Study on shear strength and flexural strength of zirconia treated by hot acid etching

Study on shear strength and flexural strength of zirconia treated by hot acid etching | 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 Study on shear strength and flexural strength of zirconia treated by hot acid etching Xiaomin Yang, Huihui Tao, Yang Liu, Junju Mu, Zhuoran Liang, Yannan Zhang, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4794388/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 3 You are reading this latest preprint version Abstract In recent years, zirconia ceramics have been widely used as in prosthodontics because of their good aesthetics and mechanical properties. At present, the thermal acid etching technology for treating zirconia ceramics has gradually emerged as a new method. In this study, the effect of thermal acid etching surface treatment on the shear strength and flexural properties was investigated. In the fourth sentence, it might be clearer to specify that the zirconia ceramics were divided into five groups: "In the experiment, the zirconia ceramics were divided into five groups, each receiving a different treatment: blank, 110µm alumina sandblasting, 10-minute thermal acid etching, 30-minute thermal acid etching, and 60-minute thermal acid etching.The surface morphology, crystal structure, and the initial shear bonding strength of zirconia were analyzed by scanning electron microscope (SEM), X-ray diffractometer (XRD), and Instron3345 micro-force testing machine, respectively.SPSS19.0 software was used for the statistical analysis of experimental data, and the statistical difference was set as P < 0.05. The experimental results show that the thermal acid etching technology can effectively increase the surface roughness of zirconia and the shear bonding strength of zirconia and resin adhesive, the effect is obviously better than that of sandblasting, and there is no obvious correlation with the time of technology. This conclusion is of significant importance for guiding oral clinical treatment. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. Introduction With the development of the concept of minimally invasive oral cavity and the continuous innovation of new prosthodontic materials, public demand for oral medicine is not only the solution to dental pain and the recovery of chewing function. Aesthetic prosthodontics of the oral cavity has become a trend that is increasingly popular and widely accepted. In recent years, zirconia ceramics have gradually replaced metal PFM crowns in oral prosthodontics with their stable physical and chemical properties and aesthetic properties 1 and become a new prosthodontic material that can meet both functional and aesthetic requirements in clinical oral prosthodontics. In dental prosthodontics, the key to the successful clinical application of all-ceramic zirconia is the micromechanical and chemical retention formed by it and the resin cement adhesive. Therefore, forming a good bonding interface with the resin adhesive is important in ensuring the long-term application of zirconia repair in clinical practice 2 . Because zirconia ceramics do not contain glass matrix components, they are insoluble in strong acids and alkalis at room temperature, and their bonding strength is significantly lower than that of die-cast ceramics, which is difficult to meet the requirements of clinical repair on the bonding strength of materials 3 . Using aluminum oxide sandblasting surface of zirconium oxide is the common clinical way of roughening 2 . However, while improving the surface morphology of zirconia and increasing the roughness, it will cause the formation of surface micro-cracks, which increases the risk of micro-leakage between the zirconia and the resin adhesive; therefore, sandblasting cannot completely solve the problem of insufficient adhesion of all-ceramic zirconia. In recent years, zirconia ceramics treated by hot acid etching have become a new technology that is gradually being applied in the field of dental prosthesis. Hot acid etching is the use of high temperature heating strong acid acts on the surface of zirconia; the irregular high-energy atoms around zirconia are corroded and a large number of porous structures are formed on the surface to increase the roughness, which increases the effective area of the bonding, provided a more stable bonding strength for zirconia and resin adhesive, and thus enabled a satisfactory bonding strength of zirconia that meets the requirements of clinical application 4 , 5 . The ideal way of zirconium oxide surface treatment is to satisfy both the clinical bonding strength and mechanical properties of relatively stable. Hence, the purpose of this experiment is to explore the effect of hot acid etching surface treatment on the shear bonding strength and flexural properties of Cercon Zirconia, and to provide a basis for clinical selection of reasonable and effective surface treatment of zirconia. 2. MATERIALS AND METHODS 2.1. Specimen preparation Two kinds of zirconia samples of Cercon HT porcelain block (Dentsply, Germany) were prepared respectively. Type I specimens measured 25 mm × 8 mm × 1 mm, with 55 pieces each, while Type II specimens consisted of 25 pieces, each measuring 3 mm × 3 mm × 1 mm. Additionally, there were 5 pieces of die-cast ceramic specimens with specifications (IPS E. Max Press, Ivo Clara Viva Dent, Switzerland) measuring 3 mm × 3 mm × 1 mm. To maintain uniformity across all specimens, they were completed with water sandpaper of 180, 240, 360, 400, 600, 1000, 1200, and 2000 mesh. After grinding and polishing on the grinding machine, they were soaked in distilled water for 1 minute. Following this, they underwent ultrasonic washing in an ultrasonic cleaning machine for 30 minutes before being air-dried for use. 2.2. Selection of hot acid solution Hot acid etching is a process in which strong acid is heated to high temperatures and applied to the surface of zirconia. This action corrodes the irregular high-energy atoms surrounding the zirconia, forming numerous porous structures on its surface to increase roughness. This increase in roughness enhances the effective bonding area, providing a more stable bonding force for the adhesion of zirconia to resin materials 4 , 5 . In this experiment, concentrated hydrochloric acid served as the acidic medium, methanol acted as the solvent, and FeCl3 functioned as the oxidant to facilitate the zirconia etching reaction. To ensure the smooth progress of the hot acid etching reaction, methanol was employed as a solvent to maintain reaction pressure. Additionally, a constant temperature magnetic stirring bath was utilized to regulate temperature and control flow rate, thereby ensuring thorough reaction between the zirconia specimen and the hot acid etching solution 6 – 8 . The advantages of this method include conducting the reaction in a closed reactor, preventing methanol volatilization and consumption. Both methanol and ferric chloride can be reused, contributing to cost-effectiveness. Additionally, hydrochloric acid, as a low-cost corrosive agent, is utilized. The experimental equipment selected is relatively safe, with a reasonable risk coefficient. Furthermore, this study explores the impact of hot acid etching on the surface roughness of zirconia by varying the etching time. It aims to optimize and confirm whether etching time correlates positively with zirconia surface roughness, thereby providing an effective method for clinical zirconia treatment. 2.3. Preparation of hot acid etching solution 100 mL of hot acid etching solution requires 80 mL of methanol (Sinopharm Chemical Reagent Co., Ltd., China), 20 mL of 37% concentrated hydrochloric acid (Tianjin Kemeo Reagent Co., Ltd., China) and 0.2 g of ferric trichloride (Chemical Reagent Co., Ltd., China). The polished zirconia specimens were placed in a sealed reactor (Stainless steel reaction kettle with PTFE lining, Dalian Institute of Chemical Physics, Chinese Academy of Sciences) filled with hot acid etching solution. The reactor was placed in a heated constant temperature magnetic stirring oil bath pot (HWCL-3, Zhengzhou great wall science & trade co., ltd., China) (100℃), and a rotor inside the reactor (rotating speed 400r/min) was used to maintain uniform stirring of the hot acid etching solution 9 . 2.4. The experimental groups After grinding and polishing, Cercon zirconia specimens were randomly divided into 5 groups (n = 5) and treated as follows (Table 1 ). Table 1 Experimental grouping diagram (A1-E1 is altron zirconia, A2-E2 is cercon zirconia, F is die-casting ceramic) Group Treatment A1/A2 Blank B1/B2 Standblasting C1/C2 10 min hot acid etching D1/D2 30 min hot acid etching E1/E2 60 min hot acid etching F Hydrofluoric acid and silane coupling agent (Die-casting ceramic) Blank control of group A: Cercon zirconia specimens were polished without any other treatment . Sandblasting treatment of group B: At 0.4 Mpa pressure, 110 µm alumina particles were sandblasted at a distance of 10 mm from the surface of the Cercon zirconia specimen for each 20s (Twin-Pen Sandblaster, China). After sand blasting, the test pieces were washed in anhydrous ethanol for 15 min and dried for later use . Group C, D, E hot acid etching treatment: Cercon zirconia specimens were placed in a closed reactor with 30 mL hot acid etching solution (24 mL methanol, 6 mL concentrated hydrochloric acid, 0.06 g ferric chloride) heated to 100℃ for reaction of 10 min, 30 min, 60 min, respectively. After the reaction, they were washed in anhydrous ethanol for 15 min and dried for later use . Group F hydrofluoric acid group: the polished die-cast ceramics are etched with hydrofluoric acid for 60 s, rinsed under pressure with an air gun head for 20 s until no HF remains, then rinsed with absolute ethanol for 5 minutes, and then blow-dried, set aside and coated with silane coupling agent for 2 min before bonding. 2.5. Collection and treatment of isolated teeth Upper and lower anterior teeth as well as premolars extracted due to periodontitis or orthodontic reasons were collected, following specific criteria: no defects or caries on the lips of the crown; no bad mineralization and fluoride spots on enamel surface; no root canal treatment; no obvious crack on the lip of tooth crown.The collected isolated teeth were decapitated along the enamel-cementum boundary, placed in normal saline, and stored in cold storage at 4°C for future use. A plane of at least 3 mm × 3 mm was prepared on the labial or buccal surface of the isolated teeth using an emery car needle. The thickness was maintained at ≤ 1 mm to preserve the adhesive interface within the enamel layer. After ultrasonic vibration for 5 minutes, the teeth were stored in distilled water. All procedures were performed by a single operator. 2.6. Structure characterization One type I Cercon zirconia specimen with different surface treatments was randomly selected and put into a vacuum ion plating machine (EIKO, IB3 Japan) for gold spraying treatment. The specimen sprayed with gold was placed on the stage of scanning electron microscope (Carl Zeiss, Supra 55 sapphire, Germany), and the surface morphology of zirconia was observed with magnification of 5000 times. Then, one type I zirconia specimen with different surface treatments was randomly selected for X-ray diffraction Radiometer (panaco, Empyrean X, the Netherlands) to detect the crystal structure of the surface. The scanning target was copper, the scanning speed was 0.02°/min, and the scanning Angle was 20°-70°.The X-ray diffraction pattern of each specimen was used to analyze whether there was crystal phase transition. 