Influence of microbrush on efficacy of bonding into root canals

Recently, several 'one-bottle' systems have been introduced for bonding into root canals. This study evaluated the influence of two brushes used as carriers of a primer-adhesive solution in the formation of resin tags, adhesive lateral branches and hybrid layer when used to bond fiber posts.

Twenty root canal treated teeth, extracted for periodontal reasons, were selected for this study. The samples were randomly divided into two groups of 10 samples each: Group 1: Microbrush + One Step + Dual Link resin cement; Group 2: One Step + Dual Link resin cement. The adhesive system and resin cement were used strictly following manufacturers' instructions. The priming-adhesive solution of the 'one-bottle' system was light-cured before placing the resin cement and the post. Twenty translucent fiber posts were used. Then, root samples were processed for SEM observation.

The adhesive system showed resin dentin interdiffusion zone (RDIZ), resin tag and adhesive lateral branch formation. Microscopic examination of restored interfaces of Group 1 showed a higher % (P < 0.05) of RDIZ than those found in samples of Group 2. In Group 2 samples RDIZ morphology was well detectable and uniform in the first two thirds of root canals while in the apical third the RDIZ was not uniformly present while in Group 1 RDIZ was visible at the apical third too. No statistically significant differences were found among the two groups coronally and at the middle third, while the apical third of Group 1 showed significantly more resin tags than in Group 2. The characteristic reverse cone shape of resin tags was always noted in the coronal and middle third of the root canals of both groups and at the apical third of Group 1. In the apical third of Group 2 root canals, the resin tags showed a less uniform morphology and a shorter length than those found in the other observed thirds.