Objective: OPG-/- mice develop severe osteoporosis caused by significant enhancement of bone resorption by osteoclasts. We examined the periodontal tissue reaction course of OPG-/- mice using the Waldo method, and we investigated the effect of administering bisphosphonate (BP) on the periodontal tissue.
Materials and Method: Eight-week-old male OPG-/- mice and WT mice were injected with BP intraperitoneally once daily. Under anesthetized conditions, an elastic module was inserted interproximally between the upper first and second molars on the left side. One and 3 days after the elastic insertion, the maxillary bones with surrounding tissues were dissected. Morphology was examined using micro-computed tomography. We measured the shortest intervals between the first and second molars and then performed histological analysis.
Results: At 3 days after elastic insertion, the interdental distance between first and second molars in OPG-/-mice without BP was longer than that in WT mice without BP. No significant differences were found in WT mice without BP compared with OPG-/-mice with BP. Histologically, in WT mice without BP the alveolar bone surfaces facing the tension side of the PDL were very smooth and osteoclasts were seldom observed. On the other hand, in OPG-/- mice without BP, osteoclast number increased notably, and alveolar bone structures were markedly lost. BP treatment of the OPG-/-mice resulted in a decrease in the loss of the alveolar bone.
Conclusion: BP treatment results in normalization of bone metabolism and prevents loss of alveolar bone during experimental tooth movement in OPG-/- mice.