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Advisory Committee Chair

Nathaniel C Lawson

Advisory Committee Members

Javed Amjad

Nejat Amir

Robles Augusto

Document Type

Thesis

Date of Award

2023

Degree Name by School

Master of Science (MS) School of Dentistry

Abstract

Background: In patients with restored dentitions, it is possible for crowns on opposing teeth to gradually wear each other through chewing and bruxism. Therefore, the wear of restorative materials used for dental crowns is an important mechanical property for their long-term clinical success. Lithium disilicate is a widely used dental ceramic due to its strength, machinability, and translucency. Due to the rising use of ceramic restorations, a comparison of the wear resistance of lithium disilicate against different ceramic crown materials is useful for the clinician when selecting a crown material to oppose an existing lithium disilicate crown. Objective: To compare volumetric wear of lithium disilicate against different ceramics (3 mol% yttria-stabilized tetragonal zirconia polycrystals zirconia, 5 mol% yttriastabilized tetragonal zirconia polycrystals, lithium disilicate glass-ceramic, feldspathic porcelain) and enamel antagonist. Methods: Forty (40) flat lithium disilicate (e.max CAD. Ivoclar Vivadent) specimens (n=8/antagonist material) were prepared by sectioning them into blocks (8mm x 4mm x 4 mm thickness) with a sectioning saw. The specimens were crystallized and mounted in a brass holder with acrylic resin. Specimens were wet polished down to 1200 grit SiC in a polishing wheel. For the antagonist, balls made of 3Y-TZP, 5Y-TZP, LDC, and FP were milled at an external laboratory. The ceramic materials, 3Y-TZP, 5Y-TZP, and e.max were polished with ASAP Indirect+ for 20 seconds each. Similarly, porcelain antagonists were polished with Dialite Feather Lite for 20 seconds each. The enamel cusps were sectioned from extracted human teeth, cleaned with pumice, and mounted into a steel hex screw with acrylic resin to be used as the enamel antagonist. A two-body wear test was performed using a ball-on-disc sliding wear device (UAB custom wear device, Birmingham AL) A 1.5 mm repeating impact/slide wear was conducted in 33% glycerin at 24 °C for 400,000 cycles with a frequency of 1 Hz. The applied load was 15N. Wear resistance was analyzed in a 3D optical non-contact profilometer (VR-5000) measuring volume loss on lithium disilicate specimens. Area loss of the antagonist specimens was analyzed by a digital microscope (VHX Keyence). In addition, Vickers hardness was measured, and surface morphologies were observed after the wear test using a scanning electron microscope. Statistical analysis was performed using 1- way ANOVA, and multiple pair-wise comparisons of means were performed using Tukey’s Post-hoc test. (p

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