Search

Objective: To evaluate the effect of the activation mode of adhesive cementation on push-out bond strength of fiber-reinforced resin posts to root canal dentin. Method and Materials: Forty mandibular premolars were endodontically treated and randomly divided into 4 equal groups. In groups G-1, G-2, and G-3, Single Bond (3M Espe) was applied and light polymerized for 20 seconds; in group G-4, Scotchbond Multi-Purpose Plus (3M Espe) was used as an autopolymerized adhesive. The dual-cure resin cement Rely X ARC (3M Espe) was light polymerized in G-2 and G-3 but not in G-1 and G-4. The translucent post Light-Post (Bisco) was used in G-3 and the opaque post Aestheti-Plus (Bisco) in the other groups. The roots were sectioned in 3 parts (cervical, middle, apical); each slice was submitted to the push-out test at a crosshead speed of 0.5 mm/min. Data were analyzed by analysis of variance and Tukey test (alpha = .05). Results: Light polymerization of both the adhesive and resin cement in G-2 led to significantly higher bond strength than in G-1, where only the adhesive was light polymerized. No difference was found between G-2 (opaque post) and G-3 (translucent post). The autopolymerized adhesive showed the highest bond strength in all root regions. The middle and apical post/root regions had similar bond strength, but it was significantly lower than that in the cervical region (P < .001). Conclusion: Bond strength to root dentin varied as a function of the activation mode of post adhesive cementation and post/root regions [ABSTRACT FROM AUTHOR]

This in situ study evaluated the Shore A hardness and phthalate concentration of 3 tissue conditioners (Coe-Comfort, Dura Conditioner, Softone) inserted into grooves on 9 maxillary dentures. Data were collected at baseline and after 3, 7, and 14 days of denture use. All materials showed a decrease in phthalate concentration and an increase in hardness over time, but the largest changes occurred during the first 3 days; 59% to 74% of the hardness variability was explained by the phthalate concentration. Overall, Coe-Comfort was softer and had less alteration in its phthalate concentration than Dura Conditioner and Softone up to day 7. [ABSTRACT FROM AUTHOR]

Purpose: To assess the magnitude and distribution of axial forces and bending moments in abutments as a function of cantilever length and inclination of implants. Methods: Ten metallic bars simulated frameworks of fixed implant-supported prosthesis over two master models with five implants: one with all implants straight and parallel (n=5) and one with the two distal implants tilted (n=5). Strain gauges were fixed on abutments to measure deformation when a 50N-load was applied on the cantilever at 10, 15, and 20 mm-distance from the distal abutment. Deformation values were transformed into axial force and bending moment and analyzed by ANOVA and Tukey test ([alpha] = 5%). Results: Comparing 10 mm- to 20 mm-cantilever, there was an increase of approximately 50% for axial force and of 70% for saggital bending moment. On the abutment adjacent to the cantilever, the axial force in the inclined model was 70% lower than in the straight model, and bending moments did not vary. Conclusion: The results suggest that the inclination of distal implants does not have any deleterious biomechanical effect on abutments of the tested models and may reduce the cantilever effect on force magnitude. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the cumulative effect of two protocols of microwave disinfection (Protocol 1: 690 W/6 min; Protocol 2: 345 W/6 min) on surface roughness (Ra) and baseplate adaptation of two denture resins polymerized by microwave energy (Onda Cryl) or hot water bath (QC-20). Methods: For Ra evaluation, rectangular specimens were fabricated and subjected to the following disinfection treatment (n=8/group): 1) Control (no disinfection), 2) Protocol 1, and 3) Protocol 2. Ra was measured using a profilometer at baseline (T0) and after two disinfection procedures (T1, T2) with a 7-day interval immersed in distilled water. To evaluate dimensional stability, maxillary baseplates were divided into the disinfection treatment groups (n=6), and adaptation was measured by weighing a silicon film reproducing the gap between resin baseplate and a metallic master model. Results: Ra had a significant interaction between type of resin/polymerization technique, disinfection treatment, and number of disinfection procedures (P<0.001). For Ra, Protocol 2 and control groups had similar increase of Ra over time, but Protocol 1 groups showed a significant decrease of Ra in T2. Baseplate adaptation was affected by a significant interaction between disinfection treatment and number of disinfection procedures (P<0.001), and Protocol 1 yielded the largest mean in T2. Conclusion: Onda Cryl displayed greater changes of Ra and adaptation than QC-20. Protocol 1 promoted overall damage to both types of denture resins after two disinfection procedures. [ABSTRACT FROM AUTHOR]