Bond strength of resin composite to light activated bleached enamel.

OBJECTIVES: This study evaluated the microtensile bond strength (µTBS) of a resin composite bonded to bleached enamel as a function of bleaching conditions. MATERIALS AND METHODS: The whiteness hydrogen peroxide (HP) bleaching agent containing 35% HP was applied to the central incisors' facial enamel surface and irradiated as follows: No treatment (G1; control); no light (G2); light-emitting diode, the 40s (G3); diode laser, the 20s (G4); and neodymium:yttrium aluminum garnet laser, 20s (G5). A Variolink II resin composite structure was then built up incrementally on the surface. The teeth were sectioned into three 1.2 mm × 1.2 mm wide "I"-shaped sections. The specimens were then subjected to microtensile testing at a crosshead speed of 1 mm/min. Data were analyzed using one-way ANOVA (α =0.05) followed by the Tukey Honestly Significant Difference post-hoc test. The fractured surfaces were observed with a stereomicroscope at × 100 magnification. RESULTS: One-way ANOVA revealed no statistical differences among the groups (P > 0.05). No differences appeared between the groups bonded 14 days after bleaching (P > 0.05). Mean µTBS values (MPa) were as follows: 22.05 ± 5.01 (G1); 19.6 ± 5.6 (G2); 19.3 ± 5.4 (G3); 20.08 ± 2.08 (G4); and 18.1 ± 4.8 (G5). Many adhesive failures occurred at the bleached and irradiated enamel surfaces. CONCLUSION: The various irradiation treatments following the application of the whiteness HP bleaching agent to enamel did not significantly reduce the µTBS within a 14-day period.

The effect of bleaching agents on the color stability of ceromer and porcelain restorative materials in vitro.

PURPOSE: The aim of this in vitro study was to determine the color changes of five different restorative materials after exposing these materials to two different home bleaching agents. METHODS: This study applied bleaching agents to an ultralow-fusing porcelain, a low-fusing porcelain, two types of heat-pressed glass ceramics, and a ceromer. A total of 24 disc-shaped specimens were fabricated (with a diameter of 10 mm and a thickness of 2 mm) from each material (n=12). The initial color measurements were taken with a spectrophotometer. The first set of specimens were bleached with 10% hydrogen peroxide (HP) for one hour daily for 10 days. The other set of specimens were bleached with 10% carbamide peroxide (CP) bleaching gel for eight hours daily for 14 days. Data were analyzed with the one-way analysis of variance and Kruskal-Wallis statistical test. The difference in the prebleaching and postbleaching color of each material was considered to be statistically significant at p < 0.05. RESULTS: The study found a statistically significant difference among the color changes of the test groups after exposing them to both bleaching agents (p<0.05). Appreciable color change was observed in the Estenia (ΔE=3.99) specimens that were bleached with the HP, and noticeable color changes were observed in the Estenia (ΔE=1.89) and IPS Empress 2 (ΔE=1.66) groups when they were treated with the CP. CONCLUSIONS: Restorations (especially polymer-containing restorative materials) should be protected before any bleaching procedure due to the high risk of color change.

Comparison of the Color Change of Porcelain Laminate Veneers Produced by Different Materials After Luting with Three Resin Cements.

OBJECTIVES: This study aimed to compare color change of porcelain laminate veneers fabricated with two lithium disilicate ceramics and a zirconia-reinforced lithium silicate ceramic material after luting with conventional dual-cure, amine-free dual-cure, or light-cure resin cements using artificial accelerated aging (AAA). METHODS AND MATERIALS: Ninety noncarious human maxillary central incisors were embedded in autopolymerizing acrylic resin blocks to prepare conventional laminate veneers with incisal coverage. Prepared teeth were randomly divided into 3 groups (n=30) to fabricate laminate veneer restorations using: (1) lithium disilicate ceramic, (2) lithium disilicate ceramic with high-density micronization, and (3) zirconia-reinforced lithium silicate ceramic. Impressions of the preparations were taken with a laboratory scanner. Acquired 3D images were processed into a surface tessellation language file. Data were exported for 3D printing on a printer, and laminate veneers were printed in castable wax resin. Ceramic veneers were heat-pressed after investment according to the manufacturer's recommendations and further divided into three groups (n=10) according to luting cement type: (1) light-cure resin cement, (2) amine-free dual-cure resin cement, and (3) conventional dual-cure resin cement. Color measurements were performed from the middle of each specimen with a spectrophotometer before and after AAA for 300 hours with a total energy of 150 kJ/m2. Color changes were calculated with the CIEDE 2000 (ΔE00) formula. Color differences were assessed using two-way analysis of variance (ANOVA) (α=0.05), and the paired t-test was used to compare the L*, a*, and b* parameters in each group before and after aging. RESULTS: There were no significant differences between the ceramic groups (p>0.05). The color changes of the materials ranged from 2.26 to 3.13. All materials were above the clinically acceptable limit (ΔE00>1.8). The conventional dual-cure resin cement group showed more color change (p>0.05). CONCLUSIONS: Color changes were observed in all porcelain laminate veneers after artificial accelerated aging. The zirconia-reinforced lithium silicate veneers showed similar color changes as lithium disilicate veneers; the amine-free dual-cure resin cement showed a similar color change as light-cure resin cement after aging.