2.7. Choice of adhesive The adhesive utilized in this experiment is Panavia F. As a self-etching resin adhesive, it offers advantages over glass ionomer adhesives, polycarboxylic acid cement adhesives, and resin-reinforced glass ionomer adhesives. Notably, Panavia F exhibits high strength and its color meets aesthetic requirements. These qualities contribute to enhanced edge sealing of all-porcelain restorations and reduce microleakage along the restoration edges 10 , thus forming a good bonding effect on the surface of zirconia and enamel. While the total acid etched resin adhesive requires the use of phosphoric acid and pretreatment agent in advance to treat the tooth surface, with high sensitivity of operation technology and uncertain human factors, so the self-etched adhesive with relatively low sensitivity of operation was selected in this experiment. However, the technology of self-adhesive resin adhesive is less sensitive and more convenient to operate. Therefore, how to choose resin adhesive is also a very important factor affecting whether zirconia can form effective bonding with tooth surface at present. Resin adhesives can be categorized based on their components, namely adhesives containing 10-MDP and those without it. Panavia F adhesives belong to the former category as they contain 10-MDP. Souza et al. suggested that resin adhesives or undercoatings containing 10-MDP could effectively enhance the initial bonding strength of zirconia surfaces 11 . The effective bonding between zirconia and enamel relies on both mechanical and chemical retention mechanisms. Mechanical retention is achieved through surface roughening via sandblasting or hot acid etching, while chemical retention is facilitated by the presence of 10-MDP.The functional phosphoric acid groups of 10-MDP react with oxygen atoms on the zirconium oxide surface, forming chemical covalent bonds. Additionally, 10-MDP undergoes olefinic bond and condensation reactions with the resin cement matrix. These processes effectively bind the zirconia and resin together. Therefore, resin adhesive containing 10-MDP is considered the preferred bonding material for zirconia 12 . In conclusion, Panavia F, a self-etching adhesive containing 10-MDP, was chosen for investigation in this experiment. However, as this study only examined the initial bonding strength of Panavia F, further extensive research is necessary to evaluate the bonding strength and long-term durability of adhesives with various types and components. Such studies can offer valuable references and guidance for the clinical application of adhesives. 2.8. Shear test design (Fig. 1 ) ISO 11405 does not specify the size of the bonding area for shear test specimens but emphasizes considering its impact on bonding strength. The standard mandates applying a force of 10 N vertically to the bonding surface for 10 seconds during the bonding process. Consequently, all specimens in this shear test were set to a size of 3 mm × 3 mm × 1 mm. For uniform loading during shear force application and to avoid experimental errors from biaxial or torsional forces, a plane loading head was chosen. Placido's study indicated that positioning the load 1 mm away from the bonding interface minimizes stress 13 . Additionally, different loading speeds influence shear strength and fracture modes; hence, a loading speed of 0.5 mm/min was maintained based on the bonding interface's fracture mode 14 .Furthermore, adhesive residue removal is crucial to prevent experimental errors. Thus, during the experiment, adhesives were thoroughly removed without touching the zirconia or die-cast ceramic specimens. 2.9. Mechanical properties measurement The isolated teeth, each with 1 mm thickness of enamel uniformly ground, were embedded in self-coagulated resin, exposing the enamel bonding surface. Excess resin material at the edges was removed with a mixing knife to ensure full exposure of the enamel bonding surface, aligned completely parallel to the loading interface. After the self-coagulating resin completely hardened, the test specimen was removed. Strict adherence to Panavia F adhesive (Panavia F, Kolili, Japan) requirements was observed during tooth treatment and bonding with Type II zirconia and die-casting ceramic specimens. The enamel bonding interface was initially etched with 35% phosphoric acid for 30 seconds, followed by rinsing with air gun pressure for 15 seconds and blow-drying for 30 seconds. A mixture of Panavia F A and B solutions was evenly applied to the enamel bonding surface with a small brush for 30 seconds. Compound resin Paste A and Paste B were mixed evenly on a mixing plate and then applied to the bonding surface of zirconia and die-casting ceramic specimens. The completed adhesive specimens were secured in an Instron 3345 micro-force tester (Instron, America), subjected to a vertical loading pressure of 10 N for 10 seconds to ensure perpendicular loading direction to the bonding interface. Excess adhesive at the specimen edges was removed, followed by edge sealing and curing with a light curing lamp for 20 seconds. The specimens were then placed in a 37°C water bath for 24 hours. Subsequently, the completed zirconia and die-casting ceramic bonding specimens were positioned on the Instron 3345 micro-force tester, and a loading speed of 0.5 mm/min was set. The loading head, kept parallel to the bonding surface and at a distance of 1 mm from the bonding interface, uniformly loaded the specimens until detachment. The maximum load value (F) at the fracture moment was recorded by the Instron 3345 micro-force tester, and the shear strength was calculated. Observation of the shear fracture interface was conducted under a stereoscopic microscope (NOVEL, Yongxin, Jiangnan, Nanjing, China) at 20x magnification. The fracture interface was classified into zirconia and resin bonding interface fracture, resin cohesion fracture, and tooth enamel and resin bonding interface fracture. The Instron 3345 micro-force tester was utilized to assess the three-point bending strength of Type I zirconia specimens following various surface treatments (refer to Fig. 2 ). The span was set at 20 mm, with a loading speed of 0.5 mm/min, and the specimens were loaded until fracture occurred. The Instron 3345 micro-force tester recorded the maximum load value at the moment of fracture, allowing for calculation of the three-point bending strength.. Figure Note: In the above figures, T is the diffraction peak of tetracrystal phase, 2θ is the diffraction angle on the horizontal axis, and the diffraction peak and peak intensity on the vertical axis. 2.10. Statistical analysis The results of shear bonding strength and three-point bending strength were analyzed using the single-factor analysis method and T-test method available in SPSS 19.0 statistical software. A statistical significance threshold of P < 0.05 was set. XRD results were analyzed using MDI Jade 6 software and Origin 2019 software. 3. RESULTS 3.1. Microstructure and crystal structure E show the scanning electron microscope images of the blank control, 110 µm alumina sandblasting, 10 min hot acid etching, 30 min hot acid etching and 60 min hot acid etching at 5000 times of Cercon zirconia (Fig. 3 ). As shown in the Fig. 3 , the scanning electron microscope results of Cercon zirconia in the blank control group showed smooth surface, regular and dense grain structure arrangement, and no cracks and pits. The surface structure of Cercon zirconia in 110 µm alumina blasting group showed a strip-shaped pit structure without obvious cracks. The zirconia surface morphology of the hot acid etching group at 10 min, 30 min and 60 min was basically the same, and no obvious difference was observed. According to the figure, the surface of Cercon zirconia after the hot acid etching treatment presented three-dimensional pore structure with grain width enlargement. The results show that the surface roughness of Cercon zirconia is increased by sandblasting and hot acid etching to different degrees, and the hot acid etching effect is more significant. Figure Note: In the above figures, T is the diffraction peak of tetracrystal phase, 2θ is the diffraction angle on the horizontal axis, and the diffraction peak and peak intensity on the vertical axis. 3.2. Shear bonding strength The value of shear strength of each group is5.47 ± 1.33 MPa in A group, 8.22 ± 2.40 MPa in B group, 10.89 ± 1.43 MPa in C group, 11.09 ± 2.39 MPa in D group, 11.02 ± 2.39 MPa in E group (Fig. 4 ). There is no statistical significance between groups C, D and E (p > 0.05), but there is statistical significance between group A and group B, C, D and E, and between group B and C, D and E (p < 0.05). The shear strength of die-cast ceramics in Group F is 27.33 ± 2.67 MPa, which is statistically different from that of zirconia in this experiment (P < 0.05). Figure note: A-E represents the shear strength of the blank control, 110 µm alumina blasting, thermal etching, 10 min hot acid etching, 30 min hot acid etching and 60 min hot acid etching of Altron and Cercon zirconia, and F represents the shear strength of the die-casting ceramics. The upper and lower short lines are the highest and lowest values of shear strength of each group, the upper and lower bounds of the column are the upper and lower quartile, the bold line is the median, and the marked values at the top of the graph are the mean and standard deviation. All groups of zirconia fracture interfaces were observed using an optical microscope, focusing on the zirconia and resin bonding interface. A very small number of mixed fractures were observed, with most of the fracture interfaces exhibiting cohesive fractures. In contrast, the fracture interfaces of die-casting ceramics predominantly showed mixed cohesive fractures (Table 2 ). Table 2 Adhesive section results of each group Group Zirconia resin bonding interface fracture Mixed fracture Tooth enamel resin bonding interface A1 5 0 0 A2 5 0 0 B1 5 0 0 B2 C1 C2 D1 D2 E1 E2 F 5 5 5 5 5 5 5 1 0 0 0 0 0 1 0 4 0 0 0 0 0 0 0 0 3.3. Three-point bending strength The three-point bending strength values of each group is 1684.2 ± 123.2 MPa in A group, 1492.8 ± 110.1 MPa in B group, 1337.2 ± 57.7 MPa in C group, 1292.8 ± 118.7 MPa in D group, 1241.2 ± 144.2 MPa in E group (Fig. 5 ). There was no statistical significance between groups C, D and E (P > 0.05), but there was statistical significance between group A and other groups (P < 0.05), and between group B and other groups (P < 0.05). Figure note: A-E represents the three-point bending strength of the blank control, 110 µm alumina blasting, thermal etching, 10 min hot acid etching, 30 min hot acid etching and 60 min hot acid etching of Altron and Cercon zirconia. The upper and lower short lines are the highest and lowest values of three-point bending strength of each group, the upper and lower bounds of the column are the upper and lower quartile, the bold line is the median, and the marked values at the top of the graph are the mean and standard deviation. 