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PubMed1975

Periodontosis in sibs.

Periodontosis is an idiopathic degeneration of the periodontium which results in migration and loss of teeth. The disease begins in the regions of the incisors and first molars. Late in the disease, other areas of the dental arches may be involved. The gingivae are not initially inflamed, and there are no associated systemic abnormalities. Local irritants cannot account for the marked alveolar destruction which leads to the tooth loss. Several heritable syndromes and periodontitis also may be associated with alveolar bone destruction. Periodontosis can be differentiated each of these on the basis of negative laboratory tests, lack of associated anomalies, distinctive pattern of bone loss and timing of onset of gingival inflammation. A family in which periodontosis was present in three of six sibs and in which ichthyosis was segregating independently of periodontosis is reported.

Adolescent↗
PubMed1996

Management of dens evaginatus: evaluation of two prophylactic treatment methods.

Dens evaginatus (DE) is an odontogenic anomaly characterized by an enamel covered tubercle, enclosing dentin and pulpal tissue. It most commonly affects premolar teeth of people of mongoloid ethnicity. The prevalence of DE in Singapore is 2.1%. Fracture or attrition of the tubercle may lead to pulpal necrosis. Thus, prophylactic management of DE is preferred. A retrospective cohort study comparing two common prophylactic restorative methods was conducted. This involved 817 children, aged 10 years at the outset, having 1591 DE. The teeth were observed for 2 years. The results showed that significantly less teeth developed pulpal pathology when an enamoplasty-preventive resin restoration method was used (0.52%) as compared to an amalgam cavity restoration (5.37%) and the control (3.65%) [chi 2 = 9.595 (p < 0.01) df = 2]. Knowledge of the various treatment options and prevalence data is important as there is an increasing global migration of people of mongoloid ethnicity.

Asian People↗
PubMed1981

Ultrastructure of differentiating preameloblasts from tooth germs of the permanent dentition of Macaca mulatta and Macaca arctoides.

Cytodifferentiation of inner enamel epithelium and the adjacent connective tissue from the tip of the cervical loop to the initiation of enamel elaboration in two Macaca species was examined. Ten- to twelve-month-old specimens were fixed by perfusion and the permanent tooth buds were prepared for transmission electron microscopy. At the cervical loop proper, inner enamel epithelium cells have lobed nuclei, a paucity of cytoplasm, and wide extracellular spaces; the basal lamina facing the dental papilla is straight. With increasing distance from the tip of the cervical loop, the following changes occur gradually: (a) preameloblasts elongate from 15 to 45 micrometers, and their organelles, particularly mitochondria and profiles of rough endoplasmic reticulum, become more numerous; (b) extracellular spaces decrease between preameloblasts starting at the basal (infranuclear) end; (c) the basement membrane becomes convoluted and associated with aperiodic fibers; (d) preodontoblast projections penetrate the aperiodic fibers; (e) collagen fibers subjacent to the basement membrane increase in density, with particularly thick fibers paralleling the aperiodic fibers. These modifications occur within three-fourths of the distance from the tip of the cervical loop to the mineralization front. The condensation of preodontoblasts is followed immediately by predentin synthesis. Concomitantly, the basement membrane breaks down and the aperiodic fibers are engulfed by preameloblasts. Preameloblast projections penetrate junctional predentin, contact mineralized dentin, and enamel synthesis ensues. At this stage the ameloblast is 45 micrometers long, the nucleus is central or basal, the Golgi apparatus has migrated apically, but the Tomes' process has not yet formed. The results indicate that odontogenesis in Macaca monkeys more closely resembles human odontogenesis than does that in the murine rodents.

Ameloblasts↗
PubMed1992

Nonmetric tooth crown traits in the Ami tribe, Taiwan aborigines: comparisons with other east Asian populations.

The frequencies of occurrence of 17 tooth crown traits in the living Ami tribe, which inhabits the east coast of Taiwan, were investigated and compared with other East Asian populations based on Turner's (1987) Mongoloid dental variation theory. Principal coordinate analysis based on Smith's mean measure of divergence using frequencies of the 17 traits suggests that the Ami tribe together with the Yami tribe and the Bunun tribe is included in the sinodont group typical of the Chinese mainland and northeast Asia. In light of these results and the estimated distribution of sinodonty and sundadonty in the past and the present, we speculate that the gene flow from Chinese mainlanders to native sundadonts, who seem to have migrated northward to Taiwan, contributed significantly to the formation of the living Taiwan aboriginal groups, sinodonts. Among the aboriginal tribes of Taiwan, the Ami have characteristics intermediate between those of the Yami and the Bunun. The relative positions of these tribes in East Asian populations suggests that the extent of sinodontification and of genetic isolation is one of the causes of the intertribal variation.

