In vitro Wear Resistance of Composite Resin Restorations against Ceramic Antagonists

Introduction: Occlusal contacts of direct composite restorations and antagonistic ceramics previously had relied on antagonist microtopography, contact mechanics and microstructure of the composite. Control of the ceramic surface condition following laboratory/chairside tweaks had been judged necessary to minimise composite wear for mixed-material occlusions. The purpose of this investigation was to assess the in-vitro wear resistance of a nanohybrid composite when opposed by ceramic antagonists representative of clinical conditions under controlled two-body sliding. Materials and Methods: Composite discs were constructed, standardised by successive polishing and opposed by three antagonist conditions: Glazed lithium-disilicate, polished monolithic zirconia and chairside-adjusted zirconia. Specimens were subjected to reciprocating sliding (50 N, 1.5 mm stroke, 1.2 Hz, 250,000 cycles) through artificial saliva under intermittent thermocycling. Primary outcome was composite volumetric loss; secondary outcomes were maximum vertical loss, roughness changes (ΔRα), ΔSα), steady-state coefficient of friction, facet area and qualitative wear mechanisms by scanning electron microscopy. Normality and homoscedasticity were screened; group differences were analysed by one-way ANOVA with Tukey tests and volumetric loss correlated by Pearson tests with ΔRa and friction. Results: Antagonist type significantly impacted volumetric loss ( P < 0.001$). Polished zirconia showed the lowest loss, followed by glazed lithium-disilicate, with adjusted zirconia being the highest. All pairwise differences were significant. Higher loss strongly correlated with increased friction and surface roughness (ΔRα). Conclusion: Antagonist surface state significantly influenced composite wear. Polished zirconia minimised roughness and loss, whereas adjusted zirconia increased friction and surface damage, highlighting the necessity of precise ceramic finishing for optimal occlusal stability.