Interrelation between fusions in the primary dentition and agenesis in the succedaneous permanent dentition seen from an embryological point of view

The purpose of the present study was to elucidate the relationship between fusions in the primary dentition and the occurrence of agenesis in the succedaneous permanent dentition in a Danish child population and to elucidate this relationship from the recently described normal embryological development of the anterior parts of the human maxilla and mandible. The material included radiographs, either as intraoral film or as orthopantomograms from a total of 19 primary dentitions with a total of 21 fusions. Radiographs of the permanent dentition in the fusion regions were available for all 19 dentitions. Of 21 fusions, a total of 20 were in the mandible and one in the maxilla. In 15 cases, the fusions were between primary incisors and in six cases between lateral incisors and canines. Agenesis of a permanent lateral incisor always occurred when there had been fusion of a primary lateral incisor and a canine in the primary dentition. When fusion had been between primary incisors, there was only agenesis of an incisor in the permanent dentition in a few cases. The degree of fusion between the involved teeth was not related to the occurrence of agenesis. It is suggested that the intra-jaw differences are related to the recently reported prenatal developmental patterns of the alveoli of the incisors and canines. Moreover, it is suggested that neural crest developmental field differences between the developing maxilla and mandible may explain the inter-jaw differences in phenotypic abnormalities.     

Masculinization of the eruption pattern of permanent mandibular canines in opposite sex twin girls

The aim of this study is to explore the effect of prenatal androgenization on the clinical eruption of permanent teeth expressing dimorphism and bimaturism. The eruption curves of permanent teeth (except third molars), including those that make up the canine complex (permanent canines, lower first premolars), are compared among opposite sex twins (OS twins) relative to single‐born boys and girls. The comparisons are made with regard to three phases of eruption (pierced mucosa, half‐ erupted, and completely erupted) from a cross‐sectional sample of dental casts, using Kaplan–Meier survival and Cox regression analyzes. The casts were collected from 2159 school children from the US Collaborative Perinatal Project, including 39 pairs of OS‐twins, of which 12 pairs (30.8%) were Euro‐Americans and 27 pairs (69.2%) were of African‐American ancestry. The eruption patterns of the incisors, upper first molars, and lower canines were found to be significantly masculinized (delayed) among OS twin girls. The differences in most other teeth were either not significant, or the number of observations of active eruption phases were too few, such as in the upper first molars and incisors, to yield strong evidence and meaningful results. The masculinization of the tooth eruption pattern in OS twin girls is intriguing because of the lower canine responses during puberty, as well as canine primordial formation during early fetal androgenization of their co‐twin during the 8th to 14th gestational weeks. The present results offer a challenge for future research exploring tooth eruption mechanisms, and may also highlight some cases of delayed or ectopic canines, which are biased toward females. Am J Phys Anthropol 151:566–572, 2013. © 2013 Wiley Periodicals, Inc.     

Dental size variation in the Atapuerca-SH Middle Pleistocene hominids

The Middle Pleistocene Atapuerca-Sima de los Huesos (SH) site in Spain has yielded the largest sample of fossil hominids so far found from a single site and belonging to the same biological population. The SH dental sample includes a total of 452 permanent and deciduous teeth, representing a minimum of 27 individuals. We present a study of the dental size variation in these hominids, based on the analysis of the mandibular permanent dentition: lateral incisors, n=29; canines, n=27; third premolars, n=30; fourth premolars, n=34; first molars, n=38; second molars, n=38. We have obtained the buccolingual diameter and the crown area (measured on occlusal photographs) of these teeth, and used the bootstrap method to assess the amount of variation in the SH sample compared with the variation of a modern human sample from the Museu Antropologico of the Universidade of Coimbra (Portugal). The SH hominids have, in general terms, a dental size variation higher than that of the modern human sample. The analysis is especially conclusive for the canines. Furthermore, we have estimated the degree of sexual dimorphism of the SH sample by obtaining male and female dental subsamples by means of sexing the large sample of SH mandibular specimens. We obtained the index of sexual dimorphism (ISD=male mean/female mean) and the values were compared with those obtained from the sexed modern human sample from Coimbra, and with data found in the literature concerning several recent human populations. In all tooth classes the ISD of the SH hominids was higher than that of modern humans, but the differences were generally modest, except for the canines, thus suggesting that canine size sexual dimorphism in Homo heidelbergensis was probably greater than that of modern humans. Since the approach of sexing fossil specimens has some obvious limitations, these results should be assessed with caution. Additional data from SH and other European Middle Pleistocene sites would be necessary to test this hypothesis.     

