Histomorphometric and biomechanical analyses of the osseointegration of loaded orthodontic microscrews inserted at different cortical bone thickness sites.

Objectives: The aim of this study was to evaluate the osseointegration of loaded orthodontic microscrews at different cortical bone thickness (CBT) sites.

Study Design: Forty-eight microscrews were inserted bilaterally in the tibias of 12 beagles, and divided into thick and thin CBT group. After 1, 3, 5, and 7 weeks, the dogs were killed and bone-screw specimens prepared for polyfluorochrome sequential labeling, microscopic computerized tomography (μCT) analysis, and biomechanical pull-out testing.

Results: All μCT parameters were increased in the thin CBT group, and decreased in the thick CBT group with time passed. Fmax of microscrews in thick CBT sites reached a peak in week 1, but dropped to lowest levels in week 3. Remodeling, apposition, and measured deposition areas of 3 labels were significantly higher in the thin CBT group than in the thick CBT group (P < .05).

Conclusions: Relatively larger CBT is of benefit for primary stability at early time points, whereas thinner CBT is more appropriate for achieving long-term stability with prolonged time.