Advances in the identification of deciduous molar tooth germs.

In forensic anthropology, correct identification of human deciduous teeth is of paramount importance for age-at-death estimation and relies on detailed anatomical descriptions. Yet literature is scarce on indications: details on the morphology of molar tooth germs of fetuses and newborns, developing from multiple mineralized centers that will eventually coalesce, are scant. This paper presents new anatomical elements for practitioners to identify human molar tooth germs at early developmental stages. 126 deciduous molars from 22 modern skeletons of fetuses and newborns (with a known age-at-death ranging between 0 days and 2 months and 21 days postnatal), without reported or observed dental pathological signs, were selected from the Collezione Antropologica LABANOF (CAL) documented skeletal collection. Gross anatomical descriptions of the morphology and configuration of the centers were provided, considering the number of mineralized centers, the shape and the outline of the occlusal plane at different stages. Three different developmental stages were observed in the maxillary first and second molar and the mandibular first molar, whereas in the mandibular second molar four stages were observed. For each stage, we provide additional detailed morphological descriptions, sketches outlining the shape of the tooth germ, and a picture of the tooth; also, indications for siding the teeth are presented. This information can be used by forensic anthropologists and odontologists for a proper identification when tooth germs are not found in anatomical connection within the dental sockets. Further analyses that encompass more age groups on a larger sample would allow to map the entire crown development of deciduous molars.

Quantitative proteomic analysis of deciduous molars during cap to bell transition in miniature pig.

Taking advantage of genetic manipulation tools and accessibility, almost all molecular knowledge on vertebrate tooth development was obtained from rodent models that only have one dentition in their entire lives. Whether the tooth development in other vertebrates such as swine or human follows the same rules remains elusive. Rodent dentitions differ considerably from human dentitions, therefore limiting the application of knowledge from rodent tooth to human tooth. Signal-mediated communication between cells and complex gene and protein regulatory networks are key components of tooth development. By combining isobaric tandem mass tag (TMT) labeling with liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) technology, we constructed the proteomic profile of deciduous molars at embryonic days 40 and 50 in miniature pig (Sus scrofa). During the ten days of prenatal development of the miniature pig, the morphology of the lower deciduous molar moves from the early cap to the bell stage. Thus, we identified proteins that are associated with these developing stages and identified differentially regulated proteins (DRPs) that are potential or novel drivers of tooth morphogenesis. Three candidate proteins were validated via qRT-PCR, western blotting analysis, and the location of those proteins in tooth germ were observed by immunohistochemical staining. Multiple signaling pathways and protein interaction network revealed potential mechanisms of early tooth programming in a large mammal. Bioinformatic analysis also showed that cross interaction of Wnt and Sonic hedgehog pathways may play a key role in deciduous development during cap to bell transition in miniature pig. SIGNIFICANCE: We performed the most comprehensive study of the whole tooth germ proteome in mammals to date. The high-throughput proteomic analysis identifies differentially regulated proteins and pathways that will help elucidate the mechanisms of tooth development.

New regression formula to estimate the prenatal crown formation time of human deciduous central incisors derived from a Roman Imperial sample (Velia, Salerno, Italy, I-II cent. CE).

The characterization and quantification of human dental enamel microstructure, in both permanent and deciduous teeth, allows us to document crucial growth parameters and to identify stressful events, thus contributing to the reconstruction of the past life history of an individual. Most studies to date have focused on the more accessible post-natal portion of the deciduous dental enamel, even though the analysis of prenatal enamel is pivotal in understanding fetal growth, and reveals information about the mother's health status during pregnancy. This contribution reports new data describing the prenatal enamel development of 18 central deciduous incisors from the Imperial Roman necropolis of Velia (I-II century CE, Salerno, Italy). Histomorphometrical analysis was performed to collect data on prenatal crown formation times, daily secretion rates and enamel extension rates. Results for the Velia sample allowed us to derive a new regression formula, using a robust statistical approach, that describes the average rates of deciduous enamel formation. This can now be used as a reference for pre-industrial populations. The same regression formula, even when daily incremental markings are difficult to visualize, may provide a clue to predicting the proportion of infants born full term and pre-term in an archaeological series.

