title: Influence of apical root resection on the biomechanical response of a single-rooted tooth: a 3-dimensional finite element analysis.
abstract: BACKGROUND
  Apical root resection is a biologically essential component in endodontic microsurgery. However, because it reduces the total root length and supported root surface, it changes the biomechanical response of the tooth. The purpose of this study was to analyze the biomechanical effect of apical root resection and to compare apical root resection with periodontal bone loss from a biomechanical standpoint.
  
  
  METHODS
  Finite element models of the maxillary central incisor were reconstructed. First, preoperative and surgically treated models were generated to assess the factors altering the biomechanical response of the tooth. Then, apically resected models with different amounts of resection (3, 4, 5, 6, 7, and 8 mm) were created to estimate the clinically applicable limit of apical root resection. Periodontally destructed models with varying degrees of bone loss (0.5, 1, 1.5, 2, and 3 mm) were also created to compare the effect of apical root resection with periodontal bone loss. Stress distribution, tooth displacement, and effective crown-to-root ratio (α) were analyzed for each condition.
  
  
  RESULTS
  Apical root resection did not significantly alter the maximum von Mises stress or tooth displacement until it reached 6 mm (α = 0.67) when the tooth was supported by normal periodontium. In contrast, periodontal bone loss had a greater impact on biomechanical response change compared with apical root resection.
  
  
  CONCLUSIONS
  For a tooth supported by normal periodontium, 3 mm of apical root resection (α = 1.07) appeared to be mechanically acceptable. The biomechanical influence of apical root resection was weak compared with that of periodontal bone loss.
authors.affiliation: Department of Conservative Dentistry and Oral Science Research Center, College of Dentistry, Yonsei University, Seoul, Republic of Korea.
authors.forename: Youngjune
authors.initials: Y
authors.lastname: Jang
authors.affiliation: School of Mechanical Engineering, Yonsei University, Seoul, Republic of Korea.
authors.forename: Hyoung-Taek
authors.initials: HT
authors.lastname: Hong
authors.affiliation: Department of Conservative Dentistry and Oral Science Research Center, College of Dentistry, Yonsei University, Seoul, Republic of Korea. Electronic address: operatys16@yuhs.ac.
authors.forename: Byoung-Duck
authors.initials: BD
authors.lastname: Roh
authors.affiliation: School of Mechanical Engineering, Yonsei University, Seoul, Republic of Korea. Electronic address: hjchun@yonsei.ac.kr.
authors.forename: Heoung-Jae
authors.initials: HJ
authors.lastname: Chun
mesh_terms: D016301:Alveolar Bone Loss / Q000503:physiopathology; D001047:Apicoectomy / Q000379:methods*; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D020342:Finite Element Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007180:Incisor / Q000033:anatomy & histology / Q000502:physiology; D008954:Models, Biological; D010485:Periapical Periodontitis / Q000503:physiopathology; D010513:Periodontal Ligament / Q000502:physiology; D013314:Stress, Mechanical; D019228:Tooth Crown / Q000033:anatomy & histology; D014092:Tooth Root / Q000502:physiology*; D014945:Wound Healing / Q000502:physiology
keywords: Alveolar bone loss; apicoectomy; biomechanics; crown-to-root ratio; endodontic microsurgery; finite element analysis