Comparative Evaluation of Wear of Natural Enamel Antagonist Against Glazed Monolithic Zirconia Crowns and Polished Monolithic Zirconia Crowns: An In Vivo Study.

PURPOSE: To comparatively evaluate the amount of wear of natural enamel against a glazed full coverage monolithic zirconia crown and a polished monolithic zirconia crown at 6 and 12 months. MATERIALS AND METHODS: Thirty subjects within the age range of 18 to 35 years participated in this study. The subjects received a total of 60 single crowns, which were divided into two groups: (1) 30 glazed monolithic zirconia crowns opposed by natural enamel (group A); and (2) 30 polished monolithic zirconia crowns opposed by natural enamel (group B). Each subject received a crown from both groups, placed bilaterally in endodontically treated maxillary or mandibular first molars. An impression was made of the opposing arch at 24 hours, 6 months, and 12 months. The resulting casts were scanned with a 3D optical scanner. The recall scans were superimposed and compared to baseline scans using 3D AutoCAD software. A control group was included to compare the wear values to natural enamel against natural enamel. RESULTS: No significant difference (P = .855) was found in enamel wear between groups A (42.80 µm) and B (42.50 µm) after 6 months of use. However, a significant difference (P < .05) in enamel wear was found between group A (81.87 µm) and group B (71.43 µm) after 12 months of use. CONCLUSION: Glazed monolithic zirconia crowns cause more wear to the opposing enamel than polished monolithic zirconia crowns after 12 months of clinical use.

A Clinical Comparative Evaluation Of The Wear Of Enamel Antagonist To Monolithic Zirconia And Metal-Ceramic Crowns.

PURPOSE: To evaluate and compare the wear of natural enamel against a metal-ceramic and a monolithic zirconia crown, with the null hypothesis that there is no difference in the wear of enamel between antagonist metal-ceramic and monolithic zirconia crowns. MATERIALS AND METHODS: In 30 subjects (irrespective of sex and within the age range of 18 to 40 years), two bilaterally opposing molars (maxillary/mandibular) were prepared to receive monolithic zirconia or metal-ceramic crowns with feldspathic porcelain veneer. A polyvinyl siloxane impression of the opposing arch was taken at the time of cementation and 1 year after cementation. Casts were poured in type III gypsum and scanned, and the images were superimposed on each other. AutoCAD was used to calculate the difference between two images, which corresponded to the linear wear of the antagonist teeth. Statistical analysis of the data was done using one-way analysis of variance (ANOVA) and post hoc Tukey honest significant difference test for intergroup comparison. The P value obtained by one-way ANOVA was 1.1102e-16 (< .05), and by post hoc Tukey test was .001 (< .01). RESULTS: The mean wear of enamel against enamel was 14.8 ± 1.3 µm, enamel against metal-ceramic was 87.1 ± 18.3 µm, and enamel against monolithic zirconia was 59.4 ± 13.6 µm. The P values obtained; ie, 1.1102e-16 (one-way ANOVA) and 0.001 (post hoc Tukey), indicated that the difference in wear of the antagonist tooth between monolithic zirconia and feldspathic porcelain was significant. CONCLUSION: It can be concluded that monolithic zirconia causes less wear of the antagonist tooth than feldspathic porcelain.