Adolescent↗
PubMed1991

Epithelial-connective tissue interaction on the tooth surface: an in vitro model.

In the present study, and in vitro system was developed and designed to examine the interaction between gingival fibroblasts (GF) and epithelial cells (EC) on the tooth surface. Porcine roots were cut transversely into 300 microns-thick root slices (RS). Gingival explants were placed on the upper RS surface and cultured in a defined medium permissive for the growth of EC. After 4 or 6 days, RS yielding EC were transferred onto confluent cultures of GF and further co-cultured for either 4 or 8 d. Cultures were then fixed and examined by SEM. The upper RS surfaces and the upper half of their peripheral aspect were covered by EC. The lower half of the peripheral RS surfaces were populated by GF originating from the confluent culture of GF. EC and GF made contact at approximately the middle of the side of the root slice. In cultures of epithelial components grown in defined medium for either 4 or 6 d and harvested 4 d after assembling the system, the EC-GF junction was located 117 +/- 45 and 271 +/- 82 microns, respectively from the upper RS aspect. Extending the co-culture period did not affect the EC-GF junction location. These results indicate that GF-EC contact stops the migration of these cells on root surfaces in vitro. The described system should be valuable for studying cellular events that may affect the formation of a new dentogingival junction following surgical periodontal therapy.

Animals↗
PubMed1979

On the progenitor cell migration velocity.

An attempt is presented to extract cell kinetic information from histomorphological features. It is applicable to rapidly proliferating tissues like the intestinal epithelium. Each replicating tissue has an origin where cells are formed and a periphery toward which cells migrate. The migration path along which they move is denominated as tissue radius on which all cell positions are mapped. Cell migration on the radius is associated with cell proliferation at tissue origin. Each mitosis there is associated with the displacement of all cells distal to it by one cell position. The more mitoses positioned between a cell and tissue origin, the greater its migration velocity. It is possible therefore to derive the cell migration velocity v(x) from the cumulative mitotic distribution on the radius, N(x). v(x) = N(x)/tm (tm = mitotic time). In this form v(x) represents also cell production at any point on the radius and may serve for the computation of other cell kinetic parameters like generation time. These arguments are illustrated on the rat incisor tooth inner enamel epithelium which has been studied in the normal and rapidly erupting tooth.

Ameloblasts↗
PubMed1977

[Physiology of the gingivo-dental sulcus].

The gingival sulcus is formed by the space between the sulcular epithelium, the junctional epithelium, and the wall of the tooth. The functioning of its different parts is important in the early changes taking place when marginal plaque is accumulating. The cellular turnover of the junctional epithelium is very high, which could explain its high healing potential. The intercellular spaces are wider in the junctional epithelium, when compared to those of the sulcular or oral epithelia. Polymorphonuclear leucocytes can migrate through these spaces, attracted toward the sulcus by chemotactic substances. Numerous substances have been shown to permeate the junctional epithelium, both toward the sulcus and from the sulcus within the connective tissue. The sulcus is normally sterile and will tend to eliminate any foreign particle. Leucocytes and desquamated epithelial cells will also tend to leave the gingival sulcus and will be found in saliva. Various instruments, such as paper or celluloid strips of platinum loops, can be used to collect the content of the gingival sulcus. Quantitative investigations can be performed by analyzing crevicular fluid or the products of washings of the marginal gingiva.

Epithelial Cells↗
PubMed1983

Morphology and permeability of junctional complexes in maturing ameloblasts of rat incisors.

Thin sections of newborn rat incisors were examined by tracer experiments and freeze-fracture replication in order to clarify the morphology and permeability of ameloblast junctional complexes in the maturation stage. Ameloblast junctional complexes consisted of gaps and tight junctions at the proximal and distal ends. Whereas the proximal junctional complexes sealed extracellular spaces incompletely, the distal ones formed complete, belt-like barriers around the cell. Tight junctions of these junctional complexes, however, were composed of both continuous and discontinuous rows of particles with various spaces among them. Intravenously injected horseradish peroxidase (HRP) reached the enamel surface through the extracellular spaces among ameloblasts and was absorbed by ameloblasts of the ruffled borders. Pinocytosis and transcellular migration of HRP could not be demonstrated in maturing ameloblasts except in the ruffled border zone.

