Orthodontic brackets undergo resistance during sliding that includes classical friction, binding, and notching. Current bracket systems are hampered by these challenging forces. As a result, the clinician usually needs to apply additional forces to overcome the resistance which increases the risk of root resorption and discomfort for the patient. This study evaluated frictional properties of a novel bracket that had polytetrafluoroethylene (Teflon™) coated rollers in its design. Five types of brackets (n = 10, each), including a passive self-ligating bracket, a traditional ligated bracket, a three-dimensionally printed direct metal laser sintering (DMLS) bracket with and without Teflon™ rollers, and computer numeric controlled (CNC) machine milled bracket with Teflon™ rollers were tested. The peak resistance values were assessed at 0°, 4°, and 8° of tip on a 0.019 x 0.025” arch wire. At 8° of tip, the DMLS and the CNC milled bracket systems, both with Teflon™ rollers, exhibited less friction as compared to the other brackets tested (p

Made available in DSpace on 2016-08-03T16:31:14Z (GMT). No. of bitstreams: 1 Paginas 1 a 110.pdf: 2675655 bytes, checksum: ebe1b48d56fd661d5dc8a8a84083c9f1 (MD5) Previous issue date: 2009-03-25 / The aim of this in vitro study was to compare the friction resistances among conventional steel-ligated and self-ligating aesthetic brackets with different retangular stainless steel archwires sizes at zero and three degrees angulation. 120 brackets of 6 commercial brands (Gemini, Clarity conventional, Transcend, Inspire, Clarity self-ligating, Damon self-ligating) where tested, 20 brackets of each brand. Two brackets were glued on a metallic plate, with angulations of zero and three degrees between them. Retangular stainless steel archwires of 0.017 x 0.025 , 0.019 x 0.025 and 0.021 x 0.025 were tested on a "instron" universal essay machine. Variance analisys and Tukey tests (p<0,05) were run to compare brackets with different archwires sizes and angulation. The study demonstrated that at zero degree angulation the self-ligating brackets produced less friction in relation to convencional ligated bracket in all archwires sizes tested. Clarity self-ligating produces even less friction then aesthetic Damon, except with the 0.021 x 0.025 archwire, where both self-ligating brackets produced statisticly similar results. Inspire bracket had the least friction with 0.019 x0.025 and 0.021 x0.025 . Similar results were observed for the self-ligating brackets in relation to convencionals at three degrees angulation. Among the convencional steel-ligated brackets, Gemini, Clarity, Transcend and Inspire produced the higest friction resistances, in increasing order. In conclusion, the angulation between the brackets increases significatively the friction forces. Furthermore, the self-ligating brackets produces less friction in relation to conventional ligating brackets, and the Clarity self-ligating bracket produced less friction than aesthetic Damon, except with 0.021 x 0.025 archwire size.(AU) / O objetivo do presente estudo consistiu em comparar in vitro o atrito produzido por braquetes estéticos, convencionais e autoligados quando inseridos fios retangulares de aço inoxidável de diferentes dimensões, nas angulações de zero e três graus entre os braquetes. Foram utilizados 120 braquetes de 6 marcas comerciais (Gemini, Clarity convencional, Transcend, Inspire, Clarity autoligado, Damon autoligado), sendo 20 braquetes de cada marca comercial. Para os ensaios laboratoriais, foram colados dois pares de braquetes de cada marca comercial em uma placa metálica, com uma angulação de zero e três graus entre os braquetes. Foram empregados os fios retangulares de aço inoxidável 0,017 x 0,025 , 0,019 x 0,025 e 0,021 x0,025 em uma máquina de ensaios universal Instron . Para a comparação entre os braquetes nos diferentes fios e angulações, foi utilizada a análise de variância e o teste de Tukey (p<0,05). Os resultados demonstraram que na angulação de zero grau, os braquetes autoligados apresentaram menor atrito em relação aos convencionais em todos os fios avaliados, sendo que, o braquete Clarity autoligado apresentou menor atrito estatisticamente significante que o Damon, exceto no fio 0,021 x 0,025 , em que ambos os braquetes autoligados apresentaram atrito estatisticamente semelhante. O braquete Inspire demonstrou o maior atrito em relação aos demais braquetes nos fios 0,019 x0,025 e 0,021 x0,025 . Na angulação de três graus, observou-se resultados semelhantes aos braquetes posicionados sem angulação comparando os braquetes autoligados em relação aos convencionais. Contudo, verificou-se que o atrito entre os braquetes convencionais ocorreu em ordem crescente sendo braquetes Gemini, Clarity convencional, Transcend e Inspire. Pôde-se concluir que a angulação entre os braquetes aumenta consideravelmente o atrito. Além disso, em ambas as angulações, os braquetes autoligados demonstraram menor atrito em relação aos convencionais, sendo que o braquete Clarity autoligado promoveu menor atrito que o Damon estético, exceto no fio 0,021 x 0,025 .(AU)