Interproximal grooving and task activity in Australia

How geographical origin and dietary habits interact with the shape of cortical mandibular sections? A geometric morphometrics study in an archaeological context

OBJECTIVE

Mandibular shape is strongly influenced by biomechanics, particularly during dietary shifts that often occurred in past populations. The relationship is considered extremely complex as development of the mandible is a multifactorial process. Since cortical bone distribution is purportedly more biomechanically sensitive than external shape, comparison of its distribution in past populations can provide new input to understand this complex relationship. The present study examined the effects of geographical origin and dietary habits on the internal anatomy of the mandibular corpus and symphysis.

DESIGN

A morphometric analysis was conducted on 72 mandibles from different populations, sampled by their geographical origin and subsistence strategies. Procrustes ANOVAs were performed to test the impact of section-plane location, geographical origin, and dietary habits on the groups' shapes.

RESULTS

The specimens' geographical origin and dietary habits had a significant effect on the shapes of the sections (Generalized Goodall F-test, F = 3.2745, df = 6, 304: p < 0.001 and F = 3.7007, df = 4, 306: p < 0.001).

CONCLUSION

Geographical origin and dietary habits influenced the shape of the mandibular sections in our sample. These relationships become more complex when analysed in isolated sections. Indeed, this study revealed that symphysis sections could be predominantly influenced by individual variables, whereas intermediate sections of the corpus could be predominantly influenced by populational variables. Future studies could focus on specific sections to better identify the specific "rules of dependence" in each cross-section.

Evidence of habitual behavior from non-alimentary dental wear on deciduous teeth from the Middle and Upper Paleolithic Cantabrian region, Northern Spain

The use of 'teeth as tools' (non-masticatory or cultural-related dental wear) has largely been employed as a proxy for studying of past human behavior, mainly in permanent dentition from adult individuals. Here we present the analysis of the non-masticatory dental wear modifications on the deciduous dentition assigned to eight Neanderthal and anatomically modern human subadult individuals from Mousterian to Magdalenian technocultural contexts in the Cantabrian region (Northern Spain). Although preliminary, we tentatively suggest that these eight subadults present activity-related dental wear, including cultural striations, chipped enamel, toothpick grooves, and subvertical grooves. We also found evidence of habitual dental hygienic practices in the form of toothpicking on a deciduous premolar. Orientation of the cultural striations indicates similar handedness development as in modern children. Taken together, these dental wear patterns support the participation of young individuals in group activities, making them potential contributors to group welfare. This study potentially adds new evidence to the importance of the use of the mouth in paramasticatory activities or as a third hand throughout the Pleistocene, which can be confirmed with a more specific reference sample.

Biocultural diversity in Late Pleistocene/Early Holocene Africa: Olduvai Hominid 1 (Tanzania) biological affinity and intentional body modification

OBJECTIVES

The dentition of Olduvai Hominid 1 (OH1) exhibits an anomalous pattern of dental wear that was originally attributed to either intentional cultural modification (filing) or plant processing behaviors. A differential diagnosis of the wear and assessment of the biological affinity of OH1 is presented.

MATERIALS AND METHODS

Macroscopic and microscopic observations of all labial and buccal tooth surfaces were undertaken to assess wear patterns. A multivariate analysis of mandibular morphology of OH1 compared to other Late Pleistocene, Holocene, and recent modern humans was used to ascertain biological affinity.

RESULTS

The morphological variation of the OH1 mandible is closely aligned with variation in penecontemporaneous fossils from Africa and outside that of recent humans. The concave wear facets exposing dentin on the labial surfaces of all three preserved mandibular incisors is confirmed. Substantial loss of labial/buccal surfaces was documented on the surfaces of all in situ maxillary and mandibular canines, premolars, and molars ranging from distinct facets with well-defined edges, to blunting or "polishing" around areas of maximum buccal curvature. The wear on both the anterior and postcanine teeth closely resemble that caused by adornments ("labrets") worn in lower-lip and buccal facial piercings known from bioarchaeological and ethnographic contexts. The wear pattern suggests that the OH1 wore three facial piercings-two buccal/lateral and a medial one in the lower lip.

