Dental Osteology

7/28/2019 Dental Osteology

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OsteologyOsteology -- TeethTeeth

Human Odontology


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OsteologyOsteology TeethTeeth --

ReferencesReferences

l Bass (Section 4 Douglas Ubelaker)


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Teeth in Anthropology andTeeth in Anthropology and

PalaeontologyPalaeontology

l Well preserved

l

Resist decayl Frequently outlast bones

l Major role in study of fossil man

(Ubelaker, in Bass)


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TeethTeethAnatomical PartsAnatomical Parts

l 3 parts:

1.Root

2. Crown

3. Neck


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TeethTeeth -- RootsRoots

Buried in jaw

Below crown and neck

Covered with cementum


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From Brothwell


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TeethTeeth -- CrownCrown

l Projects beyond gum

l

Covered with enamel


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From Brothwell


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TeethTeeth -- NeckNeck

l Slightly constricted

l Below crown

l Encircled by gum tissue


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From Brothwell


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TeethTeethApical ForamenApical Foramen

At apex of each root

Leads through root canal to pulp cavity


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From Brothwell

Teeth apical foramen


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TeethTeeth -- ComponentsComponents

Dentine

Enamel

Cementum

Pulp


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Teeth components: dentine, enamel, cementum, pulp

From Brothwell


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TeethTeeth -- DentineDentine

Very sensitive

Yellow colour

Surrounds pulp cavity (tooth cavity)

Covered by enamel on exposed parts

Covered by cementum on part implanted in

jaw

Forms most of tooth


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Teeth - dentine

From Brothwell


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TeethTeeth -- EnamelEnamel

Insensitive

Very hard

White

Covers, protects dentine of crown


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Teeth - enamel

From Brothwell


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TeethTeeth -- CementumCementum

Bony covering

Covers dentine of root and neck


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Teeth - cementum

From Brothwell


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TeethTeeth -- PulpPulp

l Fibrous material

l Contains nerves and vessels that pass

through root canal

l Occupies tooth cavity (pulp cavity) in

dentine


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Teeth - pulp

From Brothwell


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TeethTeeth -- SocketSocketl Each tooth is contained within a bony

socket (alveolus)

l Alveolus narrows toward bottom allows

tooth a large pressure surface

l Between tooth and socket is periodontal

membrane: vascular, modified periosteum;attaches to cementum and alveolar wall


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From Grant

Teeth socket or alveolus


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From Grant

Teeth

socket

Each tooth

is contained

within bony

socket(alveolus)

which

narrows

toward

bottom allows large

pressure

surface


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TeethTeeth -- PermanentPermanentl Permanent = adult = secondary

l 32 permanent teeth

l 16 in each upper and lower dental arch

(arcade); half of arch is a quadrant


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Upper (maxillary)dental

arcade

Lower(mandibular)

dental arcade

Dental arcades - schematic

Each arcade is

divided into aright and left

quadrant


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Upper (maxillary)dental

arcade

Lower(mandibular)

dental arcade

Dental arcades - schematic Quadrants are numbered

from 1 to 4 right

maxillary is quadrant 1,

left maxillary is

quadrant 2, left

mandibular is quadrant

3, and right mandibular

is quadrant 4

Start with right

maxillary 1st incisor, 1-

1, and continue to 3rdmolar, which is 1-8;

then 2-1 to 2-8, and so

on


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From Brothwell

Teeth permanent (adult, secondary) types found in each arcade


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TeethTeeth PermanentPermanent -- TypesTypes1. Incisors

2. Canines

3. Premolars

4. Molars

Classification by morphology (shape) and

function


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From Brothwell

Teeth permanent (adult, secondary) incisors for cutting


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TeethTeeth PermanentPermanent -- CaninesCaninesl Tear

l Incise

l Hold


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From Brothwell

Teeth permanent (adult, secondary) canines for tearing,

incising, and holding


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TeethTeeth PermanentPermanent --

