The purpose of the present study was to examine the effect of the bisphosphonate on osteoblastic activity of the human periodontal ligament cells in vitro. Periodontal ligament cells were primarily obtained from extracted healthy third molars. Cells of 4th to 6th passage were cultured in Dulbecco's modified Eagle's medium containing alendronate sodium or etidronate disodium at the concentration of 10^-12~10^-6 mol/L in 5% CO₂ incubator at 37℃. Cell count and MTT assay for cellular activity were done at 2 to 7 days of culture. Alkaline phosphatase activity at 4 to 7 days of culture and formation of mineralized nodules at 28 days of culture with addition of 50 µg/ml ascorbic acid, 10 mM β-glycerophosphate , 10^-7 M dexamethasone were evaluated.

1. Alendronate sodium

Compared to the control, the proliferation of periodontal ligament cells was generally increased and the cellular activity was maintained at 2 days of culture and generally decreased at 7 days of culture. Alkaline phosphatase activity of periodontal ligament cells was increased and the formation of mineralized nodules by periodontal ligament cells was enhanced compared to the control.

2. Etidronate disodium

The proliferation of periodontal ligament cells was increased at 2 days of culture and decreased or maintained at 7 days of culture. Compared to the control, the cellular activity of periodontal ligament cells was generally decreased. Alkaline phosphatase activity of periodontal ligament cells was increased and the formation of mineralized nodules by periodontal ligament cells was enhanced compared to the control.

These results suggest that alendronate sodium and etidronate disodium may have a potential effect on osteoblastic lineage of periodontal ligament cells, distinct from their inhibitory action on osteoclasts and could contribute to enhance periodontal regeneration and alveolar bone regeneration.