Periapical changes after orthodontic movement of root-filled ferret canines.

The effectiveness of orthodontic forces in moving root-filled teeth and the degree of apical resorption it causes have been observed in an animal model. Under general anesthesia, root canal therapy was performed on the mandibular canines on one side of 12 young male ferrets. Bilateral movement of the canines was induced with an orthodontic spring (150 to 175 g). Procion red dye was injected 1 wk presurgically to mark bone and cementum deposition. Three months later, tooth movement was assessed from pre- and posttreatment mandibular casts and by fluorescence microscopy from labeled bone deposition. Vital and nonvital teeth moved similar distances when subjected to the same forces. Root-filled teeth showed greater loss of cementum after tooth movement than vital teeth (p < 0.05), but without significant differences in radiographic root length.