title: Mechanical properties of hard resins for crowns and bridges.
abstract: OBJECTIVE
  Hard resins for crowns and bridges are widely used for esthetic restorations. The objective of this study was to evaluate the mechanical properties of new commercial hard resins and to compare the results with those of the other hard resins previously investigated.
  
  
  METHODS
  Dentin and enamel made with two new hard resins (Epricord: EP, Kuraray, Co., Ltd., Osaka, Japan and Prossimo: PR, GC, Co., Ltd., Tokyo, Japan) were used in this study. Regarding the fundamental characteristics, the thermal expansion/shrinkage coefficient, the filler content, the polymerization shrinkage, and the wear were examined. Regarding the strength of resin, the bending strength, hardness, compression strength, elastic modulus, and fracture strength of a jacket crown were measured.
  
  
  RESULTS
  These resins showed comparatively lower levels than the other hard resins regarding the bending strength, hardness, compression strength, and fracture strength of the jacket crown. The total filler content rate and wear amount of these resins exhibited similar values to those of the other resins. The thermal expansion/ shrinkage coefficients of these resins exhibited higher values than those of the other resins. EP showed a different tendency from PR about the compression strength, elastic modulus, and polymerization shrinkage.
  
  
  CONCLUSIONS
  PR and EP did not show dramatically better physical properties. However, the results of each examination in this study may be acceptable clinically. The results of each investigation changed according to the products used, and proper use for each case and application was suggested.
authors.affiliation: Division of Fixed Prosthodontics, Department of Restorative Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan. izumida@mail.tains.tohoku.ac.jp
authors.forename: Akio
authors.initials: A
authors.lastname: Izumida
authors.forename: Masanobu
authors.initials: M
authors.lastname: Yoda
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Inagaki
authors.forename: Joji
authors.initials: J
authors.lastname: Toyoda
authors.forename: Minoru
authors.initials: M
authors.lastname: Ishibashi
authors.forename: Shin
authors.initials: S
authors.lastname: Kasahara
authors.forename: Kohei
authors.initials: K
authors.lastname: Kimura
mesh_terms: D003442:Crowns; D003829:Denture, Partial; D004548:Elasticity; D006244:Hardness; D008422:Materials Testing; D055595:Mechanical Phenomena; D012117:Resins, Synthetic
chemical_list: D012117:Resins, Synthetic