title: Influence of reinforcement on strains within maxillary implant overdentures.
abstract: OBJECTIVE
  The purpose of this study was to examine the influence of reinforcement of an embedded cast on the strains within maxillary implant overdentures.
  
  
  METHODS
  A maxillary edentulous model with implants placed bilaterally in the canine positions, dome-shaped copings, and experimental overdentures was fabricated. Rosette-type strain gauges were attached in the canine positions and at three points along the midline of the polished surface of the denture and connected to the sensor interface controlled by a personal computer. Experimental dentures with five different reinforcements were tested: without reinforcement; with a cast cobalt-chrome reinforcement over the residual ridge and the tops of the copings; with the same reinforcement from first molar to first molar, over the residual ridge and the tops of the copings; with the same reinforcement over the residual ridge and the sides of the copings; and with the same reinforcement from first molar to first molar, over the residual ridge and the sides of the copings. A vertical occlusal load of 49 N was applied to the first premolar and then to the first molar, and the strains were measured and compared by analysis of variance.
  
  
  RESULTS
  In both loading situations, significantly less strain was recorded in dentures with reinforcement than in those without reinforcement. When the first premolar was loaded on dentures with and without palatal reinforcement at the first premolars, the strains on the denture with reinforcement over the tops of the copings were significantly lower than on the denture with reinforcement over the sides of the copings at the canine position.
  
  
  CONCLUSIONS
  Cast reinforcement over the residual ridge and the top of copings embedded in an acrylic base reduced the strain from occlusal stress on maxillary implant overdentures.
authors.forename: Toshihito
authors.initials: T
authors.lastname: Takahashi
authors.forename: Tomoya
authors.initials: T
authors.lastname: Gonda
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Maeda
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D000465:Algorithms; D001732:Bite Force; D002858:Chromium Alloys / Q000737:chemistry; D000044:Dental Abutments; D003758:Dental Implantation, Endosseous / Q000295:instrumentation; D015921:Dental Implants; D003764:Dental Materials / Q000737:chemistry; D019094:Dental Prosthesis, Implant-Supported; D003819:Denture Bases; D003779:Denture Design; D003827:Denture, Complete, Upper; D003828:Denture, Overlay; D006801:Humans; D007575:Jaw, Edentulous / Q000503:physiopathology; D008437:Maxilla / Q000503:physiopathology; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D000180:Acrylic Resins; D002858:Chromium Alloys; D015921:Dental Implants; D003764:Dental Materials