Prevalence of dental anomalies in deciduous dentition and its association with succedaneous dentition: A cross-sectional study of 4180 South Indian children.

OBJECTIVE: The objective of this study was to estimate the prevalence of dental anomalies in primary dentition of Indian population. MATERIALS AND METHODS: This cross-sectional study was conducted on 4180 children in the age of 2-6 years. Anomalies were classified based on Kreiborg criteria. The term "double tooth" was used to avoid misinterpretation between gemination. and fusion. Patients having radiographs were also examined for associated dental anomalies in permanent dentition. The occurrence and gender prevalence were evaluated using descriptive statistics. RESULTS: About 95. (2.27%) children exhibited at least one dental anomaly. Thirty.seven children showed 51 missing teeth. (0.88%), mostly in lower right incisors with a statistically significant difference between arches. (P = 0.0056) Nine children. (0.21%) had supernumerary teeth commonly in the right maxilla. Two cases of oligodontia. (0.04%) and talon cusps. (0.04%) and one case of triple tooth. (0.02%) were observed. Forty children. (0.95%) had 43 double teeth mostly in the right mandible with a statistically significant difference between the arches. (P = 0.0105). No significant difference was observed based on gender and arch, but they were statistically significant between the right and left sides. (P = 0.018). Among the children with radiographs available, 45% showed anomalies in the succedaneous dentition. CONCLUSIONS: The prevalence rates of children with double tooth, hypodontia, and hyperdontia in our study are 0.95%, 0.88%, and 0.21%, respectively. The overall prevalence rate of anomalies among boys was higher than girls.

Primary tooth size asymmetry in twins and singletons.

OBJECTIVES: To explore asymmetry values of antimeric deciduous tooth crown dimensions in three types of twins: monozygotic (MZ), dizygotic same-sex (DZ) and opposite-sex (OS) vs. single-born controls. SETTING AND SAMPLE POPULATION: Mesiodistal and labio-lingual crown dimensions of second deciduous molars and mesiodistal canine and first molar crown dimensions of 2159 children at 6-12 years of age were evaluated, originating from the US cross-sectional Collaborative Perinatal Study from the 1970s, including altogether MZ (n = 28), DZ same-sex (n = 33) and OS (n = 39) pairs. Single born (n = 1959) were used as controls. MATERIAL AND METHODS: Dental casts were measured for comparison of variance relationships calculated from antimeric teeth, exhibiting fluctuating (FA), and directional (DA) asymmetry using anova. RESULTS: Significant differences appeared in MZ and OS girls in DA of deciduous canines, which gain size in the first and second trimester, and deciduous second molars, which finally stop crown growth during the early post-natal period. Significantly, increased FA values appeared for lower deciduous canines and second molars, indicating greatest environmental stress in OS girls, MZ girls and DZ boys. Twin girls had more fluctuating and directional crown asymmetry than twin boys, but in some dimensions, the twins were more symmetric than controls. CONCLUSIONS: Transmembrane hormonal influence between opposite-sex twins, and late gestational stress factors, caused by placental malfunction and/or monochorionicity, may be involved in asymmetric growth of antimers, during critical periods of crown size gain.

Prenatal factors associated with the neonatal line thickness in human deciduous incisors.

