Effect of Simulated Microwave Disinfection on the Mechanical Properties of Three Different Types of Denture Base Resins

Abstract

Microwave irradiation at 650 W for 5 min did not affect the mechanical properties of the three denture base resins. Domestic microwave oven, at the prescribed setting, can be used as an alternative method of disinfection for complete dentures without affecting their properties.

Effect of disinfection techniques on physical-mechanical properties of a microwave-activated acrylic resin

“…In this study, the flexural strength and flexural modulus did not differ significantly in the microwave-disinfected specimens, compared with the control specimens. Previous studies (650 W/3 minutes, 650 W/1 minute, and 650 W/5 minutes) corroborate the flexural strength results [19,22,23] . With a protocol of 720 W/5 minutes, another study showed a decrease in the flexural modulus [20] .…”

“…In the present study, the Knoop hardness significantly increased after microwave polymerization, as did the Izod impact strength and glass transition temperature. Others suggested that the protocol (720 W/5 minutes) reduced [20] or did not affect (650 W/3 and 5 minutes) the impact strength [19,23] . A protocol of 650 W/3 minutes decreased the glass transition temperature of acrylic resin [21] .…”

“…Despite its effectiveness in disinfection, these protocols have reached contradictory findings, including deleterious effects on some physical and mechanical properties due to the material heating during the irradiation, which could affect the polymer structure [19][20][21] . Previous studies suggested that the time the acrylic resins are subjected to heat during disinfection could be reduced in order to produce adequate disinfection without any adverse effects [7,23,24] . Microwave exposure time of 1 minute has been found to be effective for disinfection against Candida albicans [17,18] .…”

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

“…Based on these results, it is possible to presume smaller rigidity of the resins with the increase of the microwave cycles, which seems to confirm the decrease of the Knoop hardness after repeated microwave disinfections [17], after thermal cycling and disinfection procedures [28], and under effect of different polymerization cycles and water storage [29]. Conversely, the Vickers hardness of autopolymerized resins was not detrimentally affected by microwave disinfection with times from 1 to 5 min performed twice [30], and hardness of three denture base resins were not altered after simulated microwave disinfections at 650 W for 5 min [31], probable due to the shorter time of disinfection used in these aforementioned studies.…”

Effect of food-simulating liquids on mechanical properties and surface of a dental resin

“…24,25 But the residual monomer acted as a plasticizer in the polymer structure, 22,26 consequently leaching the residual monomer from the specimens and contributing to the increase in the flexion strength after the water storage. 16,27 The water absorption of resin allows a release of unreacted components, principally monomers. 25,28 The amount of the plasticizer that leached from the resin increased with the increasing immersion time, improving the strength of this material.…”