Is a 5 mm rat calvarium defect really critical?

PURPOSE To evaluate bone regeneration in critical defects in the rats' calvarium. METHODS Eighteen rats Wistar were divided into three groups of six animals each according to the time of evaluation (15, 30 and 60 days). One calvarium defect of 5 mm was made in the parietal bone of each animal under general anesthesia. After the time of evaluation, the animals were killed, when the bone was histological studied and classified according to the type of tissue found: fibrosis or bone. RESULTS The results showed that in the group of 15 days, in five animals there was only fibrosis. In the group of 30 days, the process of regeneration was growing and in four animals was found bone, in three with partial filling and in the other one with complete filling of the defect. In the group of 60 days, out of the three animals with bone, two had a complete filling of the defect. CONCLUSIONS There was no bone regeneration in critical defects in 15 days. There was regeneration in the most part of the animals in 30 and 60 days.