title: Tooth deformation patterns in molars after composite restoration.
abstract: OBJECTIVE
  Residual stresses from polymerization shrinkage in composite restorations deform a tooth. This may cause debonding, enamel crack propagation, and post-operative sensitivity. Deformation due to shrinkage has been measured previously at a few discrete points. The purpose of this study was to analyze cuspal deformation pattern of the occlusal portion of molars for various cavity types and sizes after restoration with a light-initiated composite.
  
  
  METHODS
  Five extracted human molars were successively prepared as Class I, Class II OM, large Class II OM, and large Class II MOD. The cavities were filled with a light-curing composite using a dentin adhesive system. The occlusal portion of the unrestored cavity and the restoration were digitized with a profilometer. The digitized data of the unrestored and restored tooth were used to calculate the cuspal contour change with Cumulus software. Deformation was visualized as a color contour map.
  
  
  RESULTS
  Cuspal deformation showed up in the contour map as a reduction of buccal and lingual contour perpendicular to the surface. Large Class II MODs exhibited the highest cuspal deformation, followed by large OM restorations. Cuspal deformations in Class I and small Class II OM restorations were not significantly different.
  
  
  CONCLUSIONS
  When a composite restoration was cured, the surrounding tooth deformed due to polymerization shrinkage. Cavity type and size affected how much cusps moved inward as a result of polymerization shrinkage. This study quantified and visualized the pattern of cuspal deformation.
authors.affiliation: Department of Operative Dentistry, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Daranee
authors.initials: D
authors.lastname: Tantbirojn
authors.forename: Antheunis
authors.initials: A
authors.lastname: Versluis
authors.forename: Maria R
authors.initials: MR
authors.lastname: Pintado
authors.forename: Ralph
authors.initials: R
authors.lastname: DeLong
authors.forename: William H
authors.initials: WH
authors.lastname: Douglas
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D003737:Dental Cavity Preparation; D018772:Dental Marginal Adaptation; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000009:adverse effects*; D003799:Dental Stress Analysis; D006801:Humans; D008027:Light; D008963:Molar / Q000473:pathology; D015394:Molecular Structure; D044367:Phase Transition; D018583:Pliability; D012822:Silicon Dioxide / Q000737:chemistry / Q000528:radiation effects; D019228:Tooth Crown / Q000473:pathology*; D015040:Zirconium / Q000737:chemistry / Q000528:radiation effects
chemical_list: D003188:Composite Resins; C083568:Z100 composite resin; D012822:Silicon Dioxide; D015040:Zirconium