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Interview with Liz Eastlake: Dental Delights and Estonian Escapades

13 Dec

Liz Eastlake is an osteoarchaeologist from Yorkshire and a graduate of the MSc in Human Osteology and Funerary Archaeology from the University of Sheffield.  With a strong background in fieldwork Liz also regularly engages in public outreach and education on the topics of archaeology practice and human osteology, both in museums and in colleges around Yorkshire.  Her research interests lie in dental bioarchaeology and understanding the implications for markers of occupation in the human skeleton.  In her free time Liz can often be found at the York branch of Dr Sketchy’s anti-art art school.


These Bones of Mine: Hello Liz and thank you very much for joining me here at These Bones of Mine. For those that do not have the pleasure of knowing you, please could you introduce yourself and tell us a little bit about your background?

Liz:  Hi David, thanks for having me.  I am a graduate of the MSc in Human Osteology and Funerary Archaeology program from the University of Sheffield and I am currently working for York Archaeological Trust at their archaeology museum DIG.  I also do the occasional spot of digging and skeleton box organisation with the Trust on a volunteer basis.  Further to this I teach human osteology workshops with the Workers’ Educational Association as part of their Digability Project.  To top it all off I also work providing disability support at the local university a few days a week!  Needless to say I have very little free time and run mostly on caffeine.

TBOM: That certainly sounds like you are getting a full experience of living the archaeological life! What sparked the interest in studying human osteology and funerary archaeology, and what was the experience learning about skeletal anatomy like?

Liz:  I went on a rescue excavation in the grave yard of my village (Sheriff Hutton) church when I was 15 years old.  The church itself supposedly contains the remains of Richard III’s son, although I never really considered how blessed I was growing up in such a historic environment until much later, especially with recent events.  It was the discovery of the different elements of commingled human remains we were uncovering that fascinated me the most.

A number of skulls from the site still had small amounts of hair surviving due to the environment created by contact with copper shroud pins.  It really stuck with me that something so fragile could survive for so long beneath our feet.  Skeletal anatomy itself is a fascinating subject.  Most people are completely unaware of what goes on within their own bodies and so this aspect of archaeological study is pretty relevant and interesting to everyone.

TBOM: The rescue excavation must have been an informative introduction to the human skeleton in an archaeological context, especially considering the level of preservation present.  Your current job with York Archaeological Trust involves helping to present archaeology to the public, how have you found this and has it made you change the way you think about archaeology itself?

Liz:  Working with children in general is pretty hilarious, I love the way the mind works without any of the barriers that adults would normally put up.  In the context of archaeology a kid can really make you think about things in a different way with the answers they come up with, which is great as it is all so open to interpretation.  Often, I meet kids who are so excited to tell me all about what they have found in their own back garden or can’t wait to go home and dig up their parents flower beds after a visit (sorry parents!).  It’s so important to be inquisitive and that transfers to other aspects of life, including the process of growing up.

LIZDIG

‘I think it may be a bit late to help this person’. The chance to draw a in-situ skeleton is one of the many interactive exhibitions on offer at the DIG museum of archaeology in York. Image credit: Liz Eastlake.

What’s also great is that parents or grandparents come along thinking perhaps its a couple of hours to kill with the kids on a weekend or during the holidays, and they end up enjoying it more than the children do!  Few people realise they have an interest in something until you present the information and let it grow from there.  Archaeology is all about people – everyone has an interest in how we got to where we are today.  Most people I meet are at least amateur archaeologists in some way!

For me personally the job has given me a broader knowledge of archaeological periods, which is always beneficial when looking at specific burials.  Human osteology can be such a narrow field of study, for example when I look at teeth, which is such a tiny area, you even begin to ignore the rest of that same skeleton because there is so much to focus on when studying teeth alone.  Context is everything.  Before starting with the York Archaeological Trust I knew embarrassingly little about the archaeology of York itself.  It is easy to take things you have seen so often for granted, especially when you grow up with all this old stuff around you as you think nothing of it.  I definitely appreciate York more now than I ever have before and have the best time doing what I do.

TBOM: That is fascinating to hear about how interested children and adults become when presented with what archaeology actually is and how their experiences differ.  As previously mentioned you’ve also been working with the Workers’ Educational Association in South Yorkshire, helping to lead and present classes on human skeletal anatomy.  How have you found the audience’s reaction and participation in such activities?   

Liz:  The reactions are quite mixed.  Most participants are fascinated with how the body works.  Physical demonstrations of how bony articulations work and comparing them to the movements they can make in their own bodies helps bridge the gap between us and pile of bones.  It can be hard to think of a skeleton as a once living, fully fleshed person like ourselves.

