Effectiveness of Alcohol and Aldehyde Spray Disinfectants on Dental Impressions

Background: The gold standard for disinfection of dental impressions is by immersion although spray techniques are also available. This study compared the effectiveness of alcohol and aldehyde spray disinfectants on analogue dental impressions in a hospital setting. Materials and Methods: Impressions were swabbed after removal from the mouth (pre-disinfection) and after spraying (post-disinfection) with either a non-aldehyde alcohol-based disinfectant, Bossklein (Silsden, W Yorks, BD20 0EF, UK) or a glutaraldehyde-based alcohol-free disinfectant, MD520 (Durr Dental, 74321 Bietigheim-Bissingen, Germany). Swabs were transported to the microbiology laboratory in Amies medium and plated onto sheep blood agar within 2 hrs. Plates were incubated for 3 days at 37 degrees C then at room temperature for 3 days. After incubation, all plates were examined for microbial growth. Results: A total of 87 impressions were assessed (alginate = 41; poly-vinyl siloxane (PVS) = 31; polyether = 15). The counts were categorized into two groups: no growth or growth present. Post-disinfection contamination was present on six alginate and six PVS - impressions but only one polyether impression (x(2) = 1.27, P > 0.05, NSS). Analysis of post-disinfection growth according to impression and disinfectant found significantly more contaminated PVS impressions with the alcohol-based spray than with the aldehyde spray (x(2) = 5.37, p < 0.05). Disinfection with the aldehyde-based spray resulted in only two contaminated impressions, both in alginate. Conclusion: Alcohol-based spray disinfection of dental impressions may be less effective than aldehyde spray and full immersion of impressions is recommended. Careful wetting or soaking of all surfaces of impressions is very important when using a spray.