4. DISCUSSIONS Microstructure and crystal structure The scanning electron microscope (SEM) results revealed notable changes in the surface morphology of zirconia treated by different methods compared to the blank control group. The roughness of the treated zirconia surfaces was significantly increased compared to untreated zirconia. In the blank control group, the surfaces of Cercon zirconia appeared relatively smooth, with a dense grain arrangement, slight polishing scratches, and no evident cracks. However, in the zirconia sandblasting group, striated pit-like structures were observed on the surface. Sato et al. suggested that sandblasting treatment may induce the formation of micro-cracks on the surface of zirconia, potentially diminishing its mechanical properties 15 . However, no obvious signs of microcracks were observed on the surface of zirconia in the sandblasting group in this experiment. This observation could be attributed to the specific sandblasting parameters selected for this study. The experiment was conducted using parameters referenced from Li Xin et al 16 , suggesting that the conclusion drawn from this experiment aligns closely with their findings. After undergoing different hot acid etching time treatments, the surface of Cercon zirconia exhibited widened grain boundaries, irregular grain arrangement, increased porosity, and enhanced roughness. However, no defects or microcrack formations were observed. This phenomenon aligns with the findings of Javid et al., who suggest that hot acid etching solution may induce the rupture of the protective zirconia film, leading to localized corrosion phenomena. Consequently, this process results in the expansion of grain boundary spaces and the formation of micropores 17 . Similarly, Wegner et al. demonstrated that the hot acid etching solution has the capability to dissolve the grain structure present on the zirconia surface. This dissolution process leads to the expansion of grain boundaries, ultimately resulting in the formation of a deep three-dimensional porous structure on the surface of the zirconia 4 , 5 , 18 .The results of this experiment align with previous findings. Interestingly, the SEM images revealed that the surface roughness of zirconia did not significantly change with the extension of thermal etching time; it remained relatively constant. This observation corresponds with the research conducted by Casucci, who subjected Lava to hot acid etching for varying durations (10 min, 30 min, and 60 min) and found that the roughening effect on zirconia surfaces was independent of the reaction time. This consistency between studies suggests that hot acid etching effectively roughens the zirconia surface, regardless of the etching duration. Current literature supports the notion that hot acid etching is an effective method for increasing the surface roughness of zirconia, with minimal reports of microcrack generation. However, further exploration is warranted to understand the long-term stability and fatigue resistance of zirconia. Figure 6 illustrates the X-ray diffraction analysis results of the Cercon zirconia ceramic specimens in groups A-E. Upon reference to the standard PDF card (card number 50-1089/37-1484) provided by the International Diffraction Data Center, it becomes evident that the main diffraction peak positions of the spectra from each group are consistent with the standard diffraction peak positions of tetragonal zirconia. Analysis of the X-ray diffraction line spectra indicates that the tetragonal phase is the predominant crystal structure of the zirconia ceramics examined. Notably, no monoclinic diffraction peaks were observed in either the blank group or the zirconia group treated by different surface methods. This observation leads to speculation that there may be no transformation from the tetragonal to monoclinic crystal phase (Fig. 6). X-ray diffraction is a technique used to study the composition and crystal structure of materials. By irradiating crystals with X-rays, diffraction patterns are produced at specific angles, which can then be analyzed to determine the type of crystals present in the material 19 , 20 . The zirconia utilized in this experiment is yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). According to the PDF card 50-1089 calibrated by the international organization 'Joint Committee on Powder Diffraction Standards,' the corresponding peak angle of the tetragonal crystal phase of zirconia is typically around 30°. It's noted that after various surface treatments, there is a possibility of the unstable monoclinic crystal phase appearing. Research conducted by Lv Pin indicates that the amount of untreated zirconia and the presence of the monoclinic crystal phase after hot acid etching are minimal and negligible. However, sandblasting treatment may result in a significant presence of monoclinic phase components on the surface of zirconia 21 . However, the research results of Jiao Yang et al. revealed that the volume fraction of the monoclinic crystal phase in zirconia after hot acid etching treatment was higher compared to that after sandblasting. Specifically, the volume fractions were reported as 17.81% and 12.50%, respectively 22 . According to the analysis of zirconia XRD results in this experiment, characteristic peaks corresponding to the tetragonal crystal phase were observed in all samples, while no characteristic peaks indicative of the monoclinic crystal phase were detected. However, due to the limited literature in this field and the absence of definitive conclusions, the results of this experiment alone are insufficient to prove the transformation of zirconia's tetragonal crystal phase to the monoclinic phase following different surface treatments. To establish a clearer conclusion, further investigation is warranted, possibly by refining the detection method. Shear bonding strength According to the analysis of shear results, there was A statistical difference in shear strength between the blank control group of group A and the sandblasting group B (P < 0.05), the shear strength of sandblasting group B and hot acid etched group C, D and E were statistically different (P 0.05). The results indicate that both sandblasting and hot etching can effectively increase the shear bonding strength of Zirconia and resin adhesive, and the hot etching increases the shear bonding strength more significantly, and has no obvious correlation with the reaction time of hot etching. Casucci's study showed that the bonding strength of Lava zirconia treated by hot acid etching was significantly higher than that of sand-blasted zirconia and zirconia without any treatment, which was independent of the reaction time 7 . Combined with the results of scanning electron microscope, it can be seen that the surface of zirconia can be observed strip pit structure after sandblasting, however, after hot acid etching, a large area of acid etching can be seen, and the zirconia grain boundary can be seen to be broadened by the amplification power, and a large number of pore structures can be seen on the surface. Therefore, the experimental results are consistent with these results. The shear experimental results reveal that the shear strength value of group F was 27.33 ± 2.67 MPa, significantly higher than that of zirconia and holds substantial significance (P < 0.05). Puppin-Rontani et al. investigated the impact of hydrofluoric acid concentration and etching duration on the bonding strength of lithium silicate glass ceramics, achieving a bonding strength of 32.9 ± 2.2 MPa with 10% HF 23 . Similarly, Chao Chen's research reached a comparable conclusion, reporting an adhesive force of 31.3 ± 2.9 MPa for glass ceramics etched with HF acid 24 . The findings of this experiment align closely with these studies. Based on the experimental results, zirconia treated by sandblasting or hot acid etching still exhibits a disparity in shear strength compared to glass ceramics with more established surface treatment technologies. The die-cast ceramic block is classified as a type of glass ceramics. Glass ceramics typically consist of components such as feldspar, leucite, and lithium disilicate. These materials can be effectively etched by hydrofluoric acid to achieve a desirable surface roughness. Hydrofluoric acid is widely recognized as the optimal surface treatment agent for glass ceramics 25 . Hydrofluoric acid operates by selectively reacting with the silicate components present in glass ceramics 26 , 27 , thereby disrupting the Si-O bonds. This reaction results in the formation of fluorosilicate compounds and exposes the crystal structure of lithium disilicate. Consequently, a rough network structure is created on the surface of the glass ceramics 28 , 29 , which enhances the wettability and alters the surface energy of the material. The bonding characteristics between glass ceramics and resin adhesives rely on the presence of silica on the glass ceramic surface. Silica facilitates chemical compatibility by utilizing a silane coupling agent to achieve optimal bonding properties 30 . One end of the silane molecule features an organic functional group capable of polymerizing with the organic constituents of the resin adhesive. The other end contains an alkoxy group that reacts with the hydroxyl groups on the glass ceramic surface. This dual functionality enables the silane coupling agent to serve as an effective intermediary, promoting sufficient bonding strength between the glass ceramic and resin adhesive 31 . Unlike glass ceramics, zirconia ceramics lack a glass matrix component, rendering them unsuitable for hydrofluoric acid treatment 32 . Consequently, silane coupling agents are unable to synergistically enhance the bonding properties of zirconia ceramics. The experimental findings demonstrate that while hot etching treatment can increase the surface roughness and bonding strength of zirconia with resin, there remains a significant disparity in bonding strength between zirconia and glass ceramics. Further exploration and refinement of surface treatment methods are necessary to achieve simplicity of operation and outstanding results. Three-point bending strength According to the results of the three-point bending test, the flexural strength of Cercon zirconia decreases to varying degrees after sandblasting and hot acid etching treatments, with the hot acid etching group showing a more pronounced decrease. Several factors influence the flexural strength of zirconia, including both internal and external factors. Internal factors encompass aspects such as zirconia's processing techniques and raw material composition. On the other hand, external factors leading to the reduction in zirconia's flexural strength may include crystal phase transformation, loss of surface grain structure, and the generation of microcracks following zirconia surface treatment 33 . Sandblasting increases surface roughness, but it also escalates the risk of microcrack formation and loss of surface structure in zirconia. Research suggests that the size of sandblasting particles correlates with microcrack formation, and larger particles can lead to more significant surface loss. The 110µm sandblasting particles used in this experiment may mitigate the occurrence of microcracks and surface loss to some extent 34 , but the inherent risks associated with sandblasting cannot be entirely eliminated. Regarding the decrease in flexural strength due to hot acid etching, most scholars attribute it to crystal phase transformation. Wang Ji-de et al. demonstrated that hot acid etching treatment induces more crystal phase transitions in zirconia 35 . However, in this experiment, no crystal phase transitions were observed through X-ray diffraction analysis. According to the experimental results of three-point bending strength, there isn't a significant decrease in bending strength with the extension of hot etching time. The experimental investigation on roughness confirms that the surface roughness of zirconia remains unaffected by the etching time, suggesting that this outcome is associated with the inherent structure of zirconia material itself. 5. CONCLUSION 1. Hot acid etching increased the surface roughness of Cercon zirconia, but the increase of surface roughness of zirconia had no correlation with the hot acid etching time. 2. Hot acid etching increased the shear bonding strength of Cercon zirconia, but it is still significantly lower than that of die-casting ceramics and is independent of the hot acid etching time. 3. After hot acid etching treatment, the flexure strength of Cercon zirconia decreased to different degrees. 