title: Effect of thermocycling on the flexural and impact strength of urethane-based and high-impact denture base resins.
abstract: OBJECTIVE
  Mechanical properties of the acrylic resins used for denture fabrication may be influenced by water and temperature. Thus, the aim of this study was to evaluate the effect of thermocycling on the flexural and impact strength of a high-impact (Lucitone 199) and a urethane-based denture material (Eclipse).
  
  
  METHODS
  Flexural strength (64 × 10 × 3.3 mm) and impact strength (60 × 6 × 4 mm) specimens were made following the manufacturers' instructions and assigned to two groups (n = 10): control (C) - not thermocycled - and T - thermocycled (5000 cycles between 5 and 55°C). Specimens were submitted to three-point bending and Charpy impact tests.
  
  
  RESULTS
  Flexural strength (MPa) and impact strength (kJ/m(2)) data were analysed with two-way anova (p = 0.05). The flexural strength of material Eclipse (C, 136.5; T, 130.7) was significantly higher than that of resin Lucitone 550 (C, 99.4; T, 90.1). Material Eclipse exhibited significantly higher impact strength (C, 6.9; T, 5.3) than the resin Lucitone 550 (C, 3.5; T, 3.0). For both materials, a significant decrease in flexural and impact strengths was observed when the specimens were thermocycled.
  
  
  CONCLUSIONS
  Flexural and impact strengths were higher for Eclipse than for Lucitone 550, in both groups. Thermocycling decreased the flexural and impact strengths of Eclipse and Lucitone 550.
authors: Department of Dental Materials and Prosthodontics, Araraquara Dental School, Unesp-University Estadual Paulista, Araraquara, São Paulo, Brazil. cucci@foar.unesp.br
authors: Ana Lucia
authors: AL
authors: Machado
authors: Aaron D
authors: AD
authors: Puckett
authors: Larry C
authors: LC
authors: Breeding
authors: Amanda Fucci
authors: AF
authors: Wady
authors: Carlos Eduardo
authors: CE
authors: Vergani
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D003819:Denture Bases; D006244:Hardness; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D018583:Pliability; D011140:Polyurethanes / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D000180:Acrylic Resins; D003188:Composite Resins; D003764:Dental Materials; C509237:Eclipse Prosthodontic Resin; D008689:Methacrylates; D011140:Polyurethanes; D014867:Water; C040291:Lucitone