Dental Tray Adhesives and Their Role as Transmission Medium

Objectives: Objectives: Apart from mechanical methods, the adhesive retention of impression materials in dental impression trays is often applied for the purpose of impression taking in dental practices. The most often used application form of adhesive fluid in the dental practice consists of the use of a reusable brush stored in a small flask. If the trays are not properly disinfected, there is a potential risk for the transmission of oral bacteria and fungi into the flask and subsequently to other patients.
Methods: This study consisted of a qualitative control regarding the ability of tray adhesives to serve as a transmission medium for orally present bacteria and fungi. For this purpose, 10 flasks with tray adhesive were monitored for 12 weeks regarding any signs of contamination. Adhesive fluid samples were taken and applied on seven different culture mediums. After the incubation time all grown colonies were identified using MALDI-TOF. Isolates for which no reliable identification was obtained were further identified by sequencing the 16S rRNA genes.
Results: After 2 and after 12 weeks, no colonies could be found on any medium. After 4 weeks, there were colonies that could be detected on 6 blood agar plates. They were identified as Staphylococcus warnerii, Staphylococcus epidermis, Staphylococcus pasteuri, Ralstonia insidiosa, and Alloiococcus otitidis. However, these were false-positive findings due a contamination of the Blood agar medium. After 8 weeks, one colony (Streptococcus oralis) could be detected on a single blood agar plate.
Conclusions: Out of 50 samples there was only 1 sample with detectable oral bacteria. The disinfectant component of the tested tray adhesive (Isopropanol) appears to be effective. Thus, the risk of transmission of oral bacteria by reused brushes in tray adhesives must be considered as low.