Differential hydrolytic degradation of dentin bonds when luting carbon fiber posts to the root canal

The purpose of the study was to evaluate the effect of water storage, adhesive system and root canal region on the hydrolytic degradation of dentin bonds to carbon fiber posts.

Fiber posts were bonded to the root canals using different adhesive systems and composites: SB1 XT group (Scotchbond 1 XT/RelyX ARC), OBF group (One Up Bond F Plus/Ionotite F), and AB2 group (All Bond 2/C&B) After water storage (10 days), all roots were sectioned into 1 mm beams and divided into coronal or apical group. The specimens were stored in water at 22-26 °C temperature for 15 or 60 days and tested for microtensile bond strength at a crosshead speed of 0.9 mm/min after the calculation of the bonding area. Statistical analysis was performed with ANOVA followed by Tukey test to detect differences between groups (α=0.05). SEM investigation was performed to determine the mode of fracture.

Bond strength at coronal and apical half showed significant differences between experimental groups both after 15 and 60 days of water storage. Premature failures were observed in 16-20% of specimens before storage in water.

For the bonding systems tested, clinicians should consider that bond strength inside the root canal at apical half is lower than at coronal half irrespective of the adhesive system. The adhesion within the root canal is possible for SB1 XT and OBF groups unlike the AB2 group where adhesion to root canal dentine is not reliable. Nevertheless, apical half represents the worst scenario in which is possible to obtain a durable adhesion.