Quantitative study of bacterial colonization of dental casts

Contamination of dental casts can occur if the record bases are improperly disinfected or inadvertently not disinfected during fabrication of a prosthesis. It is essential to develop an effective means of disinfecting dental casts from professional, medical, and legal points of view.

This study determined whether: (1) saliva contamination on the surface of the dental cast contributed to bacterial growth over time and (2) cleaning or disinfecting of dental casts can minimize bacterial growth.

Five dental casts were contaminated with saliva. Each cast was divided into six areas and swabbed at 15, 30, 60, 120, 180, and 240 minutes. Sheep blood agar plates were inoculated and incubated at 37 degrees C for 72 hours. Standardized dental stone cylinders were contaminated with 25 microliters of saliva and treated by rinsing in tap water, scrubbing with soap and tap water, soaking in 2% glutaraldehyde, or as controls with and without saliva contamination (n = 12). The treated dental stone cylinders were placed in individual test tubes containing 2.5 ml of sterile phosphate-buffered solution and a final dilution of 10(-4) was achieved. Sheep blood agar plates were inoculated and incubated at 37 degrees C for 24 hours.

Contamination of dental casts did not decrease, even when allowed to sit 4 hours before handling. Results also demonstrated that rinsing saliva-treated stone cylinders for 20 seconds significantly diminished bacterial contamination. Scrubbing with soap and tap water or soaking in 2% glutaraldehyde significantly reduced the bacterial contamination of saliva-treated stone cylinders when compared with rinsing with tap water.

Bacterial contamination of dental casts can occur and requires an effective method of disinfecting.