Long-term regional bond strength of three MMA-based adhesive resins in simulated vertical root fracture

The purpose of this study was to investigate bond durability of MMA-based adhesives to root dentin in a simulated complete vertical root fracture (CVRF). The fractured fragments of human premolar root were reattached using Super-Bond C&B (SB; Sun Medical), M-Bond or M-Bond II (MB or MB II; Tokuyama Dental). After storage for 1 day, 1 month, 6 months and 1 year, the reattached specimens were subjected to microtensile bond strength (µTBS) test at cervical and apical regions. Results showed that µTBS was significantly higher to cervical dentin than to apical dentin in MB and MB II, but not SB (p<0.05). Significant decrease in µTBS was found for MB and MB II after 1 year, whereas no significant difference was found for SB (p<0.05). Analysis of failure mode by SEM indicated differences over time. In conclusion, significant differences were found in the regional bond durability among MMA-based adhesives used to restore CVRF, that may lead to different clinical performances.