Research Paper
Osteobiology
Effect of calcitonin on bone regeneration in male rats: a histomorphometric analysis

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Abstract

The aim of this study was to evaluate the effectiveness of calcitonin in promoting bone growth in surgical bone defects in rat mandibles. Fifty male rats were divided into two groups: bone defect (control) and bone defect with calcitonin (experimental). A circular bone defect 4 mm in diameter was made in the mandibular bone of the rats in the angle region, and covered with a polytetrafluoroethylene barrier. The experimental group received 2 IU/kg of synthetic salmon calcitonin intramuscularly three times a week, with treatment starting immediately after surgery. The animals were killed 3, 7, 14, 21 and 28 days after the surgical procedure. The bone defects were examined histologically and by histomorphometric analysis. The Student t-test was applied to the histomorphometric data, with the level of significance set at 5%. The animals of the experimental group showed a lower level of bone formation at almost all time points than the control group, but no difference between groups was observed 28 days after surgery. The volume of newly formed bone matrix was significantly greater in the control than the experimental group at 7, 14 and 21 days, as determined by both morphologic and histomorphometric analysis. Bone repair in the calcitonin-treated animals was delayed in comparison to controls, indicating the need for further studies on male rats.

Section snippets

Animals

Fifty male albino Wistar rats (Rattus norvegicus) aged 3 months and weighing 300 g on average were divided into two groups: control (C) and experimental (Ca). The study was approved by the Local Ethics Committee (07/99-PA/CEP).

Surgery

The animals were anaesthetized with Rompun (pre-anaesthetic, Bayer SA, São Paulo (SP), Brazil) plus Ketalar (anaesthetic, Holliday-Scott SA, SP, Brazil). These drugs were administered intramuscularly to the animals at 1/0.5 proportion, 0.1 mL/100 g body weight. An incision

Radiographic images

A well-delineated and radiolucent round area (Fig. 2) corresponding to the bone defect was observed at all time points studied. Complete closure of the region was not observed in any of the radiographs from the control or experimental groups.

3-day period

The central region of the defect was filled with blood clot, small pieces of debris and some inflammatory cells in both the experimental and control groups. The presence of rounded cells with an osteogenic aspect was observed on the margins of the lesions.

7-day period

A

Discussion

Studies have shown that salmon calcitonin stimulates bone formation in female rats2, 22, 23, 25, 29, 30. In the present study, the animals of the experimental group showed a lower level of bone formation compared to the control group, as determined by both morphologic and histomorphometric analysis. Animals of the control and experimental groups did not show complete closure of the region in the radiographic images at all time points studied.

Calcitonin has been employed for many years as an

Acknowledgments

The authors would like to thank Prof. Ivan Balducci for the statistical analysis; Prof. Nelson Luiz de Macedo for the donation of the PTFE barrier; Kodak, São José dos Campos, SP, Brazil, for the donation of the occlusal film (Kodak Ektaspeed EO-41 P); Novartis Biociências SA, São Paulo, SP, Brazil, for donating the Miacalcin medication, and the Dental School of Piracicaba, UNICAMP, Brazil, for the use of their Radiology Laboratory.

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