The critical-size supraalveolar peri-implant defect model:: characteristics and use

Objective: Novel implant technologies and reconstructive therapies for alveolar augmentation require pre-clinical evaluation to estimate their biologic potential, efficacy, and safety before clinical application. The objective of this report is to present characteristics and use of the critical-size, supraalveolar, peri-implant defect model. Methods: Bilateral extraction of the mandibular premolars was performed in 12 Hound Labrador mongrel dogs following horizontal surgical cut-down of the alveolar ridge approximating 6 mm. Each jaw quadrant received three custom-produced TiUnite(TM), empty set4.0 x 10 mm threaded implants placed into osteotomies prepared into the extraction sites of the third and fourth premolars. The implants exhibited a reference notch 5 mm from the implant platform to facilitate surgical placement leaving 5 mm of the implant in a supraalveolar position, and to serve as a reference point in the radiographic, histologic and histometric analysis. The implants were submerged under the mucoperiosteal flaps for primary intention healing. Fluorescent bone markers were administered at weeks 3 and 4 post-surgery, and pre-euthanasia. The animals were euthanized following an 8-week healing interval when block biopsies were collected for analysis. Results: Healing was generally uneventful. The radiographic and histometric evaluations demonstrate the limited osteogenic potential of this defect model. Whereas lingual peri-implant sites exhibited a mean (+/- SE) bone gain of 0.4 +/- 0.1 mm, resorption of the buccal crestal plate resulted in a mean bone loss of 0.4 +/- 0.2 mm for an overall osteogenic potential following sham-surgery averaging 0.0 +/- 0.1 mm. Overall bone density and bone-implant contact in the contiguous resident bone averaged 79.1 +/- 1.1% and 76.9 +/- 2.3%, respectively. Conclusion: The results suggest that the critical-size, supraalveolar, peri-implant defect model appears a rigorous tool in the evaluation of candidate technologies for alveolar reconstruction and osseointegration of endosseous oral implants. Limited innate osteogenic potential allows critical evaluation of osteogenic, osteoconductive, or osteoinductive technologies in a challenging clinical setting.