DISCUSSION

Our findings suggest that the expression of social identities through intentional body modification is more diverse than previously documented elsewhere in Africa during the Late Pleistocene (i.e., ablation) and Early Holocene (i.e., ablation, chipping, and filing).

Root grooves on two adjacent anterior teeth of Australopithecus africanus

Tooth root grooves and other ante-mortem dental tissue loss, not associated with caries found on or near the cementoenamel junction (CEJ), are commonly termed non-carious cervical lesions. Three main processes are implicated in forming these lesions: abrasion, dental erosion, and abfraction. As yet, these lesions have not been described in non-Homo hominins. In this study, South African fossil hominin collections were examined for evidence of any type of non-carious cervical lesion. Only one individual shows ante-mortem root grooves consistent with non-carious cervical lesions. Two teeth, a mandibular right permanent lateral incisor (STW 270) and canine (STW 213), belonging to the same Australopithecus africanus individual, show clear ante-mortem grooves on the labial root surface. These lesions start below the CEJ, extend over a third of the way toward the apex, and taper to a point towards the lingual side. The characteristics of these grooves suggest the predominant aetiology was erosive wear. In addition, they are extremely similar to clinical examples of dental erosion. These are the oldest hominin examples of non-carious cervical lesions and the first described in a genus other than Homo. Further, the lesions suggest that this individual regularly processed and consumed acidic food items.

The dawn of dentistry in the late upper Paleolithic: An early case of pathological intervention at Riparo Fredian

OBJECTIVES

Early evidence for the treatment of dental pathology is found primarily among food-producing societies associated with high levels of oral pathology. However, some Late Pleistocene hunter-gatherers show extensive oral pathology, suggesting that experimentation with therapeutic dental interventions may have greater antiquity. Here, we report the second earliest probable evidence for dentistry in a Late Upper Paleolithic hunter-gatherer recovered from Riparo Fredian (Tuscany, Italy).

MATERIALS AND METHODS

The Fredian 5 human consists of an associated maxillary anterior dentition with antemortem exposure of both upper first incisor (I¹ ) pulp chambers. The pulp chambers present probable antemortem modifications that warrant in-depth analyses and direct dating. Scanning electron microscopy, microCT and residue analyses were used to investigate the purported modifications of external and internal surfaces of each I¹ .

RESULTS

The direct date places Fredian 5 between 13,000 and 12,740 calendar years ago. Both pulp chambers were circumferentially enlarged prior to the death of this individual. Occlusal dentine flaking on the margin of the cavities and striations on their internal aspects suggest anthropic manipulation. Residue analyses revealed a conglomerate of bitumen, vegetal fibers, and probable hairs adherent to the internal walls of the cavities.

DISCUSSION

The results are consistent with tool-assisted manipulation to remove necrotic or infected pulp in vivo and the subsequent use of a composite, organic filling. Fredian 5 confirms the practice of dentistry-specifically, a pathology-induced intervention-among Late Pleistocene hunter-gatherers. As such, it appears that fundamental perceptions of biomedical knowledge and practice were in place long before the socioeconomic changes associated with the transition to food production in the Neolithic.

Evidence of toothpick groove formation in Neandertal anterior and posterior teeth

OBJECTIVES

During the microscopic examination of the Neandertal dentitions from El Sidrón (Spain) and Hortus (France), we found unusual fine parallel microstriations on the mesial and distal sides of all tooth types, near the cervix. As its appearance was similar to toothpick grooves described in other Homo species, it could correspond to early stages on its formation. To test this hypothesis we developed an experimental replication of a groove using grass stalks.

MATERIALS AND METHODS

Comparisons between 204 isolated Neandertal teeth and the two experimental dental specimens corroborate that the marks correspond to initial stages of toothpick groove formation, and we propose a five-grade recording scale that summarized the groove formation process.

RESULTS

Using this new recording procedure, we found that Hortus individuals have higher incidence of this trait (eight individuals out of nine) than the El Sidrón individuals (nine out of 11). Toothpick grooves from El Sidrón show the earliest stages of development, whereas the grooves found on Hortus Neandertals were well-developed. Toothpick grooves were also found in 21 incisors and canines.

