Postnatal lower jaw dentition in different phenotypes of tabby mice

The tabby (Ta) syndrome in mouse is homologous to human anhidrotic ectodermal dysplasia, including defective development of hair, teeth, and glands. To complete the available data on the functional dentition in the Ta mice, we analyzed the mandibular cheek teeth in 261 postnatal specimens arranged in several phenotype/genotype groups: 51 Ta-hemizygous males, 56 Ta-homo/hemizygous females, 64 Ta-heterozygous females, and 40 and 50 wild-type control males and females, respectively. We evaluated tooth number, size, shape and eruption and compared these parameters in the different groups. In any individual group of Ta mice, there was variability mainly in the size and shape of the most mesial tooth and in the tooth patterns. The incidence of a reduction in tooth number in homozygous and hemizygous mice was dependent on the breeding scheme.     

Mesiodens

The presence of an extra supernumerary tooth in the central position of the upper or lower jaw is called mesiodens. These teeth can be present as part of a syndrome or can be found as an isolated finding. Mesiodens is the most frequently found extra tooth, with a prevalence in the general population of 0.15-1.9%, and with a higher frequency in males than females. Usually the shape is conical and mesiodens is smaller than the neighbour incisor. Several hypotheses have been suggested for the formation of supernumerary teeth. Early diagnosis and treatment are needed to support right dental occlusion.     

Emergence of permanent teeth among the meiteis of Manipur,India

To estimate the time and sequence of emergence of the first 28 permanent teeth in rural Meiteis of Manipur, 440 children 5–14 years of age were examined. Median tooth emergence times were earlier in females than males. The first molar was highly variable in its emergence time in both sexes. With the exception of premolars, mandibular teeth emerged earlier than maxillary teeth. Although no definite pattern was found in bilateral differences, left maxillary teeth and right mandibular teeth emerged slightly earlier in females and males, respectively. There was no clear sex difference in the sequence of permanent tooth emergence. The quiescent period between the first and second phases of tooth emergence was more apparent in the mandible than in the maxilla and occurred between the lateral incisor and first premolar in both jaws and sexes. The Meiteis displayed earlier emergence compared to other populations within India. The findings of this study support earlier reports that socioeconomic conditions do not significantly influence permanent tooth emergence; the chief controlling factor is most likely genetic. © 1994 Wiley-Liss, Inc.     

Teeth and their sex-dependent dimorphic shape in three species of costa rican plethodontid salamanders (Amphibia: Urodela)

The shape of the teeth and their sex-dependent dimorphic expression in three species of Costa Rican plethodontids (Bolitoglossa subpalmata, Oedipina uniformis and Nototriton abscondens) were studied using light microscopy and scanning electron microscopy. The teeth of the vomerine tooth patches are about one third larger than the teeth of the jaws in B. subpalmata and O. uniformis, whereas all teeth of N. abscondens are of about uniform size. The occurrence of bicuspid tooth germs in the fetus proves that primary teeth are bicuspid in these directly developing plethodontids. Females possess only bicuspid teeth consisting of a pedicel and a crown, as is considered characteristic for urodeles after metamorphosis. Adult males possess conical monocuspid teeth on the premaxillary. These teeth--which are similar to the typical late larval tooth of salamanders presenting a larval stage--are about twice as big as the neighbouring bicuspid maxillary teeth. N. abscondens males possess some monocuspid teeth and teeth of aberrant shapes on the premaxillary and the maxillaries. A tendency to build more monocuspid teeth in the premaxillary region than in the maxillary region can be observed in this species. We suppose that different degrees of sensitivity to androgens in each section of the dental lamina of the upper jaw cause the secondary occurrence of conical monocuspid teeth predominantly on the premaxillary section.     

Clinical and radiographic dental findings in X linked hypohidrotic ectodermal dysplasia.

X linked hypohidrotic ectodermal dysplasia was studied in the dentition of both affected males and carrier females. Hypodontia was more severe in males than females and there were differences in the pattern of tooth absence between the sexes. Abnormal crown form, with the maximum diameter of the teeth being apically displaced, was noted particularly in the anterior teeth. Taurodontism was commonly seen radiographically.     