Increasing human tooth length between birth and 5.4 years

Most previous studies of tooth development have used fractional stages of tooth formation to construct growth standards suitable for aging juvenile skeletal material. A simple alternative for determining dental age is to measure tooth length throughout development. In this study, data on tooth length development are presented from 63 individuals of known age at death, between birth and 5.4 years, from an archeological population recovered from the crypt of Christ Church, Spitalfields, London. Isolated developing teeth (304 deciduous, 269 permanent) were measured in millimeters and plotted against individual age. Regression equations to estimate age from a given tooth length, are presented for each deciduous maxillary and mandibular tooth type and for permanent maxillary and mandibular incisors, canines, and first permanent molars. Data on the earliest age of root completion of deciduous teeth and initial mineralization and crown completion of some permanent teeth in this sample are given, as well as the average crown height and total tooth length from a small number of unworn teeth. This method provides an easy, quantitative and objective measure of dental formation appropriate for use by archeologists and anthropologists. © 1993 Wiley-Liss, Inc.     

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.     

Innervation of the human upper primary dentition: Implications for understanding tooth initiation and rethinking growth and eruption patterns

Recent comparisons of humans with apes and early fossil hominids have prompted renewed interest in the study of sequences of dental growth and development. Such comparisons, however, rely on certain assumptions about tooth development and dental homology and the biological reality of distinguishing “deciduous” from “permanent” teeth. In light of earlier suggestions by Schwartz that there might be a correlation between nerves and the stem progenitors of tooth classes, and thus between nerve branch number and number of tooth classes, we studied a large sample of ～ 3 month fetuses to elucidate the nature of nerve branching patterns and the development of the primary dentition (i.e., the “deciduous” incisors, canine, and molars, and the first “permanent” molar). Contrary to expectation, variation in nerve branch patterning was the rule. If nerve fibers do have a role in tooth development, it can only be at the time of initiation, with definitive innervation occurring late in tooth development. In taking into consideration the entire span of tooth development—from initiation to innervation to eruption—and the process by which successional teeth arise (each from the external dental epithelium of a predecessor tooth), we suggest that dividing tooth growth and eruption into patterns of the “deciduous” teeth vs. those of the “permanent” is artificial and that a more meaningful approach would be the study of the entire dentition.     

Morphological features of Jat dentition

Observations on morphological characters of milk and permanent teeth, based on 648 pairs of dental casts of 356 male and 292 female Jat children of Haryana (India) are reported. Deciduous teeth show high frequencies of bilateral winging of maxillary central incisor, Carabelli's cusp of maxillary second molar, and deflecting wrinkle of mandibular second molar. Reduction of maxillary molar cusps is more marked in males than in females. Y pattern is very common in deciduous molars. Permanent teeth have high frequencies of grooved cingulum of incisors, cingular nodule of lateral incisors and canines, and distal accessary ridge of canines. Low frequencies of Carabelli's cusp and winging are also common. The tendency towards faintly developed shovelling in milk incisors occurs more often than in the permanent teeth.     

