All ETDs from UAB

Advisory Committee Chair

Daniel Givan

Advisory Committee Members

John Burgess

Keith Kinderknect

Perng-Ru Liu

Document Type

Thesis

Date of Award

2014

Degree Name by School

Master of Dentistry (MDent) School of Dentistry

Abstract

Purpose: The influence of the vertical abutment positions on the retention of a three-unit implant supported cantilevered FPD restoration was measured and compared. Methods: The study included four groups (n=10) of cantilevered FPDs restorations, fabricated of monolithic zirconia. Prefabricated titanium implant abutments were used and connected to their analogs. The analogs were fixated on a split mold and their vertical position was adjusted on a 2 mm bases depending on the group, resulting also to an alteration of the occlusal thickness of the restorative material. The prosthesis were cemented to the abutments with Rely X Luting Plus resin modified glass ionomer and then loaded on the cantilevered pontic to 400,000 cycles at 70N at a rate of 40cycles/minute. A lateral slide of 2mm towards the buccal surface was also applied. Upon completion of the fatigue testing the analogs were individually pulled from the prosthesis and the maximum pulling strength in newtons was recorded. Results: During the cyclic loading, zirconia and screw factures were observed and recorded. One-Way and Two-Way ANOVA was used to compare the retentive values of the groups and no statistical difference was found. The group with the thinnest occlusal thickness of the zirconia showed a large number of screw fractures and couldn't be compared. Conclusions: Monolithic Y-TZP showed a success rate of 97.5% after completion of the fatigue testing. Increasing the occlusal thickness of the material resulted to a better stress distribution on the prosthesis. Alterations of the abutments vertical position will affect the axis of rotation and a trend was observed for the group where the abutment farthest to the pontic was on a higher vertical position to have better retentive values. The slide motion created a more complex biomechanical system and no conclusions could be drawn regarding the most favorable cantilevered design.

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