[Studies on bonding interfaces of two dentin adhesives by scanning electron microscopy].

Objective: To purpose of this study was to investigate the microstructure and bonding mechanism of bonding interfaces of two current one-bottle dentin bond systems(Prime & Bond NT, PBNT; Prime one Mirage, P-One).

Methods: Fifteen extracted, caries-free human molars were prepared according to a modified method used for microtensile bond strength measurement. Each crown was divided into nearly equal halves with a 5 mm deep slot for accepting treatment of the two dentin bond systems, respectively. After 24 h storage in distilled water at 37 degrees C, the bonded teeth were subjected to two treatments: 5 teeth were observed by and tested for microtensile bond strengths without further treatment and 10 teeth were thermocycled(2400 cycles, between 5 degrees C and 55 degrees C) prior to SEM observation and bond strength testing. Hour-glass shaped microspecimens with a thickness of approximately 0.5 mm were cut from each tooth and used for SEM observation and microtensile bond strength measurement.

Results: A typical resin-infiltrated zone (hybrid layer) with a thickness of 3-5 microns and well-formed cone shaped resin tags that penetrated the dentinal tubules were clearly observed at the resin-dentin interfaces in the two bond systems. There were multiple lateral branches of tubular resin tags that interconnected to form a micro-network of resin. No evident differences in SEM images between the two bond systems as well as between thermocycling and without thermocycling in each bond system were found.

Conclusion: PBNT and P-One provided good resin infiltration, producing a three-dimensional interlocking micro-network of resin tags in the dentin tubules with multiple lateral branches that penetrate the intertubular dentin, which positively influenced the adhesion between dentin and the two bond systems.