Stereophotogrammetric analysis of occlusal morphology of extant hominoid molars: phenetics and function

Because teeth are commonly preserved in the fossil record, dental remains have often been employed in estimating evolutionary relationships among fossil hominoids. This is appropriate, however, only to the extent that dental morphology is phylogenetically informative. I have used phenetic analytic techniques to assess whether hominoid molars are likely to be useful for phylogenetic inference. Thirty-four occlusal landmarks for first and second molars were chosen; seven on each maxillary and ten on each mandibular tooth. Three-dimensional locations of these points were determined from stereophotographs of dental arcades of more than 260 specimens from six taxa (gorilla, chimpanzee, human, orangutan, siamang, and gibbon). Analytic emphasis was on canonical variates analyses of landmark coordinates for mandibular and maxillary second molars, adjusted for intergroup size differences. There is little correspondence between the systematic implications of hominoid molar morphometrics and reliable estimates of evolutionary propinquity based on interhominoid biomolecular similarities. The former seem to have been determined largely by dietary constraints. Although this suggests the possibility of using the protocol employed here to infer diets of fossil hominoids, molar crown measurements seem unlikely to serve well as phylogenetic indicators in the Hominoidea.     

Negritos, Australian aborigines, and the "proto-sundadont" dental pattern: the basic populations in east Asia, V.

Five evolutionarily significant dental traits were identified from a B-square distance analysis of nine crown characters recorded for several populations of East Asia and Oceania. Intergroup variation in these traits distinguishes three major divisions of the Mongoloid dental complex: sundadonty, sinodonty, and the dental pattern of Australian Aborigines. The Australian crown features may be characterized as having high frequencies of evolutionarily conservative characters. Negritos, one of the probable representatives of indigenous inhabitants of Southeast Asia who may have shared a common ancestor with Australians, possess the more derived sundadont dental pattern. As far as the five crown traits treated here are concerned, Australian dental features may be described as conforming to a "proto-sundadont" dental pattern, applying Turner's terminology. This pattern may represent a microevolutionary step prior to the emergence of the sundadont and sinodont patterns.     

Increase of tooth size in prehistoric coastal Peru, 10,000 B.P.-1,000 B.P.

Teeth increase in size during a 9,000-year period in an archaeologically derived, radiocarbon dated sample of skeletons from a geographically restricted area of coastal Peru. Although cultural change is extensive, including the transition to food production and pottery making, teeth do not reduce as predicted under these conditions by Brace's Probable Mutation Effect. Since most of the dental literature dealing with size change of teeth focuses upon dental reduction, hypotheses explaining why teeth increase through time are not well developed. No obvious selective forces explaining size increase are apparent in the present data. Attrition decreases through time. The increase in tooth size in this collection may be a function of overall cranialfacial size increase, which (pending further data) may be related to a general body size increase.     

Supernumerary molars in anthropoidea,adapidae, and Archaeolemur: Implications for primate dental homologies

The model of primate dental homologies and development recently proposed by Schwartz ('75, '78) is re-evaluated in view of documented exceptions to his account of postcanine supernumerary teeth in both anthropoids and prosimians. Schwartz concluded that catarrhines and living indriids retain only two true molars in each dental quadrant. As many as six molars on one side of the jaw can develop in rare instances in catarrhines, and supernumerary molars are also known for a wide range of other primates, including Cebidae, Adapidae, and subfossil Indriidae. Polydontia cannot be explained exclusively by atavistic development. More convincing explanations regard supernumerary teeth as the result of excessive growth of the dental lamina or localized twinning of tooth buds during early development. Conventional dental formulae of catarrhines and indriids including three permanent molars remain the most plausible.     

湖北长阳青铜时代人类乳齿特征的研究

对在湖北长阳县深潭湾崖葬墓出土的青铜时代人类乳齿形态特征的观察研究显示在人类恒齿出现的大多数具有种族识别价值的形态特征在乳齿有相等程度的表现,其中部分特征的出现率和表现程度高于恒齿。与其他地区人群相比,长阳青铜时代人类乳齿特征在总体上与东北亚人类具有的“中国型牙齿”特征接近。同时,在个别牙齿特征上呈现出南亚蒙古人种的特点。作者对产生这种现象的原因进行了分析。本文还就长阳青铜时代人类乳齿测量数据的表现特点进行了探讨。     

Homologies of the anterior teeth in Indriidae and a functional basis for dental reduction in primates

In a recent paper Schwartz ('74) proposes revised homologies of the deciduous and permanent teeth in living lemuriform primates of the family Indriidae. However, new evidence provided by the deciduous dentition ofAvahi suggests that the traditional interpretations are correct, specifically: (1) the lateral teeth in the dental scraper of Indriidae are homologous with the incisors of Lemuridae and Lorisidae, not the canines; (2) the dental formula for the lower deciduous teeth of indriids is 2.1.3; (3) the dental formula for the lower permanent teeth of indriids is 2.0.2.3; and (4) decrease in number of incisors during primate evolution was usually in the sequence I3, then I2, then I1. It appears that dental reduction during primate evolution occurred at the ends of integrated incisor and cheek tooth units to minimize disruption of their functional integrity.     