CONCLUSIONS

These differences could be due to the more advanced occlusal dental wear in Hortus individuals, maybe age-related and with a more meat-based diet maybe favoring the inclusion of food debris and thus probing as the cleaning methodology. Our results allow the identification and characterization of incipient toothpick grooves on the human fossil record and contribute to increase our knowledge on Neandertals behavioral and oral care habits.

Abfraction: A review

Abfraction (AF) is the pathological loss of tooth substance caused by biomechanical loading forces that result in flexure and failure of enamel and dentin at a location away from the loading. The theory of AF is based primarily on engineering analyses that demonstrate theoretical stress concentration at the cervical areas of the teeth. However, the theory is not yet proven and there are explanations against it. AF lesions present primarily at the cervical region of the dentition and are typically wedge-shaped, with sharp internal and external line angles. Diagnosis of AF plays a very important role in the management of patients. The aim of the present narrative review is to comprehensively discuss the historical, etiopathogenetic, clinical, and diagnostic and treatment aspects of AF.

Functional dental occlusion: an anthropological perspective and implications for practice

Physiologic changes occur in dental occlusion throughout life, resulting from the interplay between functional demands and reciprocating adaptive responses. These changes have been reported in the anthropological literature and they reflect evolutionary changes in the human stomatognathic system during the Paleolithic, hunter-gatherer period. Specific occlusal changes occur in response to different environments, leading to extensive variation within and between extinct and extant human populations. For example, functional demands can cause occlusal and interproximal tooth wear, resulting in shortening of the dental arch, continual tooth eruption and changes in masticatory patterns. Since the advent of farming through to our current industrialized culture, functional demands on the human masticatory system, and its adaptive responses to these demands, have been reduced considerably. Indeed, it is only occasionally that functional demands are severe enough to lead to obvious pathology in the modern human dentition. In contrast to normal masticatory activity, 'modern-day conditions' such as dental caries, periodontal disease and erosion, can lead to significant changes in dental occlusion that are pathological and need to be treated. The masticatory system is a dynamic, functional unit that displays considerable change over a lifetime. In this concept paper, it is proposed that modern human populations living in industrialized environments display dental occlusions that can be considered to be 'neotenous'; that is, our dentitions tend to reflect an unworn stage of our ancestors that was only seen in infants, juveniles and young adults. Clinicians can draw on both phylogenetic and ontogenetic perspectives of 'functional dental occlusion' to differentiate continual physiological changes occurring over time that require ongoing review, from pathological responses that require intervention.

Toothpicking and periodontal disease in a Neanderthal specimen from Cova Foradà site (Valencia, Spain)

We present a Neanderthal maxilla (CF-1) from Cova Foradà site (Oliva, Valencia, Spain) with periodontal disease and evidence of attempts to alleviate pain with the use of a toothpick. Two interproximal grooves have been found on the distal surfaces of the upper left Pm³ and M¹ of CF-1 maxilla. The location, morphology and size of the grooves coincide with other interproximal grooves found on the teeth of other fossil specimens. Heavy dental wear and periodontal disease would have caused the Cova Foradà Neanderthal specimen pain and discomfort, which the individual attempted to mitigate using some kind of dental probe.

Hunter-gatherer variability: Dental wear in South Australia

Often it is assumed that hunter-gatherer dentitions are dominated by heavy attrition. Recent analyses, however, have shown unexpected variability in the pattern of wear between groups. It had been previously noted that wear differed between neighboring groups on the Murray River, Australia. This analysis extends that geographic scope as well as focusing on wear across the dentition, including the premolars. The samples came from coastal and riverine regions of southern Australia. The analysis used records from the Yorke Peninsula, Adelaide Plains (Gillman site), and Euston regions. These were compared with previously published work from the Adelaide Plains and four locations on the Murray River. The results confirm the overall severity of wear but reveal systematic differences between the samples in terms of the pattern of wear. Heavy wear on the incisors and canines is observed among males from the Euston, Kaurna, Middle A, Murray Mouth, and Yorke Peninsula samples but with marked intra-individual variability. Extensive premolar wear is noted among females from Kaurna and Middle B samples as well as among males and females from Euston. It is argued that these patterns relate to gendered non-masticatory use of teeth and reliance upon bulrush (Typha spp.) and related species for both food and fiber among some groups. We argue that analyzing the degree of variability within samples and across all teeth provides a more nuanced understanding of dental wear among hunter-gatherers.

