Enamel structure and composition in the tricho-dento-osseous syndrome

Interrelationships Between Morphometric, Densitometric, and Mechanical Properties of Teeth in 5-Month-Old Polish Merino Sheep

Interrelationships between morphological, densitometric, and mechanical properties of deciduous mandibular teeth (incisors, canine, second premolar) were investigated. To perform morphometric, densitometric, and mechanical analyses, teeth were obtained from 5-month-old sheep. Measurements of mean volumetric tooth mineral density and total tooth volume were performed using quantitative computed tomography. Microcomputed tomography was used to measure total enamel volume, volumetric enamel mineral density, total dentin volume, and volumetric dentin mineral density. Maximum elastic strength and ultimate force of teeth were determined using 3-point bending and compression tests. Pearson correlation coefficients were determined between all investigated variables. Mutual dependence was observed between morphological and mechanical properties of the investigated teeth. The highest number of positive correlations of the investigated parameters was stated in first incisor indicating its superior predictive value of tooth quality and masticatory organ function in sheep. Positive correlations of the volumetric dentin mineral density in second premolar with final body weight may indicate predictive value of this parameter in relation with growth rate in sheep. Evaluation of deciduous tooth properties may prove helpful for breeding selection and further reproduction of sheep possessing favorable traits of teeth and better masticatory organ function, leading to improved performance and economic efficiency of the flock.

Endodontic management of a hypertaurodontic tooth associated with 48, XXYY syndrome: A review and case report

Taurodontism is a developmental anomaly of a tooth characterized by large pulp chamber and short roots. Patients with multiple taurodontic teeth are associated with the probability of a systemic syndrome or chromosomal anomaly. This is the first reported incidence of the endodontic management of a hyper taurodontic mandibular second molar in a patient diagnosed with 48, XXYY syndrome.

Systemic disorders and their influence on the development of dental hard tissues: a literature review

OBJECTIVES

This report highlights the influence of a number of disorders with systemic physiological effects that impact on the development of dental hard tissues. It focuses in particular, on the pathological effects of systemic conditions with less well recognised, but no less important, impacts on dental development. Such conditions, include cystic fibrosis, HIV/AIDS, leukaemia, Alstrom syndrome, hypophosphatasia, Prader-Willi syndrome, Tricho-dento-osseous syndrome, tuberous sclerosis, familial steroid dehydrogenase deficiency and epidermolysis bullosa. These, along with developmental and environmental causes of enamel and dentine defects, are discussed and the possible aetiology of such effects are proposed. Furthermore, the dental management and long-term dental care of these patients is outlined.

SOURCES

MEDLINE/PubMed.

CONCLUSIONS

Enamel and dentine defects can present with a wide spectrum of clinical features and may be caused by a variety of factors occurring throughout tooth development from before birth to adulthood. These may include host traits, genetic factors, immunological responses to cariogenic bacteria, saliva composition, environmental and behavioural factors and systemic diseases. These diseases and their spectrum of clinical manifestations on the organs affected (including the dentition) require an increased knowledge by dental practitioners of the disease processes, aetiology, relevant treatment strategies and prognosis, and must encompass more than simply the management of the dental requirements of the patient. It is important that the impact of the disease and its treatment, particularly in respect of immunosuppression where dental interventions may become life-threatening, is also taken into consideration.

Thickness and microhardness of deciduous tooth enamel with known DLX3 mutation

AIM

To investigate the thickness and hardness of teeth affected by a 2-bp deletion (c.561_562delCT) in the DLX3 gene.

METHODS AND MATERIALS

Extracted maxillary deciduous second molar was collected from the affected individual at age 12 years 7 months. Samples were sectioned buccolingually after embedding in epoxy resin. We measured the enamel thickness and microhardness and performed an elemental analysis using an electron probe microanalyser.

RESULTS

On average, the hardness of the enamel with a 2-bp deletion in DLX3 was about 53% of normal enamel hardness. The mutant enamel thickness was about half of the thickness of the normal control. The calcium level in the enamel with the 2-bp deletion was slightly decreased, while the magnesium level was slightly increased, in comparison to levels measured for normal teeth.

CONCLUSION

This study shows that enamel affected by a 2-bp deletion in DLX3 has reduced thickness as well as diminished microhardness. These data may explain the severe attrition and interdental spacing observed in affected individuals.

Severely hypoplastic amelogenesis imperfecta with taurodontism

BACKGROUND

The prominent dental feature of a boy was severely hypoplastic enamel in both primary and permanent teeth.

CASE REPORT

Many permanent teeth were already infected while emerging in the oral cavity. Panoramic radiograph showed enlarged and elongated pulp chambers (taurodontism) in the permanent first molars. The clinical and radiological diagnosis was either hypomaturation-hypoplastic amelogenesis imperfecta with taurodontism (AIHHT) or tricho-dento-osseous syndrome (TDO). Histological examination of the upper right permanent first molar revealed thin lamellar or somewhat thicker amorphous enamel on approximal surface only with no rods or incremental lines visible. Histologically, the Witkop type AIG designated 'enamel agenesis' cannot be excluded. The medical and dental history of the family members, as well as the boy's medical examination, was noncontributing. He had thick, blond, curly hair. The bone structure of the jaws and skull was normal. For genetic analysis, DLX3 gene was sequenced but no mutation was found.

CONCLUSIONS

Since the gene defect of TDO has been localized only in the DLX3 gene, the more probable diagnosis was AI.

Tricho-dento-osseous syndrome and amelogenesis imperfecta with taurodontism are genetically distinct conditions

Amelogenesis imperfecta of the hypomaturation-hypoplasia type with taurodontism (AIHHT) is inherited as a highly penetrant autosomal dominant trait. These dental findings are similar to those of another autosomal dominant condition, the tricho-dento-osseous syndrome (TDO), from which AIHHT differs primarily by lack of changes in the hair and bones. TDO is characterized by a highly variable clinical phenotype. While enamel hypoplasia and taurodontism appear to be present in all TDO cases, non-dental features may be absent, with approximately half of TDO cases losing the kinky/curly hair phenotype seen in infancy by adolescence, and in almost 20% of cases, osseous changes are not evident. The genetic basis for AIHHT is unknown and it has been questioned whether AIHHT and TDO are separate conditions or a spectrum of disease. The genetic basis for TDO has recently been identified as a deletion mutation in the distal-less 3 (DLX3) transcription factor gene. To determine if AIHHT and TDO represent variable expression of a common DLX3 gene mutation, allelic mutations of the DLX3 gene, or mutations in DLX7 (the linked paralogue to DLX3 on chromosome 17), we have performed mutational analysis and sequencing studies of the DLX3 and DLX7 genes in three individuals (two affected and one unaffected) from a family with AIHHT. Results of the analysis demonstrate that AIHHT and TDO are not due to a common DLX3 gene mutation. Sequence analyses of the DLX3 and DLX7 genes suggest AIHHT is not due to genetic mutations or polymorphisms in the exons of these genes. These results suggest that AI-HHT and TDO are two genetically distinct conditions.