title: Biomechanical comparison of a single short and wide implant with monocortical or bicortical engagement in the atrophic posterior maxilla and a long implant in the augmented sinus.
abstract: OBJECTIVE
  The present study investigated the biomechanical interactions of a monocortically or bicortically engaged short and wide implant in the atrophic posterior maxilla and compared them to those of a long implant in the augmented sinus under different loading conditions via a nonlinear finite element (FE) approach.
  
  
  METHODS
  Nonlinear FE models of a single implant in the posterior maxilla were constructed for the following conditions: (1) A monocortically engaged 5-mm-long, 7-mm-wide implant with an internal tripodgrip abutment connection (SIT-1), (2) a bicortically engaged 6-mm-long, 7-mm-wide implant with internal tripod-grip abutment connection (SIT-2), and (3) a 13-mm-long, 4.5-mm-wide implant with an internal-hexagon abutment connection in an augmented sinus. Simulated loads of 150 N were applied axially at the central fossa, off-axis at the buccal and palatal cusps, and toward the axis at the buccal and palatal cusps.
  
  
  RESULTS
  The simulated results showed that loading condition was the main factor influencing the mechanical responses. Oblique occlusal forces increased implant stress and stress/strain values for the surrounding bone. The use of a long implant decreased the implant stress but increased the bone stress/strain values relative to a short and wide implant. The SIT-1 and SIT-2 implants increased the implant stress on average by 2.94 and 2.67 fold, respectively. However, the SIT-2 implant reduced the average stress and strain in bone by 37%, and the SIT-1 implant reduced average stress by 33% and average strain by 32%.
  
  
  CONCLUSIONS
  Placement of a short and wide implant in the atrophic posterior maxilla may be a possible alternative for reducing the strain/stress on the surrounding bone. Detrimental off-axis loads should always be minimized to prevent extraordinarily high bone strain and stress.
authors.affiliation: Chang Gung Memorial Hospital, Department of Periodontics, Chang Gung University, Graduate Institute of Dental and Craniofacial Sciences, Tao-yuan, Taiwan.
authors.forename: Shih-Hao
authors.initials: SH
authors.lastname: Chang
authors.forename: Chun-Li
authors.initials: CL
authors.lastname: Lin
authors.forename: Yang-Sung
authors.initials: YS
authors.lastname: Lin
authors.forename: Shue-Sang
authors.initials: SS
authors.lastname: Hsue
authors.forename: Shiang-Rung
authors.initials: SR
authors.lastname: Huang
mesh_terms: D001284:Atrophy; D001732:Bite Force; D015921:Dental Implants; D017267:Dental Prosthesis Design; D003799:Dental Stress Analysis / Q000379:methods; D020342:Finite Element Analysis; D006801:Humans; D008437:Maxilla / Q000473:pathology*; D059546:Sinus Floor Augmentation; D013314:Stress, Mechanical
chemical_list: D015921:Dental Implants