The neonatal line (NNL) is used to distinguish developmental events observed in enamel which occurred before and after birth. However, there are few studies reporting relationship between the characteristics of the NNL and factors affecting prenatal conditions. The aim of the study was to determine prenatal factors that may influence the NNL thickness in human deciduous teeth. The material consisted of longitudinal ground sections of 60 modern human deciduous incisors obtained from full-term healthy children with reported birth histories and prenatal factors. All teeth were sectioned in the labio-lingual plane using diamond blade (Buechler IsoMet 1000). Final specimens were observed using scanning electron microscopy at magnifications 320×. For each tooth, linear measurements of the NNL thickness were taken on its labial surface at the three levels from the cemento-enamel junction. The difference in the neonatal line thickness between tooth types and between males and females was statistically significant. A multiple regression analyses confirmed influence of two variables on the NNL thickness standardised on tooth type and the children's sex (z-score values). These variables are the taking of an antispasmodic medicine by the mother during pregnancy and the season of the child's birth. These two variables together explain nearly 17% of the variability of the NNL. Children of mothers taking a spasmolytic medicine during pregnancy were characterised by a thinner NNL compared with children whose mothers did not take such medication. Children born in summer and spring had a thinner NNL than children born in winter. These results indicate that the prenatal environment significantly contributes to the thickness of the NNL influencing the pace of reaching the post-delivery homeostasis by the newborn's organism.

Neonatal line on fetus and infant teeth: An indicator of live birth and mode of delivery.

BACKGROUND: The neonatal line (NL) is an important issue in forensic odontology. It is the sign of a developmental birth defect, which is caused by the effect of metabolic stress on tooth structures when the fetus passes to extrauterine life. AIMS: The aim of this research is to determine the existence and thickness of NL in teeth, as it is a legal necessity to indicate the signs of viability at birth in a forensic examination of a fetus or infant case. STUDY DESIGN AND SUBJECTS: This research was conducted on 48 lower left and right lateral teeth, which were taken from 24 autopsy cases (46% female and 54% male). Left lateral teeth were sectioned in a vertical plane and right lateral teeth were sectioned in a horizontal plane. The NL thickness was measured with a scanning electron microscope (SEM). These cases comprised three conditions as: 70.3% normal birth, 16.7% caesarean sections, and 12.5% still birth cases under the legal and ethical permission. OUTCOME MEASURES: The mean NL thickness of normal birth cases was higher than caesarean cases as 7.7µm and 2.5µm, respectively. RESULTS AND CONCLUSIONS: The results showed a statistical significance between all birth conditions. NL does not exist in still birth cases (p<0.001). Not only is the presence of NL a sign of live birth, but also its thickness is an indicator of the delivery mode where NL thickness of normal birth was found thicker than the caesarean cases.

Construction of a cDNA library for miniature pig mandibular deciduous molars.

BACKGROUND: The miniature pig provides an excellent experimental model for tooth morphogenesis because its diphyodont and heterodont dentition resembles that of humans. However, little information is available on the process of tooth development or the exact molecular mechanisms controlling tooth development in miniature pigs or humans. Thus, the analysis of gene expression related to each stage of tooth development is very important. RESULTS: In our study, after serial sections were made, the development of the crown of the miniature pigs' mandibular deciduous molar could be divided into five main phases: dental lamina stage (E33-E35), bud stage (E35-E40), cap stage (E40-E50), early bell stage (E50-E60), and late bell stage (E60-E65). Total RNA was isolated from the tooth germ of miniature pig embryos at E35, E45, E50, and E60, and a cDNA library was constructed. Then, we identified cDNA sequences on a large scale screen for cDNA profiles in the developing mandibular deciduous molars (E35, E45, E50, and E60) of miniature pigs using Illumina Solexa deep sequencing. Microarray assay was used to detect the expression of genes. Lastly, through Unigene sequence analysis and cDNA expression pattern analysis at E45 and E60, we found that 12 up-regulated and 15 down-regulated genes during the four periods are highly conserved genes homologous with known Homo sapiens genes. Furthermore, there were 6 down-regulated and 2 up-regulated genes in the miniature pig that were highly homologous to Homo sapiens genes compared with those in the mouse. CONCLUSION: Our results not only identify the specific transcriptome and cDNA profile in developing mandibular deciduous molars of the miniature pig, but also provide useful information for investigating the molecular mechanism of tooth development in the miniature pig.

