Evaluation of the Fracture resistance of Machinable Versus Copy Milling Zirconia Restoration after Cyclic Loading

Document Type : Original Article

Authors

1 Fixed Prosthodontics Department, Faculty of Dentistry, Al Azher University Crowns and Bridges Department.

2 Ass. Professor of Crowns and Bridges Department Al-Azhar University.

3 Lecturer of Crowns and Bridges Department Al Azher University Assiut Branch

Abstract

Purpose: To evaluate the influence of, layering and mechanical fatigue on the Fracture resistance of Zirconia crown produced using CAD/CAM and copy milling systems. Materials and Methods: One metallic die was fabricated to simulate prepared upper premolar tooth (Tooth 24: with anatomic occlusal reduction,). Using universal milling machine Twenty crowns were fabricated using Prettau zirconia blank with a luting space settings of 60 μm. The fabricated crowns were grouped according to fabrication system in to CAD CAM and copy milling (N=20) as well as each group were divided again in to monolithic and by layered (n=10) Crowns were cemented using Panavia resin cement, then the fracture resistance were measured for half of samples using a instron device,. The other half of samples were subjected to cyclic loading (50 N load, 3700 cycles) and fracture resistance. Data were submitted to three-way ANOVA, and statistical significance was set at p < 0.05. Results: In monolithic groups (MO, CO), the highest fracture resistance was recorded with the CAD/CAM non-loaded samples, (1200.48±41.98N), while the lowest fracture resistance was recorded with the copy milled cyclic loaded samples, (1043±28.04N). In veneered groups (MV, CV), the highest fracture resistance was recorded with the CAD/CAM non-loaded samples, (800±41.57N), while the lowest fracture resistance was recorded with the copy milled cyclic loaded samples, (711±122.89N). Conclusion: CAD/CAM groups recorded statistically significant higher fracture resistance than copy milling groups. Monolithic groups recorded statistically significant higher fracture resistance than veneered groups. The cyclic loading (at 37,000 cycles) has no effects on the fracture resistance in all groups.
Al-Azhar Journal of Dental Science
Volume 21, Issue 5 - Serial Number 5
Supplement edition
December 2018
Pages 481-484

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