Internal fit of cobalt–chromium and zirconia implant abutments fabricated using different techniques: a micro–computed tomography study

Purpose To evaluate the internal fit at the implant-abutment interface of zirconia and cobalt–chromium abutments fabricated using different techniques by micro-computed tomography (micro-CT). Methods Twenty screw-retained abutments were divided into 4 groups ( n = 5): milled zirconia (ZrCAD), milled cobalt–chromium (Co-CrMill), laser-sintered cobalt–chromium (Co-CrLS), and cast cobalt–chromium (Co-CrCL). Specimens were subjected to cyclic loading (300,000 cycles, 200 N) and thermocycling (10000 cycles, 5 to 50 °C). Internal fit was assessed by micro-CT at 3 regions and 3 spatial planes (180 measurements). Data were analyzed with Kruskal–Wallis and Bonferroni-Holm tests (α = 0.05). Results Significant differences in internal fit were found ( p < 0.05). Co-CrLS showed the highest internal gap values (26.75 ± 7.05 μm, 87.00 ± 3.26 μm, 86.50 ± 5.76 μm). Significant differences were observed between Co-CrLS and ZrCAD (Region 1, p = 0.003), Co-CrMill (Regions 1 and 2, p = 0.003–0.004), and Co-CrCL (Regions 1 and 3, p = 0.003–0.001). Total values also differed between Co-CrMill and Co-CrLS ( p = 0.012) and Co-CrCL and Co-CrLS ( p = 0.002). Conclusions Internal fit differed among the evaluated workflows. Laser-sintered cobalt–chromium abutments showed the least favorable adaptation, whereas milled and cast cobalt–chromium showed lower gap values; zirconia showed intermediate descriptive values. The clinical significance of these differences remains uncertain. Clinical trial number Not applicable.