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.