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Analysis of the Titanium-Zirconia Implant- Abutment Micro-Gaps

Background: The implant–abutment micro-gap has been investigated as a potential etiological factor for peri-implant diseases. Purpose: The aim of this study was to determine the marginal accuracy of different zirconia CAD/CAM abutments placed on external hex implants. Materials & methods: Twelve external hex implants (4.1mm) were used from the same company. The samples were divided into four groups: group 1) 4 mm diameter anti-rotational (AR) stock titanium abutments (n = 4); group 2) scanned (3Series, Dental Wings) and milled (RCS-1, Röders GmbH) 4 mm diameter zirconiaabutments (n = 4); group 3) scanned (3Series, Dental Wings) and milled (CNC 240, Lava) 4mm diameterzirconia abutments (n = 4); and, group 4) two piece 4.1 mm diameter stock abutments (Ti-base, CEREC, Sirona) (n=4), and torqued according with the manufacturer’s instructions (30Ncm, 20Ncm, 20Ncm & 35 Ncm, respectively). The samples were placed in a sample holder and segmented longitudinally. The implant-abutment gap was measured in 6 different pre-determined locations using optic microscopy. Results: One-way ANOVA statistical analysis was conducted and showed that the micro-gaps in the group 1 samples were not significantly different when compared with the micro-gaps in group 4 samples. However, a significant difference (p < 0.05) was found between the micro-gaps when using titanium abutments (groups 1 & 4) compared to zirconia abutments (group 3). Conclusion: Within the limits of this study, it was concluded that zirconia abutments cannot be milled with the same degree of precision as the metal abutments. The mechanical effects of marginal implant-abutment microgap and risk of microbial infiltration should be evaluated in clinical investigations. Keywords: Dental implant; Abutment interface;Microleakage.