PKA regulatory subunit expression in tooth development.

Protein kinase A (PKA) plays critical roles in many biological processes including cell proliferation, cell differentiation, cellular metabolism and gene regulation. Mutation in PKA regulatory subunit, PRKAR1A has previously been identified in odontogenic myxomas, but it is unclear whether PKA is involved in tooth development. The aim of the present study was to assess the expression of alpha isoforms of PKA regulatory subunit (Prkar1a and Prkar2a) in mouse and human odontogenesis by in situ hybridization. PRKAR1A and PRKAR2A mRNA transcription was further confirmed in a human deciduous germ by qRT-PCR. Mouse Prkar1a and human PRKAR2A exhibited a dynamic spatio-temporal expression in tooth development, whereas neither human PRKAR1A nor mouse Prkar2a showed their expression in odontogenesis. These isoforms thus showed different expression pattern between human and mouse tooth germs.

Size and shape variability in human molars during odontogenesis.

Under the patterning cascade model (PCM) of cusp development inspired by developmental genetic studies, it is predicted that the location and the size of later-forming cusps are more variable than those of earlier-forming ones. Here we assessed whether differences in the variability among cusps in total and each particular crown component (enamel-dentin junction [EDJ], outer enamel surface [OES], and cement-enamel junction [CEJ]) could be explained by the PCM, using human maxillary permanent first molars (UM1) and second deciduous molars (um2). Specimens were µCT-scanned, and 3D models of EDJ and OES were reconstructed. Based on these models, landmark-based 3D geometric morphometric analyses were conducted. Size variability in both tooth types was generally consistent with the above prediction, and the differences in size variation among cusps were smaller for the crown components completed in later stages of odontogenesis. With a few exceptions, however, the prediction was unsupported regarding shape variability, and UM1 and um2 showed different patterns. Our findings suggested that the pattern of size variability would be caused by temporal factors such as the order of cusp initiation and the duration from the beginning of mineralization to the completion of crown formation, whereas shape variability may be affected by both topographic and temporal factors.

Fetal age estimation using MSCT scans of deciduous tooth germs.

Evaluation of fetal age is an essential element in many fields such as anthropology, odontology, paleopathology, and forensic sciences. This study examines the correlation between fetal age, femoral diaphyseal length (considered as the gold standard), and deciduous tooth germs of fetuses aged 22 to 40 weeks amenorrhea (WA) based on computed tomography (MSCT) reconstructions. Qualitative and quantitative studies of femoral and deciduous tooth germ lengths were performed on 81 fetuses (39 females and 42 males). R software was used for statistical analyses. Intra-observer and inter-observer variabilities and the interclass correlation coefficient (ICC) were calculated. Correlation coefficients (R (2)) and linear regression equations were calculated. Intra- and inter-observer variabilities were very satisfactory (intra-observer ICC ≥ 0.96, inter-observer ICC ≥ 0.95). Femoral length was significantly correlated with age (R (2) = 0.9). The correlation coefficient between age and height, width, and dental volume was R (2) ≥ 0.73. Tooth germs were good indicators of fetal age. Our method appears to be reliable and reproducible, and the results of this study agreed with those of the literature. The dental formula provided a precise estimation of fetal age between 25 and 32 WA. Tooth germs were reliable indicators of fetal age, and multislice computed tomography was shown to be an innovative and reliable technology for this purpose.

Precise chronology of differentiation of developing human primary dentition.

