Structure and organization of odontoblasts.

Differentiation of odontoblasts involves cell-to-cell recognition, contact stabilization involving the formation of attachment specializations, cytoplasmic polarization, development of the protein synthetic and secretory apparatus, and the active transport of mineral ions. The secretory odontoblast is characterized by an extensive rough-surfaced endoplasmic reticulum, a highly developed Golgi complex, and the presence of specific secretion granules. Type I collagen, a major constituent of dentin matrix, appears to be secreted by the odontoblast into predentin at the proximal portion of the odontoblast process, the major cytoplasmic process extending from the odontoblast cell body into the dentin. The odontoblast process contains a rich network of microtubules and microfilaments. The proximal portion of the process is also a site of fluid-phase endocytosis. Adjacent odontoblasts are held together by numerous macula adherens junctions and a well-developed distal junctional complex adjacent to be predentin. Junctional strands of the occludens type have been observed to be a component of this junctional complex. Tracer studies employing horseradish peroxidase indicate that this junctional complex does not form a tight barrier to the diffusion of tissue fluid from the interodontoblast spaces into the predentin. Many well-developed gap junctions are formed between adjacent odontoblasts and between odontoblasts and the fibroblasts that make up the subodontoblastic layer. Ca-ATPase activity is demonstrated in the Golgi complex and mitochondrial cristae and along the distal plasma membranes of odontoblasts. ALPase activity is also intense along the entire odontoblast cell surface. The osmium tetroxide-pyroantimonate technique for calcium localization demonstrates prominent reaction precipitates in mitochondria of odontoblasts. Energy-dispersive x-ray microanalysis of anhydrously fixed and processed odontoblasts detected Ca and P peaks throughout the cytoplasm. A sulfur peak is noted in the distal cytoplasm of odontoblasts and in matrix vesicles. Together, these results demonstrate the complexity and variety of cell functions involved in dentinogenesis.

The contributions of Etienne Bourdet (1722-1789) to the diagnosis and treatment of periodontal disease.

Two of the most important figures in the development of the dental profession in eighteenth-century France were Pierre Fauchard and Etienne Bourdet. The title, father of modern dentistry, rightly belongs to Fauchard, for his treatise was the first comprehensive description of dental practice. He broke new ground, and in so doing he set high standards for those who would follow. Bourdet, one generation after Fauchard, was equally effective in describing the practice of dentistry in his treatise published in 1757. The fame of Fauchard continues to overshadow the merit of some of Bourdet's original contributions, especially in the area of periodontal disease. Examination of Fauchard's and Bourdet's concepts of gingival and periodontal pathology, and their methods of managing the disease, reveals many similarities as well as significant differences. Bourdet linked gingival inflammation to local alveolar bone loss with much intuition. In his writings we see the origin of the notions of the gingival pocket, and of an ulcerated pocket epithelium. Furthermore, his treatment rationale was based on a clearly defined concept of the local pathology formed from personal observation.

Multinucleated fibroblastic cells in the periodontal ligaments of aged rats.

Using 12- to 18-month-old rats, we examined the ultrastructural and cytochemical features of multinucleated fibroblastic cells (MFCs) in the periodontal ligament (PDL) of molars. In aged rats, the MFCs were distributed randomly in the PDL and exhibited cytoplasmic structural variations which were not dependent on the number of nuclei. There was a tendency for the MFCs to cluster in the PDL. The MFCs, rich in cytoplasmic organelles involved with procollagen synthesis such as rough endoplasmic reticulum and the Golgi apparatus, incorporated and secreted 3H-proline-labelled products. The MFCs also possessed many phagosomes containing intact collagen fibrils. These MFCs were apparently involved in phagocytosis and intracellular degradation of incorporated collagen fibrils. Phagosome-rich MFCs contain acid phosphatase activity in primary and secondary lysosomes, similar or stronger in intensity to that which can be demonstrated in mononuclear fibroblasts. However, unlike mononuclear fibroblasts, the MFCs did not exhibit alkaline phosphatase activity along their plasma membranes. These results suggest that MFCs demonstrate a range of fibroblastic cellular activity, including collagen phagocytosis, and that they may lack certain plasma membrane glycoproteins, which might explain the occurrence of multinucleation in these cells.

