Effect of sterilization techniques prior to antimicrobial testing on physical properties of dental restorative materials

Abstract

Objectives: 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 sub- jecting 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

Superior1, Ionoseal1, Dyract Extra1 and SDR1. 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 Si–O 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 mate- rials 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.

Clinical significance: Results of antimicrobial studies cannot be extrapolated clinically as the

material sterilization treatment results in changes to material chemistry and microstruc- ture, which could in turn affect the materials’ antimicrobial activity.