While correlation of developmental stage with embryonic age of the human primary dentition has been well documented, the available information regarding the differentiation timing of the primary teeth was largely based on the observation of initial mineralization and varies significantly. In this study, we aimed to document precise differentiation timing of the developing human primary dentition. We systematically examined the expression of odontogenic differentiation markers along with the formation of mineralized tissue in each developing maxillary and mandibular teeth from human embryos with well-defined embryonic age. We show that, despite that all primary teeth initiate development at the same time, odontogenic differentiation begins in the maxillary incisors at the 15th week and in the mandibular incisors at the 16th week of gestation, followed by the canine, the first primary premolar, and the second primary premolar at a week interval sequentially. Despite that the mandibular primary incisors erupt earlier than the maxillary incisors, this distal to proximal sequential differentiation of the human primary dentition coincides in general with the sequence of tooth eruption. Our results provide an accurate chronology of odontogenic differentiation of the developing human primary dentition, which could be used as reference for future studies of human tooth development.

Stem cells in dental pulp of deciduous teeth.

Dental pulp from deciduous (baby) teeth, which are discarded after exfoliation, represents an advantageous source of young stem cells. Herein, we discuss the methods of deciduous teeth stem cell (DTSC) isolation and cultivation. We show that based on these methods, at least three different stem cell populations can be identified: a population similar to bone marrow-derived mesenchymal stem cells, an epithelial stem-like cells, and/or a mixed population composed of both cell types. We analyzed the embryonic origin and stem cell niche of DTSCs with respect to the advantages they can provide for their future use in cell therapies and regenerative medicine. In vitro and in vivo differentiation of the DTSC populations, their developmental potential, immunological compatibility, tissue engineering, and transplantation use in studies in animal models are also the focus of the current report. We briefly describe the derivation of induced pluripotent stem (iPS) cells from DTSCs, which can be obtained more easily and efficiently in comparison with human fibroblasts. These iPS cells represent an interesting model for the investigation of pediatric diseases and disorders. The importance of DTSC banking is also discussed.

Early morphogenesis of heterodont dentition in minipigs.

The minipig provides an excellent experimental model for tooth morphogenesis because its diphyodont and heterodont dentition resemble that of humans. However, little information is available on the processes of tooth development in the pig. The purpose of this study was to classify the early stages of odontogenesis in minipigs from the initiation of deciduous dentition to the late bell stage when the successional dental lamina begins to develop. To analyze the initiation of teeth anlagens and the structural changes of dental lamina, a three-dimensional (3D) analysis was performed. At the earliest stage, 3D reconstruction revealed a continuous dental lamina along the length of the jaw. Later, the dental lamina exhibited remarkable differences in depth, and the interdental lamina was shorter. The dental lamina grew into the mesenchyme in the lingual direction, and its inclined growth was underlined by asymmetrical cell proliferation. After the primary tooth germ reached the late bell stage, the dental lamina began to disintegrate and fragmentize. Some cells disappeared during the process of lamina degradation, while others remained in small islands known as epithelial pearls. The minipig can therefore, inter alia, be used as a model organism to study the fate of epithelial pearls from their initiation to their contribution to pathological structures, primarily because of the clinical significance of these epithelial rests.

The Spy VI child: a newly discovered Neandertal infant.

Spy cave (Jemeppe-sur-Sambre, Belgium) is reputed for the two adult Neandertal individuals discovered in situ in 1886. Recent reassessment of the Spy collections has allowed direct radiocarbon dating of these individuals. The sorting of all of the faunal collections has also led to the discovery of the remains of a Neandertal child, Spy VI. This individual is represented by two mandibular corpus fragments. The left fragment is the most complete and both sides preserve the mental foramen. Four deciduous teeth are associated with these mandibular remains: three incisors and one canine. The lower left canine (Spy 645a) conjoins with the corresponding alveolar socket in the left part of the mandible. Following extant standards, the developmental stage of the preserved teeth indicate an age at death of about one and a half years. In addition to performing a classical morphometric comparative study of the mandible and teeth, we have evaluated the dental tissue proportions using high-resolution microtomographic techniques. Our results show that Spy VI generally falls within the Neandertal range of variation. However, this specimen also exhibits particular traits, notably in the dental internal structural organization, which reveals that variation in the immature Neandertal variation is larger than what was variation currently represented by the available fossil record. These observations demonstrate the need for investigating the frequency and expression of immature Neandertal traits in fossil anterior teeth, as well as their temporal and geographic variation. Direct radiocarbon dating of the Spy VI specimen has been conducted in two different laboratories. The results of Spy VI confirm the age previously determined for the two adults, making the Spy Neandertal remains the youngest ever directly dated in northwest Europe.

