Restoration techniques and marginal overhang in Class II composite resin restorations.

摘要

OBJECTIVES: The objective of the study was to compare in vitro interproximal overhang formation of Class II composite resin restoration when using different matrix systems. METHODS: 240 lower left molar phantom head teeth with an MO-preparation were divided into 12 groups (n=20). In six groups a circumferential matrix (Tofflemire X-thin matrix, HaweNeos 1001-c, SuperCap) was used, combined with either a hand-instrument (PFI49 or OptraContact) or separation ring (Composi-Tight Gold). In the other six groups two sectional matrix systems were used (flexible and dead-soft), with three separation rings (Composi-Tight Gold, Contact Matrix, Palodent BiTine). Matrices were secured with wooden wedges and preparations were restored with composite resin Clearfil AP-X (Kuraray) placed and polymerized in increments. After matrix removal overhang was measured on a standardized digital macroscopic image in mm(2). For analysis a multiple linear regression model was used. RESULTS: Use of circumferential matrices resulted in less overhang than sectional matrices (-0.85 mm2, p<0.001). A flexible matrix led to less overhang than dead-soft matrices (-0.54mm2, p<0.001), and no difference was found between straight and pre-contoured matrices (p=0.945). The insertion of the OptraContact resulted in a much increased overhang of 2.54 mm2 (p<0.001). The Composi-Tight Gold and the Contact Matrix System rings resulted in less overhang, -0.69 and -0.68 mm(2), respectively (both p<0.001), whereas the Palodent BiTine ring did not. CONCLUSIONS: Use of circumferential matrices or sectional flexible matrices resulted in the least marginal overhang when combined with a Contact Matrix separation ring or a Composi-Tight Gold ring.