Form and patterning of anterior tooth wear among aboriginal human groups

Form and severity of dental attrition was assessed in aboriginal human groups including hunter-gatherers (Eskimos, Australians) and those with dependence to a varying degree on food production (Southwest U.S. and Ohio American Indians). Wear on anterior teeth was both relatively and absolutely greater in the hunter-gatherers, as indicated by comparisons of wear on anterior and posterior teeth which come into occlusion at roughly the same time. Distinct differences in form of anterior wear were also apparent: The hunter-gatherers exhibited steadily increasing incidences of labially rounded wear with greater functional age, while the food-producing groups showed little or no rounding but instead high frequencies of heavily cupped wear (especially in those with premature loss of posterior teeth). These differences were attributed to nonmasticatory utilization of the front teeth in hunter-gatherers and to employment of the anterior teeth in masticatory (grinding) activities necessitated by large-scale molar loss in food producers.     

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.     

Canadian Eskimo permanent tooth emergence timing

To identify the times of emergence of the permanent teeth of Canadian Eskimos (Inuit), 368 children and adolescents were examined. The presence or absence of all permanent teeth except the third molars was recorded and these data subjected to probit analysis. Female emergence times were advanced over males. Generally, the Inuit of both sexes showed statistically significant earlier emergence times than Montreal children, except for the incisors. The present results do not support hypotheses indicating that premature extraction of the deciduous teeth advances the emergence of their succedaneous counterparts. There is some indication the controls of deciduous tooth emergence continue to play some part in emergence of the permanent dentition, especially the first permanent teeth that emerge.     

Task activity and anterior tooth grooving in prehistoric California indians.

Abraded grooves have been observed on the anterior teeth of all the adults in a small population of prehistoric California Indians. These dental effects show considerable variety, appearing on maxillary and mandibular teeth, on approximal and occulusal surfaces, and either isolated or bilaterally aligned. Although many of the grooves are indistinguishable from those reported for other prehistoric populations, their variety illustrates the limited applicability of etiological hypotheses previously proposed to account for such effects. It is suggested that the grooves represent traces of a task activity involving the pulling of fibrous materials across the teeth.     

Relationships between attrition and lingual tilting in human teeth

Associations between occlusal dental attrition and the lingual tilting of human teeth were investigated in two aboriginal California populations. A literature survey suggests lingual tilting is related geographically and temporally to the helicoidal occlusal plane in humans; if true, lingual tilting should be expected throughout the Homo osteological record. Buccal alveolar abscesses, exposed pulp chambers, extent of tooth attrition, angle of lingual tilt, and amount of overjet were observed for lingually tilted teeth. These attributes were analyzed statistically, leading to a conclusion that lingual tilting is slight and infrequent unless tooth attrition is pronounced. It is suggested that lingual tilting is due in part to masticatory stress. A feedback model considers lingual tilting as one conspicuous manifestation of a more complex “severe attrition syndrome,” the initial stimulus for which may derive from heavy occlusal tooth wear. Untested possibilities should be examined–e.g., age-related changes, the impact of the helicoidal occlusal plane, and the role of masticatory forces.     

Approximal grooving of teeth

Approximal grooving of teeth is a form of tooth wear seen in some fossil hominids (Neandertal Man and Pekin Man) and in some primitive peoples (Bushmen, Australian aborigines and American Indians). Previous workers have claimed the grooves were produced either by an acid secreted from the gum or by constant probings with a tooth-pick. The purpose of this paper is to refute these hypotheses, and to suggest from observations on the morphology of the grooves in four Bushman skulls, one American Indian skull, and one South African Negro skull that the approximal grooves are produced by dietary grit (sand and soil in the food and drinking water) being sucked from the vestibule into the oral cavity proper during the mouth-cleansing phase of swallowing.     

Dental modifications and tool use in the western Great Basin

Nondietary function is an important concern in the study of the human dentition and its role in adaptation. The purpose of the present investigation is to describe and interpret a pattern of dental wear in the anterior dentition of precontact hunter-gatherers that inhabited the western Great Basin. These data are discussed in light of ethnographic documentation as a means by which the archaeological record is linked with associated behavior of the representative populations. A series of 171 dentitions from a group of archaeological localities was examined. Of 1,931 teeth observed, 16 of these showed narrow (0.4-2.0 mm) transverse grooves located on the midocclusal surfaces of anterior teeth. The grooves were restricted in occurrence to five older adult males. Documentation of prehistoric and historic western Great Basin aboriginal populations indicates an adaptation that involves use of plant materials in the production of a variety of utilitarian objects, such as fish nets, basketry, funerary bags, fowling bags, and rope. In postcontact contexts, the anterior dentition has been shown to play an important role in the preparation of materials used for the production of this equipment. It seems most likely, then, that the grooves observed herein resulted directly from the use of the dentition as part of the tool assemblage for the production of other tools.     

