An in vitro study on the use of circumferential matrix bands in the placement of Class II amalgam restorations.

Objective: To compare the effectiveness of a disposable metal matrix band system and the Siqveland matrix system in the restoration of a Class II preparation with amalgam. To assess the difference in amalgam overhang produced between the two systems in vitro.

Methods: A right maxillary first premolar with a Class II cavity preparation was duplicated in acrylic to produce a standardized cavity. Forty acrylic teeth were individually mounted in a hand-held model of an upper right quadrant and restored with amalgam by twenty dentists. Each dentist restored two replica teeth with amalgam; one using the Omni-matrix system and the other using the Siqveland matrix system. All 40 restored teeth were individually mounted on a standardised jig, viewed under a microscope, photographed and overhangs, if present, measured using Image ProPlus 4.0. A comparison of the overhangs produced by the two systems was analysed using a paired sample t-test.

Results: An overhang was present in all cases. There was a significant difference in the size of the overhangs produced by the two different matrix systems (p-value 0.036). The Siqveland produced a larger overhang than the Omni-matrix system.

Conclusion: A commonly used matrix band (Siqveland), when compared to a newer, disposable system (Omni-matrix), was found to result in consistently larger overhangs during the restoration of class II preparations with amalgam. As Omni-matrix is a disposable system, the potential for cross-contamination is removed and it can, therefore, be considered a suitable replacement for the non-disposable Siqveland matrix system.