Permanent tooth sizes in 46, XX-males

Measurements of permanent tooth sizes in four XX-males showed their teeth to be smaller than those of male controls and similar in size to those of female controls. The teeth of the XX-males were smaller than those of their first-degree male relatives and of the same size as those of three of their mothers. The teeth of three fathers of XX-males were similar in size to control males and the teeth of three mothers of XX-males were similar in size to control females. The detailed knowledge that exists regarding the sequence and timing of tooth crown development allows the following implications to be made from our results. Growth retardation in XX-males is of primary genetic origin and is due to the absence of the gene(s) normally located on the Y-chromosome. Growth retardation, compared to normal males, is apparent and final three years after birth, conceivably begins after 2--3 months of foetal life and persists during childhood. It is unlikely that XX-males have had a Y-chromosome at any stage. If maleness is caused by a recessively inherited translocation or a mutational acquisition of the testis-determining gene(s), the genes influencing growth are not involved in either mechanism.     

Enamel thickness in 47,XYY males' permanent teeth

Enamel thickness of the maxillary permanent central incisors and canines in 14 47,XYY males, their male and female relatives and population-control males and females were determined from radiographs. The results indicated, although not fully unambiguously, that the thickness of enamel and that of 'dentin' (distance between mesial and distal dentino-enamel junctions) are increased in the teeth of 47,XYY males compared with normal controls. Earlier results have indicated a direct growth-promoting effect of the Y chromosome on tooth growth by influencing both enamel formation and, possibly through cell proliferations, growth of dentin. The present results can be considered additional evidence for the presence of the factors within the Y chromosome controlling different growth processes. Tooth size measurements in two males with deletions of the parts of the y chromosome suggested that there may be a specific growth-promoting gene(s) in the non-fluorescent part of the long arm. It is suggested that the way of influence of the Y chromosome on the amelogenesis is regulatory, and that the difference in tooth size between males and females is explained by a differential growth-promoting effect of the Y chromosome compared to the X chromosome.     

Not your father’s homodonty—stress,tooth shape,and the functional homodont

Teeth tell the tale of interactions between predator and prey. If a dental battery is made up of teeth that look similar, they are morphologically homodont, but if there is an unspecified amount of regional specialization in size or shape, they are morphologically heterodont. These are vague terms with no useful functional implication because morphological homodonty does not necessarily equal functional homodonty. Teeth that look the same may not function the same. Conical teeth are prevalent in fishes, superficially tasked with the simple job of puncture. There is a great deal of variation in the shape and placement of conical teeth. Anterior teeth may be larger than posterior ones, larger teeth may be surrounded by small ones, and patches of teeth may all have the same size and shape. Such variations suggest that conical dentitions might represent a single morphological solution for different functional problems. We are interested in the concept of homodonty and using the conical tooth as a model to differentiate between tooth shape and performance. We consider the stress that a tooth can exert on prey as stress is what causes damage. To create a statistical measure of functional homodonty, stress was calculated from measurements of surface area, position, and applied force. Functional homodonty is then defined as the degree to which teeth along the jaw all bear/exert similar stresses despite changes in shape. We find that morphologically heterodont teeth are often functionally homodont and that position is a better predictor of performance than shape. Furthermore, the arrangement of teeth affects their function, such that there is a functional advantage to having several smaller teeth surrounding a singular large tooth. We demonstrate that this arrangement of teeth is useful to grab, rather than tear, prey upon puncture, with the smaller teeth dissipating large stress forces around the larger tooth. We show that measurements of how shape affects stress distribution in response to loading give us a clearer picture of the evolution of conically shaped teeth.     

Effect of eda Loss of Function on Upper Jugal Tooth Morphology

The Tabby/eda mice, which bear a loss of function mutation for the eda (ectodysplasinA) gene, are known to display developmental anomalies in organs with an ectodermal origin. Although the lower jugal (cheek) teeth of Tabby/eda mice have been extensively studied, upper teeth have never been investigated in detail. However, this may help us to further understand the function of the eda gene in tooth development. In this work, the shape and size of both the crown and the radicular system were studied in the Tabby/eda mice upper jugal teeth. To deal with the high morphological variability, we defined several morphotypes based on cusp numbers and position. Statistical tests were then performed within and between the different morphotypes to test the correlation between tooth size and morphology. Our analysis reveals that, as in lower teeth, eda is necessary to segment the dental lamina into three teeth with the characteristic size and proportions of the mouse. Nevertheless, since strong effects are observed in heterozygous upper teeth while lower are only mildly affected, it seems that the upper jaw is more sensitive than the lower jaw to the loss of eda function. Modifications in cusp number and the abnormal crown size of the teeth are clearly linked, and our results indicate a role of eda in cusp patterning. Moreover, we found that the Tabby mutation induces variations in the dental root pattern, sometimes associated with hypercementosis, suggesting a newly uncovered role played by eda in root patterning and formation. Anat Rec, 2009. © 2008 Wiley‐Liss, Inc.     

