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PubMed1990

Calcification capacity of dental papilla mesenchymal cells transplanted in the isogenic mouse spleen.

The capacity of the dental pulp to form calcified tissue was examined in papilla cells dissociated from first molar tooth germs of the neonatal mouse and isografted in the spleen for up to 7 days. To obtain papilla cell populations without odontoblasts, pulpal mesenchyme was isolated mechanically from the enamel organ after 0.1% trypsin treatment and rolled on a membrane filter. On day 3 after transplantation, the grafted papilla cells had changed into large, spindle-shaped cells, and initial calcification with needle-like crystals began in association with the collagenous matrix surrounding those cells. On day 7 after transplantation, the spindle cells transformed into odontoblast-like cells containing well-developed secretory organelles, and irregular, but nontubular, calcified tissues were commonly observed surrounding the extracellular collagenous matrix. The calcified tissue matrix with cellular inclusions displayed a structure similar to that of osteodentin. During this period, an intense positive reaction for alkaline phosphatase (ALPase) activity was demonstrated along the cell membranes of the odontoblast-like cells aligned at the periphery of forming calcified tissue. Enzymatic activity could not be detected on the cells incorporated completely into osteodentin-like matrix. The present results show that the papilla cell population transplanted into the spleen formed osteodentin-like material, thus demonstrating the capacity of papilla cells to produce calcified tissue.

Alkaline Phosphatase↗
PubMed1999

Dental anomalies associated with amelogenesis imperfecta: a radiographic assessment.

Amelogenesis imperfecta, a group of hereditary conditions primarily affecting the enamel, has been associated with dental anomalies, including taurodontism, congenitally missing teeth, delayed eruption, crown resorption, and abnormal enamel density. The purpose of this study was to assess the prevalence of these anomalies in an amelogenesis imperfecta population. The study group consisted of members of 9 unrelated families--22 family members with amelogenesis imperfecta and 13 unaffected family members. Panoramic radiographs were evaluated for taurodontism, congenitally missing teeth, delayed tooth eruption, pathologic dental resorption, pulp calcification, and radiographic enamel density. The prevalence of taurodontism was similar in people with amelogenesis imperfecta and normal people; all of the remaining parameters were more commonly observed in people with amelogenesis imperfecta. The radiographic enamel density was quantitatively reduced in teeth affected by amelogenesis imperfecta in comparison with teeth with normal enamel. These findings suggest that some of the features associated with amelogenesis imperfecta result from abnormal enamel formation (eg, decreased enamel density, crown resorption) whereas others may occur as a result of expression of the genetic mutation in cells other than ameloblasts (eg, abnormal eruption, pulp calcification).

Adolescent↗
PubMed1996

Longitudinal study of dental development in chimpanzees of known chronological age: implications for understanding the age at death of Plio-Pleistocene hominids.

Reconstruction of life history variables of fossil hominids on the basis of dental development requires understanding of and comparison with the pattern and timing of dental development among both living humans and pongids. Whether dental development among living apes or humans provides a better model for comparison with that of Plio-Pleistocene hominids of the genus Australopithecus remains a contentious point. This paper presents new data on chimpanzees documenting developmental differences in the dentitions of modern humans and apes and discusses their significance in light of recent controversies over the human or pongid nature of australopithecine dental development. Longitudinal analysis of 299 lateral head radiographs from 33 lab-reared chimpanzees (Pan troglodytes) of known chronological age allows estimation of means and standard deviations for the age at first appearance of 8 developmental stages in the mandibular molar dentition. Results are compared with published studies of dental development among apes and with published standards for humans. Chimpanzees are distinctly different from humans in two important aspects of dental development. Relative to humans, chimpanzees show advanced molar development vis a vis anterior tooth development, and chimpanzees are characterized by temporal overlap in the calcification of adjacent molar crowns, while humans show moderate to long temporal gaps between the calcification of adjacent molar crowns. In combination with recent work on enamel incremental markers and CAT scans of developing dentitions of Plio-Pleistocene hominids, this evidence supports an interpretation of a rapid, essentially "apelike" ontogeny among australopithecines.

Aging↗
PubMed2003

Unusual manifestations in X-linked amelogenesis imperfecta.

This paper describes a female with X-linked amelogenesis imperfecta (XAI). This case is unusual in having taurodontism, pulpal calcifications, coronal defects prior to tooth eruption and unerupted teeth. These findings have been reported in some cases of autosomal dominant and autosomal recessive AI but have not previously been documented in XAI.

Adolescent↗
PubMed2005

Review: extracellular matrix regulates tooth morphogenesis.