Ameloblasts↗
PubMed1975

Cellular renewal in the enamel organ and the odontoblast layer of the rat incisor as followed by radioautography using 3H-thymidine.

Renewal of the cell populations of the incisor was studied in 100 gm male rats injected with a single dose of 3H-thymidine and sacrificed at various times from one hour to 32 days after injection. Radioautographs showed that a cohort of labeled cells within the enamel organ, odontoblast layer, and pulp was carried passively with the erupting incisor from the apical end towards the gingival margin where the life cycle of these cells was terminated. Labeled cells in the upper and lower incisor, although traversing different absolute lengths, were found in approximately the same functional stage of their life cycle at similar times after the injection. Thus, by one and on-half days labeled ameloblasts began inner enamel secretion and, by eight days (upper) or nine days (lower), complement outer enamel secretion. By 32 days labeled ameloblasts had traversed the entire enamel maturation zone and were located at the gingival margin. Labeled odontoblasts followed closely the movement of labeled ameloblasts. The mean rate of ameloblast migration was 567 mum/day on the upper incisor and 651 mim/day on the lower. For the odontoblasts this rate was 55 mum/day (upper) and 631 mum/day (lower). Finally, it was found that as the rat age, the duration of the life cycle for epithelial and pulp cell populations of the incisor increased because of growth within the lonitudinal axis of the tooth. It was concluded that the apical end of the incisor literally "grows backward" in the bony socket, and hence, the duration of the life cycle becomes greater simply because it takes cells longer to physically reach the gingival margin.

Ameloblasts↗
PubMed1984

The role of ascorbic acid deficiency in human gingivitis--a new hypothesis.

Periodontal disease is one of the most prevalent health problems in the world and is the major cause of tooth loss in the adult population. Its two major subdivisions are gingivitis where disease is confined to the gingiva, and periodontitis where disease is present both in the gingiva and the supporting periodontal tissues. During the first stage there is a vasculitis of vessels subjacent to the junctional epithelium which is followed by exudation of fluid from the gingival sulcus and migration of leukocytes. There is variable expression of this stage throughout the mouth with new areas of involvement appearing in place of healed areas. Mast cells which are present in the gingival connective tissues may participate in this inflammatory response by liberating histamine. Ascorbic acid deficiency has been shown to be a conditioning factor in the development of gingivitis. When humans are placed on ascorbic acid deficient diets there is increased edema, redness and swelling of the gingiva. These changes have been attributed to deficient collagen production by gingival blood vessels. However, this may be due to an antihistamine role of ascorbic acid. This vitamin may act to directly detoxify histamine or effect a change in the level of enzymes responsible for histamine metabolism. This could occur through the influence of ascorbic acid in altering cyclic AMP (c-AMP) levels. Such changes in the level of this regulatory molecule could result in increased histamine-N-methyl transferase and other enzymes responsible for the breakdown of histamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Development of a three-dimensional extracellular matrix synthesized by human diploid fibroblasts in vitro.

Development and maturation of an extracellular matrix, synthesized by human gingival fibroblasts, have been studied microscopically. Pairs of demineralized, fibronectin-coated slices of human tooth root, 300 micron thick, were placed on confluent cell layers, defining a 0.5 mm wide space. The cultures were grown under standard conditions with ascorbic acid (50 micrograms ml-1) added daily. At various times up to 13 weeks, the cultures were fixed and the samples prepared for light and electron microscopy. Cells from the monolayer became attached to, and migrated up, the vertical root surface and, during the time studied, completely filled the space between the root slices with an extracellular matrix. A close association was seen between the cell membrane and collagen fibres in the demineralized surface initially. A thin layer of fibrillar material was deposited between the cell and the vertical surface, and eventually an extracellular matrix surrounding the cells and attaching to the root surface was present. Samples fixed in the presence of Ruthenium Red showed intense staining of the fibrillar material, indicating the presence of anionic molecules. Additional cells migrated onto the newly synthesized matrix and up the root surface. Growth of the fibrillar networks on either side, horizontally and vertically, continued and, eventually, an extracellular matrix attaching to the vertical surfaces completely filled the previously empty space. Immunocytochemical staining showed that the matrix contained hyaluronic acid, chondroitin sulphate, dermatan sulphate and fibronectin at this time. Collagen fibres were observed at 6 weeks, and at later times collagen types I, III and V were the primary matrix components. The fibroblasts attaching to the root slice and those present at the edge of the matrix had an elongated, polar form. The cells within the matrix frequently showed a stellate appearance with numerous extended processes, in contact with fibrillar material or collagen fibres. Fibroblast processes were at later times seen to enclose bundles of collagen fibres and to mediate cell-to-cell contact, occasionally via desmosome-like structures. The structure and composition of the matrix and the appearance and apparent behaviour of the cells were similar to that observed in the healing wound. This system thus could provide a model for studying various aspects of regeneration of extracellular matrix.

