The occurrence of porosity in reline acrylic resins. Effect of microwave disinfection.
BACKGROUND
Microwave energy has proved to be an effective method for disinfecting acrylic dentures. However, the effect of microwave heating on the porosity of autopolymerising denture reline resins has not been investigated.


OBJECTIVE
The purpose of the study was to determine the effect of microwave disinfection on the porosity of autopolymerised denture reline materials (Kooliner-K, New Truliner-NT, Tokuso Rebase Fast-TR and Ufi Gel Hard-UGH) and a conventional heat-polymerised denture base resin (Lucitone 550-L).


METHODS
Specimens (10 mm x 20 mm x 1 mm) were obtained from the impression surface of the palatal mucosa in a single person and divided into four groups (n = 5). The porosity was evaluated after polymerisation (C1), after two cycles of microwave disinfection (MW2), after seven cycles of microwave disinfection (MW7) and after 7 days storage in water at 37 degrees C (C2). Specimens from group MW7 were exposed to microwave disinfection daily being stored in water at 37 degrees C between exposures. All the replicas were sputter coated with gold and micrographs/digital images were taken of each replica using scanning electron microscopy at magnification x 100. The SEM micrographs were then examined using an image analyser to determine the number of pores. Comparison between materials and groups were made using Kruskal-Wallis tests.


RESULTS
MW7 resulted in a significant increase in the number from the pores of material K, but decreased in number in reline material TR and UGH reline resin. The number of pores in materials NT and L remained unaffected following microwave disinfection.


CONCLUSIONS
Differences in the porosity amongst the materials and for different experimental conditions were observed following microwave disinfection.
Novais
Polyanna Maria Rocha
PM
Department of Dentistry, University of Fortaleza, Ceara, Brazil.
Giampaolo
Eunice Teresinha
ET
Vergani
Carlos Eduardo
CE
Machado
Ana Lúcia
AL
Pavarina
Ana Cláudia
AC
Jorge
Janaina Habib
JH
D000180:Acrylic Resins / Q000737:chemistry* / Q000528:radiation effects; D003764:Dental Materials / Q000737:chemistry* / Q000528:radiation effects; D003819:Denture Bases; D003823:Denture Rebasing; D004203:Disinfection / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry / Q000528:radiation effects; D008855:Microscopy, Electron, Scanning; D008872:Microwaves / Q000627:therapeutic use*; D016062:Porosity; D012826:Silicone Elastomers / Q000737:chemistry / Q000528:radiation effects; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
D000180:Acrylic Resins; D003764:Dental Materials; D008689:Methacrylates; D012826:Silicone Elastomers; C503430:Tokuso Rebase Fast; C483158:Ufi gel; D014867:Water; C103363:kooliner; C071514:truliner; C040291:Lucitone