Development and evolution of the helicoidal plane of dental occlusion

The helicoidal plane of dental occlusion is a composite feature involving axial inclination of teeth and effects of dental attrition. Recent studies disagree on its distribution and significance in hominoid primates. The distribution, development, and functional basis of the helicoidal plane are investigated here, based on quantitative analysis of dental morphology and attrition in 667 human and 60 chimpanzee dentitions. Helicoidal planes are nearly universal in the human and chimpanzee dentitions studied. Increasing axial inclination of molars from M1 to M3 is primarily responsible for the helicoidal plane, although attrition acts to increase its expression. In hominoids, increased molar axial tilt appears to be associated with facial shortening and dental reduction. Population and species comparisons suggest a functional relationship with cranial structure. Progressive axial tilt of molars producing a helicoidal plane is found consistently in mammals with cheek teeth positioned partly under the cranium, as in hominids, pongids, some cebids, macropodids, ursids, and sciurids. Facial shortening is an important trend in hominid evolution and axial inclination of molars might be expected to show progressive change from Australopithecus afarensis to recent Homo sapiens.     

甘肃临潭磨沟墓地人骨的牙齿健康状况

本文通过甘肃临潭磨沟齐家文化墓地出土的262例人骨标本的牙病情况尤其是龋病、牙周病、根尖周病以及牙结石情况的统计与分析,得知磨沟墓地古代居民牙齿疾病的基本情况:1)牙病的罹患率性别差异显著,女性龋病和根尖周病的罹患率高于男性,而在牙周病和牙结石的出现率上则是男性高于女性;2)牙病的罹患率随着年龄增长而增高;3)龋病、牙周病及根尖周病多发于臼齿,牙结石多发于门齿;4)重度磨耗牙齿多发牙周病及根尖周病;5)牙病罹患率不仅受到性别、年龄、牙位以及齿冠磨耗程度的影响,而且与磨沟组古代居民农业种植食物和采集食物并重的食物结构有关。     

Dental remains from Dmanisi (Republic of Georgia): morphological analysis and comparative study

The systematic excavation of the Dmanisi site (Republic of Georgia) has provided the earliest evidence of hominins outside Africa, dating back to ca. 1.8Ma. The analysis of the hominin remains has mainly focused on the morphology of the crania and mandibles. We present the first detailed morphological analysis and comparison of the Dmanisi teeth. The dental evidence from Dmanisi shows a unique combination of primitive and derived traits. In general, although the Dmanisi dental fossils show primitive morphology that resembles that seen in Australopithecus and H. habilis, they also display some derived characteristics, particularly in relation to dental reduction, resembling that seen in the dentition of H. erectus from the Far East.     

牛河梁红山文化人群龋齿的统计与分析

本文通过对牛河梁遗址出土的31例红山文化时期人类牙齿龋病的统计与分析, 获知: 1)牛河梁遗址男女两性的患龋率、龋齿率没有明显的性别差异; 2)他们的患龋率和龋齿率有随年龄增长逐步增高的趋势; 3)上颌的龋齿罹患率高于下颌; 4)龋齿的发生主要集中在臼齿,且以咬合面部位为主; 5)他们的患龋率和龋齿率均较低。牛河梁红山文化人群相对偏低的龋齿率可能暗示出他们的经济生活方式还处在以采集狩猎为主体的模式中, 农耕经济可能处于较低层次的状态。     

Stem cells: Sources,and regenerative therapies in dental research and practice

Stem cells are considered to be among the principle scientific breakthroughs of the twentieth century for the future of medicine, and considered to be an important weapon to fight against diseases, particularly those that have resisted the efforts of science for a long time. Human dental tissues have limited potentials to regenerate but the discovery of dental stem cells have developed new and surprising scenario in regenerative dentistry. Stem cell treatments are one example of the possibility using adult cells sourced from patients’ own bodies’ means that it can be expected that in the near future such treatments may become routine at dental practices. The hope is that it will become possible to regenerate bone and dental tissues including the periodontal ligament, dental pulp and enamel, and that the creation of new teeth may also become feasible. In view of this possibility of achieving restoration with regenerative medicine, it can be considered that a new era of dentistry is beginning. Thus the aim of this review is to give dental professionals a brief overview of different stem cells sources and the latest findings and their implications for improving oral health and treating certain conditions of the human mouth and face.     

