Marginal and internal fits of zirconia single crown and Four-unit Fixed Dental Prostheses Substructures.

Abstract

Purpose: 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