An anthropological perspective: another dimension to modern dental wear concepts

For many years, research on tooth wear by dental academics has been diametrically opposite to that of anthropological research, with each discipline having a different understanding as to the nature of the wear processes. Dental focus revolved around preventive and restorative considerations while the anthropological focus was a biological understanding related to human evolution, diet, environment, form, and function and included all the craniofacial structures. Introducing the anthropological perspective into modern dentistry gives an insight into the “bigger picture” of the nature and extent of tooth wear. By combining anthropological evidence with clinical knowledge and experience, it is most likely to provide the best-informed and biologically based approach to the management of tooth wear in modern societies.

Non-carious cervical lesions on permanent anterior teeth: a new morphological classification

BACKGROUND

Various cross-sectional forms of non-carious cervical lesions have been described but no formal morphological classification system has been developed. The aims of this study were to describe the spectrum of common morphological forms of non-carious cervical lesions observed within a large sample of extracted human permanent anterior teeth and to develop a system for classification based on morphological features.

METHODS

Over 15,000 extracted permanent anterior teeth were examined macroscopically under illumination at 2x magnification. Well-defined, descriptive categories were formed, based on observable non-carious cervical lesion features and using terminology currently reported in the literature. The lesions were then sorted into these categories.

RESULTS

Five hundred and forty-two non-carious cervical lesions were identified on 15 289 teeth extracted in the early to mid 20th century, representing a frequency of 3.5%. The main categories developed were "shallow", "concave", "wedge-shaped", "notched", and "irregular".

CONCLUSIONS

The new morphological classification system provides an alternative to presently used systems based on aetiology, and should facilitate future research on non-carious cervical lesions.

Gradients of occlusal wear in hunter-gatherers and agriculturalists

Occlusal wear was recorded in maxillary teeth from three North American late Archaic (3385 +/- 365 cal BC) hunter-gatherer sites (n = 306) and late Anasazi-early Zuni agricultural sites ( approximately 1300 AD) (n = 87). Comparisons were undertaken using descriptive and inferential statistics to determine differences between these groups, and along the maxillary tooth row. The hunter-gatherers had a significantly greater percentage of occlusal wear than the agriculturalists. For both hunter-gatherers and agriculturalists, occlusal wear was greatest on the central incisors and first molars. The third molars had the least amount of wear. It was inferred from these results that the hunter-gatherers had a more abrasive diet, and different daily task activities compared to the agriculturalists. One further finding was that wear patterns on anterior and posterior teeth are influenced by the order that teeth erupt into the jaw, as well as diet and behavior.

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.

A qualitative assessment of non-carious cervical lesions in extracted human teeth

BACKGROUND

Opinions vary about the causes of non-carious cervical lesions (NCCLs). They have been attributed to toothbrush abrasion, acid corrosion (commonly termed dental erosion), and abfraction. The purpose of this study was to examine the microwear details of NCCLs in a collection of extracted human teeth using scanning election microscopy (SEM).

METHODS

Negative replicas of large NCCLs in 24 extracted human teeth were obtained in polyvinylsiloxane impression material (Light Body Imprint II, 3M ESPE) and viewed under SEM.

RESULTS

All NCCLs extended from the cemento-enamel junction to the root surface and they displayed a variety of wedge-shaped appearances. There was evidence of both abrasion and corrosion in 18 of the 24 teeth (75.0 per cent), abrasion only in one tooth (4.2 per cent) and corrosion only in five teeth (20.8 per cent). Horizontal furrows with smooth edges and minor scratch marks, characteristic of abrasion and corrosion, were noted in 13 teeth (54.2 per cent).

