Miniscrews are increasingly being used to enhance orthodontic anchorage. Objectives: The specific aim of this study was to evaluate the adaptive changes occurring in bone adjacent to a screw interface at 6 weeks post implantation. Methods: Self-drilling (Synthes, USA) screws (102) were placed in 7 dogs at predetermined sites in both jaws. Calcein labels were administered at day 33 and day 40. Animals were sacrificed at day 42. Jaws were dissected and undecalcified sections, each containing the screw and its adjacent bone, were obtained. Thirty-seven sections were examined by histomorphometric methods. Mineral apposition rate (MAR), bone formation rate (BFR) and bone contact (BC) were quantified in the bone supporting the screw. Modeling response in both jaws was also quantified. Results: The BFR in the bone directly adjacent (0-1mm) to the screw was significantly greater (32.7±38.1 vs. 10.2±12.5,%/yr, p=0.01) than in the bone further away (1-4mm) from the screw. The BFR in the mandible was significantly (p=0.001) higher than in the maxilla (35.5± 27.2 vs. 11.6±7.8, %/yr). No significant difference (p>0.05) existed in BC in mandible (94.2±2.9, %) vs. the maxilla (84.7±18.8, %). Periosteal callus thickness of the maxilla was significantly greater (p=0.032) than the mandible. Remodeling and modeling dynamics in bone-screw interface were similar to that observed around endosseous implants. BC for self-drilling screws is typically higher than self-tapping screws placed with a pilot hole. Conclusions: BFR in the mandible was 3-fold greater than in the maxilla. There was a decreasing gradient of BFR from bone adjacent to the screw to bone further away. A vital remodeling interface was seen at 6 weeks post insertion of screws. This suggests an adaptation response, which is necessary for sustenance of the screws during their clinical application existed at 6 weeks post-insertion.

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