Biomechanical and histological comparison of self-drilling and self-tapping orthodontic microimplants in dogs

Introduction: The purpose of this study was to compare the influences of different implant modalities on orthodontic microimplants and surrounding tissues biomechanically and histologically. Methods: Fifty-six titanium alloy microimplants placed on the buccal side of the maxillae and the mandibles in 2 dogs were divided into 2 groups of 28; one group of microimplants was self-drilling, and the other was self-tapping. Approximately 200 g of continuous and constant forces were applied immediately between 2 microimplants by stretching closed nickel-titanium coil springs for 9 weeks. Peak insertion torque and removal torque were recorded immediately after the implants were placed and when the dogs were killed, respectively. Undecalcified sections of the microimplants and the surrounding tissues were studied with light microscope and fluorescent microscope. Results: Success rates were higher in the self-drilling group (93%) than in self-tapping group (86%). Higher peak insertion torque and peak removal torque values were seen in the self-drilling group in both the maxilla and the mandible. A tendency to fracture was found in self-drilling group. The percentage of bone-to-implant contact values was greater in the self-drilling group. Conclusions: Self-drilling microimplants can provide better anchorage and can be recommended for use in the maxilla and in thin cortical bone areas of the mandible.