HOW DO DENTAL STUDIES CONTRIBUTE TO THE RECONSTRUCTION OF THE LIVES OF PAST PEOPLES? Kathleen Whitaker Durham University, Durham, UK

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1 EAA Summer School ebook 1: HOW DO DENTAL STUDIES CONTRIBUTE TO THE RECONSTRUCTION OF THE LIVES OF PAST PEOPLES? Kathleen Whitaker Durham University, Durham, UK Introduction Paleopathology, as a sub-discipline of osteology and ultimately archaeology, can provide vital insights into the lives of past peoples. As a field of study, it can add a new dimension to the knowledge we can gain about the past. Together these subjects can enlighten us on the everyday experiences and troubles, and ideally the health and wellbeing of our ancestors. Skeletal remains form the basis of analysis for osteologists and it is through a careful study of skeletons both at the macroscopic and microscopic levels that we can begin to understand the individuals and ultimately the population of a given culture or time. One major difficulty in the study of human remains is preservation. Whether naturally caused through time or through intervention from humans or animals, the damage to the skeleton can cause much heartache and frustration (Spriggs 1989). In an ideal situation the entire skeleton would be available, but more often then not, bones are broken or missed in excavations, or were just not suitable for analysis. Sometimes in these cases the dentition does survive. The material makeup of teeth presents the prospect for better preservation and as a result, provides the opportunity for analysis when it may not have been available otherwise. Enamel is the hardest tissue in the human body and can provide evidence of the stresses an individual was experiencing early in life during its formation. Dentition can also display the results that often occur when teeth are used for purposes other than eating, or when substances possibly not suitable for consumption are eaten. Through dental studies paleopathologist are able to extract an extensive record of the life of an individual, presenting insights into the stresses, diets and occupations which an individual and or population may have dealt with during their lives. Background Principal Dental Diseases or Defects It is important to clarify that all changes to the dentition are not necessarily diseases or defects, but regardless of their origin, paleopathologists can use these alterations to help to learn about the individual. Dental diseases are divided into the categories of infectious, degenerative, developmental and genetic; however there is a considerable amount of overlap and to a certain degree there is also disagreement on the exact aetiology of certain changes, such as dental caries (Lukacs 1989). Those discussed below will not be identified as belonging to a certain subtype but rather their diagnostic and analytical features will be examined to provide a background for later discussions. Enamel Defects There are several conditions that fall under this category including linear enamel hypoplasia (LEH), gross enamel defects and deciduous enamel defects. Overall it is the enamel that is affected by a variety of non-specific stressors. Generally these conditions can be described as a deficiency in enamel thickness due to disruption of ameloblast (enamel forming) activity (Goodman et al 1980 in Lukacs, 1989: 267). There are several ways to diagnose this condition, including macroscopically, by looking for irregular horizontal lines or pits on the labial surfaces of the crown of the teeth, and microscopically by looking for Wilson bands which resemble a striae of Retzius that exhibit a linear arrangement of abnormal or absent prism structure (Rose et al, 1985: 287). These defects can occur on all the teeth (generally implying genetic factors) or on a majority of teeth, suggesting a possible metabolic origin (Fig. 1). Typically these defects can be scored for location, appearance and severity. The limitations of these techniques for this and all defects/diseases will be discussed later. Dental Wear Dental wear can be divided into three general categories including attrition, abrasion and erosion. Attrition is due to tooth on tooth contact and can result in the wearing down of tooth enamel, possibly exposing the dentine and pulp chamber. Abrasion can produce the same effects with the general loss of surface detail due to abrasive particles such as unprocessed or poorly processed foods which damage the surfaces with mastication (Powell 1985:309). Erosion of tooth enamel occurs most often when acidic substances are ingested or built up within the mouth. 27