Renal pathology in hemizygous sickle cell mice

Transgenic mice have been developed that express exclusively human sickle cell beta hemoglobin and have major pathological features found in humans with sickle cell disease. These mice provide a unique opportunity to investigate the fundamental mechanisms of this disease and to design new strategies to correct the associated genetic defect(s). We found that in breeding males expressing only adult human alpha-globin and sickle beta-globin (homozygous SS mice) with females containing these transgenes plus one copy of the mouse beta-globin gene (hemizygous SS mice) greater than expected numbers of hemizygous offspring were produced than homozygous mice (carrying no mouse beta-globin gene). These hemizygous mice, expressing the human alpha and sickle beta(s) transgenes in combination with mouse beta+/-, were used for our preliminary studies of their renal pathology. No kidney lesions were found in the control (129/Sv) mice, whereas about 50% of the hemizygous SS mice showed mild-to-severe kidney lesions, including glomerulonephritis, cystic atypical hyperplastic tubules, and general nephropathy. Kidneys of some hemizygous mice were normal or showed minimal nephropathy, yet those of the susceptible phenotype developed a mild-to-more-severe form of renal lesions. The tubular epithelium of kidneys of hemizygous mice of the more affected phenotype exhibited increased expression of inducible nitric oxide synthase with an increased 3-nitrotyrosine in close proximity. There was also a stronger immunostaining for vascular cell adhesion molecule-1 in the interstitial capillary cells as well as the tubular epithelial cells of the renal cortex, compared with normal control mice. The occurrence of a high incidence of renal abnormalities in our hemizygous SS mice suggests that these mice may provide a suitable model to study the pathogenesis of nephropathy resulting from altered blood flow and/or insufficient oxygen delivery.     

Craniofacial and dental characteristics of Kabuki syndrome

We describe oral manifestations in six patients (three females and three males aged 6 to 24 years) with Kabuki syndrome (KS), based on their physical, orthopantomographic, and cephalometric findings. All six patients had a high-arched palate, malocclusion, most commonly unilateral posterior cross-bite (5/6), severe maxillary recession and mid-facial hypoplasia. Other frequently observed oral manifestations included small dental arch and hypodontia. Three patients lacked permanent teeth, mostly the central/lateral incisors. Both tooth size (in primary and permanent teeth) and dental arch (in length and width) tended to be small. We would like to stress that oral care and management is a must for the well-being of KS patients.     

The intraspecific diversity of tooth morphology in the large-spotted catshark Scyliorhinus stellaris: insights into the ontogenetic cues driving sexual dimorphism

Teeth in sharks are shed and replaced throughout their lifetime. Morphological dental changes through ontogeny have been identified in several species and have been correlated with shifts in diet and the acquisition of sexual maturity. However, these changes were rarely quantified in detail along multiple ontogenetic stages, which makes it difficult to infer the developmental processes responsible for the observed plasticity. In this work, we use micro-computed tomography and 3D geometric morphometrics to describe and analyze the tooth size and shape diversity across three ontogenetic stages (hatchling, juvenile, and sexually mature) in the large-spotted catshark Scyliorhinus stellaris (Linnaeus, 1758). We first describe the intra-individual variation of tooth form for each sex at each ontogenetic stage. We provide a tooth morphospace for palatoquadrate and Meckelian teeth and identify dental features, such as relative size and number of cusps, involved in the range of variation of the observed morphologies. We then use these shape data to draw developmental trajectories between ontogenetic stages and for each tooth position within the jaw to characterize ontogenetic patterns of sexual dimorphism. We highlight the emergence of gynandric heterodonty between the juvenile and mature ontogenetic stages, with mature females having tooth morphologies more similar to juveniles’ than mature males that display regression in the number of accessory cusps. From these data, we speculate on the developmental processes that could account for such developmental plasticity in S. stellaris.     