PremolarsPremolarsl Broad occlusal surfaces

l Usually two cusps

l For grinding


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From Brothwell

Teeth permanent (adult, secondary) premolars for grinding,

with broad occlusal surfaces and multiple cusps


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TeethTeeth PermanentPermanent -- MolarsMolarsl Similar to premolars

l Broader occlusal surfaces

l For grinding


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TeethTeeth --AbbreviationsAbbreviationsl I = incisor

l C = canine

l PM = premolar

l M = molar

l Premolars and molars can be numbered

with superscript or subscript to indicate

upper or lower arch


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From Brothwell

Teeth abbreviations

M PM C I

M PM C I


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TeethTeeth Dental FormulaDental Formulal Eight teeth in each quadrant: two incisors,

one canine (cuspid), two premolars

(bicuspids), three molars

l Adult human formula: 2-1-2-3; formula

numbering is from incisors to molars

l All adult teeth except molars are precededby primary or deciduous teeth


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TeethTeeth Third MolarThird Molarl Quite variable in time of appearance, or

even if it appears

l Often called 18 year molar (i.e. presence

indicates individual is at least 18 years old)


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From Brothwell

Teeth third molar quite variable in time of appearance


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TeethTeeth -- DeciduousDeciduousl Deciduous = primary = temporary = milk

l Two incisors, one canine, two molars in

each quadrant; hence 10 deciduous teeth in

each upper and lower arch

lNo premolars

l Abbreviate i, c, m, with superscripts orsubscripts to denote upper or lower molars


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From Brothwell

Teeth deciduous = primary = temporary = milk

(no premolars)

Formula: 2-1-2


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From Brothwell

Teeth deciduous = primary = temporary = milk

(no premolars)

Order of eruption: medial incisor, lateral

incisor, 1st molar, canine, 2nd molar


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TeethTeeth DeciduousDeciduous

Time of EruptionTime of Eruptionl Medial incisor: 6-8 months

l Lateral incisor: 8-10 months

l First molar: 12-16 months

l Canine: 16-20 months

l Second molar: 20-24 months

l Followed by interval of 4 years

l In 6th year, permanent teeth start to erupt


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From Brothwell

Teeth

deciduous -time of

eruption

In 6th year,

permanentteeth start to

erupt


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TeethTeeth Eruption ofEruption of

Permanent TeethPermanent Teethl 1st molars are first permanent teeth: often

known as 6 year molars

l Replacement of deciduous teeth bypermanent teeth: medial incisors, lateralincisors, 1stpremolars, canines, and 2nd

premolars

l 2nd molars erupt about 12th year; 3rd molarsabout 18th year (highly variable)


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From Brothwell

Teeth

deciduous -time of

eruption

In 6th year,

permanentteeth start to

erupt; 2nd

molars about

12th year; 3rd

molars about18th year

highly

variable


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TeethTeeth SurfacesSurfaces -- LingualLinguall Lingual = toward the tongue

l Opposite of labial or buccal surfaces


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TeethTeeth SurfacesSurfaces Mesial andMesial and

DistalDistall Medial surfaces of front teeth and anterior

surfaces of side teeth are mesial (proximal)

l Mesial = toward the midline (imagine

stretching dental arcade out into a straight

line: medial surfaces = mesial surfaces)

l Opposite surfaces = distal


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Teeth surfaces occlusal - schematic

Occlusal surface: biting surface, masticatory surface;

where maxillary and mandibular surfaces meet


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TeethTeeth SurfacesSurfaces ContactContact

SurfacesSurfacesl Proximal (mesial) and distal surfaces are

contact surfaces

l Exceptions: distal surfaces of last molars

l Proximal (mesial) and distal surfaces rub

against one another with chewing motion,

producing areas of wear these areas maymatch on adjacent teeth


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Teeth surfaces contact (interproximal) surfaces - schematic

Proximal (mesial) and distal surfaces are contact

surfaces; exception is distal surface of last molar


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TeethTeeth -- CrownsCrownsl Human crowns: evolved from tritubercular

or tricuspid tooth

l Two labial tubercles and one lingual

tubercle can be seen on each tooth

(Grant)


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Teeth crowns schematic (occlusal view)

Human crowns: evolved from tritubercular (tricuspid) tooth

Labial

tubercles

Labial

tubercles

Lingual

tubercle

Lingual

tubercle


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TeethTeeth CrownsCrowns -- continuedcontinuedl Lower molars: usually have 5 tubercles

two labial, two lingual, and a fifth distal;

may be reduced on 3rd lower molar(Grant)


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TeethTeeth -- OcclusionOcclusionl Upper arch teeth project labially beyond

lower arch teeth

l Hence labial borders of occlusal surfaces oflower premolars and molars are worn and

rounded; lingual borders are sharp; reverse

holds for upper premolars and molars(Grant)


