Effect of Repeated Simulated Disinfections by Microwave Energy on the Complete Denture Base Adaptation

Rafael L.X Consani,Simonides Consani,Rose Y Iwasaki,Wilson B Mendes,Marcelo F Mesquita

doi:10.2174/1874210600802010061

Abstract

This study evaluated the effect of repeated microwave disinfections on the adaptation of the maxillar denture base using 2 different flask closure methods. Twenty stone cast-wax base sets were prepared for flasking by traditional cramp or RS system methods. Five bases for each method were submitted to 5 repeated simulated disinfections in a microwave oven with 650W for 3 minutes. Control bases were not disinfected. Three transverse cuts were made through each stone cast-resin base set, corresponding to canine, first molar, and posterior region. Measurements were made using an optical micrometer at 5 points for each cut to determine base adaptation: left and right marginal limits of the flanges, left and right ridge crests, and midline. Results for base adaptation performed by the flask closure methods were: traditional cramp (non-disinfected = 0.21 ± 0.05mm and disinfected = 0.22 ± 0.05mm), and RS system (non-disinfected = 0.16 ± 0.05 and disinfected = 0.17 ± 0.04mm). Collected data were submitted to ANOVA and Tukey test (α=.05). Repeated simulated disinfections by microwave energy did not cause deleterious effect on the base adaptation, when the traditional cramp and RS system flask closure methods were compared.

Highlights

In addition to the changes occurred due to several variables, such as linear shrinkage of the acrylic resins [1], denture processing [2,3], commercial types of acrylic resins [4], flask closure methods [5], and post-pressing times [6], treatments for denture disinfection performed by chemical [7] and microwave irradiation methods can promote linear dimensional changes [8,9,10,11].Prosthesis can be contaminated by microorganisms during manufacture or manipulation, or by the patients
The stone cast-wax base sets were codified with numbers to blind the examiner, and randomly divided into the following groups (n=5): (1) bases made for the traditional cramp flask closure method (TFC) and nondisinfected (ND); (2) bases made for the TFC method and submitted to repeated simulated disinfections by microwave (RSD); (3) bases made for the RS system flask closure method (RSFC) and ND; and (3) bases made for the Restriction System flask closure (RSFC) method submitted to RSD
Denture base fit values obtained for the RSFC method (ND = 0.16 ± 0.05mm, and RSD = 0.17 ± 0.04mm) were significantly lower (p

Summary

Introduction

Prosthesis can be contaminated by microorganisms during manufacture or manipulation, or by the patients. As an effort to eliminate or decrease cross-contamination, chemical solutions should be used for prosthesis disinfection. Materials sent from dental clinics to prosthetic laboratories were contaminated by bacteria [12], and sterile prostheses could be contaminated during polishing or by microorganisms transferred from other prostheses during laboratory practice [13,14,15]. Glutaraldehyde, sodium hypochlorite, iodoform, or chlorine dioxide had been suggested for prosthesis chemical disinfection to avoid cross-contamination, [16,17,18,19,20,21]; this method shows disadvantages such as prosthesis staining and oral tissue reactions [22, 23].

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Conclusion