The teeth of many fish, amphibia, and reptiles are attached to the alveolar bone via ankylosis. In contrast, mammalian periodontia are characterized by a gomphosis, an attachment of the tooth root in the alveolar bone socket via periodontal ligament fibers. Among the reptiles, the crocodilians are the only group featuring a gomphosis-type connection between tooth root and alveolar bone, while in other reptiles tooth-root and jawbone are connected via ankylosis. The purpose of the present study was to compare several key features of the crocodilian periodontium with those of the mammalian and noncrocodilian reptile periodontium. As experimental models for our study we chose the periodontium of newborn geckos (Hemidacylus turcicus), juvenile caimans (Caiman crocodilus crocodilus), and 10-day-postnatal Swiss-Webster mice (Mus musculus) as representative models for noncrocodilian reptiles, crocodilian reptiles, and mammals. The caiman periodontium emerged as an intermediary between the mineral-free mouse ligament and the mineralized gecko ankylosis-type attachment. Caiman ligament fibers were less organized than mouse ligament fibers but featured distinct fasciae surrounding ligament fiber bundles. Caiman Hertwig's epithelial root sheath (HERS) was similarly perforated as mouse HERS and distinctly different from the continuous gecko HERS. Both caiman and mouse HERS covered the entire tooth root length, while in the gecko HERS was limited to the coronal portion of the root, allowing for cementoid-mediated ankylosis at the apical tip of the root. We interpret our data to indicate distinct differences in mineral distribution, periodontal ligament fiber organization, and HERS distribution between noncrocodilian reptiles, crocodilian reptiles, and mammals. Mineral deposits in the caiman ligament may reflect an evolutionary position of the caiman periodontium between ankylosis and gomphosis.

Hydrogen peroxide and heat are two components of a technique commonly used to bleach human teeth. The effects of these two components on pulp tissue of dog teeth were evaluated histologically. Hydrogen peroxide alone or with heat caused obliteration of odontoblasts, hemorrhage, resorption, and inflammatory infiltration, while heat alone was not detrimental. Pulpal changes demonstrated evidence of reversibility after 60 d.

Vitamin D-dependent calcium-binding protein (CaBP) was localized in tissue sections of kidneys from rabbits, rats, and chicks using antiserum specific for chick intestinal CaBP. In rabbit kidney, CaBP was present in all cells of the distal convoluted tubule and most cells of the connecting tubule. Fewer, but still a majority, of the cells of cortical collecting ducts contained CaBP. The intensity of immunochemical staining and the number of stained cells decreased markedly in medullary collecting ducts, and only a few collecting duct cells contained CaBP at the junction of the inner and outer medulla. In the rat kidney, CaBP was present in all distal convoluted tubule cells, but the immunochemical staining was less intense than in the rabbit. The protein also was found in most connecting tubule cells of the rat; however, only a few collecting duct cells in the superficial corte of the rat contained CaBP. CaBP was essentially absent from mid- to deep-cortical collecting duct cells, while a very few collecting duct cells always contained CaBP at the junction of the inner and outer stripes of the outer medulla. In the chick, CaBP was present in distal convoluted tubule cells as the distal convoluted tubule coursed adjacent to the central vein. CaBP was absent from chick collecting duct cells. In all three species CaBP was not detected in the other portions of the nephron.

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Increasing saturation of the binding proteins following rises in testosterone production, and the small but significant changes in protein concentration, probably related to postural changes, were implicated as the major factors in the rhythm amplitude. However, the early morning decline in the non-SHBG-bound fraction was not explained by these factors. The rise in cortisol concentration at this time is a probable cause. Alternatively, simulation suggests that a substance appearing in the early morning and competing with testosterone for albumin binding sites may be responsible.