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Teeth occlusion - schematic

Maxilla

Upper

teeth

Lower

teeth

Mandible

Upper arch teeth

project laterally

beyond lower

arch teeth


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Teeth occlusion

Note how lingualborder of

maxillary tooth is

worn and

rounded, and

buccal border is

sharp

From Grant

Types of dental occlusion patterns


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Slight overlap of

upper teeth over

lower teeth

Modified from Brothwell



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Slight overlap of

upper teeth over

lower teeth;

incisors do not

come into

occlusion

From Brothwell



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TeethTeeth -- DevelopmentDevelopmentl Enamel: ectodermal origin

l Begins to develop during 3rd fetal month

l From buds that sprout from ingrowing plate

(primary dental lamina) of ectodermal cells

l Each bud takes form of cap covering

mesodermal papilla from which remainderof tooth is formed (Grant)


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Growth and Calcification ofGrowth and Calcification of

Permanent TeethPermanent Teethl Begins in 1st molars (6 year molars) about

time of birth, in incisors and canines (upper

lateral incisors excepted) from 4th

to 6th

month, in upper lateral incisors from 10th to11th month, and in premolars and 3rd molarsearly in 2nd year

l Useful in radiologic diagnosis of age(Grant)


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Average

developmentalstages of human

dentition note

calcification and

growth

From Brothwell


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Permanent

tooth

eruptiontimes for

boys and

girls note

great

variationtimes in

tooth

eruption

From

Brothwell


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TeethTeeth Nerve SupplyNerve Supply Upper teeth: maxillary nerve (V2)

Lower teeth: mandibular nerve (V3)


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TeethTeeth MeasurementsMeasurements

Tooth HeightTooth Heightl From cementoenamel junction to maximum

height of crown

l Often not used archaeologically: many pre-historic peoples wore teeth down (attrition)

due to grit in diet


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TeethTeeth MeasurementsMeasurements --

Mesiodistal DiameterMesiodistal Diameterl Maximum diameter between mesial and

distal contact points

Teeth measurements schematic crown view


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labial or buccal

lingual

Mesiodistal

diameter

maximum

diameter

between mesial

and distal

contact points


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Buccolingual DiameterBuccolingual Diameterl Maximum diameter at right angles to

mesiodistal diameter



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labial or buccal

lingual

Buccolingual

diameter

maximum

diameter at

right angles to

mesiodistal

diameter


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Crown ModuleCrown Modulel A measurement of relative crown mass

l Average of mesiodistal and buccolingual

diameters


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TeethTeeth SupernumerarySupernumerary --

continuedcontinuedl Often bilateral

l May be retained deciduous teeth in adult

l May be located in many different positions

around dental arch

(Ubelaker)


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Teeth

supernumerary

Often bilateral

May be

retained

deciduousteeth in adult

Various

locations

around dentalarch

From

Brothwell


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TeethTeeth -- RotationRotation

l May be rotated up to 180 degrees from

usual dental orientation

l Most common in 2ndpremolars


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Teeth

crowding

Crowding

causes change

in position of

one or more

teeth

From Brothwell


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TeethTeeth CrowdingCrowding -- continuedcontinued

l Often seen with impacted 3rd molars and

rotated teeth

l Rarely seen in deciduous teeth: lots of roomfor eruption of teeth

l Incisors most affected by dental crowding

(Ubelaker)


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Teeth

crowding

Often seen with

impacted 3rd

molars and

rotated teeth

Incisors are

most affected by

dental crowding

From Brothwell


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TeethTeeth MorphologicalMorphological

VariationVariation1. Molar cusp pattern

2. Extra cusps

3. Shovel-shaped teeth

4. Peg-shaped teeth

5. Taurodontism

6. Enamel extension and pearls

7. Extra or missing roots


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TeethTeeth Molar Cusp PatternMolar Cusp Pattern

l Anthropological use: distinguishing modern

populations, assessing primate ancestry

l Assessment limited in prehistoricpopulations due to grit-related attrition of

cusps

l

Maxillary molars have different patternsfrom mandibular patterns

T th CM ill M l C


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TeethTeeth -- Maxillary Molar CuspMaxillary Molar Cusp

PatternPatternl 3 or 4 cusps, separated by well-defined

grooves (Bass, fig. 4-13)

l 1st maxillary: 4 cusps, same sizel 2nd maxillary: 4th cusp (= hypocone) usually

smaller

l 3rd

maxillary: hypocone either absent, ormuch reduced (cuspule on distal surface)

Teeth molar cusp pattern maxillary


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Teeth molar cusp pattern - maxillary

1st molar

4 cusps,

same size

2nd molar

4th cusp

usually

smaller

(hypocone)

