Background: Several researches on tooth-supported crowns have shown that when cement space is increased, the marginal gap is reduced. However, there is no sufficient data measuring the effect of increasing the cement space on the vertical marginal gap of implant supported crowns.
Materials and methods: Thirty internal connection dummy implants and matching stock titanium abutments were coupled and implanted into auto polymerizing acrylic resin blocks. Three groups (n=10) of zirconia molar crowns with 3 different virtual cement space settings (40, 60, and 100 μm) were designed by using a CAD design software program. A digital microscope was used to measure the mean vertical marginal gap (MG) for each group, where a total of 120 measurements for each of the 3 groups (12 sites per crown and 10 crowns per group) were evaluated. all specimens were collected for thermomechanical aging which in this study simulated 3 months of chewing conditions. marginal gaps were remeasured as described before, One-way variance analysis and the post hoc Tukey pairwise comparison tests were used to analyze the data (α=.05).
Results: A significant difference (P<.001) was found between the MG values of the zirconia implant-supported crowns fabricated by using the 3 cement space settings. The smallest MG was obtained with the 60-μm setting as compared with the 40-μm and 100-μm settings.
Conclusion: The smallest MGs were obtained when a 60-μm cement space value was used (P<.001).