Roots Of Human Teeth Research Articles

Microbial caries induction in the roots of human teeth in vitro

Streptococcus mutans GS5, Lactobacillus casei DSM20011 and Actinomyces viscosus T14 produce artificial caries in the roots of extracted teeth. Roots were coated with wax leaving an 8 mm 2 window exposed on the buccal surfaces, and then incubated for 8 days in the presence of the test organism, the synthetic medium being changed each day. Samples were then examined by SEM, or microradiographs were obtained from 120 μm sections. The pH at the root surface at the end of the induction averaged 4.43, 5.00 and 5.20, and the lesion depths measured on the microradiographs averaged 121, 83 and 34 μm, for Strep. mutons, L. casei and A. viscosus respectively. This relationship between pH and lesion depth confirms earlier findings. As all of these organisms can produce lesions in tooth structure, elimination of one type would probably not eliminate caries.

Human dentin matrix induces cartilage formation in vitro by mesenchymal cells derived from embryonic muscle.

Dentin matrix was assayed for its potential to elicit chondrogenesis of mesenchymal cells in vitro. The substratum was prepared by demineralization of human tooth root dentin, while embryonic thigh muscle was used as a source of mesenchymal cells. Formation of chondrocytes from mesenchymal cells occurred in the presence of dentin matrix, and in the same sequence as previously shown with substrata of demineralized bone.

The mineral solubility of human tooth roots

Whole roots of molars that had never been exposed to the mouth were exposed to calcium and phosphate-containing buffer solutions with discrete values of pI OHA [i.e. −log( a Ca 2− 10 · a PO 4 3− 6· a OH− 2)] at various pH. From densitometric measurements on contact-microradiographs of transverse sections of the roots the rate of demineralization ( V dcm) was calculated. V dem changed non-linearly as a function of pI OHA and became zero at a pI OHA-value of 105.3 ± 0.4; this is substantially lower than the corresponding value of 118 ± 1 for enamel. Thus root mineral is more soluble than enamel mineral. The critical pH for root caries appears to be about 6.7, provided that the plaque fluid follows about the same pH-pI OHA− pathway as acidified saliva.

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.

Influence on pH level of two calcium hydroxide root canal sealers in vitro

The pH level of saline solutions was determined 1 hour, 4 hours, 1 day, 2 days, 3 days, and 1 week after roots of human teeth, which had received one of four root canal treatments, were placed in them. The four treatments following instrumentation were filling of canals with laterally condensed gutta-percha and either Sealapex (10), calciobiotic root canal sealer (CRCS) (10), or a Grossman type sealer (10), and filling of only the coronal 2 to 3 mm of canals with Cavit (unfilled, 10). The coronal 2 to 3 mm of all canals in all groups were filled with Cavit. The pH levels of the four solutions were compared to each other and to that of saline solution only. The pH levels of the solutions in the Sealapex group were higher than those of all the other solutions for each of the six times (p < .01). Although the pH levels of the solutions in the CRCS group were significantly lower than those of the Sealapex group, they were higher than those of the other solutions at 1 hour and at 4 hours (p < .01). After that there were no significant differences in the level of pH for the CRCS, Grossman, unfilled, or saline-solution-only groups, except that at 3 days and at 1 week the pH levels of the unfilled group were significantly lower than those of all other groups.

Cell and fiber attachment to demineralized dentin from periodontitis-affected root surfaces.

This study assessed connective tissue and epithelial responses to dentin specimens obtained from periodontitis-affected roots of human teeth after surface demineralization. Rectangular dentin specimens with opposite faces of root and pulpal dentin were prepared from beneath root surfaces covered by sheets of calculus. One half of the specimens were treated with citric acid, pH 1, for 3 minutes, while the remainder served as untreated controls. Specimens were implanted vertically into incisional wounds on the dorsal surface of rats with one end of the implant protruding through the skin. Four specimens in each group were available 1, 3, 5 and 10 days after implantation. Histologic and histometric analyses included counts of adhering cells, evaluation of attached connective tissue fiber density and diameter, and assessment of epithelial migration. Analyses within each group comparing root and pulpal surfaces showed no differences between any of the parameters. Comparisons between experimental and control groups showed that demineralized surfaces had a greater number of cells attached, fiber attachment occurred and epithelial downgrowth was inhibited. Surface demineralization of dentin from periodontitis-affected roots predisposed toward a connective tissue attachment.

Cell and fiber attachment to demineralized dentin from normal root surfaces.

The study assessed connective tissue and epithelial responses to dentin specimens (obtained from normal roots of human teeth) after surface demineralization. Rectangular dental specimens with opposite faces of root and pulpal dentin were prepared from beneath root surfaces covered by periodontal ligament. One-half of the specimens were treated with citric acid, pH 1, for 3 minutes, while the remainder served as untreated control specimens. Specimens were implanted vertically into incisional wounds on the dorsal surface of rats with one end of the implant protruding through the skin. Four specimens in each group were available 1, 3, 5 and 10 days after implantation. Histologic and histometric analyses included counts of adhering cells, evaluation of connective tissue fiber relationships and assessment of epithelial migration. Analyses within each group comparing root and pulpal surfaces showed no differences between any of the parameters. Comparisons between experimental and control groups showed that demineralized surfaces had a greater number of cells attached, fiber attachment occurred and epithelial downgrowth was inhibited. The fiber attachment to experimental specimens differed morphologically from fiber attachment to normal root surfaces: the number of fibers attached per unit length and the diameter of attached fibers were significantly less on experimental specimens. Demineralized specimens at 10 days had a distinct eosinophilic surface zone. Surface demineralization of dentin predisposed toward a cell and fiber attachment system which inhibited migration of epithelium.

