Actual adhesion state of direct resin composite restoration applied with resin core system

The purpose of this study was to examine the actual adhesion state of direct resin composite restoration applied with the resin core system. A standardized Class 2 MO core cavity was prepared in 60 human extracted lower first molars. Pretreatment for the cavity walls and resin core material filling of the pulp cavity were performed with Clearfil DC Bond＋DC core Automix (DC) or Clearfil Bond SE ONE + DC core Automix ONE (SE). Then, the coronal part of the cavity was restored with Clearfil AP-X. Restored specimens were divided into two groups (n=15): one with dynamic load stress (S+) and the other without the stress (S-). For the S+ group, dynamic load stress (16 kgf×3×105 times) was applied in water at 37℃. For the S- group, no stress was applied. The specimens were trimmed to standardized beam specimens, and micro-tensile bond strength (μ-TBS) to four intra-cavity dentin walls, gingival wall (G), pulpal-floor wall (P), coronal-axial wall (CA), and pulpal-axial wall (PA) were measured. The data was examined using ANOVA and Weibull analysis. The μ-TBS to G was significantly higher than that of the other walls except for the value of DC (S-) to P, regardless of dynamic load stress and resin core system. The influence of load stress was significant only for the μ-TBS to P. The Weibull modulus of G was significantly greater than that of the other dentin walls, regardless of the stress and the system. At both 10% and 90% probabilities of failure levels, the adhesion on the four dentin walls tended to require less stress to debond by dynamic load stress, regardless of the resin core system.