Sterilization of Silicone and Titanium Using Ultraviolet Light

Sterilization is a very important parameter in infection control. It is monitored through the use of biological, chemical, and physical means. Several sterilizing methods have been described in the literature, each with its own advantages and disadvantages, however little information is evident regarding Ultraviolet Light Radiation as a mode of sterilization. The purpose of this study was to investigate the effectiveness of the Ultraviolet Light machine in sterilization of silicone rubber discs and commercially pure titanium samples infected with Bacillus subtilis. Twenty silicone discs, 7.9 mm in diameter and 2.5 mm in thickness were prepared of MDX4-4210 following manufacturers recommendations and placed in ten groups, with two silicone discs in each group. Eight of the groups were exposed to ultraviolet light radiation (UV) at different lengths of exposure time. The UY light exposure times corresponded to 4, 10, 12, 15, 20, 30, 40, and 60 seconds. The other two groups were used for controls, a positive control with zero seconds of exposure of the UV light, and the other a negative control where a standard autoclave sterilization cycle was used (121oC for 20 minutes at 15 psi). Ten commercially pure titanium samples, 10 mm X 8.2 mm X 3 mm were machined by BUD industries (Holland, NY) and infected with Bacillus subtilis. These samples were divided into five groups each containing two samples. Three groups were subjected to the ultraviolet light radiation at exposure times of 8, 16, and 90 seconds. The other two groups were used as controls, a positive control where the inoculated samples were not subjected to any UV light exposure and a negative control in which the samples were subjected to an autoclave sterilization cycle. The silicone discs and commercially pure titanium samples were washed with phosphate buffer solution, serial dilution\u27s performed, heat shocked in a hot water bath of 80°C for 20 minutes, and plated on blood agar plates in duplicate. These plates were incubated at 37°C for seven days. The colony forming units (CFu) were counted and recorded. One -way Analysis of Variance (ANOV A) was used for statistical comparisons at (p \u3c .05). The raw data quickly revealed that a significant number of Bacillus subtilis spores were killed yet it remained that at no time above zero seconds was there a 100 percent of Bacillus subtilis killed for silicone discs or the commercially pure titanium samples. The Ultraviolet Light machine did not sterilize the silicone discs or the commercially pure titanium samples