Fluorine concentration changes in human periodontally diseased tooth roots following several treatment times with citric acid.

Citric acid conditioning of exposed cementum has become an important adjunct to the clinical management of periodontal disease, and aggressive root planing is recommended to remove hypermineralized and endotoxin-laden diseased cementum. A nuclear resonance reaction technique was used to examine fluorine concentration changes subsequent to application of citric acid (pH 1.0) to the periodontal disease-exposed cementum surfaces of human tooth roots. The technique does not require the test teeth to be sectioned, thereby permitting longitudinal assessments of changes in fluorine concentration and minimizing measurement errors due to the considerable biological variation found between individuals. Initial fluorine concentrations ranged from 0.9%-2.4%, and maxima occurred within 4-6 microns of the surface, suggesting the presence of a hypermineralized layer. Within 60 sec, the citric acid had effectively removed the hypermineralized layer and the previously observed fluctuations in fluorine concentration leveled out at 0.3%-0.5%. Although the results indicated rapid removal of the hypermineralized layer and establishment of fluorine levels normally found in healthy cementum, the experimental design did not permit appraisal of potential effects upon the organic components of periodontally-exposed cementum.

Deposition of corrosion products from dowels on human dental root surfaces measured with proton microprobe technique

Distribution of copper, mercury and zinc on human teeth root surfaces adjacent to dowels of gold alloy or brass as well as dowels of brass in conjunction with an amalgam crown has been measured with a proton microprobe using PIXE techniques. Upper limits of the contents of gold and silver on the root surfaces were established. Pronounced concentration profiles of copper and zinc were observed on the root surfaces of teeth prepared with dowels of brass. The dowel of gold alloy revealed only zinc deposition. The major part of copper on the root surfaces is assumed to arise from corrosion of the dowels, and has been transported to the surface by diffusion through the dential tubuli. Zinc in the volume analysed is a constituent of dentin tissue as well as a corrosion product of the brass dowel. Part of the zinc level could also be ascribed to erosion of the zinc phosphate cement matrix. The volumes analysed were (25×25×25)μm 3. The levels of copper, mercury and zinc on the tooth root surfaces attained values up to about 200, 20 and 600 ppm, respectively.

Variation in the Area of Intraperiodontal Surfaces of Human Tooth Roots, in Relation to Their Depth: Thesis—Paris 1970

Variation in the Area of Intraperiodontal Surfaces of Human Tooth Roots, in Relation to Their Depth: Thesis—Paris 1970

Scanning electron microscopic examination of root after apicoectomy.

The scanning electron microscope was used to examine resected areas of eight roots of human teeth extracted after long intervals following surgical procedures. Some resorption lacunae were observed in the areas with protuberances of newly formed cementum. In the lacunae, honeycomb-like structures were found. On the resected surface, residues of ligaments and periodontal fibers, and in one of the specimens dentinal tubules with odontoblastic processes protruding above the surface were present.

Aging of tissues of the roots of nonfunctional human teeth (impacted canines)

In order to examine the aging of dentin and cementum, seventy-two impacted human canines, nonfunctional and not affected by external factors, such as attrition, abrasion, caries, etc., were surgically extracted. Ground sections were prepared and the areas of sclerotic dentin and cementum were measured with the aid of a planimeter and expressed as a percentage of the total root area. It was found that there is a significant increase in sclerotic dentin and apposition of cementum with an increase in age.

Mineralization in the roots of human deciduous teeth demonstrated by tetracycline labelling

The pattern of tetracycline labelling was investigated on ground sections of the roots of deciduous teeth. All bands were continuous across the granular layer of Tomes where they turned coronally. Underlying acellular cementum, the bands appeared to merge with the hyaline layer of Hopewell-Smith. In regions where cellular cementum was present, the bands ran through areas identifiable as cellular and intermediate cementum. Previously ( owens, 1972) the band pattern in the coronal region was interpreted as indicative of mineralization in an initially unmineralized surface zone of root dentine. However, a similar interpretation in relation to cellular cementum was not possible and could not be reconciled easily with conventional views of cementogenesis. An alternative hypothesis was therefore postulated, suggesting that, during formation, the surface of dentine may become modified to resemble cellular and intermediate cementum.

Contribution to the ontogenetic morphology of roots of human teeth.

Contribution to the ontogenetic morphology of roots of human teeth.

Electron microscopy of human developing dentine

The early stages of dentinogenesis have been studied in the electron microscope by examination of sections from growing roots of human premolar teeth. The appearances of the epithelial root sheath, the undifferentiated tissue of the dentine papilla and the separating membrane are described. The relative insignificance of von Korff's fibres is noted and recent observations on this subject are reviewed. The different appearances of the odontoblast cell before, during and after function are compared and the significance of these changes is discussed.