Bacterial contamination of cavity varnish.

The present investigation was undertaken to determine whether cavity varnish can serve as a bacterial reservoir. Twenty-eight samples of cavity varnish were collected From bottles in use in a clinic and two From previously unopened bottles of the material. Samples were grown on a variety of media, both aerobically and anaerobically. Results indicated growth in 25 of 30 samples. The two Freshly opened bottles of varnish contained organisms indigenous to soil. The 23 contaminated samples From the clinic contained organisms including several varieties of oral and pharyngeal Flora. The results indicate that cavity varnish can serve as a bacterial reservoir. Cavity varnish is a natural rosin or synthetic resin dissolved in a solvent such as ether or chloroform. One of its principal functions is to reduce microleakage.1,2 Because of the difficulty of attaining a continuous layer of varnish and the tendency for small voids to form as the varnish dries, it has been recommended that two or three coats of varnish be applied. 2,3.4 A dental operator who follows this advice and places the same applicator into the varnish bottle repeatedly may be contaminating the varnish. In a study by Fuller and Hormati,s this problem was addressed by studying six samples of cavity varnish. They concluded that the material did not support the growth of microorganisms. In actuality, their study only showed that the six samples tested were free of bacterial contamination. The purpose of the current study was to evaluate a large number of samples (both opened and previously unopened bottles) for contamination and to see whether the material would support bacterial growth. Methods and Materials Samples of cavity varnish~ were collected aseptically with sterile pipettes from bottles used by 28 randomly a Copalite, Harry J. Bosworth Co., Chicago, Ill. selected students in the pediatric dental clinic, as well as from two unopened bottles. No attempt was made to ascertain the age of each bottle or its duration of use prior to sampling. Each 20 kH sample then was plated on brain heart infusion agar and grown at 37°C aerobically and anaerobically. (Preliminary studies with several types of media suggested that all samples which demonstrated growth on more selected media also grew on brain heart infusion agar. Therefore, in subsequent work, all samples initially were plated on this enriched media). Positive samples were observed by examining these plates for growth after 24 and 48 hours. Isolated colonies were transferred to media including blood agar, chocolate agar, Mitis-Salivarius agar, eosin methylene blue agar, and malt agar. They were then grown aerobically, anaerobically, and microaerophilically at 37°C. Biochemical tests included oxidase and coagulase tests, carbohydrate fermentation, and the Enterotube identification system for suspected coliforms. Techniques utilized for special identification followed standard protocols. 6,7