title: Three-dimensional processing deformation of three denture base materials.
abstract: BACKGROUND
  Heat-polymerized polymethyl methacrylate denture bases deform during and after polymerization, and this deformation may affect the clinical performance of complete dentures.
  
  
  OBJECTIVE
  The purpose of this study was to investigate the processing deformation of 3 denture base materials on a standardized anatomic model by using a contact scanner and surface matching software.
  
  
  METHODS
  Maxillary reproductions of a definitive cast were digitized by using a contact scanner. The casts were allocated to 4 groups, depending on the denture base material: compression molded (heat polymerized, polymethyl methacrylate based); injection molded (heat polymerized, polymethyl methacrylate based); manually adapted and light-polymerized (urethane dimethacrylate based); and manually adapted, compression molded, and light-polymerized (urethane dimethacrylate-based). The intaglio surfaces of denture bases fabricated on each replicate cast also were digitized by using the contact scanner. Surface-matching software was used to measure dimensional changes between each cast and its corresponding denture base. The Kruskal-Wallis analysis of variance based on ranks was used to assess differences in contraction, expansion, and overall change among groups. The Mann-Whitney U test was performed to determine differences among individual groups. Statistical significance was inferred when P<.01 to compensate for multiple group comparisons.
  
  
  RESULTS
  Statistically significant differences in processing deformations were observed among polymethyl methacrylate-based resins and urethane dimethacrylate-based resin. No differences were observed between compression molding and injection molding or between manual adaptation alone and the combination of manual adaptation and compression molding.
  
  
  CONCLUSIONS
  Urethane dimethacrylate-based resin showed greater processing deformation compared with polymethyl methacrylate-based resins. Compression molding and injection molding techniques produced similar results for the polymethyl methacrylate-based resins. The methodology used showed patterns of deformation that were too complex to be accurately analyzed by linear measurements.
authors.affiliation: Postgraduate student, Department of Prosthodontics, King's College London Dental Institute, London, UK.
authors.forename: Andreas
authors.initials: A
authors.lastname: Artopoulos
authors.forename: Andrzej S
authors.initials: AS
authors.lastname: Juszczyk
authors.forename: Jose M
authors.initials: JM
authors.lastname: Rodriguez
authors.forename: Robert K F
authors.initials: RK
authors.lastname: Clark
authors.forename: David R
authors.initials: DR
authors.lastname: Radford
mesh_terms: D003188:Composite Resins / Q000737:chemistry; D003735:Dental Casting Technique; D003764:Dental Materials / Q000737:chemistry*; D003819:Denture Bases; D006358:Hot Temperature; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D007267:Injections; D008027:Light; D008422:Materials Testing; D008437:Maxilla / Q000033:anatomy & histology; D008689:Methacrylates / Q000737:chemistry*; D008768:Methylmethacrylates / Q000737:chemistry; D008953:Models, Anatomic; D058105:Polymerization; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D011140:Polyurethanes / Q000737:chemistry*; D011312:Pressure; D012984:Software; D013499:Surface Properties
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C509237:Eclipse Prosthodontic Resin; D008689:Methacrylates; D008768:Methylmethacrylates; D011140:Polyurethanes; C029824:urethane dimethacrylate luting resin; C029883:Trevalon universal; D019904:Polymethyl Methacrylate