IPS e.max Press全瓷冠用于前牙修复：边缘适合度及颜色匹配随访

背景：IPS e.max Press热压铸全瓷以其较好的美观效果和生物学性能已被越来越多地应用于临床修复。 目的：分析IPS e.max Press全瓷冠用于前牙美学修复的边缘适合度及颜色匹配等情况。 方法：纳入前牙美容修复患者52例(138颗牙),其中男20例,女32例,年龄18-45岁,前牙缺损62颗,牙外伤46颗,畸形小牙30颗,分为2组修复,治疗组(n=26)采用IPS e. max Press全瓷冠和传统钴铬合金烤瓷冠修复,对照组(n=26)采用传统钴铬合金烤瓷冠修复,修复后1周复诊,调查患者满意度;修复后随访6个月、2年,评估修复体完整性、边缘适合度、牙龈健康状况及颜色匹配等情况。 结果与结论：修复后1周,治疗组患者对修复体颜色、外形及舒适度方面的满意度显著高于对照组(P < 0.05);治疗后6个月,治疗组边缘适合度、牙龈健康状况及颜色匹配显著优于对照组(P < 0.05);治疗后2年,治疗组边缘适合度、牙龈健康状况及颜色匹配显著优于对照组(P < 0.05)。表明IPS e.max Press全瓷冠修复前牙具有良好的边缘适合度、牙龈健康状况及颜色匹配等生物学特性,患者满意度高。 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

Size and shape of mandibular first molars in Down syndrome

The size and shape characteristics of permanent mandibular first molars were compared in a group of young males with Down syndrome (DS) and a control group of normal males. Generalized size was quantified by the log transforms of five intercusp distances and shape by a principal component analysis of the log distances scaled to constant size.

On average the DS molars were smaller than the controls by 8%, the most marked reduction being in the distance between the distal and distolingual cusps. The scores on two of the four components of shape also differed between the DS and control teeth. These two shape components, which accounted for over 41% of the total shape variation, were determined specially by the occlusal morphology of the distal crown region. Discriminant function analyses also indicated the importance of the distal regions in discriminating between control and DS molars.

Evidence suggests that trisomy 21 is associated with a general retardation in growth. The observed features of DS molars were consistent with decreased cellular activity in the developing tooth germs, producing morphological changes that were more pronounced in the later-forming crown regions.     

Size and shape of mandibular first molars in Down syndrome

The size and shape characteristics of permanent mandibular first molars were compared in a group of young males with Down syndrome (DS) and a control group of normal males. Generalized size was quantified by the log transforms of five intercusp distances and shape by a principal component analysis of the log distances scaled to constant size. On average the DS molars were smaller than the controls by 8%, the most marked reduction being in the distance between the distal and distolingual cusps. The scores on two of the four components of shape also differed between the DS and control teeth. These two shape components, which accounted for over 41% of the total shape variation, were determined specially by the occlusal morphology of the distal crown region. Discriminant function analyses also indicated the importance of the distal regions in discriminating between control and DS molars. Evidence suggests that trisomy 21 is associated with a general retardation in growth. The observed features of DS molars were consistent with decreased cellular activity in the developing tooth germs, producing morphological changes that were more pronounced in the later-forming crown regions.     

Comparison of the total length and areas of upper central incisors between males and females using computer-assisted morphometry

The determination of measurements of teeth facilitates various procedures in dentistry. The purpose of this study was to evaluate the total length and the area of the non-extracted upper central incisors (UCI). Periapical radiographies of 42 UCI were placed over a lighted box. The outlines of the teeth and the pulp cavity were traced onto sheets and then measured using an image analyzer. The area of the upper left central incisor tooth (tooth 21) was statistically significantly larger in males than in females (p = 0.02). The total length of the right UCI was similar to that of the left one. This study demonstrates that computer-assisted morphometry is an important tool for the evaluation of the total length and areas of teeth and their pulp cavities. The significantly larger area of tooth 21 in males compared to females has anthropomorphic and clinical implications.     

