Comparative Evaluation of Wear of Natural Teeth and Crown Materials Opposing Metal, Metal-Ceramic, and Zirconia Surfaces: An In Vitro Study

Background The increasing demand for aesthetic dentistry has led to widespread use of zirconia and metal-ceramic restorations. Although zirconia demonstrates superior mechanical properties and fracture resistance, the wear behaviour of restorative materials against natural enamel and opposing restorations remains a critical clinical consideration. Objective To comparatively evaluate the surface and volumetric wear of natural teeth, metal-ceramic crowns, and zirconia crowns when opposed by metal, metal-ceramic, and zirconia surfaces under standardised in vitro conditions. Materials and methods Ninety freshly extracted human premolars were randomly allocated into three groups (n = 30): natural teeth, metal-ceramic crowns, and zirconia crowns. Each group was further subdivided (n = 10) according to opposing disc material (metal, metal-ceramic, or zirconia). Specimens were mounted in acrylic resin and subjected to wear testing using a pin-on-disc apparatus under a constant 2 kg load for 10 cycles of one-hour duration with continuous distilled water irrigation at 37°C. Surface and volumetric wear were measured after testing. Statistical analysis was performed using one-way analysis of variance (ANOVA) with a significance level set at p < 0.05. Results Significant differences in both surface and volumetric wear were observed among groups (p < 0.05). Metal-ceramic antagonists produced the highest surface wear across natural teeth (177.2 ± 40.4), metal-ceramic crowns (181.3 ± 37.6), and zirconia crowns (141.4 ± 56.7). Metal discs demonstrated the lowest surface wear in all categories. Volumetric analysis revealed that zirconia opposing surfaces consistently resulted in the least material loss. Conclusions Wear behaviour varied significantly depending on restorative and opposing material combinations. Metal-ceramic antagonists generated the greatest wear, whereas zirconia surfaces demonstrated comparatively favourable and enamel-compatible wear characteristics. Polished zirconia may represent a clinically acceptable balance between aesthetics and functional durability.