ABSTRACT: This study aimed to assess the effect of post-cementation waiting time for core preparation of cemented cast posts and cores had on retention in the root canal, using two different luting materials. Sixty extracted human canines were sectioned 16 mm from the root apex. After cast nickel-chromium metal posts and cores were fabricated and luted with zinc phosphate (ZP) cement or resin cement (RC), the specimens were divided into 3 groups (n = 10) according to the waiting time for core preparation: no preparation (control), 15 minutes, or 1 week after the core cementation. At the appropriate time, the specimens were subjected to a tensile load test (0.5 mm/min) until failure. Two-way ANOVA (time versus cement) and the Tukey tests (P < 0.05) showed significantly higher (P < 0.05) tensile strength values for the ZP cement groups than for the RC groups. Core preparation and post-cementation waiting time for core recontouring did not influence the retention strength. ZP was the best material for intraradicular metal post cementation.
International Journal of Dentistry 01/2012; 2012:785427.
ABSTRACT: To investigate the effect of bleaching and staining solutions on roughness and shade changes in a nanofilled resin composite [Filtek Supreme (FS)].
FS specimens (n = 135) were light cured and separated into groups (n = 45) that were bleached with 10% carbamide peroxide (CP) agent or 16% or 35% hydrogen peroxide (HP). In the first two groups the bleaching gel was used for 4 hours a day, during 14 days, and for the third group in three sessions of 45 minutes. Each group was subdivided (n = 15) and immersed in coffee, red wine or distilled water for 3 hours a day during 40 days. The roughness values (Ra) and shade (parameter CLELab) were evaluated at baseline, after bleaching and after staining. The data was analyzed by ANOVA and Tukey test or Kruskal Wallis.
The effects on specimens varied depending on the bleaching product and staining solution. FS after bleaching and after staining presented higher roughness. In the evaluation of shade changes after bleaching, it was observed that resin color changed and that 35% hydrogen peroxide bleached the resin more than the others. After staining in three solutions, all specimens changed color and wine showed the higher staining capacity.
American journal of dentistry 08/2011; 24(4):245-9. · 0.76 Impact Factor
ABSTRACT: The authors conducted an in situ study of the influence of various time intervals after tooth bleaching with 35 percent hydrogen peroxide on the bond strength of resin-based composite restorations.
After selecting 20 participants, the authors randomly fixed enamel and dentin blocks onto the buccal surfaces of posterior maxillary teeth one week before performing tooth bleaching with 35 percent hydrogen peroxide. After the bleaching treatment, they removed one block of dentin or enamel and prepared it for the bond strength tests according to these time intervals: no bleaching treatment (controls), immediately after bleaching, seven days after bleaching, 14 days after bleaching and 21 days after bleaching.
The analysis of variance and Tukey test showed significant differences between times (P<.05), and shear bond strength values of resin-based composite to enamel and dentin were lower immediately after the bleaching treatment.
The authors found that 35 percent hydrogen peroxide reduces the bond strength to enamel and dentin and that it is necessary to wait seven days before performing adhesive restorative procedures.
The results of this study suggest that clinicians should allow seven days to elapse after completion of in-office bleaching with 35 percent hydrogen peroxide before placing adhesive restorations.
Journal of the American Dental Association (1939) 03/2010; 141(3):300-6. · 1.77 Impact Factor