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									Osteology - Teeth

Human Odontology

Osteology – Teeth References
l Bass

(Section 4 – Douglas Ubelaker)

Teeth in Anthropology and Palaeontology
l Well

preserved l Resist decay l Frequently outlast bones l Major role in study of fossil man (Ubelaker, in Bass)

Teeth – Anatomical Parts
l

3 parts: 1. Root 2. Crown 3. Neck

Teeth - Roots
Buried in jaw • Below crown and neck • Covered with cementum
•

From Brothwell

Teeth - Crown
l Projects beyond gum l Covered

with enamel

From Brothwell

Teeth - Neck
l Slightly constricted l Below

crown l Encircled by gum tissue

From Brothwell

Teeth – Apical Foramen
• At apex of each root • Leads through root canal to pulp cavity

Teeth – apical foramen

From Brothwell

Teeth - Components
Dentine • Enamel • Cementum • Pulp
•

Teeth – components: dentine, enamel, cementum, pulp

From Brothwell

Teeth - Dentine
• • • • • •

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

Teeth - dentine

From Brothwell

Teeth - Enamel
Insensitive • Very hard • White • Covers, protects dentine of crown
•

Teeth - enamel

From Brothwell

Teeth - Cementum
Bony covering • Covers dentine of root and neck
•

Teeth - cementum

From Brothwell

Teeth - Pulp
l Fibrous

material l Contains nerves and vessels that pass through root canal l Occupies tooth cavity (pulp cavity) in dentine

Teeth - pulp

From Brothwell

Teeth - Socket
l 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

Teeth – socket or alveolus

From Grant

Teeth – socket Each tooth is contained within bony socket (alveolus) which narrows toward bottom – allows large pressure surface From Grant

Teeth - Permanent
l Permanent

= adult = secondary l 32 permanent teeth l 16 in each upper and lower dental arch (arcade); half of arch is a quadrant

Dental arcades - schematic Upper (maxillary) dental arcade Each arcade is divided into a right and left quadrant

Lower (mandibular) dental arcade

Dental arcades - schematic Upper (maxillary) dental arcade

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

Lower (mandibular) dental arcade

Start with right maxillary 1st incisor, 11, and continue to 3rd molar, which is 1-8; then 2-1 to 2-8, and so on

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

From Brothwell

Teeth – Permanent - Types
Incisors 2. Canines 3. Premolars 4. Molars
1.

Classification by morphology (shape) and function

Teeth – Permanent - Incisors
l Cutting teeth

Teeth – permanent (adult, secondary) – incisors – for cutting

From Brothwell

Teeth – Permanent - Canines
l Tear l Incise l Hold

Teeth – permanent (adult, secondary) – canines – for tearing, incising, and holding

From Brothwell

Teeth – Permanent Premolars
l Broad

occlusal surfaces l Usually two cusps l For grinding

Teeth – permanent (adult, secondary) – premolars – for grinding, with broad occlusal surfaces and multiple cusps

From Brothwell

Teeth – Permanent - Molars
l Similar

to premolars l Broader occlusal surfaces l For grinding

Teeth – permanent (adult, secondary) – molars – for grinding, similar to premolars, with broader occlusal surfaces and multiple cusps

From Brothwell

Teeth - Abbreviations
lI

= 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

Teeth – abbreviations M PM C I

M

PM

C

I

From Brothwell

Teeth – Dental Formula
l 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 preceded by primary or deciduous teeth

Teeth – dental formula 3 2 1 2

3 Formula: 2-1-2-3

2

1

2

From Brothwell

Teeth – Third Molar
l 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)

Teeth – third molar – quite variable in time of appearance

From Brothwell

Teeth - Deciduous
l Deciduous

= primary = temporary = milk l Two incisors, one canine, two molars in each quadrant; hence 10 deciduous teeth in each upper and lower arch l No premolars l Abbreviate i, c, m, with superscripts or subscripts to denote upper or lower molars

Teeth – deciduous = primary = temporary = milk (no premolars)

Abbreviate: i, c, m

From Brothwell

Teeth – Deciduous continued
incisors and canines are small versions of adult teeth l Formula: 2-1-2 l First deciduous maxillary molars are precursors of adult maxillary premolars l Deciduous second molars are replicas of permanent first molars in respective maxilla or mandible (Ubelaker)
l Deciduous

