Effect of disinfection by microwave irradiation on the strength of intact and relined denture bases and the water sorption and solubility of denture base and reline materials

Abstract

This study evaluated the influence of microwave disinfection on the strength of intact and relined denture bases. Water sorption and solubility were also evaluated. A heat-polymerized acrylic resin (Lucitone 550) was used to construct 4-mm-thick (n 5 40) and 2-mm-thick (n 5 160) denture bases. Denture bases (2-mm) were relined with an autopolymerizing resin (Tokuso Rebase Fast, Ufi Gel Hard, Kooliner, or New Truliner). Specimens were divided into four groups (n 5 10): without treatment, one or seven cycles of microwave disinfection (650 W for 6 min), and water storage at 378C for 7 days. Specimens were vertically loaded (5 mm/min) until failure. Disc-shaped specimens (50 mm 3 0.5 mm) were fabricated (n 5 10) to evaluate water sorption and solubility. Data on maximum fracture load (N), deflection at fracture (mm), fracture energy (N mm), water sorption (%), and solubility (%) were analyzed by two-way analysis of variance and Student-Newman-Keuls tests (a 5 0.05). One cycle of microwave disinfection decreased the deflection at fracture and fracture energy of Tokuso Rebase Fast and New Truliner specimens. The strength of denture bases microwaved daily for 7 days was similar to the strength of those immersed in water for 7 days. Microwave disinfection increased the water sorption of all materials and affected the solubility of the reline materials.

Comparison of denture microwave disinfection and conventional antifungal therapy in the treatment of denture stomatitis: a randomized clinical study

“…8,10,14,17 Despite the fact that the methods of disinfection through microwaves used in earlier studies 8,10,14,27 are considered to be effective for the sterilization of complete dentures and the treatment of denture stomatitis, it has been demonstrated that the heat generated during microwave irradiation can increase the contraction of the acrylic resins 28,29 and accelerate the water sorption and solubility processes of these materials. 30 There have also been reports of undesirable effects on mechanical properties in denture base resins after microwave disinfection for 6 minutes. [31][32][33][34] Therefore, in vitro and in vivo studies were conducted to evaluate both antimicrobial efficacy and effects on acrylic resins of microwave disinfection with the use of reduced irradiation times.…”

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

“…With a protocol of 720 W/5 minutes, another study showed a decrease in the flexural modulus [20] . The water sorption and solubility of complete denture bases in a previous study (650 W/6 minutes) showed no significant changes [13] . In the present study, both properties significantly decreased after microwave disinfection.…”

“…During microwave irradiation, the amount of unreacted monomer reduces due to further polymerization [10,18] , and the residual monomer released into water increases [21,22] . The heating generated could increase the water sorption, inducing a plasticizing effect that may affect the material [13] , besides the plasticizing effect of residual monomers [14] . All of these mechanisms must be considered as factors that can change the physical-mechanical properties of the acrylic resins [21] .…”

“…In addition, complete dentures contaminated by Candida albicans are a potential source of infection and re-infection of the oral soft tissues, and its disinfection has been recommended as an adjuvant in the treatment of stomatitis and as an essential procedure for maintaining a healthy oral mucosa [7,8] . Many protocols for denture disinfection have been proposed, including immersion in chemical solutions such as glutaraldehyde [9] , sodium perborate [10] , sodium hypochlorite [11,12] , chlorhexidine digluconate [7] , peracetic acid [11,12] , and microwave irradiation [7,13] . Ideally, the choice of the disinfectant method should be made with regard to its effectiveness in inactivating microorganisms without detrimental effects on the acrylic resins.…”

Microwave assisted disinfection method in dentistry

“…In a more clinically relevant approach, the effect of denture microwave disinfection on the maximum fracture load, deflection at fracture, and fracture energy of intact and relined denture bases was evaluated. After exposed to microwave irradiation for 7 days (6 minutes/650W), the strength of the denture bases was similar to the strength of those immersed in water for 7 days (Seó et al, 2008). An aspect that has also been investigated is the influence of microwave disinfection on bond strength between resilient liners and denture base acrylic resin.…”