Microgap Between Zirconia Abutments and Titanium Implants

Purpose: The aim of this study was to evaluate in vitro the microgap between different zirconia abutments and their titanium implants. Materials and Methods: Four systems were evaluated: Procera zirconia (Nobel Biocare) (Nb), Cercon Balance Anterior (Dentsply Friadent) (Ba), ZirDesign (Astratech) (Zd), and Straumann Cares ceramic (Straumann) (Ca). Five assemblies were assessed for each system. The assemblies were embedded in epoxy, cut along their long axes, and polished. Scanning electron microscopic observations were made along the first 100 µm of the gap on each side at maximal magnification. Images were combined and gap measurements were made 10 µm apart. A two-way analysis of variance was performed on the data. Results: Scanning electron micrographs showed a mean marginal microgap of 0.89 µm (SD 1.67) for all assemblies. Significant differences (P .001) were observed between mean (± SD) microgap measurements of the four tested systems: Ba = 0.38 ± 0.28 µm; Zd = 0.55 ± 0.23 µm; Nb = 1.83 ± 3.21 µm; Ca = 0.90 ± 0.59 µm. The mean microgap of the first 20 µm of the outer region (1.66 µm) was significantly (P .001) larger than the mean microgap (0.56 µm) of the inner region (30 to 100 µm). Conclusions: Within the limitations of this study, the mean microgap observed for all tested systems was less than 2 µm. For each system, the microgap decreased quickly from the outer region to the inner. The mean gap was larger for flat-to-flat connection systems, compared to internal-connection systems with a conical interface. These results demonstrate smaller microgaps compared to those described in the literature for titanium abutments. The precise fit of these abutments could lead to better biologic and biomechanical behavior. Keywords: dental implants, implant abutments, microgap, zirconia