4. The grain structure of Cercon zirconia after hot acid etching treatment showed no apparent transformation from tetracrystalline phase to monoclinous phase, so it is speculated that the physical and chemical properties of Cercon Zirconia after hot acid etching treatment are relatively stable. Declarations CLINICAL RELEVANCE STATEMENT To solve the clinical problem of insufficient bonding strength of zirconia, we evaluate the bonding performance of zirconia ceramics after thermal etching.This conclusion has an important guiding role for the clinical application of zirconia ceramics. Author Contribution Methodology and writing- original draft, XY; Investigation, writing and formal analysis,HT; Conceptualization, review and editing, YL and HT; Writing and editing, JM and ZL; Investigation and editing YZ; Resources, ML; Writing, FM; Methodology and supervision, ZC; Methodology, resources and supervision, JC; All authors have read and agreed to the published version of the manuscript. DATA AVAILABILITY STATEMENT The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author. References Chen, D., Wang, N., Gao, Y., Shao, L. q., Deng, B.. (2014). A 3-dimensional finite element analysis of the restoration of the maxillary canine with a complex zirconia post system. Prosthet Dent. 112(6), 1406–15. doi: 10.1016/j.prosdent.2014.05.017 Miyazaki, T., Nakamura, T., Matsumura, H., Ban, S., Kobayashi, T.. (2013). Current status of zirconia restoration. 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(2022). in vitroComparative evaluation of bond strength of resin cements with and without 10-methacryloyloxydecyl dihydrogen phosphate (mdp) to zirconia and effect of thermocycling on bond strength - An study. J Clin Exp Dent. 14(4), e316-e320. doi: 10.4317/jced.59324 Blatz, M. B., Sadan, A., Kern, M.. (2003). Resin-ceramic bonding: a review of the literature. J Prosthet Dent. 89(3), 268–74. doi: 10.1067/mpr.2003.50 Placido, E., Meira, J.B.C., Lima, R.G., Muench, A., et al. (2007). Shear versus micro-shear bond strength test: a finite element stress analysis. Dent Mater. 23(9), 1086–92. doi: 10.1016/j.dental.2006.10.002 Lindemuth, J.S., Hagge, M.S.. (2000). Effect of universal testing machine crosshead speed on the shear bond strength and bonding failure mode of composite resin to enamel and dentin. Mil Med. 165(10), 742–6. doi: 10.1093/milmed/165.10.742 Sato, H., Yamada, K., Pezzotti, G., Nawa, M., Ban, S.. (2008). Mechanical properties of dental zirconia ceramics changed with sandblasting and heat treatment. Dent Mater J. 27(3), 408–14. doi: 10.4012/dmj.27.408 Su, N., Yue, L., Liao, Y., Liu, W., Zhang, H., Li, X., Wang, H., Shen, J.. (2015). The effect of various sandblasting conditions on surface changes of dental zirconia and shear bond strength between zirconia core and indirect composite resin. J Adv Prosthodont. 7(3), 214–23. doi: 10.4047/jap.2015.7.3.214 Ye, S., Chuang, S.F., Hou, S.S., Lin, J.C., Kang, L.L., Chen, Y.C.. (2022). Interaction of silane with 10-MDP on affecting surface chemistry and resin bonding of zirconia. Dent Mater. 38(4), 715–724. doi: 10.1016/j.dental.2022.02.014 Aboushelib, M.N., Kleverlaan, C.J., Feilzer, A.J.. (2007). Selective infiltration-etching technique for a strong and durable bond of resin cements to zirconia-based materials. J Prosthet Dent. 98, 379–88. Aboushelib, M.N., Kleverlaan, C.J., Feilzer, A.J.. (2008). Microtensile bond strength of different components of core veneered all-ceramic restorations. Part 3: double veneer technique. J Prosthodont. 17(1), 9–13. doi: 10.1111/j.1532-849X.2007.00244.x Guang, H., Xie, H., Song, X., Liu, F., Chen, C., Zhang, F.. (2013). Effect of Zirconia Core Porcelain Treatment and Finishing Porcelain Process on Bonding Strength of Porcelain/Porcelain. Journal of Nanjing Medical University (Natural Science Edition). 33(08), 1161–1166. Jin, C., Wang, J., Huang, Y., Yu, P., Xiong, Y., Yu, H., Gao, S.. (2022). Effects of Hydrofluoric Acid Concentration and Etching Time on the Bond Strength to Ceramic-coated Zirconia. J Adhes Dent. 24(1), 125–136. doi: 10.3290/j.jad.b2838165 Jiao, Y., Wang, J.D., Deng, J.P.. (2018). Effect of different surface treatments on the crystal structure and properties of zirconia. Beijing Da Xue Xue Bao Yi Xue Ban. 50(1), 49–52. Puppin, R.J., Sundfeld, D., Costa, A.R., Correr, A.B., Puppin, R.R.M., Borges, G.A., Sinhoreti, M., Correr, S.L.. (2017). Effect of Hydrofluoric Acid Concentration and Etching Time on Bond Strength to Lithium Disilicate Glass Ceramic. Oper Dent. 42(6), 606–615. doi: 10.2341/16-215-L CHEN, C., JIANG, T.. (2011). Effect of Surface Melting Glass Ceramics on the AdHESion Strength of Zirconia to Resin. Chinese Journal of Stomatology. 46 (Z1), 99–103. Matinlinna, J.P., Vallittu, P.K.. (2007). Bonding of resin composites to etchable ceramic surfaces - an insight review of the chemical aspects on surface conditioning. J Oral Rehabil. 34(8), 622–30. doi: 10.1111/j.1365-2842.2005.01569.x Kermanshah, H., Torkamani, M.J., Ranjkesh, B., Bahrami, G., Farahmandpour, N.. (2021). Effect of different surface treatments of presintered or sintered zirconia on bond strength to dentine. J Conserv Dent. 24(6), 599–605. doi: 10.4103/jcd.jcd_249_21 Yen, T.W., Blackman, R.B., Baez, R.J.. (1993). Effect of acid etching on the flexural strength of a feldspathic porcelain and a castable glass ceramic. J Prosthet Dent. 70, 224–33. Della, B.A., Shen, C., Anusavice, K.J.. (2004). Work of adhesion of resin on treated lithia disilicate-based ceramic. Dent Mater. 20(4), 338–44. doi: 10.1016/S0109-5641(03)00126-X Zogheib, L.V., Bona, A.D., Kimpara, E.T., McCabe, J.F.. (2011). Effect of hydrofluoric acid etching duration on the roughness and flexural strength of a lithium disilicate-based glass ceramic. Braz Dent J. 22(1), 45–50. doi: 10.1590/s0103-64402011000100008 Ozcan, M., Vallittu, P.K.. (2003). Effect of surface conditioning methods on the bond strength of luting cement to ceramics. Dent Mater. 19(8), 725–31. doi: 10.1016/s0109-5641(03)00019-8 Tanaka, R., Fujishima, A., Shibata, Y., Manabe, A., Miyazaki, T.. (2008). Cooperation of phosphate monomer and silica modification on zirconia. J Dent Res. 87(7), 666–70. doi: 10.1177/154405910808700705 Xu, Y., Huang, H.. (2016). Effect of Different Zirconia Ceramics Surface Treatment on the Adhesion Strength of Zirconium to Resin. Chinese Journal of Applied Stomatology. 9(08), 506–508 + 510 Inokoshi, M., Shimizu, H., Nozaki, K., Takagaki, T., Yoshihara, K., Nagaoka, N., Zhang, F., Vleugels, J., Van, M.B., Minakuchi, S.. (2018). Crystallographic and morphological analysis of sandblasted highly translucent dental zirconia. Dent Mater. 34(3), 508–518. doi: 10.1016/j.dental.2017.12.008 Wang, H., Aboushelib, M.N., Feilzer, A.J.. (2008). Strength influencing variables on CAD/CAM zirconia frameworks. Dent Mater. 24(5), 633–8. doi: 10.1016/j.dental.2007.06.030 Wang, J., Deng, J., Shen, B., Ma, L.. (2018). Three Surface Coarsing Methods and the Adherence and Flexural Strength of Zirconia Ceramics: Which Has the Advantage?. Chinese Journal of Tissue Engineering Research.. 22(26), 4196–4201. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editor assigned by journal 25 Jul, 2024 Submission checks completed at journal 25 Jul, 2024 First submitted to journal 24 Jul, 2024 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-4794388","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":331934565,"identity":"51a82fda-df0a-4f3f-92f9-82e414fb1da0","order_by":0,"name":"Xiaomin Yang","email":"","orcid":"","institution":"Shanghai Jiading District Dental Center for Dental Disease Prevention and control","correspondingAuthor":false,"prefix":"","firstName":"Xiaomin","middleName":"","lastName":"Yang","suffix":""},{"id":331934566,"identity":"ae99a317-7adc-46f9-86ff-95499bde3f81","order_by":1,"name":"Huihui Tao","email":"","orcid":"","institution":"Department of Stomatology, The First Affiliated Hospital of Dalian Medical University","correspondingAuthor":false,"prefix":"","firstName":"Huihui","middleName":"","lastName":"Tao","suffix":""},{"id":331934568,"identity":"8cda3aeb-8b30-4e4e-822d-31662668f347","order_by":2,"name":"Yang Liu","email":"","orcid":"","institution":"Department of Stomatology, The First Affiliated Hospital of Dalian Medical University","correspondingAuthor":false,"prefix":"","firstName":"Yang","middleName":"","lastName":"Liu","suffix":""},{"id":331934569,"identity":"64e76aae-0dc6-433b-96a6-adae63be7f7e","order_by":3,"name":"Junju Mu","email":"","orcid":"","institution":"Dalian Institute of Chemical Physics","correspondingAuthor":false,"prefix":"","firstName":"Junju","middleName":"","lastName":"Mu","suffix":""},{"id":331934570,"identity":"e69b389c-c0ba-4a15-b8fd-2a5de4dd7ea6","order_by":4,"name":"Zhuoran Liang","email":"","orcid":"","institution":"Department of Stomatology, The First Affiliated Hospital of Dalian Medical University","correspondingAuthor":false,"prefix":"","firstName":"Zhuoran","middleName":"","lastName":"Liang","suffix":""},{"id":331934571,"identity":"c2e3b3e9-4cc2-4e86-90f7-a081719ea938","order_by":5,"name":"Yannan Zhang","email":"","orcid":"","institution":"Department of Stomatology, The First Affiliated Hospital of Dalian Medical University","correspondingAuthor":false,"prefix":"","firstName":"Yannan","middleName":"","lastName":"Zhang","suffix":""},{"id":331934572,"identity":"905003fc-9cb5-40a6-a22b-455b271a4b1e","order_by":6,"name":"Min Liu","email":"","orcid":"","institution":"Department of Stomatology, The First Affiliated Hospital of Dalian Medical University","correspondingAuthor":false,"prefix":"","firstName":"Min","middleName":"","lastName":"Liu","suffix":""},{"id":331934573,"identity":"344c799b-66e5-4f8c-b430-af42e619decf","order_by":7,"name":"Fanhao Meng","email":"","orcid":"","institution":"Department of Stomatology, The First Affiliated Hospital of Dalian Medical University","correspondingAuthor":false,"prefix":"","firstName":"Fanhao","middleName":"","lastName":"Meng","suffix":""},{"id":331934574,"identity":"48d6400a-5d78-430d-a0c9-3af290dec577","order_by":8,"name":"Zhi Cui","email":"","orcid":"","institution":"Department of Stomatology, The First Affiliated Hospital of Dalian Medical University","correspondingAuthor":false,"prefix":"","firstName":"Zhi","middleName":"","lastName":"Cui","suffix":""},{"id":331934575,"identity":"2e19c68b-9fd6-42aa-8adb-7a9434b34ac9","order_by":9,"name":"Jianfeng Chen","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABA0lEQVRIie3PMUvEMBTA8VcCdckRxxcU/Qo5DnonFP0qkUJdCrd20pRCP0PFwW/hnFLoFO9W4QQrB869RRwcNKOD6Y2C+cMbAu/HIwA+318M7cR4cgrr1+1nHlPG1D4kXcymhSGCmvSY13oPAml+qVoTHk6qNhZKugW7K7t+ITEoqscO0KypAB0Mu8xx5Lm7EiiRHNBV2ot8Q+dEEX778DsRmEXIPzAMaj0X0mzomdIhmTjJ8h2/r1B46SNsqhUVWo6RLLQEQZuIF5UeJ/iURpaIqeqSGZiE8ropnX9hdfJ2hPL65h7aZgv5+QVjZTPsHMRG8Oc7UO59uzKMrvh8Pt+/7gv3RFNmb8BovQAAAABJRU5ErkJggg==","orcid":"","institution":"Department of Stomatology, The First Affiliated Hospital of Dalian Medical University","correspondingAuthor":true,"prefix":"","firstName":"Jianfeng","middleName":"","lastName":"Chen","suffix":""}],"badges":[],"createdAt":"2024-07-24 10:03:16","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4794388/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4794388/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":62984554,"identity":"536ed03f-0989-40e6-915e-12d4d5961fbc","added_by":"auto","created_at":"2024-08-21 18:55:05","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1859306,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of Zirconia with different surface treatments (×5000)\u003c/p\u003e","description":"","filename":"Fig1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4794388/v1/1f7c758daeb06e6ef48f2650.jpg"},{"id":62984555,"identity":"50783729-0553-4620-998c-8a767ef37055","added_by":"auto","created_at":"2024-08-21 18:55:05","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":762792,"visible":true,"origin":"","legend":"\u003cp\u003eXRD pattern of Altron zirconia\u003c/p\u003e\n\u003cp\u003eFigure Note: In the above figures, T is the diffraction peak of tetracrystal phase, 2θ is the diffraction angle on the horizontal axis, and the diffraction peak and peak intensity on the vertical axis.\u003c/p\u003e","description":"","filename":"Fig2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4794388/v1/de622dfe82a54a964784b97a.jpg"},{"id":62984729,"identity":"f30ea3f0-f1c1-43fa-b34c-2a0e7f294522","added_by":"auto","created_at":"2024-08-21 19:03:05","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":774995,"visible":true,"origin":"","legend":"\u003cp\u003eXRD pattern of Cercon zirconia\u003c/p\u003e\n\u003cp\u003eFigure Note: In the above figures, T is the diffraction peak of tetracrystal phase, 2θ is the diffraction angle on the horizontal axis, and the diffraction peak and peak intensity on the vertical axis.