Growth and development in the saddle-back tamarin: The sequence and timing of dental eruption and epiphyseal union

A cross-sectional sample of 121 colony-born saddle-back tamarins, Saguinus fuscicollis, was examined to identify the sequence and timing of dental eruption and epiphyseal union. The state of dental development of the deciduous and permanent dentitions was recorded as erupted or non-erupted on the basis of gingival penetration. Eighteen areas of union of long bone epiphyseal and other secondary centers, the union of the primary elements of the innominate, and the spheno-occipital synchondrosis were examined. The state of union at the areas was recorded on a three-point scale of not united, uniting, and united. The data indicated that deciduous incisors and canines were present at birth and that all deciduous teeth were erupted by 12 weeks. The first permanent tooth, M(1), erupted between weeks 16 and 23; the permanent dentition was fully erupted by 45 weeks. Union of the long bone epiphyses began in the third month at the distal humerus and continued until the first quarter of the second year. The secondary centers at the ischial tuberosity and iliac crest were united slightly later than four and six years of age, respectively. Regression analysis of the data indicate their potential use as parameters for predicting age in feral specimens.     

Odontometry of a Spanish neolithic-Bronze age sample. Comparison with other populations of the iberian peninsula. I.-Permanent teeth

The present study concerns the morphometric characteristics of two hundred permanent teeth from the Neolithic-Bronze Age human remains found in «Galería del Sílex» (Atapuerca Cave, Burgos, Spain). The crown index reveals that all the upper maxillary teeth (except incisors) and the mandibular first incisors, canines and premolars have a vestibulo-lingual diameter greater than the mesio-distal. The dental module and the surface value show that the mandibular teeth (except the molars) are smaller than those of the upper maxillary. These results are very similar to other European populations. Finally, the Sílex Gallery sample was compared with five other series of the Iberian Peninsula which have a chronology from the Mesolithic to the Middle Age. The results indicate a general decrease for both diameters (ØMD and ØVL) throughout time.     

Oral and craniofacial morphology of a patient with Larsen syndrome

A case is reported of a 15 years old Chinese female with Larsen syndrome exhibiting many characteristic facial and skeletal features plus hitherto unreported orofacial anomalies including delayed dental development; hypodontia affecting all the permanent canines, second and third molars, maxillary lateral incisors and second premolars; morphological anomalies of the maxillary first premolars and molars; a class 3 skeletal pattern and reduced upper facial height. Cephalometric radiographs showed the skull bones to have an appearance similar to that of osteopetrosis.     

Tooth loss and tooth retention in a multitribal group of Bantu-speaking South African blacks: A study on 500 dry mandibles

Tooth loss and tooth retention in adult South African Bantu-speaking Negroes were studied from data derived from 500 dry mandibles. The tribe, sex, and stated age of the specimens were available. Mandibles were equally distributed over the third to seventh decade of life. The presence of dental units was recorded and analysed within and between decade age groups. The mandibles carried a total of 5,459 dental units. Between the third and fourth decades of life and between the sixth and seventh decades, the reduction of the frequency of dental units was mild and statistically not significant. It was, however, severe and significant between the fourth and fifth, and the fifth and sixth decades. In the third-decade group, most teeth were found in the anterior region with a tendency to diminish in number posteriorly. After the third decade there was a definite persistence of first premolars and canines with significant tendency toward loss of teeth anterior and posterior to them. Only the incisors and third molars showed significant reduction in number from the third to the fourth decade. The reduction of all teeth was statistically significant later, until the sixth decade of life. Although there was loss of teeth from the sixth to the seventh decade, it was not significant for any of the homologous dental units. There is a possibility that some dietary differences existed between the older subjects (50–70 years old) and the younger ones (20–49 years old) which may have had some influence on the results.     

