title: Effect of retention design of artificial teeth and implant-supported titanium CAD-CAM structures on fracture resistance.
abstract: BACKGROUND
  For implant-supported hybrid prostheses, high mastication forces and reduced acrylic resin thickness over a metal substructure often cause failures arising from tooth or resin fractures. To assay fracture resistance of artificial teeth and resin in implant-supported hybrid prostheses in relation to the titanium structure and retention design supporting teeth.
  
  
  METHODS
  40 specimens bearing incisors were divided into four groups according to the titanium structure supporting the teeth and the type of load force applied: Group I (Control; n=10): Application of static loading to ten incisors set over a metal structure with internal retention. Group II (Control; n=10): Application of static loading to ten incisors set over a metal structure with external retention. The remaining study specimens (n=20) were subjected to 120,000 masticatory and thermal cycles in a chewing simulator. Afterwards, static loading was applied until the point of fracture using an Instron machine. Group III (Study; n=10): Application of dynamic and static loading to ten incisors set over a metal structure with internal retention. Group IV (Study; n=10): Application of dynamic and static loading to ten incisors set over a metal structure with external retention. Data obtained for the four groups was analyzed and compared, determining the type of fracture (cohesive or adhesive) using a reflected light microscope.
  
  
  RESULTS
  Statistical analysis confirmed that there were significant differences in fracture resistance between the four groups. External retention was found to have more fracture resistance than the internal retention.
  
  
  CONCLUSIONS
  Hybrid prostheses with titanium substructures and external retention obtained significantly better results than samples with internal retention.
  
  
  BACKGROUND
  Chewing simulator, thermocycler, fatigue, implant-supported hybrid prosthesis, acrylic teeth, fracture, metal structure design.
authors.affiliation: Prosthodontics and Occlusion, University of Valencia, Valencia, Spain.
authors.forename: Kristin
authors.initials: K
authors.lastname: Ladetzki
authors.affiliation: Prosthodontics and Occlusion, University of Valencia, Valencia, Spain.
authors.forename: Rocío
authors.initials: R
authors.lastname: Mateos-Palacios
authors.affiliation: Dental Materials, University of Valencia, Valencia, Spain.
authors.forename: Agustín
authors.initials: A
authors.lastname: Pascual-Moscardó
authors.affiliation: Prosthodontics and Occlusion, University of Valencia, Valencia, Spain.
authors.forename: Eduardo J
authors.initials: EJ
authors.lastname: Selva-Otaolaurruchi