8th Dental Facial Cosmetic International Conference

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Effect of Cementation, Cement Type and Vent Holes on Fit of Zirconia Copings

The purpose of this in vitro study was to investigate the effect of cementation, cement type and vent holes on the marginal and internal fit of Zirconia (Zr) Copings. Materials and Methods: 100 extracted premolars were mounted in resin and prepared for Zr crowns. Samples were randomly divided into 5 groups (n=20): A=No Cementation; B=Cementation with Glass-Ionomer (GI); C=GI+Vent-Holes; D=Cementation with Resin Cement (RC); and E=RC+Vent-Holes. The copings were fabricated using Zirconia Blocks (ZenostarT, Wieland Dental, Germany) with a standardized cement space of 20µm. For Groups C & E copings were designed to have 0.5mm of Vent-Holes on the Buccal and Lingual Cusp Tips. The copings were tried on, cemented under load of 20 Newtons, thermocycled, re-embedded in resin and cross sectioned into mesial and distal halves. The copings were examined with 3D-Digital Microscope (HIROX, KH-7700, Tokyo, Japan) at 50X to200X magnification and the gaps or misfit were recorded at 9 predetermined points. Results: Mean gap recorded for non-cemented copings was statistically less than that for the cemented groups P<0.05 except vs Group E (RC plus vent holes). No statistical difference was observed among the cemented groups P>0.05. However, the fit of copings with vent holes was statistically better than without holes P<0.05. Conclusions: Marginal and Internal gap values designed in the software programs differed than the actual values measured for the non-cemented copings. Cementation process also influenced the fit of the Zr copings, the resin cement being the more accurate. The addition of vent-holes on the occlusal surface improved the fit. Keywords: Zirconia copings; Marginal fit; Internal fit; Zirconia Cementation; Vent-holes.

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