title: Influence of tapered and external hexagon connections on bone stresses around tilted dental implants: three-dimensional finite element method with statistical analysis.
abstract: BACKGROUND
  The purpose of this study is to analyze the tension distribution on bone tissue around implants with different angulations (0°, 17°, and 30°) and connections (external hexagon and tapered) through the use of three-dimensional finite element and statistical analyses.
  
  
  METHODS
  Twelve different configurations of three-dimensional finite element models, including three inclinations of the implants (0°, 17°, and 30°), two connections (an external hexagon and a tapered), and two load applications (axial and oblique), were simulated. The maximum principal stress values for cortical bone were measured at the mesial, distal, buccal, and lingual regions around the implant for each analyzed situation, totaling 48 groups. Loads of 200 and 100 N were applied at the occlusal surface in the axial and oblique directions, respectively. Maximum principal stress values were measured at the bone crest and statistically analyzed using analysis of variance. Stress patterns in the bone tissue around the implant were analyzed qualitatively.
  
  
  RESULTS
  The results demonstrated that under the oblique loading process, the external hexagon connection showed significantly higher stress concentrations in the bone tissue (P <0.05) compared with the tapered connection. Moreover, the buccal and mesial regions of the cortical bone concentrated significantly higher stress (P <0.005) to the external hexagon implant type. Under the oblique loading direction, the increased external hexagon implant angulation induced a significantly higher stress concentration (P = 0.045).
  
  
  CONCLUSIONS
  The study results show that: 1) the oblique load was more damaging to bone tissue, mainly when associated with external hexagon implants; and 2) there was a higher stress concentration on the buccal region in comparison to all other regions under oblique load.
authors.affiliation: Department of Dental Materials and Prosthodontics, Dental School of Araçatuba, UNESP - Univ Estadual Paulista, São Paulo, Brazil.
authors.forename: Daniel Augusto
authors.initials: DA
authors.lastname: de Faria Almeida
authors.forename: Eduardo Piza
authors.initials: EP
authors.lastname: Pellizzer
authors.forename: Fellippo Ramos
authors.initials: FR
authors.lastname: Verri
authors.forename: Joel Ferreira
authors.initials: JF
authors.lastname: Santiago
authors.forename: Paulo Ségio Perri
authors.initials: PS
authors.lastname: de Carvalho
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D000539:Alveolar Process / Q000502:physiology; D001732:Bite Force; D002858:Chromium Alloys / Q000737:chemistry; D003198:Computer Simulation; D059605:Dental Implant-Abutment Design; D003758:Dental Implantation, Endosseous / Q000379:methods*; D015921:Dental Implants; D003764:Dental Materials / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry; D055119:Elastic Modulus; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008954:Models, Biological; D016012:Poisson Distribution; D017680:Potassium Compounds / Q000737:chemistry; D013314:Stress, Mechanical; D014025:Titanium / Q000737:chemistry; D015036:Zinc Phosphate Cement / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D002858:Chromium Alloys; D015921:Dental Implants; D003764:Dental Materials; D017680:Potassium Compounds; D003776:Dental Porcelain; C016447:feldspar; D015036:Zinc Phosphate Cement; D014025:Titanium