A few participants have felt uneasy about the bones, despite the knowledge that the skeleton I bring is just an accurate plastic copy.  I think this mostly comes from the portrayal of bones and death in the media.  I saw a really interesting talk by Campbell Price at Manchester Museum a while ago that talked about how skeletons and mummies especially are portrayed alongside werewolves and vampires and it is not surprising that people, especially children (but not always), ask ‘is it real?’ when faced with a preserved Egyptian mummy in a museum.  A feeling of unease might also come from a fear of death itself and the uncertainty it brings.  This is a completely understandable feeling but I think it is important to try to break this fear down in an educational setting and challenge misconceptions about what happens to our bodies after we die.

TBOM: As well as helping to de-mystify the human skeleton for the public, you’ve also presented your MSc dissertation research on the study of the dentition of two 18th and 19th century populations from northern England at a recent Elmet Archaeology talk.  What was your research about and how did you come to focus on teeth specifically?

Liz:  I seem to have focused on teeth since I first became interested in human osteology.  I find them fascinating because they look pretty much the same in death as they do in life.  There is such a wealth of information you can gain about people’s lives in the past by studying dentition.  I have focused on what they can tell me about the general health of the population I’m studying and also whether they can give an indication of individual occupation.  At some point everyone has grasped something between their teeth, like house keys for example, when your hands are full.  Repeated use of the teeth as a third hand can leave tell-tale marks on the tooth surface, for example basketry weaving or even sewing; snapping a thread between the incisors.

My dissertation topic focused on identifying occupation from the teeth of two Victorian era cemetery populations, one of high status individuals from the St Bride’s assemblage in London and the other of low status people from Coronation Street assemblage in South Shields, northern England.  Social status for these two sites was known from written records, but the difference was also apparent from the teeth.  A number of individuals from the high status group had solid gold dentures and fillings, as well as other evidence for dental intervention and aid.  Those from the low status site had no clear evidence for dental work by a professional and would have likely extracted a troublesome tooth themselves or had a similarly untrained acquaintance do it for them.  These individuals also had some quite extreme dental wear patterns indicative of use of the teeth for grasping and pulling materials within their mouths. Unlike the high status site which had only one example of an older adult female with grooved patterns of wear in her anterior dentition, perhaps from snapping threads whilst sewing.

To most people it can be quite unsettling to envisage the pain a large abscess or gross caries would have caused a living person hundreds of years ago.  However, the information that can be gained through the study of teeth is so extensive and informative about past populations, that it is a fascinating area of osteological analysis, which I hope to pick up again by completing a PhD in the future.

TBOM:  That sounds like a fascinating comparative study on Victorian populations.  So as well educating the public on the value of archaeology and human osteology and as well as conducting original research, you have also recently been excavating an Iron Age site in Estonia.  How did that come about and what were your experiences there like?

Liz:  A friend of mine from my masters course at Sheffield, Anu Kivirüüt, invited me along to the excavation she was running with her department at the University of Tartu.  It was a fantastic couple of weeks of perfect hot weather and digging in the shade.  I particularly enjoyed the excavation methods employed in Estonia which are so different to the strict regulations in the U, although I discuss this more at Anu’s site here.

The excavation was on the Aakre Kivivare tarand-grave site, which are Iron Age in date.  This type of grave sites are communal burial places with rectangular above-ground stone wall enclosures, which are often labelled and described as  tarands-graves.  When these graves first appeared on the landscape in the Pre-Roman Iron Age (around 500 BC – AD 50), they contained only inhumation burials and one rectangular enclosure was assigned for one body.  However, over time, cremation became a more frequently recorded way of disposing of the dead and the subsequent cremated bones and most of the artefacts were scattered in the tarand-area, mostly inside but also outside of the walls (see more information here on this ongoing project).

The entire site was recorded using digital photography, in a technique called photogrammetry, and converted into a 3D model after each layer of soil and stones was removed.  This was a great time-saving method and the 3D model really helped visualize the site layers.  Unfortunately, very little bone, cremated or otherwise was recovered from the site.  However, there were numerous beautifully preserved brooches of different typologies, a selection of which can be viewed here.

As well as a fantastic excavation there was also opportunities to explore other nearby archaeological and cultural sites, taste the great food, swim in the lakes and enjoy a sauna (including being whipped with birch bark – it is good for you!)

