Aim: The aim of this research was to study the effect of tooth convergence and internal surface treatment on the marginal fit of Zirconia and Lithium disilicate all-ceramic copings.
Materials and Methods: Two stainless steel dies were fabricated simulating a prepared maxillary premolar. The first die had 12°and the second 20° axial wall occlusal convergence. For each material (Zirconia and Lithium disilicate), Thirty non anatomical all ceramic copings were fabricated using inlab MC XL unit (15 copings on each die). For each group of taper, specimens were subdivided according to the technique of the internal surface treatment into three subgroup (5 copings each); air abrasion, tribochemical coating and acid etching. Cervical marginal accuracy was tested before and after cementation using a stereomicroscope.
Results: Taper 12° recorded statistically significant higher mean value than taper 20°. Acid etching recorded statistically significant lowest marginal gap mean value. Regardless to ceramic material, taper or cement, the marginal gap after cementation was statistically significant higher than before cementation (p<0.05)
Conclusion: Increasing the degree of taper lead to better marginal fit regardless the type of ceramic material. The marginal gap of e.max copings is better than that of zirconia in both before and after cementation. Copings treated with acid etching surface treatment show better marginal adaptation than tribochemical coating and sandblasting surface treatments regardless the type of ceramic material and degree of taper of the preparation.