Effect of provisional restorations on the final bond strengths of porcelain laminate veneers.

The purpose of this in vitro study was to evaluate the effect of the different provisional restorations cementation techniques on the final bond strengths of porcelain laminate veneers (PLVs). Thirty-six extracted human central incisors were sectioned 2 mm below the cemento-enamel junction, and crown parts were embedded into self-cure acrylic resin. Standardized PLV preparations were carried out on labial surfaces of the teeth. Then the teeth were randomly divided into three groups of 12 each. In group 1, provisional restorations were cemented with eugenol-free cement. In group 2, prepared teeth surfaces were first coated with a desensitizing agent then provisional restorations were cemented with resin cement. In group 3, provisional restorations were not fabricated to serve as control. After specimens were stored in distilled water for 2 weeks, provisional restorations were removed and final IPS Empress 2 ceramic veneers were bonded with a dual-curing resin. Two microtensile samples from each tooth measuring 1.2 x 1.2 x 5 mm were prepared. These sections were subjected to microtensile testing and failure values were recorded. The data were analysed by one-way anova and Tukey HSD tests. The PLVs, placed on the tooth surface that had received a dentine desensitizer and provisional restorations luted with resin cement (group 2), showed the lowest bond strength in all test groups. But no statistically significant differences were found between the bond strength of PLVs in control group (no provisional restorations) and group 1 (provisional restorations cemented with eugenol-free cement before final cementations). Scanning electron microscopic (SEM) examination of this study also showed that the bonding to enamel surface was better in control group and group 1 than group 2.

Implant-supported overdenture therapy: a 3- to 8-year prospective study.

Inflammatory changes in periimplant soft tissues and loss of alveolar bone can develop as in periodontal diseases. This clinical phenomena has been described as periimplantitis. Microorganisms such as Gram-negative anaerobic rods, spirochetes, and bacteroides that are seen in subgingival flora in periodontitis have also been found in sulcular microflora in periimplantitis. The purpose of this study was to evaluate periimplant tissue changes in totally edentulous patients who had implant-supported overdentures for 3 to 8 years (5-5.5 years) clinically from both a subjective and an objective point of view. The clinical parameters used in this study can be helpful in the evaluation of periimplant tissue health.

Microleakage of different cementation techniques in Class V ceramic inlays.

Microleakage between the restorative materials and the cavity walls of teeth remains a problem. The purpose of this study was to evaluate the microleakage around Class V ceramic inlay restoration using three different cementation techniques. Class V preparations were made on the buccal surfaces of 45 freshly extracted premolar teeth. The teeth were randomly divided into three groups of 15. In the first group, dentine bonding agent (DBA) (Clearfil Liner Bond 2V) was applied immediately after the tooth preparation (D-DBA). In the second group, DBA was applied to the prepared cavities while luting ceramic inlays (I-DBA). In the third group, DBA was not applied at either stage (No-DBA). Impressions were made and ceramic inlays (Ceramco II) fabricated and cemented in the Class V cavities. The restorations were stored in water at room temperature for 24 h. All restorations were thermocycled and then subjected to a dye penetration test. After sectioning, leakage at cavity/restoration interface was scored. Statistical analysis was performed using Kruskal-Wallis, Mann-Whitney U and Wilcoxon's signed tests. Results showed no significant difference among three different cementation techniques (P > 0.05). Microleakage at the dentine margins was greater than that at the enamel margins (P < 0.05).

The effect of dentin desensitizers on thermal changes in the pulp chamber during fabrication of provisional restorations.

The purpose of this study was to evaluate the effect of two dentin desensitizers on the pulp chamber temperature increase during fabrication of provisional restorations by a direct method. Sixty intact extracted mandibular third molars were prepared for a metal-ceramic complete crown. Then the teeth were randomly divided into three groups of 20 each. Group 1, no dentin desensitizer was used as the control group; group 2, a resin-based dentin desensitizer was selected; and group 3, the prepared teeth surfaces were coated with polyurethane cyanoacrylate adhesive. Each of the three groups was further divided into two polymerizing systems (autopolymerizing and a photopolymerizing) of 10 each. After insertion of the resin-filled matrix, the temperature change in the pulpal chamber was recorded with thermocouple connected to a data logger. anova indicated no significant differences for all combinations of desensitizing agents and curing methods (P > 0.05). When light cured composite or chemical curing acrylics were used to make temporary crowns, the presence of desensitizing agent did not reduce the temperature transmitted from the provisional material; the residual temperature rise transmitted was of such a magnitude as to cause concern regarding possible thermal injury to pulp.