Microscopy of the neonatal line in developing human enamel

Weber, D.; Eisenmann, D

doi:10.1002/aja.1001320307

Cited by 66 publications

(30 citation statements)

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“…1979;Massler and Schour 1946;Schour 1936;Schour and Massler 1937;Weber and Eisenmann 1971;Whittaker and Richards 1978), it is possible, or even likely, that physiological weight fluctuations along the first week may affect NL thickness variation.…”

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confidence: 99%

“…As a whole, the NL is observable in over 90% of primary dentitions and 10% of first permanent molars of individuals having survived the perinatal stage, i.e. at least the first 3-7 to 10-15 days ex utero (e.g., Levine et al 1979;Massler and Schour 1946;Schour 1936;Schour and Massler 1937;Weber and Eisenmann 1971;Whittaker and Richards 1978).This scar can be distinctly recognised because of the differences in quality between preand postnatal enamel (Humphrey et al 2007;Kodaka et al 1996;Thomas and Lee 2003;Wilson and Beynon 1989), as well as due to its characteristic location, specific for each tooth class (Skinner 1992;Skinner and Dupras 1993;Rossi et al, 1999). The NL, whose variable thickness in humans may reach or even exceed 30 µm (Rossi et al 1999;Schour 1936;Weber and Eisenmann 1971), is distinguishable from a Wilson band because it is more prominent and displays a more clearly discernible prism disturbance (Kodaka et al 1996;Rushton 1939;Skinner 1992;Skinner and Dupras 1993;Thomas and Lee 2003;Wilson and Beynon 1989).…”

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confidence: 99%

“…The NL, whose variable thickness in humans may reach or even exceed 30 µm (Rossi et al 1999;Schour 1936;Weber and Eisenmann 1971), is distinguishable from a Wilson band because it is more prominent and displays a more clearly discernible prism disturbance (Kodaka et al 1996;Rushton 1939;Skinner 1992;Skinner and Dupras 1993;Thomas and Lee 2003;Wilson and Beynon 1989).…”

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confidence: 99%

“…at least the first 3-7 to 10-15 days ex utero (e.g., Levine et al 1979;Massler and Schour 1946;Schour 1936;Schour and Massler 1937;Weber and Eisenmann 1971;Whittaker and Richards 1978).…”

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confidence: 99%

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Gestation Length, Mode of Delivery, and Neonatal Line-Thickness Variation

Zanolli

Bondioli

Manni³

et al. 2011

Human Biology

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ABTRACTThe transition from an intra-to extra-uterine environment leaves its mark in deciduous teeth (and first permanent molars) as an accentuated enamel incremental ring called the neonatal line (NL). This prominent microfeature separates the enamel formed during intrauterine life from that formed after leaving the womb. However, while the physical structure of this scar is well known, the bases of its formation are still a matter of investigation. In particular, besides the influence of the birth-related abrupt environmental and dietary changes and the role played by physiological factors such as hypocalcaemia, it has been suggested a direct relationship between NL thickness variation and the physical trauma implied by the birth dynamics, the Caesarean and the operative modes being apparently associated to the thinnest and the thickest lines, respectively. By using the histological record from a deciduous dental sample (exfoliated crowns) of 100 modern healthy school-aged children (47 males and 53 females) of reported birth histories (normal delivery mode: 55 cases; Caesarean: 40; operative: 5), we investigated the relationships between birth dynamics and NL thickness variation. The Tukey Honest Significant Difference method has been used to test the differences between the means of the grouping levels. The results of our histo-morphological investigation do not support the suggestion that Caesarean-born children display, on average, a thinner enamel scar compared to children associated to a normal delivery mode. Rather, our study points to the influence exerted by factors intimately related to gestational length variation on the degree of expression of the line. KEY WORDS: HUMAN BIRTH, DELIVERY MODE, GESTATION LENGTH, DECIDUOUS TEETH, DENTAL ENAMEL STRUCTURE, INCREMENTAL MARKERS, NEONATAL LINE.Pre-print version. Visit http://digitalcommons.wayne.edu/humbiol/ after 1 December 2011 to acquire final version. 2The birth process leaves its mark on dental enamel in the form of a ring, an accentuated incremental line called the "Neonatal Line" (NL) (Rushton 1933;Schour 1936). This prominent microfeature, occasionally visible also in the dentine (Schour 1936;Skinner 1992), separates the enamel formed during intrauterine life from that formed after leaving the womb.In modern humans, the NL is usually present in all crowns forming at birth, that is, all the elements of the primary dentition and the first permanent molars (mesiobuccal cusp) (Christensen and Kraus 1965, Deutsch andPe'er 1982;Deutsch et al. 1985;Kraus 1959;Levine et al. 1979). Occasionally, a macroscopic hypoplasia can be detected in correspondence with the NL, but it is usually worn away (Massler et al. 1941;Moss-Salentijn and Hendricks-Klyvert 1985;Schroeder 1991;Skinner 1992).At birth, the enamel is only partially mineralized and continues to increase in thickness by apposition of additional centripetal layers secreted by the ameloblasts at the level of the enamel-dentine junction (EDJ) to a circadian rhythm of 4-5 µm in extant humans (Antoine et al. 2...

