Relationships between age and dental attrition in Australian aboriginals

Tooth wear scores (ratios of exposed dentin to total crown area) were calculated from dental casts of Australian Aboriginal subjects of known age from three populations. Linear regression equations relating attrition scores to age were derived. The slope of the regression line reflects the rate of tooth wear, and the intercept is related to the timing of first exposure of dentin. Differences in morphology between anterior and posterior teeth are reflected in a linear relationship between attrition scores and age for anterior teeth but a logarithmic relationship for posterior teeth. Correlations between age and attrition range from less than 0.40 for third molars (where differences in the eruption and occlusion of the teeth resulted in different patterns of wear) to greater than 0.80 for the premolars and first molars. Because of the generally high correlations between age and attrition, it is possible to estimate age from the extent of tooth wear with confidence limits of the order of +/- 10 years.     

Patterns of dental wear in the Lengua Indians of Paraguay

Wear patterns were examined on dental casts of 202 living Lengua Indians from the Chaco area of Paraguay. Consideration was given to the development of the molar helicoidal plane, age-related changes in occlusal attrition, coalescence of dentine exposures, interproximal attrition, and erupted crown height. This study lends support to Osborn's theory of the helicoidal plane development by showing that attrition enhances rather than modifies posteruption molar occlusal planes. The rate of interproximal attrition was found to slow down with the eruption and functional initiation of the third molars. Sinuous and cavo-convex interproximal contact areas that are generated with age, however, appeared to be less abrasion resistant than straight surfaces, hence leading to an increase in interproximal attrition rates with advanced age. Maximum crown height reduction occurred between the ages of 20 and 40 years in central incisors, canines, and first molars. Kruskal-Wallis tests and log linera models failed to demonstrate significant sexually dimorphic or antimeric differences in wear patterns of Lengua teeth.     

Development of the helicoidal plane

In this study of thebelicoidal occlusal plane the relationships between tooth wear, the transverse slopes of mandibular molars and dental arch breadths were examined in 74 pre-contemporary Australian Aboriginal skulls. With increasing age and tooth wear the orientation of the mandibular occlusal surfaces increased towards the buccal. The differential occlusal orientation from first to third molars, present at eruption, tended to increase progressively with tooth wear. These functionally induced changes, together with regional differences in relative breadths of the maxillary and mandibular dental arches, are important in the development of abelicoidal occlusal plane.     

Occlusal relief changes with molar wear in Pan troglodytes troglodytes and Gorilla gorilla gorilla

Most research on primate tooth form-function relationships has focused on unworn teeth. This study presents a morphological comparison of variably worn lower second molars (M(2)s) of lowland gorillas (Gorilla gorilla gorilla; n=47) and common chimpanzees (Pan troglodytes troglodytes; n=54) using dental topographic analysis. High-resolution replicas of occlusal surfaces were prepared and scanned in 3D by laser scanning. The resulting elevation data were used to create a geographic information system (GIS) for each tooth. Occlusal relief, defined as the ratio of 3D surface area to 2D planometric area of the occlusal table, was calculated and compared between wear stages, taxa, and sexes. The results failed to show a difference in occlusal relief between males and females of a given taxon, but did evince differences between wear stages and between taxa. A lack of significant interaction between wear stage and taxon factors suggests that differences in occlusal relief between chimpanzees and gorillas are maintained throughout the wear sequence. These results add to a growing body of information on how molar teeth change with wear, and how differences between primate species are maintained at comparable points throughout the wear sequence. Such studies provide new insights into form-function relationships, which will allow us to infer certain aspects of diet in fossils with worn teeth.     

Technical note: Occlusal fingerprint analysis: Quantification of tooth wear pattern

Information about food ingestion and mastication behavior during the lifespan of an individual is encoded in the dental occlusal wear pattern. To decode this information, we describe a new method called occlusal fingerprint analysis (OFA). Structural parameters of wear facets on the occlusal surface of teeth are quantified from digitized casts for the interpretation of occlusal aspects. The OFA provides an individual three‐dimensional dental occlusal compass that indicates the major pathways of interaction between antagonists, revealing information about development, spatial position, and enlargement of wear facets. Humans develop a very similar overall pattern of crown contacts, although specific characteristics of wear facets reflect an individual's occlusal relationships and masticatory behavior. We hypothesize that the wear pattern is a unique character and therefore valuable for individual identification. Furthermore we suggest that OFA, when further developed, may be useful for identification of behavioral, biological, and chemical factors affecting crown morphology. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.     