Mineralized tissues are unique in that they use proteins to attract and organize calcium and phosphate ions into a structured mineral phase, thus precise knowledge of the expression and extracellular distribution of matrix proteins is very important to understand their function. Tooth development is regulated by sequential and reciprocal interactions between neural crest-derived mesenchymal cells and the oral environment. However, the precise molecular mechanisms that mediate interactions between epithelium and mesenchymal cells are not clear, although basement membrane (BM) components have been shown to play important roles in these regulatory events. In addition, the extracellular matrix layer, whose main components are laminin, collagen IV, nidogen, and sulfated proteoglycan, and the BM layer are both considered to be involved with cell proliferation and differentiation. During tooth morphogenesis, extracellular matrices are dramatically changed. Further, the BM components, laminin and collagen IV support dental epithelium; however, in the late stage, they begin the processes of enamel matrix secretion and calcification, after which the BM structure between the dental epithelium and mesenchyme disappears. In addition, tooth abnormalities associated with several kinds of human diseases that cause mutations in the extracellular matrix, as well as the molecular mechanisms of the basement membrane and enamel matrix during tooth morphogenesis, are not clearly understood. In our review, we discuss the role of the extracellular matrix, with focus on the BM and enamel matrix during tooth morphogenesis.

Ameloblasts↗
PubMed1991

Short-term mineralization of dentin and enamel in the mouse embryonic molars cultured in serum-free, chemically-defined medium.

The present study was designed to demonstrate the short term mineralization of dentin and enamel, and to investigate the effects of sodium beta-glycerophosphate (Na-beta-GPO4) on calcification in a serum-free, chemically-defined medium. The first mandibular molars at the bell stage dissected from 18-day-old mouse embryos were used as explants, which were cultured by an improved flotation method. Calcification of enamel in the 18-day-old embryonic molars occurred within the 6th day of culture. In another experiment, the molar germs were cultured in a serum-free, chemically-defined medium supplemented with 1, 5 and 10 mM Na-beta-GPO4. Promotion of tooth mineralization was recognizable at very low concentrations, such as 1 mM Na-beta-GPO4, in 18-day-old embryonic tooth germs. The culturing system reported here shortens the time required for dentin and enamel calcification to one half or one third of that reported previously and therefore should prove useful for examining regulations for cytodifferentiation and morphogenesis in tooth germs and the mineralization of dentin and enamel.

Ameloblasts↗
PubMed1985

Ultrastructural distribution of acidic glycosaminoglycans associated with matrix vesicle-mediated calcification in mouse progenitor predentine.

The ultrastructural localization of acidic glycosaminoglycans, presumed to be proteoglycans, was examined during initial matrix vesicle-mediated calcification in dentine, by using ruthenium red (RR) staining, high iron diamine thiocarbohydrazide silver proteinate (HID-TCH-SP) staining, and an enzymatic digestion method. Progenitor predentine 2-10 micron width of developing mouse molar tooth germs was used throughout the present study. The outer surface membrane of the intact matrix vesicles had a strong affinity for RR. The RR positive materials appeared beaded and extended perpendicularly from the vesicle membrane. They tended to disappear with the disruption of the vesicular membrane, which resulted from overextension due to needle-like, crystal-like structures. The HID-TCH-SP stain deposits, approximately 10 nm in diameter, were densely distributed around the intact matrix vesicles, though few were found inside them. Some matrix vesicles that were presumably disrupted, however, contained smaller stain deposits. On the outer surface membrane of the disrupted vesicles, HID-TCH-SP stain deposits were fewer in number. The results obtained from enzymatic degradation studies showed that the anionic materials on the outer surface membrane of the matrix vesicles were represented by chondroitin-4-sulfate and/or chondroitin-6-sulfate. We suggest that chondroitin sulfates attached to the outer leaflet of the vesicular membrane play an important role during the incipient stage of the matrix vesicle-mediated calcification process.

Animals↗
PubMed1989

[Fine structure of the root resorption of human deciduous tooth].

During growth and development of the gnathic bone in infants, it is not possible to observe the processes of resorption of the bone and deciduous tooth root, bone formation and calcification of the permanent teeth separately. In the gnathic bone of infants where a normal balance exists between formation of new tissue and resorption, the formative bone tissue is closely related to the cells which give rise to the deciduous and the permanent teeth. We used a scanning electron microscope to observe the fine structure of the root resorption of the deciduous teeth, using root deciduous teeth extracted from humans. Large and small plate-shaped absorbed fossula were found together with projecting dentinal fiber tubuli in the dentinal resorption cavity of the deciduous tooth root. Odontoclasts with a round form supported and covered by fibrous connective tissue were also observed. Furthermore, when the fibrous tissue was removed washed out, an arrangement of calcified collagen fibers (similar to stromal tissue) was found in the cavity. On the absorbed cementum surface a plate-like resorption cavity had formed. The surface was covered by fibrous connective tissue with a regular pattern. The round and oval odontoclasts were surrounded by thick vascular-like connective tissue. High levels of P and Ca were found in the dentinal absorption cavity by X-ray analysis and Al, Mg, Na and Zn were also found. S, P, Ca and Zn were found in the odontoclasts Ca, P, Mg, Na and Zn were found in the cementum resorption cavity.

