Evaluation of the first maxillary molar post-extraction socket as a model for dental implant osseointegration research

OBJECTIVES: Published information regarding the use of rat jawbones for dental implant osseointegration research is limited and often inconsistent. This study assessed the suitability and feasibility of placing dental implants into the rat maxilla and to establish parameters to be used for dental implant research using this model. MATERIALS AND METHODS: Forty-two customized titanium implants (2 × 3 mm) were placed bilaterally in the maxillary first molar area of 21 Sprague-Dawley rats. Every animal received two implants. The animals were subsequently sacrificed at days 3, 7, 14, 28 and 56 post-surgery. Resin-embedded sections of the implant and surrounding maxilla were prepared for histological and histomorphometric analyses. RESULTS: The mesial root of the first molar in the rat maxilla was the optimal site to place the implant. Although the most apical 2-3 threads of the implant penetrated into the sinus cavity, 2 mm of the remaining implant was embedded in the bone. New bone formation at day 7 around the implant increased further at day 14, as measured by the percentage of bone-to-implant contact (%BIC) and new bone area (%BA) in the implant thread chambers (55.1 ± 8.9% and 63.7 ± 7.7%, respectively). There was a further significant increase between day 14 and 28 (P < 0.05), however, no significant differences were found between day 28 and 56 in either %BIC or %BA. CONCLUSIONS: The mesial root socket of the first molar in the rat maxilla is a useful model for dental implant research. Osseointegration following implant placement as measured by BIC plateaued after 28 days. The recommended implant dimensions are 1.5 mm in diameter and 2 mm in length.