Análise da densidade óssea e da atenuação do feixe de raios X nos tecidos moles, em mandíbula de coelhos submetidos à lasertarapia, durante a distração osteogênica

Abstract

INTRODUCTION: Cone-beam computed tomography (CBTC) provides detailed information about the amount and quality of new bone formed during distraction osteogenesis (DO). The density of the lengthened bone is measured based on different levels of gray found in the images. The use of CBTC therefore allows to perform a quantitative analysis of bone density and, thus, to measure the level of X-ray attenuation by soft tissues. OBJECTIVES: To assess, via CBTC, newly formed bone in mandibles of rabbits treated with DO under the biomodulating effects of AsGaAl infrared laser radiation (λ=830 nm, 40 mW), applied during the activation phase. The distracted area was assessed based on the gray levels shown on images and observing the influence of soft tissues on X-ray attenuation. MATERIALS AND METHODS: Ten rabbits were used (two experimental groups and one control group). The two experimental groups were treated with DO and low-level laser therapy. Rabbits in experimental group A were killed 11 days after the beginning of DO, and those in experimental group B, after 21 days of DO. CBTC images were obtained from the mandibles of the ten rabbits with soft tissues and subsequently (after dissection) without soft tissues. This comparison allowed to analyze the influence of soft tissues on X-ray attenuation, and consequently on the decrease in gray levels observed in the tomographs of rabbits treated with DO. RESULTS: The presence of soft tissues increased X-ray attenuation, resulting in a decrease in the levels of gray observed in three-dimensional CBCT images of mandibular bone tissue of the rabbits before and after soft tissue removal. The area of the mandibles treated with DO presented higher levels of gray in rabbits killed at 21 days. CONCLUSIONS: CBCT allowed to assess bone density variation in areas treated with DO. The presence of soft tissues contributes to decrease the levels of gray in three-dimensional CBCT bone tissue images of the ten rabbits assessed. This occurs due to the absorption of X-rays by soft tissues studied by tomography. We found that bone density in the area treated with DO, as observed on tomography, increased in direct proportion to the bone maturation period after the activation phase in DO, based on the gray levels observed.