Qualitative analysis of peripheral peri-implant bone and influence of alendronate sodium on early bone regeneration.

BACKGROUND Alendronate sodium increases alveolar bone density with systemic use. It inhibits osteoclast activity and is thought to result in a net increase in osteoblastic activity. However, little is known about local in vivo use. The purpose of this study was to evaluate the effect of local delivery of alendronate on bone regeneration within peri-implant defects. Peri-implant bone was examined histomorphometrically to evaluate the amount of supporting bone peripheral to the bone-implant interface. METHODS Six adult hound dogs were evenly divided into 2 groups, with one group receiving alendronate-coated dental implants and the other group serving as controls. Dental implants were placed immediately after extraction of right and left second, third, and fourth mandibular premolars. Forty-eight dental implants were placed (2 types in each dog: 24 hydroxyapatite [HA]-coated and 24 titanium machine-polished [TMP]), for a total of 4 variables. A bioabsorbable collagen membrane was secured over the implants and defects, and the flaps closed primarily. The dogs were sacrificed on day 28. Specimens were sectioned, mounted, and stained with Stevenel's blue and van Gieson's picric fuchsin. The amount of bone adjacent and 1 mm peripheral to the implant surface was recorded with a computerized microscopic digitizer. RESULTS Locally applied alendronate resulted in significantly increased amounts of bone (P<0.0002, ANOVA) in the peripheral area with both HA and TMP implants. However, the most influential factor in the amount of peripheral bone was the type of implant surface (P<0.0001). CONCLUSIONS Local application of alendronate is useful in increasing the amount of peripheral peri-implant bone. Also, the amount of supporting bone was not related to the bone-to-implant contact but to the surface characteristics of the implant. The findings of the present study indicate that the evaluation of dental implant-supporting bone should include peripheral bone as well as bone-to-implant interface.