SEM analysis of in vivo formed dentin-composite micro-gap

Objectives: The objective of this study was to present SEM appearance of the micro-gap between dentin walls and composite material formed during eight months of in vivo function in patients. Methods: Occluso-mesial adhesive type cavities were prepared clinically in eight intact third molars, eight months before their extraction due to orthodontic indication, with signed patient's approval. All teeth were in full physiological function with their antagonists. Cavity depth was at least 2 mm in dentin beneath DEJ, in both occlusal and proximal cavity. Cavities were totally etched, and restored randomly with one of the four adhesive/composite systems: 1. ELS® + James 2 (Saremco, Switzerland), 2. Tetric Ceram + Excite (Vivadent, Liechtenstein), 3. ELS® + Excite, and 4. Pont 4 + Optibond Solo Plus (Kerr, Italy) – two cavities per system. Restorations were placed using “oblique incremental technique”, curing each layer for 40 sec with the same light curing device (Astralis 7, Vivadent, Liechtenstein). Final modeling and polishing was conducted using tungsten-carbide finishing kit (Kerr, USA), and silicone polishers (Diatech, Switzerland). Following extraction teeth were stored in deionized water at 370C, not longer than for 7 days before longitudinal mesio-distal sections through the middle of the cavity with a restoration were made, and then processed and observed on SEM (JEOL, JSM, 6460 LV). Results: All samples showed existence of cracks between dentin wall and composite restoration. Areas of intact bond were observed with enamel, but very seldom and short in length with dentin in cavities restored with ELS®, and Tetric Ceram. Cohesive, adhesive and mixed type of cracks, as well as broken resin tags were found in the same tooth sample, regardless adhesive/composite system clinically applied. Conclusions: In all tooth samples enamel/composite interface was intact. Different types of bond destruction with dentin was found regardless the material applied.