Animal model for evaluating the effect of systemic estrogen deficiency on residual ridge resorption

The rate of resorption of residual ridges after tooth extraction varies among subjects. Despite many human studies, the etiologic factors of severe forms of resorption of residual ridges are unknown and probably multifactorial. To facilitate investigations of resorption of residual ridges, it is preferable to use an animal model with a dentoalveolar component similar to that of human beings. This study developed a rapid, nonhuman primate model in which one could measure resorption of residual ridges at the most critical period, with the least amount of time, minimal operation, and the least interference with normal nutrition. Three female Macaca fascicularis monkeys, 7 to 9 years old, were selected for simple extraction of four maxillary incisors, four mandibular incisors, and two mandibular canines. Lateral cephalographs were taken at weeks 0, 1, 2 to 3, 5 to 6, 8 to 9, 11 to 12, and 26 to 28 after extraction with a newly constructed cephalostat that allowed easy reproducibility of animal placement in the prone position. Height and area measurements were made of maxillary and mandibular anterior residual ridges in the superimposed cephalographs. Sequential mean bone loss data produced bone loss curves similar to those observed in humans. One animal underwent ovariectomy. The plasma levels of both estrogen and progesterone decreased over 25 days and stayed below the detection limits thereafter. Tooth extraction was done 4 weeks after the ovariectomy and the bone resorption pattern was able to be observed longitudinally with the newly established monkey cephalostat. The results indicated that Macaca fascicularis need not be sacrificed when used in longitudinal studies of resorption of residual ridges in a relatively short period of experimental time. This model can provide an excellent opportunity to investigate a causal relationship between the rate of resorption of residual ridges and predisposing systemic factors such as estrogen deficiency.