外胚间充质干细胞在牙组织工程的应用与基因调控

用干细胞构建组织工程化牙齿是近年来口腔医学领域的研究热点,外胚间充质干细胞是目前已知牙源性干细胞的共同前体细胞,细胞的生物学特性和成牙信号分子环境是牙齿发育与再生的核心与关键,并贯穿于牙齿形成的全过程,是研究牙组织工程最具潜力的种子细胞,明确外胚间充质干细胞成牙分化能力及相关表型特征和分化特性,对进一步深入认识牙齿发育与再生机理具有重要作用。     

Tooth size and arcadal length correlates in man

Intra-arcadal mesiodistal and buccolingual tooth size correlations were evaluated in a sample of 125 caucasoids with ideal occlusion. Dental dimensions were corrected for arcade mength (as a measure of jaw size) by a series of regression analyses of each mesiodistal dimension on the sum of the mesiodistal dimensions within each arcade. Regression coefficients of tooth dimension on arcade length were calculated to gain an insight into the dimensional sensitivity of individual teeth to arcade length variation. The data presented here suggest a strong association between arcadal length (jaw size) dependence, and the dimensional stability of individual teeth. When corrected for arcade length, a definite pattern of tooth size correlation emerges: postcanine maxillary and mandibular teeth are negatively correlated to the anterior teeth and are positively correlated to one another. The hypothesis is developed that anterior and postcanine teeth should be viewed as two separate and negatively size-correlated units, beyond the boundaries of the four morphological tooth classes. Recognition of this basic dichotomous size arrangement within each jaw allows for a reassessment of some of the problems associated with hominid dental evolution.     

The role of lead and cadmium in deciduous teeth and saliva on dental caries in children residing in Tehran,Iran

BackgroundLead (Pb) and Cadmium (Cd) are important environmental contaminants. There is no biological monitoring of exposure to these heavy metals and their potential effect on dental caries in children in Tehran, Iran, a polluted megacity. Therefore, the present study investigated the potential association between Pb and Cd levels in primary teeth and saliva and dental caries.MethodsIn a cross-sectional design, 211 children aged 6–11 years referred to Tehran University of Medical Sciences, School of Dentistry and residing in Tehran were examined. Pb and Cd levels of exfoliated primary teeth and stimulated saliva were determined by atomic absorption spectrophotometry (AAS). Dental caries prevalence was evaluated according to WHO criteria. Socioeconomic status, oral hygiene behavior, snacking frequency and salivary pH data were acquired as confounding factors. Frequency and percentages were reported for categorical variables, mean and standard deviation (SD) for continuous variables, and geometric mean for skewed continuous variables. A simple linear regression and Pearson correlation tests were used for statistical analyses. P-values < 0.05 were considered as significant.ResultThe mean (95 % confidence interval) Pb and Cd levels in teeth were 213.26 ppb (164.29–274.84) and 23.75 ppb (20.86–27.05), respectively. The mean Pb and Cd levels in saliva were 11.83 ppb (10.71–13.06) and 3.18 ppb (2.69–3.75), respectively. Furthermore, Pb and Cd in primary teeth and saliva were not associated (p > 0.05) with socioeconomic status, oral hygiene behavior and snacking frequencyConclusionThis study showed no association between Pb and Cd concentrations in primary teeth and in saliva with dental caries prevalence.     

A network of Wnt, hedgehog and BMP signaling pathways regulates tooth replacement in snakes

Most dentate vertebrates, from fish to humans, replace their teeth and yet the molecular basis of tooth replacement is poorly understood. Canonical Wnt signaling regulates tooth number in mice and humans, but it is unclear what role it plays in tooth replacement as it naturally occurs. To clarify this, we characterized Wnt signaling activity in the dental tissues of the ball python Python regius. This species replaces teeth throughout life (polyphyodonty) and in the same manner as in humans, i.e., sequential budding of teeth from the tip of the dental lamina. From initiation stage onwards, canonical Wnt read-out genes (Lef1 and Axin2) are persistently expressed by cells in the dental lamina tip and surrounding mesenchyme. This implies that molecular signaling at work during dental initiation carries over to tooth replacement. We show that canonical Wnt signaling promotes cell proliferation in python dental tissues and that by confining Wnt activity in the dental lamina the structure extends instead of thickens. Presumably, lamina extension creates space between successive tooth buds, ensuring that tooth replacement occurs in an ordered manner. We suggest that hedgehog signaling confines Wnt activity in the dental epithelium by direct planar repression and, during tooth replacement stages, by negatively regulating BMP levels in the dental mesenchyme. Finally, we propose that Wnt-active cells at the extending tip of the python dental lamina represent the immediate descendents of putative stem cells housed in the lingual face of the lamina, similar to what we have recently described for another polyphyodont squamate species.     

