Effect of Repair Systems on Dentin Bonding Performance

Objectives: The aim of this study was to investigate the influence of metal primer, silane coupling agent and phosphoric acid etching on dentin bonding performance of a 2-step self-etch adhesive system (Clearfil SE Bond 2, Kuraray Noritake Dental).
Methods: Human dentin surfaces were ground with #600-grit SiC and separated into four groups in accordance to pretreatment method: no pretreatment (CONTROL); 40% phosphoric acid K-Etchant GEL (K, Kuraray Noritake Dental); Alloy Primer (AP, Kuraray Noritake Dental); and Porcelain Bond Activator (PB, Kuraray Noritake Dental). Resin composite (Clearfil AP-X, Kuraray Noritake Dental) was placed and light cured for 40s (VALO Curing Light, high power mode, 1400 mW/cm², Ultradent). The specimens were sectioned into 1×1 mm beams and separated into 2 subgroups (n=20): 24h water storage at 37°C (24h) and 10000 thermal cycles (10k) of 5°C to 55°C with dwelling time of 30s each. The µTBS testing was done using a universal testing machine (EZ-SX, Shimadzu) at a crosshead speed of 1 mm/min. Specimens were also subjected to acid-base challenge to analyze the morphological difference at the dentin-adhesive interface by SEM (JSM-IT100, JEOL). The results were analyzed with two-way ANOVA and t-test with Bonferroni correction (a=0.05).
Results: There were no significant differences between the µTBS values of CONTROL, K and AP groups. However, statistically lower results were observed between PB and CONTROL (24h), PB and CONTROL, K and AP groups (10k), and PB before and after thermocycling (Fig.1). SEM images at the dentin-adhesive interface revealed that all groups produced an acid-base resistant zone (ABRZ). Erosion under ABRZ was observed in some cases for all groups, except for CONTROL. (Fig.2)
Conclusions: It is suggested that Porcelain Bond Activator could be a factor affecting negatively the dentin bonding performance. However, the ABRZ formed with erosion in all, but the control group.