Three-dimensional evaluation of gap formation of cervical restorations

Objectives In some studies gap formation has been evaluated in just one section of the restorative. This in vitro study aimed to design a quantitative three-dimensional method for evaluation of the contraction gap in restoratives. Methods Cervical cavities were prepared on buccal, palatal or lingual surfaces in human extracted molars and were then filled with resin composites. Specimens were reduced every 100 μm in a direction parallel to the tooth axis, and perpendicular to the cavity floor from one proximal side to the other. The sequence of reducing the sections by 100 μm, image taking (250×) and observation of these images (maximal 2500×) were repeated. Three-dimensional images of the contraction gap were made using analytical software and the proportions of the interface with gap formation calculated. Results The mean proportions of the interface with gap formation of the self-etching system (Clearfil Liner Bond II Σ) was 41.7±6.3% and that of the self-priming system (Single Bond) was 38.2±3.9%; there was no significant difference. Conclusions Approximate three-dimensional images of the in vitro contraction gap could be drawn and the mean proportions of the interface with gap formation could be more precisely calculated than by previous methods.