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confidence: 99%

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confidence: 99%

“…at least the first 3-7 to 10-15 days ex utero (e.g., Levine et al 1979;Massler and Schour 1946;Schour 1936;Schour and Massler 1937;Weber and Eisenmann 1971;Whittaker and Richards 1978).…”

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Gestation Length, Mode of Delivery, and Neonatal Line-Thickness Variation

Zanolli

Bondioli

Manni³

et al. 2011

Human Biology

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“…This study determined the age at death of skeletal remains, based on a count of enamel cross-striations exposed in longitudinal cross-sections of teeth. Birth is marked to a neonatal line, an accentuated striae of Retzius (Schour, 1936;Weber and Eisenmann, 1971;Whittaker and Richards, 1978), observable in deciduous teeth and first permanent molars. The counting of enamel cross-striations begins adjacent to the group of rods crossing the neonatal line in the first permanent molar and continues to the incisors, canines, and premolars by matching the striae of Retzius among tooth types.…”

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Patterns of ontogeny in human evolution: Evidence from dental development

Mann

Lampl

Monge

1990

Am. J. Phys. Anthropol.

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An understanding of the patterns of maturation that characterize earlier hominines would markedly increase our understanding of human evolution. Earlier reports suggesting that the australopithecines had a pattern of growth and development similar to that of modern humans have been challenged in recent years by a variety of studies. These studies have focused on dental enamel microstructure in attempts to characterize the time frame of enamel calcification. When the latter are combined with data on root development and the sequence of dental calcification and eruption, a picture emerges that attempts to characterize modern human, early hominine,l and ape dental maturation.One of the major features that distinguish modern humans from other hominoids is the increased length of the childhood dependency period. Many writers have looked at this time as an important element in the basic adaptive strategy of humans (Gould, 1976;Dobzhansky, 1962;Mann, 1972;Lovejoy, 1981). A prolonged dependency period provides time for the transmission of complex information about the environment, its resources, and the methods of resource procurement from one generation to another. A lengthened time of dependency can permit the young to internalize information about a number of different, seasonally exploited habitats and the techniques most useful in finding and harvesting the resources in each area. Prolonged dependency also provides time for the young to learn the cues underlying the successful employment of the vast repertoire o f social hehaviorq that govern the peaceful and harmonious interactions of members of a society. It is possible that even the development of language is founded on the lengthened learning period of childhood.The precise biological mechanisms that were modified in the course of human evolution to bring about the prolongation of the dependency period are unknown, although Gould (1976) suggests that a relatively small number of changes in the regulatory genes controlling ontogenetic processes would be all that was necessary. Holloway (1969) has argued that the adaptive value of a prolonged time of maturation need not be directly related to an increase in brain size. In this view, an enlarged parietal association cortex, which he has described in early hominine endocasts (Holloway, 1981(Holloway, , 1983(Holloway, , 1984(Holloway, , 1985 Holloway and Kimbel, 1986; but see 'In this paper, we follow Weiss (1987) and Weiss and Mann (1990) in employing the subfamily IIomininae, rather than the family Hominidae, to describe humans and our close immediate ancestors and relatives. 0 1990 Wiley-Liss, Inc. PHYSICAL, ANTHROPOI,OGY lV0l 33,1990 Falk, 1987, for a contrasting view), would provide the essential neurological foundation for an extended childhood dependency to evolve. An understanding of when the prolonged childhood dependency period appeared in hominine evolution would be extremely useful for our comprehension of human evolution. In 1948 Dart initially suggested that the South African australop...

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Enamel Structure and Properties

Antoine¹,

Hillson²

2015

A Companion to Dental Anthropology

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Microscopy of the neonatal line in developing human enamel

Cited by 66 publications

References 8 publications

Gestation Length, Mode of Delivery, and Neonatal Line-Thickness Variation

Gestation Length, Mode of Delivery, and Neonatal Line-Thickness Variation

Patterns of ontogeny in human evolution: Evidence from dental development

Enamel Structure and Properties

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