Efficacy and durability of bleaching with diode lasers: an in vitro study.

The aim of this in vitro study was to compare the efficacy and durability of bleaching with diode lasers over a 9-month period. This study evaluated 27 extracted teeth categorized into 3 bleaching groups (n = 9): 940-nm diode laser, 980-nm diode laser, and 40% hydrogen peroxide whitening gel (control). After the baseline color of the teeth was measured using a spectrophotometer, the teeth underwent dental prophylaxis and their color was measured again. Bleaching treatment was then performed. The color of the teeth was measured immediately after bleaching and 1 day (24 hours), 1 week, 1 month, 3 months, 6 months, and 9 months after bleaching. The Commission Internationale de l'Eclairage (CIE) L*a*b* color change (ΔE*) at each timepoint was calculated and compared using repeated-measures analysis of variance. All bleaching techniques effectively whitened the teeth to a clinically perceptible level (ΔE* > 3.3), and there were no statistically significant differences among the groups (P > 0.05). The mean ΔE* values of the laser groups were not significantly different from the mean value of the control group during the 9-month evaluation period (P > 0.05). However, statistically significant differences among the groups were noted when color measurements at the following timepoints were compared: immediately after bleaching vs 1 day; 1 day vs 1 week; and 3 months vs 6 months (P < 0.05). Use of a 940-nm diode laser, 980-nm diode laser, or conventional hydrogen peroxide gel provided equally effective bleaching. The color change remained clinically perceptible throughout the 9-month period.

Effect of matrix metalloproteinase inhibitors on microtensile bond strength of dental composite restorations to dentin in use of an etch-and-rinse adhesive system.

AIM: This study assesses the effect of matrix metalloproteinases on microtensile bond strength (µTBS) of an etch-and-rinse adhesive system. METHODS: This in vitro study evaluated 88 extracted premolars. The teeth were sectioned to expose dentin and were then randomly divided into four groups (n = 22). In group 1 (control), dentin surface was etched, and Adper Single Bond 2 was applied. In groups 2-4, dentin surface was etched and chlorhexidine (CHX), 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), and dimethyl sulfoxide (DMSO) were applied on the surfaces, respectively, and blotted dry. Next, Adper Single Bond 2 was applied and all teeth were built up with Z350 composite. In each group, half the samples immediately and the other half after 10,000 thermal cycles underwent µTBS test. Data were analyzed using ANOVA and Tukey's test (α = .05). RESULTS: In thermocycled samples, maximum µTBS was noted in CHX group followed by DMSO, EDC, and control group (p < .001). The thermocycled µTBS of composite to dentin was significantly higher in CHX group compared with EDC, DMSO, and control groups (p < .001) but was not significantly different in EDC and DMSO groups (p = .498). CONCLUSION: The thermocycled µTBS obtained by the application of CHX, EDC, and DMSO was significantly higher compared with the value to the control group.

The effect of office bleaching on the color and bond strength of resin restorations.

BACKGROUND: Bleaching may affect the bond strength of existing composite fillings and may weaken it. Hence, the aim of this study was to find the best method of in-office bleaching with the least effect on microshear bond strength (MSBS) of existing composite resin fillings to tooth structure. MATERIALS AND METHODS: In this in vitro study, Class V cavities were prepared on buccal surface of 50 extracted third human sound molars. The cavities in 25 teeth had enamel axial walls, Group E, which were divided into five subgroups of E1 through E5 and in 25 teeth had dentin axial walls, Group D, which were divided into five subgroups of D1 through D5. Cavities were treated with Single Bond 2 adhesive system and restored with composite resin (Z250). The corresponding subgroups received similar bleaching methods and materials; 1 - not bleached, 2 - hydrogen peroxide (HP) 25%, 3 - HP + ultraviolet light, 4 - HP + light-emitting diode-curing device, and 5 - HP + diode laser. Teeth colors were monitored before and after bleaching, and MSBS test and failure modes were examined. Results were analyzed with one-way ANOVA and Kruskal-Wallis tests. P < 0.05 was considered significant. RESULTS: One-way ANOVA did not show differences in MSBS of enamel subgroups but showed significant differences in dentin subgroups (P < 0.00). Adhesive fracture in all of the subgroups was the most frequent mode of failure. Kruskal-Wallis test showed that laser was the most effective instrument to change ΔE. CONCLUSION: Diode laser was the best method for tooth bleaching because lowering the shear bond strength between composite resin and enamel was minimum and also had the most ΔE in tooth bleaching.