Distribution pattern of cholinesterase enzymes in human tooth germs.

The two distinct molecular forms of cholinesterase (ChE) are acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Our previous studies have reported that ChE is involved in tooth development. However, further experiments are needed to understand the precise action of ChE in tooth development. This study aimed to localise types of ChE in human tooth germs, and identify their distribution pattern. ChE were localised in frozen sections of jaws which were prepared from dead fetuses, neonates and stillborns who were free from visible abnormalities by Karnovsky and Root method. AChE was identified in the inner and outer enamel epithelia including the cervical loop region, stratum intermedium and preameloblasts of tooth germs at bell stage. Secretory ameloblasts were free from staining. The bud and cap stages of permanent tooth germs showed AChE activity on the lingual aspect and top surface of the epithelial ingrowths, respectively. BuChE activity was localised in the degenerating dental lamina. Our study reported the first evidence of localisation of ChE in human tooth development and identified the possible molecular form of ChE in tooth germs as AChE. Also, our results have provided strong evidence to speculate the action of AChE is on the cells of enamel organ during tooth development.

Importância da manutenção de espaço em odontopediatria / Importance of space maintenance in pediatric dentistry

A manutenção de espaço para a erupção dos dentes sucessores permanentes durante as fases de dentição decídua e ista é importante para o desenvolvimento normal da oclusão. Entretanto, a perda prematura de dentes decíduos pode levar a perda de espaço, dependendo de alguns fatores, dentre eles, a idade do peciente, o estágio de desenvolvimento dental, o dente perdido, a presença de apinhamento ou espaçamento no arco e a relação oclusal. Na região ântero-superior, a manutenção de espaço se faz necessária para preencher os rrquisitos estéticos, funcionais e psicológicos, não havendo preocupação direta com a perda de espaço. Por outro lado, na região ântero-inferior e posterior os mantenedores de espaço são indispensáveis para evitar o comprometimento do espaço presente para a erupção dos dentes permanentes sucessores. O objetivo deste trabalho é discorrer sobre as consequências da perda precoce de dentes decíduos e permanentes, revisar as justificativas para a manutenção de espaço e os aparelhos indicados nas diferentes situações clínicas.

Arco lingual de Nance e mola de secção aberta na perda precoce de dente decíduo / Lingual Arch of Nance and spring of open section in the premature loss of deciduous teeth

A perda de dente decíduo antes de sua esfoliação natural pode gerar consequencias ao desenvolvimento da oclusão futura por ruptura do equilíbrio dentário. Para o controle da movimentação indesejável do dentes adjacentes ao espaço deixado pelo dente decíduo, dispõe-se de aparelhos mantenedores de espaço. Enquanto os aparelhos recuperadores de espaços são dispositivos dinâmicos utilizados quando o diâmetro mésio-distal do arco, destinado ao dente permanente em fase de erupção, foi perdido parcialmente. Este trabalho tewm o intuito de relatar o caso clínico de uma paciente de 8 anos de idade, que compareceu a clínica de Odontopediatria da Universidade Federal da Paraíba para atendimento odontológico de rotina. Verificou-se a necessidade de exodontia do elemento 85, devido à presença da lesão cariosa extensa e mobilidade dentária. Diante da perda precoce do elemento supracitados e dos elementos 75 e 84, que haviam sido anteriormente extraídos, optou-se pela instalação de um aparelho mantenedor de espaço, arco lingual de Nance. A erupção precoce e não orientada do elemento 34 gerou perda de espaço para a erupção do 35, confeccionando-se então um recuperador de espaço, utilizando-se mola de secção aberta.