Collagen↗
PubMed1990

Relationships between tooth eruption, occlusion and alveolar bone resorption: histochemical and cytological studies of bone remodeling on rat incisor alveolar bone facing the enamel after root resection.

The labial side of rat incisor alveolar bone facing the enamel is continuously resorbed as the result of compressive force produced by the occlusion and eruption of incisors. In order to clarify the relationship between this mechanical compressive force and the bone cells involved in bone remodeling, we examined morphological changes occurring in the alveolar bone once the compressive force was eliminated by the removal of the proliferative odontogenic base (root resection according to Berkovitz and Thomas, 1969). After root resection, the incisor migrated halfway along the socket. On the crestal part where incisor still existed, active osteoclasts were prominent on the bone surface, and flattened mononuclear cells lay close upon active osteoclasts. Sinusoidal blood vessels or capillaries were observed at short distances from the bone surface. On the basal part where socket was vacant, osteoblasts lined up on the newly formed bone, and the osteogenic cell layer lay on the osteoblasts. Between the two parts, which correspond to the reversal phase proposed by Baron (1977), osteoblastic cells with developed cell organelles increased in number and the distance between blood vessels and bone surface increased. Osteoclasts reduced their activities, and osteoblastic cells often wedged themselves between the osteoclasts and bone surface. These findings indicate that the elimination of compressive force mediated by incisors leads to the activation of osteoblastic cells and inactivation of osteoclasts, which results in a conversion from bone resorption to bone formation. Thus, osteoblastic cells may play an important role in controlling osteoclastic activity in conversion from bone resorption to bone formation, partly by a direct effect and partly by controlling the access of blood vessels to the bone surface.

Acid Phosphatase↗
PubMed1993

Gene expression of CD24 core peptide molecule in developing brain and developing non-neural tissues.

CD24 is a signal transducing molecule on the surface of most human B cells, murine immature T cells, myeloid and erythroid lineage cells. We isolated rat CD24 gene from embryonic brain cDNA library and characterized the gene expression during rat embryogenesis. Rat CD24 cDNA is homologous to murine and human CD24 gene with respect to the structure of signal peptide, N-glycosylation sites, and possible glycosyl phosphatidylinositol (GPI) linker attaching site, suggesting that rat CD24 is a transducing glycoprotein anchoring membrane via GPI linker. In the developing embryo, in situ hybridization analyses revealed that CD24 transcript was detected in primitive ectoderm, mesoderm, and ventral endoderm of day 9 postcoitum (p.c.) embryo. In central nervous systems CD24 transcript was strongly expressed in postmitotic cells of spinal cord, hindbrain, midbrain, and forebrain from day 11 p.c. embryo to day 21 p.c. embryo but was dramatically down regulated in adult brain. Furthermore, expression was also detected in epithelium during development of non-neural tissues, such as intestinal mucosal epithelium, nasal epithelium, ductal epithelium of salivary gland, bronchial epithelium, renal tubular epithelium, and hair follicles. In tooth development, where correct epithelium requires epithelial-mesenchymal interactions, CD24 mRNA was specifically induced in mesenchymal cells differentiating into odontoblast in dental papilla, suggesting the pivotal role of CD24 molecule in cell differentiations in vivo. We suggest that CD24 gene may encode the core peptide molecule of 31 kDa GPI linked molecule which has been known to be important in the migration of neurons on astroglial processes during development.

Amino Acid Sequence↗
PubMed2002

Quantitative studies on the movement of fluid and lymphocytes through periodontal tissue and into the draining lymph.

