COMPARISON OF FAILURE LOADS OF METAL CERAMIC CROWNS WITH TWO DIFFERENT MARGINS-AN IN-VITRO STUDY.

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.