Objectives: To ascertain how Feather edge and Chamfer finish line affect the marginal adaption of Zirconia reinforced lithium silicate glass-ceramic (ZLS) and Super transparent multilayered zirconia crowns (STML).

Materials and Methods: Two mandibular molar typodont acrylic teeth with their long axes aligned perpendicular to the surface of the block, stabilized at their apex and inserted in epoxy resin that auto-polymerizes. Simulate all ceramic crown preparation, One with a 0.2mm featheredge margin (F). The other one with a chamfer finish line of 0.5mm (C). A total of 40 monolithic crowns were constructed; 20 crowns from each material: Group ZLS for Zirconia reinforced lithium silicate ceramic (Celtra Duo) CAD/CAM blocks, (Dentsply Sirona), Group STMLZ for Super translucent multilayered zirconia (Katana, Kurary Noritake Japan) (intermediate translucency and strength).

Results: There was a significant interaction between the type of ceramic material and the finish line design on the marginal adaptation as indicated by ANOVA test. Feather edge finish line had better marginal adaptation with STML group than that of ZLS group. On the other hand, Chamfer finish line design for both ceramic groups showed no significant difference on marginal adaptation.

Conclusions: The marginal adaptation was obviously affected by the different margin designs as well as the type of ceramic material used. Feather edge finish line proved to have better marginal adaptation specially with Zirconia ceramics. Chamfer finish line design gave an acceptable marginal adaptation with both Zirconia and Zirconia reinforced glass ceramic.