ABSTRACT
OBJECTIVE: The objective of this study was to investigate, by simulation, the effect of conventional composite resin insertion techniques on cuspal deflection using bonded typodont artificial teeth. The deflection produced by a new low-shrinkage composite was also determined. MATERIALS AND METHODS: Sixty standardized MOD preparations on ivorine maxillary premolars were prepared: group A at 4 mm depth and group B at 6 mm depth. Each group was further subdivided according to composite insertion technique (n=6), as follows: 1) bulk insertion, 2) horizontal increments, 3) tangential increments, and 4) a modified tangential technique. Preparations were microetched, acid-cleaned, and bonded with adhesive resin to provide micromechanical attachment before restoration with a conventional composite (Spectrum TPH( 3 ), Dentsply). Two additional subgroups at 4 mm and 6 mm depth (n=6) were restored in bulk using low-shrinkage composite (Filtek LS, 3M/ESPE). All groups received the same total photo-polymerization time. Cuspal deflection was measured during the restorative procedure using two Linear Variable Differential Transformers attached to a data acquisition system. RESULTS: The average cuspal deflections for group A were 1) 40.17 ± 1.18 µm, 2) 25.80 ± 4.98 µm, 3) 28.27 ± 5.12 µm, and 4) 27.33 ± 2.42 µm. The deflections in group B were 1) 38.82 ± 3.64 µm, 2) 50.39 ± 9.17 µm, 3) 55.62 ± 8.16 µm, and 4) 49.61 ± 8.01 µm. Cuspal flexure for the low-shrinkage composite was 11.14 ± 1.67 µm (group A: 4 mm depth) and 16.53 ± 2.79 µm (group B: 6 mm depth). CONCLUSIONS: All insertion techniques using conventional composite caused cuspal deformation. In general, deeper preparations showed increased cuspal deflection-except in the case of bulk insertion, which was likely affected by decreased depth of cure. Cuspal movement using low-shrinkage composite was significantly reduced.
