Histologic, histomorphometric, and radiographic monitoring of bone healing around in-office-sterilized orthodontic mini-implants with or without immediate load: study in rabbit tibiae.

PURPOSE: The objective of this study was to describe bone healing around self-drilling orthodontic mini-implants (MIs), sterilized in an office with an autoclave, with or without immediate orthodontic loading. MATERIALS AND METHODS: One hundred forty-four self-drilling MIs (TOMAS, Dentaurum) were inserted into the tibiae of 18 white rabbits, with full-thickness flaps elevated under general anesthesia. An immediate load (50 cN) was applied to 50% of the MIs. Two rabbits were sacrificed soon after the surgery and served as a control group. Four rabbits each were sacrificed at 15, 21, 30, or 60 days after the surgeries. Digital radiographs were obtained to measure the cortical bone thickness (CBT) around and between the implants. Sections were obtained and stained for histologic and histomorphometric analysis. Bone quantity (BQ), bone-to-implant contact (BIC), and CBT were evaluated statistically. RESULTS: At day 0, fractures were visible in the cortical area around the MIs. At days 15 and 21, intense proliferation of woven bone followed by formation of lamellar bone was seen. After 30 days, primary bone was visible, with less proliferation activity. At day 60, primary bone in the process of remodeling into secondary bone was apparent. BQ was better with loading after 15 days and increased throughout the healing period in the loaded and unloaded groups. Loading did not influence the BIC values, which increased with healing time for loaded and unloaded implants. CBT increased in all regions, and CBT was greater around the MIs than between them except for unloaded MIs in the 15-day group. CONCLUSION: An immediate, light orthodontic load did not affect the bone healing process around orthodontic MIs. Osseointegration and CBT increased and were time-related.