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Objective: The aim of this study was to investigate the effect of Nd:YAG and argon laser irradiations on enamel demineralization after two different models to induce artificial caries., Background Data: It is believed that the use of the high-intensity laser on the dental structure can lead to a more acid-resistant surface., Materials and Methods: Twenty-one extracted human third molars were sectioned into tooth quarters. The quarters were distributed in three groups: Group I (control), untreated; Group II, Nd:YAG laser (60 mJ, 15 pps, 47.77 J/cm(2), 30 sec); and Group III, argon laser (250 mW, 12 J/cm(2), 48 sec). Tooth quarters from each group were subjected to two different demineralization models: cycle 1, a 14 day demineralization (pH 4.5; 6 h) and remineralization (pH 7.0; 18 h) solutions, 37 °C and cycle 2, 48 h in demineralization solution (pH 4.5). Samples were prepared in slices (60-100 μm thick) to be evaluated under polarized light microscopy. Demineralization areas were measured (mm(2)) (n=11). Data were analyzed by ANOVA and Tukey's test (p<0.05)., Results: Means followed by different letters are significantly different: 0.25 A (control, cycle 48 h); 0.18 AB (control, cycle 14 days); 0.17 AB (Nd:YAG, cycle 14 days); 0.14 BC (argon, cycle 48 h); 0.09 BC (Nd:YAG, cycle 48 h), and 0.06 C (argon, cycle 14 days)., Conclusions: The argon laser was more effective for caries preventive treatment than Nd:YAG laser, showing a smaller demineralization area in enamel.

Objective: This study analyzed the adhesive-dentin interface when Nd:YAG and Er:YAG lasers were applied to dentin., Background Data: Lasers applied to dentin cause morphological changes of this tissue. Because adhesive systems bond to dentin through the hybrid layer, it is important to investigate the adhesive-dentin interface when dentin is irradiated with lasers., Methods: The occlusal dentin of 12 human molars was exposed and polished with 400 and 600 grit silicon carbide abrasive paper. Teeth were randomly divided into six groups: Group 1, adhesive system Adper Single Bond 2 (SB); Group 2, adhesive system Clearfil SE Bond (CSB); Group 3, Nd:YAG laser (60 mJ, 15 Hz, 0.9 W) and SB; Group 4, Nd:YAG laser (60 mJ, 15 Hz, 0.9 W) and CSB; Group 5, Er:YAG (200 mJ, 4 Hz, 0.8 W) and SB; Group 6, Er:YAG (200 mJ, 4 Hz, 0.8 W) and CSB. Blocks of composite resin were built upon the adhesive system. Tooth-resin sets were cut in a mesio-distal direction, resulting in four samples for each group. Surfaces were polished until 1200 grit silicon carbide abrasive paper, followed by diamond pastes. Samples were demineralized, deproteinized, dried, metalized, and evaluated by scanning electron microscopy., Results: SB formed a thicker hybrid layer, with resin tags longer than CSB. Nd:YAG laser application on the dentin surface, prior to the adhesive procedures, resulted in a thinner hybrid layer with fewer resin tags. Er:YAG laser application on the dentin surface, prior to the adhesive procedures, did not allow the formation of a hybrid layer but formed resin tags., Conclusion: Nd:YAG and Er:YAG laser changed the adhesive-dentin interface.

Objective: The aim of this study was to evaluate the effect of different surface treatments on bond strength between In-Ceram Alumina (VITA) and Panavia Fluoro Cement (Kuraray), and to verify the association between bond strength values and the percentage of remaining cement on the ceramic surface., Background Data: Although several conventional surface treatments have been used on aluminous ceramic, no study investigated the effect of the Nd:YAG laser., Methods: Nine In-Ceram Alumina blocks (10 x 10 x 6 mm) received three surface treatments: group 1, Al(2)O(3) sandblasting + silane; group 2, Al(2)O(3) sandblasting + Rocatec Plus + silane; and group 3, Al(2)O(3) sandblasting + Nd:YAG Laser + silane. Resin cement was applied and light cured, followed by the application of composite. Blocks were sectioned to obtain sticks with a cross-sectional area of 1.0 mm(2). Microtensile bond strength (microTBS) was recorded in a universal testing machine at a crosshead speed of 0.5 mm/min. Scanning electron microscopy images of the fractured areas were used to calculate the amount of remaining cement on the ceramic substrate., Results: All treatments yielded statistically different microTBS values (MPa): group 1, 14.38(A); group 2, 20.09(B); and group 3, 23.21(C) (ANOVAand Tukey's test, alpha = 0.05). Pearson's correlation coefficient for microTBS x percentage of remaining cement was r = 0.92 (p < 0.05)., Conclusions: The Nd:YAG laser was the most effective surface treatment, followed by Rocatec and Al(2)O(3) sandblasting. A strong positive association was found between bond strength values and percentage of remaining cement.

Objective: This in vitro study evaluated the tensile bond strength of Single Bond adhesive system to indirect composite surfaces treated with Er:YAG laser, fluoridric acid, or air abrasion., Background Data: Application of adhesive techniques is well established in restorative dentistry, yet the influence of surface treatments on the bond strength of adhesive systems to indirect composite restorations prior to luting or repair procedures remains unclear., Methods: Two hundred and ten samples made of three indirect composites (BelleGlass, Sculpture, and Targis) were divided into 21 groups (n = 10) and treated with (1) control (no treatment); (2) silane (RelyX 3M ceramic primer); (3) 10% fluoridric acid; (4) Er:YAG laser; (5) Er:YAG laser + 10% fluoridric acid; (6) air abrasion; and (7) air abrasion + 10% fluoridric acid. Afterwards, silane and Single Bond adhesive system were applied on each treated surface, and a direct composite resin (Z250) cone was built. The prepared specimens were submitted to tensile bond strength test and stereoscopy evaluation to determine the type of failure after rupture., Results: Bond strength mean values were statistically different in function of indirect composite and surface treatment. BelleGlass treated with Er:YAG laser had the highest mean value (22.92 MPa), and Sculpture conditioned with fluoridric acid had the lowest mean (11.88 MPa). Stereoscopy showed a predominant cohesive failure in Targis resin and mixed type for Sculpture and BelleGlass., Conclusions: These results suggest that Single Bond tensile bond strength improves with Er:YAG laser as a surface treatment compared to fluoridric acid or air abrasion.