The Effect of Occlusal Surface Preparation on Fracture Resistance of Zirconia Crowns Made by CAD\CAM System

Abstract

Backgroun & Aim: Because of the increase in cosmetic demands and the relentless pursuit to reach the best in both functional and cosmetic aspects, and with the continuous development of new materials in dentistry, metal-free ceramic restorations abounded as alternatives to PFM prosthodontics.They contain glass-ceramic, crystalline ceramic , but it is still used carefully in bridges and posterior prostheses due to its brittleness and low fracture resistance compared to metal.

It is compare the effect of occlusal surface preparation patterns on the fracture resistance of zirconia crowns manufactured by cad-cam technique.

Materials and methods: The research sample consisted of 40 zirconia ceramic crowns divided into the following groups:

Group A: traditional crowns (Bi-layered) and metal abutments with anatomical occlusal surface.

Group B: monolithic zirconia crowns and metal abutments with anatomical occlusal surface.

Group C: monolithic zirconia crowns and metal abutments with flat occlusal surface.

Group D: monolithic zirconia crowns and metal abutments with flat occlusal surface. contain a 0.5 mm mesiodistal groove.

Then the metal abutments have been printed by laser metal printer and after crowns cementation, the fracture resistance was studied by the general mechanical testing instrument then the Statistical analysis was done.

Results: the results showed that the monolithic zirconia crowns showed higher fracture resistance in comparison with double layers crowns when the abutments’ occlusal surfaces were prepared in an anatomical shape.  

occlusal surface preparation patterns didn’t affect the fracture resistance when using single-layer zirconia crowns.