title: Effect of microwave disinfection on the surface roughness of three denture base resins after tooth brushing.
abstract: OBJECTIVE
  This study investigated the effect of microwave disinfection on the roughness of three heat-polymerised acrylic resins after tooth brushing.
  
  
  BACKGROUND
  Microwave disinfection has been recommended to reduce cross-contamination. However, this procedure may also influence the physical and mechanical properties of acrylic resins.
  
  
  METHODS
  Specimens (40 × 20 × 2 mm) of resins: Lucitone 550 (L), QC 20(QC) and Acron MC (A) were prepared and divided into four groups (n = 10): Control groups 1 (C1) and 2 (C2) - stored in water for 48 h or 7 days; Test groups 1 (MW2) and 2 (MW7) - stored in water for 48 h and disinfected (650 W for 6 min) daily for 2 or 7 days, respectively. After treatments, the specimens were placed in a tooth brushing machine at a rate of 60 reciprocal strokes per minute. The specimens were brushed with 20 000 strokes, which represent approximately 2 years of denture cleansing. The surface roughness (Ra) was evaluated before and after the tooth brushing. Data were analysed by two-way anova and Tukey Honestly Significant Difference (HSD) post hoc tests (α = 0.05).
  
  
  RESULTS
  The data revealed significant changes between test groups for A and L resins. Comparison among resins revealed that for MW7, the roughness of A was significantly lower than that of L. After the seven microwave cycles, it could be seen that the roughness values of QC were significantly lower than those of L.
  
  
  CONCLUSIONS
  The roughness of QC after brushing was not significantly affected by microwave disinfection. For A and L, seven microwave cycles resulted in increased roughness.
authors.affiliation: Department of Dental Materials and Prosthodontics, Univ Estadual Paulista,Araraquara, Dental School, UNESP, Araraquara - SP, Brazil.
authors.forename: Fernanda Emiko
authors.initials: FE
authors.lastname: Izumida
authors.forename: Roberta Chuqui
authors.initials: RC
authors.lastname: Ribeiro
authors.forename: Eunice Teresinha
authors.initials: ET
authors.lastname: Giampaolo
authors.forename: Ana Lucia
authors.initials: AL
authors.lastname: Machado
authors.forename: Ana Cláudia
authors.initials: AC
authors.lastname: Pavarina
authors.forename: Carlos Eduardo
authors.initials: CE
authors.lastname: Vergani
mesh_terms: D000180:Acrylic Resins; D000704:Analysis of Variance; D003819:Denture Bases; D004203:Disinfection / Q000379:methods*; D008422:Materials Testing; D008872:Microwaves; D013499:Surface Properties; D014099:Toothbrushing
chemical_list: D000180:Acrylic Resins; C488492:QC 20 (denture base resin); C075051:Acron MC; C040291:Lucitone