TBOM:  Swimming in the lake sounds quite beautiful, but if I ever head to Estonia I think I’ll avoid the birch whipping!  The use of technology to quickly record the site at Aakre Kivivare certainly sounds innovative and extremely useful, please do let me know how the excavations and research turn out.  In conclusion, though, it is clear you have managed to gain a lot of experience in the various aspects that archaeological life has to offer.  Do you have any advice to the next crop of archaeologists and, finally, what are your plans for the future?

Liz:  I would say volunteer, volunteer, volunteer!  Getting involved with excavations as well as post-ex stuff before starting at University, during your course and over summer holidays shows you are keen and can make you lots of useful connections for the future.  Then when you are qualified, especially in a specialised area of the profession, try to never work for free again (chuckle)!

20140430_140842

One happy skeleton. Drawing bones in-situ at YAT’s DIG museum helps children (and adults) understand the importance of context in archaeology. Image Credit: Liz Eastlake.

I would love to do a PhD in some aspect of dental anthropology at some point in the future, as well as getting more experience in the commercial side of archaeology.  I think it is important to see things from start to finish where possible, as context is everything and it can be easy to detach a single skeleton from its surroundings and consider it individually.  However, this does not benefit our view of the past.  Working in the field will also mean a chance to experience all aspects of archaeology and not just bones.

But before I get PhD crazed I am going travelling around the world, admiring old things and rock climbing (but mostly trying not to be an obnoxious cliche for the benefit of people who follow me on social media!).

TBOM: Thanks for the advice Liz and I hope you enjoy your travels!  

Further Information

  • Head to York Archaeological Trust’s portal to learn more about their museums and archaeological here.  If you are an interested member of the public, an archaeological student or simply want to learn about archaeological artefacts YAT always welcome volunteers.
  • Learn more about Elmet Archaeology’s upcoming lectures and annual Dearne Valley Archaeology Day here.  Elmet participate in both commercial and community archaeological projects and are always active in education outreach.  Check out some of their courses for 2015 here.
  • The Workers’ Education Association’s are always actively promoting education outreach in a variety of locations and involving a wide range of subjects.  As a part of the ongoing Show Us Your Research! project by the universities of Coimbra and Algrave, Portugal,  Beauchamp and Thorpe (2014) have produced an assessment of WEA’s ongoing inclusive archaeology education project.  Read the PDF summing up their research on the benefits and outcomes so far of the inclusive archaeology project for free here.
  • Head over to the Aakre Kivivare blog site to learn more about the fascinating finds from this Estonian Iron Age site (site can be translated).  Liz has also produced a post on her experiences from the 2014 summer excavations which can be read here.

Skeletal Series Part 12: Human Teeth

28 Oct
teeeeeethhh

Basic human permanent dentition. Click to enlarge.  Image credit: modified from here.

Teeth, as a part of the dentition, are a wonder of the natural world and come in a variety of forms and designs in vertebrate animals, with perhaps some of the most impressive examples include the tusks of elephants and walruses.  They are also the only part of the human skeletal system that can be observed naturally and the only part that interact directly with their environment via mastication (White & Folkens 2005: 127).

Although primarily used to break down foodstuffs during mastication, teeth can also be used as tools for a variety of extramasticatory functions such as the processing of animal skins and cord production (Larsen 1997: 262).  As the hardest of the biological material found in the body teeth survive particularly well in both the archaeological and fossil records, often surviving where bones do not.  Teeth are a goldmine of information for the human osteologist and forensic anthropologist alike as they can be indicative of the sex, age, diet and geographic origin of the individual that they belong to (Koff 2004, Larsen 1997, Lewis 2009, White & Folkens 2005).

This entry will introduce the basic anatomy of the human dental arcade, deciduous and permanent dentition and the various tooth classes, alongside a quick discussion of the action of mastication itself.  But first, as always in this series, we’ll take a look at how teeth can be found during the excavation of archaeological sites.  This post marks the final Skeletal Series post to deal explicitly with individual elements of the human skeletal system.  The next few posts in the Skeletal Series will be aimed at detailing the methods used in aging and sexing elements in the adult and non-adult skeleton (and the success rates of the various methods), followed by posts introducing the pathological conditions that can be present on human skeletal remains.

Excavation

The 32 permanent human teeth, located in the upper arcade (maxilla) and lower arcade (mandible) of the jaws, each holding 16 teeth, are resilient to chemical and physical degradation.  Furthermore tooth crown morphology (the surface that consists of enamel) can only be changed by attrition (tooth wear), breakage, or demineralization once the crown of a tooth has erupted through the gum line (White & Folkens 2005: 127).  As such teeth are often found at locations where human remains are suspected to be buried or otherwise excavated.  Care must be taken around the fragile bones of the spanchnocranium (i.e. the facial area of the skull), defined as necessary, and, if needed due to fragility, the area may have to be lifted with natural material still adhered to the bone to be more carefully micro-excavated in the lab (Brothwell 1981: 3).

