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Results for “Periodontal Ligament”

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At least 19 recordsLinked to original sources

PubMed1979

The absence of proprioceptive nerve endings in the human periodontal ligament: the role of periodontal mechanoreceptors in the reflex control of mastication.

A review of the literature was conducted to determine the presence or absence of proprioceptive nerve endings in the human periodontal ligament. A histologic review of the periodontal ligament innervation concluded that nerve endings found were those mediating pain, pressure, or touch and that there is no histologic evidence of any "classic" proprioceptive nerve ending in the periodontal ligament. A summary is given concerning the precise role of nerve endings in the periodontal membrane, their afferent pathways, and the role of masticatory muscle proprioception, jaw reflexes, and the temporomandibular joint in the coordinated control of mastication and mandibular proprioception.

Afferent Pathways↗

PubMed1979

Procollagen synthesis and processing in periodontal ligament in vivo and in vitro. A comparative study using slab-gel fluorography.

A combination of dodecylsulphate/polyacrylamide gel electrophoresis and fluorography has been used to quantify the synthesis of type I and type III collagens by periodontal ligament in situ and periodontal-ligament fibroblasts in vitro. The separation of 14C-labelled collagen alpha chains was achieved by introducing an interrupted reduction step, and the total radioactivity in the alpha-chain bands related to the fluorographic response by a series of standard curves. From these curves an accurate assessment of the relative amounts of type I and III collagen synthesized could be made. The same system also allowed the synthesis and processing of the respective procollagens to be analyzed. For the study in vivo, 200-g male rats were injected with 2 mCi [14C]glycine and killed 0.5-6 h later. Periodontal ligament was dissected from the mandibular molars and the newly-synthesized collagens extracted with 0.45 M sodium chloride. In the study in vitro, confluent monkey periodontal-ligament fibroblasts were cultured in the presence of [14C]proline and [14C]glycine. Analysis of labelled collagens showed a rapid conversion of type I procollagen to collagen but type III collagen was recovered as a procollagen intermediate both in vitro and in vivo. Analysis of duplicate samples after pepsin digestion showed type III collagen synthesis to comprise 15% of the total collagen synthesized in vivo and 20% in early subcultures in vitro. However, the proportion of type III synthesized by the fibroblasts decreased on subculturing. The data demonstrate that fibroblasts in vitro retain the basic characteristics of collagen synthesis and procollagen processing found in vivo, but the overall phenotypic expression of the cells is not stable in culture.

Animals↗

PubMed1979

Light and ultrastructural relationship between oxytalan fibers in the periodontal ligament of the guinea pig.

The interfaces and the relationships between collagen and oxytalan fibers were observed under light and electron microscopy. Guinea pig periodontal ligament was prepared for light and electron microscopy with perfusion using Peter's buffered formalin for light microscopy and GTA-S-collidine and OSO4 for electron microscopic studies. The tissue for light microscopy was stained with a modified Gomori's aldehyde fuchsin technique, in which pre-oxidization with potassium monopersulfate was carried out before staining so as to demonstrate the oxytalan fibers. EM tissues were routinely stained with lead citrate and uranyl acetate. Two different structural relationships were observed. First, the subcomponents of the collagen and oxytalan fiber types interweave with each other; and, second, some of these two-fiber subcomponents appear attached to each other. These relationships and the known orientation of oxytalan fibers as seen in the periodontal ligament provide insight as to the function of oxytalan fibers. The oxytalan fibers may provide increased structural integrity and increased distribution of forces over a wider area of the periodontal ligament. Because of their close relationship to blood and lymph vessels in the periodontal ligament, they may also help to stabilize these elements by the same structural relationships to collagen fibers.

Animals↗

PubMed1979

Remodelling of collagen fibers in the periodontal ligament and the supra-alveolar region.

Although the rate of turnover of collagen in the periodontal ligament may be somewhat higher than in the gingiva, it is doubtful whether this is the only factor that may explain why rearrangement of collagen fibers in the ligament occurs much more rapidly than in the supra-alveolar region under certain experimental conditions. It may well be that there are other factors that determine the ability of the periodontal tissues to rearrange themselves. On the basis of the distribution pattern of collagen phagocytosis by fibroblasts and the pattern of incorporation of 3H-proline it seems that turnover of collagen, at least in the periodontal ligament is evenly distributed across the width of the tissue. However, local variations in the presence of cells containing intracellular collagen fibrils may occur, as indicated by the observation that a relatively high concentration of ingested collagen fibrils is seen in fibroblasts in the direct vicinity of osteoclasts. It is suggested that coordinated action of fibroblasts and osteoclasts near the alveolar bone surface may represent part of a local mechanism through which rapid remodelling of certain areas in the periodontal ligament may be accomplished.