Concepts of occlusion: Australian evidence

Longitudinal studies of aboriginal children over a 20-year period have drawn attention to the wide variation in morphological features of the dentition and the way in which occlusal relationships develop. This paper summarizes some important determinants of optimal occlusal development, namely, tooth size relationships within and between dentitions, the patterns of alveolar growth, and tooth migrations during the transition from primary to permanent teeth and the nature of growth changes in the dental arches. Dental occlusion constantly changes throughout life in response to changing functional requirements. Observations limited to cross-sectional material provide an incomplete, and sometimes misleading, concept of dental occlusion and masticatory function.     

冷光美白技术漂白活髓着色牙的临床疗效分析

目的:评价应用Beyond冷光美白技术漂白活髓着色牙的临床疗效。方法:选择牙齿变色病人117例,其中外源性染色牙18例,氟牙症16例,四环素染色牙47例,增龄性变色牙36例,该组病例的前牙及第一前磨牙均为活髓牙,采用Beyond冷光漂白法治疗,美白效果用Vita比色板进行前后比较。结果:外源性着色牙与增龄性变色牙美白疗效较好,平均提高6.09个色阶。对氟牙症疗效也较明显,但颜色分布不均匀,仍会有条纹或斑块状白斑。对轻、中度的四环素牙平均可提高3.46个色阶,重度四环素牙疗效欠佳。结论:Beyond冷光美白技术是目前治疗活髓变色牙特别简捷、安全和有效的方法之一。     

冷光美白技术漂白活髓着色牙的临床疗效分析

目的：评价应用Beyond冷光美白技术漂白活髓着色牙的临床疗效。方法：选择牙齿变色病人117例,其中外源性染色牙18例,氟牙症16例,四环素染色牙47例,增龄性变色牙36例,该组病例的前牙及第一前磨牙均为活髓牙,采用Beyond冷光漂白法治疗,关白效果用Vita比色板进行前后比较。结果：外源性着色牙与增龄性变色牙关白疗效较好,平均提高6．09个色阶。对氟牙症疗效也较明显,但颜色分布不均匀,仍会有条纹或斑块状白斑。对轻、中度的四环素牙平均可提高3．46个色阶,重度四环素牙疗效欠佳。结论：Beyond冷光美白技术是目前治疗活髓变色牙特别简捷、安全和有效的方法之一。     

Size and morphology of the permanent dentition in prehistoric Ohio Valley Amerindians.

Metric and morphological characterizations of the permanent teeth from a total of 155 prehistoric Amerindians are presented. The individuals represent samples from three Ohio Valley burial complexes (considered together as the Late Diffuse group): Glacial Kame, Adena and Ohio Hopewell. Metric data include common measures of central tendency and dispersion. From these measures estimates and analyses of the magnitude of sexual dimorphism and relative variability are presented as well as analyses of the patterns of these estimates. Forty morphological characters are also tabulated. The results indicate a number of provisional hypotheses: the generally larger tooth size of the Late Archaic Indian Knoll when compared to the Late Diffuse groups is consistent with the hypothesis of mitigated selective pressures in more technologically advanced groups; although tooth size is smaller in the Late Diffuse groups, dental morphology is as complex, or more so when compared to the Indian Knoll group. Since morphology and size do not covary exactly the biocultural forces resulting in smaller tooth size do not seem to act as strongly on dental morphology; odontological differences within the Late Diffuse arise primarily between the Glacial Kame-Adena and the Ohio Hopewell. These differences correspond to major biocultural changes in this area; although provisional hypotheses concerning odontological variability are erected, hypotheses concerning evolutionary trends must await the discovery of evolving lineages within these groups; similarities are noted among all compared groups including the pattern and magnitude of sexual dimorphism and relative variability. These parameters may be similar for all eastern Amerindians during this period; finally, the morphology of the deciduous dentition, which generally predicts that of the permanent teeth, is found to be less complex than the permanent teeth. This may be the result of a selective disadvantage for the individuals in the deciduous dentition sample which is reflected in the dentition.     

