Assessment of current adhesives in class I cavity: Nondestructive imaging using optical coherence tomography and microtensile bond strength

• Sealing performance was measured in five adhesives by optical coherence tomography.
• Sealing and bond strength performance within individual specimens were correlated.
• Interfacial defects increased after thermal aging.
• Increased interfacial defects tended to decrease the bond strength.
• Two- and three-dimensional images were useful in assessing bonding performance.

ObjectivesTo evaluate the sealing ability and the microtensile bond strength (MTBS) of different adhesive systems bonded to dentin in class I cavities.MethodsRound tapered dentin cavities (3-mm diameter, 1.5-mm height) prepared in extracted human molars were restored using composite resin (Clearfil Majesty Posterior) with two-step etch-and-rinse adhesive system (Adper Single Bond 2: ASB2), two-step self-etch adhesive (Clearfil SE Bond: CSEB), all-in-one adhesives (G-Bond Plus: GBP; Tri-S Bond Plus: TSBP), or no adhesive (Control), or bonded using low-shrinkage composite with its proper adhesive (Filtek Silorane, Silorane Adhesive System: FSS). After 24-h water storage or 10,000 cycles of thermal stress, the specimens were immersed into a contrast agent. Two and three-dimensional images were obtained using optical coherence tomography (OCT). The mean percentage of high brightness (HB%) at the interfacial zone in cross-sectional images was calculated as an indicator of contrast agent or gap at the interface. The specimens were then sectioned into beams and the MTBS measured.ResultsThe HB% (ASB2 = TSBP = CSEB < FSS = GBP) and MTBS (CSEB = ASB2, CSEB > TSBP = GBP = FSS, ASB2 > FSS) differed significantly among the adhesives. After aging, HB% increased for GBP and FSS specimens, and the MTBS decreased for FSS specimens (ANOVA, Tukey's post hoc, p < 0.05). The HB% and MTBS were significantly and negatively correlated (p = 0.002). Confocal laser scanning and scanning electron micrographs confirmed contrast agent infiltration within the gap.SignificanceThere was a significant correlation between sealing performance and bond strength of the adhesives in the whole cavity. After aging, the two-step systems showed equal or superior performance to the all-in-one and Silorane systems.