\u003c/p\u003e","description":"","filename":"Fig3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4794388/v1/df61326ea4b190e76fe5aa80.jpg"},{"id":62984558,"identity":"2428266f-e935-4649-846d-cf4a9a67c73d","added_by":"auto","created_at":"2024-08-21 18:55:05","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":766020,"visible":true,"origin":"","legend":"\u003cp\u003eThe shear strength of each sample\u003c/p\u003e\n\u003cp\u003eFigure note: A-E represents the shear strength of the blank control, 110 μm alumina blasting, thermal etching, 10 min hot acid etching, 30 min hot acid etching and 60 min hot acid etching of Altron and Cercon zirconia, and F represents the shear strength of the die-casting ceramics. The upper and lower short lines are the highest and lowest values of shear strength of each group, the upper and lower bounds of the column are the upper and lower quartile, the bold line is the median, and the marked values at the top of the graph are the mean and standard deviation.\u003c/p\u003e","description":"","filename":"Fig4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4794388/v1/9cb98de19f64be8de01fb8f8.jpg"},{"id":62984925,"identity":"675f426e-7844-4e24-af2c-aebfdd4e2289","added_by":"auto","created_at":"2024-08-21 19:11:05","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":720485,"visible":true,"origin":"","legend":"\u003cp\u003eThree-point bending strength values\u003c/p\u003e\n\u003cp\u003eFigure note: A-E represents the three-point bending strength of the blank control, 110 μm alumina blasting, thermal etching, 10 min hot acid etching, 30 min hot acid etching and 60 min hot acid etching of Altron and Cercon zirconia. The upper and lower short lines are the highest and lowest values of three-point bending strength of each group, the upper and lower bounds of the column are the upper and lower quartile, the bold line is the median, and the marked values at the top of the graph are the mean and standard deviation.\u003c/p\u003e","description":"","filename":"Fig5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4794388/v1/60919b2bfd60f686390f817a.jpg"},{"id":62985182,"identity":"210a63ab-5301-418c-9d74-24df96625215","added_by":"auto","created_at":"2024-08-21 19:19:07","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5379711,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4794388/v1/d47ad246-118b-4cb9-84ef-4da9daf8b3c2.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Study on shear strength and flexural strength of zirconia treated by hot acid etching","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eWith the development of the concept of minimally invasive oral cavity and the continuous innovation of new prosthodontic materials, public demand for oral medicine is not only the solution to dental pain and the recovery of chewing function. Aesthetic prosthodontics of the oral cavity has become a trend that is increasingly popular and widely accepted. In recent years, zirconia ceramics have gradually replaced metal PFM crowns in oral prosthodontics with their stable physical and chemical properties and aesthetic properties \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e and become a new prosthodontic material that can meet both functional and aesthetic requirements in clinical oral prosthodontics. In dental prosthodontics, the key to the successful clinical application of all-ceramic zirconia is the micromechanical and chemical retention formed by it and the resin cement adhesive. Therefore, forming a good bonding interface with the resin adhesive is important in ensuring the long-term application of zirconia repair in clinical practice \u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. Because zirconia ceramics do not contain glass matrix components, they are insoluble in strong acids and alkalis at room temperature, and their bonding strength is significantly lower than that of die-cast ceramics, which is difficult to meet the requirements of clinical repair on the bonding strength of materials \u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. Using aluminum oxide sandblasting surface of zirconium oxide is the common clinical way of roughening \u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. However, while improving the surface morphology of zirconia and increasing the roughness, it will cause the formation of surface micro-cracks, which increases the risk of micro-leakage between the zirconia and the resin adhesive; therefore, sandblasting cannot completely solve the problem of insufficient adhesion of all-ceramic zirconia. In recent years, zirconia ceramics treated by hot acid etching have become a new technology that is gradually being applied in the field of dental prosthesis. Hot acid etching is the use of high temperature heating strong acid acts on the surface of zirconia; the irregular high-energy atoms around zirconia are corroded and a large number of porous structures are formed on the surface to increase the roughness, which increases the effective area of the bonding, provided a more stable bonding strength for zirconia and resin adhesive, and thus enabled a satisfactory bonding strength of zirconia that meets the requirements of clinical application \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe ideal way of zirconium oxide surface treatment is to satisfy both the clinical bonding strength and mechanical properties of relatively stable. Hence, the purpose of this experiment is to explore the effect of hot acid etching surface treatment on the shear bonding strength and flexural properties of Cercon Zirconia, and to provide a basis for clinical selection of reasonable and effective surface treatment of zirconia.\u003c/p\u003e"},{"header":"2. MATERIALS AND METHODS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Specimen preparation\u003c/h2\u003e \u003cp\u003eTwo kinds of zirconia samples of Cercon HT porcelain block (Dentsply, Germany) were prepared respectively. Type I specimens measured 25 mm \u0026times; 8 mm \u0026times; 1 mm, with 55 pieces each, while Type II specimens consisted of 25 pieces, each measuring 3 mm \u0026times; 3 mm \u0026times; 1 mm. Additionally, there were 5 pieces of die-cast ceramic specimens with specifications (IPS E. Max Press, Ivo Clara Viva Dent, Switzerland) measuring 3 mm \u0026times; 3 mm \u0026times; 1 mm. To maintain uniformity across all specimens, they were completed with water sandpaper of 180, 240, 360, 400, 600, 1000, 1200, and 2000 mesh. After grinding and polishing on the grinding machine, they were soaked in distilled water for 1 minute. Following this, they underwent ultrasonic washing in an ultrasonic cleaning machine for 30 minutes before being air-dried for use.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Selection of hot acid solution\u003c/h2\u003e \u003cp\u003eHot acid etching is a process in which strong acid is heated to high temperatures and applied to the surface of zirconia. This action corrodes the irregular high-energy atoms surrounding the zirconia, forming numerous porous structures on its surface to increase roughness. This increase in roughness enhances the effective bonding area, providing a more stable bonding force for the adhesion of zirconia to resin materials \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e .\u003c/p\u003e \u003cp\u003eIn this experiment, concentrated hydrochloric acid served as the acidic medium, methanol acted as the solvent, and FeCl3 functioned as the oxidant to facilitate the zirconia etching reaction. To ensure the smooth progress of the hot acid etching reaction, methanol was employed as a solvent to maintain reaction pressure. Additionally, a constant temperature magnetic stirring bath was utilized to regulate temperature and control flow rate, thereby ensuring thorough reaction between the zirconia specimen and the hot acid etching solution \u003csup\u003e\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. The advantages of this method include conducting the reaction in a closed reactor, preventing methanol volatilization and consumption. Both methanol and ferric chloride can be reused, contributing to cost-effectiveness. Additionally, hydrochloric acid, as a low-cost corrosive agent, is utilized. The experimental equipment selected is relatively safe, with a reasonable risk coefficient. Furthermore, this study explores the impact of hot acid etching on the surface roughness of zirconia by varying the etching time. It aims to optimize and confirm whether etching time correlates positively with zirconia surface roughness, thereby providing an effective method for clinical zirconia treatment.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Preparation of hot acid etching solution\u003c/h2\u003e \u003cp\u003e100 mL of hot acid etching solution requires 80 mL of methanol (Sinopharm Chemical Reagent Co., Ltd., China), 20 mL of 37% concentrated hydrochloric acid (Tianjin Kemeo Reagent Co., Ltd., China) and 0.2 g of ferric trichloride (Chemical Reagent Co., Ltd., China). The polished zirconia specimens were placed in a sealed reactor (Stainless steel reaction kettle with PTFE lining, Dalian Institute of Chemical Physics, Chinese Academy of Sciences) filled with hot acid etching solution. The reactor was placed in a heated constant temperature magnetic stirring oil bath pot (HWCL-3, Zhengzhou great wall science \u0026amp; trade co., ltd., China) (100℃), and a rotor inside the reactor (rotating speed 400r/min) was used to maintain uniform stirring of the hot acid etching solution \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. The experimental groups\u003c/h2\u003e \u003cp\u003eAfter grinding and polishing, Cercon zirconia specimens were randomly divided into 5 groups (n\u0026thinsp;=\u0026thinsp;5) and treated as follows (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\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\u003eExperimental grouping diagram (A1-E1 is altron zirconia, A2-E2 is cercon zirconia, F is die-casting ceramic)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTreatment\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA1/A2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBlank\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB1/B2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStandblasting\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC1/C2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10 min hot acid etching\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eD1/D2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30 min hot acid etching\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eE1/E2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e60 min hot acid etching\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHydrofluoric acid and silane coupling agent (Die-casting ceramic)\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\u003eBlank control of group A: Cercon zirconia specimens were polished without any other treatment .\u003c/p\u003e \u003cp\u003eSandblasting treatment of group B: At 0.4 Mpa pressure, 110 \u0026micro;m alumina particles were sandblasted at a distance of 10 mm from the surface of the Cercon zirconia specimen for each 20s (Twin-Pen Sandblaster, China). After sand blasting, the test pieces were washed in anhydrous ethanol for 15 min and dried for later use .\u003c/p\u003e \u003cp\u003eGroup C, D, E hot acid etching treatment: Cercon zirconia specimens were placed in a closed reactor with 30 mL hot acid etching solution (24 mL methanol, 6 mL concentrated hydrochloric acid, 0.06 g ferric chloride) heated to 100℃ for reaction of 10 min, 30 min, 60 min, respectively. After the reaction, they were washed in anhydrous ethanol for 15 min and dried for later use .