Effect of Microwave Disinfection Procedures on Torsional Bond Strengths of Two Hard Chairside Denture Reline Materials

The Effect of Microwave Disinfection on Denture Base Polymers, Liners and Teeth: A Basic Overview

The aim of this paper was to overview the current scientific knowledge concerning the effect of microwave disinfection on denture related material properties. Cross-infection control in dentistry is a significant issue in everyday clinical practice due to the recent increase in some infectious diseases such as hepatitis B, C and AIDS and therefore numerous methods of disinfection have been used. The most widespread method of disinfection used in everyday practice is chemical, however, studies have suggested that chemical disinfectants alter the physical and mechanical properties of the acrylic resins and enable the growth and proliferation of certain bacteria. Therefore, microwaves were introduced as an easy to use-and-access, low cost, chemical free alternative. The question that arose was if and in what way the microwave irradiation affected the denture related material properties. Microwaving affects the denture resin bases, liners and teeth in different ways. The results showed that microwave disinfection could be a safe alternative for the disinfection of denture bases and liners compared to the chemical one, when the procedure is carried out in dry conditions, but could possibly cause dimensional changes of clinical significance on them when the irradiation takes place in wet environment. It also seems to have no detrimental effects of clinical importance on the flexural properties, impact strength and hardness of denture resins and the bond, flexural strength, porosity and hardness of denture liners. The effects of microwave disinfection on the hardness of denture teeth and teeth/denture bond strength are still controversial and no safe conclusions can be drawn.

A conventional microwave oven for denture cleaning: a critical review

INTRODUCTION

Denture cleaning should be quick and easy to perform, especially in long-term care facilities. The lack of proper oral hygiene can put older adults at higher risk from opportunistic oral infections, particularly fungal. As an alternative to regular brushing, the use of a microwave oven has been suggested for cleaning and disinfecting dentures.

OBJECTIVES

To synthesise and discuss the advantages and disadvantages of the use of a conventional microwave oven for cleaning and disinfecting complete dentures.

METHODS

A brief literature search focused on papers dealing with microwave therapy for denture cleaning through PubMed Central, Cochrane Database of Systematic Reviews, Google Scholar, Ovid MEDLINE(R) In-Process, and Scifinder Scholar.

RESULTS

One hundred and sixty-seven manuscripts published in English with full text were found, and 28 were accepted and discussed in the light of the advantages and disadvantages of the use of conventional microwave oven for cleaning and disinfecting complete dentures.

CONCLUSIONS

There was no standardisation for microwave use for denture cleaning. Manual cleaning still seemed to be the optimal method for controlling fungal infection and denture stomatitis. However, such a daily routine appeared to be underused, particularly in long-term care facilities.

Efficacy of denture disinfection methods in controlling Candida albicans colonization in vitro

OBJECTIVE

The aim of this study was to rank 10 denture disinfection methods according to their efficacy in reducing Candida albicans (C. albicans) colonization on soft denture relining material.

MATERIAL AND METHODS

Circular specimens (diameter 8 mm) were made of soft denture relining material (Mucopren E, Kettenbach) and thermally aged. Specimens were incubated with C. albicans (strain 1386, DSMZ) followed by 1 of 10 disinfection procedures (6 soaks, 2 microwave irradiation regimes, 1 effervescent commercial cleansing product, and denture left dry overnight). Incubation with phosphate buffered saline (PBS) served as a control. Adhering fungi were quantified using a bioluminometric assay in combination with an automated plate reader for cell quantification. Scanning electron micrographs (SEMs) were made for validation.

RESULTS

Low median luminescence intensities indicated the presence of a few viable fungi after the soaking of specimens in sodium hypochlorite (10 relative luminescence units (rlu)), microwave irradiation immersed in water (8 rlu), and application of effervescent cleansing tabs (22 rlu). No statistically significant difference (p>0.05) to control PBS (200 rlu) was found after immersion in hydrogen peroxide (172 rlu), glutaraldehyde (103 rlu), household vinegar (196 rlu), Listerine coolmint (194 rlu), Plax (222 rlu), dry microwave irradiation (221 rlu) and specimens left dry overnight (165 rlu). SEM displayed C. albicans monolayers with different morphologic forms on each surface investigated.

CONCLUSIONS

Only soaking in sodium hypochlorite (1%; 10 min), microwave irradiation immersed in water (800 W; 6 min), and application of effervescent cleansing tabs (Blend-a-dent tabs; 10 min) proved to be effective against C. albicans colonization on soft denture relining material.