Estudo in vivo e in vitro com e sem termociclagem, da resistência ao cisalhamento de braquetes colados com fonte de luz halógena
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2008-06-01
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Dental Press Editora
Resumo
OBJETIVO: avaliar a resistência de braquetes metálicos colados em dentes humanos com resina polimerizada com luz halógena por meio de ensaios mecânicos de cisalhamento. METODOLOGIA: para este estudo foram realizados ensaios in vivo com dinamômetro portátil digital e in vitro com máquina de ensaios mecânicos universal com e sem termociclagem, complementado pelo Índice de Adesivo Remanescente (IAR). Braquetes Edgewise Standard (Abzil) foram colados utilizando adesivo Transbond Plus Self Etching Primer (SEP) e Resina Transbond XT. Foram formados 3 grupos com 10 dentes em cada um deles. No GI os braquetes foram colados nos segundos pré-molares dos pacientes. Nos GII e GIII utilizaram-se primeiros pré-molares extraídos por motivos ortodônticos. Os ensaios mecânicos do GI foram realizados 24 horas após a polimerização diretamente na boca dos pacientes com dinamômetro portátil digital. No GII os corpos-de-prova foram armazenados em água destilada e levados à estufa a 37ºC durante 24 horas e, posteriormente, submetidos à termociclagem, com 1000 ciclos a 5 e 55ºC. No GIII os corpos-de-prova foram armazenados em água destilada em temperatura ambiente por 24 horas e posteriormente submetidos aos ensaios mecânicos. RESULTADOS: os valores médios da resistência ao cisalhamento em Megapascal foram de: GI = 4,39; GII = 7,11 e GIII = 7,35. Após a descolagem foram realizadas fotografias das áreas de colagem, tanto dos dentes submetidos a testes in vivo quanto in vitro e ampliadas 5x para facilitar a visualização. As imagens obtidas foram analisadas, classificadas de acordo com o IAR e, por meio de gráficos de dispersão, foi verificada a relação entre a resistência ao cisalhamento e este índice. CONCLUSÃO: a média dos ensaios mecânicos realizados in vivo foi estatisticamente menor em relação aos ensaios in vitro. Não houve diferenças na resistência ao cisalhamento in vitro entre o grupo termociclado e o não-termociclado. Não houve relação entre tensão de ruptura e tipo de falha.
OBJECTIVE: The purpose of this research was to assess the strength of metallic brackets bonded to human teeth, with lightcuring resin with halogen light, by means of mechanical tests of shear bond strength. METHODS: In vivo tests with a portable digital dynamometer and in vitro tests with Universal testing machine were performed, with and without thermocycling, complemented by Adhesive Remaining Index (ARI). Edgewise standard brackets (Abzil) were bonded using Transbond Plus Self Etching Primer (SEP) and Transbond XT resin. Three groups of ten teeth each have been formed. In GI the brackets were bonded to second premolars in the patients mouths. In GII and GIII the brackets were bonded to first premolars extracted for orthodontic reasons. The mechanical tests of GI were performed 24 hours after the polymerization, directly in the patients mouths with a portable digital dynamometer. In GII the specimens were stored in distilled water and taken to sterilizer at 37ºC for 24 hours and afterwards, submitted to thermocycling with 1000 cycles at 5 and 55º C. In GIII the specimens were stored in distilled water at room temperature for 24 hours, and then submitted to mechanical tests. RESULTS: The average values of the shear strength in Megapascal were: GI=4.39; GII=7.11 and GIII=7.35. Pictures of the bonding areas in both in vivo and in vitro samples were taken after the tests and they were amplified 5 times to be better visualized. The images obtained were analyzed, classified according to IAR and it was verified, by means of dispersion graphs, the relation between the shear bond strength and this index. CONCLUSION: The average of the in vivo mechanical tests was statistically lower than the in vitro tests. There were no differences in the in vitro shear bond strength between the thermocycled and non-thermocycled groups. There was no relation between shearing stress and kind of failure.
OBJECTIVE: The purpose of this research was to assess the strength of metallic brackets bonded to human teeth, with lightcuring resin with halogen light, by means of mechanical tests of shear bond strength. METHODS: In vivo tests with a portable digital dynamometer and in vitro tests with Universal testing machine were performed, with and without thermocycling, complemented by Adhesive Remaining Index (ARI). Edgewise standard brackets (Abzil) were bonded using Transbond Plus Self Etching Primer (SEP) and Transbond XT resin. Three groups of ten teeth each have been formed. In GI the brackets were bonded to second premolars in the patients mouths. In GII and GIII the brackets were bonded to first premolars extracted for orthodontic reasons. The mechanical tests of GI were performed 24 hours after the polymerization, directly in the patients mouths with a portable digital dynamometer. In GII the specimens were stored in distilled water and taken to sterilizer at 37ºC for 24 hours and afterwards, submitted to thermocycling with 1000 cycles at 5 and 55º C. In GIII the specimens were stored in distilled water at room temperature for 24 hours, and then submitted to mechanical tests. RESULTS: The average values of the shear strength in Megapascal were: GI=4.39; GII=7.11 and GIII=7.35. Pictures of the bonding areas in both in vivo and in vitro samples were taken after the tests and they were amplified 5 times to be better visualized. The images obtained were analyzed, classified according to IAR and it was verified, by means of dispersion graphs, the relation between the shear bond strength and this index. CONCLUSION: The average of the in vivo mechanical tests was statistically lower than the in vitro tests. There were no differences in the in vitro shear bond strength between the thermocycled and non-thermocycled groups. There was no relation between shearing stress and kind of failure.
Descrição
Palavras-chave
Resistência ao cisalhamento, Luz halógena, Máquina universal de ensaios mecânicos, Termociclagem, Tensiômetro portátil digital, Shear bond strength, Light, Universal testing machine, Thermocycling, Portable digital debonding device
Como citar
Revista Dental Press de Ortodontia e Ortopedia Facial. Dental Press Editora, v. 13, n. 3, p. 66-76, 2008.