Embryonic development of Python sebae - II: Craniofacial microscopic anatomy, cell proliferation and apoptosis

This study explores the microscopic craniofacial morphogenesis of the oviparous African rock python (Python sebae) spanning the first two-thirds of the post-oviposition period. At the time of laying, the python embryo consists of largely undifferentiated mesenchyme and epithelium with the exception of the cranial base and trabeculae cranii, which are undergoing chondrogenesis. The facial prominences are well defined and are at a late stage, close to the time when lip fusion begins. Later (11-12d), specializations in the epithelia begin to differentiate (vomeronasal and olfactory epithelia, teeth). Dental development in snakes is different from that of mammals in several aspects including an extended dental lamina with the capacity to form 4 sets of generational teeth. In addition, the ophidian olfactory system is very different from the mammalian. There is a large vomeronasal organ, a nasal cavity proper and an extraconchal space. All of these areas are lined with a greatly expanded olfactory epithelium. Intramembranous bone differentiation is taking place at stage 3 with some bones already ossifying whereas most are only represented as mesenchymal condensations. In addition to routine histological staining, PCNA immunohistochemistry reveals relatively higher levels of proliferation in the extending dental laminae, in osseous mesenchymal condensations and in the olfactory epithelia. Areas undergoing apoptosis were noted in the enamel organs of the teeth and osseous mesenchymal condensations. We propose that localized apoptosis helps to divide a single condensation into multiple ossification centres and this is a mechanism whereby novel morphology can be selected in response to evolutionary pressures. Several additional differences in head morphology between snakes and other amniotes were noted including a palatal groove separating the inner and outer row of teeth in the upper jaw, a tracheal opening within the tongue and a pharyngeal adhesion that closes off the pharynx from the oral cavity between stages 1 and 4. Our studies on these and other differences in the python will provide valuable insights into in developmental, molecular and evolutionary mechanisms of patterning.     

Measurements of tooth wear among Australian Aborigines: I. Serial loss of the enamel crown

The dental casts made from Aboriginal children during the course of a longitudinal growth study in Central Australia provided material for analyzing tooth wear under known environmental conditions. The wear facets produced on the occlusal surfaces were clearly preserved on the dental stone casts and recorded the progress of enamel attrition from ages 6 to 18. These casts were photographed and traced by electronic planimetric methods that automatically recorded the location and size of wear facets on the first and second permanent molars. These areas of worn tooth surface were compared to the total tooth surface. The worn surface was regressed on age to calculate wear rates of each tooth. Discriminant analyses were also performed to determine the significance of dental attrition differences between the sexes at each age group. The total wear on each tooth was highly correlated with age as expected but females wore their teeth at a significantly higher rate than males. The mandibular molars wore more rapidly than maxillary teeth in both sexes. The discriminant analysis successfully grouped 91% of the cases according to age and sex. Pattern of wear, the location, and size of wear facets also differed between age groups and sex. The questions of why there is a difference between male and female wear or why there is greater wear on one arch or arch region have no ready answers. The differing rates and pattern of dental wear do suggest that arch shape and growth rates may be the answer though it has yet to be tested. However, the occlusal surface wear is useful for age estimation in a population and provides a record of shifting masticatory forces during growth.     

Continuous tooth eruption in Australian aboriginal skulls

Increases in the distance from the cemento-enamel junction to the alveolar crest (CEJ-AC) have often been attributed to senile atrophy of the bone or to the effects of periodontitis, without reference to the condition of the alveolar crest. This study investigated the relationship between CEJ-AC distance, tooth wear, gender, site of the CEJ-AC measurements, and age in 161 pre-white-contact Australian aboriginal skulls. Individual teeth were included in the study when there was no evidence of dehiscence, periodontitis, or abscess cavity formation in the supporting alveolar bone. The CEJ-AC distances increased as the severity of attrition increased; in male skulls, CEJ-AC distances were greater than in female skulls for all categories of tooth wear. In general, CEJ-AC distances measured on the mesial aspects of teeth were greater than those recorded distally; lingual distances generally exceeded buccal recordings. The best explanation of these findings and similar reports in the anthropological literature is that continuous tooth eruption occurred without the concomitant coronal movement of alveolar bone. This conclusion has significant ramifications for anthropological, epidemiological, and clinical studies which use the CEJ and AC as reference points when measuring periodontal attachment loss (periodontitis).     

