Evaluation of Interfacial Morphology and Marginal Leakage of a Newly-developed HEMA-free One-bottle One-step Adhesive System

Abstract

This study aimed to evaluate a newly-developed HEMA-free one-step adhesive system, G-bond Plus® (GC, GBP), regarding the ultrastructural features of tooth-adhesive interfaces and marginal leakage. G-Bond® (GC, GB), Bond Force® (Tokuyama Dental, BF) and Clearfil tri-S Bond® (Kuraray Medical, TS) were used as reference materials. Enamel and dentin surfaces of extracted human molars were treated with one of the four adhesive systems and then observed by either scanning electron microscopy (SEM) or confocal laser scanning microscopy (LSCM). For the assessment of marginal leakage, class V cavities prepared in extracted human premolars were treated with one of the four adhesive systems and filled with flowable resin composites (n=5). After 7 days of storage in water at 37℃, specimens were subjected to mechanical load cycling, immersed in a 50% silver nitrate solution for 24h, and then sectioned bucco-lingually. The degree of silver penetration along enamel- and dentin-adhesive interfaces was scored under a stereomicroscope and then the interfaces were observed with SEM. Enamel prism ends and dentinal tubule openings were more evident in GBP- and TS-treated specimens compared with those treated with GB and BF; LSCM also demonstrated that GBP and TS caused deeper step formation along the boundary between treated and untreated regions. The degree of silver penetration along enamel- and dentin-adhesive interfaces was larger in GBP and TS than in GB and BF, although no statistically significant difference was found (p>0.05, Kruskal-Wallis test). SEM also demonstrated that gap formation along the enamel-adhesive interface was more frequent in GB than in GBP, TS and BF, and that gap formation and silver penetration along the dentin-resin interface were more often seen in GB and BF than in GBP and TS. These findings suggest that the self-etching potential and sealing ability of GBP are comparable to or better than those of GB, BF and TS.