CONCLUSIONS

Based on microscopic assessment of a sample of extracted teeth, it appears that abrasion and corrosion are common associated aetiological factors in the formation of NCCLs.

Nonalimentary tooth use in prehistory: an example from early Holocene in Central Sahara (Uan Muhuggiag, Tadrart Acacus, Libya)

Signs of nonalimentary tooth use were observed on the dentition of an adult male from a single burial excavated in an area close to the Uan Muhuggiag rock shelter (Tadrart Acacus, Libya), dated to more than 7800 uncalibrated years BP, that represents the most ancient human remain found in the Libyan Sahara, and provides a first glimpse of human adaptation in the early Holocene of this region. The wear pattern shows large grooves running across the occlusal surfaces of maxillary and mandibular anterior teeth and premolars. The results of macroscopic and microscopic observation, together with scanning electron microscope (SEM) examination and experimental tests, suggest that the microdamage might be due to repeated friction of vegetal fibers, probably as a consequence of basket making, net production, or mat processing. Further data are needed to allow us to distinguish among plant-oriented activities related to food acquisition (e.g., rope and net processing), food storage (e.g., basket making), or domestic handicraft (e.g., mat processing), whose implications may generate different interpretations of sexual division of labor.

Additional human remains from Blombos Cave, South Africa: (1999-2000 excavations)

The uppermost Middle Stone Age (MSA) layers at Blombos Cave contain high densities of Still Bay bifacial points. Information from other regional sites places the Still Bay prior to the Howiesons Poort industry, which has been dated at 65-70 ka. The Blombos Cave MSA strata have yielded nine human teeth or dental fragments. Four that were recovered during the 1997-1998 excavations have been published elsewhere. The remaining five were discovered during the 1999-2000 field seasons; these are described here. Three of the new specimens are deciduous teeth, and two are permanent premolar and molar crown fragments. The entire dental sample probably represents at least five and as many as seven individuals. The deciduous teeth from the upper MSA levels are likely to have been exfoliated in the cave. One deciduous tooth and the permanent tooth fragments from the lower MSA levels probably represent three individuals who died in or near the cave. The Blombos Cave premolars preserve horizontal circum-cervical striae suggestive of palliative tooth pick use. Approximately half of the permanent and deciduous crown diameters exceed those of recent Africans; for the remainder, the fossil values fall among modern African sample means. The Blombos Cave tooth crowns tend to be smaller than the majority of penecontemporaneous Neandertal teeth. The morphology of the Blombos Cave di is comparable to MSA homologues from the nearby, and presumably somewhat younger site of Die Kelders Cave 1.

New human teeth from Middle Stone Age deposits at Klasies River, South Africa

Since 1984, the main site at Klasies River has been re-investigated. Human remains, animal bones and stone artefacts have been collected from the LBS, SAS and other stratigraphic members, and these discoveries help to establish the antiquity of anatomically near-modern populations practicing a Middle Stone Age way of life on the southern coast of Africa. Several teeth found in the lower SAS levels in 1989-1991 can be matched in recent South African populations. Two complete upper molars representing one individual have crowns that are relatively short mesiodistally. These specimens are small in comparison to black South African homologues, but MD and BL dimensions fall close to the averages for San burials. This evidence confirms that several of the Klasies individuals have very small molars, while others have cheek teeth that are close to the upper limits for size variation in recent Africans. The new material is in keeping with the view that sex dimorphism within this Middle Stone Age population may be pronounced.

A review of interproximal wear grooves on fossil hominin teeth with new evidence from Olduvai Gorge

Interproximal (approximal) grooves at the cementum-enamel junction of premolar and molar teeth have been observed in a broad range of human ancestors and related extinct species from 1.84 million years ago to the present. Many hypotheses have been presented to explain the aetiology of these grooves, though their form and positioning are most consistent with tooth-picking behaviours. This paper reviews occurrences of interproximal grooves in the cheek teeth of modern and fossil humans, evaluates hypotheses on their cause, and reports on a previously undescribed groove found in OH 60, a molar tooth from Olduvai Gorge. This specimen is among the earliest to show such grooving, and is most likely attributable to Homo erectus. It is concluded that, because interproximal grooves have been observed only on Homo teeth, they probably reflect a behaviour or behaviours unique to that genus.