Circled in red, the teeth are located in the upper (maxilla) and lower (mandible) jaws. This individual, dating to the medieval period in eastern Germany, highlights a common occurrence in supine burials where the mandible often ‘falls’ forward as the muscles, ligaments and tendons decompose. Always be careful when excavating suspected burial features as both bone and tooth can be chipped by trowels or other metallic excavation implements. Photograph taken by author.

Loose dentition may be found around the skull itself as teeth can be loosened naturally postmortem as natural ligaments decompose.  Sieving around the location of the skull may prove useful in finding loose teeth and also the smaller bones of the skulls (such as the ear ossicles).  In the excavation of non-adult remains, or of suspected females with fetal remains in-situ, great care should be taken in recording and the excavating of the skull, torso and pelvis.  As mentioned below teeth form from the crown down, as such deciduous or permanent teeth during growth may be loose in exposed crypts in the mandible or maxilla (Brickley & McKinley 2004).  Furthermore due to the small size and colour of the 20 deciduous teeth, especially the crowns during the formation and growth of the teeth, may be mistaken for pieces of dirt or rocks.

Tooth Anatomy & Terminology

The basic anatomy of teeth can be found in the diagram below, but it is worth listing the anatomical features of a typical tooth here.  The chewing surface of the tooth is called the occlusal surface and it is here that the crown of the tooth can be found.  The crown of a tooth is made of enamel, an extremely hard and brittle mixture of minerals (around 95-96% hydroxyapatite).  The enamel is formed in the gum and once fully formed contains little organic material.  The demineralization of teeth can repair initial damage, however this is limited in nature.  Dentin (sometimes termed dentine) is the tissue that forms the core of the tooth itself.  It is supported by a vascular system in the pulp of the tooth.  Dentin can only repair itself on the inner surface (the walls of the pulp cavity), but dentin is a softer material than enamel and once exposed by occlusal wear it erodes faster than enamel.  The pulp chamber, in the centre of the diagram below, is the largest part of the pulp cavity at the crown end of the tooth.  The pulp itself is the soft tissue inside the pulp chamber, which includes the usual trio bundle of vein, artery and nerves (V.A.N.).  The root of the tooth is the part that anchors it into the dental alveolus tissue (sockets) of the jaw (either the maxilla or mandible).

Toothanatomy2

The basic anatomy of a tooth (in this case a molar), outlining the three main layers present in all human teeth. Image credit: Kidport.

Cementum is the bone type tissue that covers the external surface of the roots of teeth.  The apex, or apical foramen, is the opening at the end of each root, which allows for the nerve fibers and vessels up the root canal into the pulp chamber.  Heading back up to the occlusal surface of the tooth we encounter cusps of the crown, each of which have different individual names depending on their position.  Upper teeth end with the prefix -cone whereas lower teeth end with the prefix -conid (see details here).  Finally we have fissures, which are clefts between the occlusal surfaces between cusps.  Fissures help divide the cusps into patterns and are helpful to know to help identity individual teeth (specifically the molars).  Above information taken from White & Folkens (2005: 130-131).

As previously highlighted there are some directional terms that are specific to the dentition, but it is pertinent to repeat some of the key aspects here for clarification as tooth orientation is important –

Apical: towards the root.
Buccal: towards the cheek (the buccinator muscle- the terminator of the muscle world!), used in realtion to posterior teeth (premolars and molars) only.
Cervical: towards the base of the crown or neck of the tooth (often called the cementoenamel junction).
Distal (direction): away from the midline of the mouth, opposite of mesial.
Incisal: towards the cutting edge of the anterior teeth.
Interproximal: between adjacent teeth, also useful to know and be able to identify are interproximal contact facets (IPCFs) which can indicate anatomical location of  tooth.
Labial: surface towards the lips, anterior teeth (canines and incisors) only.
Lingual: of the tooth crown towards the tongue.
Mesial (direction): towards the midline, closest to the point where the central incisors contact each other.
Occlusal: towards the chewing surface (crown) of the tooth.

teethdirect

Tooth anatomical direction terminology and legend of tooth position, above is the maxillary dental arcade. Typically the uppercase and lowercase numbers refer to maxilla and mandible positions respectively, and often include a L or R for left or right hand side for quadrant location. In deciduous dentition lower case letters are used, in permanent dentition capitalization is used. Premolars are often 3rd (1st premolar) and 4th (2nd premolar) after palaeontological standards. Check out Brickley & McKinley (2004) below for BABAO recording standards. Image credit: Dr Lorraine Heidecker @ Redwoods.edu.