Illustrating ontogenetic change in the dentition of the Nile monitor lizard,Varanus niloticus: a case study in the application of geometric morphometric methods for the quantification of shape–size heterodonty

Many recent attempts have been made to quantify heterodonty in non-mammalian vertebrates, but the majority of these are limited to Euclidian measurements. One taxon frequently investigated is Varanus niloticus, the Nile monitor. Juveniles possess elongate, pointed teeth (caniniform) along the entirety of the dental arcade, whereas adults develop large, bulbous distal teeth (molariform). The purpose of this study was to present a geometric morphometric method to quantify V. niloticus heterodonty through ontogeny that may be applied to other non-mammalian taxa. Data were collected from the entire tooth row of 19 dry skull specimens. A semilandmark analysis was conducted on the outline of the photographed teeth, and size and shape were derived. Width was also measured with calipers. From these measures, sample ranges and allometric functions were created using multivariate statistical analyses for each tooth position separately, as well as overall measures of heterodonty for each specimen based on morphological disparity. The results confirm and expand upon previous studies, showing measurable shape–size heterodonty in the species with significant differences at each tooth position. Tooth size increases with body size at most positions, and the allometric coefficient increases at more distal positions. Width shows a dramatic increase at the distal positions with ontogeny, often displaying pronounced positive allometry. Dental shape varied in two noticeable ways, with the first composing the vast majority of shape variance: (i) caniniformy vs. molariformy and (ii) mesially leaning, ‘rounded’ apices vs. distally leaning, ‘pointed’ apices. The latter was twice as influential in the mandible, a consequence of host bone shape. Mesial teeth show no significant shape change with growth, whereas distal teeth change significantly due primarily to an increase in molariformy. Overall, heterodonty increases with body size concerning both tooth size and shape, but shape heterodonty changes in the mandible are much less pronounced. Although it is unclear to what degree V. niloticus specializes in hard prey items (durophagy), previous studies of varanid feeding behavior, along with research on analogous durophagous vertebrates, indicate a division of labor along the tooth row in adults, due to a possible transition to at least a partial durophagous niche. The geometric morphometric method proposed here, although not without its own limitations, may be ideal for use with a number of dental morphotypes in the future.     

Morphometric evaluation of the human tractus solitarius

We measured the cross-sectional area (CSA) of the human tractus solitarius (HTS) with the help of an image-analyzer system on a cross section of the upper part of the medulla oblongata in 44 Japanese cadavers (22 males and 22 females) and examined the relationship between age, sex and whether the subjects were dentulous or edentulous. The results showed no significant differences between the left and right sides of the HTS in either male or female subjects. However, the size of HTS decreased slightly with age in males but not at all in females, whereas tooth loss had a definite incidence on the size of HTS in females but not in male, as the CSA was smaller in edentulous females but not in edentulous males. This would tend to indicate that a decreases in taste function is connected with the aging process in male, and with tooth loss in females.     

Defective immunoglobulin M responses to vaccination or infection with Schistosoma mansoni in xid mice.

Mice vaccinated with irradiated Schistosoma mansoni cercariae develop a persistent immunoglobulin M (IgM) antischistosomulum antibody response. To investigate the possible role of antilarval IgM antibodies in the effector mechanism of vaccine-induced immunity, CBA/N mice, which have an X-linked genetic defect resulting in impaired IgM antibody responses to certain antigens, were analyzed for their resistance to a challenge infection. When either infected with unattenuated parasites or vaccinated with irradiated cercariae, mice of this inbred strain failed to produce detectable IgM antibodies to schistosomulum surface membrane and soluble worm antigens. To analyze the effect of this IgM deficiency on immunity, F1 hybrids were constructed between CBA/N females and nondefective C57BL/6J males. As expected, vaccinated (CBA/N X C57BL/6J)F1 females, as well as (CBA/J X C57BL/6J)F1 males and females, produced normal IgM antibodies to both surface antigens and worm antigen extracts. However, such antibodies were not produced by (CBA/N X C57BL/6J)F1 males (hemizygous for xid). Nevertheless, (CBA/N + C57BL/6J)F1 males displayed the same high levels of immunity to challenge infection as (CBA/N X C57BL/6J)F1 females and (CBA/J X C57BL/6J)F1 males and females. These results indicate that vaccine-induced immunity is not dependent on an IgM response to schistosome antigens.