Alveolar Process↗

PubMed1975

Autoradiographic study of 3-h-proline incorporation by rat periodontal ligament, gingival connective tissue and dental pulp.

The rates of 3-H-proline incorporation by the rat periodontal ligament, the gingival connective tissue and the dental pulp were studied by autoradiography. The rate of 3-H-proline incorporation by the periodontal ligament was 2.8 times higher than by the gingival connective tissue and 5 times higher than by the dental pulp. These differences were significant (p smaller than 0.01). The pattern of 3-H-proline incorporation by the periodontal ligament was significantly different (p smaller than 0.01) from that by the gingival connective tissue and the dental pulp. The latter two tissues exhibited a similar pattern of 3-H-proline incorporation. The ratio of the rates of 3-H-proline incorporation by the three tissues did not correlate with the ratio of the cellular densities in the same three tissues.

Animals↗

PubMed1977

In vitro strength of the human periodontal ligament.

The tensile properties of the human periodontal ligament were studied by direct loading and compression experiments. It was found that the ligament behaved in an elastic manner up to an elastic limit after which rupture occurred. The values obtained for the tensile strength of the ligament are in general agreement with those of other workers for similar tissues.

Dental Stress Analysis↗

PubMed1977

The oxytalan fiber system in the mandibular periodontal ligament of the lathyritic mouse.

Experimental lathyrism was produced in young albino mice with a diet containing 50% sweet pea seed (Lathyrus odoratus). After 7 days on the lathyritic diet, sections of themandibular molar and incisor periodontal ligaments, when oxidized and treated with aldehyde fuchsin, demonstrated enhanced staining of the oxytalan fibers and numerous vessels. At this time aldehyde fuchsin or orcein also revealed marked pathological changes in the periodntal ligament of all molars. When athyrism was prolonged for 12 weeks, both the molar and incisor oxytalan systems were still readily identifiable although the molar periodontal ligament continued to be serverely affected by lathyrism. The oxytalan fibers retained their characteristic tooth-vascular association in all of the lathyritic mice. Oxytalan fibers of the lathyritic and control animals showed similar reactions to enzyme digestion with beta-glucuronidase, elastase, and pepsin. However, gingival elastic fibers reacted in a different way from oxytalan fibers with beta-glucuronidase and elastase treatment. These findings indicate that in the lathyritic mouse the oxytalan fiber system of functioning teeth possesses a high degree of permanence and is metabolically distinct from collagen and elastic fibers.

Animals↗

PubMed1977

Cultivation of periodontal ligament fibroblasts on extracted monkey incisor. A histologic study of three culturing methods.

Forty-two permanent incisors were extracted from green vervet monkeys and cultivated in Eagle's medium at 37 degrees C using the following culture methods: 1. teeth placed at the bottom of the culture flask; 2. teeth placed in an upright position in the culture flask and supported by an open glass cylinder; 3. teeth placed in an upright position in the culture flask and supported by a semisolid tissue culture medium. The teeth were cultured from 1 to 21 days and then examined histologically and periodontal changes registered histometrically. After 2 days, most of the periodontal membrane showed signs of extensive cell necrosis. After 3 days the first signs of proliferation of cells were seen either as clusters around existing vessels or as a surface layer on the periodontal membrane. After 7 days an almost complete over of connective tissue cells had formed on the root surface. This layer had formed on periodontal ligament with cell necrosis as well as on areas with preserved vitality of the periodontal cells. Areas on the root surface without periodontal ligaments were also covered with a cell layer. No significant change took place within the periodontal membrane with extended culture periods (2 and 3 weeks). Better results were achieved using liquid medium as compared with semisolid medium.

Animals↗

PubMed1979

The role of the periodontal ligament in overdenture treatment.

The results of this experiment suggest that the periodontal ligament plays a role in the efficiency of muscular activity during chewing in patients wearing overdentures. A masticatory index as an indicator of the efficiency of masticatory movement is proposed in this research.

Aged↗

PubMed1978

[In vitro study of the role of periosteum and the periodontal ligament in the bone repair process].

For the study of the role of periosteum and periodontal ligament in the phenomena of bone repair, fragments of palatal mucosa and maxillary or mandibular bone from adult rats and devoid of periosteum were cultivated in association. The survival went beyond 26 days. In the bone, the ligament side showed by the 12th day signs of osteogenesis, whereas the other side devoid of periosteal osteoblasts showed empty lacunea, as it is observed "in vivo".

Animals↗

PubMed1977

[Ultrastructural demonstration of the phagocytic activity of periodontal ligament fibroblasts in the rat using enzymatic tracers].

