title: Influence of apical root resection on the biomechanical response of a single-rooted tooth-part 2: apical root resection combined with periodontal bone loss.
abstract: BACKGROUND
  In a clinical situation, an apically resected tooth is often accompanied by a varying degree of periodontal bone loss. The purpose of this study was to assess the influence of apical root resection combined with periodontal bone loss on the biomechanical response of a single-rooted tooth.
  
  
  METHODS
  A basic intact model and a basic apically resected model of the upper central incisor were selected for the numerical analysis. From each basic model, 6 models were developed assuming different amounts of periodontal bone loss (0, 0.5, 1, 1.5, 2, and 3 mm). Maximum von Mises stress (σ max), maximum tooth displacement (ΔR max), and effective crown-to-root ratio (α) were calculated for each condition.
  
  
  RESULTS
  There were only marginal differences (a 2.1% difference in σ max and a 16.9% difference in ΔR max) between the biomechanical responses of the intact model and the apically resected model when the tooth was supported by a normal periodontium. However, when destruction of the periodontium was assumed, the intact model and the apically resected model responded differently. The difference increased as the periodontal bone loss progressed, resulting in a 68.7% difference in σ max and a 56.3% difference in ΔR max when the periodontal bone loss increased to 3 mm (α = 0.48).
  
  
  CONCLUSIONS
  Although the biomechanical response of an apically resected tooth was relatively stable when the tooth was supported by a normal periodontium, the apically resected tooth showed a more deteriorated response compared with the intact tooth as the periodontal bone loss progressed.
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: 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
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
mesh_terms: D016301:Alveolar Bone Loss / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D003799:Dental Stress Analysis; D020342:Finite Element Analysis; D006801:Humans; D008954:Models, Biological; D013314:Stress, Mechanical; D019227:Tooth Apex / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery*; D019228:Tooth Crown / Q000473:pathology / Q000503:physiopathology
keywords: Alveolar bone loss; apicoectomy; biomechanics; crown-to-root ratio; endodontic microsurgery; finite element analysis