Measurement of band displacement: A methodology to determine composite packability

Objective: A posterior composite should be able to maintain its shape when packed against a matrix band. The objective of this study was to develop an in vitro methodology to determine composite packability by measuring the displacement of a matrix band. Method and materials: The experimental setup consisted of a sectional matrix system secured for the restoration of an occlusodistal cavity preparation. The distance the band was displaced was measured from superimposed digital images. First, band displacements were measured under applied forces of 25, 50, and 75 g for different loading orders. Different forces resulted in different band displacements. Loading order significantly affected band displacements. Thus, the reproducibility of the experimental setup is ensured provided the band is replaced after each test. The cavity was filled with a universal composite (Z100, 3M ESPE) or a posterior composite (Filtek P60, 3M) at 37°C. Results: The band displacements were 32 ± 28 µm vs 107 ± 38 µm for ZI00 and Filtek P60, respectively. Conclusion: The present study proposed measuring band displacement as an in vitro methodology to determine the packability of dental composite. Based on the result, the posterior composite should help in forming contact better than the universal composite tested.