title: Effects of preparation designs and adhesive systems on retention of class II amalgam restorations.
abstract: OBJECTIVE
  This study evaluated the effects of three preparation designs and the influence of an adhesive system in Class II amalgam restorations when a load was applied directly to the marginal ridge.
  
  
  METHODS
  Seventy-two sound caries-free maxillary molars were divided into 6 groups of 12 teeth. In groups 1 and 4, the preparation had an extension through the occlusal groove, whereas the other four groups used a proximal slot (box-only) preparation. Groups 2 and 5 had facial and lingual retention grooves that extended from the gingival floor to the occlusal surface, and groups 3 and 6 had slots without grooves. Teeth in groups 1, 2, and 3 were restored with amalgam and groups 4, 5, and 6 were restored with resin bonded amalgam. The marginal ridges of the restorations were loaded at an angle of 13.5 degrees to the long axis of the tooth in an Instron testing machine until failure.
  
  
  RESULTS
  Analysis of mean failure loads indicated that proximal slot preparations with retention grooves or occlusal extensions were statistically equivalent but significantly greater than proximal slots without grooves. The addition of an adhesive system improved fracture values for all three types of preparations.
  
  
  CONCLUSIONS
  When proximal caries was diagnosed and no occlusal caries was evident, a proximal slot amalgam restoration combined with retention grooves and an adhesive system was the appropriate choice.
authors.affiliation: Department of Conservative Dentistry, Faculty of Dentistry, University of Hacettepe, Ankara, Turkey.
authors.forename: J
authors.initials: J
authors.lastname: Görücü
authors.forename: M
authors.initials: M
authors.lastname: Tiritoglu
authors.forename: G
authors.initials: G
authors.lastname: Ozgünaltay
mesh_terms: D000704:Analysis of Variance; D003723:Dental Amalgam; D001840:Dental Bonding; D003737:Dental Cavity Preparation / Q000379:methods*; D018772:Dental Marginal Adaptation; D003793:Dental Restoration, Permanent / Q000379:methods*; D003799:Dental Stress Analysis; D017220:Dentin-Bonding Agents; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates; D019279:Resin Cements
chemical_list: C070606:Amalgambond; D017220:Dentin-Bonding Agents; D008689:Methacrylates; D019279:Resin Cements; D003723:Dental Amalgam