Abstract

Objective:- This in vitro study compared the load necessary to cause porcelain failure on traditionally fabricated metal-ceramic crowns cemented to metal tooth analogues with two different types of margins.

Methods :- A sample size of 40 specimens were selected and divided in to two groups with 20 sample each. All the crowned specimens were embedded in autopolymerising resin. The acrylic resin should be approximately at 2 mm distance from the margins of prepared crowns. All polymethyl methacrylate resin blocks were ground flat to ensure that each specimen is secured and in correct alignment, when compressive forces were applied to the lingual-incisal line angle, at 130° to the long axis of the specimen until catastrophic porcelain fracture occurs.
Results:-The load at which porcelain fracture occurred on crowns fabricated with shoulder margin was 1742N and the load at which porcelain fractured occurred on crowns fabricated with chamfer margin was 946N.
CONCLUSION:- Astatistically significant difference was found between the loads at which porcelain from crowns with porcelain margins was fractured and crowns with metal collar margins was fractured(p< 0.01), with porcelain margins being the highest value.

Key words: Metal ceramic, Shoulder Margin, Chamfer Margin, Failure Load