Alejandro Sánchez-Ayala1, Alfonso Sánchez-Ayala2, Rafaela Cristina Kolodzejezyk1, Vanessa Migliorini Urban1, Manuel Óscar Lagravère1, Nara Hellen Campanha3. 1. Department of Dentistry, University of Ponta Grossa, Avenida General Carlos Cavalcanti n° 4748, Bloco M, Sala 64A, 84030-900, Ponta Grossa, Paraná, Brazil. 2. Department of Dentistry, University of Ponta Grossa, Avenida General Carlos Cavalcanti n° 4748, Bloco M, Sala 64A, 84030-900, Ponta Grossa, Paraná, Brazil. snzcd@uepg.br. 3. Orthodontic Graduate Program, University of Alberta, 116 St & 85 Ave, T6G 2R3, Edmonton, Alberta, Canada.
Abstract
PURPOSE: Masticatory muscles are physically affected by several skeletal features. The muscle performance depends on muscle size, intrinsic strength, fiber direction, moment arm, and neuromuscular control. To date, for the masticatory apparatus, only a two-dimensional cephalometric method for assessing the mechanical advantage, which is a measure for the ratio of the output force to the input force in a system, is available. This study determined the reliability and errors of a three-dimensional (3D) mechanical advantage calculation for the masticatory system. METHODS: Using cone-beam computed tomography images from teenage patients undergoing orthodontic treatments, 36 craniofacial landmarks were identified, and the moment arms for seven muscles and their load moment arms (biomechanical variables) were determined. The 3D mechanical advantage for each muscle was calculated. This procedure was repeated by three examiners. Reliability was verified using the intraclass correlation coefficient (ICC) and the errors by calculating the absolute differences, variance estimator and coefficient of variation (CV). RESULTS: Landmark coordinates demonstrated excellent intra- and interexaminer reliability (ICC 0.998-1.000; p < 0.0001). Intraexaminer data showed errors < 1.5 mm. Unsatisfactory interexaminer errors ranged from 1.51-5.83 mm. All biomechanical variables presented excellent intraexaminer reliability (ICC 0.919-1.000, p < 0.0001; CV < 7%). Interexaminer results were almost excellent, but with lower values (ICC 0.750-1.000, p < 0.0001; CV < 10%). However, the muscle moment arm and 3D mechanical advantage of the lateral pterygoid muscles had ICCs < 0.500 (p < 0.05) and CV < 30%. Intra- and interexaminer errors were ≤ 0.01 and ≤ 0.05, respectively. CONCLUSIONS: Both landmarks and biomechanical variables showed high reliability and acceptable errors. The proposed method is viable for the 3D mechanical advantage measure.
PURPOSE: Masticatory muscles are physically affected by several skeletal features. The muscle performance depends on muscle size, intrinsic strength, fiber direction, moment arm, and neuromuscular control. To date, for the masticatory apparatus, only a two-dimensional cephalometric method for assessing the mechanical advantage, which is a measure for the ratio of the output force to the input force in a system, is available. This study determined the reliability and errors of a three-dimensional (3D) mechanical advantage calculation for the masticatory system. METHODS: Using cone-beam computed tomography images from teenage patients undergoing orthodontic treatments, 36 craniofacial landmarks were identified, and the moment arms for seven muscles and their load moment arms (biomechanical variables) were determined. The 3D mechanical advantage for each muscle was calculated. This procedure was repeated by three examiners. Reliability was verified using the intraclass correlation coefficient (ICC) and the errors by calculating the absolute differences, variance estimator and coefficient of variation (CV). RESULTS: Landmark coordinates demonstrated excellent intra- and interexaminer reliability (ICC 0.998-1.000; p < 0.0001). Intraexaminer data showed errors < 1.5 mm. Unsatisfactory interexaminer errors ranged from 1.51-5.83 mm. All biomechanical variables presented excellent intraexaminer reliability (ICC 0.919-1.000, p < 0.0001; CV < 7%). Interexaminer results were almost excellent, but with lower values (ICC 0.750-1.000, p < 0.0001; CV < 10%). However, the muscle moment arm and 3D mechanical advantage of the lateral pterygoid muscles had ICCs < 0.500 (p < 0.05) and CV < 30%. Intra- and interexaminer errors were ≤ 0.01 and ≤ 0.05, respectively. CONCLUSIONS: Both landmarks and biomechanical variables showed high reliability and acceptable errors. The proposed method is viable for the 3D mechanical advantage measure.
Authors: G J Dicker; M Tuijt; J H Koolstra; R A Van Schijndel; J A Castelijns; D B Tuinzing Journal: Int J Oral Maxillofac Surg Date: 2012-04-21 Impact factor: 2.789
Authors: G J Dicker; J H Koolstra; J A Castelijns; R A Van Schijndel; D B Tuinzing Journal: Int J Oral Maxillofac Surg Date: 2012-03-12 Impact factor: 2.789
Authors: Manuel O Lagravère; Jillian M Gordon; Ines H Guedes; Carlos Flores-Mir; Jason P Carey; Giseon Heo; Paul W Major Journal: Angle Orthod Date: 2009-11 Impact factor: 2.079