\u003c/p\u003e \u003cp\u003eGroup F hydrofluoric acid group: the polished die-cast ceramics are etched with hydrofluoric acid for 60 s, rinsed under pressure with an air gun head for 20 s until no HF remains, then rinsed with absolute ethanol for 5 minutes, and then blow-dried, set aside and coated with silane coupling agent for 2 min before bonding.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Collection and treatment of isolated teeth\u003c/h2\u003e \u003cp\u003eUpper and lower anterior teeth as well as premolars extracted due to periodontitis or orthodontic reasons were collected, following specific criteria: no defects or caries on the lips of the crown; no bad mineralization and fluoride spots on enamel surface; no root canal treatment; no obvious crack on the lip of tooth crown.The collected isolated teeth were decapitated along the enamel-cementum boundary, placed in normal saline, and stored in cold storage at 4\u0026deg;C for future use. A plane of at least 3 mm \u0026times; 3 mm was prepared on the labial or buccal surface of the isolated teeth using an emery car needle. The thickness was maintained at \u0026le;\u0026thinsp;1 mm to preserve the adhesive interface within the enamel layer. After ultrasonic vibration for 5 minutes, the teeth were stored in distilled water. All procedures were performed by a single operator.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6. Structure characterization\u003c/h2\u003e \u003cp\u003eOne type I Cercon zirconia specimen with different surface treatments was randomly selected and put into a vacuum ion plating machine (EIKO, IB3 Japan) for gold spraying treatment. The specimen sprayed with gold was placed on the stage of scanning electron microscope (Carl Zeiss, Supra 55 sapphire, Germany), and the surface morphology of zirconia was observed with magnification of 5000 times. Then, one type I zirconia specimen with different surface treatments was randomly selected for X-ray diffraction Radiometer (panaco, Empyrean X, the Netherlands) to detect the crystal structure of the surface. The scanning target was copper, the scanning speed was 0.02\u0026deg;/min, and the scanning Angle was 20\u0026deg;-70\u0026deg;.The X-ray diffraction pattern of each specimen was used to analyze whether there was crystal phase transition.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.7. Choice of adhesive\u003c/h2\u003e \u003cp\u003eThe adhesive utilized in this experiment is Panavia F. As a self-etching resin adhesive, it offers advantages over glass ionomer adhesives, polycarboxylic acid cement adhesives, and resin-reinforced glass ionomer adhesives. Notably, Panavia F exhibits high strength and its color meets aesthetic requirements. These qualities contribute to enhanced edge sealing of all-porcelain restorations and reduce microleakage along the restoration edges \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e, thus forming a good bonding effect on the surface of zirconia and enamel. While the total acid etched resin adhesive requires the use of phosphoric acid and pretreatment agent in advance to treat the tooth surface, with high sensitivity of operation technology and uncertain human factors, so the self-etched adhesive with relatively low sensitivity of operation was selected in this experiment. However, the technology of self-adhesive resin adhesive is less sensitive and more convenient to operate. Therefore, how to choose resin adhesive is also a very important factor affecting whether zirconia can form effective bonding with tooth surface at present.\u003c/p\u003e \u003cp\u003eResin adhesives can be categorized based on their components, namely adhesives containing 10-MDP and those without it. Panavia F adhesives belong to the former category as they contain 10-MDP. Souza et al. suggested that resin adhesives or undercoatings containing 10-MDP could effectively enhance the initial bonding strength of zirconia surfaces \u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. The effective bonding between zirconia and enamel relies on both mechanical and chemical retention mechanisms. Mechanical retention is achieved through surface roughening via sandblasting or hot acid etching, while chemical retention is facilitated by the presence of 10-MDP.The functional phosphoric acid groups of 10-MDP react with oxygen atoms on the zirconium oxide surface, forming chemical covalent bonds. Additionally, 10-MDP undergoes olefinic bond and condensation reactions with the resin cement matrix. These processes effectively bind the zirconia and resin together. Therefore, resin adhesive containing 10-MDP is considered the preferred bonding material for zirconia \u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIn conclusion, Panavia F, a self-etching adhesive containing 10-MDP, was chosen for investigation in this experiment. However, as this study only examined the initial bonding strength of Panavia F, further extensive research is necessary to evaluate the bonding strength and long-term durability of adhesives with various types and components. Such studies can offer valuable references and guidance for the clinical application of adhesives.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e2.8. \u003cb\u003eShear test design\u003c/b\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e)\u003c/h2\u003e \u003cp\u003eISO 11405 does not specify the size of the bonding area for shear test specimens but emphasizes considering its impact on bonding strength. The standard mandates applying a force of 10 N vertically to the bonding surface for 10 seconds during the bonding process. Consequently, all specimens in this shear test were set to a size of 3 mm \u0026times; 3 mm \u0026times; 1 mm. For uniform loading during shear force application and to avoid experimental errors from biaxial or torsional forces, a plane loading head was chosen. Placido's study indicated that positioning the load 1 mm away from the bonding interface minimizes stress \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. Additionally, different loading speeds influence shear strength and fracture modes; hence, a loading speed of 0.5 mm/min was maintained based on the bonding interface's fracture mode \u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e.Furthermore, adhesive residue removal is crucial to prevent experimental errors. Thus, during the experiment, adhesives were thoroughly removed without touching the zirconia or die-cast ceramic specimens.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e2.9. Mechanical properties measurement\u003c/h2\u003e \u003cp\u003eThe isolated teeth, each with 1 mm thickness of enamel uniformly ground, were embedded in self-coagulated resin, exposing the enamel bonding surface. Excess resin material at the edges was removed with a mixing knife to ensure full exposure of the enamel bonding surface, aligned completely parallel to the loading interface. After the self-coagulating resin completely hardened, the test specimen was removed. Strict adherence to Panavia F adhesive (Panavia F, Kolili, Japan) requirements was observed during tooth treatment and bonding with Type II zirconia and die-casting ceramic specimens. The enamel bonding interface was initially etched with 35% phosphoric acid for 30 seconds, followed by rinsing with air gun pressure for 15 seconds and blow-drying for 30 seconds. A mixture of Panavia F A and B solutions was evenly applied to the enamel bonding surface with a small brush for 30 seconds. Compound resin Paste A and Paste B were mixed evenly on a mixing plate and then applied to the bonding surface of zirconia and die-casting ceramic specimens. The completed adhesive specimens were secured in an Instron 3345 micro-force tester (Instron, America), subjected to a vertical loading pressure of 10 N for 10 seconds to ensure perpendicular loading direction to the bonding interface. Excess adhesive at the specimen edges was removed, followed by edge sealing and curing with a light curing lamp for 20 seconds. The specimens were then placed in a 37\u0026deg;C water bath for 24 hours. Subsequently, the completed zirconia and die-casting ceramic bonding specimens were positioned on the Instron 3345 micro-force tester, and a loading speed of 0.5 mm/min was set. The loading head, kept parallel to the bonding surface and at a distance of 1 mm from the bonding interface, uniformly loaded the specimens until detachment. The maximum load value (F) at the fracture moment was recorded by the Instron 3345 micro-force tester, and the shear strength was calculated. Observation of the shear fracture interface was conducted under a stereoscopic microscope (NOVEL, Yongxin, Jiangnan, Nanjing, China) at 20x magnification. The fracture interface was classified into zirconia and resin bonding interface fracture, resin cohesion fracture, and tooth enamel and resin bonding interface fracture.\u003c/p\u003e \u003cp\u003eThe Instron 3345 micro-force tester was utilized to assess the three-point bending strength of Type I zirconia specimens following various surface treatments (refer to Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The span was set at 20 mm, with a loading speed of 0.5 mm/min, and the specimens were loaded until fracture occurred. The Instron 3345 micro-force tester recorded the maximum load value at the moment of fracture, allowing for calculation of the three-point bending strength..\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure Note: In the above figures, T is the diffraction peak of tetracrystal phase, 2θ is the diffraction angle on the horizontal axis, and the diffraction peak and peak intensity on the vertical axis.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e2.10. Statistical analysis\u003c/h2\u003e \u003cp\u003eThe results of shear bonding strength and three-point bending strength were analyzed using the single-factor analysis method and T-test method available in SPSS 19.0 statistical software. A statistical significance threshold of P\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was set. XRD results were analyzed using MDI Jade 6 software and Origin 2019 software.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. RESULTS","content":"\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Microstructure and crystal structure\u003c/h2\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eE show the scanning electron microscope images of the blank control, 110 \u0026micro;m alumina sandblasting, 10 min hot acid etching, 30 min hot acid etching and 60 min hot acid etching at 5000 times of Cercon zirconia (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e3\u003c/span\u003e). As shown in the Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e3\u003c/span\u003e, the scanning electron microscope results of Cercon zirconia in the blank control group showed smooth surface, regular and dense grain structure arrangement, and no cracks and pits. The surface structure of Cercon zirconia in 110 \u0026micro;m alumina blasting group showed a strip-shaped pit structure without obvious cracks. The zirconia surface morphology of the hot acid etching group at 10 min, 30 min and 60 min was basically the same, and no obvious difference was observed. According to the figure, the surface of Cercon zirconia after the hot acid etching treatment presented three-dimensional pore structure with grain width enlargement. The results show that the surface roughness of Cercon zirconia is increased by sandblasting and hot acid etching to different degrees, and the hot acid etching effect is more significant.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure Note: In the above figures, T is the diffraction peak of tetracrystal phase, 2θ is the diffraction angle on the horizontal axis, and the diffraction peak and peak intensity on the vertical axis.