Sublethal Toxicity of 17 Per- and Polyfluoroalkyl Substances with Diverse Structures to Ceriodaphnia dubia, Hyalella azteca, and Chironomus dilutus

Seven-day sublethal toxicity tests were performed with the freshwater invertebrates Ceriodaphnia dubia, Hyalella azteca, and Chironomus dilutus to determine the effects of per- or polyfluorinated alkyl substances (PFAS) of varying chain length within four classes: perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkyl sulfonic acids (PFSAs), perfluoroalkane sulfonamides, and fluorotelomer sulfonic acids. In general, toxicity increased with increasing chain length, but the slopes of these relationships varied markedly by species and chemical class. The toxicity of individual PFCAs was similar among species. The toxicity of PFSAs was similar to PFCAs for C. dubia and H. azteca, whereas PFSAs were much more toxic to C. dilutus, with median effect concentrations (EC50s) as low as 0.022 mg perfluorooctane sulfonate (PFOS)/L and 0.012 mg perfluorononane sulfonate (PFNS)/L. Despite the high sensitivity to PFOS and PFNS, C. dilutus was not very sensitive to structurally similar fluorotelomer sulfonates (6:2 and 8:2). Perfluoroalkane sulfonamides were the most toxic class tested among all species (e.g., EC50s of 0.011 and 0.017 mg perfluorooctane sulfonamide/L for C. dilutus and H. azteca, respectively). The differences in toxicity among species and chemical classes suggest that mechanisms of PFAS toxicity may differ as a function of both. Environ Toxicol Chem 2024;43:359-373. Published 2023. This article is a U.S. Government work and is in the public domain in the USA.

[The use of organic bone matrix as material for direct pulp capping]

The effect of bone matrix soaked in thyrocalcitonin on vitally amputated pulp was studied in beagle dogs with light and electron microscopy. All treated teeth were vital after eight weeks; the area of implantation was densely populated with cells. Formation of hard tissue differing from normal dentinogenesis had begun.

[The use of composite filling materials in endodontics (animal experimental, light and electron microscopic studies]

The tissue affinity of a composite used in root canals was studied in beagle dogs. No pathologic tissue response was observed in the areas surrounding the plastic eight weeks later. Newly formed connective tissue bordered the material. Comparative SEM investigations showed the marginal strength of this type of root filling.

[Therapeutic possibilities in the changing dentition in generalized developmental disorders of the hard substance, ultrastructurally diagnosed I]

Three 5 to 14-year old patients with generalized developmental disturbances of dental hard substance--clinical diagnosis: dentinogenesis imperfecta--are used as examples of age-specific therapy groups in order to demonstrate the various courses of therapy. Early therapy of permanent teeth consists of treating enamel defects with UV hardening resin of the Nuva system. To evaluate adhesion of dental hard substances to resin, it is proposed to use adhesive matrices.