Tooth Formation Research Articles

Periderm fate and independence of tooth formation are conserved across osteichthyans

BackgroundPrevious studies have reported that periderm (the outer ectodermal layer) in zebrafish partially expands into the mouth and pharyngeal pouches, but does not reach the medial endoderm, where the pharyngeal teeth develop. Instead, periderm-like cells, arising independently from the outer periderm, cover prospective tooth-forming epithelia and are crucial for tooth germ initiation. Here we test the hypothesis that restricted expansion of periderm is a teleost-specific character possibly related to the derived way of early embryonic development. To this end, we performed lineage tracing of the periderm in a non-teleost actinopterygian species possessing pharyngeal teeth, the sterlet sturgeon (Acipenser ruthenus), and a sarcopterygian species lacking pharyngeal teeth, the axolotl (Ambystoma mexicanum).ResultsIn sturgeon, a stratified ectoderm is firmly established at the end of gastrulation, with minimally a basal ectodermal layer and a surface layer that can be homologized to a periderm. Periderm expands to a limited extent into the mouth and remains restricted to the distal parts of the pouches. It does not reach the medial pharyngeal endoderm, where pharyngeal teeth are located. Thus, periderm in sturgeon covers prospective odontogenic epithelium in the jaw region (oral teeth) but not in the pharyngeal region. In axolotl, like in sturgeon, periderm expansion in the oropharynx is restricted to the distal parts of the opening pouches. Oral teeth in axolotl develop long before mouth opening and possible expansion of the periderm into the mouth cavity.ConclusionsRestricted periderm expansion into the oropharynx appears to be an ancestral feature for osteichthyans, as it is found in sturgeon, zebrafish and axolotl. Periderm behavior does not correlate with presence or absence of oral or pharyngeal teeth, whose induction may depend on ‘ectodermalized’ endoderm. It is proposed that periderm assists in lumenization of the pouches to create an open gill slit. Comparison of basal and advanced actinopterygians with sarcopterygians (axolotl) shows that different trajectories of embryonic development converge on similar dynamics of the periderm: a restricted expansion into the mouth and prospective gill slits.

Induction of human stem cells into ameloblasts by reaggregation strategy

BackgroundHuman epithelium-derived stem cells and induced pluripotent stem cells (hiPSCs) possess the capability to support tooth formation and differentiate into functional enamel-secreting ameloblasts, making them promising epithelial-component substitutes for future human tooth regeneration. However, current tissue recombination approaches are not only technically challenging, requiring precise induction procedures and sophisticated microsurgery, but also exhibit low success rates in achieving tooth formation and ameloblastic differentiation.MethodsSuspended human keratinocyte stem cells (hKSCs) or cells from three hiPSC lines were directly mixed with dissociated embryonic mouse dental mesenchymal cells (mDMCs) that possess odontogenic potential in different proportions and reaggregated them to construct bioengineered tooth germs. The success rates of tooth formation and ameloblastic differentiation were confirmed after subrenal culture. The sorting capability, sequential development, and ameloblastic differentiation of stem cells were examined via GFP tracing, RT-PCR, and histological analysis, respectively.ResultsOur reaggregation approach achieved an impressive success rate of more than 90% in tooth formation and 100% in ameloblastic differentiation when the chimeric tooth germs contained 1%~10% hKSCs or 5% hiPSCs. In addition, we observed that hiPSCs, upon exposure to mDMCs, initially transformed into epidermal cells, as indicated by KRT14 and CD29 expression, before progressing into dental epithelial cells, as indicated by SP6 and SHH expression. We also found that epithelial-derived hiPSCs, when reaggregated with mDMCs, were more favorable for tooth formation than their mesenchymal-derived counterparts.ConclusionsThis study establishes a simplified yet highly effective cell-cell reaggregation strategy for inducing stem cells to support tooth formation and differentiate into functional ameloblasts, paving the way for novel approaches for the development of stem cell-based tooth organoids and bioengineered tooth germs in vitro.

