Non-destructive 3D imaging of composite restorations using optical coherence tomography: Marginal adaptation of self-etch adhesives

Abstract Objectives To investigate the potential use of swept-source optical coherence tomography (SS-OCT) as a new tool to evaluate marginal adaptation of composite restorations in class I cavities. Methods Round-shaped class I cavities (3 mm diameter × 1.5 mm depth) were prepared on buccal enamel of bovine teeth with cavity floor located in dentine. The cavities were restored with a flowable resin composite (Clearfil Majesty LV) using two-step self-etch adhesive (SE Bond), all-in-one self-etch adhesive (G-Bond) or no adhesive (Control). The specimens were subjected to water storage (37 °C, 24 h) or thermal stress challenge (5000 cycles, 5 °C and 55 °C). 3D scans (4 mm × 4 mm × 2.6 mm obtained in 4 s) of the restoration were obtained using SS-OCT before and after immersion into a contrast agent. 2D images obtained from the 3D scans ( n = 30/group) were analysed to evaluate marginal adaptation. Area fraction of pixels with high brightness values at the interfacial zone was calculated using a digital image analysis software. The results were statistically compared with statistical significance defined as p ≤ 0.05. Results Wilcoxon signed ranks test showed that there was no statistically significant difference in the results of SS-OCT before and after infiltration of the contrast agent when a ranking transformation was applied on to the data ( p > 0.05). A significant positive linear correlation was found between the two SS-OCT images. Confocal laser scanning photomicrographs of samples cut after silver infiltration confirmed the presence of gap. Conclusions 3D imaging by SS-OCT can be considered as a non-invasive technique for fast detection of gaps at the restoration interface.