Deciduous neonatal line: Width is associated with duration of delivery

Enamel histomorphometry, growth patterns and developmental trajectories of the first deciduous molar in an Italian early medieval skeletal series

Understanding the growth patterns and developmental trajectories of teeth during early life stages provides valuable insights into the ontogeny of individuals, particularly in archaeological populations where such information is scarce. This study focuses on first deciduous molars, specifically investigating crown formation times and daily secretion rates, through histological analysis. A total of 34 teeth from the Early Medieval necropolises of Casalmoro and Guidizzolo (Mantua, Lombardy, northern Italy) were analysed assessing growth parameters and identifying possible differences between sites and between sexes, which are determined through proteomic analysis. Furthermore, a robust linear regression model relating prism length and secretion time was built to estimate growth rates also in teeth in which the finest incremental markings are not visible. The daily secretion rates (DSR) in inner enamel showed a high homogeneity between dental arches, sexes and the two sites. Values fall within the known range reported in the literature for the same tooth class in archaeological populations. However, a difference in DSR was observed when compared with modern sample published values. Crown formation times and age at crown completion differ between dental arches, with maxillary first molars initiating their matrix apposition earlier than mandibular molars as formerly reported. However, no significant differences were highlighted in association with sex. This study expands our understanding of the growth and development of the first deciduous molars in a medieval population, providing valuable insights into growth trajectories specific to the dental arch. These findings highlight the need for extensive investigations using similar methodologies to attain more accurate and comprehensive information about the developmental patterns of first deciduous molars. Additionally, proteomic analysis improves the capability to conduct sex-specific histological assessments of immature individuals, thanks to this method's application in determining their sex.

Enamel incremental markings in the deciduous teeth of children from the Early Bronze and modern ages

OBJECTIVE

The purpose of this study was to determine whether children from Early Bronze Age and modern populations differ in terms of the width of the neonatal line (NNL) and the occurrence of accentuated lines in enamel.

DESIGN

The sample (N = 59) consisted of two groups: 29 deciduous teeth removed from the jaws of children (dental age range from 1 to 10 years) whose skeletal remains were found in Early Bronze archaeological graves in Mokrin Serbia, and 30 present-day exfoliated deciduous teeth from 6 to 11 year old children. Mothers, whose children participated in this study, provided information regarding their health during pregnancy. The analysis was carried out on ground sections with a scanning electron microscope. Two clinicians measured the width of the NNL and counted the accentuated lines in the enamel.

RESULTS

There was a statistically significant difference between the children from the two groups regarding the width of the NNL. The width of the NNL between children whose mothers were healthy and diagnosed with gestational diabetes was significantly different. Most subjects did not have accentuated lines in the prenatal enamel, regardless of whether they were from the Bronze or Modern age. Accentuated lines were dominantly found in the postnatal enamel of the children from the Early Bronze age.

CONCLUSIONS

This study is the first to investigate the width of the NNL in teeth of Maros children and Serbian children from the modern age. The wider NNL of children from the Early Bronze age indicates the possibility that they have experienced more overall stress in perinatal life.

Caries experience among children born after a complicated pregnancy

Objectives

Behavioural and lifestyle factors, as oral hygiene and diet, are well‐established risk factors in the pathogenesis of dental caries, though displaying large differences in susceptibility across individuals. Since enamel formation already starts in utero, pregnancy course and outcome may eventually play a role in enamel strength and caries susceptibility. Therefore, we studied the association between history of pregnancy complications and the caries experience in their six‐year‐old children. The pregnancy complications included small for gestational age (SGA), spontaneous preterm birth (sPTB), gestational hypertension (GH), pre‐eclampsia (PE), individually, and a combination of those, designated as placental syndrome.

Methods

This study was embedded in Generation R, a prospective longitudinal Dutch multiethnic pregnancy cohort study. Information about pregnancy complications was obtained from questionnaires completed by midwives and obstetricians with cross‐validation in medical records. These included SGA, sPTB, GH and PE. Caries experience was assessed with the decayed, missing and filled teeth (dmft) index at a mean age of six years. The association between dental caries experience and a history of pregnancy complications was studied by using hurdle negative binomial (HNB) models.

Results

We were able to assess the dmft index in 5323 six‐year‐old children (mean age 6.2 years, SD 0.5). We did not find an association between the different pregnancy complications and dental caries experience in childhood, whether for SGA, sPTB, GH, PE, or for the combined outcome placental syndrome (HNB estimates: OR 1.02, 95%CI 0.87 ‐ 1.19; RR 0.90, 95%CI 0.78 ‐ 1.04). Further adjustment of the models with different confounders did not alter the outcome.

Conclusions

Although it is expected that prenatal stress can be a risk factor for caries development later in life, our findings do not support this hypothesis. Therefore, we believe disparities in caries experience between children are probably not explained by early life events during a critical intrauterine period of development.

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.