Teeth – deciduous = primary = temporary = milk (no premolars)

Formula: 2-1-2

From Brothwell

Teeth – Deciduous – Order of Eruption
l Medial incisor, lateral incisor, 1st

molar,

canine, 2nd molar l Completed in first 24 months l Useful in aging infant and child skeletal material (Ubelaker)

Teeth – deciduous = primary = temporary = milk (no premolars)

Order of eruption: medial incisor, lateral incisor, 1st molar, canine, 2nd molar

From Brothwell

Teeth – Deciduous – Time of Eruption
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
l Medial

Teeth – deciduous time of eruption In 6th year, permanent teeth start to erupt

From Brothwell

Teeth – Eruption of Permanent Teeth
l 1st

molars are first permanent teeth: often known as 6 year molars l Replacement of deciduous teeth by permanent teeth: medial incisors, lateral incisors, 1st premolars, canines, and 2nd premolars l 2nd molars erupt about 12th year; 3rd molars about 18th year (highly variable)

Teeth – deciduous time of eruption In 6th year, permanent teeth start to erupt; 2nd molars about 12th year; 3rd molars about 18th year – highly variable From Brothwell

Teeth - Surfaces
l 1. 2. 3. 4. 5.

Each tooth has 5 surfaces: Labial or buccal Lingual Mesial Distal Occlusal

Teeth – Surfaces – Labial or Buccal
l Anterior

surfaces of front teeth and lateral surfaces of side teeth l Labial (toward lip) anteriorly: for incisors and canines l Buccal (toward cheek) laterally: for premolars and molars

Teeth – surfaces – labial or buccal - schematic labial labial

buccal

buccal

Labial (toward lip): anterior surfaces of incisors and canines Buccal (toward cheek): lateral surfaces of premolars and molars

Teeth – Surfaces - Lingual
l Lingual

= toward the tongue l Opposite of labial or buccal surfaces

Teeth – surfaces – lingual - schematic

labial

labial

buccal lingual

buccal

Lingual: toward the tongue – opposite of lingual or buccal (same for all teeth)

Teeth – Surfaces – Mesial and Distal
l 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

Teeth – surfaces – mesial and distal - schematic

Mesial: toward the midline Distal: opposite of mesial

Teeth – Surfaces - Occlusal
l Biting

surfaces are occlusal l Occlusal = masticatory

Teeth – surfaces – occlusal - schematic

Occlusal surface: biting surface, masticatory surface; where maxillary and mandibular surfaces meet

Teeth – Surfaces – Contact Surfaces
l 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 may match on adjacent teeth

Teeth – surfaces – contact (interproximal) surfaces - schematic

Proximal (mesial) and distal surfaces are contact surfaces; exception is distal surface of last molar

Teeth - Crowns
l Human

crowns: evolved from tritubercular or tricuspid tooth l Two labial tubercles and one lingual tubercle can be seen on each tooth (Grant)

Teeth – crowns – schematic (occlusal view) Human crowns: evolved from tritubercular (tricuspid) tooth

Labial tubercles

Labial tubercles

Lingual tubercle

Lingual tubercle

Teeth - Crowns
l Incisors:

labial tubercles fuse, form cutting (incisal) edge (mesiodistal ridge or edge) l Joined to indistinct lingual tubercle by two faint lines (cingulum) that enclose triangular space; among North American Indians these may be pronounced and give incisors a shovel-like appearance (Grant)

Teeth – incisor – schematic (occlusal view) Human crowns: evolved from tritubercular (tricuspid) tooth Incisor Labial tubercles have fused Lingual tubercle indistinct

Labial tubercles of incisor teeth fuse – form cutting or incisal edge (mesiodistal ridge or edge)

Teeth – incisor – schematic (occlusal view) Human crowns: evolved from tritubercular (tricuspid) tooth Incisor Labial tubercles have fused Cingulum Lingual tubercle indistinct Cingulum Labial tubercles join with indistinct lingual tubercle by two faint lines – cingula – enclosing triangular space; may give incisor a shovel shape (see Bass, p. 280)

Teeth – Crowns - continued
l Canines:

labial tubercles fuse to form single large cone and lingual tubercle is often well defined (Grant)

