Ceramic materials are harder than enamel and unless polished or glazed, may wear the opposing tooth enamel. However many clinicians advocate using zirconia with no veneering feldspathetic porcelain to reduce the occlusal reduction of the preparation. However the wear of glazed and polished zirconia functioning against the enamel of the opposing teeth is unknown.
Objectives: To measure the wear of occlusal enamel cusp tips opposing polished or glazed zirconia surfaces. Methods: Eight flat rectangular ceramic blocks (7.00mmX11.00mmX6mm) with either a polished or glazed zirconia surface were placed in brass holders using self cured acrylic. The specimens were placed into a modified Leinfelder wear machine and tested against intact recently extracted human premolars (100,000cycles/75N/1.2Hz). Fifty micron PMMA beads were used as the third body media (15g beads/9g water). Polyvinyl siloxane impressions (Imprint light body/3M ESPE) of the teeth were taken before and after load cycling and poured with a low expansion dental stone (Silky rock/Whip Mix/Type IV). The dental stone was vacuum mixed (Vac-U-Mixer/Whip Mix) according to the manufacturer's instructions. Stone casts of the cusps of the premolars and ceramic material surfaces were scanned before and after wear testing using a non-contact 3D profilometer (PROSCAN2000/Scantron/England) to determine wear (volume loss) on the tooth enamel and restorative material. Images made after testing were superimposed over the initial image using ProForm software (Scantron/England). Data were analyzed with two factor ANOVA and Tukey/Kramer post-hoc test (p=.05).
Results: (Mean±SD).
Glazed | Polished | |
Enamel wear (mm3) | 0.4±0.2 | 0.9±0.4 |
The glazed ceramic surface produced significantly less enamel wear compared to polished ceramic surface (p=0.0157).
Conclusion: Within the limitations of this study, glazed ceramic surfaces should be preferred when the restoration antagonist is natural tooth. Supported in part by Glidewell Laboratories.