Human remains from Blombos Cave, South Africa: (1997-1998 excavations)

The Middle Stone Age (MSA) layers at Blombos Cave contain abundant bifacial Still Bay points, formal and ad hoc bone artefacts, and an intentionally incised bone piece. These artefacts add weight to arguments that some aspects of modern human behavior developed earlier in sub-Saharan Africa than elsewhere. Four human teeth were recovered from the MSA strata at Blombos during the 1997-1998 excavations. Two are heavily worn deciduous teeth, and two are incomplete permanent premolar crowns. The Blombos di(1)is comparatively large in relation to modern African homologues, falling within the lower part of the observed Neandertal range. The dm(1)and P(3)are comparable to modern teeth and smaller than most Neandertal crowns. The premolars preserve horizontal circum-cervical striae that suggest palliative toothpick use. The di(1)evinces labial scratches that resemble neither the "cutmarks" that have been observed on Neandertal incisors, nor the striae that have been recorded on modern human teeth.

Radiographic study of the broadbeach aboriginal dentition

This study forms part of a larger anthropological investigation of the Ngaraangbal Aboriginal Tribe's ancestral burial ground at Broadbeach, Australia. It examines the dentition, records the associated pathology in a noninvasive manner, and relates this to the likely subsistence diet of the tribe. The Broadbeach osteological collection was returned for reburial in 1985; however, radiographic and photographic records of 36 adult males were available. These form the basis of our study. The pathology noted in the study sample was compared with a representative sample (n = 38) of pre-European Aboriginal remains from throughout Queensland for verification purposes only. Rates of dental pathology and injury were calculated from the radiographic and photographic records. There was a significant rate of tooth-wear related intra-bony pathology (4.0%), moderate to severe alveolar bone loss, and heavy dental attrition, of which the mandibular posterior teeth were the most severely affected. Caries prevalence (0.8%) was low for hunter-gatherer populations. A large number of molar pulp chambers had a distinctive "cruciate" morphology resulting from the formation of secondary dentine and pulp stones. Injuries and abnormalities included upper central incisor avulsion (58.3%) and taurodontism. These results support the proposal that the Ngaraangbal tribe was a hunter-gatherer population subsisting on an abrasive diet that included marine foods.

Interproximal grooving in the Atapuerca-SH hominid dentitions

The dental sample recovered from the Sima de los Huesos (SH) Middle Pleistocene cave site of the Sierra de Atapuerca (Spain) includes 296 specimens. Interproximal wear grooves have been observed in 20 maxillary and mandibular posterior teeth belonging to at least five of the 32 individuals identified so far in the SH hypodigm. Interproximal grooving affected only the adults, and at an age between 25 and 40 years. The appearance, morphology, and location pattern of the SH wear grooves are similar to those reported in other fossil hominids and in more recent human populations. Two alternative proposals, the toothpicking and the fiber or sinew processing hypotheses, compete for explaining the formation of this anomalous wear. The characteristics observed in the wear grooves of the SH teeth are compatible only with the habitual probing of interdental spaces by means of hard and inflexible objects. Dietary grit may also have contributed to the abrasion of the root walls during the motion of the dental probes.

The earliest Acheulean from Konso-Gardula

Konso-Gardula is a palaeoanthropological area discovered by the 1991 Palaeoanthropological Inventory of Ethiopia in the southern Main Ethiopian Rift. The Konso-Gardula sediments span the period about 1.3-1.9 million years ago. They contain rich Acheulean archaeological occurrences. Vertebrate fossils include early Homo.

On the etiology of interproximal grooves

The recent suggestion by Brown and Molnar (1990) that the common etiology of sinew processing is responsible for the production of interproximal tooth grooves is contested. Based on a review of the Australian evidence and presentation of a previously undescribed dentition from Central Europe, it is argued toothpicks are a likely cause of many artificial grooves in human teeth.