title: Effect of abutment angulation on the strain on the bone around an implant in the anterior maxilla: a finite element study.
abstract: BACKGROUND
  Angled abutments are often used to restore dental implants placed in the anterior maxilla due to esthetic or spatial needs. The effect of abutment angulation on bone strain is unknown.
  
  
  OBJECTIVE
  The purpose of the current study was to measure and compare the strain distribution on the bone around an implant in the anterior maxilla using 2 different abutments by means of finite element analysis.
  
  
  METHODS
  Two-dimensional finite element models were designed using software (ANSYS) for 2 situations: (1) an implant with a straight abutment in the anterior maxilla, and (2) an implant with an angled abutment in the anterior maxilla. The implant used was 4x13 mm (MicroThread). The maxillary bone was modeled as type 3 bone with a cortical layer thickness of 0.5 mm. Oblique loads of 178 N were applied on the cingulum area of both models. Seven consecutive iterations of mesh refinement were performed in each model to observe the convergence of the results.
  
  
  RESULTS
  The greatest strain was found on the cancellous bone, adjacent to the 3 most apical microthreads on the palatal side of the implant where tensile forces were created. The same strain distribution was observed around both the straight and angled abutments. After several iterations, the results converged to a value for the maximum first principal strain on the bone of both models, which was independent of element size. Most of the deformation occurred in the cancellous bone and ranged between 1000 and 3500 microstrain. Small areas of cancellous bone experienced strain above the physiologic limit (4000 microstrain).
  
  
  CONCLUSIONS
  The model predicted a 15% higher maximum bone strain for the straight abutment compared with the angled abutment. The results converged after several iterations of mesh refinement, which confirmed the lack of dependence of the maximum strain at the implant-bone interface on mesh density. Most of the strain produced on the cancellous and cortical bone was within the range that has been reported to increase bone mass and mineralization.
authors.affiliation: Department of Prosthodontics, The University of Texas Health Science Center Dental Branch at Houston, Houston, TX, USA.
authors.forename: Xavier E
authors.initials: XE
authors.lastname: Saab
authors.forename: Jason A
authors.initials: JA
authors.lastname: Griggs
authors.forename: John M
authors.initials: JM
authors.lastname: Powers
authors.forename: Robert L
authors.initials: RL
authors.lastname: Engelmeier
mesh_terms: D000539:Alveolar Process / Q000502:physiology*; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D000044:Dental Abutments; D015921:Dental Implants; D003799:Dental Stress Analysis / Q000295:instrumentation / Q000379:methods*; D020342:Finite Element Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008437:Maxilla / Q000502:physiology; D016474:Weight-Bearing
chemical_list: D015921:Dental Implants