Effect of hypocalcemic state on enamel formation in rat maxillary incisors

Craniofacial and dental characteristics of patients with vitamin-D-dependent rickets type 1A compared to controls and patients with X-linked hypophosphatemia

ᅟOBJECTIVES: Vitamin-D-dependent rickets type 1A (VDDR1A) is a rare inherited disease caused by defective activation of vitamin D. The aim of the study was to describe the craniofacial characteristics and the dental phenotype of patients with genetically confirmed VDDR1A. The VDDR1A findings were compared to findings in patients with X-linked hypophosphatemia (XLH) and healthy controls.

MATERIAL AND METHODS

Ten patients with VDDR1A were identified. The reference group for the comparison of cephalometric findings was 49 adults without chronic disease. The reference group for the comparison of dental findings was 30 adults with XLH. Clinical examination, clinical photos, and radiographs were obtained. Cephalometric analysis was performed. Photos and radiographs were visually evaluated.

RESULTS

The depth of the posterior cranial fossa (d-p and d-s-iop) in VDDR1A adults was reduced compared to the reference group (p < 0.05). Five (83%) of six adults with VDDR1A and one (4%) of 25 adults with XLH had enamel hypoplasia on several incisors and/or canines (p < 0.001). Three (75%) of four adults with VDDR1A and none of 16 adults with XLH had several first molars with enamel hypoplasia (p = 0.004). Five of 7 (71%) adults with VDDR1A and 24 of 30 (80%) adults with XLH had endodontically affected teeth.

CONCLUSIONS

The dental aberration of VDDR1A is more in line with the dental aberration of nutritional rickets than with the dental aberrations in XLH, suggesting the combination of low availability of both calcium and phosphate to be critical in periods of enamel formation.

CLINICAL RELEVANCE

Knowledge on craniofacial and dental aberration in patients with rare diseases, e.g., inherited rickets, is of importance to the dental practitioner, especially during diagnostics and treatment in special care units.

Aetiology of Molar-Incisor Hypomineralisation: A systematic review

AIM

This was to review and assess the studies on aetiology of Molar-Incisor Hypomineralisation (MIH) or, as a proxy, of demarcated opacities in permanent first molars and to consider the potential factors involved with findings obtained in animal experiments.

METHODS

A systematic search by Medline online database was performed. Abstracts behind appropriate titles were studied and finally the full articles were evaluated for their strength of evidence in the aetiology of MIH.

RESULTS

From a total of 1,142 articles 28 were identified and selected for review. The selected papers covered medical problems in prenatal, perinatal and postnatal period, medication of the child during the first years of life, and exposure to fluoride or environmental toxicants (dioxins and PCBs) in the early childhood. Based on the assessment of the articles it was still not possible to specifically name those factors causing MIH although correlations between several potential factors and MIH were presented. Among the factors suggested and found to cause enamel defects in animal experiments were: high fever, hypoxia, hypocalcaemia, exposure to antibiotics (amoxicillin, a macrolide), and dioxins.

CONCLUSION

Despite increased knowledge on the aetiology of MIH insufficient evidence to verify the causative factors exists. Further studies, especially prospective ones, are needed to improve the level and strength of evidence of the role of the present putative factors and to reveal new factors that may be involved. Any combined effect of several factors should be taken into account. Experimental dose/response studies and research on the molecular mechanisms causing the abnormal function of the ameloblasts are also necessary to deepen our knowledge of MIH.

Case report: Management of severe posterior open bite due to primary failure of eruption

BACKGROUND

Primary failure of tooth eruption (PFE) is a rare condition affecting any or all posterior quadrants. Unilateral involvement of maxillary and mandibular quadrants causes a dramatic posterior open bite that requires complex management strategies.

CASE REPORT

An 8 year-old boy attended the Dublin Dental School and Hospital regarding infra-occlusion of his right maxillary and mandibular primary molars. Both right first permanent molars had also failed to erupt. All permanent teeth were present radiographically. Facial appearance and soft tissues were normal and oral function was not affected. The patient had no significant medical history and his siblings had no similar dental abnormalities.

TREATMENT

The infra-occluded right first and second primary molars were extracted, and the right first permanent molars were surgically exposed.

FOLLOW UP

Eruption of the premolars and molars was monitored over the next 2 years. The premolars showed signs of eruption and continued root development. Exfoliation of the remaining primary teeth proceeded as usual. The right first permanent molars did not erupt and were subsequently extracted. Continued eruption of the canines and premolars reduced the inter-arch separation. A removable tongue shield appliance was suggested but declined by the patient. At age 13 years, orthodontic extrusion was used to further reduce the inter-dental distance between the canine and premolars. The reduction was from 5 mm to 1.5 mm between the right first premolars and from 10 mm to 5 mm between the right second premolars. Extrusion of the canine teeth was also attempted to improve the smile line. The canine extruded 1 mm to give a 2 mm overlap. There were no changes in centric occlusion and the midline was unaffected. In the 2 years since orthodontic treatment, the spaces have reopened slightly to 3 mm between first premolars and 6 mm between second premolars. The patient is now aged 16 years and is aware that an improved aesthetic smile line may be achieved by use of onlay restorations.

CONCLUSION

In this unique case, a profound unilateral posterior open bite occurred due to primary failure of eruption of the maxillary and mandibular teeth on the affected side. Orthodontic therapy was used to modify the position of the permanent canines and premolars to reduce the posterior open bite.