Antimicrobial activity of type III dental gypsum incorporated with 3-iodo-2-propynyl-butylcarbamate and its physical properties

Dental impressions have been considered to be potential sources of microbial contamination from patients’ blood and saliva to dental personnel and prostheses fabricated on gypsum casts. Thus, the development of dental gypsum with antimicrobial activity to reduce crosscontamination between patients and laboratory personnel is needed. This study aims to evaluate the influence of incorporation of 3-iodo-2-propynyl-butylcarbamate (IPBC) into type III dental gypsum on its antimicrobial activities and physical properties such as dry compressive strength and setting time. Type III dental gypsum (The Siam Moulding Plaster Co., Ltd, Thailand) incorporated with 3 concentrations of IPBC (0.01%, 0.005% and 0.001% w/w) was tested compared with the control, gypsum without disinfectant. Microorganisms tested were Staphylococcus aureus ATCC 6538, Pseudomonas aeruginosa ATCC 27853 and Candida albicans ATCC 1023. One hundred μL of each microbial suspension (10⁸ CFU/mL) was dropped on hydrocolloid impression (Jeltrate; Caulk/Dentsply, Milford, DE) and left dry. All types of gypsum mixes were prepared and poured into the impressions and allowed to set for 60 min. Then the gypsum samples were removed and the microbial contact surfaces were imprinted on Brain Heart Infusion agar plates. After incubation, colonies appeared on agar were gram-stained and counted. The dry compressive strength and setting time were tested in accordance with International Standard (ISO) 6873: 1998 (E). Dental gypsum containing IPBC showed antimicrobial activity against all tested microorganisms with the percentage of microbial reduction ranging from 19.4% to 70.6%. Among all types of dental gypsum, no significant differences in dry compressive strength and setting time were observed. The newly developed type III dental gypsum incorporated with IPBC had antimicrobial effects against all tested microorganisms. The physical properties of the modified dental gypsum were within the ISO standards. However, further investigation on other properties such as dimensional stability, detail reproduction and clinical usage are still needed.