Humans↗
PubMed1990

[A clinical study of traumatic injuries to deciduous teeth. (3). The influence on their permanent successors].

To study the influence of traumatic injuries to deciduous teeth on their permanent successors, we investigated 126 traumatized deciduous incisors of 66 children who had visited our clinic regularly after traumatic injuries, and whose permanent successors had erupted. The results are summarized as follows. 1) Some developmental disturbances on permanent successors, such as concerning their eruption, or crowns, roots and pulp, were found in 72 teeth. Among these, influences on crown formation and calcification were most often found, and white discoloration in the enamel was recorded in 55 teeth, yellow discoloration in 4 teeth and hypoplasia in 11 teeth. 2) One successor erupted one and a half years after the eruption of its opposite, and two teeth erupted in torsiversion. Three successors had root angulation, while arrest of root formation was found in one tooth. Pulp canal obliteration appeared in two teeth before their eruption. 3) Developmental disturbances of the crowns tended to be more severe and had a higher ratio when traumatic injuries occurred at a younger age. The range of the ages of the children at the time of injury was limited in cases of hypoplasia and yellow discoloration. 4) According to the diagnoses at the first visit, the severity of periodontal injury and the dislocational directions of deciduous incisors might relate to the disturbances of crown formation and calcification of successors. 5) According to the type of treatment, enamel hypoplasia was observed more frequently in the observation group and the extraction group. Yellow and relatively large white discolorations were found more frequently in the reposition group than in the fixation group. 6) In the endodontic therapy group, only relatively small white discolorations were found, but white discoloration was observed more frequently in the extraction after endodontic therapy group than in the extraction without endodontic therapy group after first visit. 7) White discoloration in the enamel was most often located in the both upper and lower teeth at the incisal third position on the labial surface.

Child↗
PubMed1979

The relationship between tooth mineralization and early radiographic evidence of the ulnar sesamoid.

The relationship between early radiographic evidence of calcification of the adductor sesamoid of the first metacarpophalangeal joint and the state of maturity of certain teeth was investigated. Data were obtained from the records of one hundred and forty children of Caucasoid origin, comprising ninety-three girls and forty-seven boys. Calcification of the adductor sesamoid was closely related to the completion of root mineralization of the mandibular canine prior to apical closure. No significant sex differences were noted in the state of maturation of the tooth in relation to this particular stage of skeletal development. Correlations among the remaining teeth studied were low, the distribution of calcification stages being widely dispersed with significant sex differences evident. Based on the findings of this study, the completion of root formation of the mandibular canine prior to apical closure may be used as a maturity indicator for the commencement of the circumpubertal growth spurt with a similar degree of confidence as the calcification of the adductor sesamoid of the thumb. It should be noted, however, that racial variations might exist in the relationship between the state of maturity of this tooth and the commencement of mineralization of the sesamoid. Caution should thus be exercised in the application of these findings to other racial groups.

Calcification, Physiologic↗
PubMed1995

Amelogenesis imperfecta and nephrocalcinosis syndrome. Case studies of clinical features and ultrastructure of tooth enamel in two siblings.

This article describes the enamel ultrastructure and clinical features in two siblings with the little known syndrome of Amelogenesis imperfecta and nephrocalcinosis. Nephrocalcinosis was diagnosed by x-ray examination of the abdomen, intravenous pyelography, ultrasonography, and computed tomography scan. Amelogenesis imperfecta was diagnosed from clinical and histologic examinations. The affected enamel was hypoplastic (approximately 0.2 mm thick), positively birefringent, generally aprismatic, porous, and consisted of loosely packed, randomly orientated, thin (approximately 10 nm wide), ribbonlike crystals. The enamel surface was rough, extensively cracked, and covered with ovoid or globular protrusions. Observations showed that in this case hypoplasia, hypocalcification, or hypomaturation defects were present in the same tooth, indicating that both secretory and maturation phases may have been affected. The study suggested the possibility of an abnormality in interstitial matrix, which could lead to dystrophic calcification in the kidney and abnormal tooth enamel formation. It also suggested the possibility of involvement of two separate but closely linked genes.

Adolescent↗
PubMed2001

Bur extensor for root canal access.

Access to a tooth with a partial canal calcification was made. The access was possible only with a bur extensor connected to a LN bur. Calcification was bypassed, and the canal was completely prepared.

Adult↗