Effect of altered occlusal function on transseptal ligament and new bone thicknesses in the periodontium of the rat.

Alteration of tooth function is assumed to change stress/strain on the adjacent alveolar bone and its mucoperiosteum, producing changes in morphology similar to those described for other load-bearing bones. The present study suggested that crestal alveolar bone and its mucoperiosteum respond differently to stress/strain than load-bearing bones in other locations, possibly due to differences in the mechanism of bone loading by muscles and teeth. Occlusal hypofunction was initiated by extraction of agonist teeth; the contralateral teeth were placed in hyperfunction by the surgery. Untreated animals were also studied. 3H-proline was injected, animals were killed 1-5 weeks later, and the thicknesses of new bone and transseptal ligament were measured. After 5 weeks of altered function, total thickness (new bone + transseptal ligament) was similar in untreated and in hypofunctional and hyperfunctional situations; however, a new ratio between transseptal ligament and new bone thicknesses was established. Occlusal force was negatively correlated with new bone and positively correlated with transseptal ligament thickness; both thicknesses were statistically correlated in each functional situation (P less than 0.001). Hyperfunction resulted in increased transseptal ligament thickness, but decreased new bone thickness as compared to untreated controls (P less than 0.001). In contrast, hypofunction resulted in an increased new bone thickness, but a decreased transseptal ligament thickness (P less than 0.001). Tissue responses assure appropriate support for the teeth in each functional situation.