Above information taken from White & Folkens (2005: 128) and here.

A different method for recording the presence/absence and state of the individual teeth from archaeological skeletal populations is proposed by the British Association of Biological Anthropology and Osteoarchaeology (BABAO) as mentioned above.  In this method, proposed by Connell (2004: 8) the deciduous and permanent dentition are given a separate letter or number:

toothrecording

The BABAO 2004 guidelines for compiling a dental inventory for a skeleton. It should be noted that if compiling a large inventory for a population it is best to individually number and identify each tooth after the Buikstra & Ubelaker 1994 standards (but see also Bone Broke). Click to enlarge. Image credit: Connell (2004: 8).

Deciduous & Permanent Teeth

Humans have only two sets of teeth during their lifetimes.  The first set, known as the deciduous (primary or milk) teeth, are the first to form, erupt and function during the early years of life (White & Folkens 2005: 128).  The primary dentition consists of central incisor, lateral incisor, canine, first molar and second molar in each jaw quadrant, making a total of 20 individual deciduous teeth in all.

These are systematically lost and replaced by the permanent, or secondary, dentition throughout childhood, adolescence and early adulthood.  As noted above these include a central incisor, lateral incisor, canine, two premolars, and three molars in each jaw quadrant making a total of 32 individual permanent teeth in all.

The sequencing of the pattern of tooth eruption plays a vital clue in estimating the age of the individual, whilst tooth attrition (wear) is used in estimating individual age after the permanent dentition have fully erupted (White & Folkens 2005: 346).  The loss of a tooth, or teeth, antemortem (before death) can lead to alveolar resorption over the empty tooth socket.  Individuals who have no teeth left (often elderly individuals or individuals suffering periodontal disease) are termed edentulous.  This can lead to problems pronouncing words, the cheeks sagging inwards and problems chewing or grinding food (Mays 1999).  Perhaps the most famous example of this is one of the Dmanisi hominin fossils (crania D3444 and associated mandible D3900) whose crania lacked any teeth whatsoever and showed alveolar bone resorption of both the mandibular and maxillary arches.  However it is unknown if this is evidence of conspecific care, or just of survival, is not known (Hawks 2005).

teeth decid

The human deciduous dentition, notice the absence of any premolars and lack of third molar. The total number of deciduous teeth is 20. Not to scale. Image credit: identalhub.

Deciduous tooth formation begins only 14-16 weeks after conception.  White & Folkens (2005: 364) note that there are four distinct periods of emergence of the human dentition: 1) most deciduous teeth emerge and erupt during the 2nd/3rd year of life, 2) the two permanent incisors and first permanent molar usually emerge around 6-8 years old, 3) most permanent canines, premolars, and second molars emerges between 10-12 years old and finally 4) the 3rd molar emerges around 17/18 years old – although this can vary.  Note also that there are some differences between the sexes and between populations (Larsen 1997, Lewis 2009, Mays 1999).  Trauma, pathological conditions and diseases can also influence tooth development and eruption rates, often delaying the eruption of the permanent dentition and sometimes leaving visible deformities in the teeth themselves, such as linear enamel hypoplasia (sign of stress) or mulberry molars (specific sign of disease) (Lewis 2009: 41).

teeth perman

The human permanent dentition highlighting the 32 individual present. Notice the crown shape and sizes indicating different functions. Not to scale. Image credit: identalhub.

The basic differences between the deciduous and permanent dentition are as follows:

Deciduous…………………….Permanent

1. No premolars.                          2 premolars.

2. Smaller teeth, each              Larger teeth apart from premolars
tooth is smaller than                    which replace deciduous molars.
successor.

3. Cusps pointed &                  Cusps are blunt, crowns not bulbous,
crowns bulbous.                            contact areas broader.

4. Enamel less translucent, Enamel is more translucent, blueish white.
teeth appear whiter.

5. Enamel ends abruptly at    Enamel ends gradually,
the neck.                                             1st molars have no bulge at cervical margin.

6. Occlusally the Bucco-         Buccal and lingual surfaces do not converge,
lingual diameter                              therefore wider.
of molars is narrower.

7. Roots shorter and more    Roots longer and stronger, multi-rooted
delicate, separate close              teeth trunk present and roots
to crown, but are longer             do not diverge near crown.
compared to crown size.

