title: Failure strengths of denture teeth fabricated on injection molded or compression molded denture base resins.
abstract: BACKGROUND
  Denture tooth fracture or debonding remains a common problem in removable prosthodontics.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to explore factors determining failure strengths for combinations of different denture tooth designs (shape, materials) and injection or compression molded denture base resins.
  
  
  METHODS
  Three central incisor denture tooth designs were tested: nanohybrid composite (NHC; Ivoclar Phonares II), interpenetrating network (IPN; Dentsply Portrait), and microfiller reinforced polyacrylic (MRP; VITA Physiodens). Denture teeth of each type were processed on an injection molded resin (IvoBase HI; Ivoclar Vivadent AG) or a compression molded resin (Lucitone 199; Dentsply Intl) (n=11 or 12). The denture teeth were loaded at 45 degrees on the incisal edge. The failure load was recorded and analyzed with 2-way ANOVA (α=.05), and the fracture mode was categorized from observed fracture surfaces as cohesive, adhesive, or mixed failure.
  
  
  RESULTS
  The following failure loads (mean ±SD) were recorded: NHC/injection molded 280 ±52 N; IPN/injection molded 331 ±41 N; MRP/injection molded 247 ±23 N; NHC/compression molded 204 ±31 N; IPN/compression molded 184 ±17 N; MRP/compression molded 201 ±16 N. Injection molded resin yielded significantly higher failure strength for all denture teeth (P<.001), among which IPN had the highest strength. Failure was predominantly cohesive in the teeth, with the exception of mixed mode for the IPN/compression group.
  
  
  CONCLUSIONS
  When good bonding was achieved, the strength of the structure (denture tooth/base resin combination) was determined by the strength of the denture teeth, which may be affected by the processing technique.
authors.affiliation: Resident, Advanced Prosthodontics Program, University of Tennessee Health Science Center, Memphis, Tenn.
authors.forename: Nathan E
authors.initials: NE
authors.lastname: Robison
authors.affiliation: Associate Professor, Department of Restorative Dentistry, University of Tennessee Health Science Center, Memphis, Tenn.
authors.forename: Daranee
authors.initials: D
authors.lastname: Tantbirojn
authors.affiliation: Professor and Director of Biomaterials Research, Department of Bioscience Research, University of Tennessee Health Science Center, Memphis, Tenn. Electronic address: antheun@uthsc.edu.
authors.forename: Antheunis
authors.initials: A
authors.lastname: Versluis
authors.affiliation: Professor and Director of Graduate Prosthodontics, Department of Prosthodontics, University of Tennessee Health Science Center, Memphis, Tenn.
authors.forename: David R
authors.initials: DR
authors.lastname: Cagna
mesh_terms: D000180:Acrylic Resins; D003188:Composite Resins; D019245:Compressive Strength; D003799:Dental Stress Analysis; D003819:Denture Bases; D003779:Denture Design; D006801:Humans; D008422:Materials Testing; D011140:Polyurethanes
chemical_list: D000180:Acrylic Resins; D003188:Composite Resins; D011140:Polyurethanes; C513703:Vivadent; C040291:Lucitone