Study of the mandibular bone dynamics and of the alveolar crest resorption processes in diabetic and control rats.

Periodontal illness is an inflammatory reaction of the periodontal tissue to the bacteria in the dental plaque. In order to assess the mandibular growth and describe the development of rats’ “spontaneous” periodontal illness, control animals line “m” were employed. The findings observed were corroborated against two experimental models (experimental diabetes and bisphosphonates). The experimental diabetes model was explored, because diabetes is considered an aggravating factor of periodontal illness. A therapeutic assay was carried out with bisphosphonates, which are highly recognized drugs for their antiosteoclastic effect. Periodontal illness can be considered an illness of the bone metabolism, given the typical bone resorption. In control rats, mandible growth matched body growth. Diabetes had an adverse effect on body growth which did not show in dry weight, density or mandible volume. In comparison with the control animals, animals treated with lidadronate (IG-9402) revealed a significant increase in dry weight and mandible volume. These results are consistent with such drugs’ well-known antiresorptive effect. The distance between the amelo-cementum junction and the alveolar bone crest (LAC-COA) increased as time elapsed, and it was bigger on the lingual side than on the vestibular side, in control animals, in diabetic animals and in animals treated with bisphosphonates. Measurement of the supporting periodontal bone (HPS) has not proved to be a useful means to assess periodontal illness during the rat’s fast-growing period. Periodontal illness appeared after weaning, and developed towards the 6th or 7th week after birth, with no signs of pathological alteration of the gingival tissue. In diabetic animals, there was a bigger number of focuses with lower total area in the resorption involved. Lower bone turnover, as well as the likely immunological tolerance to the usual food and mouth germs, account for this observation. The mineral density of the periodontal bone with no pathology was, on average, 34% lower in comparison with the control animals. The mineral density of the periodontal bone in resorption was also significantly lower. Equal doses of two bisphosphonates did not produce equal results. Lidadronate reduced the total area in resorption. Olpadronate significantly increased the mineral density of the periodontal bone with no pathology. With the techniques employed, modifications consistent with the bisphosphonates’ antiosteoclastic effect were observed. The accumulated evidence proved contradictory: on the one hand, a series of indicators (number and amplitude of resorption focuses, and bone loss evidenced by the increase of the LAC-COA distance and the histological images of bone resorption) would suggest that the “spontaneous” periodontal illness advances with age. However, the lymphocyte clusters in the periodontal tissue were observed only in the 4th week. These results suggest two hypotheses: 1. The “spontaneous” periodontal illness is an example of immune tolerance. 2. The modifications observed in very young rats’ periodontium are produced by the environmental antigens in an immaturity period of the immune system.

Received: Jul. 2008 Accepted: Sep. 2008