Dental arch shape and tooth wear variability

The rapid rate of tooth wear frequently reported among certain contemporary aboriginal populations has often been attributed to dietary form and abrasives. Several investigators have reported a close correlation between food bulk and the wear planes formed over the dental arches, i.e., steep oblique wear vs. flat horizontal planes. In this investigation we demonstrate that arch shape is an additional and a significant factor influencing the distribution of wear facets and exposed dentin over occlusal surfaces. We examined 64 dental stone casts of Aboriginals from Yuendumu, Central Australia, born between 1900 and 1940. These casts offer a record of the variety of tooth wear and arch forms and their interrelationships. This group of individuals, some subsisting on abrasive and some on soft diets, have dentition which exhibit various wear rates and wear patterns probably due to the diversity of arch shape, size, and occlusal relationships. Hypsiloid or U-shaped maxillas had a more buccally directed wear in contrast to the parabolic or hyperbolic forms, which exhibit a heavier lingual loading. Varying occlusal conditions also contribute to differing wear patterns over the arches. Individuals with alternate intercuspation, for example, have a more horizontally directed wear. These and other conditions of shape, size, and occlusion emphasize the importance of morphological factors in the production of tooth wear rates and patterns in addition to dietary abrasives.     

Dental wear and oral pathology: possible evidence and consequences of habitual use of teeth in a Swedish Neolithic sample

Atypical wear and oral lesions were studied in the dental remains from the Middle Neolithic Pitted Ware Culture site Ajvide on the island of Gotland in the Baltic Sea. Teeth (n = 764) from 17 males and 11 females were examined microscopically to document unusual wear, assess wear patterns and oral lesions as evidence of habitual behavior, and determine their effect on the oral health of this population. Five atypical wear types were observed: occlusal facets, occlusal excessive load, labial vertical striae, labial horizontal striae, and interproximal striae. Three oral lesions were recorded: chipping, periapical lesions, and dental tilting. Results indicate that teeth were used in a habitual manner at Ajvide, based on the morphology and regularity of the patterns of atypical wear. Differences were observed between the sexes, indicating gender-related differences in the habitual use of teeth. Some wear categories showed a significant correlation with age, signifying increased or accumulated wear with age. Statistically significant positive correlations were found in the molars between occlusal excessive load wear and periapical lesions as well as tilting. Other apparent links were also observed between chipping and vertical striae as well as excessive load, although these were not significant. This suggests a relationship between dental wear and dental pathologies at this site, suggesting that habitual use of teeth indirectly affected the general oral health at the site. Wear patterns, furthermore, seem to mirror both frequent activities as well as single events.     

Brief communication: Identification reassessment of the isolated tooth Krapina D58 through occlusal fingerprint analysis

High variability in the dentition of Homo can create uncertainties in the correct identification of isolated teeth. For instance, standard tooth identification criteria cannot determine with absolute certainty if an isolated tooth is a second or third maxillary molar. In this contribution, using occlusal fingerprint analysis, we reassess the identification of Krapina D58 (Homo neanderthalensis), which is catalogued as a third maxillary molar. We have hypothesized that the presence/absence of the distal occlusal wear facets can be used to differentiate second from third maxillary molars. The results obtained confirm our hypothesis, showing a significant difference between second and third maxillary molars. In particular we note the complete absence of Facets 7 and 10 in all third molars included in this analysis. The presence of these facets in Krapina D58 eliminates the possibility that it is a third maxillary molar. Consequently it should be reclassified as a second molar. Although this method is limited by the degree of dental wear (i.e., unworn teeth cannot be analyzed) and to individual molars in full occlusion, it can be used for tooth identification when other common criteria are not sufficient to discriminate between second and third maxillary molars. Am J Phys Anthropol 143:306–312, 2010. © 2010 Wiley‐Liss, Inc.     