Immune proteins recovered in tooth enamel as a biochemical record of health in past populations: Paleoproteomic analysis of Mission Period Native Californians

The enamel proteome includes a range of proteins that are well-preserved in archaeological settings but have so far received less study than those associated with sex-estimation of enamel. We look beyond sex-specific sequencing of amelogenin to investigate the potential of several serum proteins, including immunoglobulin gamma (IgG), the major immunoglobulin found in blood serum, and C-reactive protein (CRP), which is associated with inflammatory response, to provide insight into the health and stresses experienced by individuals in the past. We apply this approach to enamel samples from Mission-Period ancestral Ohlone interred at Asistencia San Pedro y San Pablo (CA-SMA-71/H; n = 11). For comparison, we also examine enamel from historic-period European-Americans interred in the City Cemetery in San Francisco (n = 12), and extracted third molars from present-day military cadets (n = 8). Results indicate that IgG is elevated among individuals at the asistencia relative to samples from present-day military cadets, and historic City Cemetery individuals (ANOVA with post-hoc Tukey Kramer tests, p < .02). Further, the inflammatory protein CRP, normally expressed at much lower levels than IgG, was present in 55% (6 of 11) of the asistencia samples, and in 17% (2 of 12) of the historic City Cemetery samples, but was not detected in enamel samples from present-day military cadets. While more studies are needed, we argue that the difference in IgG could reflect higher levels of chronic diseases such as tuberculosis among Ohlone living within the Mission system, and the presence of measurable amounts of CRP could relate to higher degrees of physical, social, and emotional stresses. To our knowledge, this is the first paleoproteomic study of immune proteins in tooth enamel. The ability to track immune responses during tooth formation could provide valuable and high-resolution information on ancient health and disease at the level of the individual over archaeological time-scales.

Abutment Tooth Formation Simulator for Naked-Eye Stereoscopy

Virtual reality is considered to be useful in improving procedural skills in dental education, but systems using wearable devices such as head-mounted displays (HMDs) have many problems in terms of long-term use and hygiene, and the accuracy of stereoscopic viewing at close ranges is inadequate. We developed an abutment tooth formation simulator that utilizes a display (spatial reality display—SRD) to precisely reproduce 3D space with naked-eye stereoscopic viewing at close range. The purpose of this was to develop and validate the usefulness of an abutment tooth formation simulator using an SRD. A 3D-CG (three-dimensional computer graphics) dental model that can be cut in real time was output to the SRD, and an automatic quantitative scoring function was also implemented by comparing the cutting results with exemplars. Dentists in the department of fixed prosthodontics performed cutting operations on both a 2D display-based simulator and an SRD-based simulator and conducted a 5-point rating feedback survey. Compared to the simulator that used a 2D display, the measurements of the simulator using an SRD were significantly more accurate. The SRD-based abutment tooth formation simulator received a positive technical evaluation and high dentist satisfaction (4.37), suggesting its usefulness and raising expectations regarding its future application in dental education.

Fgf9 promotes incisor dental epithelial stem cell survival and enamel formation

BackgroundUnderstanding the role of cytokines in tooth development is critical for advancing dental tissue engineering. Fibroblast growth factor 9 (FGF9) is the only FGF consistently expressed throughout dental epithelial tissue, from the initiation of tooth bud formation to tooth maturation. However, mice lacking Fgf9 (Fgf9−/−) surprisingly show no obvious abnormalities in tooth development, suggesting potential compensation by other FGFs. Here we report findings from an Fgf9S99N mutation mouse model, a loss-of-function mutation with a dominant negative effect. Our study reveals that Fgf9 is crucial for dental epithelial stem cell (DESC) survival and enamel formation.MethodsTo dissect the role of Fgf9 in tooth development, we performed the micro-CT, histomorphological analysis and gene expression assay in mice and embryos with S99N mutation. In addition, we assessed the effect of FGF9 on the DESC survival and dental epithelial differentiation by DESC sphere formation assay and tooth explant culture. Cell/tissue culture methods, gene expression analysis, specific inhibitors, and antibody blockage analysis were employed to explore how Fgf9 regulates enamel differentiation and DESC survival through both direct and indirect mechanisms.ResultsThe Fgf9S99N mutation in mice led to reduced ameloblasts, impaired enamel formation, and increased apoptosis in the cervical loop (CL). DESC sphere culture experiments revealed that FGF9 facilitated DESC survival via activating ERK/CREB signaling, without affecting cell proliferation. Furthermore, in vitro tissue culture experiments demonstrated that FGF9 promoted enamel formation in a manner dependent on the presence of mesenchyme. Interestingly, FGF9 stimulation inhibited enamel formation in isolated enamel epithelia and DESC spheres. Further investigation revealed that FGF9 supports DESC survival and promotes amelogenesis by stimulating the secretion of FGF3 and FGF10 in dental mesenchymal cells via the MAPK/ERK signaling pathway.ConclusionsOur study demonstrates that Fgf9 is essential for DESC survival and enamel formation. Fgf9 performs as a dual-directional regulator of the dental enamel epithelium, not only inhibiting DESC differentiation into ameloblasts to preserve the stemness of DESC, but also promoting ameloblast differentiation through epithelial-mesenchymal interactions.

