title: Effects of clip materials on stress distribution to maxillary implant overdentures with bar attachments.
abstract: BACKGROUND
  Fracture of maxillary implant overdentures (IODs) is a frequent complication. However, no studies have examined the effects of clip materials on the stress applied to maxillary IODs.
  
  
  OBJECTIVE
  The purpose of this study was to investigate the effects of clip materials for bar attachments on the stress applied to maxillary IODs without palatal coverage.
  
  
  METHODS
  This study included finite element analysis and a model study. An edentulous maxillary model with 4 implants and an experimental overdenture with bar attachments was fabricated. Strain gauges were attached on the denture surface adjacent to the end of each clip. Four clip conditions (n=5) were prepared: 3 plastic clips, 1 plastic clip, 3 metal clips, and 1 metal clip. A vertical load of 50 N was applied on the IOD. The maximum principle strain (MPS) was statistically analyzed by 2-way ANOVA and the post hoc Tukey HSD tests with clip materials and clip numbers as factors (α=.05).
  
  
  RESULTS
  The greatest stress was observed on the resin surface around the end of the clip on the loaded side. The MPSs between both clip materials (P=.048) and numbers (P<.001) differed significantly on the palatal side of the end of the center clip on the loaded side: the MPSs of the metal clips were significantly larger than those of the plastic clips, and the MPS of 1 clip was significantly larger than for 3 clips.
  
  
  CONCLUSIONS
  The stress around plastic clips tended to be lower than that around metal clips.
authors.affiliation: Graduate student, Gerodontology and Oral Rehabilitation, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Yushima, Bunkyo, Tokyo, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Tanoue
authors.affiliation: Assistant Professor, Gerodontology and Oral Rehabilitation, Tokyo Medical and Dental University, Tokyo, Japan. Electronic address: m.kanazawa.gerd@tmd.ac.jp.
authors.forename: Manabu
authors.initials: M
authors.lastname: Kanazawa
authors.affiliation: Resident, Gerodontology and Oral Rehabilitation, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Shin
authors.initials: S
authors.lastname: Takeshita
authors.affiliation: Professor, Gerodontology and Oral Rehabilitation, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Minakuchi
mesh_terms: D015921:Dental Implants; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis; D003779:Denture Design; D003781:Denture Retention / Q000295:instrumentation*; D003828:Denture, Overlay; D008422:Materials Testing; D013525:Surgical Instruments; D013718:Tensile Strength
chemical_list: D015921:Dental Implants