Prenatal dental development in the black howler monkey (Alouatta caraya)

Prenatal dental development was investigated in 19 black howler monkey fetuses that ranged in crown-rump length from 84 mm to 170.5 mm. During this period of fetal development, all of the deciduous teeth and the first permanent molars were found to pass through various stages of crown and root formation. The deciduous incisors, canines, and first molars each calcified from a single calcification center. The second deciduous molars each calcified from two separate calcification centers. And, the third deciduous and first permanent molars each calcified from four separate calcification centers. The morphogenetic events involved in the establishment of the molar crown patterns were found to differ markedly from those of their counterparts among catarrhine primates. In all cases, however, the calcification sequence was found to be directly related to the morphology of the developing crown.     

Talon cusp from two archaic period cemeteries in North America: implications for comparative evolutionary morphology

Talon cusps are rare morphological features of the anterior dentition that represent a spectrum of lingual cingulum diversity. In this paper, talon cusp prevalence is described in two Archaic period North American samples, Windover Pond (Florida) and Buckeye Knoll (Texas). Given the early date of these cemeteries (~7500 BP), these specimens represent the oldest reported cases of lingual talon cusp in the New World, and perhaps globally. Windover preserves three cases of talon cusp (representing three different individuals) affecting the permanent maxillary lateral incisors. The sample frequencies were 1.8% and 3.1% for the left and right maxillary lateral incisors, respectively. Buckeye Knoll preserves four cases of talon cusp representing three individuals. Talon cusps at this site were distributed throughout the maxillary anterior dentition, including a permanent maxillary central incisor, bilateral permanent maxillary lateral incisors, and a deciduous maxillary lateral incisor. The multicomponent nature of this site complicates sample frequency calculation with by-tooth estimates ranging from 3.6% to 25%. This paper discusses the difficulties with comparative frequency estimation, resulting from a proliferation of terminology that is discipline-specific. Understanding the evolutionary basis and significance of dental morphological variation requires an inclusive approach to the comparative literature that focuses on homology within the context of odontogenetic process.     

The study of animal bones from archaeological sites. By Raymond E. Chaplin. ix + 170 pp., figures,tables, bibliography,index. Seminar press,London. 1971. $5.75 (cloth)

A review of the literature reveals a long history of disagreement on the interpretation of the lower deciduous and permanent dentition of the Indriidae. This disagreement has centered on the existence and/or replacement of a canine as a member of the indriid toothcomb. The presence of a pair of canines in the toothcomb of lemurids and lorisids has rarely been questioned, and there is no evidence to indicate that this interpretation is incorrect. There has, however, been no consistency nor substantiating evidence presented for any interpretation of the indriid toothcomb. By comparing the morphology of the teeth of the lemurid, lorisid, and indriid toothcomb, both deciduous and permanent, comparing the mode of dental development in these three families, identifying the indriid lower deciduous dentition, and by relating the data to an ontogenetic and phylogenetic framework, this study proposes: (1) in all three families, the lateral teeth of the toothcomb are canines, (2) the dental formula for the lower deciduous teeth of indriids is 1.1.4, (3) the dental formula for the lower permanent teeth of indriids is 1.1.2.3, and (4) that decrease in number of incisors during primate evolution was most likely I1 to I2 to I3.     

Some dental traits of Diaguitas Indian skulls

Dental characteristics were studied on 60 skulls that belong to a population of Diaguitas Indians of approximately the Tenth Century. Mesiodistal crown diameters of permanent teeth were as follows: central incisors (8.77 mm), lateral incisors (7.23 mm), canines (8.40 mm), first maxillary molars (10.77 mm), second maxillary molars (10.71 mm), first mandibular molars (11.13 mm), and second mandibular molars (10.17 mm). Also determined was the frequency of shovel shaped incisors (80.30%), groove and cusp patterns of mandibular molars (Y5 73.40%), groove and cusp patterns of maxillary molars (H4 87.25%), and mesiopalatal version of maxillary incisors (66.20%). No skull showed Carabelli's cusp. The findings were compared with those for different populations past and living. The results suggest that the affiliation of the population analyzed was mongoloid.     

