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PubMed2003

Craniofacial morphology and dental age in children with Silver-Russell syndrome.

OBJECTIVES: This investigation is a part of a multidisciplinary descriptive evaluation of the Silver-Russell syndrome (SRS). The aim of this study was to describe the craniofacial morphology, occlusion and dental age in children with the SRS. DESIGN: A descriptive literature-controlled study. SETTING AND SAMPLE POPULATION: Sixteen children diagnosed as having SRS, 10 boys and six girls, aged 4.4-14.5 years, were referred from different parts of Sweden to the Queen Silvia Children's Hospital, Göteborg University. EXPERIMENTAL VARIABLE: Facial morphology was measured on lateral and postero-anterior radiographs. Occlusion, tooth eruption and palatal height were measured on casts, and dental maturity was evaluated on orthopantomograms. OUTCOME MEASURE: Linear and angular measurements were obtained from lateral radiographs and the ratios of the linear measurements from the postero-anterior radiographs. The degree of tooth calcification shown on orthopantomograms was taken as a measure of dental maturity. Biometric measurements were taken and the degree of tooth eruption was recorded from the dental casts. The SRS children were compared with reference groups with t-test and z-scores. RESULTS: Overall, SRS children were found to have smaller linear facial dimensions and deviations in the facial proportions, such as a small retropositioned, and steeply inclined maxilla and mandible, and a proportionally larger anterior facial height in relation to the posterior facial height. In 40% of them a smaller facial height or length on one side (facial asymmetry) was correlated to the smaller side of the body. The frequency of malocclusions was higher, and the palatal height showed a tendency towards an increase. Dental maturity was within normal limits, while the time of tooth eruption was slightly delayed. CONCLUSIONS: The deviating facial morphology described above is a part of the syndrome, which is characterized by short stature, growth hormone deficiency and asymmetries of the body. The higher percentage of malocclusions in the SRS children might lead to a greater need of orthodontic treatment.

Abnormalities, Multiple↗
PubMed2004

Relationships between dental and skeletal maturity in Turkish subjects.

The aim of this study was to investigate the relationships between the stages of calcification of various teeth and skeletal maturity stages among Turkish subjects. The samples were derived from dental panoramic and hand-wrist radiographs of 500 subjects (215 males and 285 females). Calcification of the mandibular canines, first and second premolars, and second and third molars was rated according to the system of Demirjian. To evaluate the stage of skeletal maturation of each hand-wrist radiograph, nine ossification events were determined according to the systems of Björk, and Grave and Brown. Statistically significant relationships were determined between dental calcification and skeletal maturity stages according to Spearman rank-order correlation coefficients. Correlations between dental development and skeletal maturity ranged from .490 to 0.826 for females and .414 to .706 for males (P < .01). The second molar showed the highest correlation and the third molar showed the lowest correlation for female and male subjects. For both sexes, root formation of the canine as well as the first premolar was completed in the majority of the subjects at the MP3cap, PP1cap, Rcap stages. Because of the high correlation coefficients, this study suggests that tooth calcification stages from panoramic radiographs might be clinically useful as a maturity indicator of the pubertal growth period. It is appropriate to put these skeletal and dental maturation relationships into daily orthodontic diagnostic practice, when treating a Turkish patient.

Adolescent↗
PubMed1996

Recent observations on enamel crystal formation during mammalian amelogenesis.