The ultrastructural study of non-decalcified periodontal ligament of rats, labeled with horseradish peroxidase used as an enzymatic tracer for the mechanism of endocytosis, shows that there exists in the fibroblast, on the one hand, an endogeneous peroxidase revealed by the preparation and characteristic of certain cellular organelles: mitochondria, free ribosomes, ribosomes of the granular endoplasmic reticulum; and on the other hand an exogeneous peroxidase which demonstrates the ability of fibroblasts to phagocytose. This exogeneous peroxidase initially marks the collagen fibrils located in the extracellular medium, then at a later time he cytoplasmic membrane during its invagination, and finally the membrane of phagosomes. The intracellular collagen situated at the interior of phagosomes is also marked by the peroxidase and demonstrates the passage of the collagen from the extracellular medium to the intracellular medium.

Actin Cytoskeleton↗

PubMed2026

Effects of umbilical cord mesenchymal stem cell-derived exosomes on periodontal ligament stem cells: An exploratory study.

OBJECTIVE: To investigate whether exosomes derived from human umbilical cord mesenchymal stem cells (UCMSCs) at two osteogenic induction stages (undifferentiated and late-stage) differentially affect periodontal ligament stem cells (PDLSCs), and to explore the potential molecular basis. DESIGN: UCMSCs and PDLSCs were isolated and cultured. Exosomes were harvested from undifferentiated UCMSCs (Exo-D0) and UCMSCs after 14 days of osteogenic induction (Exo-D14). PDLSCs were treated with both exosome types. Proliferation and migration were analyzed using EdU and scratch assays, the latter under serum-free conditions. Early osteogenic differentiation was assessed by alkaline phosphatase staining and quantitative reverse transcription PCR (qRT-PCR). Differentially expressed miRNAs were identified by high-throughput sequencing and further analyzed through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. RESULTS: Both exosome types promoted PDLSC migration. Exo-D0 enhanced early osteogenic differentiation, whereas Exo-D14 enhanced proliferation but reduced early osteogenic marker expression. Sequencing identified 21 differentially expressed miRNAs (13 upregulated, 8 downregulated). Bioinformatic prediction suggested that the putative target genes were enriched in Ras signal transduction, regulation of kinase activity, and focal adhesion, and further predicted significant enrichment in the MAPK, Ras, and PI3K-Akt signaling pathways, which are central to cell proliferation and osteogenic differentiation. CONCLUSIONS: Exosomes from undifferentiated and osteogenically induced UCMSCs exerted distinct effects on PDLSCs, potentially associated with differentially packaged miRNAs. These findings offer a basis for hypotheses about exosome-mediated mechanisms and support matching exosome sources to the intended therapeutic outcome as potential cell-free strategies for periodontal tissue regeneration and alveolar bone repair.

Humans↗

PubMed1975

Bovine periodontal ligament. An invesitation of the collagen, glycosaminoglycan and insoluble glycoprotein components at different stages of tissue development.

Periodontal ligaments from unerupted, partially erupted and mature teeth were extracted with 0.15 M NaCl. The major reducible collagen cross-link in each insoluble fraction was dehydrodihydroxylysinonorleucine; the dehydroydroxylysinonorleucine contents were smaller. There was no significant difference in the quantities of these cross-links relative to collagen contents in the three speciments, but one of the precursors, hydroxyallysine, markedly decreased in the older tissue. The amino acid compositions of the trypsin-resistant insoluble fractions were generally characteristic of collagen. Analyses of separated glycopeptides revealed the presence of insoluble non-collagenous glycoproteins and collagen hexoses. The latter were lower in the mature ligament. Hyaluronic acid progressively decreased relative to chondroitin sulphate on eruption and maturation. A hyaluronidase-resistant glycosaminoglycan, probably dermatan sulphate, occurred in the NaCl-insoluble fraction of the mature ligament and in appreciable amounts in all NaCl extracts.

Animals↗

PubMed1979

Circadian periodicity of the cell kinetics of rat molar periodontal ligament.

Circadian periodicity of DNA synthesis (S) phase and mitosis over a complete 12-hour light/12-hour dark cycle was studied in rat molar periodontal ligament (PDL) with 3H-thymidine autoradiography. Maximum percent labeled cells was at 10 A.M. in all regions, and mean labeling (24-hour average) was 1.44, 0.93, and 1.46 percent for the crest, midroot, and apical areas of the PDL, respectively. Maximum percent mitotic figures were also at 10 A.M. in all areas studied, and the mean number of mitoses averaged over 24 hours was 0.19, 0.12, and 0.14, respectively for crest, midroot, and apical areas. Ratios of mean labeling and mitotic indices were 7.58, 7.75, and 10.43 from crest to apex. Duration of mitosis and S phase were estimated at 1.2 and 9 hours, respectively. Analysis of data suggested that stress/strain within the PDL, associated with masticatory function, has a regional influence on duration of S phase, mitotic rate, and percentage of cells in the S phase. These results help define an in vivo experimental model for assessing the PDL cellular response to biomechanically defined force systems. Clinical implications are discussed.

