Staircase-pattern neonatal line in human deciduous teeth is associated with tooth type

Assessment of physiological disturbances during pre- and early postnatal development based on microscopic analysis of human deciduous teeth from the Late Epipaleolithic site of Shubayqa 1 (Jordan)

OBJECTIVES

To study pre- and early postnatal tooth formation and to analyze the effects of physiological disturbances on enamel and dentin formation in deciduous teeth of infants from the Late Epipaleolithic (Natufian) site Shubayqa 1.

MATERIALS AND METHODS

Ten deciduous teeth from six infants (ages at death between 21 and 239 days) were analyzed by light and scanning electron microscopy.

RESULTS

Marked prism cross-striations and an abnormal wavy course of the prisms were recorded in pre- and postnatal enamel of all analyzed teeth. Single or multiple accentuated incremental lines were observed in prenatal enamel of nine teeth and in postnatal enamel of eight teeth. Accentuated Andresen lines and broader zones exhibiting an enhanced calcospheritic pattern were recorded in the pre- and postnatally formed dentin of nine teeth.

DISCUSSION

The structural abnormalities in the pre- and postnatally formed enamel of the infants are considered indicative of chronic stress that negatively affected the activity of secretory ameloblasts. The structural aberrations in pre- and postnatal dentin denote that odontoblasts were also affected by this stress. The presence of single or multiple accentuated incremental lines in pre- and postnatal enamel is interpreted as reflecting (short-term) impacts of higher intensity superimposed on the chronic stress. Our findings suggest compromised maternal health affecting the late fetus and compromised health in newborns. Although limited by the small number of analyzed individuals, the present study contributes to the knowledge of maternal and early infant health conditions in Late Epipaleolithic populations.

Variation in mineral, organic, and water volumes at the neonatal line and in pre- and postnatal enamel

OBJETIVES

The neonatal line (NNL) in enamel is hypomineralized, but quantitative data on the enamel component volumes of the NNL are lacking. This study aimed at quantifying the variation in the mineral, organic, and water volumes at the NNL and in pre- and postnatal enamel.

MATERIALS AND METHODS

In buccal enamel longitudinal ground sections of exfoliated primary incisors (upper and lower; n = 17), the enamel component volumes were quantified at five histological sites (located at 40 μm intervals along a transversal line): the NNL, two sites in prenatal enamel, and two sites in postnatal enamel. Mineral volume was quantified using microradiography, and non-mineral volumes were quantified using polarizing microscopy.

RESULTS

Differences in component volumes between the NNL and pre- and postnatal enamel had high effect sizes (Hedge's G ranging from 0.89, for the water volume, to 1.88, for the mineral volume; power > 90 %). The distance from the NNL correlated with the normalized component volume: r = 0.459, 95 % CI = 0.274/0.612 (mineral); r = -0.504; 95 % CI= -0.328/-0.647 (organic), and r = -0.294; 95 % CI= -0.087/-0.476 (water). Approaching the NNL from postnatal enamel, the percentage differences in component volumes were: -1.93 to -3.22 % for the mineral volume, +21.26 to +35.42 % for the organic volume, and +3.86 to +6.03 % for the water volume. Towards postnatal enamel, the percentage differences had the opposite trend.

CONCLUSIONS

The enamel NNL is slightly hypomineralized with an increased organic volume one order of magnitude higher than the percentage differences in both mineral and water volumes.

Enamel neonatal line thickness in deciduous teeth of Australian children from known maternal health and pregnancy conditions

BACKGROUND

Physiological disruptions to early human development have implications for health and disease in later life. Limited research has explored how prenatal factors influence dental development in children of mothers with known pregnancy conditions. Enamel in human deciduous teeth begins forming in utero and is highly susceptible to physiological upsets experienced perinatally. The moment of birth itself is marked in deciduous enamel by the Neonatal Line (NNL) as a baby transitions from the uterine to external environment. This study evaluates the effect of maternal health factors that include stress and alcohol consumption on NNL in teeth from Australian children.

STUDY DESIGN AND SUBJECTS

Mothers (n = 53) were interviewed about their health during pregnancy and experience of birth. Sixty-five deciduous teeth (incisors, molars, one canine) from their children were donated for histological examination. Neonatal line thickness was measured from thin sections and evaluated against maternal and neonatal factors using statistical analyses, controlling for tooth type and birth number.

RESULTS AND CONCLUSIONS

The only maternal factor of a statistically significant effect on NNL thickness was alcohol consumption. Children of mothers who drank occasionally during pregnancy had a thicker NNL when compared to children of mothers who abstained. These results suggest that maternal lifestyle factors influence NNL formation possibly due to physiological changes that disrupt calcium homeostasis during enamel deposition. We highlight large intra-specific variation in human NNL expression. The potential of dental sampling in identifying children with prenatal exposure to alcohol is suggested.