Morphological analysis of proximal contacts in class II direct restorations with 3D image reconstruction

To evaluate the proximal contact on class II composite restorations constructed using various restorative approaches by a morphological analysis.

Sixty plastic premolar teeth were prepared for class II cavities. These teeth were divided into six groups and restored using different materials and matrix systems. Two composite materials used were a microhybrid composite Filtek Z100 (3M/ESPE) and a packable composite P60 (3M/ESPE). Three interproximal matrix systems were two circumferential metal matrices (0.05 mm and 0.03 mm thin, respectively) combined with a Tofflemire retainer, and a pre-contoured sectional matrix system (Palodent). The contact morphologies of the restorations were visually inspected with regard to their buccolinugal and mesiodistal aspects. The contact tightness was measured by inserting different amounts of metal strips. For quantitatively morphologic analysis, three-dimensional (3D) scans of proximal contacts were performed. The results were analysed with two-way ANOVA and the Tukey test.

Under visual observation, contact surfaces in sectional matrix groups showed anatomic profile but concave in the centre, whilst the circumferential matrix groups showed flat profiles. The sectional matrix improved the contact tightness. The 3D analysis revealed that the matrix system was correlated with the contact morphology, since the sectional matrix generated significantly deeper and wider surface concavity.

All the interproximal matrix systems presented some deficiency in either the contact tightness or contours. Although the sectional matrix system enhanced contact tightness, it caused contact concavity by formation of interproximal marginal overhang. The quantitative morphologic analysis helps to examine improper proximal contact and the associated problems.