3rd molar

hypocone

either absent

or much

reduced(cuspule on

distal

surface)

T thT th M dib l M lM dib l M l


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TeethTeeth Mandibular MolarMandibular Molar

Cusp PatternCusp Patternl 4 or 5 cusps

l Cusps arranged so grooves between them

form T or Yl Patterns: Y5, Y4, +5, +4

l Y5: common prehistoric pattern

l Y4, +5, +4: more recent(Bass)

Teeth molar cusp pattern mandibular


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Teeth molar cusp pattern - mandibular

1st molar

Y5 pattern

very

common

Y5 +5 +4

Y42nd and 3rd

molars have

other 3

patterns

M dib l M l CM dib l M l C


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Mandibular Molar CuspMandibular Molar Cusp

PatternPattern -- continuedcontinuedl Evolution: Y5 -> Y4 or +5 -> +4

l Modern: Y5 often seen on mandibular 1st

molarl Modern: 2nd and 3rd molars have mainly

other three patterns

l Cusp patterns may not be exact hard todefine (Bass; also see Bass fig 4-14)


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TeethTeeth Extra CuspsExtra Cusps

l May be on various maxillary andmandibular molar surfaces

l

Protostylid: extra cusp on anterior buccalsurface of mandibular molars; e.g. SouthAfrican Australopithecines, Meganthropus(Java), Sinanthropus (China); in modern

Pima Indians(Bass; Bass figure 4-15b)


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Teeth extra cusps


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Carabellis cusps: on anterior lingual surfaces of

maxillary molars

mesial

distal

lingualbuccal

Carabellis

cusp


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TeethTeeth PegPeg--ShapedShaped

l Teeth are particularly small

l Especially 3rd molars, lateral incisors

l Often related to congenital absence


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TeethTeeth -- TaurodontismTaurodontism

l In molars

l Pulp cavity enlarged, roots reduced

lNeanderthals, other fossils

l Occasionally in modern populations

l Subtypes: cynodont, hypotaurodont,

mesotaurodont, hypertaurodont(Bass, fig. 4-17a)


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TeethTeeth Extra or MissingExtra or Missing


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TeethTeeth Extra or MissingExtra or Missing

RootsRootsl From 1st molar to 3rd molar is trend for roots

to be less divergent, more fused

l Similar trend in premolars(Bass)


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TeethTeeth Enamel ExtensionsEnamel Extensions


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TeethTeeth Enamel Extensions,Enamel Extensions,

PearlsPearlsl In some molars, premolars

l Extension of crown enamel may extend

between rootsl May terminate in enamel cluster: enamel

pearl (may be obscured in alveolus)

l

In many modern groups(Bass, fig. 4-17b)

Teeth

l


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enamel

extensions,

pearls

In some

molars,

premolars

Extension of

crown enamel

between roots

From Brothwell


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TeethTeeth Occlusal WearOcclusal Wear

l Mastication (chewing): upper and lowerarch teeth rub each other and any containeddietary grit

l Abrasion by grit wears occlusal surfaces,may erode cusp pattern; varies with diet

l Could be rapid, e.g. American Indians(grinding stone grit)

(Bass)

Teeth occlusal wear abrasion by grit wears occlusal

surfaces, may erode cusp pattern, varies with diet


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From Brothwell

y p p


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Teeth occlusal wear : different rates of attrition in different

populations age estimation from attrition in one population


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From Brothwell

may be different from another; also individual variation within

group limits accuracy


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TeethTeeth Cultural DeformationCultural Deformation

l Filed, chipped, drilled, incised decorative

l Multiple different population groups

l Mainly incisors: easier to work on, mostvisible to others

l Interproximal grooves (especially molar):

often associated with caries, alveolarabscesses - ? pain relief efforts (Bass)


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Dental

development


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From

Brothwell

development

Sequence ofcalcification and

eruption very

useful in aging,

particularly in

young

T th O l i


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TeethTeeth -- OcclusionOcclusion

l Mongoloid: frequent edge-edge occlusion

l Caucasoids: usually slight overbite

l Underbites uncommon in all groups

Caucasoids



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Caucasoids

usually slight

overbite

From Brothwell

Mongoloids

frequent edgeto edge

occlusion

T thT th S l Di hiS l Di hi


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TeethTeeth Sexual DimorphismSexual Dimorphism

Neither adult nor deciduous teeth have

distinct dimorphic indicators

Male teeth may be larger than female teethwithin a given population


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END

Dental Osteology

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