Statement of Problem: Today, cross infection control is an integral part of dentistry and many dental health care workers no longer question its necessity. All dental equipments and instruments could be potentially considered as a source of infection.

Purpose: The aim of this study was the evaluation of aerobic contaminations of four disposable materials used in routine dental practice.

Materials and Methods: In this cross-sectional study, random sampling was performed and tryptone soy broth transfer culture medium was used. After 24 hours of incubation, samples were transferred to specific culture media. (Mckangy, Chocolate agar and Blood agar). Cultured bacteria were stained and studied using gram staining method. The study was carried out in a 17 weeks period.

Results: All suction tips were infected with Bacillus cereus bacterium. Two cases of cotton roll samples showed contamination with Bacillus cereus, 2 cases with gram positive, coagulase negative cocci, 1 case with Streptococcus viridians and one case with Enterobacter class A. One case of anesthetic cartridges was contaminated with Staphylococcus epidermidis and two cases with Streptococcus viridians. Two cases of gutta-percha samples were contaminated with Bacillus cereus.

Conclusion: Based of the findings of this study, the highest level of contamination was observed in saliva ejector tips. Contamination with Bacillus cereus was seen more frequently.