Wear Performance of Monolithic Dental Ceramics against Enamel

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  • March 19, 2019
Creator
  • Ghuman, Taneet
    • Affiliation: School of Dentistry, Department of Operative Dentistry
Abstract
  • Wear of human enamel and the restorative materials is often a functional and anatomical concern when selecting a restorative material for clinical application. Ceramic restorations have been known to cause wear of opposing enamel. Demands for more biocompatible ceramics have led to the development of new generations of monolithic ceramic materials, but their wear performance has not been fully understood. Objective: To measure and compare enamel wear against monolithic ceramic materials (Lithium Disilicate and Zirconia) as a function of surface treatment (polished, glazed, polished then glazed). Additionally, the surface roughness (Ra) of the ceramic materials was measured before wear testing to evaluate the effect of surface treatment on the surface roughness. Materials and methods: The study included 10 flat specimens of lithium disilicate (polished), zirconia (n=10), (divided into polished, glazed, polished and then glazed). Enamel specimens were obtained from freshly extracted and caries free maxillary 1st premolars. Buccal cusps were standardized, mounted onto steel styli, stabilized with self-cure acrylic resin, and polished with a series of 400-, 600-, and 1200-grit SiC paper. The ceramic specimens comprised of standardized lithium disilicate (polished), zirconia (polished, glazed, polished then glazed) blocks (n=10). All ceramic specimens were wet-finished (pumice/polishing cloth), cleaned (ultrasonic bath/5min/distilled water), glazed and stored for 24hrs at 37°C. Before testing, the surface roughness of all ceramic specimens was measured using a non-contact 3D surface profilometer (Proscan 2000, UK). Enamel and ceramic specimens were mounted into brass holders and subjected to cyclic loading in a chewing simulator for 600,000 cycles with a vertical load of 20N onto ceramic specimens stabilized on a 2mm horizontal sliding platform at a frequency of 20 cycles/min. The test was conducted at 37°C using a continuous solution of 33% glycerin + 66% water for lubrication. Volume and depth loss (mm3) were determined, the 3D scans were superimposed with PROFORM software. Data was analyzed by ANOVA and Tukey post-hoc tests (p=0.05). Results: Wear Volume: Ceramics: there was no measurable wear loss on polished zirconia, significant material loss wear values were seen with other groups. Enamel demonstrates significantly greater wear when opposed with polished lithium disilicate, polished and then glazed zirconia and glazed Zirconia (p<0.0001) than polished zirconia specimens. Conclusion: Enamel showed wear when opposed to all ceramic groups. Enamel opposed to polished zirconia showed lower mean wear values than when opposed to polished lithium disilicate, polished and glazed zirconia, and glazed zirconia. Monolithic zirconia is wear-resistant. Glazed materials are rougher than polished materials even when glaze is applied to a polished material, causing notable wear of the opposing enamel. This study was supported in part by Ivoclar Vivadent.
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  • In Copyright
Advisor
  • Ritter, Andre
  • Donovan, Terence
  • Boushell, Lee
Degree
  • Master of Science
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2016
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