Verena Preis1, Michael Schmalzbauer2, Dominique Bougeard2, Sibylle Schneider-Feyrer3, Martin Rosentritt3. 1. Department of Prosthetic Dentistry, Regensburg University Medical Center, Regensburg, Germany. Electronic address: verena.preis@ukr.de. 2. Institute for Experimental and Applied Physics, University of Regensburg, Germany. 3. Department of Prosthetic Dentistry, Regensburg University Medical Center, Regensburg, Germany.
Abstract
OBJECTIVES: To investigate the surface properties (roughness, composition, phase transformation) of monolithic zirconia specimens after dental adjustment procedures (grinding, polishing) and wear simulation. METHODS: Zirconia specimens (Cercon base, Cercon ht, DeguDent, G; n=10/material) were successively sintered, ground, and polished with an intraoral polishing kit in a three-step procedure. Sintered zirconia specimens with high surface roughness served as a reference. For each treatment step, wear simulations with steatite plates (d=10 mm) as antagonists were conducted as well as surface roughness tests (Ra), EDX analysis, and X-ray diffraction (XRD) measurements. SEM pictures were taken, and data were statistically analyzed (one-way ANOVA, post hoc Bonferroni, α=0.05). RESULTS: Grinding significantly (p=0.000) increased the roughness of sintered zirconia up to values of 1.36±0.11 μm (Ra). Polishing significantly (p=0.000) reduced Ra. The lowest roughness value after the final polishing step was 0.20±0.03 μm. Wear testing resulted in a further slight decrease of Ra. After the grinding procedure, SEM pictures showed deep grooves that were progressively smoothed by polishing. The EDX spectra showed that magnesium was transferred from steatite antagonists to zirconia by wear. In the XRD-patterns, monoclinic (m) peaks were observed after grinding and polishing. The maximum intensity ratio between the m (11-1) peak and the tetragonal t (111) peak decreased after the completion of all polishing steps. Wear did not induce phase transformation. CONCLUSIONS: Adequate polishing reduced the roughness of ground zirconia. Wear had little influence on roughness and no influence on phase transformation. CLINICAL SIGNIFICANCE: Careful polishing is recommended to keep surface roughness and phase transformation low.
OBJECTIVES: To investigate the surface properties (roughness, composition, phase transformation) of monolithic zirconia specimens after dental adjustment procedures (grinding, polishing) and wear simulation. METHODS:Zirconia specimens (Cercon base, Cercon ht, DeguDent, G; n=10/material) were successively sintered, ground, and polished with an intraoral polishing kit in a three-step procedure. Sintered zirconia specimens with high surface roughness served as a reference. For each treatment step, wear simulations with steatite plates (d=10 mm) as antagonists were conducted as well as surface roughness tests (Ra), EDX analysis, and X-ray diffraction (XRD) measurements. SEM pictures were taken, and data were statistically analyzed (one-way ANOVA, post hoc Bonferroni, α=0.05). RESULTS: Grinding significantly (p=0.000) increased the roughness of sintered zirconia up to values of 1.36±0.11 μm (Ra). Polishing significantly (p=0.000) reduced Ra. The lowest roughness value after the final polishing step was 0.20±0.03 μm. Wear testing resulted in a further slight decrease of Ra. After the grinding procedure, SEM pictures showed deep grooves that were progressively smoothed by polishing. The EDX spectra showed that magnesium was transferred from steatite antagonists to zirconia by wear. In the XRD-patterns, monoclinic (m) peaks were observed after grinding and polishing. The maximum intensity ratio between the m (11-1) peak and the tetragonal t (111) peak decreased after the completion of all polishing steps. Wear did not induce phase transformation. CONCLUSIONS: Adequate polishing reduced the roughness of ground zirconia. Wear had little influence on roughness and no influence on phase transformation. CLINICAL SIGNIFICANCE: Careful polishing is recommended to keep surface roughness and phase transformation low.
Authors: Taciana Emília Leite Vila-Nova; Isabelle Helena Gurgel de Carvalho; Dayanne Monielle Duarte Moura; André Ulisses Dantas Batista; Yu Zhang; Carlos Alberto Paskocimas; Marco Antonio Bottino; Rodrigo Othávio de Assunção E Souza Journal: Dent Mater Date: 2020-01-31 Impact factor: 5.304
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