Title:
Proximal marginal overhang of composite restorations in relation to placement technique of separation rings.

Abstract:
The aim was to investigate in vitro the marginal overhang in Class II composite restorations placed with various separation rings and placement techniques. A total of 180 Mesial-Occlusal [MO] preparations in artificial molar teeth were divided into nine groups (n=20). After placement of the sectional matrix, one of three ring systems was applied: Contact Matrix System (Danville Materials), Composi-Tight Gold (Garrison), and V-Ring (Triodent). In each group, rings were placed according to four different techniques (V-Ring placed with technique no. 2 only): 1) occlusally of the wedge, 2) on back end of the wedge, 3) between adjacent tooth and wedge, and 4) between treated tooth and wedge.After application of the adhesive resin, preparations were restored with composite Clearfil AP-X (Kuraray) and polymerized in increments. After matrix removal, overhang was measured on a standardized digital macroscopic image in millimeters squared. For analysis, analysis of variance and Tukey B were used (p<0.05).For the Contact Matrix System and Composi-Tight Gold ring, the different placement techniques had a statistically significant effect on the amount of marginal overhang (p<0.031). The V-Ring resulted in the least marginal overhang (p<0.001).None of the placement techniques and separation rings could completely prevent marginal overhang, and the placement technique has a significant influence on its occurrence.