8. Dentin is less thick.               Dentin is thicker.

9. Enamel more permeable        Enamel less permeable, more calcified,
less calcified, more                    relatively less attrition.
attrition.

Above information modified from White & Folkens 2005 and here.

Tooth Class

Teeth in humans are classed into 4 separate classes of tooth based on function and position.  The classes include incisors, canines, premolars and molars, each aiding the other during the mastication of food.

teeth jawline

The human permanent dentition. Notice the larger size of the maxilla (upper) crowns compared to the mandible (lower) crowns and the differences between the roots of the same class of tooth. The first molar is the largest of the molar and the first to erupt. This can tooth can often have evidence of attrition on its cusps and crown when the 2nd and 3rd molars lack abrasion due to the 1st’s early eruption. Not to scale. Image credit: Biologycs 2012.

Maxilla Teeth:

Incisors (general: crowns flat and blade-like, outline of dentine occlusal patch is often rectangular or square if exposed by wear)

The upper incisor crowns are broad (or mesiodistally elongated) relative to their height, and have more lingual relief.  The central incisor crown is larger and more symmetrical than the lateral incisor crown but the roots are shorter and stouter to crown size than to the lateral incisor roots (White & Folkens 2005: 142).

Canines (general: crowns are conical and tusklike, canine roots longer than other roots in the same dentition, can be confused for incisors)

Upper canines are broad relative to their height and have more lingual relief, with apical occlusal wear that is largely lingual (towards the tongue) (White & Folkens 2005: 139).

Premolars (general: crowns are round, shorter than canine crowns and smaller than molar crowns, generally only have two cusps, usually single rooted but can be confused for canines but note shorter crown height)

The upper premolar crowns have cusps of nearly equal size and the crowns are more oval in occlusal outline.  Further to this the crowns of upper premolars also have strong occlusal grooves that orient mesiodistally between the major cusps, this is a key identifier for maxilla premolars (White & Folkens 2005: 140).

Molars (general: crowns larger, squarer, bear more cusps than any other tooth class, have multiple roots, 3rd molars sometimes mistaken for premolars)

Generally peaking the maxilla molars go from largest to smallest (1st molar to 3rd molar) in size and morphology.  The crowns generally have 4 cusps.  The 1st molar has three roots (two buccal and one lingual, which when seen from the buccal position the lingual root comes into view in the middle of the two buccal roots).  The occlusal surface is described as a rhomboid in shape with 4 distinctive cusps.  The 2nd molar has three roots but the two buccal roots are nearly parallel with each other, and is described as heart shape in the occlusal view.  The 3rd molar has three roots present but the two buccal roots are often fused, and the outline of the occlusal surface is also described as a heart shape.  The 3rd molar also shows greater developmental variation than either the 1st or 3rd molars, and are often the tooth that is congenitally missing.  All roots of the molars angle distally with respect to the major crown axes (White & Folkens 2005: 152).

Mandibular Teeth:

Incisors

Lower incisor crowns are narrow compared to their height and have comparatively little lingual topography, further to this the roots are usually more mesiodistally compressed in cross-section (White & Folkens 2005: 139).  The lower central incisor crowns are slightly smaller than the lower lateral crowns, with shorter roots relative to the crown and absolutely than lateral incisors (White & Folkens 2005: 142).

Canines

Lower canines have comparatively little lingual relief compared to the upper canines, and the apical occlusal wear is mostly labial.  The lower canines are also narrow relative to their height (White & Folkens 2005: 139).

Premolars

Lower premolar crowns are more circular in occlusal outline than upper premolars, and have comparatively weak median line grooves.  In lower premolars the long axes of the roots are angled distally relative to the vertical axis of the crown.  When IPCFs are present they are mesial and distal in location (White & Folkens 2005: 150).

Molars

Generally speaking the mandibular molars go from largest (1st molar) to smallest (3rd molar) in size and morphology, same as the maxilla molars.  The 1st mandibular molar is very recognizable as it has the largest crown with 5 cusps in the distinctive Y-5 cusp pattern and a pentagonal occlusal surface.  The two roots of the tooth tend to be long, separate and divergent.  The 3rd molar is smaller than the 1st or 2nd and have more irregular cusps and lack distal IPCFs, it also has two short and poorly developed roots that curve distally.  The occlusal surface is often described as crenelated and ovoid in shape.  The 2nd molar crown is an intermediate of the 1st and 3rd crowns (with 4 cusps) and roots (which have a distal inclination) in morphological terms, but has a distinctive +4 pattern of the occlusal surface.  All roots of the molars angle distally with respect to the major crown axes.