BACKGROUND: Enamel mineralization taking place during amelogenesis is a unique model to investigate carbonatoapatite formation in vivo. The abundance of proteinaceous crystal growth inhibitors, in particular amelogenins, contributes significantly to the mineralization process. Their putative roles are to prevent random proliferation of crystal nuclei and to regulate the growth kinetics and orientation of the formed enamel crystals. METHODS: The enamel fluid surrounding the forming enamel crystals contains high concentrations of carbonate and magnesium ions, both of which seem to modulate the mineralization process. Particularly, Mg ions can adsorb onto enamel crystal surfaces in a manner to compete with Ca ions. Enamel mineral formed during amelogenesis is featured as calcium-deficient, acid phosphate-rich carbonatoapatites. Currently the most putative stoichiometry model for enamel mineral is (Ca)5-x(HPO4)v(CO3)w(PO4)3-x (OH)1-x. RESULTS: Very significant changes in the morphology, stoichiometry, and solubility of enamel crystals occur during the various stages of amelogenesis. The early enamel mineralization comprises two events: the initial precipitation of the well-documented thin ribbons and the subsequent overgrowth of apatite crystals on those templates. The thin ribbons precipitated in the vicinity of the secretory ameloblasts have the highest contents of acid phosphate, particularly in the form of exchangeable species, whereas both the exchangeable and unexchangeable acid phosphate decrease concomitantly with the progress of the apatite overgrowth and the appearance of elongated hexagonal crystals in the late secretory stages. CONCLUSIONS: Those morphological and compositional features seem to be consistent with the formation of precursors, such as octacalcium phosphate.

Amelogenesis↗
PubMed1996

Cementogenesis reviewed: a comparison between human premolars and rodent molars.

BACKGROUND: Cementum continues to be the least-known mineralized tissue. Although recent advances in the field of molecular biology have contributed to an understanding of the involvement of molecular factors in cementum formation during development and regeneration, cementogenesis on a cell biological basis is still poorly understood. Virtually nothing is known about cementoblast origin, differentiation, and the cell dynamics during normal development, repair, and regeneration. This review describes the recent findings of cementogenesis on roots of human premolars and opposes them to those of teeth from other mammals, particularly the rodent molar. METHODS: Using light and electron microscopy, light microscopic radioautography, and various measurements, a comprehensive insight into the development and repair of cementum during and after root formation and tooth eruption has been achieved for human premolars. RESULTS: Cementum is a highly responsive mineralized tissue. This biological activity is necessary for root integrity and for bringing and maintaining the tooth in its proper position. With regard to cementum formation and periodontal fiber attachment, considerable species-particularities exist that are mainly based on differences in growth rates and tooth sizes. Since root development and initial cementogenesis last on the average 5-7 years in human premolars, cementum formation in these teeth is characterized by along-lasting phase of prefunctional development, with occurs independent of principal periodontal fiber attachment to the root and which may take 5 years or more. The first molar of the rat, however, is in functional occlusion 3 1/2 weeks after the onset of root formation. Since initial cementum formation and periodontal fiber attachment to the root occur almost at the same time in this tooth, the distinction between cells associated with one or the other process is very difficult to achieve, and cementogenesis cannot be described independent of periodontal fiber attachment to the root. Therefore, the determination of cementoblast origin in the rodent molar may be intricate. CONCLUSIONS: Taking into account these species differences, the current description on the origin and differentiation of cementoblasts is inconsistent and the description of cementogenesis is still incomplete. This review calls into question the currently held concept of cementogenesis and offers a possible alternative.

Animals↗
PubMed1993

Increasing human tooth length between birth and 5.4 years.

Most previous studies of tooth development have used fractional stages of tooth formation to construct growth standards suitable for aging juvenile skeletal material. A simple alternative for determining dental age is to measure tooth length throughout development. In this study, data on tooth length development are presented from 63 individuals of known age at death, between birth and 5.4 years, from an archeological population recovered from the crypt of Christ Church, Spitalfields, London. Isolated developing teeth (304 deciduous, 269 permanent) were measured in millimeters and plotted against individual age. Regression equations to estimate age from a given tooth length, are presented for each deciduous maxillary and mandibular tooth type and for permanent maxillary and mandibular incisors, canines, and first permanent molars. Data on the earliest age of root completion of deciduous teeth and initial mineralization and crown completion of some permanent teeth in this sample are given, as well as the average crown height and total tooth length from a small number of unworn teeth. This method provides an easy, quantitative and objective measure of dental formation appropriate for use by archeologists and anthropologists.

