Effect of cavity depth and application technique on marginal adaptation of resins in dentin cavities.

The wall-to-wall polymerization contraction of two restorative resins was investigated in butt-joint dentin cavities prepared in extracted human teeth. The cavity diameter was 4 mm, and the cavity depth ranged between 0.5 and 3.0 mm. The width of the maximum marginal contraction gap was measured, using a light microscope, approximately 0.1 mm below the original free surfaces of the fillings. It was found that increasing the cavity depth from 0.5 to 3.0 mm did not influence the marginal contraction gap close to the free surfaces of the fillings. It was also found that a two-phase application technique, where the surface of the first layer was placed parallel to the free surface of the cavity, did not reduce the marginal contraction gap, while a two-phase technique with oblique layers resulted in approximately a 25% reduction.