Effect of microwave disinfection on physical and mechanical properties of acrylic resins

Abstract

This study evaluated the effect of microwave energy on the hardness, impact strength and flexural strength of the Clássico, Onda-Cryl and QC-20 acrylic resins. Aluminum die were embedded in metallic or plastic flasks with type III dental stone, in accordance with the traditional packing technique. A mixing powder/liquid ratio was used according to the manufacturer's instructions. After polymerization in water batch at 74ºC for 9 h, boiling water for 20 min or microwave energy at 900 W for 10 min, the specimens were deflasked after flask cooling at room temperature, and submitted to finishing. Specimens non-disinfected and disinfected by microwave irradiation were submitted to hardness, impact and flexural strength tests. Each specimen was immersed in distilled water and disinfected in a microwave oven calibrated to 650 W for 3 min. Knoop hardness test was performed with 25 g load for 10 s, impact test was carried out using the Charpy system with 40 kpcm, and 3-point bending test with a crosshead speed of 0.5 mm/min until fracture. Data were submitted to statistical analysis by ANOVA and Tukey's test =0.05). Disinfection by microwave energy decreased the hardness of Clássico and Onda-Cryl acrylic resins, but no effect was observed on the impact and flexural strength of all tested resins.

Effect of Different Simulated Microwave Disinfection Cycles on Hardness, Roughness and Gloss of Acrylic Resins

“…This result is in agreement with the previous study that reported hardness decrease for acrylic resins after microwave irradiation, but no effect was observed on the impact and flexural strength [16]. Moreover, conventional and boiled polymerization cycles promoted similar roughness and surface hardness for QC-20 and Classico resins [24]; however, the hardness levels for both resins were lesser than those seen in the current study.…”

“…Although the microwave radiation had been efficient in the sterilization process, possible harms on the mechanical and viscoelastic properties of the acrylic resin still need to be best clarified. Previous studies have shown that the disinfection by microwave energy decreased the hardness of some acrylic resin types, but no effect was observed on the impact and flexural strength [16]. Repeated microwave disinfections decreased the Knoop hardness and showed no effect on the impact strength, while the flexural strength was similar for all evaluated acrylic resins [17]; however,though the roughness after brushing was not significantly affected by microwave disinfection, a increased microwave cycles resulted in greater roughness [18].…”

Effect of soft drink towards heat cured acrylic resin denture base surface roughness

“…17 Each specimen was put in a plastic vial contained a aquadest and soft drinks solution, with each amounted as much as 20 ml, and stored in an incubator at the temperature of 5°C (for the treatment group). 18 All specimens were immersed for 2 days to simulated the average person soft drink daily consumption habits for 20 minutes in 5 months period of time (20 minutesx150 days= 3000 minutes=50 hours=2.08 days). The immersion media was replaced daily.…”

Effect of repeated cycles of chemical disinfection in microhardness of acrylic resins of complete denture base

“…An effective alternative method that has been currently used is microwave irradiation to fight several diseases and eliminate colonization by Candida albicans 4,[8][9][10][11][12] .…”

“…Clinical characteristics such as rugosity, hardness, dimensional stability of color and bending properties can be changed after immersion in those solutions 1,11,13 .…”