부산대학교 도서관

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1600-0501.2008.01690.x Byline: Abilio Ricciardi Coppede (1), Maria da Gloria Chiarello de Mattos (1), Renata Cristina Silveira Rodrigues (1), Ricardo Faria Ribeiro (1) Keywords: dental implants; internal tapered connection; loosening torque; prosthesis and implants; tightening torque Abstract: Abstract Objectives: Internal tapered connections were developed to improve biomechanical properties and to reduce mechanical problems found in other implant connection systems. The purpose of this study was to evaluate the effects of mechanical loading and repeated insertion/removal cycles on the torque loss of abutments with internal tapered connections. Material and methods: Sixty-eight conical implants and 68 abutments of two types were used. They were divided into four groups: groups 1 and 3 received solid abutments, and groups 2 and 4 received two-piece abutments. In groups 1 and 2, abutments were simply installed and uninstalled; torque-in and torque-out values were measured. In groups 3 and 4, abutments were installed, mechanically loaded and uninstalled; torque-in and torque-out values were measured. Under mechanical loading, two-piece abutments were frictionally locked into the implant; thus, data of group 4 were catalogued under two subgroups (4a: torque-out value necessary to loosen the fixation screw; 4b: torque-out value necessary to remove the abutment from the implant). Ten insertion/removal cycles were performed for every implant/abutment assembly. Data were analyzed with a mixed linear model (P[less than or equal to]0.05). Results: Torque loss was higher in groups 4a and 2 (over 30% loss), followed by group 1 (10.5% loss), group 3 (5.4% loss) and group 4b (39% torque gain). All the results were significantly different. As the number of insertion/removal cycles increased, removal torques tended to be lower. It was concluded that mechanical loading increased removal torque of loaded abutments in comparison with unloaded abutments, and removal torque values tended to decrease as the number of insertion/removal cycles increased. Author Affiliation: (1)Department of Dental Materials and Prostheses, School of Dentistry of Ribeirao Preto, University of Sao Paulo, Ribeirao Preto, Sao Paulo, Brazil Article History: Date:Accepted 5 November 2008 Article note: Correspondence to:, Dr. Ricardo Faria Ribeiro, Department of Dental Materials and Prostheses, School of Dentistry of Ribeirao Preto, University of Sao Paulo, Avenida do Cafe, s/n, Monte Alegre, CEP: 14040-904, Ribeirao Preto, Sao Paulo, Brazil, Tel: +55 (16) 3602 4005, Fax: +55 (16) 3602 0999, e-mail: rribeiro@forp.usp.br