Adhesive improvement in optical coherence tomography combined with confocal microscopy for class V cavities investigations

The purpose of this study is to present a non invasive method for the marginal adaptation evaluation in class V composite restorations. Standardized class V cavities prepared in human extracted teeth were filled with composite resin (Premise, Kerr). The specimens were thermocycled. The interfaces were examined by Optical Coherence Tomography (OCT) combined with confocal microscopy and fluorescence. The optical configuration uses two single mode directional couplers with a superluminiscent diode as the source at 1300 nm. The scanning procedure is similar to that used in any confocal microscope, where the fast scanning is en-face (line rate) and the depth scanning is much slower (at the frame rate). Gaps at the interfaces as well as on the inside of the composite resin were identified. OCT has numerous advantages that justify its in vivo and in vitro use compared to conventional techniques. One of the main concerns was the fact that at the adhesive layer site it was very hard to tell the adhesive apart from material defects. For this reason the adhesive was optimized in order to be more scattering. This way we could make a difference between the adhesive layer and the material defects that could lead to microleakages.