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At least 199 records · Page 11Linked to original sources
PubMed1984

Possible mechanisms of induction of dentinogenesis.

The following hypothesis is proposed: The inner enamel epithelium influences all cells of the dental papilla very early during embryologic development--long before any morphologic changes due to histo-differentiation are noticeable. During normal odontogenesis, the epithelium acts as a second order inducer for the differentiation of odontoblasts and their subsequent production of dentin. Other mechanisms exist which can induce responding fibroblasts of the dental pulp to produce dentin or dentin-like tissue. Collagen matrix can act as such an inducer.

Animals↗
PubMed2005

A quantum biological hypothesis of human secondary dentinogenesis.

It is hypothesized that human coronal secondary dentin (SD) is a final classical mechanical (CM) response to a chain of prior quantum mechanical (QM) transductions of the information of initial CM occlusal loadings of enamel. Such CM energy is transduced into QM quanta (as protons) that are translocated centripetally via clustered water (CW), (as "proton wires"), that is structurally related to both enamel prism sheath and hydroxyapatite crystal hydration shells. These quanta pass into odontoblastic cell processes (OP), lying within dentinal tubules (DT). OP's contain abundant parallel arrays of cylindrical microtubules (MT). These are the sites of two further CW-related QM events: (i) proton translocation associated with conformal changes of MT tubulin protein dimers; and (ii) coherent energetic oscillations within the CW filling the MT's hollow cores. Finally, these quanta pass into the odontoblastic soma, where QM wave function collapse transduces this information into a final CM state that initiates the processes of SD formation. A critical portion of this hypothesis may be experimentally tested.

Dentin, Secondary↗
PubMedDate not supplied

Effect of ascorbic acid deficiency on primary and reparative dentinogenesis in non-ascorbate-synthesizing ODS rats.

Ascorbic acid is essential to the biosynthesis of collagen, the major organic matrix component of dentine. The ODS rat is a mutant strain of Wistar rat characterized by hereditary lack of L-gulono-gamma-lactone oxidase and thus is unable to synthesize ascorbic acid. ODS rats were given an ascorbic acid-free diet to investigate how ascorbic acid deficiency affects dentine formation in vivo. Histomorphometric analysis on their growing molars and incisors showed a significant reduction in both size and mineral apposition rate of dentine, as revealed by contact microradiography and fluorescent time-marking, respectively. A similar reduction in bone formation was simultaneously demonstrated in the mandible, confirming the previously reported osteopathic effects of ascorbic acid deficiency. When pulp inflammation was induced in lower first molars by making unsealed pulp exposures, specimens from control animals showed continuous deposition of an osteodentine-like tissue in the radicular pulp chamber; this type of mineralized tissue formation was greatly reduced in ascorbic acid-deprived animals. These results indicate that ascorbic acid deficiency hampers dentine formation under both physiological and pathological conditions of the dentine/pulp complex. ODS rats could be useful in investigating in vivo effects of ascorbic acid deficiency on the formation of dentine and other dental mineralized tissues.

Animals↗
PubMed1990

The effect of adriamycin on dentinogenesis and 3H-thymidine incorporation into the enamel organ of the rat incisor.

The effect of adriamycin (5 mg/kg) on 3H-thymidine incorporation and on dentin formation was studied in rat incisors. Male Sprague Dawley rats received an intravenous injection of adriamycin. Some of these also received a subcutaneous injection of 3H-thymidine at a dose of 2 mCi/kg one day later. One group of control animals received an intravenous injection of a volume of physiological saline equal to that of the adriamycin dose. Another group received physiological saline, and one hour later was given an additional injection of 3H-thymidine at a similar dose as above. All the animals were killed by perfusion with 2.5% phosphate buffered glutaraldehyde 1 h, 1 d, 4 d, 8 d, 16 d, 28 d, and 32 d after 3H-thymidine treatment. Light microscopy revealed irregular dentin deposits between the mantle and circumpulpal layer of the labial dentin at 16 d. Within these deposits were trapped cells. The latter, through radioautographic labelling, appeared to be cells from the odontoblast layer. Also, the labelling pattern of the enamel organ in both the control and experimental groups indicated that the eruption rate of the tooth was not affected. Serial sectioning and examination of the lingual portion of the incisors at 28 d revealed a lack of dentin formation and a failure in the closure of the apical foramen. Electron microscopic observations showed an irregular and random arrangement of collagen fibers within the deposits of irregular dentin, and the presence of twisted odontoblastic processes. Examination of the lingual surface showed the presence of fibroblasts and collagen fibers bridging the gap that resulted from the failure in dentin formation. These cells, which were similar to periodontal ligament cells, appeared to have arisen from that area. These results indicate that adriamycin has no effect on tooth eruption, but has a reversible effect on the function of secretory odontoblasts, which manifested itself as a periodic deposition of irregular dentin on the labial surface, and on dentin formation on the lingual surface which manifested itself as a failure in dentin formation, and consequently, the closure of the apical foramen.

Animals↗
PubMed1985

Aberrations in pulpal histology and dentinogenesis in transplanted erupting teeth.

Responses of pulpal tissues were assessed histologically in teeth that had been transplanted after root formation was moderately well advanced. Degeneration occurred in the coronal third, but the area was repopulated by cells proliferating from the center of the pulp. Apically, the tissues, including the odontoblasts, remained vital and functional. Widespread intrapulpal formation of osteodentin was prominent in later observation periods. Apical closure occurred prematurely by production of osteodentin and cellular cementum in the form of an apical diaphragm; these mineralized tissues were confluent with a similarly active deposition of cellular cementum apically on the root surface.

Animals↗