Contamination of Composite Resins in Dental Clinics of a Teaching Institution

Objective: To evaluate by microbiological analysis, the contamination of composite resins in three dental clinics of a teaching institution in the city of Santa Maria, RS, Brazil and to assess the correlation between contamination and usage frequency of the resins. Method: First, a survey was performed to determine how many students practiced in each clinic and the teaching semester they were attending. One hundred samples were available for the study in the different clinics and all of them were analyzed. Two-millimeter increments were aseptically collected from each composite resin syringe in the outpatient setting. The samples were immediately to the laboratory and immersed in test tubes containing 5 mL of BHI (Brain Heart Infusion) culture medium. After 24-hour incubation period in a bacteriological incubator at 37oC the first reading of the culture medium turbidity was made by an experienced examiner, and the last reading was made after 48 h. A negative control group was established. The samples in which turbidity of the culture medium occurred were considered as contaminated. Results: 51% of the analyzed composite resin samples were contaminated, with percentage varying among the clinics. A strong correlation was found between the number of students practicing in the clinic and the percentage of contamination. Conclusion: At some point in the restorative procedure performed by the students occurs a failure that results in contamination. Therefore, there is a risk of cross-infection, which requires an alternative way to avoid this contamination in the procedures.