All ETDs from UAB

Advisory Committee Chair

Nathaniel Lawson

Advisory Committee Members

John Burgess

Amjad Javed

Keith Kinderknecht

Perng-Ru Liu

Document Type

Thesis

Date of Award

2016

Degree Name by School

Master of Dentistry (MDent) School of Dentistry

Abstract

Purpose: To compare the fracture load of monolithic Zirconia crowns and E-max crowns with different margin designs and to create a guideline for margin design for monolithic Zirconia crowns. Methods: Digital design of prep maxillary molar tooth was performed with TOC 20 degrees and occlusal reduction 1 mm and axial reduction 1 mm and two different margin designs (group 1: Shoulder 0.8mm group 2: Light Chamfer 0.3mm). Dies were milled using Ultra Crystal material. Monolithic Zirconia crowns were milled (n=9 in group 1 and n=8 in group 2). Crowns were cemented with Rely X luting Plus. The specimens were stored in deionized water in an incubator maintained at oral temperature (37°C) for 24 hours, tested in the Alabama wear machine for 400,000 cycles and thermocycled for 5,000 cycles (5,000 warm, 5,000 cold) and loaded to failure in the universal testing maching (Instron 5565). The null hypothesis was that there was no difference in the fracture strength of monolithic zirconia crowns with two margins types(0.3mm chamfer, 0.8mm shoulder) cemented with resin modified glass ionomer. Results: Two crowns in the 0.8mm shoulder group and one crown in the 0.3mm chamfer group broke during the fatigue test. There was no statistical difference between the two groups after the fracture test but the values on second group are higher. Conclusion: Within the limitations of this study there is no effect of margin design on fracture strength of zirconia crowns. The values of fracture strength of zirconia crowns are significantly higher than the average biting forces or clenching forces.

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