[Research on feasibility and effectiveness of the bone-implant contact evaluation in dogs by micro-CT]

Objective: To discuss the feasibility and effectiveness of using micro-CT in bone-implant contact (BIC) evaluation in dogs, and to provide reference for clinical and scientific research. Methods: Bilateral mandibular second premolar and first molar of six male Beagle dogs were extracted. After 3 months' healing, eight implants were placed in bilateral mandible of each dog, four on each side. Dogs were sacrificed at 2 weeks, 4 weeks and 8 weeks after implant placement, two on each time point. Samples were scanned with micro-CT and digitally reconstructed. Bone-implant interface was analyzed at different analysis regions (25, 50 and 100 μm from implants' surface), different detection range models were obtained (each time point consists 48 models), and BIC was evaluated, and the results were counted as micro-CT(25), micro-CT(50), and micro-CT(100) groups. Then undecalcified slides were made (three slides for each sample) and stained with toluidine blue for observation and analysis of BIC using an optical microscope, and the results were counted as optical microscope groups. The advantages and disadvantages, evaluation efficiency and BIC of different methods were analyzed. Results: To evaluate BIC of single sample, it took about 90 minutes by micro-CT, which was much lower than the time of 14 days by optical microscope. The success rates of modeling of micro-CT(25), micro-CT(50), and micro-CT(100) groups all were 100.0% (48/48), and total success rate of micro-CT group was 100.0% (144/144). For optical microscope groups, the success rates of making slides 2, 4, 8 weeks were 89.6% (43/48), 93.8% (45/48) and 93.8% (45/48), respectively, and total success rates of optical microscope group was 92.4% (133/144). At 2, 4,8 weeks after implantation, BIC in micro-CT(25) group was significantly smaller than that in optical microscope group at the same time point (P<0.05). However, at 2, 4,8 weeks after implantation, BIC of the micro-CT(50) and micro-CT(100) groups showed no significant difference with optical microscope groups at the same time point (P>0.05). A significant correlation (P<0.001, each) was seen between slides and micro-CT (25, 50, 100 μm groups) concerning BIC (r=0.680, r=0.892, r=0.713), and error bias was -19.4%, -0.9%, 3.0%, respectively. The probability within the 95% limits of agreement were 97.9%. Conclusions: Micro-CT is a faster, simpler and more efficient way to analyze BIC at the implant-bone interface than optical microscope observation. BIC analysis by selecting 50 μm from implants' surface as analysis region using micro-CT is in consistent with that using the optical microscope.