Graphic of the mandibular right quadrant highlighting a few of the specific dental anatomy terms from the above section. Image credit: modified from Gray’s Anatomy here.

Information for this section taken from White & Folkens 2005: 133-152 and here.

For tooth identification there are four questions to bear in mind:

A) To which category (or class) does the tooth belong?
B) Is the tooth permanent or deciduous?
C) Is the tooth an upper or a lower?
D) Where in the arch is the tooth located?

Although I’ve hinted at some of the answers above, those questions are a whole other post!  But do investigate the Human Bone Manual by White and Folkens (2005) for further information and/or Brothwell (1981) and Mays (1999).

Note

This post will be updated to include the muscles of mastication.

Further Information

  • Over at Bone Broke Jess Beck has a number of detailed posts focusing on teeth, with a few entries describing the anatomy of the various classes of teeth in detail (expect future posts though!).  Particularly useful is the Identifying Human Teeth: Human Dentition Cheat Sheet post which can handily be downloaded as a PDF!
  • Check out this handy sheet for anatomical and direction terminology for teeth.
  • The University of Illinois at Chicago have a wonderfully helpful molar identification sheet available here.
  • Can teeth heal themselves? I wish!  Only a bit by demineralization, learn more here.
  • Over at What Missing Link? James R Lumbard has a fantastic post on how the muscles work, which includes a case study on the musculature of the jaw.
  • An in-depth 13-minute dissection video of the muscles of mastication can be found here.  Please be aware that this is a real human dissection.

Bibliography

Brickley, M. & McKinley, J. I. (eds.). 2004. Guidance to the Standards for Recording Human Skeletal Remains. BABAO & Reading: IFA Paper No. 7. (Open Access).

Brothwell, D. R. 1981. Digging Up Bones: The Excavation, Treatment and Study of Human Skeletal Remains. Ithica: Cornell University Press. (Open Access).

Connell, B. 2004. Compiling a Dental Inventory. In Brickley, M. & McKinley, J. I. (eds.) Guidance to the Standards for Recording Human Skeletal Remains. BABAO & Reading: IFA Paper No.7: 8. (Open Access).

Gosling, J. A., Harris, P. F., Humpherson, J. R., Whitmore I.,& Willan P. L. T. 2008. Human Anatomy Color Atlas and Text Book. Philadelphia: Mosby Elsevier.

Hawks, J. 2005. Caring for the Edentulous. John Hawks Weblog. Accessed 29th October 2014.

Koff, C. 2004. The Bone Woman: Among the Dead in Rwanda, Bosnia, Croatia and Kosovo. London: Atlantic Books.

Larsen, C. S. 1997. Bioarchaeology: Interpreting Behaviour from the Human Skeleton. Cambridge: Cambridge University Press.

Lewis, M. E. 2009. The Bioarchaeology of Children: Perspectives from Biological and Forensic Anthropology. Cambridge: Cambridge University Press.

Mays, S. 1999. The Archaeology of Human Bones. Glasgow: Bell & Bain Ltd.

White, T. & Folkens, P. 2005. The Human Bone Manual. London: Elsevier Academic Press.

Skeletal Series B: The Biological Basis of Teeth and Anatomical Directional Terms

5 Mar

As mentioned in the previous post teeth are a distinct part of human anatomy and are of special interest to the human osteologist in archaeological contexts.  Teeth are the most resistant skeletal element to chemical or physical destruction during burial of human remains and as such are often over represented in the archaeological record.  As the only skeletal element that directly interacts with the environment (via mastication of food) teeth are a vital source of knowledge on the age, sex and diet of individuals and past populations (White & Folkens 2005).  There is now an extensive academic research body of materials and articles available on the study of both hominin and archaeological teeth.

Teeth in situation in the maxilla (upper jaw) and mandible (lower jaw) of a Saxon skull.

Origin & Anatomy

Dentition is often found in the lower and upper jaw of most animals, and are thought to have developed originally from fish scales (White & Folkens 2005, Shubin 2008).  Teeth throughout the animal kingdom have different uses, and come in a variety of different shapes and sizes.  Homo sapiens (modern-day humans) have two sets of teeth throughout their life.  Each set is located in the Mandible & Maxilla, and often refered to as the ‘dental arches’ or dental arcades”.  The deciduous dentition appears during early infancy and consist of around 20 individual teeth.  The permanent dentition gradually replaces the deciduous dentition, and is normally complete by around around 18 to 20 years of age, with females possibly exhibiting earlier eruption rates.  Typically the wisdom teeth (the 3rd molars) are the last to erupt fully towards the end of adolescence (Mays 1998).