DENTAL AGENESIS OF UPPER LATERAL INCISORS: Case report in a patient from the city of Mato Verde - MG

Dental agenesis or also known as hypodontia, is established as a numerical anomaly that implies a lack of tooth development. The most frequently encountered agenesis, with the exception of third molars, is the upper lateral incisors. The objective of this study was to report a clinical case of agenesis of upper lateral incisors in a patient from the city of Mato Verde-MG. This is a qualitative study with observational/descriptive objectives. The research will be carried out in the municipality of Mato Verde-MG at Faculdade Verde Norte (FAVENORTE). Female patient, Caucasian, ten years old, attended the FAVENORTE clinic, together with her guardian, with the main complaint being: “Assessing the formation of permanent teeth, as she had already been diagnosed with agenesis of the deciduous upper lateral incisors”. On clinical examination it was observed that there was a lack of permanent upper lateral incisors. The radiographic examination confirmed the absence of the germs of the permanent upper lateral incisors, thus confirming the agenesis of these dental elements. Therefore, the patient was referred to the orthodontist, who prepared an individualized treatment plan for the patient. Early diagnosis is extremely important in cases of tooth agenesis, where professionals must pay attention to its characteristics, targeting treatment options for each case, thus obtaining a favorable prognosis and a better quality of life for the patient.

Double Teeth and Coexistent Anomalies: Examples From Continental Africa.

Whether gemination or fusion, double teeth are rare worldwide, including Africa based on few published data. New cases from the continent are tallied, and anomalies potentially associated with double teeth are identified. These findings should interest a range of dental researchers. The presence of double teeth was recorded in 97 modern and premodern North and sub-Saharan African samples (5631 inds.). They and coexistent anomalies are described relative to published examples. Prevalence was estimated as possible, using a Poisson model for 95% confidence intervals (CI). Three maxillary double teeth were identified: a primary left lateral incisor in a Nubian child (1938-1756 BC), permanent left central incisor in an adult Egyptian (3650-3500 BC), and permanent right central incisor in a modern (19th century) adult from Guinea. Each co-occurs, respectively, with a talon cusp, peg lateral incisor and, in the latter individual, second premolar crown variation with rotation, and third molar dens evaginatus. Double tooth prevalence is 0.048% (CI 0.001%-0.270%), with regional variation, in premodern, and 0.000% in modern North Africans. It is 0.000% for premodern and 0.048% for modern sub-Saharan Africans (0.008%-1.714%). The double incisors are comparable to other global examples, indicative of common developmental processes during odontogenesis. Prevalence is lower than published modern rates, to suggest some exceptionality in Africans as reported earlier for other dental variants. Finally, though circumstantial, double teeth and accompanying anomalies may share an etiology. Continuing research overall, and in Africa specifically, will promote an improved understanding of double teeth formation and expression.

Development and eruption of human teeth in the Chinese population: a comprehensive dental atlas

AimThe first comprehensive chart on dental development was published 75 years ago based on Caucasian children and this has been used as a standard dental chart to date. Few population specific charts have been developed recently and updated dental charts on modern subjects can provide more information on dental development patterns. This study aims to construct a comprehensive dental atlas for modern Chinese children and young adults to assist in clinical, forensic, and public health applications.MethodsThe study sample comprised of 2,306 subjects, age ranging from 2 to 24 years belonging to Chinese ethnicity. Dental formation and eruption of permanent teeth and resorption of primary teeth were analyzed separately for females and males. For each age range, the number of teeth (n), and the stage of development was calculated for first (Q1), second (Q2) and third quartiles (Q3). Similar analysis was performed for the position of permanent teeth and the resorption of primary teeth. To determine the variations between the sex, Mann-Whitney U-test was conducted by comparing the median (Q2) stages.ResultsVariations in dental formation and eruption of permanent teeth and resorption of primary teeth were observed between maxillary and mandibular dentitions and between the sex, however the difference was not statistically significant (p = 0.535 to p = 1.000). The dental atlas was presented separately for Chinese females and males.ConclusionThis atlas on modern Chinese population serves as a practical tool to assist in clinical diagnosis and treatment planning, in forensic investigations as well as indicators of developments in public health.