Teeth as Potential New Tools to Measure Early-Life Adversity and Subsequent Mental Health Risk: An Interdisciplinary Review and Conceptual Model

Early-life adversity affects nearly half of all youths in the United States and is a known risk factor for psychiatric disorders across the life course. One strategy to prevent mental illness may be to target interventions toward children who are exposed to adversity, particularly during sensitive periods when these adversities may have even more enduring effects. However, a major obstacle impeding progress in this area is the lack of tools to reliably and validly measure the existence and timing of early-life adversity. In this review, we summarize empirical work across dentistry, anthropology, and archaeology on human tooth development and discuss how teeth preserve a time-resolved record of our life experiences. Specifically, we articulate how teeth have been examined in these fields as biological fossils in which the history of an individual's early-life experiences is permanently imprinted; this area of research is related to, but distinct from, studies of oral health. We then integrate these insights with knowledge about the role of psychosocial adversity in shaping psychopathology risk to present a working conceptual model, which proposes that teeth may be an understudied yet suggestive new tool to identify individuals at risk for mental health problems following early-life psychosocial stress exposure. We end by presenting a research agenda and discussion of future directions for rigorously testing this possibility and with a call to action for interdisciplinary research to meet the urgent need for new biomarkers of adversity and psychiatric outcomes.

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.

Synchrotron X-ray fluorescence mapping of Ca, Sr and Zn at the neonatal line in human deciduous teeth reflects changing perinatal physiology

OBJECTIVES

Our first objective was to review the evidence describing the appearance and microstructure of the neonatal line in human deciduous teeth and to link this with known changes in neonatal physiology occurring at and around birth. A second objective was to explore ways to improve identification of the neonatal line by mapping the pre- and postnatal distribution of Ca, Sr and Zn in deciduous cuspal enamel and superimposing these maps onto transmitted light micrographs that included a clear true section of the neonatal line.

MATERIALS AND METHODS

We used synchrotron X-ray fluorescence to map elemental distributions in pre- and postnatal enamel and dentine. Two deciduous canines and 5 deciduous molars were scanned with an X-ray beam monochromatised to 17.0 keV at either 10.0, 2.5 or 1.0 μm resolution and 10 ms integration time.

RESULTS

Calcium maps distinguished enamel and dentine but did not clearly demarcate tissues formed pre- or postnatally. Strontium maps reflected presumed pre- and postnatal maternal serum levels and what are likely to be diet-dependent regions of Sr enrichment or depletion. Prenatal Zn maps, particularly for dentine, mirror elevated levels in the fetus and in colostrum during the first few days of life.

CONCLUSIONS

The neonatal line, enamel dentine junction and surface enamel were all Zn-rich. Within the neonatal line Zn may be associated with increased crystallinity but also with caries resistance, both of which have been reported previously. Elemental mapping may improve the identification of ambiguous NNLs and so be useful in forensic and archaeological studies.

Those who died very young-Inferences from δ15 N and δ13 C in bone collagen and the absence of a neonatal line in enamel related to the possible onset of breastfeeding

OBJECTIVES

Stable isotope analysis has often been used in neonatal remains from archeological contexts to investigate the presence of a signal of breastfeeding and weaning in past populations. Tooth histology on the other hand might be used as an indicator of birth survival. This pilot study aimed to investigate the feasibility of using stable nitrogen (δ¹⁵ N) and carbon (δ¹³ C) isotope values from neonatal bone collagen to elucidate if values deviating from the adult female average could indicate breastfeeding and co-occur with the presence of a neonatal line (NNL). The combination of these independent indicators might be useful in clarifying the fate of individuals who died around birth.

MATERIALS AND METHODS

Bone collagen from 21 archeological human and animal specimens was extracted and analyzed via mass-spectrometry for δ¹⁵ N and δ¹³ C. A verification of the stable isotope results was undertaken using tooth histology on three individuals who were investigated for the presence of a NNL as an indicator of live birth and short survival.

RESULTS

The biological age of the human samples varied between 8.5 lunar months (Lm) and 2 postnatal months (Pm) of age. All except one individual exhibited elevated δ¹⁵ N values compared to the female average. The histological analyses revealed no NNL for this and two further individuals (n = 3).

DISCUSSION

The results indicate that elevated nitrogen values of very young infants relative to a female average in archeological contexts are not necessarily associated with a breastfeeding onset signal, and therefore cannot be used exclusively as a proxy of birth survival. The elevation might be possible due to various reasons; one could be nutritional, in particular maternal stress during pregnancy or a metabolic disorder of mother and/or her child. In those cases, the evaluation of a NNL might reveal a false breastfeeding signal as seen for two individuals in our sample who have elevated nitrogen values despite the fact no NNL could be observed. Overall, our data support the growing awareness that bone collagen δ¹⁵ N values of neonates/infants should not be used as a proxy for breastfeeding or birth survival on its own.