Brief communication: on the optimum number of metacarpals for roentgenogrammetric measurement

Interpretation of dental development of fossil hominids requires understanding of and comparison with the pattern and timing of dental development among living humans and pongids. We report the first study of crown and root calcification in the lower permanent molar teeth among chimpanzees (Pan troglodytes) of known chronological age. A series of 99 lateral head radiographs of 16 captive-born chimpanzees were analyzed. Radiographs were taken at irregular intervals throughout the entire postnatal period of dental development from birth to 13 years of age. Permanent mandibular molars were rated on an eight-point maturation scale from initial radiographic appearance through crown and root calcification and apical closure of the root canals. In addition, we were able to document initial crown calcification and completion, as well as root completion and apical closure in incisors, canines, and premolars. Our results show several differences from the widely cited developmental schedule for pongid dentitions of Dean and Wood (Folia Primatol. 36:111–127, 1981). We found a much greater degree of temporal overlap in calcification of the crowns of adjacent molars, a pattern very unlike that usually seen in human dental development, which is characterized by delays between the onset of crown calcification in the molar series. Also, the ages and durations of crown and root formation in our chimp sample differ from the estimates proposed by Dean and Wood. By more clearly establishing the nature of developmental schedules and the timing of major events in the pongid dentition, these results should aid in the ongoing controversies concerning the human or pongid nature of dental development among Plio-Pleistocene hominids.     

禄丰古猿前部牙齿的釉面横纹与牙冠形成时间

釉面横纹的数目可用于推断个体牙齿的牙冠形成时间,在生长发育研究中具有重要的意义。本研究运用数码体视显微镜和扫描电镜观察了云南石灰坝禄丰禄丰古猿(简称禄丰古猿)30枚齿冠完整的前部牙齿,包括上下颌中门齿6枚、侧门齿10枚和犬齿14枚。根据唇侧面釉面横纹计数的观察结果,分别以7天和9天芮氏线生长周期,估算各齿型的牙冠形成时间,结果显示:以生长周期7天计算,中门齿牙冠形成时间约为3.6-4.1年,侧门齿牙冠形成时间约为2.7-3.7年,犬齿牙冠形成时间约为4.2-7.0;以生长周期9天计算,中门齿牙冠形成时间约为4.4-5.2年,侧门齿牙冠形成时间约为3.4-4.7年,犬齿牙冠形成时间约为5.2-8.8年。为更深入地了解禄丰古猿牙冠形成时间在不同齿型及性别间足否存在明显差异,本文用SPSS软件对其进行显著性差异检验。采用小样本平均值的t值假设检验(置信区间为95%),结果如下:禄丰古猿前部牙齿的牙冠形成时间在各类牙齿的上下颌中不存在显著性差异;犬齿牙冠形成时间存在非常显著的性别差异,雄性牙冠形成时间明显长于雌性,侧门齿也存在显著的性别差异,而中门齿性别间则无显著性差异。此外对禄丰古猿中门齿,侧门齿和犬齿的牙冠形成时间进行单因素方差分析并两两对比,结果显示中门齿与侧门齿的牙冠形成时间不存在显著性差异,而犬齿与中门齿和侧门齿均存在显著性差异,犬齿牙冠形成时间明显长于门齿。同时也对禄丰古猿前部牙齿的牙冠形成时间与齿冠高进行相关性分析,其结果表明两者有显著的正相关性。将禄丰古猿与其他古猿和现生大猿、南方古猿以及人属成员进行对比,结果显示其前部牙齿牙冠形成时间长于原修康尔猿、南方古猿、傍人、人属成员,接近于蝴蝶禄丰古猿和大猩猩,而明显小于黑猩猩、华南化石猩猩及现生猩猩。     

Enamel hypoplasia in the Middle Pleistocene hominids from Atapuerca (Spain)

