Implant-borne suture expansion in rabbits: A histomorphometric study of the supporting bone

Osseointegrated implants have a large potential for diverse clinical applic ations, including support for sutural expansion and facial prostheses. The objectives of this study were to evaluate. (1) the histomorphometric respon se of thin cortical bone to implant placement and (2) whether loading of th e bone surrounding these implants affects osseointegration as evaluated by histomorphometry. Eighteen New Zealand White rabbits had two titanium impla nts placed bilaterally in the anterior surface of their nasal bones. The ra bbits were divided into an unloaded control group, one experimental group l oaded at 1 Newton (N), and another loaded at 3 N. Fluorescent labels were u sed to mark areas of active bone formation. All rabbits were euthanized aft er 12 weeks of loading. Stereological point-hit and line-intercept methods were used to measure bone volume, direct bone-implant contact, new bone vol ume, and bone turnover rate in the bone surrounding the implants. All the i mplants remained stable during the loading period. A factorial ANOVA with r epeated measures was used to compare the variables. The only significant di fference among the three groups was a higher bone volume in the lateral cor onal far region in the control group (p < 0.05). Within all groups, bone vo lume (p < 0.002), turnover rate (p < 0.001), and percent of new bone (p < 0 .05) were higher within 1 mm of the implant compared to 1-3 mm away. This m ay be due to the increased stress and strain in the bone adjacent to the im plant. This study indicates that there are no detrimental effects of loadin g on osseointegration when implants placed in the thin facial cortices are used as anchors for sutural expansion. (C) 1999 John Wiley & Sons, Inc.