Changes in orientation of attritional wear facets with implications for jaw motion in a mixed longitudinal sample of Propithecus edwardsi from Ranomafana National Park, Madagascar

In many mammalian species, the progressive wearing down of the teeth that occurs over an individual's lifetime has the potential to change dental function, jaw movements, or even feeding habits. The orientation of phase-I wear facets on molars reveals the direction of jaw movement during the power stroke of mastication. We investigated if and how molar wear facets change with increasing wear and/or age by examining a mixed longitudinal dataset of mandibular tooth molds from wild Propithecus edwardsi (N = 32 individuals, 86 samples). Measurements of the verticality of wear facets were obtained from three-dimensional digital models generated from μCT scans. Results show that verticality decreases over the lifetime of P. edwardsi, a change that implies an increasingly lateral translation of the jaw as the teeth move into occlusion. A more transverse phase-I power stroke supports the hypothesis that these animals chew to maximize longevity and functionality of their teeth, minimizing the "waste" of enamel, while maintaining sharp shearing crests. Results of this study indicate that wear facet verticality is more closely correlated with age than overall amount of tooth wear, measured as area of exposed dentin, suggesting that age-related changes in cranial morphology may be more responsible for adjustments in jaw motion over the lifetimes of Propithecus than wear-related changes inthe shape of occluding teeth. Finally, the rate of decrease in wear facet verticality with age is greater in males than in females suggesting differences in development and/or access to resources between the sexes in this species.     

The caries-attrition competition

Contradictory reports on the interreation of caries and attrition concerning their destructive activity at the occlusal surface of teeth required more investigation. Some suggested that the abrasive action of attrition worked against the progress of decay. Others proposed that attrition facilitated the development of caries in dentine exposed due to the dental wear. A comparison of the condition of teeth in western societies from an intermediate stage, with the preceding period characterized by excessive attrition, and with the following period of ongoing reduction of dental wear, might elucidate the mutual relationship. For this reason the almost complete dental assemblage of fifty men, whalers buried during their short sojourn in the Arctic in the 17th and 18th centuries at a Dutch whaling station, and the data of their contemporaries, were evaluated. The results confirmed the proposition that the rise in caries incidence from (pre-) medieval times on, was associated with an ongoing fall of dental attrition. Within this sample of an intermediate phase, one sees that the percentage of carious molars decreases considerably when the degree of dental wear increases. Besides, at the occlusal surface the decay was almost exclusively located in the natural fissures and pits of teeth, not in the exposed dentine due to wear. These findings strongly suggest a competitive relationship between progress of caries and attrition. The best impression of the attrition rate is gained by linkage of degree of dental attrition (i.e. functional age) to age at death. The wide age ranges fitting to the degrees of molar wear make it hazardous to use attrition for age determination.     

Modular Wear Facet Nomenclature for mammalian post-canine dentitions

Abstract

Dental wear facets on the occlusal surface of premolars and molars are traces of their main function, the mastication and therefore reflect masticatory movements and also paramasticatory (i.e. non-dietary use of teeth) behavior. Here we present the Modular Wear Facet Nomenclature applicable to most mammalian dentitions. Topographic positions of wear facets in relation to the major cusps and crests of the teeth are used to designate the areas of the occlusal surface the facets occupy (e.g. their mesial, distal, lingual, or buccal position). Previous published systems for labeling wear facets have been inconsistent with each other. Therefore, we provide a synoptic review of the most widely-used terminologies, and introduce the alternative Modular Wear Facet Nomenclature. This nomenclature aims to overcome the difficulties caused by the existing inconsistent wear facet terminologies. Our new approach is applicable to dentitions where the occlusal morphology does not change significantly for most of the lifetime of the animal. In those dentitions, the primary occlusal surfaces are not significantly modified as wear facets become more extensive with wearing. This appears to be a common pattern in pre-tribosphenic, tribosphenic molars, and the teeth derived from tribosphenic precursors (e.g. bunodont molar morphologies). In teeth where the secondary occlusal surface is functionally intensely modified (i.e. high-crowned and evergrowing teeth with large areas of dentine exposed) any facet labeling system appears to be challenging, since the identification of individual facets is blurred and their spatial position may be indeterminable.     

