Determination of critical size defect of minipig mandible.

The critical size defect (CSD) of bone can provide a standard for evaluating the usefulness of bone repair materials or methods. The present study aimed to determine the CSDs of the minipig mandible with and without the periosteum. Ten 18 month-old female minipigs were used. First, the premolars and the first molar in the right mandible of each minipig were extracted. Two months later, the animals were randomly divided into two groups, with six animals in group A and four in group B. In group A, bone segments of 4, 5 and 6 cm were removed from the right mandible and the neighbouring periosteum was preserved. In group B, bone segments of 1 and 2 cm were removed from the right mandible and the periosteum was removed. The defects were retained with two reconstructive titanium plates. The mandibles underwent X-ray examinations at 4, 8 and 12 weeks after the operation. The animals were sacrificed at 12 weeks after the operation, and specimens were evaluated by gross and histological examinations. For defects retained by two reconstructive plates, the CSDs in the minipig mandible models with and without periosteum were determined as 6 and 2 cm, respectively.