Comparative study of wear properties of CAD/CAM PEEK materials, resin ceramics and dental enamel under simulated chewing conditions

Objectives: To compare the impact-sliding wear properties of CAD/CAM polyetheretherketone (PEEK) materials and resin ceramics with dental enamel, and to investigate the corresponding wear mechanisms. Methods: Six CAD/CAM polymer materials were assessed in comparison with human tooth enamel. Hardness, modulus and roughness values of each group were measured, prior to wear testing in a chewing simulator (ballon-disc design, 49 N). Wear depth, volume loss and wear rate were analysed using a nanoindentation tester and an optical profiler. Wear scars were further examined by backscattered electron scanning electron microscopy to identify the tribo-mechanisms. Results: No significant difference in wear rate was found among BioHPP (R), BioPEAK (R) (two filler-containing PEEK compounds) and natural enamel, during chewing simulation. After 500,000 cycles, the former two materials exhibited lower wear depth and volume loss of material and the steatite antagonists, as well as smaller wear scars, than pure PEEK ShushijieTM, resin ceramics Vita ENAMIC (R) and LavaTM Ultimate, despite lower baseline hardness and elastic modulus than enamel. Of all the groups, BioHPP (R), a ceramic-filled PEEK compound, exhibited the greatest wear resistance and the least abrasiveness to the antagonist, comparable to enamel. PEEK materials can absorb the impact stress and undergo plastic deformation, which is different from the impactsliding wear mechanisms of resin ceramics. Conclusions: With increasing wear cycles, PEEK compounds with high filler densities showed more favourable wear properties, comparable to enamel; and formed a compacted wear debris layer, exhibiting self-lubrication, despite of three-body wear. Clinical significance: Within the limitations of our results, PEEK compounds are particularly suitable for pathological wear conditions in posterior regions.