title: In vitro wear of indirect composite restoratives.
abstract: BACKGROUND
  Indirect composite restoratives have been improved in their wear resistance and physical properties. Several new indirect composites claim to be successfully used for full coverage crowns, but there is limited information for wear values of these new indirect composites.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the wear characteristics of 7 indirect composite restoratives and to compare them with a type III gold alloy by means of an in vitro wear test.
  
  
  METHODS
  Seven indirect composites (2 photopolymerized and 5 photo/heat-polymerized types) and a type III gold alloy (control) were used. Cylindrical Class I cavities (4-mm diameter and 3-mm depth) were prepared in occlusally flattened extracted human molars. Inlays with respective materials were fabricated on duplicated stone casts according to the manufacturers' instructions. Three types of in vitro wear tests were completed by use of the University of Alabama wear simulator. The wear tests included generalized wear as simulation of the wear during mastication, localized wear as simulation of attrition by occlusal contact, and antagonistic enamel wear, which simulated the wear of enamel created by direct contact with the restorative materials. Seven specimens were tested for each material and wear mode, and the wear depths were measured on profilometric tracings with a 2-dimensional profilometer with 1-microm accuracy. All data were analyzed by 1-way analysis of variance, and multiple comparisons were performed with Fisher's test, for which the significant level was set at.05.
  
  
  RESULTS
  The gold alloy control exhibited a very small amount of wear in both generalized wear (0.2 +/- 0.1 microm) and localized wear (13.8 +/- 5.0 microm) as compared with all composite specimens. The antagonistic enamel wear of gold alloy was similar with the value of Sculpture. The material group, which was post polymerized or post heat-treated, included BelleGlass, Sculpture, Estenia, and Cristobal+ and showed small values ranging from 1.6 to 2.2 microm in the generalized wear. For the localized wear, Estenia exhibited the minimum value (12.8 +/- 4.9 microm) that was statistically the same as the value of the gold alloy control. However, Estenia exhibited the greatest antagonistic enamel wear value (66.0 +/- 14.0 microm) of all materials tested in this study. It was statistically significant with other materials (P</=.05).
  
  
  CONCLUSIONS
  Within the limitations of this study, it was concluded that some indirect composite restoratives have similar wear resistance to the type III gold alloy tested. Antagonistic enamel was abraded more by highly filled composite materials.
authors.affiliation: School of Dentistry, University of Alabama at Birmingham, Birmingham, Ala 35294-0007, USA. shiro@mail.dental.uab.edu
authors.forename: Shiro
authors.initials: S
authors.lastname: Suzuki
authors.forename: Eiichi
authors.initials: E
authors.lastname: Nagai
authors.forename: Yohsuke
authors.initials: Y
authors.lastname: Taira
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Minesaki
mesh_terms: D000704:Analysis of Variance; D002516:Ceramics; D016009:Chi-Square Distribution; D003188:Composite Resins; D019554:Dental Restoration Wear; D003799:Dental Stress Analysis; D005899:Glass Ionomer Cements; D006047:Gold Alloys; D006801:Humans; D007284:Inlays / Q000009:adverse effects; D008422:Materials Testing; D008689:Methacrylates; D008963:Molar; D011140:Polyurethanes; D012823:Silicate Cement; D013499:Surface Properties; D019217:Tooth Attrition / Q000209:etiology*
chemical_list: D003188:Composite Resins; C451599:Cristobal; C113550:FiberKor, sculpture; D005899:Glass Ionomer Cements; D006047:Gold Alloys; D008689:Methacrylates; D011140:Polyurethanes; C113676:Solidex; C110370:belleGlass; C111282:dental polyglass; C091839:urethanetrimethacrylate; D012823:Silicate Cement