Interfacial Evaluation after Root Reinforcement with Composite and Fibre Post

Objectives: To evaluate the formation and quality of the bonding interface in experimentally weakened roots reinforced with adhesive restorative materials and quartz fibre posts, varying the light-exposure time of the composite resin used for root reinforcement.

Methods: Twelve extracted human maxillary central incisors teeth were used. The crowns were removed and the roots were endodontically treated. After post-space preparation, the roots were randomly assigned to four groups of three specimens each. In the experimental groups, root dentine was flared and adhesively (All Bond 2) restored with composite resin (Light Core) light-activated through a translucent fibre post (DT Light Post) for either: 40 s (group 1), 80 s (group 2) or 120 s (group 3). In group 4 (control), the roots were not experimentally weakened. Twenty-four hours after post cementation (Duo Link), the specimens were sectioned transversally in three slices (corresponding to the coronal, middle and apical regions of root restoration) and processed for scanning electron microscopic analysis to observe bonding interface formation, quality of hybrid layer, density of resin tags and presence of adhesive lateral branches using a four-step scale method.

Results: Formation of hybrid layer, resin tags and lateral branches were evident in all groups, independently of the region. However, the statistical analysis (Kruskal-Wallis, a=0.05) revealed that resin tag density was significantly lower in the apical region than in the coronal and middle regions (P<0.05). Furthermore, comparison of the flared/reinforced groups showed that the different irradiation times used for composite resin cure did not affect significantly the results (P=0.2139).

Conclusions: The light-exposure time did not influence the formation and quality of the bonding interface, but the root canal region played a significant role, with lower density of resin tags apically.