同口牙齿的磨耗级比较

本文比较和分析了同口同侧牙齿的相应的磨耗级,提供了除臼齿以外的牙齿磨耗年龄变化依据。同时还对上下对应牙、两侧对称牙的磨耗级作了比较和分析。     

Brief communication: Subvertical grooves on interproximal wear facets from the El Sidrón (Asturias,Spain) Neandertal dental sample

The distribution of subvertical grooves on interproximal wear dental facets from the El Sidrón (Asturias, Spain) Neandertals is described and analyzed. Out of 93 teeth, 64.5% present subvertical grooves, including a high frequency (50%) on the anterior dentition. Contrary to some studies, subvertical grooves from adjacent facets perfectly overlap each other and do not interdigitate, probably forming small channels. Both the facet and the groove surface share the same polished appearance, suggesting a common origin. Statistical analyses reveal that the number of grooves is neither dependent on the degree of occlusal wear, nor on the position on the tooth or the individual's age. However, facet width is an important factor determining the number of subvertical grooves. The etiology of subvertical grooves formation on Neandertal teeth remains unclear. Am J Phys Anthropol, 2010. © 2010 Wiley‐Liss, Inc.     

Dental wear study in a 14th century skull of the Sao tribe, Cameroon

The aim of this work was to study the wear affecting the almost complete dentition of a Sao individual fossil from Cameroon prehistory (XIVth century). Occlusal surfaces of the fossil fragile pieces were plaster replicated with an original technique adapted from usual dental impression methods (silicon elastomer polymerising by addition). Axial macro-photographs of both sectional dental casts and original pieces made it possible to produce drawings of the occlusal areas on transparencies in order to superimpose the lateral hemiarch counterparts in their optimal intercuspal position. The study of interarch contacts was completed by confronting and observing the occluding position of hemiarch replicas. The occlusal analysis revealed that the wear extent was equivalent on left and right molars. Hall's occlusal wear index and Van Reenen and Reinach's classification of proximal wear allow assessment of the degree of wear extent on premolar and molar sections in relation to the side or the arch observed. The even bilateral proximal and occlusal wears observed on the different kinds of homologous teeth appeared as the main contributor to this well-balanced interarch occlusion. The mandibular incisor losses and the particular type of wear affecting lower canines led to the conclusion of the presence of a labret, a great number of which was found in the area. According to Miles' method of age assessment based on tooth wear, the pieces studied belonged to an individual between 30 and 40 years old.     

Association of occlusal wear facets in patients with temporomandibular disorders

Occlusal changes were important factors in temporomandibular disorder (TMD). It is of interest to evaluate the association of occlusal wear facets in TMD patients. We used a dataset of 49 patients with and without TMD for this study. Occlusal wear facets were evaluated using Smith and Knight tooth wear index. Data shows that teeth wear was present more in patients with TMD (55%). The age group 26-40 years showed high prevalence of teeth wear (grade1) in TMD patients (P value = 0.034). TMD was present more in females than males. Female (54%) patients with TMD showed more teeth wear compared to males. Most patients with TMD showed posterior teeth wear (61%) than generalized teeth wear. Thus, association was present between occlusal teeth wear and TMD patients especially in the age group of 26-40 years. Hence, proper evaluation of occlusal factors will aid in early diagnosis of TMDs.     

Dental wear,wear rate,and dental disease in the African apes

The African apes possess thinner enamel than do other hominoids, and a certain amount of dentin exposure may be advantageous in the processing of tough diets eaten by Gorilla. Dental wear (attrition plus abrasion) that erodes the enamel exposes the underlying dentin and creates additional cutting edges at the dentin‐enamel junction. Hypothetically, efficiency of food processing increases with junction formation until an optimal amount is reached, but excessive wear hinders efficient food processing and may lead to sickness, reduced fecundity, and death. Occlusal surfaces of molars and incisors in three populations each of Gorilla and Pan were videotaped and digitized. The quantity of incisal and molar occlusal dental wear and the lengths of dentin–enamel junctions were measured in 220 adult and 31 juvenile gorilla and chimpanzee skulls. Rates of dental wear were calculated in juveniles by scoring the degree of wear between adjacent molars M1 and M2. Differences were compared by principal (major) axis analysis. ANOVAs compared means of wear amounts. Pearson correlation coefficients were calculated to compare the relationship between molar wear and incidence of dental disease. Results indicate that quantities of wear are significantly greater in permanent incisors and molars and juvenile molars of gorillas compared to chimpanzees. The lengths of dentin–enamel junctions were predominantly suboptimal. Western lowland gorillas have the highest quantities of wear and the most molars with suboptimal wear. The highest rates of wear are seen in Pan paniscus and Pan t. troglodytes, and the lowest rates are found in P.t. schweinfurthii and G. g. graueri. Among gorillas, G. b. beringei have the highest rates but low amounts of wear. Coefficients between wear and dental disease were low, but significant when all teeth were combined. Gorilla teeth are durable, and wear does not lead to mechanical senescence in this sample. Am. J. Primatol. 72:481–491, 2010. © 2010 Wiley‐Liss, Inc.     