2 Figure 1: Example of maxillary linear enamel hypoplasia (Lukacs 1989: 268). Dental attrition can be scored at the macroscopic level using Brothwell s method (1981) by recording the amount of dentine exposure on all the teeth. This method also highlights abnormal wear such as angled crowns, and differences between left and right or mandible and maxilla dentition. Differences in the three conditions are best analysed at the microscopic level to pick up the minute distinctions among them. Dental microwear can best be studied using a scanning electron microscope (SEM) that picks up the subtle differences that conventional light microscopes can miss (Teaford, 1991). The wear is characterized by regular patterns in set locations on the tooth, so it becomes possible to tell the difference between molar shearing facets and molar crushing and or grinding facets which can have implications when discussing types and causes of wear (Teaford, 1991: ). Dental Calculus Calculus is the mineralization of bacterial plaque resulting from, among other things, a high protein diet (Lukacs 1989:267). This mineralization can result in a variety of manifestations including pits, fissures, grey or brown thick plaque on the supragingival surface or thinner green or black plaque on the subgingival surface (Fig. 2), (Greene et al 2005: 122). The teeth most often affected include the upper molars on the buccal surface and lower incisors on the lingual surface. There are several ways to analyse and record dental calculus. Those proposed by Brothwell (1981) and Dobney and Brothwell (1986) focus on the severity and/or extent of the calculus on individual teeth. It is also vital to record the tooth or teeth affected; the sites on the individual teeth and the amount of cover. Calculus indices have also become another method for analysing rates and prevalence of calculus between and among populations (Greene et al, 2005). The advantage of this type of method is that it provides a multidisciplinary approach of combining solid paleopathological methods (Buikstra and Ubelaker 1994) with modern clinical methods (ten Cate 1988) to arrive at a more dynamic result that can be used for future studies and comparisons. Dental Diseases and Defects Through Time In modern times there are a variety of dental diseases that continue to affect the dentition. There are also however a number of factors that influence the defects both today and in the past, including diet, economy, environment, social status, oral hygiene and lifestyle. Al of these variables dictate the quality of the food one is consuming and the access to dentists to combat any defects that may arise. Foods that tend to be high in sugars whether natural or artificial, can have serious erosive affects on the dentition as well as promoting carious lesions throughout the mouth. Diets high in protein are also susceptible to higher amounts of calculus and can lead to more complicated conditions such as periodontal disease, which is much more prevalent today than in the past (Lavigne and Molto, 1995). Today, in many areas of the world, including North America, fluoride is present in the water system. This helps to strengthen the dentine and enamel and can assist in the prevention of carious lesions and degree of wear. Oral hygiene is an extremely important issue, one that most populations in the modern world are aware of, but which many individuals do not practice. Methods such as flossing appear to be relatively straight forward and yet often children and adults do not take this step. 28

3 This failure causes an increase in completely preventable dental caries. Today with all of our knowledge, it is interesting to look at the prevalence of dental caries, calculus and wear, which are relatively high, and compare them to those of the past, when populations may not have had the luxury of modern dental knowledge and technology. Overall there are a number of factors, as discussed above which induce or predispose an individual to dental disease and defects, and it is important to remember these if we are to study, analyse and interpret dentitions of the past in order to get a better understanding of historic lives. Figure 2: An example of maxillary dental calculus (Lukacs 1989: 270). Non-Specific Stress Non-specific stress indicators are present throughout the osteological record (Mays 1985; Wapler 2004). Within bone these episodes can manifest as Harris lines, cribra orbitalia and porotic hyperostosis. In the dentition, linear enamel hypoplasia (LEH) and other enamel defects are commonly attributed to specific episodes of enamel growth disruption in an individual s life. Enamel does not remodel as bone does and as such the teeth can provide a more permanent record of developmental disruption during infancy and childhood than skeletal indicators (King et al, 