Gap comparison between single crown and three-unit bridge zirconia substructures

Abstract

Purpose: To compare marginal and internal gaps of zirconia substructure of single crowns with those of threeunit fixed dental prostheses. Materials and methods: Standardized Co-Cr alloy simulated second premolar and second molar abutments were fabricated and subsequently duplicated into type-III dental stone for working casts. After that, all zirconia substructures were made using Lava™system. Marginal and internal gaps were measured in 2 planes (mesial-distal plane and buccal-palatal plane) at 5 locations: marginal opening (MO), chamfer area (CA), axial wall (AW), cusp tip (CT) and mid-occlusal (OA) using Replica technique. Results: There were significant differences between gaps at all locations. The mean ± SD of marginal gap in premolar was 43.6 ± 0.4μm and 46.5 ± 0.5μm for single crown and 3-unit bridge substructure respectively. For molar substructure the mean ± SD of marginal gap was 48.5 ± 0.4μm and 52.6 ± 0.4μm for single crown and 3-unit bridge respectively. The largest gaps were found at the occlusal area, which was 150.5 ± 0.5μm and 154.5 ± 0.4μm for single and 3-unit bridge premolar substructures respectively and 146.5 ± 0.4μm and 211.5 ± 0.4μm for single and 3-unit bridge molar substructure respectively. Conclusion: Independent-samples t-test showed significant differences of gap in zirconia substructure between single crowns and three-unit bridge (P<.001). Therefore, the span length has the effect on the fit of zirconia substructure that is fabricated using CAD/CAM technique especially at the occlusal area. © 2014 The Korean Academy of Prosthodontics.