title: A novel dual material mouthguard for patients with dental implants.
abstract: OBJECTIVE
  Dental implant-supported reconstructions demonstrate significantly less physiological flexibility for loading and traumatic forces compared with a normal dentition because of their rigid integration with the adjacent bone. Ethylene vinyl acetate (EVA) material has become widely accepted as a mouthguard material; however, many studies indicate the necessity of improving the impact absorption ability by considering the design and developing new materials. The aim of this study was to compare the shock-absorbing ability of a novel dual component material comprising EVA and porous rubber with that of EVA alone.
  
  
  METHODS
  Three groups of samples were tested: Group 1 = EVA (thickness, 4 mm), Group 2 = type 1 material (2-mm thick porous rubber sheet sandwiched between two sheets of 1-mm thick EVA sheets), and Group 3 = type 2 material (1-mm thick porous rubber sheet sandwiched between EVA sheets with 1 and 2-mm thickness, respectively). Shock absorption was determined by means of a hammer impact testing device equipped with strain gauge, accelerator, and load cell.
  
  
  RESULTS
  The value of shock-absorbing ability of group 2 (40.6 ± 12.5%) was significantly higher than those of group 1 (15.6 ± 2.1%) and group 3 (21.2 ± 9.2%). The material with thicker rubber sheet showed significantly higher shock-absorbing ability compared with that of the material with thinner rubber sheet.
  
  
  CONCLUSIONS
  The novel dual material was superior to conventional EVA material in shock-absorbing ability depending on the thickness of porous rubber, and it may be potentially effective as mouthguard material, in particular, for patients wearing implant-supported constructions.
authors.affiliation: Department of Biomaterials, Sahlgrenska Academy at University of Gothenburg, Göteborg, Sweden. miyahara.irm@tmd.ac.jp
authors.forename: Takayuki
authors.initials: T
authors.lastname: Miyahara
authors.forename: Christer
authors.initials: C
authors.lastname: Dahlin
authors.forename: Silvia
authors.initials: S
authors.lastname: Galli
authors.forename: Shima
authors.initials: S
authors.lastname: Parsafar
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Koizumi
authors.forename: Shohei
authors.initials: S
authors.lastname: Kasugai
mesh_terms: D000704:Analysis of Variance; D015921:Dental Implants; D003799:Dental Stress Analysis; D004867:Equipment Design; D006801:Humans; D008422:Materials Testing / Q000379:methods; D009064:Mouth Protectors; D011145:Polyvinyls; D012408:Rubber; D013314:Stress, Mechanical; D018677:Tooth Injuries / Q000517:prevention & control
chemical_list: D015921:Dental Implants; D011145:Polyvinyls; D012408:Rubber