Radionuclide imaging of hard and soft tissues of dog jaws under heavy orthodontic forces

Rectilinear scanning with soft tissue, vascular and skeletal imaging agents was used to study the effects of heavy orthodontic forces on the tissues of dog jaws. A coil delivering either a 300 or 600 gram separating force to two adjacent lower right posterior teeth was inserted in each of four dogs. The animals were scanned with the three imaging agents three to four week after insertion of the coils. Only the skeletal agent, Tc-PP, was selectively concentrated in tissues adjacent to the stressed teeth. Tissue distributions of this agent, determined from autopsy samples, revealed that, although all the hard and soft tissues examined contained measurable amounts of Tc-PP, only alveolar bone demonstrated increased uptake of the agent as a result of the applied forces. Tc-PP concentrations were highest in areas of pressure and tension. The total area of alveolar bone showing increased uptake of Tc-PP was larger with 600 than with 300 gram coils. There was close agreement between rectilinear scanning and the tissure distributions of Tc-PP with respect to both the size and anatomic location of the alveolar bone regions affected by the separating forces. This technique may have useful applications in orthodontic research.