Age Determination by Teeth↗
PubMed1994

Bone sialoprotein is localized to the root surface during cementogenesis.

Bone sialoprotein (BSP), an RGD-containing protein with cell attachment properties, is believed to play a regulatory role in the biomineralization of various connective tissues. To determine its possible role in tooth root formation, murine dentoalveolar tissues at sequential phases of development were analyzed immunohistochemically for the presence of BSP. BSP was localized to alveolar bone and cementum at time points associated with initial mineralization of these tissues. In addition, northern blot analyses of dental follicle tissue at day 27 of tooth development indicated that BSP mRNA is expressed by dental follicle cells at a time point coincident with the initiation of cementogenesis on the peripheral tooth root surface. Collectively, these findings indicate that BSP may play an important role in the formation and mineralization of cementum.

Animals↗
PubMed2002

Caiman periodontium as an intermediate between basal vertebrate ankylosis-type attachment and mammalian "true" periodontium.

The teeth of many fish, amphibia, and reptiles are attached to the alveolar bone via ankylosis. In contrast, mammalian periodontia are characterized by a gomphosis, an attachment of the tooth root in the alveolar bone socket via periodontal ligament fibers. Among the reptiles, the crocodilians are the only group featuring a gomphosis-type connection between tooth root and alveolar bone, while in other reptiles tooth-root and jawbone are connected via ankylosis. The purpose of the present study was to compare several key features of the crocodilian periodontium with those of the mammalian and noncrocodilian reptile periodontium. As experimental models for our study we chose the periodontium of newborn geckos (Hemidacylus turcicus), juvenile caimans (Caiman crocodilus crocodilus), and 10-day-postnatal Swiss-Webster mice (Mus musculus) as representative models for noncrocodilian reptiles, crocodilian reptiles, and mammals. The caiman periodontium emerged as an intermediary between the mineral-free mouse ligament and the mineralized gecko ankylosis-type attachment. Caiman ligament fibers were less organized than mouse ligament fibers but featured distinct fasciae surrounding ligament fiber bundles. Caiman Hertwig's epithelial root sheath (HERS) was similarly perforated as mouse HERS and distinctly different from the continuous gecko HERS. Both caiman and mouse HERS covered the entire tooth root length, while in the gecko HERS was limited to the coronal portion of the root, allowing for cementoid-mediated ankylosis at the apical tip of the root. We interpret our data to indicate distinct differences in mineral distribution, periodontal ligament fiber organization, and HERS distribution between noncrocodilian reptiles, crocodilian reptiles, and mammals. Mineral deposits in the caiman ligament may reflect an evolutionary position of the caiman periodontium between ankylosis and gomphosis.

Alligators and Crocodiles↗
PubMed1979

Structure and formation of ankylosis in Xenopus laevis.

The structure of ankylotic teeth in Xenopus laevis was studied by light, transmission, and scanning electron microscopy as well as by microradiography in decalcified and undecalcified specimens. The mature teeth of Xenopus laevis are calcified from the crown to the base, fused to the jaw bone, and have no uncalcified area, such as a fibrous ring separating the tooth into the crown and pedicle. Microradiography shows that the mature tooth and jaw bone appear as an X-ray opaque area, except for the basal region of the dentine. This region is composed of an X-ray translucent area and an X-ray opaque thin layer on the lingual side of the translucent area. The mature tooth is composed of two differently calcified areas: (1) a highly calcified area, which makes up almost all of the tooth and contains a thin layer of the basal dentine on the lingual side, and (2) a lowly calcified basal dentine, which is fused to the jaw bone. Therefore, the lowly calcified area does not completely separate the dentine and jaw bone. Repeating banding patterns among the collagen fibrils differ among the dentine-forming area and the matrices of dentine and jaw bone. During the formation of ankylosis of the tooth germ, collagen bundles in the dentine-forming area accumulate directly on the surface of the jaw bone. Consequently, the mature teeth of Xenopus laevis fuse to the jaw bone directly without the mediation of the other structures.

Animals↗