Flexural strength and hardness of reline and denture base acrylic resins after different exposure times of microwave disinfection.
OBJECTIVE
To evaluate the effect of microwave disinfection on the flexural strength and Vickers hardness of 4 autopolymerized resins (Kooliner [K], Tokuso Rebase Fast [T], Ufi Gel Hard [U], and New Truliner [N]) and 1 denture base resin (Lucitone 550 [L]).


METHODS
For each material, 48 specimens (64 x 10 x 3.3 mm) were made and divided into 6 equal groups (n = 8). In the control group, specimens were untreated. Before testing, specimens were immersed in 200 mL of distilled water and submitted to disinfection for 1 of the following irradiation times: 1, 2, 3, 4, or 5 minutes. The irradiation procedure was performed twice. The flexural strength was determined using a testing machine MTS-810 and measurements of Vickers hardness were made on Micromet 2100. The values were submitted to ANOVA and Tukey's test (P = .05).


RESULTS
The K material showed a significant increase (P = .0010) in flexural strength following 5 minutes of disinfection compared to control specimens. The flexural strength mean values of materials T, U, and N were not significantly affected (P > .05) by disinfection. Compared to the control group, the K material showed a significant increase in hardness (P < .001) following disinfection for 3, 4, and 5 minutes. For material U, disinfection for 4 and 5 minutes produced specimens with significantly increased hardness values (P < .001) compared to the control group. For material N, disinfection for 5 minutes resulted in significantly higher hardness values (P < .001) than the control group.


CONCLUSIONS
Regardless of the irradiation time, the flexural strength and hardness of the materials evaluated were not detrimentally affected by microwave disinfection.
Ribeiro
Daniela Garcia
DG
Department of Dental Materials and Prosthodontics, São Paulo State University, UNESP, Araraquara Dental School, São Paulo, Brazil.
Pavarina
Ana Cláudia
AC
Machado
Ana Lucia
AL
Giampaolo
Eunice Teresinha
ET
Vergani
Carlos Eduardo
CE
D000180:Acrylic Resins / Q000528:radiation effects; D003799:Dental Stress Analysis; D003819:Denture Bases; D003822:Denture Liners; D004203:Disinfection / Q000379:methods*; D006244:Hardness; D019552:Infection Control, Dental / Q000379:methods*; D008422:Materials Testing; D008872:Microwaves; D018583:Pliability; D011897:Random Allocation; D013997:Time Factors
D000180:Acrylic Resins