Abstract
Aims: To evaluate the effect of microwave disinfection on transverse strength and hardness of acrylic resin denture base materials. Materials and methods: The samples were 112 samples (56 heat cured acrylic resin and 56 microwave cured acrylic resin) they were prepared in dimensions of 65± 0.3x10±0.03x2.5 ±0.03 mm (length, width and thickness respectively) for transverse strength test and 30x15x3±0.03 mm (length, width and thickness respectively) for indentation hardness test. The samples were divided into seven disinfection groups; each one contain five samples which were (control, 900 W or 540W for 3min either inside glass flask containing 150 ml of distilled water)or along with glass flask containing 150 ml of distilled water or alone. The collected data were analyzed using analy-sis of variance (one way ANOVA) at P ≤ 0.05 and Duncan's multiple range test. Results: the transverse strength of microwave acrylic resin samples were significantly decreased except samples that disinfect-ed by 540 watt microwave energy for 3 minute with water inside microwave oven. The hardness number for heat cured acrylic denture base showed no significant differences compared to control group while hardness number of microwave acrylic resin were significantly decreased in relation to control group. Conclusions: Transverse strength of microwave acrylic resin that disinfected with microwave was decreased except at 540 watt for 3 minutes with water a side in microwave oven. While heat cured acrylic resin after microwave disinfection was significantly increased compared with the control sample. Rockwell hardness number for microwave acrylic resin significantly decrease in relation to control group; while for heat cured acrylic denture base showed no significancy comparing with the control group.
Highlights
Adequate maintenance of removable prostheses is needed for denture wearers to have an esthetic, odor free appliance and good oral health.[1]
The Effect of Microwave on the Transverse Strength: The mean, standard deviation of Effect of Microwave Disinfection on Acrylic Resin Denture Base Materials transverse strength N/mm2 of the control and disinfected samples with different settings were shown in Table [1]
The polymerized microwave acrylic resin had lower residual monomer content compared to heat cured acrylic resin in which 2.25 gm of powder for each ml of liquid was used, and the specially designed acrylic for microwave curing exhibited significantly lower residual MMA leach compared with heat cured acrylic resin.[16]. So, heating of the cured resin by microwave lead to partial de polymerization that result in extension of the distance between the polymer chain.[17]. Samples that disinfected by 540 watt microwave energy for 3 minutes with water inside microwave oven, it was likely that the presence of water in side the microwave oven prevent heat concentration on the sample [10] so the transverse strength of these samples has not been affected by microwave disinfection
Summary
Adequate maintenance of removable prostheses is needed for denture wearers to have an esthetic, odor free appliance and good oral health.[1]. 900 Watt is an effective method for disinfection against Staphylococus aureus and Pseduomonase aeruginosa.[3]. Microwave irradiation at 690 Watt for 6 minutes was used to disinfect denture resin bases.[4]. Two cycles of microwave sterilization (650W for 6 minutes) decreased the Vickers hardness number (VHN) of several types of acrylic resin denture teeth when www.rafidaindentj.net. Microwaving of acrylic resin specimens in domestic adjustable-wattage microwave oven result in significant increase in flexural strength means compared to the control.[6,7]. The aims of this study were to evaluate the effect of microwave disinfection on transverse strength and hardness of heat (water bath) and microwave cured acrylic resin denture base materials
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