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Publication Open Access Gap comparison between single crown and three-unit bridge zirconia substructures.(2014-08) Chuchai Anunmana; ชูชัย อนันต์มานะ; Chanavut Asvanund; ชนวุตม์ อัศวนันท์; Masnisa Charoenchitt; Chuchai Anunmana; ชูชัย อนันต์มานะ; Mahidol University. Faculty of Dentistry. Department of ProsthodonticsPURPOSE To compare marginal and internal gaps of zirconia substructure of single crowns with those of three-unit 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 ± 0.4 µm and 46.5 ± 0.5 µm for single crown and 3-unit bridge substructure respectively. For molar substructure the mean ± SD of marginal gap was 48.5 ± 0.4 µm and 52.6 ± 0.4 µm for single crown and 3-unit bridge respectively. The largest gaps were found at the occlusal area, which was 150.5 ± 0.5 µm and 154.5 ± 0.4 µm for single and 3-unit bridge premolar substructures respectively and 146.5 ± 0.4 µm and 211.5 ± 0.4 µm 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.Publication Open Access Marginal and internal fits of zirconia single crown and Four-unit Fixed Dental Prostheses Substructures.(2015-09) Kulnaree Charukietkajorn; กุลนรี จารุเกียรติขจร; Chuchai Anunmana; ชูชัย อนันต์มานะ; Chuchai Anunmana; ชูชัย อนันต์มานะ; Mahidol University. Faculty of Dentistry. Department of ProsthodonticsPurpose: To compare marginal and internal gaps of zirconia single crown substructures with those of four-unit fixed dental prostheses substructures. Materials and Methods: A standard Co-Cr model of maxillary first premolar and maxillary second molar abutments was made. Twenty polyether impressions of the standard model were taken and subsequently poured with type-IV dental stone. Zirconia substructures were fabricated as premolar and molar single crowns (Cr, n=10) and four-unit bridges (Br, n=10) using LAVA™ Zirconia system. The gaps between substructures and their standard abutments were evaluated using silicone replica technique. Twenty-two different points were measured along the marginal and internal surfaces. The differences of the gap widths between single crown and four-unit bridge substructures were analyzed using Mann Whitney U-test (α=0.05). Results: There was significant difference of marginal gap between Cr and Br groups at mesial marginal gap of molar (30±44 and 112±19 µm for Cr and Br, respectively). For the internal gaps, mid-occlusal point revealed the largest gap. No significant difference of internal gaps between Cr and Br groups was observed except at some points of mesial chamfer area of molar (123±18 and 218±33 µm for Cr and Br, respectively) and at buccal axial wall of premolar (45±15 and 76±47 µm for Cr and Br, respectively). Conclusions: The differences between the gaps of zirconia single crown and those of four-unit bridge substructures were found at the mesial side of molar marginal area. Most of internal gaps of single crown substructures did not significantly differ from those of four-unit bridge substructures