Radiotherapy alters the composition, structural and mechanical properties of root dentin in vitro.

OBJECTIVES: Post-radiation dental lesions affect mainly the cervical area of the tooth. Until now, there are quite few evidences regarding the effects of radiation exposure on root dentin breakdown. To better understand this effect, we used human root dentin specimens obtained from third molars from similarly aged individuals. MATERIALS AND METHODS: Twenty specimens were analyzed by the surface hardness (SH), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) to evaluate the baseline properties of their root dentin. Other six human teeth were prepared and analyzed by scanning electron microscopy (SEM). Then the specimens were randomly distributed between two groups (n = 13 per group) and irradiated with a total dose of 55 or 70 Gy in a linear accelerator. The percentage of EDX and surface hardness loss (%SHL) were determined based on measurements before and after irradiation. The specimens were also analyzed after irradiation by SEM and XRD. The Ca/P weight ratio was calculated. RESULTS: Based on SEM analysis, radiation exposure induced dehydration of the dentin. The Ca/P weight ratio decreased (p = 0.0045). The %SHL of specimens irradiated with 70 Gy was higher than that of the 55-Gy group (p < 0.05), although even the lower dose induced root dentin breakdown. CONCLUSIONS: Overall, we can state that radiation exposure changes the composition and structure of human root dentin, which detrimentally affect its hardness. CLINICAL RELEVANCE: The changes reported herein might influence the selection of the dental materials and will bring new knowledge in this field to prevent radiation-related caries in root dentin.

Comparação entre radioterapia convencional e conformacional para tratamento de neoplasia de próstata através de histogramas dose-volume (PAP)

A radioterapia é considerada a modalidade terapêutica padrão para pacientes com neoplasia de próstata podendo ser realizada por diferentes métodos tais como, técnica convencional, conformacional e, mais recentemente, Intensidade Modulada (IMRT). Durante um período de transição entre as técnicas de tratamento empregadas no Serviço de Radioterapia do Hospital das Clínicas de Ribeirão Preto, foi possível avaliar os histogramas dose-volume (DVHs) de pacientes com tumores de próstata que foram tratados com radioterapia convencional e conformacional. O objetivo deste trabalho foi avaliar e comparar quantitativamente a distribuição de dose em reto e bexiga através da análise dos DVHs obtidos para ambas as técnicas utilizadas. Para isso, foram feitos o delineamento do alvo (próstata e vesícula seminal) e dos órgãos de risco de interesse dos vinte e quatro pacientes considerados neste estudo, o planejamento físico com quatro campos (convencional) e cinco campos (conformacional) e, por fim, a análise dos DVHs. Os resultados obtidos revelam que a técnica conformacional possibilita maior entrega de dose no volume alvo e apresenta valores de dose percentuais nos órgãos de risco inferiores aos obtidos com a técnica convencional. Esta comparação entre os dois métodos de tratamento abordados permite análise futura quanto à toxicidade dos pacientes tratados com radioterapia.