Optical Quantification of Microgaps at Dentin-Composite Interface

Abstract

Objective. Microgap formation between polymer-based resin system and teeth surfaces is undetectable by conventional x-rays. Therefore, this in vitro study was designed to assess the adaptation of polymeric dental fillings and microgap formation at the tooth floor using cross-polymerization optical coherence tomography (CP-OCT). Materials and Methods. Class-I cavities (4 mm diameter × 1.5 mm depth) were prepared in twenty extracted molar teeth and divided into two groups: ESQ and DI (n = 10). All groups were bonded with Tetric-N Bond universal (Ivoclar/Vivadent) in selective etching mode. Then, each group was restored with either Estelite ∑ Quick dental composite (ESQ; Tokuyama Dental) or IPS Empress Direct (DI; Ivoclar/Vivadent) in bulk filling technique. After 24 h, all groups were immersed in a contrasting medium, ammoniacal silver-nitrate, for 24 h, followed by photo-developing solution for 8 h. Later, all groups were subjected to CP-OCT tomographic scans to examine microgaps and composite adaptation at the cavity floor at intervals of 0.25 mm. Analysis of CP-OCT raw data after conversion into two-dimensional images was carried out with the aid of image analysis software (ImageJ). Results. A Mann-Whitney test showed a statistically significant difference in gap formation between the two groups (p < 0.001), with greater microgaps being perceived as high signal intensities in the form of bright clusters at the cavity floor in ESQ group. Conclusion. CP-OCT is a useful diagnostic tool that can be used to observe the microgaps under composite restorations. Regardless of the factors affecting gap formation, less gap formation was observed in the group that shared the same polymer formula from the same manufacturer.