Evaluation of wear characteristics of different CAD/CAM restorative materials by increased chewing forces via chewing simulator

This study was conducted to compare wear characteristics of different CAD/CAM restorative materials and their enamel antagonists under increased chewing forces. The aim was to evaluate the patient-related and material-related factors to decide material selection with high clinical success. Extracted and divided cusps of healthy human third molars-against CAD/CAM materials as Vita Enamic®, a polymer-infiltrated ceramic network (PICN); GC Cerasmart®, a resin nanoceramic; Celtra® Duo, a zirconia- reinforced lithium silicate ceramic; and IPS e.max ZirCAD, a polycrystalline zirconia was exposed to chewing simulation (1.200.000 cycles, load 120 N, 5/55 ºC thermocycling). To determine the wear volume loss, each tooth cusp and material sample were scanned with 3D laser scanner and the images were overlapped using the Geomagic software. After measuring the initial surface roughness (Ra) of materials, Vickers hardness (GPa) and fracture toughness (K1C) were measured (1 kgf (≈ 9.807 N), 15 sec., 5 indentations). Wear characteristics were analysed by scanning electron microscope. IPS e.max ZirCAD group showed significantly lower volume loss (0.02 ± 0.01 mm3) than those of the three other groups (Vita Enamic, GC Cerasmart, Celtra Duo) (p=0.001, p=0.018 and p=0.005, respectively). The wear of cusp/Celtra Duo [0.59 mm3 (0.50 - 1.63 mm3)] was significantly higher than cusp/GC Cerasmart [0.17 mm3 (0.04 - 0.41 mm3)] (p=0.007). The surface hardness and fracture toughness of Vita Enamic and IPS e.max ZirCAD were decreased due to the thermocycling and mechanical loading (p=0.000 and p=0.008). Zirconia showed totally different wear mechanism than other materials due to its polycrystalline structure preventing microcrack formation. Zirconia may refer as an enamel-friendly material in patients with high chewing forces as it did not result in significant wear of enamel. It is observed that Celtra Duo exhibit an abrasive character against enamel antagonist by ejected zirconia crystals due to wear. GC Cerasmart might prevent the possible wear of enamel antagonist by its force absorbing manner.