Evaluation of a Canine Immediate-Loading Implant Defect Model

Objectives: Numerous biotechnologies are being developed for peri-implant alveolar augmentation. The objective of this study was to evaluate a canine implant dehiscence defect as a model to study bone formation and osseointegration under conditions for functional loading. Ultimately such a preclinical model would become useful to study osteoconductive and/or osteoinductive biotechnologies prior to clinical introduction.

Methods: Buccal, 4x5 mm, dehiscence defects were surgically prepared in conjunction with placing implants (3 implants/jaw quadrant) into mandibular premolar extraction sockets in six adult male Hound Labrador mongrel dogs. Prosthetic abutments subject to functional loading were placed and wound closure for primary intention healing achieved. Resonance frequency analysis was performed at intervals throughout the study, as was administration of bone fluorescent markers. The animals were euthanized at 8 weeks postsurgery for histometric analysis. Examiner reliability was assessed using the concordance correlation coefficient. Generalized estimating equations were used for analysis; measurements at implant level were used and estimates adjusted for clustering of implants into animals using a robust variance estimator. Wald tests were used for multiple comparisons. Level of significance was set at 5%.

Results: Healing was uneventful without any defect exposures. Examiner reliability was generally high ranging from 0.92 to 0.99. RFA showed significantly improved implant stability (ISQs) from 55.7±2.9 at baseline to 72.4±1.2 at 8 weeks. Mean defect height was 5.3±0.2 mm. Fluorescent/incandescent light microscopy showed limited new bone formation averaging 0.6±0.4 mm. Bone-implant contact averaged 30.6±15.4% vs. 79.3±2.7% in the adjoining resident bone.

Conclusion: The observations herein suggest that the canine implant dehiscence defect appears a valid critical-size model for study of osteoconductive and/or osteoinductive biotechnologies intended for alveolar augmentation under conditions for functional loading.