A finite element analysis on the indication for extracting partially impacted mandibular third molars considering mandibular trauma

BackgroundPatients presenting with partially impacted lower third molars (M3) have a higher likelihood of experiencing angle fractures while simultaneously decreasing the risk of condylar fractures. However, the specific biomechanical mechanism responsible for this occurrence remains unclear. Moreover, there is an ongoing debate regarding whether the removal of M3s might actually increase the risk of condylar fractures. This study aimed to evaluate how the presence of M3s influences mandibular fractures resulting from blows to the symphysis and lateral mandibular body, and to determine the indication for extracting M3s in such cases.MethodsModels of the mandible with a partially M3-impacted model (M3I), M3-extracted model (M3E), and M3-absent model (M3A) were generated using a computer. A traumatic blown force of 2000 N was applied to the symphysis and the right body of the mandible. Von Mises and principal stresses were analyzed, and failure indexes were determined. Two cases of mandibular linear fractures were chosen for model verification and interpretation.ResultsWhen force was applied to the symphysis, the condylar region exhibited the highest stress levels, while stress in the mandibular angle region was much less regardless of the M3 state. On applying the force to the right mandibular body, stress in the condylar region decreased while stress in the mandibular body increased, especially in the blown regions. Impacted tooth or cavity formation post-M3 extraction led to uneven stress distribution on the blown side of the mandible, increasing the risk of mandibular angle fractures. In cases where M3 was absent or the extraction socket had healed, stress from lateral traumatic blown force was evenly distributed along both the inner and outer oblique lines of the mandible, thereby reducing the risk of mandibular fractures.ConclusionsThe reduced risk of condylar fractures in patients with partially impacted lower M3s and mandibular angle fractures is mainly due to lateral blows on the mandible, which generate less stress in the condylar region than blows on the mandibular symphysis, rather than being caused by the M3 itself. Extraction of the lower M3 can decrease the risk of mandibular fractures, with a minor influence on condylar fractures.

Region-specific gene expression profiling of early mouse mandible uncovered SATB2 as a key molecule for teeth patterning

Mammalian dentition exhibits distinct heterodonty, with more simple teeth located in the anterior area of the jaw and more complex teeth situated posteriorly. While some region-specific differences in signalling have been described previously, here we performed a comprehensive analysis of gene expression at the early stages of odontogenesis to obtain complete knowledge of the signalling pathways involved in early jaw patterning. Gene expression was analysed separately on anterior and posterior areas of the lower jaw at two early stages (E11.5 and E12.5) of odontogenesis. Gene expression profiling revealed distinct region-specific expression patterns in mouse mandibles, including several known BMP and FGF signalling members and we also identified several new molecules exhibiting significant differences in expression along the anterior–posterior axis, which potentially can play the role during incisor and molar specification. Next, we followed one of the anterior molecules, SATB2, which was expressed not only in the anterior mesenchyme where incisor germs are initiated, however, we uncovered a distinct SATB2-positive region in the mesenchyme closely surrounding molars. Satb2-deficient animals demonstrated defective incisor development confirming a crucial role of SATB2 in formation of anterior teeth. On the other hand, ectopic tooth germs were observed in the molar area indicating differential effect of Satb2-deficiency in individual jaw regions. In conclusion, our data provide a rich source of fundamental information, which can be used to determine molecular regulation driving early embryonic jaw patterning and serve for a deeper understanding of molecular signalling directed towards incisor and molar development.

