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Previous issue date: 2012-03-08 / 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. / INTRODU??O: A tomografia computadorizada do tipo Cone-beam (TCCB) fornece informa??es detalhadas sobre a qualidade e a quantidade de osso neoformado pela distra??o osteog?nica (DO). Permite mensurar a densidade do osso alongado, por meio da avalia??o dos tons de cinza. Desta forma, pode-se realizar uma an?lise quantitativa da densidade ?ssea, dimensionando a atenua??o dos feixes de raios X pelos tecidos moles nas imagens. OBJETIVOS: Avaliar, por interm?dio da TCCB, o osso mandibular neoformado em mand?bulas de coelhos submetidos ? DO, sob efeito biomodulat?rio da irradia??o por laser infravermelho AsGaAl (λ=830 nm, 40 mW), aplicado durante a fase de ativa??o do aparelho distrator. A ?rea da distra??o ? avaliada pelos n?veis de cinza das imagens, observando tamb?m a influ?ncia dos tecidos moles na atenua??o dos feixes de raios X. MATERIAIS E M?TODOS: Dez coelhos foram utilizados (dois grupos experimentais e um grupo controle). Os grupos experimentais foram submetidos ? DO e ? terapia a laser de baixa potencia (LLLT). Os coelhos do grupo experimental A foram mortos ap?s 11 dias do in?cio da DO e os coelhos do grupo experimental B, mortos ap?s 21 dias do in?cio da DO. Os 10 coelhos foram submetidos a tomografia com tecidos moles e posteriormente dissecados e submetidos a tomografia sem tecidos moles. Assim, foi poss?vel analisar a influ?ncia dos tecidos moles em coelhos submetidos ? DO na atenua??o dos feixes de raios X e, consequentemente, na diminui??o dos valores de n?veis de cinza observados na imagem tomogr?fica. RESULTADOS: A presen?a dos tecidos moles aumenta a atenua??o dos feixes de raios X contribuindo na diminui??o dos valores de n?veis de cinza, observados na imagem do tecido ?sseo em 3D, na mand?bula dos 10 coelhos submetidos a tomografia, antes e ap?s a remo??o dos tecidos moles. A ?rea das mand?bulas submetidas ? distra??o apresentaram valores superiores de cinza, nos coelhos mortos ap?s 21 dias do in?cio da DO. CONCLUS?ES: Com tom?grafos do tipo Cone-beam, foi poss?vel avaliar a varia??o da densidade ?ssea em ?reas submetidas ? DO. A presen?a dos tecidos moles contribui na diminui??o dos valores de n?veis de cinza observados nas imagens do tecido ?sseo dos 10 coelhos em 3D. Isto ocorre devido ? absor??o do feixe de raios X pelos tecidos moles submetidos a tomografia. Tamb?m observou-se que a densidade ?ssea na ?rea da distra??o, visualizada na tomografia, aumenta proporcionalmente ao per?odo de matura??o ?ssea ocorrido ap?s a fase de ativa??o da DO, conforme observa??o dos valores de cinza obtidos.
| Identifer | oai:union.ndltd.org:IBICT/oai:tede2.pucrs.br:tede/1162 |
| Date | 08 March 2012 |
| Creators | Cenci, Rodrigo Alberto |
| Contributors | Oliveira, Mar?lia Gerhardt de |
| Publisher | Pontif?cia Universidade Cat?lica do Rio Grande do Sul, Programa de P?s-Gradua??o em Odontologia, PUCRS, BR, Faculdade de Odontologia |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | application/pdf |
| Source | reponame:Biblioteca Digital de Teses e Dissertações da PUC_RS, instname:Pontifícia Universidade Católica do Rio Grande do Sul, instacron:PUC_RS |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | -8096554818733665164, 500, 600, 4673435736271820140 |
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