Teeth – Crowns - continued
l Molars:

all have as basis two labial tubercles, proximal lingual tubercle l Upper molars: additional lingual tubercle placed distally, making 4 tubercles in total l 1st molar always has 4 tubercles, 2nd commonly, 3rd variably (Grant)

Teeth – Crowns - continued
l Lower

molars: usually have 5 tubercles – two labial, two lingual, and a fifth distal; may be reduced on 3rd lower molar (Grant)

Teeth - Roots
canines, premolars: single root l 1st upper premolar: commonly bifid or double root l Lower molars: 2 flattened roots, one proximal, one distal l Upper molars: 3 conical roots, 2 smaller labial, 1 larger lingual (Grant)
l Incisors,

Teeth – Roots - continued
l Teeth

roots are flattened proximodistally, especially in lower teeth l Upper teeth: compromise between rounded and conical, and flattened; upper medial incisor has roundest root, canines have longest roots, molar roots often recurved

Teeth - Occlusion
l Upper

arch teeth project labially beyond lower arch teeth l Hence labial borders of occlusal surfaces of lower premolars and molars are worn and rounded; lingual borders are sharp; reverse holds for upper premolars and molars (Grant)

Upper arch teeth project laterally beyond lower arch teeth

From Grant

Teeth – occlusion - schematic Upper arch teeth project laterally beyond lower arch teeth

Maxilla

Upper teeth Lower teeth

Mandible

Teeth – occlusal wear of premolars and molars Upper arch teeth project laterally beyond lower arch teeth – this causes wear of buccal borders of occlusal surfaces of lower premolars and molars, and sharp lingual borders; reverse for upper molars and premolars

Maxilla

Upper teeth Lower teeth

wear

Mandible

Teeth – occlusion

Note how lingual border of maxillary tooth is worn and rounded, and buccal border is sharp From Grant

Types of dental occlusion patterns Slight overlap of upper teeth over lower teeth

Modified from Brothwell

Teeth – Occlusion - continued
l

l l

Upper incisors in most biological groups “overbite” lower incisors, do not come into occlusion Upper and lower dental arches are flush with each other posteriorly Upper medial incisors are relatively large, and 3rd upper molars relatively small; when arches are in occlusion, most teeth bite on two teeth

Types of dental occlusion patterns Slight overlap of upper teeth over lower teeth; incisors do not come into occlusion

From Brothwell

Teeth - Development
l 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 remainder of tooth is formed (Grant)

Teeth – Development continued
l At

same time, buds from which enamel of corresponding permanent teeth arise sprout from lingual surface of dental plate, but remain temporarily quiescent l The 3 permanent molars develop similarly from backward extension of plate

Growth and Calcification of Permanent Teeth
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 to 11th month, and in premolars and 3rd molars early in 2nd year l Useful in radiologic diagnosis of age (Grant)
l Begins

Average developmental stages of human dentition – note calcification and growth

From Brothwell

Permanent tooth eruption times for boys and girls – note great variation times in tooth eruption

From Brothwell

Growth and Calcification of Permanent Teeth - continued
disturbances in early infancy can affect anterior teeth, but will omit upper lateral incisors l Enamel defects can not be corrected once they have occurred (Grant)
l Metabolic

Teeth – Nerve Supply
Upper teeth: maxillary nerve (V2) • Lower teeth: mandibular nerve (V3)
•

Teeth – Sexual Dimorphism
l Not

well enough marked in either primary or secondary teeth to allow sex determination l Males generally have larger teeth

Teeth - Measurements
Tooth height 2. Mesiodistal diameter 3. Buccolingual diameter 4. Crown module
1.

Teeth – Measurements – Tooth Height
l From

cementoenamel junction to maximum height of crown l Often not used archaeologically: many prehistoric peoples wore teeth down (attrition) due to grit in diet

Teeth – measurements – tooth height

Tooth height – from cementoenamel junction to maximum height of crown

Modified from Brothwell

Teeth – Measurements Mesiodistal Diameter
l Maximum diameter between mesial and

distal contact points

Teeth – measurements – schematic – crown view labial or buccal

Mesiodistal diameter – maximum diameter between mesial and distal contact points

lingual

Teeth – Measurements – Buccolingual Diameter
l Maximum

diameter at right angles to mesiodistal diameter

Teeth – measurements – schematic – crown view labial or buccal

Buccolingual diameter – maximum diameter at right angles to mesiodistal diameter

lingual

Teeth – Measurements – Crown Module
lA

measurement of “relative crown mass” l Average of mesiodistal and buccolingual diameters

