Introduction: The removal of ceramic veneers is a time-consuming procedure in a dental office. Little research has been done in alternative removal techniques for ceramic veneers. The objective of this study was to evaluate the removal of feldspathic and lithium disilicate reinforced glass ceramic veneers by Er, Cr: YSGG and to measure debonding time and pulpal temperature increase during veneer removal. Methods: Fifty-seven bovine incisor teeth were prepared and divided into 3 groups. Ceramic specimens with a thickness of 0.7mm, a width of 4mm and a length of 8 mm were fabricated from feldspathic ceramic, lithium disilicate reinforced glass ceramic HT (high translucency) and lithium disilicate reinforced glass ceramic MO (medium opacity) (19 for each group). Specimens were cemented on the labial surface of incisors using resin cement. The Er, Cr: YSGG laser was applied to each specimen at 2.5 W and 25 Hz. Debonding time was measured for each specimen, and the intrapulpal temperature was detected in 3 specimens for each group. Data were analyzed via one-way analysis of variance (ANOVA) at significance level of 0.05 (α = 0.05). Results: Mean debonding time was 103.68 (26.76), 106.58 (47.22) and 103.84 (32.90) seconds for feldspathic, lithium disilicate MO, and lithium disilicate HT respectively. There was no significant statistical difference among the groups (P value = 0.96). The intrapulpal temperature increase was less than 1°C in all groups. Conclusion: Er, Cr: YSGG can successfully be used to efficiently debond feldspathic and lithium disilicate reinforced glass ceramic veneers. There was no significant difference for debonding time among these ceramic materials. During ceramic laminate veneer removal by laser irradiation, no irritating temperature rise was detected.

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Objectives. Despite the widespread use of resin cements in cementing dental restorations, their bond strength to CAD/CAM base metal alloys is not widely studied. This study aimed to evaluate the microshear bond strength (μSBS) between cobalt-chrome (Co-Cr) alloys fabricated using casting or CAD/CAM methods with three types of resin cements. Materials and Methods. Fifty Co-Cr blocks were prepared with CAD/CAM or casting technique. Specimens were divided using primer or not and bonded to three types of resin cements: Panavia F2, RelyX Unicem, and Duo-Link. The differences between the mean μSBS values were analyzed using the two-way ANOVA test and Tukey analysis (α = 0.05). The mode of failure was evaluated using a stereomicroscope. In addition, the specimens were examined by scanning electron microscopy (SEM) based on two received signals: backscattered electrons (SEB) and secondary electrons (SEs). One intact alloy specimen in each group was analyzed by energy-dispersive X-ray spectroscopy (EDX). Results. Most of the specimens in the no-primer group were prematurely debonded. Statistical analyses showed that the interaction between the alloy substrate and cement type was significant ( p = 0.001 ). The bond strength of Panavia F2 was significantly higher than Duo-Link in the CAD/CAM group ( p = 0.001 ). SEM evaluation confirmed the difference in grain structures, while EDX showed no remarkable difference in the chemical composition of the alloy substrates. Conclusion. Alloy fabrication technique may influence the bond strength of resin cements. In the CAD/CAM group, cement containing MDP molecules exhibited higher strength than the etch-and-rinse one.

Many surgical treatments require a suitable tissue adhesive that maintains its performance in wet conditions and can be applied simultaneously for hard and soft tissues. In the present study, a dual cross-linked tissue adhesive was synthesized by mixing the gelatin methacryloyl (Gel-MA) and gelatin-dopamine conjugate (Gel-Dopa). The setting reaction was based on a photopolymerization process in the presence of a combination of riboflavin and triethanolamine and a chemical cross-linking process attributed to the genipin as a natural cross-linker. Modified gelatin macromolecules were characterized and the best wavelength for free radical generation in the presence of riboflavin was obtained. Tissue adhesives were prepared with 30% hydrogels of Gel-MA and Gel-Dopa with different ratios in distilled water. The gelation occurred in a short time after light irradiation. The chemical, mechanical, physical, and cytotoxicity properties of the tissue adhesives were evaluated. The results showed that despite photopolymerization, chemical crosslinking with genipin played a more critical role in the setting process. Water uptake, degradation behavior, cytotoxicity, and adhesion properties of the adhesives were correlated with the ratio of the components. The SEM images showed a porous structure that could ensure the entry of cells and nutrients into the surgical area. While acceptable properties in most experiments were observed, all features were improved as the Gel-Dopa ratio increased. Also, the obtained hydrogels revealed excellent adhesive properties, particularly with bone even after wet incubation, and it was attributed to the amount of gelatin-dopamine conjugate. From the obtained results, it was concluded that a dual adhesive hydrogel based on gelatin macromolecules could be a good candidate as a tissue adhesive in wet condition.

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Background and Aim: The conventional procedure for removal of porcelain laminate veneers (PLVs) is time-consuming and inconvenient. The purpose of this study was to evaluate the efficacy of Er:YAG laser for debonding of PLVs. Materials and Methods: Forty-eight intact extracted human maxillary anterior teeth received discoid PLVs (24 feldspathic and 24 e-max ceramic). The PLVs had 0.7 mm thickness and 4 mm diameter. After cementation of all PLVs with a light-cure cement, samples were stored at 37ºC distilled water for 48 h. Samples of each ceramic were randomly divided into 3 groups of 8 samples. Then, laser was irradiated on the cemented PLVs as follows: (I) feldspathic PLVs without laser irradiation (control group), (II) feldspathic PLVs with laser irradiation (6 s, 10 Hz, 200 mJ, 2 W), (III) feldspathic PLVs with laser irradiation (6 s, 10 Hz, 300 mJ, 3 W), (IV) e-max PLVs without laser irradiation (control group), (V) e-max PLVs with laser radiation (6 s, 10 Hz, 200 mJ, 2 W), (VI) e-max PLVs with laser irradiation (6 s, 10 Hz, 300 mJ, 3 W). The shear bond strength of all samples was measured using a universal testing machine. We used Mann-Whitney and Kruskal-Wallis tests for data analysis (P<0.05). Results: Laser irradiation decreased the shear bond strength of both ceramics. But this decrease was only significant for the e-max group (P<0.05). No significant difference was found between different laser irradiation powers in the two ceramic groups. Conclusion: Er: YAG laser is effective for debonding of e-max PLVs.

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Background: The current study aimed to assess the amount of fluoride released from fluoride-containing dental adhesives and its effect on micro-tensile bond strength (µTBS) and on resistance to demineralisation of dentine and enamel. Material and Methods: Two fluoride-containing dental adhesives, and a fluoride-free adhesive were used as experimental adhesives. After thermal cycling the µ-TBS of adhesives to dentine and the failure mode were assessed. The fluoride release and cross-sectional microhardness (CSMH) of specimens were measured before and after one day, 7 and 28 days of pH-cycling. The data were analysed using one-way ANOVA, Weibull statistics and repeated measures ANOVA. Results: The results indicated a significant difference between the group of FL and both the SE and LBF groups (p≤0.001). The CSMH values of both the dentine and enamel underneath the adhesives was reduced at 28 th day of the pH-cycling compared to the baseline (p≤0.001). From day 1 to day 28, the released fluoride declined in both the fluoride containing dental adhesives (p≤0.001). Conclusions: Based on the results, the released fluoride from dental adhesives may adversely influence the bond strength and durability of the resin/dentine interface. Moreover, the released fluoride didn't improve the resistance to demineralisation of adjacent enamel and dentine to bond interface.