Tracking Childhood Lead Exposure in Early Industrial Romanians

Childhood lead exposure has been linked to severe adverse health outcomes throughout life. Measurements of lead in teeth have established that individuals living in contaminated environments show higher levels compared to individuals living further away, although less is known about when individuals are most susceptible to these exposures. We examined lead (Pb208) concentrations (ppm) in teeth over the first 2.5 years of life in 16 children born in the late 19th to early 20th century throughout Romania. This period of intense industrialization was characterized by increases in mining, coal burning, and oil refining—activities that contaminate air, water, and food with Pb. We hypothesized the distance from an operational mine or oil refinery, or being born in a city, would be positively associated with cumulative dentine Pb exposure (CDPE). We also predicted that Pb exposures would peak in the first six months of life when gastrointestinal (GI) absorption of Pb is likely highest. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) of sectioned tooth dentine followed by Bayesian statistical analyses revealed that living 30 km or more from a mine or oil refinery did not explain CDPE. However, being born in a city explained 42% of CDPE. All individuals showed maximum Pb exposures after six months of age, likely due to contaminated solid food and/or non-milk liquids. This research demonstrates how tooth formation can be coupled with comprehensive elemental mapping to analyse the context and timing of early-life neurotoxicant exposures, which may be extended to well-preserved teeth from clinical and historic populations.

Apexification treatment on tooth with a history of trauma: A case report

Background: Traumatic dental injuries to the teeth may result in pulpal and periapical disease. Most dental traumas occur in the 7 -10-year-old age group with incomplete apical root development. Apexification is the procedure to close the apex using bioactive material to create an apical plug. MTA can be used as a material of choice to treat open apex. Purpose: To perform an apexification of open apex with MTA apical plug. Case: A 30-year-old female patient with a chief complaint to fix her missing anterior filling and blackened tooth. The tooth had a history of trauma when the patient was 7 years old. One year ago, the tooth had intermittent pain so the tooth was treated and filled by another dentist. Case Management: Access opening is performed and apical gauging is determined. Then, working length was established. Debridement was done with H-file #80. Irrigation sequence with NaOCl 1,5% - Aquadest – EDTA 17% -aquadest. Ca(OH)2 dressing was given and temporary restoration was placed. On the second visit, temporary restoration was removed, followed by a root canal filled with MTA 3 mm from the apex using MAP carrier then confirmed with a radiograph. Conclusion: Trauma that occurs during tooth formation may cause an open apex that is treatable using an MTA plug.

Resilience of the replacing dentition in adult reptiles

The dentition is critical to animal survival and teeth are present in modern vertebrates including teleost fish, sharks, amphibians, mammals and reptiles. The developmental processes that give rise to teeth are not just preserved through evolution but also share high level of similarity with the embryogenesis of other ectodermal organs. In this review we go beyond the embryonic phase of tooth development to life-long tooth replacement. We will address the origins of successional teeth, the location of putative tissue-resident stem cells, how de novo tooth formation continues throughout life and how teeth are shed in a spatially and temporally controlled manner. We review the evidence that the dental epithelium, which is the earliest recognizable dental structure in the reptilian dentition, serves as a putative niche for tissue-resident epithelial stem cells and recent molecular findings from transcriptomics carried out in reptilian dentitions. We discuss how odontoclasts resorb the primary tooth allowing eruption of the successional tooth. The reptiles, particularly lizards, are emerging as some of the most accessible animals to study tooth replacement which has relevance to evolution of the dentition and human dental disorders.

ACUTE KIDNEY INJURI OF PATIENTS WITH ACUTE MIOCARD INFARCTION

Aim of research – the comparative analysis of the frequency and the identification of factors for the development of acute kidney injury (AKI) in patients with myocardial infarction (MI) with and without the formation of pathologic Q-tooth. Material and methods. The total of 134 patients were studied and divided into 2 groups: Group 1 – patients with coronary heart disease (CHD) MI with pathologic Q tooth formation (n = 29); Group 2 – CHD MI patients without Q tooth formation (n = 105). Inclusion criteria are first-ever MI, age older than 18 years, increase in serum creatinine level above 26.5 μmol/l within 48 hours and decrease in diuresis less than 0,5 ml/ kg/h, informed voluntary consent for participation in the study. Exclusion criteria are terminal chronic renal failure, age under 18 years, chronic heart failure with left ventricular ejection fraction (LVEF) below 40%, MI anamnesis, refusal to participate in the study. Results. Among 134 patients with MI, signs of AKI were detected in 40 (29,9%) patients. In group 1, the mean value of glomerular filtration rate (GFR) was 41,0 ± 8,2, in group 2 it was 73,2 ± 13,9 ml/min/1,73m2. Signs of AKI in group 1 were observed in 20 (69,0%) patients, in group 2 in 20 (19,0%) patients. The comparative analysis of the study groups revealed that group 1 patients, compared to group 2 patients, had higher body mass index (BMI)(p &lt; 0,001), more often concomitant chronic kidney disease (CKD) was observed (p &lt; 0,001), lower hemoglobin level was typical (p &lt; 0,001), and arterial hypotension was noted at prehospital stage (p = 0,034). In addition, group 1 patients were more likely to develop complications such as bleeding at the site of arterial puncture during percutaneous coronary intervention (PCI) (p &lt; 0,046), pulmonary edema (p &lt; 0,001) and cardiogenic shock (CS) (p &lt; 0,001). The length of stay of group 1 patients in the Intensive Therapy and Resuscitation Department was 11,5 ± 3,6 bed days, group 2 was 9,6 ± 3,9 bed days (p &lt; 0,019), and 8 (27,6%) patients and 1 (1,1%) died, respectively (p &lt; 0,001). Conclusion. Early signs of AKI were detected in 29,9% of patients with MI; this condition was more frequent in the group of patients with MI who had a formed pathologic Q wave (69%). High BMI (p = 0,02), increased blood levels of HDL (p &lt; 0,006) and total cholesterol (p &lt; 0,001), decreased blood hemoglobin (p = 0,001), arterial hypotension (p = 0,013) and initial CKD (p &lt; 0,001) were the factors contributing to the development of AKI.

