Age-related dental phenotypes and tooth characteristics of FAM83H-associated hypocalcified amelogenesis imperfecta

OBJECTIVES

Autosomal-dominant hypocalcified amelogenesis imperfecta (ADHCAI) shows phenotypic heterogeneity. Our aim was to characterise the ADHCAI phenotypes, tooth properties and genotypes.

METHODS

Three unrelated ADHCAI probands and seven additional affected members of the three families were recruited. Mutations were identified by exome and Sanger sequencing, and haplotypes by SNP array. Tooth colour, roughness, density, nanohardness, minerals and ultrastructure were investigated.

RESULTS

Ten participants were heterozygous for the FAM83H mutation c.1387C>T (p.Gln463*). All shared a 3.43 Mbp region on chromosome 8q24.3 encompassing the FAM83H variant, indicating a common ancestry. The c.1387C>T was estimated to be 23.8 generations or 600 years. The FAM83H enamel had higher roughness and lower lightness, density, nanohardness, and calcium and phosphorus levels than controls. Blunted enamel rods, wide interrod spaces and disorganised dentinoenamel junctions were observed. Evaluating the patients with the same mutation and reviewing others with different mutations in FAM83H revealed that the FAM83H heterogeneous phenotypes are age-influenced. Tooth colour and surface texture change with ageing.

CONCLUSIONS

FAM83H enamel demonstrated decreased lightness, density, hardness, calcium, phosphorus and defective ultrastructure. We have identified that the phenotypic variation in FAM83H-associated ADHCAI is age-related. Awareness of the correlation between age and clinical features of FAM83H-ADHCAI can help dentists make an accurate diagnosis.

Relationship between deciduous molar hypomineralisation and parameters of bone metabolism in preschool children

BACKGROUND

The aetiology of deciduous molar hypomineralisation (DMH) is still largely unknown.

AIM

The aim of the study was to elucidate the occurrence of DMH as a function of the parameters of bone metabolism, as it is suspected that abnormalities in these parameters may affect the mineralisation of teeth.

DESIGN

In a prospective cohort study, 958 children aged 1-6 years were examined. The inclusion criteria were: a blood sample to determine the parameters of bone metabolism; and documentation of enamel mineralisation using the European Academy of Paediatric Dentistry (EAPD) criteria. Multivariable methods were applied to analyse the incidence of DMH relative to the concentrations of serum calcium, phosphate, vitamin D, vitamin B12 and alkaline phosphatase, taking into account the effects of age, gender and height.

RESULTS

The proportion of children diagnosed with DMH was 4.0% (38 of 958). A significant difference between DMH-affected and non-DMH-affected children was found only in the serum concentration of calcium (2.47 ± 0.08 mmol/l vs. 2.52 ± 0.10 mmol/l, respectively, P = 0.004). The risk of DMH significantly increased, by 1.63-fold (95% CI: 1.03-2.57), if the calcium level dropped by 0.1 mmol/l, regardless of age, gender or adjusted height. During the follow-up examination of 17 DMH-affected subjects, the calcium level remained consistently low 1 year later (t-test, P > 0.05).

CONCLUSION

Children with DMH showed consistently subclinically lower serum calcium levels. No associations were found for other parameters.

Etiology of molar incisor hypomineralization - A systematic review

OBJECTIVES

Molar incisor hypomineralization (MIH) is a common developmental dental defect of permanent teeth, which can increase the risk of dental caries, infection and hospitalization. The etiology is currently unclear although prenatal or early childhood health factors are suspected. The aim of this systematic review was to assess the strength of evidence linking etiological factors with MIH.

METHODS

A systematic search was conducted using the Medline and Embase electronic databases for studies investigating environmental etiological factors of MIH. Two reviewers assessed the eligibility of studies. The level of evidence and bias was determined for all eligible studies according to Australian National Health and Medical Research Council guidelines for systematic reviews of etiology and the Newcastle-Ottawa Scale.

RESULTS

From a total of 2254 studies identified through electronic and hand searching, 28 were eligible for inclusion. Twenty-five of these investigated MIH and three investigated a related condition in primary teeth, hypomineralized second primary molars (HSPM), and these were analysed separately. A limited number of studies reported significant associations between MIH and pre- and perinatal factors such as maternal illness and medication use in pregnancy, prematurity and birth complications. Early childhood illness was implicated as an etiological factor in MIH in several studies, in particular fever, asthma and pneumonia. The studies investigating HSPM revealed an association with maternal alcohol consumption, infantile fever and ethnicity. However, the validity of these findings is impaired by study design, lack of adjustment for confounders, lack of detail and consistency of exposures investigated and poor reporting.

CONCLUSIONS

Childhood illness is likely to be associated with MIH. Further prospective studies of the etiology of MIH/HSPM are needed.