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Shear bonding strength\u003c/h2\u003e \u003cp\u003eThe value of shear strength of each group is5.47\u0026thinsp;\u0026plusmn;\u0026thinsp;1.33 MPa in A group, 8.22\u0026thinsp;\u0026plusmn;\u0026thinsp;2.40 MPa in B group, 10.89\u0026thinsp;\u0026plusmn;\u0026thinsp;1.43 MPa in C group, 11.09\u0026thinsp;\u0026plusmn;\u0026thinsp;2.39 MPa in D group, 11.02\u0026thinsp;\u0026plusmn;\u0026thinsp;2.39 MPa in E group (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e4\u003c/span\u003e). There is no statistical significance between groups C, D and E (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05), but there is statistical significance between group A and group B, C, D and E, and between group B and C, D and E (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The shear strength of die-cast ceramics in Group F is 27.33\u0026thinsp;\u0026plusmn;\u0026thinsp;2.67 MPa, which is statistically different from that of zirconia in this experiment (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure note: A-E represents the shear strength of the blank control, 110 \u0026micro;m alumina blasting, thermal etching, 10 min hot acid etching, 30 min hot acid etching and 60 min hot acid etching of Altron and Cercon zirconia, and F represents the shear strength of the die-casting ceramics. The upper and lower short lines are the highest and lowest values of shear strength of each group, the upper and lower bounds of the column are the upper and lower quartile, the bold line is the median, and the marked values at the top of the graph are the mean and standard deviation.\u003c/p\u003e \u003cp\u003eAll groups of zirconia fracture interfaces were observed using an optical microscope, focusing on the zirconia and resin bonding interface. A very small number of mixed fractures were observed, with most of the fracture interfaces exhibiting cohesive fractures. In contrast, the fracture interfaces of die-casting ceramics predominantly showed mixed cohesive fractures (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\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\u003eAdhesive section \u003cspan refid=\"Sec13\" class=\"InternalRef\"\u003eresults\u003c/span\u003e of each group\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eZirconia resin bonding interface fracture\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMixed fracture\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTooth enamel resin bonding interface\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB2\u003c/p\u003e \u003cp\u003eC1\u003c/p\u003e \u003cp\u003eC2\u003c/p\u003e \u003cp\u003eD1\u003c/p\u003e \u003cp\u003eD2\u003c/p\u003e \u003cp\u003eE1\u003c/p\u003e \u003cp\u003eE2\u003c/p\u003e \u003cp\u003eF\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003cp\u003e5\u003c/p\u003e \u003cp\u003e5\u003c/p\u003e \u003cp\u003e5\u003c/p\u003e \u003cp\u003e5\u003c/p\u003e \u003cp\u003e5\u003c/p\u003e \u003cp\u003e5\u003c/p\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e1\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Three-point bending strength\u003c/h2\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eThe three-point bending strength values of each group is 1684.2\u0026thinsp;\u0026plusmn;\u0026thinsp;123.2 MPa in A group, 1492.8\u0026thinsp;\u0026plusmn;\u0026thinsp;110.1 MPa in B group, 1337.2\u0026thinsp;\u0026plusmn;\u0026thinsp;57.7 MPa in C group, 1292.8\u0026thinsp;\u0026plusmn;\u0026thinsp;118.7 MPa in D group, 1241.2\u0026thinsp;\u0026plusmn;\u0026thinsp;144.2 MPa in E group (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e5\u003c/span\u003e). There was no statistical significance between groups C, D and E (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05), but there was statistical significance between group A and other groups (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05), and between group B and other groups (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure note: A-E represents the three-point bending strength of the blank control, 110 \u0026micro;m alumina blasting, thermal etching, 10 min hot acid etching, 30 min hot acid etching and 60 min hot acid etching of Altron and Cercon zirconia. The upper and lower short lines are the highest and lowest values of three-point bending strength of each group, the upper and lower bounds of the column are the upper and lower quartile, the bold line is the median, and the marked values at the top of the graph are the mean and standard deviation.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. DISCUSSIONS","content":"\u003cp\u003eMicrostructure and crystal structure\u003c/p\u003e \u003cp\u003eThe scanning electron microscope (SEM) results revealed notable changes in the surface morphology of zirconia treated by different methods compared to the blank control group. The roughness of the treated zirconia surfaces was significantly increased compared to untreated zirconia. In the blank control group, the surfaces of Cercon zirconia appeared relatively smooth, with a dense grain arrangement, slight polishing scratches, and no evident cracks. However, in the zirconia sandblasting group, striated pit-like structures were observed on the surface. Sato et al. suggested that sandblasting treatment may induce the formation of micro-cracks on the surface of zirconia, potentially diminishing its mechanical properties \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eHowever, no obvious signs of microcracks were observed on the surface of zirconia in the sandblasting group in this experiment. This observation could be attributed to the specific sandblasting parameters selected for this study. The experiment was conducted using parameters referenced from Li Xin et al \u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e, suggesting that the conclusion drawn from this experiment aligns closely with their findings.\u003c/p\u003e \u003cp\u003eAfter undergoing different hot acid etching time treatments, the surface of Cercon zirconia exhibited widened grain boundaries, irregular grain arrangement, increased porosity, and enhanced roughness. However, no defects or microcrack formations were observed. This phenomenon aligns with the findings of Javid et al., who suggest that hot acid etching solution may induce the rupture of the protective zirconia film, leading to localized corrosion phenomena. Consequently, this process results in the expansion of grain boundary spaces and the formation of micropores \u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eSimilarly, Wegner et al. demonstrated that the hot acid etching solution has the capability to dissolve the grain structure present on the zirconia surface. This dissolution process leads to the expansion of grain boundaries, ultimately resulting in the formation of a deep three-dimensional porous structure on the surface of the zirconia \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e.The results of this experiment align with previous findings. Interestingly, the SEM images revealed that the surface roughness of zirconia did not significantly change with the extension of thermal etching time; it remained relatively constant. This observation corresponds with the research conducted by Casucci, who subjected Lava to hot acid etching for varying durations (10 min, 30 min, and 60 min) and found that the roughening effect on zirconia surfaces was independent of the reaction time. This consistency between studies suggests that hot acid etching effectively roughens the zirconia surface, regardless of the etching duration. Current literature supports the notion that hot acid etching is an effective method for increasing the surface roughness of zirconia, with minimal reports of microcrack generation. However, further exploration is warranted to understand the long-term stability and fatigue resistance of zirconia.\u003c/p\u003e \u003cp\u003eFigure 6 illustrates the X-ray diffraction analysis results of the Cercon zirconia ceramic specimens in groups A-E. Upon reference to the standard PDF card (card number 50-1089/37-1484) provided by the International Diffraction Data Center, it becomes evident that the main diffraction peak positions of the spectra from each group are consistent with the standard diffraction peak positions of tetragonal zirconia. Analysis of the X-ray diffraction line spectra indicates that the tetragonal phase is the predominant crystal structure of the zirconia ceramics examined. Notably, no monoclinic diffraction peaks were observed in either the blank group or the zirconia group treated by different surface methods. This observation leads to speculation that there may be no transformation from the tetragonal to monoclinic crystal phase (Fig.\u0026nbsp;6).\u003c/p\u003e \u003cp\u003eX-ray diffraction is a technique used to study the composition and crystal structure of materials. By irradiating crystals with X-rays, diffraction patterns are produced at specific angles, which can then be analyzed to determine the type of crystals present in the material \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e,\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. The zirconia utilized in this experiment is yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). According to the PDF card 50-1089 calibrated by the international organization 'Joint Committee on Powder Diffraction Standards,' the corresponding peak angle of the tetragonal crystal phase of zirconia is typically around 30\u0026deg;. It's noted that after various surface treatments, there is a possibility of the unstable monoclinic crystal phase appearing. Research conducted by Lv Pin indicates that the amount of untreated zirconia and the presence of the monoclinic crystal phase after hot acid etching are minimal and negligible. However, sandblasting treatment may result in a significant presence of monoclinic phase components on the surface of zirconia \u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. However, the research results of Jiao Yang et al. revealed that the volume fraction of the monoclinic crystal phase in zirconia after hot acid etching treatment was higher compared to that after sandblasting. Specifically, the volume fractions were reported as 17.81% and 12.50%, respectively\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. According to the analysis of zirconia XRD results in this experiment, characteristic peaks corresponding to the tetragonal crystal phase were observed in all samples, while no characteristic peaks indicative of the monoclinic crystal phase were detected. However, due to the limited literature in this field and the absence of definitive conclusions, the results of this experiment alone are insufficient to prove the transformation of zirconia's tetragonal crystal phase to the monoclinic phase following different surface treatments. To establish a clearer conclusion, further investigation is warranted, possibly by refining the detection method.\u003c/p\u003e \u003cp\u003eShear bonding strength\u003c/p\u003e \u003cp\u003eAccording to the analysis of shear results, there was A statistical difference in shear strength between the blank control group of group A and the sandblasting group B (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05), the shear strength of sandblasting group B and hot acid etched group C, D and E were statistically different (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05), there was no statistical difference in the shear strength of hot etched groups C, D and E (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). The results indicate that both sandblasting and hot etching can effectively increase the shear bonding strength of Zirconia and resin adhesive, and the hot etching increases the shear bonding strength more significantly, and has no obvious correlation with the reaction time of hot etching. Casucci's study showed that the bonding strength of Lava zirconia treated by hot acid etching was significantly higher than that of sand-blasted zirconia and zirconia without any treatment, which was independent of the reaction time \u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. Combined with the results of scanning electron microscope, it can be seen that the surface of zirconia can be observed strip pit structure after sandblasting, however, after hot acid etching, a large area of acid etching can be seen, and the zirconia grain boundary can be seen to be broadened by the amplification power, and a large number of pore structures can be seen on the surface. Therefore, the experimental results are consistent with these results.