中国早期智人牙齿化石

中国目前较为可靠的早期智人牙齿材料应包括在巢县、许家窑、长阳、周口店新洞和桐梓发现的人类牙齿化石,代表一类与早期组早期智人相当或十分相近的古人类。丁村人类牙齿化石可能是代表晚期组早期智人也可能是代表解剖学上的现代智人。就牙齿材料而言,尚无充分的证据能表明在中国曾同时存在过两种类型的早期智人。     

True grit: A microwear experiment

Recently we noted the effects of experimental diets on microscopic dental wear in the American opossum and concluded that it might prove difficult to distinguish the microwear produced by an insectivorous diet from that produced by some kinds of herbivorous ones. We also noted that wear caused by gritty diets and those containing plant opal, although they might be confused with one another, are easily distinguished from other sorts of dietary wear. Our conclusions have been challenged on the basis that possibly we did not allow sufficient time in the experiments for diagnostic wear patterns to emerge. Additional data reported here show that this is not so. Even in our n “control” animals, fed a relatively soft unabrasive diet, enough time elapsed to produce significant dental wear. A new technique is described which for the first time allows the study of changing patterns of microscopic wear in a living animal over a period of time, thus allowing each animal to serve as its own control. A solution containing a broad-spectrum proteolytic enzyme when applied to the teeth of an anesthetized animal removes the proteinaceous coat (pellicle) which will otherwise obscure wear scratches. Precision dental impressions can then be made which reveal the details of the pattern of microwear on the teeth.     

湖北郧西黄龙洞更新世晚期人类牙齿磨耗与使用痕迹

对2004—2006年在黄龙洞发现的7枚人类牙齿磨耗与使用痕迹的观察显示: 除具有正常牙齿相互接触造成的磨耗外, 黄龙洞人类牙齿还呈现出一些特殊的使用痕迹, 包括明显的前部牙齿釉质破损与崩裂、上颌侧门齿齿冠唇面釉质破损、上颌前部牙齿齿间邻接面沟等。根据这些牙齿使用痕迹集中在前部牙齿, 釉质破损与崩裂主要分布在靠近切缘的上颌门齿唇面及下颌门齿舌面的情况, 推测生活在黄龙洞的更新世晚期人类经常使用前部牙齿从事啃咬、叼衔、或剥离等动作, 并可能将前部牙齿作为工具使用。分布在前部牙齿的齿间邻接面沟提示当时人类经常从事剔牙活动。黄龙洞人类前部牙齿的使用痕迹与当时人类获取、处理及食用附着在骨骼上的筋或肉的动作密切相关, 当时人类的食物构成中可能包含有较多的肉类及粗纤维植物。     

Variation in modern human enamel formation times

Most of what we know about the timing of human enamel formation comes from radiographic studies on children of known age. Here, we present new longitudinal data derived from a histological analysis of tooth enamel. Two samples, one from southern Africa and one from northern Europe, contained all anterior and molar tooth types. Two further samples contained only one tooth type: canines from a medieval Danish sample and third molars from a modern North American sample. Data were collected on 326 molars and 352 anterior teeth. Each tooth was sectioned and prepared for polarized light microscopy. We used daily enamel cross striations to determine cuspal enamel formation time, recorded the periodicity of long-period striae in the lateral enamel, and used this value to calculate enamel formation times for each decile of crown length. We present data that reveal some of the processes whereby differences in enamel formation times arise between our samples. Mean cuspal enamel formation times were similar in southern African and northern European anterior teeth, but differed in certain molar cusps. All the southern African anterior teeth completed enamel formation earlier. The greatest difference in mean chronological age at enamel completion was 5.2 vs. 6.2 years of age in lower canines. However, enamel completion times in the molar teeth showed few differences between the samples, with mean times for the longest forming cusps all falling between 3.0 years and 3.45 years. Our data suggest fewer differences between samples and smaller ranges of variation than in many radiographic studies and present a more realistic picture of worldwide variation in enamel formation times.     

Variation in the developing root cone angle of the permanent mandibular teeth of modern man and certain fossil hominids

The radiographic appearance of the developing root apex of 461 mandibular teeth was studied using ellipsopantomographs of 77 individuals. The angle formed by the mesial and distal aspects of the developing root cone was measured for each quarter of root development in the permanent mandibular teeth of each subject. Large values for this angle in the more coronal part of the root gradually decreased towards the root apex where values were small in all teeth studied. This gradual decrease in the angle of the developing root cone is concordant with the faster increase in root length but slower rates of dentinogenesis reported for the apical region of human teeth in the literature, as the decrease is likely to reflect the increasing numbers of odontoblasts that become involved in root formation as it proceeds apically. The developing root cone angles of one of the five fossil hominid specimens studied (KMN-ER 820) fall outside the range for the developing root cone angle of the developing premolar and permanent second molar roots in modern Homo sapiens and is evidence of a faster rate of root elongation than is typical for modern man.