Animals↗

PubMed1977

Vascular responses in the human periodontal ligament and alveolar bone detected by photoelectric plethysmography: the effect of force application to the tooth.

A modification of the technique of photoelectric plethysmography has been developed to monitor changes in the microcirculation of the human periodontal ligament and adjacent alveolar bone, whereby detection is made of light reflected from or transmitted through a tissue during alterations in blood volume, flow or distribution. Light is conducted to and from the periodontal tissues via miniature fiberoptics placed within the root canals of endodontically treated teeth, or illuminated through the external surface of the gingiva towards the root. Circulatory activity was monitored both with the teeth at rest and under forces up to 480 gm. Horizontal and axial forces were found to produce a decrease in blood volume in the area of the periodontal tissue under compression. In an area under tension, an initial increase in blood volume was followed by a decrease as the magnitude of force rose above the critical 90 to 180 gm level. The pulse volume, however, was increased during both phases. Analysis of the biphasic and pulse volume changes suggests that autoregulation of blood vessel tone occurs in the periodontal tissues as a result of alteration in extravascular tissue pressure when the root is moved relative to the alveolus. It is proposed that this autoregulatory mechanism may play a role in alveolar bone metabolism by producing alteration in local tissue oxygen tension.

Adult↗

PubMed1979

In vitro phagocytosis of exogenous collagen by fibroblasts from the periodontal ligament: an electron microscopic study.

There have been numerous electron microscopic reports of apparent phagocytosis of collagen by fibroblasts and other cells in vivo. We have developed an in vitro system which, to the best of our knowledge, will permit for the first time the study of regulatory mechanisms governing phagocytosis and digestion of collagen fibres. Cells were cultured from explants of monkey periodontal ligament, subcultured, and grown to confluence in alpha-MEM plus 15% fetal calf serum plus antibiotics. The confluent cells were then cultured together with minced rat tail tendon collagen in alpha-MEM lacking proline, lysine, glycine and fetal calf serum for up to 7 days, after which they were processed for electron microscopy. Intracellular collagen profiles could be seen in cultured cells that were associated with exogenous collagen fibrils as early as 24 hours after addition of the collagen. Through electron microscopic examination of serial sections of the culture, we have demonstrated: (1) that fibroblasts can phagocytose collagen; (2) that the observed intracellular collagen is not the result of aggregation of endogenous synthesized collagen; (3) that it is not possible to base a decision as to whether a collagen fibril has been phagocytosed in whole or in part by the type of vesicle with which it is associated; (4) that cleavage of collagen into small pieces may not be a necessary prelude to its phagocytosis.

Animals↗

PubMed1977

Dimension discrimination at two different degrees of mouth opening and the effect of anaesthesia applied to the periodontal ligaments.

The dimension discrimination ability of twenty-five young persons was tested at two different degrees of mouth opening. One reference stick of 10-0 mm and another of 45-0 mm was placed between the teeth, alternating with test sticks of different heights. The subjects were asked to assess whether a test stick felt higher or lower than the reference stick. The experiment was performed with and without anaesthesia applied to the periodontal ligaments. Anaesthesia did not impair the discrimination ability. At dimensions in the region of the 10-0 mm stick the incorrect assessments occurred predominantly among sticks higher than the reference stick. Around the 45-0 mm stick incorrect assessments were distributed evenly between dimensions higher or lower than the reference stick.

Adult↗

PubMed1979

Cell production in the normal and lathyrogenic rat periodontal ligament (PDL).

Thirty male albino rats weighing 200 g. each were separated into two groups. 15 rats received 0.2% 3-amino propionitrile fumarate (BAPN) in drinking water. 15 rats served as controls. Within three weeks eruption rate diminished by 50%. On the 22nd experimental day each rat received one dose of 1 microCi/g. body weight tritiated thymidine (1.9 Ci/mM). 5 rats of each group were then killed after 1 hour; 1 week and 2 weeks. The PDL cell migration rate was evaluated autoradiographically. It diminishes proportionally with the eruption rate. In the BAPN treated animals, the mean total periodontal ligament (PDL) cell count is 55.5% higher than that of the control.

Aminopropionitrile↗