The effect of food medium on the wear behaviour of veneering porcelain: An in vitro study using the three-body abrasion mode

Objectives: The present study examined the effect of food medium on the three-body wear behaviour of veneering porcelain derived from porcelain-fused-to-metal crowns. Methods: Seventy-four rectangular metal–ceramic specimens were prepared using Ceramco III as the veneering porcelain. After storage in distilled water at 37 °C for 2 days, the specimens were tested with a custom-designed chewing machine with a stainless steel ball as antagonist (350 N loads, 2.4 × 10 ⁶ cycles). Testing was performed using water, silica beads, poly(methyl) methacrylate beads, millet seed slurry, chicken slurry or celery slurry as abrasive medium. Wear analysis of the veneering porcelain was performed using a 3D profilometer after every 300,000 wear cycles and analysed with one-way analysis of variance and post-hoc pairwise comparison procedures. Worn surfaces were examined with scanning electron microscopy. Results: The wear curves of all experimental groups demonstrated three wear stages (running-in, steady wear and severe wear) with characteristic microstructure of worn surfaces. All the three food items selected in the present study (celery, chicken and millet seeds) had lower hardness compared with the veneering porcelain and produced less abrasion of the porcelain than a two-body wear system (water only). Abrasive wear produced with silica particles was the highest for the veneering porcelain. Conclusion: The wear process of veneering porcelain in porcelain-fused-to-metal restorations is affected by the type of food consumed during mastication. Clinical significance: Excessive abrasion may lead to premature failure of porcelain-fused-to-metal restorations. The importance of the wear behaviour of dental ceramic materials cannot be overstated. Three-body wear is an unavoidable consequence of oral function and occurs daily during eating. Understanding the effect of food particles on the wear behaviour of dental porcelain provides insight into the clinical performance and durability of these restorations.