Introduction: Performing dental practices in the oral environment leads to the transmission of microorganisms in saliva and blood to working surfaces and dental devices and their infection. Preventing transmission of infection through these devices is an important task of a dentist. Hence, this research was conducted to evaluate the disinfection quality of the dental faculty units of Ahvaz Jundishapur University of Medical Sciences (AJUMS) in Iran. Materials and Methods:In order to evaluate the quality of disinfection of the units, sampling was performed from all glasses spittoon surfaces of 90 units of the clinical unit of the AJUMS dental faculty before and after disinfection by personnel. Then, the bacteria were cultured in a medium and examined. Results:The mean (and standard deviation) of the total infection of units of the dental faculty was 46534.4 (583380.4) colonies per 1 ml before disinfection and 40265.6 (52131.1) colonies per 1 ml after disinfection, reflecting significant decrease in number of bacterial colonies after disinfection (P <0.001). In addition, a significant decrease was seen in the number of bacterial colonies in the restoration, pediatric, orthodontic and diagnosis units (p <0.05), but the difference before and after disinfection was not significant in the prosthetic, endodontic, surgical and periodontal units. In addition, the most common types of microorganisms in the whole units of the dental faculty were pseudomonas aeruginosa, Staphylococcus aureus and Streptococcus, respectively, and after disinfection, the most common types of microorganisms were Pseudomonas aeruginosa, Staphylococcus aureus and Enterococcus, respectively. Conclusion:In general, this study showed that the disinfection method of units in dental faculty can not reduce the severity of infection of the units. Given what was stated, it is recommended that the method and the substances used to disinfect the unit to be changed.