Occurrence of epidermal growth factor-binding sites during differentiation of cementoblasts and periodontal ligament fibroblasts of the young rat: a light and electron microscopic radioautographic study.

Occurrence of epidermal growth factor (EGF)-binding sites during differentiation of cementoblasts and periodontal ligament (PDL) fibroblasts was investigated using radioautography after I. V. injection of 125I-EGF to 14-day-old rats. During differentiation of cementoblasts, a very low level of EGF-binding sites was present on the mesenchymal cells in dental follicle proper, precementoblasts, and cementoblasts. On the other hand, during differentiation of PDL fibroblasts, numerous EGF-binding sites were observed on the undifferentiated paravascular cells and on the perifollicular mesenchymes representing the major source of PDL fibroblast precursor cells. Also heavy labeling was observed throughout their differentiation to PDL fibroblasts, as well as during full synthetic activity as mature cells. Quantitative analysis of the light microscopic radioautographs revealed that these cells demonstrated approximately 4 grains per 100 microns 2 of cell area. These results suggest that EGF plays an important role in differentiation of PDL fibroblasts, but not in that of cementoblasts. Furthermore, the well-known in vivo effect of EGF in producing precocious eruption of teeth may be a consequence of a more extensive effect of EGF throughout differentiation of PDL fibroblasts as well as during full synthetic activity as mature cells.

Voltaire, medicine, and dentistry.

Voltaire, the leading French intellect of the 18th century, was a notorious hypochondriac. His numerous letters contain hundreds of references to his medical and dental disorders, as well as to those of close friends. Voltaire lived to be 84 years old, but not without suffering from several systemic medical disorders and from periodontal disease that left him nearly edentulous by his mid-50s. His dental condition was diagnosed as a scorbutic condition, requiring systemic medication. As a result of neglect and possible mercury intoxication, his condition worsened, and he lost most of his teeth and suffered facial collapse because he did not wear a dental prosthesis. This paper recounts events in Voltaire's life that were connected to his medical and dental history, and in so doing provides a glance at medical and dental practice in 18th-century France.

The status of dental education at Stony Brook in 1991.

The School of Dental Medicine was planned and functions as an integral part of the Health Sciences Center at the State University of New York at Stony Brook. It has been in operation for almost 20 years. The mission of the school is multifaceted. It educates new dentists and scientists at the doctoral level. Its research advances the knowledge on which dental care is provided. Through its clinical activities, the school provides care to people in need and to special segments of the population that are underserved. And its faculty serves as a reservoir of expertise to the profession and the community.

Lessons to be learned from Pierre Fauchard.

Pierre Fauchard possessed the following attributes: Curiosity, intelligence, courage, perseverance, honesty, dexterity, and social responsibility. I suspect that these qualities would have assured him success in whatever career he might have followed. He chose surgery, and through his experience as a ship's doctor in the French navy, he specialized in diseases of the mouth and teeth (common among seamen), qualifying as a surgeon-dentist prior to establishing his highly successful private practice in Paris. In his long career he stood for excellence, the scientific approach, comprehensive care, high ethical standards, and technical innovation. Although we know almost nothing of his private life, his book does reveal a good part of his character. Based solely on this source it is possible to conclude that Fauchard was a true son of the enlightenment, who justifiably holds the title of Father of Modern Dentistry. His treatise contains lessons to be emulated even into the 21st century.

Radioautographic study of [3H]mannose utilization during cementoblast differentiation, formation of acellular cementum, and development of periodontal ligament principal fibers.

