Tooth Development Associated with Mutations in Hereditary Vitamin D-Resistant Rickets

Hereditary vitamin D-resistant rickets (HVDRR) is a rare genetic disorder caused by mutations at the level of the vitamin D receptor ( VDR) gene. The disease is characterized by refractory hypocalcemia, elevated serum levels of 1,25-dihydroxy-vitamin D, retarded growth, sparse body hair (sometimes alopecia), premature tooth loss, enlarged pulp chambers, thin dentine, and hypoplastic enamel. The aims of this study were 1) to document the dental development of children with HVDRR in association with the mutation type within the VDR and 2) to evaluate the association between dental development and the timing of and response to HVDRR treatment. Genome analysis was performed for 4 affected children (2 y 2 mo to 6 y 8 mo) under treatment with high doses of vitamin D and calcium. Longitudinal records of clinical and radiographic data on their dental development were assessed in relation to genetic profile and response to treatment. Treatment success depended on the position of the mutation within the VDR protein: children with the p.R391S mutation had a favorable outcome but maintained alopecia totalis, while 1 child with the p.H397P mutation and normal hair had no response to very high doses of vitamin D. The primary incisors, formed prenatally and first to emerge, were missing in 3 children and mobile in 1 child; parents reported loss within months posteruption. Posterior teeth were present, having erupted after treatment initiation. Hypoplastic enamel in emerging teeth was associated with late treatment onset. Mutation type in the VDR gene appears to be related to differences in the disease phenotype and response to treatment. Dental development represents an indicator of the disease process, initially protected by maternal blood levels of calcium and later restored by therapeutic supplies that normalize these levels. Knowledge Transfer Statement: Two novel mutations were associated with different HVDRR phenotypes, one of which responded positively to treatment. Early detection of the mutation should help pediatricians forecast treatment protocol and response. The results also highlight the direct relationship between dental development and blood calcium levels, underscoring the importance of early diagnosis and treatment of HVDRR to minimize the loss of primary teeth and reduce structural abnormalities of permanent teeth.

New insights on age-related association between nasopharyngeal airway clearance and facial morphology

OBJECTIVES

To evaluate the relation between adenoid hypertrophy and facial morphology across age in a pediatric population.

SETTING AND SAMPLE POPULATION

The American University of Beirut Department of Otolaryngology. Two-hundred consecutive children (age 6.00 ± 2.62 years) referred from the Pediatric Otolaryngology unit to the Orthodontic division and requiring a lateral cephalogram for adenoid hypertrophy assessment.

METHODS

Cephalometric measurements included relations among cranial base, maxilla and mandible, and airway clearance measured from adenoid to soft palate (AD). The children were classified into two age groups, Group 1: ≤ 6 years (n = 124) and Group 2: ≥ 6.01 years (n = 76), and also stratified in four subgroups (A, B, C, D) based on maxillo-mandibular divergence (palatal to mandibular plane angle, PP-MP): A- PP-MP ≤ 27.5°, n = 34; B- 27.5° < PP-MP ≤ 32°, n = 68; C- 32°<PP/MP<36.5°, n = 67; D- PP-MP ≥ 36.5°, n = 31. Statistics included t-tests and anova for group differences.

RESULTS

  Differences between groups 1 and 2 were statistically significant (p < 0.05) for AD (Group 1: 3.19 ± 2.32 mm, Group 2: 4.78 ± 2.80 mm), ANB (5.38 ± 2.24°, 4.38 ± 2.54°), LFH (56.61 ± 1.95%, 55.38 ± 1.84%), PP-H (-8.41 ± 3.28°, -6.49 ± 3.46°), and overbite (0.55 ± 2.00 mm, 1.16 ± 2.36 mm). Among subgroups, statistically significant differences (p < 0.05) occurred mainly between the most hyperdivergent group (D) and the hypodivergent (A) and normodivergent (B) groups.

CONCLUSIONS

Airway measurements were smallest in children ≤ 6 years and those presenting severe hyperdivergent pattern, which denoted the most severe airway obstruction. The findings suggest airway clearance before age 6 in the most severely affected children, but follow-up research on actual adenoidectomies in younger children is needed to determine guidelines.

Monitoring growth during orthodontic treatment

The relationship between somatic growth and orthodontic treatment has been limited to the evaluation of body height and skeletal age relative to craniofacial development. The aim of this study was to evaluate the correlation of anthropometric and biochemical measures of general growth with facial and occlusal changes during the early treatment of Class II Division 1 malocclusion. Findings are reported from 46 children, ages 7.20 to 12.85 years (skeletal ages, 5.75 to 12.75 years), who are enrolled in a prospective clinical trial. Body and knee heights were measured monthly, with a Holtain stadiometer and a Knee Height Measuring Device, respectively. Every three months, serum levels were measured of the hormone dehydroepiandrosterone sulfate (DHEAS), an androgen associated with growth in midchildhood, and osteocalcin, an indicator of bone turnover. Significant correlations existed between knee height and various occlusal measurements, but mandibular length was not significantly correlated with knee height and DHEAS levels. Knee height correlated significantly (P < .05) with DHEAS and osteocalcin only in 46% and 37% of the children, respectively. The results indicate that the evaluated biochemical measures, at the time intervals considered, may not increase the accuracy of growth depiction by physical measures alone (height and skeletal maturation).