The prevalence and chronology of enamel hypoplasias were studied in a hominid dental sample from the Sima de los Huesos (SH) Middle Pleistocene site at the Sierra de Atapuerca (Burgos, northern Spain). A total of 89 permanent maxillary teeth, 143 permanent mandibular teeth, and one deciduous lower canine, belonging to a minimum of 29 individuals, were examined. Excluding the antimeres (16 maxillary and 37 mandibular cases) from the sample, the prevalence of hypoplasias in the permanent dentition is 12.8% (23/179), whereas the deciduous tooth also showed an enamel defect. No statistically significant differences were found between both arcades and between the anterior and postcanine teeth for the prevalence of hypoplasias. In both the maxilla and the mandible the highest frequency of enamel hypoplasias was recorded in the canines. Only one tooth (a permanent upper canine) showed two different enamel defects, and most of the hypoplasias were expressed as faint linear horizontal defects. Taking into account the limitations that the incompleteness of virtually all permanent dentitions imposes, we have estimated that the frequency by individual in the SH hominid sample was not greater than 40%. Most of the hypoplasias occurred between birth and 7 years (N = 18, X = 3.5, SD = 1.3). Both the prevalence and severity of the hypoplasias of the SH hominid sample are significantly less than those of a large Neandertal sample. Furthermore, prehistoric hunter-gatherers and historic agricultural and industrial populations exhibit a prevalence of hypoplasias generally higher than that of the SH hominids. Implications for the survival strategies and life quality of the SH hominids are also discussed. © 1995 Wiley-Liss, Inc.     

禄丰古猿带状牙釉质发育不全的再观察

牙釉质发育不全是反映牙齿发育过程中遭遇生理性刺激的有效指标。本文对来自云南禄丰石灰坝的禄丰古猿(Lufengpithecus lufengensis)261枚单颗恒齿进行观察分析,发现223枚牙齿普遍罹患带状牙釉质发育不全(LEH),比例为85.4%,高于其它已报道过的中新世古猿、化石人科成员及现生大猿。另一方面,用扫描电镜和数码显微镜着重分析了12枚犬齿,均有多条LEH,且雄性犬齿的LEH条数多于雌性;相邻LEH间的釉面横纹数在14-25条之间。结合禄丰古猿釉面横纹的生长周期(9天),估算相邻LEH之间的时间间隔为4.8-6.6月,季节性营养不良可能是禄丰古猿釉质发育不全的主要原因。     

Dental fluctuating asymmetry in the Gullah: tests of hypotheses regarding developmental stability in deciduous vs. permanent and male vs. female teeth

In this investigation, deciduous teeth (canines, c; first molars, m1; second molars, m2) and their permanent successors (canines, C; first premolars, P1; second premolars, P2) were used to test two related hypotheses about fluctuating asymmetry (FA). First, based on the biology of the developing dentition, it was predicted that deciduous teeth would be more developmentally stable and thus exhibit less dimensional FA than their permanent successors. Second, based on sex differences in tooth development, it was predicted that female canines would have greater developmental stability (less FA) than male canines. Bucco-lingual measurements were made on dental casts from a single Gullah population. Using a repeated-measures study design (n = 3 repeated measures), we tested these hypotheses on sample sizes ranging from 63-82 antimeric pairs. Neither hypothesis was supported by our data. In most cases, Gullah deciduous teeth did not exhibit statistically significantly less FA than their permanent successors; indeed, statistically significant differences were found for only 3 of 12 deciduous vs. permanent contrasts, and in two cases, the deciduous tooth had greater FA. Female mandibular canines exhibited statistically significantly greater FA than those of males, while there was no statistically significant sex difference in FA for the maxillary canine. FA in these Gullah samples is high when compared to Archaic and late prehistoric Ohio Valley Native Americans, consistent with historical and archaeological evidence that environmental stress was relatively higher in the Gullah population. We suggest that when environmental stress in a population is high, the impact of differences in tooth formation time spans and developmental buffering upon FA may be minor relative to the effect of developmental noise.