2005:548). Many different causes have been attributed to dental enamel defects including nutritional quality, neonatal disturbances, systemic diseases and infectious disease (Duray 1996). Many, including Duray (1996) and King and colleagues (2005), have attempted to show correlations between dental enamel defects, such as LEH, and reduced age at death. Duray sampled a Late Woodland population from Ohio and found in a sample of 143 individuals that those with defects had a lower mean age at death of 5.37 years compared to their counterparts with normal teeth (Duray, 1996: 278). Although males were also affected, females with defects died on average seven years earlier than females with no defects. Overall his findings suggest that those individual with enamel defects suffered considerable damage to their immune system during their pre and post natal development, leading to less resistance and ability to combat stresses in their lives (Duray, 1996: 284). King and co-workers (2005) decided to focus their work on the known age at death populations of Spitalfields and St.Bride s Church in London. Of the 34 individuals surveyed, all were recorded with enamel defects, with a range of two to nineteen separate episodes of stress-related disturbances. They also analysed the ages that these disruptions would have taken place and found that for Spitalfields the highest frequency took place during the two to three year age range, while for St. Bride s it was between three and four years of age (King et al, 2005: 552). Again it was also found that females had higher frequencies and greater proportions of disrupted enamel growth than the males. There can be two possible conclusions drawn from these types of studies, one is that the individuals are members of the surviving population and the defects can be viewed as evidence that they were able to successfully deal with the trauma in their lives. (This should then also correlate with levels of child mortality that would provide evidence of those that could not survive the disturbances.) The other conclusion could be that the females of the populations may have been treated differently than the males, however, to what degree and by what means are still questionable. 29

4 Dietary Reconstruction Diet is an important aspect of past people s lives as it can have a wide ranging effect on the health and well-being of individuals and populations. In bone there are a number of ways to detect diet including evidence of metabolic diseases and stable isotope analysis to uncover food groups (Katzenberg 2000). The dentition can also supply information, but in slightly different ways. Dental wear analysis presents information on differing food processing techniques which can give insight into the technology and culture of a given population. A study was undertaken by Teaford (1991) to see if dietary changes could be found on the teeth of Native Americans prior to and after contact with Europeans. The shift from hunter-gatherer to sedentary agriculturalists is well documented in sites along the Georgia-Florida coast. In the analysis of 27 maxillary first molars, pre-contact dentitions displayed increased enamel pitting, and larger scratch widths suggesting these people were ingesting hard, abrasive objects on a regular basis (Teaford, 1991:349). The early and later contact dentitions however displayed far less wear and that was attributed to the softer diet associated with sedentary populations. This type of result was beneficial in reinforcing previous beliefs about the lives of a given population with entirely independent techniques, but it is also useful when no other supplementary information is available. Dental calculus provides a unique method by which to gain knowledge about past dietary patterns by analysing the microscopic contents of the plaque; it is a direct association of diet that is rarely available in the archaeological record (Dobney and Brothwell, 1986: 58). It is possible, under appropriate conditions, to find minute traces of plant and other food particles that became lodged in a person s dentition. Dobney and Brothwell (1986) studied a number of different individuals and animals from different time periods to look at the calculus for evidence of food debris. A piece of supragingival calculus was recovered from a prehistoric Irish skeleton from Dalkey Island. They managed to find an abundance of fragments including tiny pieces of cereal shaft (including barley), pollen grains and a large quantity of wheat (Dobney and Brothwell, 1986: 69-74). There was even evidence of an organism that is only found in crayfish, suggesting that it played a role in the diet of this prehistoric Irish man (Table 1). This type of specific information