Effect of Fabrication Technique on the Microgap of CAD/CAM Cobalt-Chrome and Zirconia Abutments on a Conical Connection Implant: An In Vitro Study

The aim of this in vitro study was to investigate the microgaps at the implant-abutment interface when zirconia (Zr) and CAD/CAM or cast Co-Cr abutments were used. Methods: Sixty-four conical connection implants and their abutments were divided into four groups (Co-Cr (milled, laser-sintered and castable) and Zirconia (milled)). After chewing simulation (300,000 cycles, under 200 N loads at 2 Hz at a 30 degrees angle) and thermocycling (10,000 cycles, 5 to 50 degrees C, dwelling time 55 s), the implant-abutment microgap was measured 14 times at each of the four anatomical aspects on each specimen by using a scanning electron microscope (SEM). Kruskal-Wallis and pair-wise comparison were used to analyze the data (alpha = 0.05). Results: The SEM analysis revealed smaller microgaps with Co-Cr milled abutments (0.69-8.39 mu m) followed by Zr abutments (0.12-6.57 mu m), Co-Cr sintered (7.31-25.7 mu m) and cast Co-Cr (1.68-85.97 mu m). Statistically significant differences were found between milled and cast Co-Cr, milled and laser-sintered Co-Cr, and between Zr and cast and laser-sintered Co-Cr (p < 0.05). Conclusions: The material and the abutment fabrication technique affected the implant-abutment microgap magnitude. The Zr and the milled Co-Cr presented smaller microgaps. Although the CAD/CAM abutments presented the most favorable values, all tested groups had microgaps within a range of 10 to 150 mu m.

Automated summary

The study found that milled Co-Cr abutments had the smallest microgaps, followed by Zirconia abutments, while sintered Co-Cr and cast Co-Cr abutments had larger microgaps. The abutment material and fabrication technique can affect the magnitude of the implant-abutment microgap.