Etiology of Hypomineralized Second Primary Molars: A Prospective Twin Study

Abstract

The etiology of hypomineralized second primary molars (HSPM) is unclear, but genetic and environmental factors have been proposed. The aim of this study was to investigate the relative contribution of genes and environment to the etiology of HSPM and to identify potential environmental risk factors in a longitudinal twin cohort. Children from twin pregnancies ( N = 250) were recruited antenatally, and detailed demographic, health, and phenotypic data were collected at recruitment, 24- and 36-wk gestation, birth, and 18 mo of age. 25-Hydroxyvitamin D was quantified for mothers at 28-wk gestation and infants at birth. Dental examinations were conducted on the twins at 6 y of age to determine the presence, severity, and extent of HSPM per standardized criteria. To investigate associations of environmental risk factors with HSPM, multiple logistic regression models were fitted with generalized estimating equations to adjust for twin correlation. Within- and between-pair analyses were performed for unshared continuous variables: birthweight and birth 25-hydroxyvitamin D. Twin-twin concordance for monozygotic (MZ) and dizygotic (DZ) pairs was calculated and compared after adjusting for identified risk factors. A total of 344 twins underwent the 6-y-old dental assessment; HSPM occurred in 68 (19.8%). After adjusting for potential confounders, vitamin D levels at birth, infantile eczema, dizygosity, in vitro fertilization, socioeconomic position, and maternal smoking beyond the first trimester of pregnancy demonstrated the strongest associations with HSPM. Overall concordance for HSPM was 0.47 (95% CI, 0.32 to 0.62) with weak evidence ( P = 0.078) of higher concordance in MZ twins (0.63; 95% CI, 0.38 to 0.89) as compared with DZ twins (0.41; 95% CI, 0.24 to 0.58). After adjusting for known risk factors, there was no evidence ( P = 0.172) for an additive genetic influence. These findings suggest that shared and unshared environmental factors, such as maternal smoking later in pregnancy and infantile eczema, are important in the etiology of HSPM.

On the Variable Clinical Presentation of Molar-Incisor Hypomineralization

“…This model fits very well with MIH from what is known from the literature regarding variation in frequency, depending on geographic origin [Vieira and Kup, 2016], variation in severity and clinical presentation [Vieira and Kup, 2016], and no clear aggregation in families for most of the cases, although approximately 20% of families have additional affected family members [Jeremias et al, 2016]. Twin studies indeed showed a higher concordance rate for monozygotic twins in comparison with dizygotic ones both in the classic presentation of MIH [Teixeira et al, 2018] and in hypomineralized second primary molars [Silva et al, 2019]. Based on the figures published by Teixeira et al [2018], we could calculate that the amount of MIH variation in the population that can be explained by genetics is approximately 20% [Vieira, 2019].…”

Pre‐term birth and asthma is associated with hypomineralized second primary molars in pre‐schoolers: A population‐based study

“…Hypomineralization was diagnosed in 7.3% of the primary second molars in this study. The literature reported values ranging from 3.6% to 10.2% . This prevalence was considered high, and this is a cause for concern, since the HSPM may increase the risk of dental caries by 3 to 6.34 times …”

“…The literature reported values ranging from 3.6% to 10.2%. 1,4,6,7,12 This prevalence was considered high, and this is a cause for concern, since the HSPM may increase the risk of dental caries by 3 to 6.34 times. 4,26 HSPM can affect between 1 and 4 primary second molars.…”

“…1,3,5,6 The aetiology of HSPM is considered multifactorial but remains inconclusive. The literature reports an association between the enamel defect and the socioeconomic-demographic conditions: ethnicity, 3 socioeconomic situation, 3,7 cigarette smoking during pregnancy, 7 and in vitro fertilization 7 ; peri-natal conditions: low birthweight 3 ; and post-natal: fever in the first year of life 3 and eczema in the first 18 months of life. 7 The prevalence of HSPM varies between 2.5% and 21.8% in different countries.…”

Validity and reproducibility testing of the Molar Incisor Hypomineralisation (MIH) Index

“…Several researchers are using/have used the index, but its properties, in terms of validity and reproducibility, are yet to be tested. As with any new index, the MIH/HSPM index needs to demonstrate adequate reproducibility (ie reliability) and validity to be used for clinical assessment.…”