title: Resinous denture base fracture resistance: effects of thickness and teeth.
abstract: OBJECTIVE
  Fracture is a frequent complication of resinous prostheses. The purpose of this study was to evaluate the effect of thickness on flexural strength of a resinous prosthesis containing a prosthetic tooth.
  
  
  METHODS
  Beam-shaped specimens 65-mm long, 12-mm wide, and 1, 2, 3, 4, or 6 mm in thickness were made from high-impact strength polymethyl methacrylate denture base material, each containing a resin-based molar prosthetic tooth at the center of the beam. A group of 3-mm-thick specimens without a prosthetic tooth (n = 7) were also made. Specimens were aged artificially, loaded in three-point flexure, examined fractographically, and analyzed.
  
  
  RESULTS
  The 1- and 2-mm-thick beams underwent considerable deformation at low loads. Maximum loads varied considerably from 0.6 kg (1-mm beams) to 38 kg (6-mm beams). The 3-, 4-, and 6-mm beam groups all underwent brittle fracture, with mean relative flexural strengths of approximately 73 MPa. Denture teeth reduced the relative flexural strength of resin beams by 0.7 x. Fracture initiation sites were generally at tiny surface defects, but did not directly involve denture teeth. Denture resin fracture toughness was 3.2 MPa m1/2, and modulus of rupture was 104 MPa.
  
  
  CONCLUSIONS
  Denture teeth substantially decreased the strength of resinous beams. Increased thickness markedly increased the load-bearing capacity of resinous beams containing denture teeth. Beams less than 2 mm in thickness with denture teeth were weakened substantially more than comparable beams of 2 mm or more in thickness. Surface finish was of critical importance. Fracture toughness was calculated fractographically, facilitating future forensic examination of clinically failed resinous prostheses.
authors.affiliation: Department of Prosthodontics, New York University College of Dentistry, New York, New York, USA.
authors.forename: Mijin
authors.initials: M
authors.lastname: Choi
authors.forename: Varun
authors.initials: V
authors.lastname: Acharya
authors.forename: Robert W
authors.initials: RW
authors.lastname: Berg
authors.forename: Joshua
authors.initials: J
authors.lastname: Marotta
authors.forename: Chad C
authors.initials: CC
authors.lastname: Green
authors.forename: Joao V
authors.initials: JV
authors.lastname: Barbizam
authors.forename: Shane N
authors.initials: SN
authors.lastname: White
mesh_terms: D003764:Dental Materials / Q000737:chemistry*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000295:instrumentation; D003819:Denture Bases; D055119:Elastic Modulus; D006801:Humans; D008963:Molar; D018583:Pliability; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors; D014093:Tooth, Artificial; D014867:Water / Q000737:chemistry
chemical_list: D003764:Dental Materials; D014867:Water; D019904:Polymethyl Methacrylate