Effectiveness of Spray Disinfectants on Three dental Impression Materials
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Background: The disinfection of dental impressions is fundamental to prevent cross-infection from the dental surgery to the laboratory. Spray rather than immersion disinfectants have recently been introduced to dental practice. This study aimed to compare the effectiveness of two spray disinfectants used at Hamdan Bin Mohammed College of Dental Medicine (HBMCDM) in Dubai, United Arab Emirates. Materials and methods: Two disinfectants were compared, a new non-aldehyde alcohol based disinfectant, Bossklein (Silsden, W Yorks, BD20 0EF, UK) and an aldehyde based disinfectant, MD520 (Dürr Dental, 74321 Bietigheim-Bissingen, Germany). Impressions taken on the prosthodontic and orthodontic clinics were swabbed immediately after rinsing under running tap water (pre-disinfection) and after spraying (post-disinfection). Maxillary or mandibular impressions taken in alginate (irreversible hydrocolloid), polyether and polyvinyl siloxane (PVS) were swabbed from the same gingivalareas before and after spraying. Manufacturer’s instructions were followed regarding the spray protocol for Bossklein which was to soak thoroughly and leave to dry naturally. To standardize the method of delivery, hand spraying only, MD520 was also used from a spray bottle as the gold standard but subsequently the Hygojet box system was not used as per manufacturer’s direction. Swabs were transported to the microbiology laboratory, MedLab, in Amies medium. All swabs were plated onto blood agar within 2 hours. Plates were incubated for 3 days at 37⁰C then at room temperature for 3 days. After incubation, the number of contaminated impressions before and after disinfection for each impression material was compared using the chi square test with the level of significance set at p<0.05. Results: A total of 87 impressions were assessed (alginate=41; PVS=31; polyether=15). The counts were categorized into 2 groups: no growth or growth present. Post-disinfection contamination was present on 6 alginate and 6 PVS impressions but only 1 polyether impression (x2=1.27, NSS). Analysis of post-disinfection growth according to impression and disinfectant found significantly more contaminated PVS impressions sprayed with Bossklein than with MD520 (x2= 5.37, p<0.05). Disinfection with MD520 resulted in only 2 contaminated impressions, both in alginate. Conclusions: Spray disinfection of dental impressions may not be as effective as immersion methods. Effective spray disinfection relies on correct operator technique such as thoroughness of soaking. A low number of trigger squeezes of spray bottles may be related to cost saving which is an issue immersion disinfectants do not have. Dental staff must be trained appropriately and understand that disinfection protocols differ.