title: Stiffness of different designs and cross-sections of maxillary and mandibular major connectors of removable partial dentures.
abstract: BACKGROUND
  Major connectors of removable partial dentures must distribute forces bilaterally without damaging the supporting tissues.
  
  
  OBJECTIVE
  This study investigated which design and cross-sectional shape of major connectors most favorably influence rigidity and flexibility.
  
  
  METHODS
  Five designs for maxillary removable partial denture major connectors and 5 lingual bar major connectors of different cross-sectional forms were cast in chrome cobalt alloy on a master cast. Points M and P, which represented the position of the first premolar and second molar teeth, were positioned 20 mm apart on the casting. Vertical and horizontal forces were applied to each point while the opposite side was gripped in an Instron testing machine. A force-deflection curve was obtained for each loading point. Mean stiffness values were obtained for loading in compression and torsion.
  
  
  RESULTS
  Values for torsional loading simulating vertical forces were lower when compared with values obtained for compression loading that simulated horizontal occlusal forces. Differences in stiffness were greater in mandibular major connectors loaded at M and P. The half pear-shaped cross section was the stiffest.
  
  
  CONCLUSIONS
  In the maxillary arch, the most rigid major connector was the anteroposterior palatal bar combination placed on different horizontal and vertical planes. The most flexible was the U-shaped design. In the mandibular arch, the most important factor in achieving rigidity was the cross-sectional shape of the major connector. The half pear-shaped cross section proved to be the most rigid.
authors.affiliation: The Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Z
authors.initials: Z
authors.lastname: Ben-Ur
authors.forename: E
authors.initials: E
authors.lastname: Mijiritsky
authors.forename: C
authors.initials: C
authors.lastname: Gorfil
authors.forename: T
authors.initials: T
authors.lastname: Brosh
mesh_terms: D001641:Bicuspid; D001732:Bite Force; D002858:Chromium Alloys / Q000737:chemistry*; D019245:Compressive Strength; D003799:Dental Stress Analysis / Q000295:instrumentation; D003779:Denture Design; D003832:Denture, Partial, Removable; D004548:Elasticity; D006801:Humans; D008334:Mandible; D008422:Materials Testing; D008437:Maxilla; D008963:Molar; D018583:Pliability; D013314:Stress, Mechanical; D013499:Surface Properties; D019415:Torque
chemical_list: D002858:Chromium Alloys