Chronic lymph drainage techniques in sheep have been used to map the pathways and to quantify the fluid and cell traffic through periodontal tissues. The continuous collection of cervical and prescapular lymph has demonstrated that 65% of labelled protein tracer injected into the periodontal tissues could be found in lymph over a period of 7.5 hours. Nearly 90% of the total radioactivity could be accounted for between the lymph and the tissue site. When silk was impregnated with radiolabelled albumin and a tooth ligated, the kinetics of the subsequent appearance of the tracer in lymph emphasized the ease with which macromolecules surrounding the teeth gain access to the lymphatics, regional lymph nodes, and immune apparatus. Animals were primed with BCG and then tuberculin (delayed hypersensitivity) lesions were simultaneously induced in the skin, bowel, and periodontium. When T cells were labelled with radioisotopes and their migration from blood to lymph measured, the periodontal tissue traffic pattern was distinct from the traffic pattern through DTH in the skin and also distinct from the pattern through the small intestine. This indicates that the lymphocyte traffic through the inflamed periodontium has unique features. This tissue specificity was not apparent when lesions were induced with TNFalpha. The static assessment of lymphocyte subsets within the tissues was also assessed with immunohistochemistry.

Animals↗
PubMed1996

Dendritic cells: a novel cellular component of the rat incisor enamel organ appearing in the late stages of enamel maturation.

Immunocompetent cells in the enamel organ of rat incisors were examined immunohistochemically using OX6, ED1, and ED2 monoclonal antibodies known to recognize the Class II MHC molecules, a monocyte-macrophage lineage, and residential macrophages, respectively. The OX6 immunopositive cells (MHC cells) were located exclusively in the enamel maturation zone. MHC cells increased in number in the incisal direction and occasionally extended cytoplasmic processes deep into the ameloblast layer. Migration of MHC cells in the ameloblast layer were also encountered. MHC cells lacked phagolysosomes and could be distinguished from typical macrophages. ED2 immunopositive cells were not seen in the enamel organ. ED1 positive cells displayed identical localization to MHC cells except that some appeared in the transitional zone. MHC cells could not be seen in the enamel organ of rat molar tooth germs. Our data confirmed the presence of a large population of "dendritic" immunocompetent cells in the enamel organ of rat incisors and characterized the ultrastructural features of these cells. Biological significance of the immunocompetent cells in the enamel organ during amelogenesis needs to be clarified.

Amelogenesis↗
PubMed2026

The Long Haul: Microtubule Motors as the Essential Supply Line for Neuronal Longevity.

The extreme morphology and polarised architecture of neurons require the highly sophisticated microtubule transport system for both construction and lifelong survival. Genomic evidence from an expanding landscape of human mutations supports the essential role of the microtubule transport machinery. During neurodevelopment, mutations disrupt the proliferation and migration of neuronal precursors, as well as the initial establishment of polarity. In the mature nervous system, the reliance on microtubule transport shifts to the long-term maintenance of axon integrity and synaptic proteostasis. Across the motor proteins responsible for long distance transport in neurons, mutations highlight a specific vulnerability of long axons to transport failure in Hereditary Spastic Paraplegia (HSP), Charcot Marie Tooth disease Type 2 (CMT2), Spinal Muscular Atrophy (SMA), Perry Syndrome, and Amyotrophic Lateral Sclerosis (ALS) amongst others. Due to the role of microtubule motors in development and maintenance, there is frequently a phenotypic spectrum within a single gene of the microtubule transport system. For example, mutations in dynein motors are linked both to malformations of cortical development and specific motor neuron loss in SMA-LED (Spinal Muscular Atrophy with Lower Extremity Predominance). By synthesising genetic evidence, this review illustrates how specific molecular failures, ranging from motor-domain kinetics to cargo binding, can inform our understanding of neuronal homeostasis. Ultimately, we argue that microtubule transport is not merely a cellular utility, but a key determinant of neuronal longevity.

Humans↗
PubMed1988

Effect of citric acid treatment on the migration of epithelium on root surfaces in vitro.

Explants of bovine gingival mucosa were cultured for four days on scaled and citric acid-conditioned root surfaces. Demineralization of the hard tissue with citric acid exposed the collagenous matrix of the root. Undemineralized islands were frequently seen among the collagen fibers of the treated roots. When cultured on scaled, control root surfaces, the epithelium migrated inwards between the connective tissue of the explant and the root surface. On citric acid-treated roots, epithelial migration in this direction was rare although it was possible. Citric acid treatment of the substratum directed the epithelium to migrate outwards from the explant. Only a few of the controls showed epithelial migration to the outward direction. The findings indicate that demineralization of the root surface has an influence on the direction in which the epithelium initially starts to migrate. An induced delay of epithelial migration between the gingival connective tissue and the hard tissue may be favorable for connective tissue attachment to the root surface.

Animals↗