Methods: Cylindrical Class I cavities were placed in premolars, having diameter: 3.5 mm and depth: 1.5 mm. A restorative procedure was performed according to manufacturers' instructions. The shrinkage in the vertical dimension (VD) was determined microscopically (x 400) expressed as the change-in-depth of the center of restorative area in the tooth cavity, before and immediately after light-activation, divided by the total restoration depth. The shrinkage in the horizontal dimension (HD) was measured as the marginal gap in tooth cavity immediately after light-activation. Specifically, a restored tooth was polished, the maximum marginal gap width was measured and then divided by the tooth-cavity diameter. The obtained data was expressed as a percentage and summed of percentages for all ten specimens. Statistical analyses (VD vs. HD) were conducted by Mann-Whitney U-test (p=0.01, N=10).
Results: Sum (%, N=10)
3M ESPE Kerr Shofu Tokuyama Kuraray GC
VD: 17.2 (0.4) 20.5 (0.6) 13.6 (0.4) 18.6 (0.4) 13.7 (0.5) 11.5 (0.4)
S S S S S S
HD 0.83 [3] 2.22 [0] 0.68 [3] 0.46 [5] 0.46 [5] 0.49 [6]
( ): S.D., [ ]: Number of specimens having no gaps, S: Significant difference.
Conclusions: There was a significant difference between VD and HD in the composite restorations.