title: Effect of interfragmentary gap on the mechanical behavior of mandibular angle fracture with three fixation designs: A finite element analysis.
abstract: BACKGROUND
  The aim of this study was to simulate stress and strain distribution numerically on a normal mandible under physiological occlusal loadings. The results were compared with those of mandibles that had an angle fracture stabilized with different fixation designs under the same loadings. The amount of displacement at two interfragmentary gaps was also studied.
  
  
  METHODS
  A three-dimensional (3D) virtual mandible was reconstructed with an angle fracture that had a fracture gap of either 0.1 or 1 mm. Three types of plate fixation designs were used: Type I, a miniplate was placed across the fracture line following the Champy technique; Type II, two miniplates were used; and Type III, a reconstruction plate was used on the inferior border of the mandible. Loads of 100 and 500 N were applied to the models. The maximum von Mises stress, strain, and displacement were computed using finite element analysis. The results from the control and experimental groups were analyzed and compared.
  
  
  RESULTS
  The results demonstrated that high stresses and strains were distributed to the condylar and angular areas regardless of the loading position. The ratio of the plate/bone average stress ranged from 215% (Type II design) to 848% (Type I design) irrespective of the interfragmentary gap size. With a 1-mm fracture gap, the ratio of the plate/bone stress ranged from 204% (Type II design) to 1130% (Type I design). All strains were well below critical bone strain thresholds. Displacement on the cross-sectional mapping at fracture interface indicated that uneven movement occurred in x, y, and z directions.
  
  
  CONCLUSIONS
  Interfragmentary gaps between 0.1 and 1 mm did not have a substantial effect on the average stress distribution to the fractured bony segments; however, they had a greater effect on the stress distribution to the plates and screws. Type II fixation was the best mechanical design under bite loads. Type I design was the least stable system and had the highest stress distribution and the largest displacement at the fracture site.
authors.affiliation: Department of Comprehensive Care, Case Western Reserve University, School of Dental Medicine, 10900 Euclid Ave., Cleveland, OH 44106-4905, USA. Electronic address: rxw26@case.edu.
authors.forename: Russell
authors.initials: R
authors.lastname: Wang
authors.affiliation: Department of Mechanical Engineering, Key Laboratory of E&M, Zhejiang University of Technology, 18 Tsao Wong Road, Hangzhou, Zhejiang 310014, China.
authors.forename: Yunfeng
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Orthopedic Surgery, University Hospitals Case Medical Center, 11100 Euclid Ave, Cleveland, OH 44016, USA.
authors.forename: Joanne Helen
authors.initials: JH
authors.lastname: Wang
authors.affiliation: Department of Oral and Maxillofacial Surgery, Case Western Reserve University, School of Dental Medicine, 10900 Euclid Ave., Cleveland, OH 44106-4905, USA.
authors.forename: Dale Allen
authors.initials: DA
authors.lastname: Baur
mesh_terms: D003198:Computer Simulation; D005593:Fracture Fixation, Internal / Q000379:methods; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008334:Mandible / Q000502:physiology* / Q000601:surgery; D008338:Mandibular Injuries / Q000503:physiopathology* / Q000601:surgery; D008875:Middle Aged; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed
keywords: Finite element analysis; Fixation designs; Interfragmentary gap; Mandibular angle fracture; Stress distribution