DISINFECTION OF DENTAL STONE CASTS - ANTIMICROBIAL EFFECTS AND PHYSICAL PROPERTY ALTERATIONS

Objectives. The purpose of this study was to evaluate the effectivenes s of disinfecting solutions incorporated into dental stone casts again st a standard and representative group of microorganisms and to note c hanges in the physical properties of the casts. Methods. Irreversible hydrocolloid impressions were con-laminated individually with Escheric hia coli, Staphylococcus aureus, Enterobacter cloacae, Pseudomonas aer uginosa, Klebsiella pneumoniae, Actinobacter calcoaceticus, Bacillus s ubtilis, Mycobacterium phlei and Candida albicans. Four readily availa ble disinfecting solutions (glutaraldehyde, povidone-iodine, chlorhexi dine and sodium hypochlorite) were added to the die stone mix used to pour up the impressions. The set cast surfaces were swabbed at 1 h and 24 h, the samples plated on agar and incubated at 37 degrees C for 24 h and 3 d for M. phlei Subsequently, colony forming units were counte d. The physical properties assessed were setting time, setting expansi on, compressive strength, detail reproduction and delayed expansion of the stone. Results. Only glutaraldehyde and povidone-iodine killed al l contaminating microorganisms within 1 h, while the 1:5 dilution of s odium hypochlorite solution was equally effective after 24 h. Two perc ent glutaraldehyde was the most effective disinfectant with the least adverse effects on the physical properties of the set cast. Although p ovidone-iodine caused a decrease in the compressive strength of the se t cast, ii can be considered to be a sound alternative. Significance. This study supports the concept of incorporating disinfectants into mo del stone as a standard operating procedure for impressions of unknown history and, most sensibly, all dental impressions.