) Influence of final irrigation protocols and endodontic sealer on bond strength of root filling material with root dentin previously treated with photodynamic therapy. Photodiagnosis Photodyn Ther 26:137\u0026ndash;141\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSouza MA, Bonacina LV, Ricci R, Padilha Rauber MG, Zuchi N, Hoffmann IP, Bischoff KF, Engelmann JL, Palhano HS, Cecchin D (2019) Influence of final irrigation protocols and type of resin cement on bond strength of glass fiber posts in root dentin previously treated with photodynamic therapy. Photodiagnosis Photodyn Ther 26:224\u0026ndash;228\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSequeira DB, Seabra CM, Palma PJ, Cardoso AL, Pe\u0026ccedil;a J, Santos JM Effects of a new bioceramic material on human apical papilla cells. J Funct Biomater 201;9(4):74\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eInada RN, Queiroz MB, Lopes CS, Silva EC, Torres FF, Silva GF et al (2023) Biocompatibility, bioactive potential, porosity, and interface analysis calcium silicate repair cements in a dentin tube model. Clin Oral Investig 27:3839\u0026ndash;3853\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWang Z, Shen Y, Haapasalo M (2021) Antimicrobial and antibiofilm properties of bioceramic materials in endodontics. Mater (Basel) 14:7594\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVivan RR, Guerreiro-Tanomaru JM, Bosso-Martelo R, Costa BC, Duarte MA, Tanomaru-Filho M (2016) Push-out bond strength of root-end filling materials. Braz Dent J 27(3):332\u0026ndash;335\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSoares CJ, Pereira JC, Valdivia AD, Novais VR, Meneses MS (2012) Influence of resin cement and post configuration on bond strength to root dentine. Int Endod J 45:136\u0026ndash;145\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDias KC, Soares CJ, Steier L, Versiani MA, Rached-J\u0026uacute;nior FJ, P\u0026eacute;cora JD, Silva-Sousa YT, de Sousa-Neto MD (2014) Influence of drying protocol with isopropyl alcohol on the bond strength of resin-based sealers to the root dentin. J Endod 40:1454\u0026ndash;1458\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSouza MA, Tumelero Dias C, Zandon\u0026aacute; J, Paim Hoffmann I, Sanches Menchik VH, Palhano HS, Bertol CD, Rossato-Grando LG, Cecchin D, de Figueiredo JAP (2018) Antimicrobial activity of hypochlorite solutions and reciprocating instrumentation associated with photodynamic therapy on root canals infected with Enterococcus faecalis - An in vitro study. 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J Prosthet Dent 105:227\u0026ndash;235\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCastagna F, Rizzon P, Rosa RA, Santini MF, Barreto MS, Duarte MA, S\u0026oacute; MVR (2013) Effect of passive ultrasonic instrumentation as a final irrigation protocol on debris and smear layer removal\u0026ndash;a SEM analysis. Microsc Res Tech 76:496\u0026ndash;502\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCreazzo G, de Barros Ciribelli Alves BM, de Assis HC, Villamayor KGG, de Sousa-Neto MD, Mazzi-Chaves JF, Lopes-Olh\u0026ecirc; FC (2025) Bond Strength and Adhesive Interface Quality of New Pre-Mixed Bioceramic Root Canal Sealer. Microsc Res Tech 88:1989\u0026ndash;2000\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePinto C, Fran\u0026ccedil;a F, Basting RT, Turssi CP, Amaral F (2024) Evaluation of Bond Strength of Three Glass Fiber Post-systems Cemented to Large Root Canals. Oper Dent 49:222\u0026ndash;230\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"bioceramic sealer, bond strength, photodynamic therapy, photosensitizer, self-adhesive cement, ultrasonic activation","lastPublishedDoi":"10.21203/rs.3.rs-7643161/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7643161/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eIntroduction\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ethe role of endodontic treatment is to eliminate microorganisms without compromising adjacent tissues and adhesion. The aim of present study was to evaluate the influence of ultrasonic activation (US) of the photodynamic therapy (PDT) photosensitizer on the bond strength of filling and restorative material.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003esixty single-rooted teeth were used. After coronal sectioning, 30 roots were used to assess the bond strength of filling material and 30 to assess the bond strength of restorative material. After complete chemomechanical preparation, the roots were randomly divided into three groups in both evaluations (n = 10), according to PDT and US protocol: G1(negative control)–distilled water; G2–conventional PDT; G3–PDT + US. Then the roots were filled with gutta-percha/Bio-C bioceramic sealer in the first evaluation, and with fiber glass posts/Rely-X U200 self-adhesive cement in the second evaluation. In both evaluations, the roots were sectioned to obtain 1 mm thick dentin discs containing the filling/restorative material, and the push-out test was performed. Failure patterns were observed under optical microscope. Specific statistical analysis was performed in both evaluations (α 5%).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ein both evaluations, bond strength was significantly lower in groups 2(PDT) and 3(PDT + US) compared to control group (p \u0026lt; 0.05), with no statistically significant difference between them (p \u0026gt; 0.05). Regarding the failure patterns, no statistically significant difference was found between groups (p \u0026gt; 0.05), with a predominance of cohesive failure in all groups.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eUS of the PDT photosensitizer did not influence the bond strength of gutta-percha/bioceramic sealer and fiber glass posts/self-adhesive cement to root dentin when compared to conventional PDT.\u003c/p\u003e","manuscriptTitle":"Influence of ultrasonic activation of the photodynamic therapy photosensitizer on the bond strength of gutta-percha/bioceramic sealer and fiberglass posts/self-adhesive cement","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-17 13:46:27","doi":"10.21203/rs.3.rs-7643161/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"b895a67f-fbb9-4f6c-9c6d-ac1c5848b062","owner":[],"postedDate":"October 17th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-11-04T22:53:15+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-17 13:46:27","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7643161","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7643161","identity":"rs-7643161","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}