Size, ultrastructure, and microhardness of natal teeth with agenesis of permanent successors.

OBJECTIVE: Natal and neonatal teeth may occur in conjunction with other oral anomalies, including anomalous development of succedaneous teeth. Our purpose was to examine the size, ultrastructure, and microhardness of two natal teeth without permanent successor germs, and compare them with the characteristics of normal primary teeth. DESIGN: The dimensions of two natal mandibular incisors extracted from a healthy 7-year-old child were measured with a digital sliding caliper. The crown dimensions of normal primary mandibular central incisors were established from dental casts of 102 children. Since the natal teeth were nearly completely devoid of enamel, the average enamel thickness determined on a sample of 19 normal primary mandibular incisors was added to the values measured. External surfaces and transverse sections of the natal teeth were examined under a scanning electron microscope. Vickers microhardness of radicular dentine was assessed for the natal teeth and for 11 normal primary mandibular incisors. RESULTS: Only remnants of enamel were present. All crown dimensions corrected for enamel loss were within the normal range. The ultrastructure of hard dental tissues was normal. The radicular dentine hardness of the natal teeth was similar to that of the normal primary mandibular incisors. CONCLUSIONS: The results indicate that the natal teeth were prematurely erupted regular primary mandibular central incisors. In our case, the occurrence of natal teeth associated with agenesis of their primary successors appears to be related to an accelerated or premature pattern of dental development, rather than to superficial positioning of the tooth germs.

Isolation and in vitro characterisation of dental pulp stem cells from natal teeth.

Dental pulp stem cells were primarily derived from the pulp tissues of exfoliated deciduous teeth, primary incisors and permanent third molar teeth. The aim of this study was to isolate and extensively characterise SCs derived from human natal dental pulp (hNDP). For characterisation, proliferation capacity, phenotypic properties, ultrastructural and differentiation characteristics and gene expression profiles were utilised. A comparison was done between the properties of NDP-SCs and the properties of mesenchymal stem cells (MSCs) from bone marrow (BM) of the human. Stem cells isolated from hNDP and hBM were analysed by flow cytometry, reverse transcriptase-PCR, Real Time-PCR, and immunocytochemistry. Both cell lines were directionally differentiated towards adipogenic, osteogenic chondrogenic, myogenic and neurogenic lineages. hNDP-SCs and hBM-MSCs expressed CD13, CD44, CD90, CD146 and CD166, but not CD3, CD8, CD11b, CD14, CD15, CD19, CD33, CD34, CD45, CD117, and HLA-DR. Ultrastructural characteristics of hNDP-SCs showed more developed and metabolically active cells. hNDP-SCs and hBM-MSCs expressed some adipogenic (leptin, adipophilin and PPARgamma), myogenic (desmin, myogenin, myosinIIa, and alpha-SMA), neurogenic (gamma-enolase, MAP2a,b, c-fos, nestin, NF-H, NF-L, GFAP and betaIII tubulin), osteogenic (osteonectin, osteocalcin, osteopontin, Runx-2, and type I collagen) and chondrogenic (type II collagen, SOX9) markers without any stimulation towards differentiation under basal conditions. Embryonic stem cell markers Oct4, Rex-1, FoxD-3, Sox2, and Nanog were also identified. The differentiation potential of hNDP-SCs and hBM-MSCs to adipogenic, osteogenic, chondrogenic, myogenic and neurogenic was shown. This report described the first successful isolation and characterisation of hNDP-SCs.

Clinical and ultrastructural study of natal and neonatal teeth.

The present study was undertaken to evaluate the surface topography of mandibular natal and neonatal incisors at the ultrastructural level using the scanning electron microscope (SEM). The enamel of the teeth exhibited hypoplastic, depressed areas and the incisal edge of natal tooth lacked enamel. In addition, root formation of the teeth was not completed, which correlated with findings that teeth may erupt without root formation.

Natal teeth in cleft lip and palate patients: a scanning electron microscopy study.

Natal and neonatal teeth may occur in patients up to 30-days after birth. The presence of two neonatal teeth in cleft lip and palate patients is reported in this study describing the structural aspects of the enamel and the dentin, using scanning electron microscopy.

[Natal and postnatal teeth: their enamel]. / Dents natale et post-natale: leur émail.

The enamel of a natal tooth in a healthy full-term child and the enamel of a postnatally erupted tooth in a premature child have been studied with scanning electron microscopy on longitudinal and cross sections. The first case shows that following a normal development, amelogenesis was arrested. This is evident by the presence of the external aprismatic layer in spite of the narrowness of the enamel which corresponds to about a third of the normal thickness. This premature arrest of amelogenesis can be dated to about the 6th month "in utero". In the second case we observed a reversible amelogenesis disturbance as attested by the absence of the external aprismatic layer as well as by a new and fast enamel apposition that took a pseudonormal course. Happening about 10 weeks before birth, this disturbance has probably been induced by factors of maternal origin. In both cases, the eruption anomaly was associated with an enamel anomaly. These observations open new perspectives in the study of natal and neonatal teeth. By extension, such observations are likely to produce complementary informations in neonatology.

A scanning electron microscopic study of the enamel of neonatal teeth.

Neonatal teeth, two mandibulars incisors and one maxillary central incisor, from two separate patients were examined, by SEM. Besides typical enamel anomalies, the incisors exhibited partial or total absence of root formation. These findings suggest that the early eruption of natal and neonatal teeth is dependent on osteoblastic activity within the area of the tooth germ. The reported cases show that teeth may erupt without root formation and without periodontal ligament which correlate with the role of the dental follicle during tooth eruption.