Study on histological features and &lt;i&gt;Bmp4&lt;/i&gt; expression pattern during tooth formation and replacement in &lt;i&gt;Xenopus&lt;/i&gt; laevis

Study on histological features and &lt;i&gt;Bmp4&lt;/i&gt; expression pattern during tooth formation and replacement in &lt;i&gt;Xenopus&lt;/i&gt; laevis

Perbedaan Tingkat Keakuratan Estiemasi Usia Menggunakan Metode Al-Qahtani Dan Metode Cameriere Pada Gambaran Radiografi Panoramik

Radiography can be used at prenatal age because at this age we can see and assess the stage of formation and development of primary teeth that have not yet erupted. The London Atlas method is well-organized, comprehensive, and evidence-based using tooth development and alveolar eruption. The method for determining chronological age based on open apex measurements was first introduced by Roberto Cameriere. This method looks at the development of the seven permanent teeth of the lower left jaw. Research objective: To determine the difference in the level of accuracy of age estimation using the Al-Qahtani method and the Cameriere method on panoramic radiography images. Materials and Methods: This research design uses analytical observational with a cross sectional research design. The statistical test used is the paired t-test. Results: Based on the results of this study, it is known that the difference in average age in the Al-Qahtani method is that the tooth age is 0.6 years older than the chronological age and in the Cameriere method the tooth age is 0.59 years older than the chronological age. Conclusion: The results of this study show that there are not differences in age estimation using the Al-Qahtani method and the Cameriere method on panoramic radiography images.

Strontium isotopes track female dispersal in Taï chimpanzees.

Chimpanzees (Pan troglodytes) are patrilocal, with males remaining in their natal community and females dispersing when they reach sexual maturity. However, the details of female chimpanzee dispersal, such as their possible origin, are difficult to assess, even in habituated communities. This study investigates the utility of 87Sr/86Sr analysis for (1) assessing Sr baseline differences between chimpanzee territories and (2) identifying the status (immigrant or natal) of females of unknown origin within the territories of five neighboring communities in Taï National Park (Côte d'Ivoire). To create a local Sr isoscape for the Taï Chimpanzee Project (TCP) study area, we sampled environmental samples from TCP-established territories (n = 35). To assess dispersal patterns, 34 tooth enamel samples (one per individual) were selected from the Taï chimpanzee skeletal collection. 87Sr/86Sr analysis was performed on all 69 samples at the W.M. Keck Lab. The theoretical density and overlap of chimpanzee communities as well as generalized linear mixed models (GLMMs) were used to test each question. 87Sr/86Sr ratios for natal male chimpanzees ranged from 0.71662 to 0.72187, which is well within the corresponding environmental baseline range of 0.70774-0.73460. The local Sr isoscapes fit was estimated with the root-mean-square error value, which was 0.0048 (22% of the whole 87Sr/86Sr data range). GLMMs identified significant differences in 87Sr/86Sr ratios between natal and unknown North community origin groups, suggesting that after 1980, females of unknown origin could be immigrants to North community (n = 7, z-ratio = -4.08, p = 0.0001, power = 0.94). This study indicates that 87Sr/86This study indicates that 87Sr/86Sr analysis can successfully identify immigrant females in skeletal collections obtained from wild chimpanzee communities, enabling the tracking of female dispersal patterns historically. There are, however, significant limitations within the scope of this study, such as (1) the absence of reliable maps for the TCP study area, (2) limited capacity for environmental sampling, (3) small sample sizes, and (4) tooth formation in wild chimpanzees.

