title: Durability of resin composite restorations in high C-factor cavities: a 12-year follow-up.
abstract: OBJECTIVE
  Polymerization shrinkage and shrinkage stress has been considered as one of the main disadvantages of resin composite restorations. Cavities with high C-factors increase the risk for interfacial failures. Several restorative techniques have been suggested to decrease the shrinkage stress. The purpose of this study was to evaluate the durability of techniques as oblique layering, indirect curing and/or a laminate with a poly-acid modified resin composite in direct Class I resin composite restorations in a 12-year follow-up.
  
  
  METHODS
  Each of 29 patients received one or two pair(s) rather extensive Class I restorations. The first restoration was a poly-acid modified resin composite/resin composite sandwich restoration and the second a direct resin composite restoration. Both restorations, except for the laminate layer, were placed with oblique layering and two-step curing technique. 90 restorations were evaluated annually with slightly modified USPHS criteria during 12 years.
  
  
  RESULTS
  At 12 years, 38 pairs were evaluated. Two cases of slight post-operative sensitivity were observed in one patient. A cumulative failure rate of 2.4% was observed for both the resin composite and the laminate restorations. One laminate restoration showed non-acceptable color match, but was not replaced and one resin composite restoration showed a chip fracture. Five restorations were replaced due to primary proximal caries.
  
  
  CONCLUSIONS
  The high failure rate expected in the high C-factor Class I cavity, associated with polymerization shrinkage and shrinkage stress, were not observed. The techniques used resulted in an excellent durability for the Class I resin composite restorations.
authors.affiliation: Institution of Odontology, Dental School Umeå, Umeå University, 901 87 Umeå, Sweden. Jan.van.Dijken@odont.umu.se
authors.forename: Jan W V
authors.initials: JW
authors.lastname: van Dijken
mesh_terms: D000096:Acetone / Q000737:chemistry; D000328:Adult; D000368:Aged; D001641:Bicuspid / Q000473:pathology; D003116:Color; D020770:Compomers / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003731:Dental Caries / Q000145:classification / Q000628:therapy*; D018772:Dental Marginal Adaptation; D003764:Dental Materials / Q000737:chemistry*; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000145:classification / Q000379:methods*; D003807:Dentin Sensitivity / Q000209:etiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D055115:Light-Curing of Dental Adhesives / Q000379:methods; D008137:Longitudinal Studies; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D008963:Molar / Q000473:pathology; D011108:Polymers / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D011446:Prospective Studies; D012008:Recurrence; D019233:Retreatment; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D020770:Compomers; D003188:Composite Resins; D003764:Dental Materials; C088486:Dyract; D011108:Polymers; D011109:Polymethacrylic Acids; C088833:Prisma TPH resin composite; C444444:prime and bond 2.1; D000096:Acetone