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.

Wettability of 3 different artificial saliva substitutes on heat-polymerized acrylic resin.

STATEMENT OF PROBLEM: The prosthodontic problems faced by a patient with xerostomia are of great concern. To aid in retention, artificial saliva substitutes should exhibit good wettability on the denture base. PURPOSE: The purpose of this in vitro study was to evaluate the wettability of 3 different artificial saliva substitutes on heat-polymerized acrylic resin and to compare these properties with natural saliva and distilled water. MATERIAL AND METHODS: A total of 150 heat-polymerized acrylic resin specimens were prepared with 25×15×2 mm dimensions. The specimens were divided into 5 groups (n=30): human saliva, distilled water, Aqwet, Mouth Kote, and Stoppers 4. The advancing and receding contact angle values were measured by using a goniometer, and the contact angle hysteresis and equilibrium angle were calculated. One-way ANOVA and the Bonferroni multiple comparisons test were performed to determine the difference between contact angle values among the groups (α=.05). RESULTS: The means of the 5 groups differed significantly (P<.05). The comparison between human saliva and Aqwet showed no significant difference for advancing contact angle, receding contact angle, contact angle hysteresis, or equilibrium contact angle, while comparison between the remaining groups indicated statistically significant (P<.05) results. All 3 saliva substitutes used in this study (Aqwet, Mouth Kote, and Stoppers 4) had significantly better wetting properties than distilled water. CONCLUSIONS: Human saliva had the lowest advancing, receding, and equilibrium contact angle values and the highest angle of hysteresis on heat-polymerized acrylic resin. Aqwet had better wetting ability than the other artificial salivary substitutes tested and was comparable to the human saliva on heat-polymerized acrylic resin. All saliva substitutes have better wetting properties than distilled water.