Dynamic microvilli sculpt bristles at nanometric scale

Organisms generate shapes across size scales. Whereas patterning and morphogenesis of macroscopic tissues has been extensively studied, the principles underlying the formation of micrometric and submicrometric structures remain largely enigmatic. Individual cells of polychaete annelids, so-called chaetoblasts, are associated with the generation of chitinous bristles of highly stereotypic geometry. Here we show that bristle formation requires a chitin-producing enzyme specifically expressed in the chaetoblasts. Chaetoblasts exhibit dynamic cell surfaces with stereotypical patterns of actin-rich microvilli. These microvilli can be matched with internal and external structures of bristles reconstructed from serial block-face electron micrographs. Individual chitin teeth are deposited by microvilli in an extension-disassembly cycle resembling a biological 3D printer. Consistently, pharmacological interference with actin dynamics leads to defects in tooth formation. Our study reveals that both material and shape of bristles are encoded by the same cell, and that microvilli play a role in micro- to submicrometric sculpting of biomaterials.

Unraveling the structure, chemical composition, and conserved signaling in leech teeth

ABSTRACT Unlike vertebrates, the number of toothed taxa in invertebrates is very few, with leeches being the only tooth-bearing organisms in the phylum Annelida. Copious studies have been conducted regarding vertebrate teeth; however, studies regarding the structure and function of invertebrate teeth are limited. In this study, the tooth structure of leeches, specifically Hirudo nipponia and Haemadipsa rjukjuana, was revealed, which showed sharp and pointed teeth along the apex of three jaws. Understanding conserved signaling regulations among analogous organs is crucial for uncovering the underlying mechanisms during organogenesis. Therefore, to shed light on the evolutionary perspective of odontogenesis to some extent, we conducted de novo transcriptome analyses using embryonic mouse tooth germs, Hirudo teeth, and Helobdella proboscises to identify conserved signaling molecules involved in tooth development. The selection criteria were particularly based on the presence of tooth-related genes in mice, Hirudo teeth, and Helobdella proboscis, wherein 4113 genes were commonly expressed in all three specimens. Furthermore, the chemical nature of leech teeth was also examined via TEM-EDS to compare the chemical composition with vertebrate teeth. The examination of tissue-specific genetic information and chemical nature between leeches and mice revealed chemical similarities between leech and mice teeth, as well as conserved signaling molecules involved in tooth formation, including Ptpro, Prickle2, and Wnt16. Based on our findings, we propose that leech teeth express signaling molecules conserved in mice and these conserved tooth-specific signaling for dental hard tissue formation in mice would corresponds to the structural formation of the toothed jaw in leeches.

Third molar agenesis in individuals with supernumerary teeth.

To explore the association between third molar agenesis and supernumerary tooth formation in a white-European population. A record review in various orthodontic clinics identified 380 eligible white-European individuals, half of whom had non-syndromic permanent supernumerary teeth (122 males and 68 females, totalling 244 supernumerary teeth; median age: 13.1, iqr: 1.5 years), and the other half were age- and sex-matched controls with full dentition, excluding the third molars. Tooth sequences were identified in panoramic radiographs. In the supernumerary group, approximately 80% of the individuals had a single supernumerary tooth, followed by those having two additional teeth. In both groups, there was no sexual dimorphism in third molar agenesis severity. The prevalence of third molar agenesis in the supernumerary group was similar to that of the control group (28/190 = 14.7% in both groups; p = 1.0). In total, 53 third molars were missing in the supernumerary group (n = 190) compared to 67 in the control group (n = 190; p = .862). The ratio of bilateral to unilateral third molar agenesis was significantly lower in the supernumerary group than in the control group (1.0 vs. 3.7, respectively; p = .026). The presence of supernumerary teeth did not significantly alter the likelihood of third molar agenesis or its severity. Bilateral third molar agenesis was considerably less prevalent in individuals with supernumerary teeth compared to controls. The present novel findings have important clinical and developmental implications.