Efeito da radiação ionizante na formação da matriz organica do esmalte dentario / Effect of ionizing radiation in dental enamel organic matrix formation

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The aim of this study was to evaluate the dental eruption rate, the organic enamel matrix birefringence, the odontogenic tissue morphology and the ultrastructure of secretory ameloblasts in incisor of rats submitted to high radiation doses. For this purpose, sixty male rats were used, the first thirty divided into three experimental groups: Control, 15Gy and 25Gy irradiated groups, which received single doses of 15 and 25Gy of X-rays, respectively, localized in the head and neck region. The measurement of the eruption rate was performed every two days, until the total experimental time was reached (six days and half). As an attempt of analyzing the dental development for a longer period, thirty other animals were used, divided into the same three experimental groups and submitted to the same procedure described above. The eruption rate values were submitted to ANOVA and Tukey test (p<0.05). All the animals tested in the sixth day and half were perfused, their hemimaxilla removed, adequately fixed and processed according to the histological protocol of FOP-UNICAMP. For birefringence analysis, the optical retardation was measured in the highest birefringence brightness area, using a polarizing microscope. Data were submitted to statistical analysis (ANOVA) and Tukey test (p<0.05). A descriptive analysis was performed for morphologic and ultrastructural evaluation. It was possible to observe, in irradiated groups, a significant reduction in the eruption rate from the fourth day. A reduction in the birefringence brightness was encountered in the irradiated groups in relation to control; this difference was, however, only significant to 25Gy irradiated group. The odontogenic tissue morphology analysis showed, in control group, odontogenic region with normal features and preserved layer of odontoblasts and ameloblasts. Both irradiated groups presented odontogenic cells disorganization, preameloblasts layer reduced in height and odontoblasts absent or poorly organized. The ultrastructural evaluation showed, in all the examined groups, the presence of organelles and Tomes process preserved. The presence of filaments in contact with the cytoplasmatic organelles was also found. However, in the irradiated groups several degeneration areas and autophagosomes were observed, suggesting a cell death process. Based on these results, it was possible to conclude that high radiation doses were capable to delay the eruption rate from the fourth day; to reduce the birefringence brightness of the organic matrix in the secretory stage of amelogenesis; to alter significantly the odontogenic tissues morphology and to cause aggression, modifying the cellular ultrastructure

ASSUNTO(S)

birrefringencia birefringence ameloblasts ultraestrutura radiation radiação ionizante ameloblastos ionizing ultrastructure

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