is almost impossible to obtain directly in an archaeological context but it can provide valuable information about the diet and therefore even the technology and economy of a population in terms of how and where they may have procured their food. Combined with other dentition studies and osteological analysis, the diets of the past can become quite clear and can shed light on the health and well being of individuals and populations. Table 1: Chart illustrating organisms discovered in dental calculus (Dobney and Brothwell: 1986: 72). Occupation Reconstruction Occupation reconstruction is one area within paleopathology in which there is little agreement. Some authors believe muscoskeletal stress markers suggest occupations such as hunters and fighters, while others believe some non-metric traits such as squatting facets suggest grain grinders (Kennedy 1989; Boulle, 2001). 30

5 Beyond bone, the dentition may be able to supplement this field that is otherwise lacking in standards of proof. Brown and Molnar (1990) studied the early nineteenth century skeletal collection of the Narrinyeri of South Australia. Eighty-five crania were inspected for changes in the dentition and they found that thirty-five or forty-one percent had one or more grooved teeth (Brown and Molnar, 1990:547). The majority of grooves in both the maxillary and mandibular dentition were located within the group of the second premolar and first and second molar (Fig. 3). Interproximal grooving was described on the dentition and attributed to the task activity of stripping fibrous sinews between the teeth. The authors were in a unique position in that there is documentary evidence in the form of film that shows the stripping of sinew in the posterior teeth of another tribe of Australian aborigines (Fig. 4). The task would have been crucial to society and the authors believe the dentitions illustrate this important occupation (Brown and Molnar, 1990:551). Turner and Anderson (2003) also set out to use the dentition to show possible evidence of occupation when they looked at seventy adult dentitions from medieval Kent. They found one case of marked dental abrasion in a year old male (Turner and Anderson, 2003:168). They noted severe changes in the anterior teeth, both on the mandible and maxilla (Fig. 5). Although at first it was suggested that the dentition and its related attrition mimicked someone who habitually smoked clay pipes, when medieval nails were tested with the dentition it was found they fit perfectly (Fig. 6; Turner and Anderson, 2003:170). The authors believe the man may have been a carpenter which explains the deformities and location on the dentition as belonging to someone who would habitually hold nails in his teeth while working. Figure 3: Deep interproximal grooving (Brown and Molnar 1990: 548). Figure 4: Aboriginal craftsmen stripping kangaroo sinew (Brown and Molar 1990: 550). 31

6 Figure 5: Palatal view of the maxillary dentition, Turner and Anderson, 2003: 171. Figure 6: Palatal view of the maxillary dentition with nails, Turner and Anderson, 2003:171. Limitations In the study and analysis of the dentition there are a number of pitfalls and limitations at each step. One of the most basic is the issue of recording. Many if not most of the methods employed to record the presence / absence or severity of dental defects are very subjective and as such there is a high chance of interobserver error (Brothwell, 1981; Hillson 1986, 1996). This complicates matters further when there are attempts at cross cultural or population comparisons when different methods may have been employed. The lack of standardization is also a concern in terms of measuring severity. This can be applied to everything from dental caries to dental wear and amount of calculus and it is important to remember these issues when reading reports and conducting work. Along these same lines are also concerns with reporting various prevalence rates. Often authors may not specify what the rates are based on, whether it is percentage of total teeth present, percentage of a specific type of tooth or even percentage of recovered skeletons. These are important points that can greatly alter any results and influence future work. Another important set of limitations is the discussion of causes of dental pathologies. As discussed above, there are often a multitude of explanations for a given dental disease, much the same as in the skeleton, and as a result it is frequently difficult to make inferences about individuals and even more so about populations. Part of this problem is also caused by focusing on just one skeletal element. Despite the knowledge that can be gained by looking at the dentition, it is absolutely prudent that as much of the skeleton as possible is examined for evidence to support, add to or provide alternatives to previous conclusions. Finally, as mentioned above, the addition of supplementary information, in whatever form, can always benefit any study which is why a multidisciplinary approach is the best method by which to conduct work and arrive at suggestions for future studies. 32

