Does orthodontic loading influence bone mineral density around titanium miniplates? An experimental study in dogs.

OBJECTIVES: To evaluate whether orthodontic loading has an effect on miniplate stability and bone mineral density (BMD) around the screws supporting those miniplates. SETTING AND SAMPLE POPULATION: Two miniplates were inserted in each jaw quadrant of 10 dogs. MATERIAL AND METHODS: Two weeks later, coil springs were placed between the miniplates of one upper quadrant and between those of the contralateral lower quadrant. The other miniplates remained non-loaded. The dogs were sacrificed 7 or 29 weeks after surgery, and the jaws were scanned with peripheral Quantitative Computed Tomography (pQCT) to assess BMD. RESULTS: The success rate was not significantly different for the loaded and the non-loaded miniplates, but was significantly higher for the maxillary compared to the mandibular ones. Mobility, associated with local inflammation, most often occurred during the transition between primary and secondary stability. pQCT showed higher BMD around mandibular vs. maxillary screws, without significant difference between loaded and non-loaded ones. Furthermore, load direction did not lead to any significant difference in BMD. CONCLUSION: Miniplate stability and BMD of the adjacent bone did not appear to depend significantly on orthodontic loading, but rather on the receptor site anatomy.