The permanent dentition consists normally of 32 teeth with 8 teeth in each quadrant of the mandibular and maxilla dental arcades, although care has to be taken when noting the number from archaeological examples as teeth can easily fall out of the sockets.

Here is a basic diagram of the inside of a normal healthy molar tooth.  As you can see the second diagram shows the basics again but also introduces the 4 different teeth that the human dentition is composed of.  Enamel is one of the hardest biological substances and the hardest in man and, alongside the dentine, provides the main cutting framework for each tooth.  Unlike human bone tissue, the tooth cannot regrow or repair damage.

Basic anatomical details of a generic molar tooth.

Enamel is almost entirely inorganic material, mostly hydroxyapatite arranged in think rods whilst the “dentine is around 75% inorganic material (again hydroxyapatite) with a mainly collagen organic component” (Mays 1998: 11).

The general anatomy of teeth alongside the 4 classes of teeth In the human (Homo sapiens) dentition.

Again, please click on the above diagram for the detail to be clear.

The four classes of teeth in the human dentition consist of the following (White & Folkens 2005):

1) Incisors (4 altogether, two to each quadrant).  The incisors are  flat and blade like, whose main job is to cut the food before mastication takes place.

2) Canines (4 altogether).  The canines are tusk-like and are conical in shape.  Their main job is to pinch and grab the food helping to bring it into the mouth for mastication.

3) Pre-Molars (4 altogether).  They are rounder and shorter than the canine crowns (see below for directional and anatomical terms) and usually have two cusps.  They are used primarily for grinding the food.

4) Molars (6 altogether).  The molars have crowns that are squarer, larger, and bear more cusps than any other tooth.  They are used , along with the pre-molars, for grinding and chewing the food to make it more palatable and easier for the stomach to digest.

Standard Anatomical Directional Terminology

Here are some basics terms for tooth terminology and anatomical positions based on the White & Folkens manual (2005):

The Mesial portion of the tooth is the closest to the central incisors (see above diagram). The Distal portion of the tooth is the opposite of Mesial.  The Lingual part of the tooth faces the tongue, whilst the Labial portion faces the lips, and is only used for the incisors and canines.  The term Bucccal is used for the opposite of Lingual, for the Pre-Molars and Molars.  The Interproxmial surfaces contact the adjacent teeth.  The biting surface of both dental arches is called the Occlusal Surface.  The root of the tooth is called the Apical.  The Crowns are the enamel tops of each tooth, whilst the Cusps are the bumps on the Pre-Molars and Molars.

Cambridge Manuals On Human Evolution on the anthropology of modern teeth, a great core guide to how human teeth are studied in archaeology.

This is a basic guide  from White & Folkens (2005), does not include the very specific terminology for the cusps on the molars.  A handy guide to the introduction and more in-depth use of teeth is the book above.  In the human dentition the teeth as a whole have been noted as being very similar in design (or homogenized) in comparison to other species whilst the morphological variation of each class of tooth (think canine, molar etc) has increased over on each of the teeth (White & Folkens 2005).  This seems like a contradiction in terms but human teeth are designed for an omnivorous diet, meaning that that  our dentition is designed to chew both plant and meat foods for our dietary requirements.

When the teeth are found in relative isolation they can be sided and matched with relative ease to either the maxilla or mandible portions of the human skull.  This can be done by noting the wear patterns on the crowns of each tooth and by looking at the size and root variation of the tooth.  Generally speaking males tend to have larger teeth than females, although there are idiosyncrasies present throughout human evolution (Jurmain et al 2011).  A later post will include talks on the palaeopathology of tooth disease and trauma.  In the meantime this guide should help in providing the basic information.

Until next time, keep smiling! (A. Boisei reconstruction pictured – notice the large teeth made for chewing tough fibrous plant material and flesh).

Bibliography

Jurmain, R. Kilgore, L. & Trevathan, W.  2011. Essentials of Physical Anthropology International Edition. London: Wadworth.

Mays, S. 1999. The Archaeology of Human Bones. Glasgow: Bell & Bain Ltd.

Schwartz, J. H. 2007. Skeleton Keys: An Introduction to Human Skeletal Morphology. New York: Oxford University Press.

Shubin, N. 2008.  Your Inner Fish: A Journey into the 3.5 Billion Year History of the Human Body. London: Pantheon.

White, T. & Folkens, P. 2005. The Human Bone Manual. London: Elsevier Academic Press.