The formation of acellular cementum and the deposition of [3H]mannose-labeled extracellular matrix were studied in 14-day-old Sprague-Dawley rats. The sequential events of cementogenesis and periodontal ligament formation observed by light and electron microscopy were described from the stage of an intact root sheath to postcementogenesis. Ultrastructural examination of cementoblasts and periodontal ligament fibroblasts revealed [3H]mannose labeling of the Golgi apparatus at 10 minutes, collagen secretion granules at 30 minutes, and the extracellular matrix beginning at 30 minutes. The extracellular matrix between cementoblasts and dentin was heavily labeled at 1 and 4 hours. Newly formed principal fibers of the periodontal ligament were also heavily labeled at 4 hours. Fully differentiated cementoblasts exhibited the largest sectional profiles and the highest number of silver grains per unit area of cytoplasm. The morphologic and radioautographic data suggest that during the formation of acellular cementum, the cementoblast phenotype is expressed for a short period of time, after which cementoblasts appear to mix with the fibroblasts of the periodontal ligament.

Radioautographic demonstration of receptors for epidermal growth factor in various cells of the oral cavity.

Mouse iodinated epidermal growth factor (EGF) was localized by light and electron microscopic radioautography in basal cells of oral epithelium, papillary cells of the enamel organ, periodontal ligament fibroblasts, preodontoblast precursor cells, and preosteoblasts of the alveolar bone of 13-day-old Sprague-Dawley rats. The specificity of binding in these cells was suggested by an observed reduction of about 90% in the labeling when excess unlabeled EGF was injected along with the 125I-EGF. In contrast, fully differentiated cells, such as ameloblasts, odontoblasts, and osteoblasts, were only poorly labeled. Quantitative analysis of the light microscopic radioautographs revealed that the papillary cells had the highest level of labeling (5.5 grains per 100 micron 2 of cell area). The significance of the rather high labeling of the preosteoblasts of the alveolar bone and the fibroblasts of the periodontal ligament is unknown. However, the well-known effect of EGF in producing precocious eruption of teeth may be a consequence of an effect on these two cell types.

H+-K+-ATPase activity in the rat incisor enamel organ during enamel formation.

The enamel organ of growing rat incisors was perfusion-fixed with a mixture of formaldehyde and glutaraldehyde and processed for ultracytochemical demonstration of ouabain-resistant, K+-stimulated p-nitrophenylphosphatase representing the second dephosphorylative step of H-K-ATPase by use of the one-step lead method. Throughout the stages of amelogenesis, the enzymatic activity was found in the plasma membranes, mitochondrial membranes, and lysosomal structures of the cells of stratum intermedium, papillary layer, and ameloblast layer. Gap junctions and desmosomes between these cells were, however, free of reaction product or showed slight precipitates of reaction. The stellate reticulum and the outer enamel epithelium at the stage of enamel secretion were usually negative for reaction. Although secretory, transition, and ruffle-ended maturation ameloblasts showed enzymatic activity at their basolateral cell surfaces, their distal cell surfaces facing the enamel were always free of reaction product. On the other hand, the smooth-ended maturation ameloblasts seldom showed a positive reaction, except in lysosomes and along their basal cell surfaces. An energy-dispersive X-ray microanalysis of reaction products of H-K-ATPase in unosmicated tissue sections demonstrated that they were composed of lead and phosphorus, which had been released during the dephosphorylation of substrate. In cytochemical controls, the enzymatic activity was completely dependent on substrate and potassium ion, resistant to ouabain and levamisole, and inhibited by nolinium bromide, a specific inhibitor of H-K-ATPase. In addition, inorganic trimetaphosphatase as enzymatic marker of lysosome was localized in dark and pale lysosomes, phagosomes, multivesicular bodies, and ferritin-containing vesicles of the ameloblasts and the cells of stratum intermedium and papillary layer. These membrane-bound structures were also positive for H-K-ATPase reaction. These results suggest that: 1) H-K-ATPase functions to maintain an acidic internal pH of lysosomes in the enamel organ cells; and 2) H-K-ATPase localization in the plasma membranes of enamel organ cells is concerned with efflux of protons derived from cytoplasmic water.