Ultrastructural pulmonary changes in mice exposed to aerosolized Periodontal Pack Powder

An electron microscopic study was undertaken to investigate pulmonary ultrastructural changes in mice following exposure to an aerosolized Periodontal Pack Powder (PPP), and to determine if the asbestos fiber, which contains 7% PPP, is respirable. One hundred and sixty-five animals were used in this study. Seventy-two of the animals were exposed to the powder twice weekly for a minimum of two weeks and a maximum of four weeks. Fifty animals were exposed to the PPP (without asbestos), with the same exposure sequence used. Forty-three animals served as nonexposed controls. Randomly selected groups of exposed and control mice were killed at designated intervals between two and 12 weeks. Microscopic examination of the lungs revealed early interstitial pneumonia. These changes were seen in both treatment groups. Late changes included a generalized resolution of the pneumonia (seen in both treatment groups) with residual diffuse interstitial fibrosis, persistence of asbestos fibers within the tissue, and early asbestos body formation (seen only in animals exposed to asbestos-containing PPP). This study documents that the asbestos in Periodontal Pack Powder is both respirable and potentially pathogenic. Dentists who have used this product could conceivably be a population at risk for pulmonary fibrosis and/or obstructive airways disease.