\u003c/p\u003e \u003cp\u003eThe shear experimental results reveal that the shear strength value of group F was 27.33\u0026thinsp;\u0026plusmn;\u0026thinsp;2.67 MPa, significantly higher than that of zirconia and holds substantial significance (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Puppin-Rontani et al. investigated the impact of hydrofluoric acid concentration and etching duration on the bonding strength of lithium silicate glass ceramics, achieving a bonding strength of 32.9\u0026thinsp;\u0026plusmn;\u0026thinsp;2.2 MPa with 10% HF \u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. Similarly, Chao Chen's research reached a comparable conclusion, reporting an adhesive force of 31.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9 MPa for glass ceramics etched with HF acid \u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. The findings of this experiment align closely with these studies. Based on the experimental results, zirconia treated by sandblasting or hot acid etching still exhibits a disparity in shear strength compared to glass ceramics with more established surface treatment technologies. The die-cast ceramic block is classified as a type of glass ceramics. Glass ceramics typically consist of components such as feldspar, leucite, and lithium disilicate. These materials can be effectively etched by hydrofluoric acid to achieve a desirable surface roughness. Hydrofluoric acid is widely recognized as the optimal surface treatment agent for glass ceramics \u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. Hydrofluoric acid operates by selectively reacting with the silicate components present in glass ceramics \u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e,\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e, thereby disrupting the Si-O bonds. This reaction results in the formation of fluorosilicate compounds and exposes the crystal structure of lithium disilicate. Consequently, a rough network structure is created on the surface of the glass ceramics \u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e,\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e, which enhances the wettability and alters the surface energy of the material. The bonding characteristics between glass ceramics and resin adhesives rely on the presence of silica on the glass ceramic surface. Silica facilitates chemical compatibility by utilizing a silane coupling agent to achieve optimal bonding properties \u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. One end of the silane molecule features an organic functional group capable of polymerizing with the organic constituents of the resin adhesive. The other end contains an alkoxy group that reacts with the hydroxyl groups on the glass ceramic surface. This dual functionality enables the silane coupling agent to serve as an effective intermediary, promoting sufficient bonding strength between the glass ceramic and resin adhesive \u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. Unlike glass ceramics, zirconia ceramics lack a glass matrix component, rendering them unsuitable for hydrofluoric acid treatment \u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e. Consequently, silane coupling agents are unable to synergistically enhance the bonding properties of zirconia ceramics. The experimental findings demonstrate that while hot etching treatment can increase the surface roughness and bonding strength of zirconia with resin, there remains a significant disparity in bonding strength between zirconia and glass ceramics. Further exploration and refinement of surface treatment methods are necessary to achieve simplicity of operation and outstanding results.\u003c/p\u003e \u003cp\u003eThree-point bending strength\u003c/p\u003e \u003cp\u003eAccording to the results of the three-point bending test, the flexural strength of Cercon zirconia decreases to varying degrees after sandblasting and hot acid etching treatments, with the hot acid etching group showing a more pronounced decrease. Several factors influence the flexural strength of zirconia, including both internal and external factors. Internal factors encompass aspects such as zirconia's processing techniques and raw material composition. On the other hand, external factors leading to the reduction in zirconia's flexural strength may include crystal phase transformation, loss of surface grain structure, and the generation of microcracks following zirconia surface treatment \u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. Sandblasting increases surface roughness, but it also escalates the risk of microcrack formation and loss of surface structure in zirconia. Research suggests that the size of sandblasting particles correlates with microcrack formation, and larger particles can lead to more significant surface loss. The 110\u0026micro;m sandblasting particles used in this experiment may mitigate the occurrence of microcracks and surface loss to some extent \u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e, but the inherent risks associated with sandblasting cannot be entirely eliminated. Regarding the decrease in flexural strength due to hot acid etching, most scholars attribute it to crystal phase transformation. Wang Ji-de et al. demonstrated that hot acid etching treatment induces more crystal phase transitions in zirconia \u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. However, in this experiment, no crystal phase transitions were observed through X-ray diffraction analysis. According to the experimental results of three-point bending strength, there isn't a significant decrease in bending strength with the extension of hot etching time. The experimental investigation on roughness confirms that the surface roughness of zirconia remains unaffected by the etching time, suggesting that this outcome is associated with the inherent structure of zirconia material itself.\u003c/p\u003e"},{"header":"5. CONCLUSION","content":"\u003cp\u003e1. Hot acid etching increased the surface roughness of Cercon zirconia, but the increase of surface roughness of zirconia had no correlation with the hot acid etching time.\u003c/p\u003e \u003cp\u003e2. Hot acid etching increased the shear bonding strength of Cercon zirconia, but it is still significantly lower than that of die-casting ceramics and is independent of the hot acid etching time.\u003c/p\u003e \u003cp\u003e3. After hot acid etching treatment, the flexure strength of Cercon zirconia decreased to different degrees.\u003c/p\u003e \u003cp\u003e4. The grain structure of Cercon zirconia after hot acid etching treatment showed no apparent transformation from tetracrystalline phase to monoclinous phase, so it is speculated that the physical and chemical properties of Cercon Zirconia after hot acid etching treatment are relatively stable.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eCLINICAL RELEVANCE STATEMENT\u003c/p\u003e\n\u003cp\u003eTo solve the clinical problem of insufficient bonding strength of zirconia, we evaluate the bonding performance of zirconia ceramics after thermal etching.This conclusion has an important guiding role for the clinical application of zirconia ceramics.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eMethodology and writing- original draft, XY; Investigation, writing and formal analysis,HT; Conceptualization, review and editing, YL and HT; Writing and editing, JM and ZL; Investigation and editing YZ; Resources, ML; Writing, FM; Methodology and supervision, ZC; Methodology, resources and supervision, JC; All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e\u003ch2\u003eDATA AVAILABILITY STATEMENT\u003c/h2\u003e \u003cp\u003eThe original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eChen, D., Wang, N., Gao, Y., Shao, L. q., Deng, B.. 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Chinese Journal of Tissue Engineering Research.. 22(26), 4196\u0026ndash;4201.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"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":"mechanics-of-time-dependent-materials","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"mtdm","sideBox":"Learn more about [Mechanics of Time-Dependent Materials](http://link.springer.com/journal/11043)","snPcode":"11043","submissionUrl":"https://submission.nature.com/new-submission/11043/3","title":"Mechanics of Time-Dependent Materials","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-4794388/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4794388/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn recent years, zirconia ceramics have been widely used as in prosthodontics because of their good aesthetics and mechanical properties. At present, the thermal acid etching technology for treating zirconia ceramics has gradually emerged as a new method. In this study, the effect of thermal acid etching surface treatment on the shear strength and flexural properties was investigated. In the fourth sentence, it might be clearer to specify that the zirconia ceramics were divided into five groups: \"In the experiment, the zirconia ceramics were divided into five groups, each receiving a different treatment: blank, 110\u0026micro;m alumina sandblasting, 10-minute thermal acid etching, 30-minute thermal acid etching, and 60-minute thermal acid etching.The surface morphology, crystal structure, and the initial shear bonding strength of zirconia were analyzed by scanning electron microscope (SEM), X-ray diffractometer (XRD), and Instron3345 micro-force testing machine, respectively.SPSS19.0 software was used for the statistical analysis of experimental data, and the statistical difference was set as P\u0026thinsp;\u0026lt;\u0026thinsp;0.05. The experimental results show that the thermal acid etching technology can effectively increase the surface roughness of zirconia and the shear bonding strength of zirconia and resin adhesive, the effect is obviously better than that of sandblasting, and there is no obvious correlation with the time of technology. This conclusion is of significant importance for guiding oral clinical treatment.\u003c/p\u003e","manuscriptTitle":"Study on shear strength and flexural strength of zirconia treated by hot acid etching","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-21 18:55:00","doi":"10.21203/rs.3.rs-4794388/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorAssigned","content":"","date":"2024-07-26T01:30:08+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-07-25T07:28:16+00:00","index":"","fulltext":""},{"type":"submitted","content":"Mechanics of Time-Dependent Materials","date":"2024-07-24T10:01:58+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"mechanics-of-time-dependent-materials","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"mtdm","sideBox":"Learn more about [Mechanics of Time-Dependent Materials](http://link.springer.com/journal/11043)","snPcode":"11043","submissionUrl":"https://submission.nature.com/new-submission/11043/3","title":"Mechanics of Time-Dependent Materials","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"7412ba07-3cff-4947-a4dd-0424183321f1","owner":[],"postedDate":"August 21st, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2024-08-21T18:55:01+00:00","versionOfRecord":[],"versionCreatedAt":"2024-08-21 18:55:00","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4794388","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4794388","identity":"rs-4794388","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}