The use of paraformaldehyde powder for the sterile storage of gutta-percha cones

This investigation was undertaken to determine whether the use of paraformaldehyde powder for the sterile storage of gutta-percha cones is necessary, effective, and safe. Gutta-percha cones from unopened manufacturer's packages (Hygienic) were found to be sterile and to possess no inherent antimicrobial properties. Paraformaldehyde powder placed within the storage container was ineffective in sterilization of cones contaminated by bacterial endospores. Such storage did not prevent contamination of cones by air-borne agents, but storage in a covered glass container without paraformaldehyde was equally effective. Formaldehyde was found to be adsorbed onto the surface of cones exposed to formaldehyde vapors. No significant increase in the level of formaldehyde in the operatory air was detected as a result of this storage method. It is recommended that this method of “sterile storage” be discontinued and efforts be directed at the prevention of contamination of cones during transfer from storage to obturation.