All ETDs from UAB

Advisory Committee Chair

Gregg M Janowski

Advisory Committee Members

Perng-Ru Liu

Milton E Essig

Robin D Foley

Jack E Lemons

Gregory B Thompson

Document Type

Dissertation

Date of Award

2011

Degree Name by School

Doctor of Philosophy (PhD) School of Engineering

Abstract

The purpose of this investigation was to study three aspects which have been shown to limit clinical applications of yttria-stabilized zirconia (Y-TZP) for dental restorations. Mechanical property and structural changes due to low-temperature degradation (LTD) of Y-TZP led to increased surface roughness and monoclinic phase fractions, with a concomitant decrease in hardness and modulus. Yttria content and flexural strength were unchanged and phase transformation proceeded from the surface into the bulk of the material. The optical properties of Y-TZP, IPS e.max® CAD (IEC), and feldspathic por-celain (FP) laminate veneers showed that the underlying color of try-in pastes (TP) af-fected the color difference for different regions of IEC and FP veneers (cervical and body region). The IEC veneers were affected more by TP color than were FP veneers. The Y-TZP veneers were not affected by the color of the TP or the composite resin abutment (CRA) color. No effect of the color of the CRA was found for the overall color of all veneers except at the cervical region for FP veneers. However, there was an effect of different colors of TP on the color coordinates of the overall color for all the veneers. The mechanical properties of these three laminate veneers materials were studied for two designs, i.e., incisal overlapped preparation (IOP) and three-quarter preparation (TQP). No effect of preparation design on the mean failure load of Y-TZP and IEC veneers was found and material type did not affect failure load for a given design except for IEC ve-neers which had a higher failure load than FP for the IOP design. The IOP design, Y-TZP and IEC veneers showed more failure by fracture of the CRA, while FP veneers fractured at the incisal region. The TQP design, Y-TZP veneers showed more failures by complete debonding, whereas the IEC and FP veneers showed more fractures of the CRA. TheY-TZP veneers showed the lowest number of fractures and highest complete debonding, while the FP veneers showed the highest number of fractures and lowest occurrence of complete debonding.

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