Paleoepidemiology of a central California prehistoric population from CA-Ala-329: dental disease

Ala-329 is a prehistoric central California site located on the southeastern margin of San Francisco Bay, dating from approximately 500 AD up to pre-European contact. A large earth mound, Ala-329, has yielded many well preserved burials, approximately 300 of which are included in this study. The most common pathological lesions seen in this population are in the dentition. Advanced attrition is pervasive, affecting all individuals with teeth in occlusion for 2 years or more. Deciduous teeth are involved even in very young children and often show severe wear before replacement. In the permanent dentition, all elements are involved by the second decade; in the oldest age category (41+ years), all individuals show severe wear throughout their dentitions. In fact, by the end of the third decade, the majority of individuals have no enamel remaining. Mild periodontal involvement is found in 74% of adults, socket resorption in 53%, and abscesses in 31% of the relevant sample. Interestingly, although dental abscesses are found more than twice as often among males, socket resorption is seen more often among females. Dental caries are seen in only 10 individuals. The high incidence of periodontal remodeling, socket resorption, and dental abscesses is probably a secondary result of severe dental attrition. It is hypothesized that a large quantity of abrasives in the diet is responsible for the extreme degree of attrition, in fact, among the most severe for any population yet described.     

Dental formulae and dental eruption patterns in Parapithecidae (Primates, Anthropoidea)

The eruption sequence for the lower teeth of Apidium phiomense based on 18 juvenile specimens is dP3, dP4, M1, M2, P2, P4, (P3, M3), C. Only five specimens of Parapithecus grangeri show developing lower teeth. P2, M1, and M2 all erupted before P3 and P4; C and M3 were the last cheek teeth to erupt. Late eruption of the lower canines in parapithecids is a possible shared derived resemblance linking these species with Anthropoidea and Adapidae and distinguishing both from Omomyidae, Tarsiidae, and tooth-combed lemurs. Late eruption of M3 in parapithecids is a shared derived resemblance with Anthropoidea alone. The lower dental formula of Apidium phiomense is confirmed as 2 X 1 X 3 X 3 by additional specimens which show the incisors. Based in part on tooth socket counts, the deciduous lower dental formula was 2 X 1 X 3. New specimens of Parapithecus grangeri now demonstrate an adult mandibular dental formula of 0 X 1 X 3 X 3 (not 2 X 1 X 3 X 3 as previously thought) and a juvenile formula of 1 X 1 X 3. The number of incisors possessed by Parapithecus fraasi is again open to debate. Material is insufficient to judge whether this species had a pair of incisors in each lower jaw quadrant, by analogy with Apidium, or had undergone reduction to just one incisor. In any event, the presence of two incisors in another parapithecid Apidium shows anterior tooth reduction of Parapithecus grangeri occurred independent of, and should not be considered a shared derived similarity with, Tarsiidae, as was once thought.     

New insight into dental epithelial stem cells: Identification,regulation, and function in tooth homeostasis and repair

Tooth enamel, a highly mineralized tissue covering the outermost area of teeth, is always damaged by dental caries or trauma. Tooth enamel rarely repairs or renews itself, due to the loss of ameloblasts and dental epithelial stem cells (DESCs) once the tooth erupts. Unlike human teeth, mouse incisors grow continuously due to the presence of DESCs that generate enamel-producing ameloblasts and other supporting dental epithelial lineages. The ready accessibility of mouse DESCs and wide availability of related transgenic mouse lines make mouse incisors an excellent model to examine the identity and heterogeneity of dental epithelial stem/progenitor cells; explore the regulatory mechanisms underlying enamel formation; and help answer the open question regarding the therapeutic development of enamel engineering. In the present review, we update the current understanding about the identification of DESCs in mouse incisors and summarize the regulatory mechanisms of enamel formation driven by DESCs. The roles of DESCs during homeostasis and repair are also discussed, which should improve our knowledge regarding enamel tissue engineering.     

拔除阻生智齿患者牙科焦虑的调查及分析

目的：了解综合医院口腔科拔除阻生智齿患者牙科焦虑的患病情况并进行相关因素分析。方法：采用牙科焦虑一般因素调查表、改良牙科焦虑量表（MDAS）及状态焦虑量表（S-AI）对300例口腔颌面外科门诊的拔除阻生智齿患者进行调查及评定,同时对引起牙科焦虑的相关因素进行分析。结果：拔除阻生智齿患者牙科焦虑的发生率为56.00%,有6项因素对牙科焦虑症的患病率有影响,差异有统计学意义（P〈0.05）,其中5项因素对MDAS得分影响较大。结论：牙科焦虑在拔除阻生智齿的患者中较普遍,有多种因素影响患者牙科焦虑的程度。