郑州汪沟遗址仰韶文化居民的牙齿磨耗及口腔健康状况

对汪沟遗址出土的174例仰韶文化居民的2816枚牙齿进行统计与分析,计算出牙齿的平均磨耗等级和前后部牙齿磨耗差别指数,统计特殊磨耗、龋齿、骨质隆起在样本中的出现率。结果显示,汪沟组牙齿平均磨耗等级为3.403262级,男性牙齿平均磨耗等级为3.63级,女性为3.61级;男女两性牙齿磨耗差异不显著（p>0.05);前后部牙齿磨耗差别指数比达到1:1;出现26例由于深覆牙合导致的特殊磨耗;臼齿咬合面凹坑式磨耗出现率为2.50%;龋齿患病率68.97%,龋齿率26.56%,龋均4.30;骨质隆起的出现率为5.20%,颌骨粗壮程度不显著。汪沟人群的牙齿磨耗程度总体偏轻,牙齿磨耗程度与河南下王岗组居民接近。基于以上特点,我们认为中原地区仰韶文化人群在饮食结构和用牙习惯上存在一定的共性。     

Sex-specific strategies of dentine depletion in red deer

Worn teeth in herbivore ungulates may be related to lower efficiency in mastication and hence lower performance. However, selection should favour maximal performance in terms of body mass and reproductive capacity during reproductive lifespan, when permanent teeth are already partially worn. We hypothesize that wear rate may respond to a strategy of use of tooth materials (notably dentine), which balances instantaneous wear rate and performance against tooth preservation for future performance and reproduction. In the present study, we investigated 4151 carcasses of Iberian red deer Cervus elaphus hispanicus and show that more worn molars were not related to lower performance throughout age. By comparing between sexes, tooth wear rates were smaller in females than in males, but the relationship between tooth wear and body performance also differed between the sexes: females did not show a significant relationship between tooth wear and performance but males with more worn teeth were in general heavier and had larger antlers until senile age, when more depleted teeth were related to smaller antlers. These results reveal, for the first time, sex-specific lifetime strategies of dentine expenditure: maintenance of performance ability throughout a longer reproductive lifespan in females, compared with maximizing current performance by depleting dentine reserves within a shorter lifespan in males.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 487–497.     

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.     

Dental topography and molar wear in Alouatta palliata from Costa Rica

Paleoprimatologists depend on relationships between form and function of teeth to reconstruct the diets of fossil species. Most of this work has been limited to studies of unworn teeth. A new approach, dental topographic analysis, allows the characterization and comparison of worn primate teeth. Variably worn museum specimens have been used to construct species-specific wear sequences so that measurements can be compared by wear stage among taxa with known differences in diet. This assumes that individuals in a species tend to wear their molar teeth in similar ways, a supposition that has yet to be tested. Here we evaluate this assumption with a longitudinal study of changes in tooth form over time in primates. Fourteen individual mantled howling monkeys (Alouatta palliata) were captured and then recaptured after 2, 4, and 7 years when possible at Hacienda La Pacifica in Costa Rica between 1989-1999. Dental impressions were taken each time, and molar casts were produced and analyzed using dental topographic analysis. Results showed consistent decreases in crown slope and occlusal relief. In contrast, crown angularity, a measure of surface jaggedness, remained fairly constant except with extreme wear. There were no evident differences between specimens collected in different microhabitats. These results suggest that different individual mantled howling monkeys wear their teeth down in similar ways, evidently following a species-specific wear sequence. Dental topographic analysis may therefore be used to compare morphology among similarly worn individuals from different species.