7 Conclusions The study of the dentition in archaeological contexts can provide clues and information about an individual that may not be available otherwise. Because of their material nature, teeth are far more resistant than bones to stresses and once formed can display the effects of diet, occupation and culture that may not be obvious elsewhere on the skeleton. It must be remembered though, that just like the skeleton, there is a possibility of error involved in recording and diagnosis so one must be cautious when making assumptions. Ideally the dentition complements the study of the skeleton and should be seen as a valuable source of evidence in conjunction with the rest of the body. References Boulle, E-L Evolution of two human skeletal markers of the squatting position: A diachronic study from antiquity to the modern age. Amer. J. Phys. Anthrop. 115: Brickley, M The diagnosis of metabolic disease in archaeological bone. In M. Cox and S. Mays (eds): Human osteology in archaeology and forensic science. London, GMM, pp Brothwell, D.R Digging up bones. London, British Museum (Natural History) Brown, T. and Molnar, S Interproximal grooving and task activity in Australia. Amer. J. Phys. Anth.. 81: Buikstra, J.E., Ubelaker, D.H Standards for data collection from human skeletal remains, In: Davis, H.A. (ed.), Arkansas Archaeological Survey Research Series, Arkansas Archaeological Survey. Fayetteville, Arkansas. Dobney, K. and Brothwell, D Dental calculus: its relevance to ancient diet and oral ecology. In R. Foley and E. Cruwys (eds), Dental Anthropology. British Archaeological Reports 291. Oxford, Tempus Reparatum, Duray, S.M Dental indicators of stress and reduced age at death in prehistoric Native Americans. Amer. J. Phys. Anthrop. 99: Greene, T.R., Kuba, C.L., and Irish, J.D Quantifying calculus: A suggested new approach for recording an important indicator of diet and dental health. Homo 56: Hillson, S Teeth. Cambridge University Press Hillson, S Dental anthropology. Cambridge, University Press Katzenberg, M.A Stable isotope analysis: a tool for studying Katzenberg and S.R. Saunders (eds): Biological anthropology of the human skeleton. New York, Wiley-Liss, past diet, demography and life history. In M.A. Kennedy, K.A.R Skeletal markers of occupational stress. In M.Y. Iscan and K.A.R. Kennedy (eds) Reconstruction of life from the skeleton. New York, Wiley-Liss, King, T., Humphrey, L.T., Hillson, S Linear enamel hypoplasias as indicators of systemic physiological stress: Evidence from two known age-at-death and sex populations from postmedieval London. Am. J. Phys. Anthrop. (published online) Lavigne, S.E. and Molto, J.E System of measurement of the severity of periodontal disease in past populations. Int. J. Osteoarchaeology 5: Lukacs, J.R Dental palaeopathology: methods for reconstructing dietary patterns. In M.Y. İşcan and K. Kennedy (eds): Reconstruction of life from the skeleton. New York, Alan Liss, Mays, S.A Relationship between Harris line formation and bone growth and development. J. Arch. Sci. 12: Powell, M.L Analysis of dental wear and caries for dietary reconstruction. In R.I. Gilbert and J.H. Mielke (eds) Analysis of prehistoric diets. London, Academic Press, Rose, J.C., Condon, K.W. and Goodman, A.H Diet and dentition: developmental disturbances. In R.I. Gilbert and J.H. Mielke (eds) Analysis of prehistoric diets. London, Academic Press, Spriggs, J On and off-site conservation of bone. In C. Roberts, F. Lee, J. Bintliff (eds): Burial Archaeology. Current research, methods and developments. Brit. Archaeol. Rep. Brit. Ser Oxford, Tempus Reparatum, pp Teaford, M Dental microwear. What can it tell us about diet and function. In M. Kelley and C. Larsen (eds): Advances in Dental Anthropology. Chichester, Wiley-Liss Inc., ten Cate, J.M Research on dental calculus: why? In ten Cate, J.M. (ed) Recent advances in the study of dental calculus. IRL Press, Oxford University Press, Oxford: 1-4. Turner, G. and Anderson, T Marked occupational dental abrasion from Medieval Kent. Int. J. Osteoarchaeol. 13: Wapler, U., Crubezy, E. and Schultz, M Is cribra orbitalia synonymous with anemia? Analysis and interpretation of cranial pathology in Sudan. Amer. J. Phys. Anthrop. 123: Mailing address: Kathleen Whitaker Durham University, Old Elvet, DH1 3HP Durham, UK katieswwhitaker@yahoo.ca 33