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At least 955 records · Page 53Linked to original sources
PubMed1991

Mineral content of different areas of human dentin in hypophosphataemic vitamin D-resistant rickets.

Calcium, phosphorus, fluoride, sodium, magnesium and zinc estimations were carried out on teeth from a patient with hypophosphataemic vitamin D-resistant rickets (HVDRR) and from a patient with acquired rickets with the aim of determining differences in the composition of dentine in these two types of rickets. Normal deciduous teeth served as controls. Mineral analyses were carried out using an electron probe micro-analyser after carefully polishing the hemisected specimens. After the analyses the specimens were coated with gold-palladium for more detailed SEM studies. The Ca, P, F and Zn contents of the calcospherites were normal, while there was more Na and less Mg in the dentine of HVDRR teeth than of controls. The significance of this remains unexplained. The mineral content of the interglobular spaces was very limited, but there was more Zn in these than in other parts of the HVDRR teeth, in the acquired rickets teeth or in the control teeth. The excess of Zn in the interglobular spaces is thought to have an effect on the mineralisation process in HVDRR teeth. The globular nature of HVDRR teeth is thought to be genetically controlled and the result of a reduction in the number of calcification nuclei. The globular nature of the HVDRR teeth was not due to lack of Ca and P, as the serum levels of these minerals were maintained within normal limits during tooth development by controlled phosphate supplementation. Because in acquired rickets the globules were seen at the developmental stage that the teeth had reached when the nutritional disturbance occurred, the fault in mineralisation is thought to be different from that in HVDRR teeth.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium↗
PubMedDate not supplied

Scanning electron microscopic analysis of dentin in vitamin D-resistant rickets--assessment of mineralization and correlation with clinical findings.

In vitamin D-resistant rickets, the basic dental defect is manifested in dentin. Structural investigations of rachitic dentin by light and scanning electron microscopy have revealed the presence of calcospherites separated by interglobular dentin. This occurs when calcospherites do not fuse. This study investigated the morphology and ultrastructure of rachitic dentin with three different clinical and histologic grades of severity to determine if dentin mineralization can be quantified by calcospherite size and degree of calcospherite fusion. The results showed that a correlation existed between calcospherite size, calcospherite fusion, and the degree of dentin mineralization. The present findings indicate that calcospherite size and calcospherite fusion are valid parameters for assessing and quantifying dentin mineralization. In addition, an SEM grading of severity was established based on these two parameters. The SEM grades correlated directly with the clinical and histologic grades, suggesting that the dental clinical manifestations are a reflection of the underlying morphology of the dentin and the extent of abnormal dentin mineralization.

Dentin↗
PubMed1991

Untreated hypophosphatemic vitamin D-resistant rickets with symptomatic ossification of the ligamentum flavum.

An adult case of untreated hypophosphatemic vitamin D-resistant rickets with symptomatic ossification of the ligamentum flavum in the thoracic region is reported and discussed with regard to the calcium metabolism and the ligamentous ossification. Factors influencing ossification of the ligamentum flavum may be mechanical stress on the spine and an increase in calcium retention.

Adult↗
PubMed2006

[From gene to disease; hypophosphataemic rickets and the PHEX gene].

X-linked hypophosphataemic rickets is associated with mutations in the PHEX gene on the short arm of the X chromosome, encoding a membrane-bound endoprotease which is predominantly expressed in osteoblasts. Defective PHEX function leaves phosphaturic peptides such as FGF23 uncleaved, enabling these peptides, known as phosphatonins, to fully exert their phosphaturic potential in the proximal tubule of the kidney. An autosomally inherited form of hypophosphataemic rickets is caused by mutations in the proteolytic processing site of FGF23 itself, while in tumour-induced osteomalacia overproduction of FGF23 and possibly other phosphatonins causes the processing capacity to be exceeded, resulting in phosphaturic hypophosphataemia and osteomalacia.

Chromosomes, Human, X↗
PubMed2006

Prevalence and pathogenesis of dental and periodontal lesions in children with X-linked hypophosphatemic rickets.

AIM: To assess the prevalence and to investigate the pathogenetic mechanisms of dental and periodontal lesions in children with X-linked hypophosphatemic rickets (XLH) examined at diagnosis or during treatment. METHODS: Nine children with XLH (age 7.2 +/- 3.3 years) were enrolled in the study (at diagnosis, n = 2; during treatment with oral inorganic phosphate salts combined with 1,25-dihydroxyvitamin D3, n = 7). Oral examination was performed according to the evidence of carious and gingival lesions. Decayed or filled teeth (dft) index for primary teeth, and the decayed, missing, or filled teeth (DMFT) index for permanent teeth was assessed. All patients with a history of spontaneous dental abscesses underwent orthopantomography examination. RESULTS: d/D ranged from 0 to 9 and f/F from 0 to 3. DMFT/dft index was 0 in the three youngest patients. One patient had enamel hypoplasia and two had enamel dyschromic alterations. Six out of nine patients (67%) had a history of spontaneous fistulae as a consequence of periapical abscesses occurring in the absence of dental decay or history of injury. In these patients, orthopantomographies showed enlarged pulp chambers associated with prominent pulp horns extending up to the dentino-enamel junction in both primary and permanent dentition. CONCLUSION: XLH patients show some peculiar dentinal abnormalities. Treatment prevents only in part dental and periodontal lesions. Genetic mechanisms have a main role in causing defective dentin mineralisation.

Adolescent↗
PubMedDate not supplied

Material matters: a mechanostat-based perspective on bone development in osteogenesis imperfecta and hypophosphatemic rickets.

This perspective paper presents a hypothesis that links abnormalities of bone material with densitometric findings in two congenital metabolic bone disorders, osteogenesis imperfecta type I (OI) and X-linked hypophosphatemic rickets (XLH). Analyses of iliac bone samples from OI patients have shown that material bone density is elevated and that the bone material is abnormally stiff in this disorder. Therefore, a given mechanical load on an OI bone will generate a smaller than normal deformation. This in turn should lead osteocytes, the putative mechanosensing cells, to systematically underestimate the prevailing mechanical forces. According to the mechanostat model, bone strength should then be adapted to the underestimated mechanical loads, which means that bone architecture and mass remain below requirements. Available densitometric studies are in accordance with this hypothesis. In XLH, a mild mineralization defect persists despite treatment. This mineralization defect should lead to soft bone material. In analogy to the above model for OI, mechanical loads should be overestimated, resulting in increased densitometric parameters of bone strength. Indeed, lumbar spine areal bone mineral density is usually elevated in such patients.

Biomechanical Phenomena↗