Influence of Delivered Radiant Exposure Values on Bonding of Fiber Posts to Root Canals

Purpose: To evaluate the effect of different radiant exposure values delivered to two simplified etch-and-rinse adhesive systems on push-out bond strength (PBS) of fiber posts to root canal, as well as nanoleakage (NL) and in situ degree of conversion (DC) within the hybrid layer. Materials and Methods: The roots of human premolars were endodontically prepared and divided into 6 groups according to the combination of the main factors adhesive/resin cement (2 commercial brands) and radiant exposure (4, 16, 48, and 288 J/cm2). The posts were cemented and the PBS tested at 0.5 mm/min (n = 7). The NL (n = 3) was evaluated using SEM after immersion of specimens in 50% silver nitrate. Micro-Raman spectroscopy was performed to determine the in situ DC (n = 2). Data were analyzed by three-way repeated measures ANOVA and Tukey's post-hoc test (5%). Results: PBS (MPa) showed a significant difference only for the middle third when an increase in radiant exposure from 4 to 16 J/cm2 or higher was used (p 0.05). The NL (%) decreased significantly with increasing radiant exposure from 48 to 288 J/cm2 in the middle and apical thirds when compared to lower radiant exposure (p 0.05). The radiant exposure of 288 J/cm2 significantly increased the DC (%) in the middle and apical thirds, compared the other radiant exposure values (p 0.05). Conclusion: The increase in radiant exposure delivered to the cervical third of root canals during post cementation improved the adhesive performance of simplified etch-and-rinse adhesive systems in the apical and middle thirds. Parole chiave: push-out bond strength, silver nitrate, degree of conversion, fiber posts, root dentin