Wear assessment of current aesthetic crowns compared with human enamel after two finishing procedures: In vitro study

Abstract

Background: Surfaces of ceramic crowns are modified several times before being exposed to wear in the oral cavity. Grinding and different finishing procedures may be associated with teeth wear due to increased surface roughness. Limited data is available with regard to the effect of polishing procedures on the surface roughness and wear behavior of ceramic crowns. This study was conducted to assess the influence of polished and polished-ground-repolished surface finish on the roughness and wear performance of three ceramic crowns. Methods: 36 natural 1st molar teeth were prepared using a CNC milling machine and classified into three groups (n=12/group): zirconia, E-max and hybrid ceramic (VITA ENAMIC) crowns. Each group was classified into two subgroups (n=6/subgroup): polished and polished-ground-repolished crowns. Natural molar teeth served as an unrestored control group (n=6). All samples were loaded into a chewing simulator for 100,000 cycles and subjected to 600 thermo-cycles in temperature changes to simulate changes in intraoral temperature. Natural maxillary 1st premolar teeth were collected and only buccal half (cusp) of sectioned tooth was used as antagonists. A profilometer was used to detect the roughness before and after masticatory cycles. The occlusal surface was analysed using a scanning electron microscope (SEM). Results: The E-max crown group had the highest mean surface roughness value (0.267µm) followed by VITA ENAMIC crown group (0.266 µm), while the lowest mean surface roughness value recorded for zirconia crown (0.257µm). The difference between these means was not significant. The polished-ground–repolished group had a higher mean surface roughness (0.266 µm) compared with the polished group (0.260 µm), which was not significantly different. Conclusions: All tested ceramic crowns showed surface roughness with values within acceptable clinical parameters (~0.2 µm). Additionally, intraoral polishing procedures could be considered a reliable technique for smoothing of zircona, E.max and VITA ENAMIC crowns after occlusal adjustment.