A rabbit lung model for testing reaction to inhaled dental restorative particles

A study was designed to test the outcome of the deposition of particles of plastic composite dental restorative material in rabbit lungs. Grinding and polishing these restorations in situ produces some particles in the 0.5- to 10-microns size range that easily enter and remain in human lungs and are associated with industrial lung disease. Dental restorative plastic material was ground in the laboratory, suspended in saline solution, and injected transtracheally into four New Zealand white rabbits. Two control rabbits were similarly injected with saline solution transtracheally. Twenty-four hours later, the rabbits were injected with 1 mCi of 67Ga citrate intravenously and subsequently reanesthetized for scanning. Baseline scans were obtained in the six animals prior to the injection of the test particles. Positive gallium scans were obtained 72 h after the administration of particulate material in the four test rabbits. The gallium scans of the control rabbits remained no different from baseline. The study was repeated one month later. The animals were killed seven days after the last gallium scan. Light microscopy and transmission electron microscopy of the lungs of the test animals showed foci of chronic inflammation around particles of the restorative material. Particles were in vacuoles within alveolar macrophages and also free in interstitium. Control animals had normal histologic conditions. Silver amalgam and gold dental restorations have years of clinical use but the new plastic composite restorative materials are rapidly being introduced into human clinical dental practice. Normal use involves polymerization, grinding, and polishing of the material within the mouth. The chronic inflammation in the lungs of rabbits indicates a need to test dental restorative material for lung biocompatibility before further, extensive clinical use.