title: Effect of microwave disinfection on the hardness and adhesion of two resilient liners.
abstract: BACKGROUND
  Microwave irradiation has been suggested for denture disinfection. However, the effect of this procedure on the hardness and bond strength between resilient liners and denture base acrylic resin is not known.
  
  
  OBJECTIVE
  This study evaluated the effect of water storage time and microwave disinfection on the hardness and peel bond strength of 2 silicone resilient lining materials to a heat-polymerized acrylic resin.
  
  
  METHODS
  Acrylic resin (Lucitone 199) specimens (75 x 10 x 3 mm) were stored in water at 37 degrees C (2 or 30 days) before bonding (n = 160). The resilient lining materials (GC Reline Extra Soft and Dentusil) were bonded to the denture base and divided into the following 4 groups (n = 10): Tests performed immediately after bonding (control); specimens immersed in water (200 mL) and irradiated twice, with 650 W for 6 minutes; specimens irradiated daily for 7 total cycles of disinfection; specimens immersed in water (37 degrees C) for 7 days. Specimens were submitted to a 180-degree peel test (at a crosshead speed of 10 mm/min) and the failure values (MPa) and mode of failure were recorded. Pretreatment and posttreatment hardness measurements (Shore A) of the resilient materials were also performed. Three-way analysis of variance, followed by the Tukey HSD test, was performed (alpha = .05).
  
  
  RESULTS
  The analysis revealed that, for all conditions, the mean failure strengths of GC Reline Extra Soft (0.95-1.19 MPa) were significantly higher ( P < .001) than those of Dentusil (0.45-0.50 MPa). The adhesion of the liners was not adversely affected by water storage time of Lucitone 199 or microwave disinfection. All peel test failures were cohesive. There was a small but significant difference ( P < .001) between the pretreatment (34.33 Shore A) and posttreatment (38.69 Shore A) hardness measurements.
  
  
  CONCLUSIONS
  Microwave disinfection did not compromise the hardness of either resilient liners or their adhesion to the denture base resin Lucitone 199.
authors.affiliation: Araraquara Dental School, Sao Paulo University, Sao Paulo, Brazil. cucci@foar.unesp.br
authors.forename: Ana Lucia
authors.initials: AL
authors.lastname: Machado
authors.forename: Larry C
authors.initials: LC
authors.lastname: Breeding
authors.forename: Aaron D
authors.initials: AD
authors.lastname: Puckett
mesh_terms: D000180:Acrylic Resins / Q000528:radiation effects; D000704:Analysis of Variance; D001840:Dental Bonding; D003819:Denture Bases; D003822:Denture Liners; D004203:Disinfection / Q000379:methods*; D006244:Hardness / Q000528:radiation effects; D006801:Humans; D008872:Microwaves; D013718:Tensile Strength / Q000528:radiation effects; D014867:Water
chemical_list: D000180:Acrylic Resins; D014867:Water; C040291:Lucitone