Effect of sterilization techniques prior to antimicrobial testing on physical properties of dental restorative materials.
OBJECTIVE
The aim of this study was to investigate any changes to the microstructure and surface properties of selected dental materials after sterilization carried out prior to subjecting them to antimicrobial testing. Initial microbial contamination on the material, as well as other possible sources of contamination were also assessed.


METHODS
The materials investigated included dentine replacement materials Chemfil Superior(®), Ionoseal(®), Dyract Extra(®) and SDR(®). The materials were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The test materials were sterilized using alcohol, steam, ultraviolet light (UV) and ethylene oxide and any changes to these materials were then assessed by SEM, microhardness testing and Fourier transform infrared (FT-IR) spectroscopy. Material microbial levels before treatments were assessed by plate counting technique and turbidity tests. Possible contamination through dispensers was assessed by analysing the CFU/sample.


RESULTS
Ethylene oxide affected the microstructure of the Chemfil, Ionoseal and Dyract, resulting in flattening of the SiO stretching vibrations and deposition of chlorine and calcium respectively in Chemfil and Dyract. Varied contamination was demonstrated on all materials when incubated in anaerobic conditions.


CONCLUSIONS
The different sterilization techniques affected the microstructure of the materials under investigation. Samples of materials produced in sterile conditions could also be contaminated with bacteria, either from the material itself or through the dispensing apparatus.


CONCLUSIONS
Results of antimicrobial studies cannot be extrapolated clinically as the material sterilization treatment results in changes to material chemistry and microstructure, which could in turn affect the materials' antimicrobial activity.
Department of Restorative Dentistry, Faculty of Dental Surgery, University of Malta, Malta.
Cher
C
Farrugia
Department Metallurgy and Materials Engineering, Faculty of Engineering, University of Malta, Malta.
Glenn
G
Cassar
Department of Food Studies and Environmental Health, Faculty of Health Sciences, University of Malta, Malta.
Vasilis
V
Valdramidis
Department of Restorative Dentistry, Faculty of Dental Surgery, University of Malta, Malta. Electronic address: josette.camilleri@um.edu.mt.
Josette
J
Camilleri
D000890:Anti-Infective Agents / Q000494:pharmacology*; D003764:Dental Materials / Q000737:chemistry*; D003793:Dental Restoration, Permanent / Q000379:methods; D006245:Hardness Tests / Q000379:methods; D012117:Resins, Synthetic / Q000737:chemistry; D013242:Sterilization / Q000379:methods*; D013499:Surface Properties
D000890:Anti-Infective Agents; D003764:Dental Materials; D012117:Resins, Synthetic
Antimicrobial testing; Composite resins; Glass ionomer cements; Resin modified glass ionomers; Sterilization