Teeth – measurements – schematic – crown view labial or buccal

Crown module – a measurement of relative crown mass Crown module = (mesiodistal diameter + buccolingual diameter) /2

lingual

Teeth - Supernumerary
l Extra teeth, in addition to usual dental

formula l May occur in any one of the 4 basic types of teeth l May resemble normal teeth, or morphology may be different entirely l Rarely in deciduous dentition (Ubelaker)

Teeth – supernumerary Extra teeth in addition to usual dental formula May occur in any one of 4 basic tooth types Morphology variable

From Brothwell

Teeth – Supernumerary continued
l Often

bilateral l May be retained deciduous teeth in adult l May be located in many different positions around dental arch (Ubelaker)

Teeth – supernumerary Often bilateral May be retained deciduous teeth in adult Various locations around dental arch From Brothwell

Teeth – Congenital Absence
l One or more may not be present

most commonly missing l Not to be confused with unerupted teeth or teeth lost antemortem l X-ray will show unerupted teeth (Ubelaker)

l 3rd molar

Teeth – Absence - continued
l Teeth

lost antemortem: alveolus (socket) may have resorbed l Teeth lost postmortem: root cavities still present l If missing tooth once contacted adjacent teeth, wear facets may be seen on remaining teeth (Ubelaker)

Teeth – absence

Wear facets on mesial and distal surfaces are indicative of an interproximal articulation with adjacent teeth; lack of wear facets may indicate that adjacent teeth were lost early on or did not erupt

Modified from Brothwell

Teeth - Rotation
l May

be rotated up to 180 degrees from usual dental orientation l Most common in 2nd premolars

Teeth – rotation A tooth may be rotated up to 180 degrees from its usual position Most common in 2nd premolars

From Brothwell

Teeth - Crowding
l In

adult, crowding may be seen, with resultant change in position of one or several teeth l Usually result of small mandible without reduction in tooth size; space in alveolus not large enough to allow teeth to erupt in usual positions, so must erupt in altered positions (Ubelaker)

Teeth – crowding Crowding causes change in position of one or more teeth

From Brothwell

Teeth – Crowding - continued
seen with impacted 3rd molars and rotated teeth l Rarely seen in deciduous teeth: lots of room for eruption of teeth l Incisors most affected by dental crowding (Ubelaker)
l Often

Teeth – crowding Often seen with impacted 3rd molars and rotated teeth Incisors are most affected by dental crowding

From Brothwell

Teeth – Morphological Variation
1. 2. 3. 4. 5. 6. 7.

Molar cusp pattern Extra cusps Shovel-shaped teeth Peg-shaped teeth Taurodontism Enamel extension and pearls Extra or missing roots

Teeth – Molar Cusp Pattern
l Anthropological use: distinguishing modern

populations, assessing primate ancestry l Assessment limited in prehistoric populations due to grit-related attrition of cusps l Maxillary molars have different patterns from mandibular patterns

Teeth - Maxillary Molar Cusp Pattern
or 4 cusps, separated by well-defined grooves (Bass, fig. 4-13) l 1st maxillary: 4 cusps, same size l 2nd maxillary: 4th cusp (= hypocone) usually smaller l 3rd maxillary: hypocone either absent, or much reduced (cuspule on distal surface)
l3

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)

Teeth – Mandibular Molar Cusp Pattern
l4

or 5 cusps l Cusps arranged so grooves between them form T or Y l Patterns: Y5, Y4, +5, +4 l Y5: common prehistoric pattern l Y4, +5, +4: more recent (Bass)

Teeth – molar cusp pattern - mandibular Y5 +5 +4

1st molar – Y5 pattern very common

2nd and 3rd molars have other 3 patterns

Y4

Mandibular Molar Cusp Pattern - continued
Y5 -> Y4 or +5 -> +4 l Modern: Y5 often seen on mandibular 1st molar l Modern: 2nd and 3rd molars have mainly other three patterns l Cusp patterns may not be exact – hard to define (Bass; also see Bass fig 4-14)
l Evolution:

Mandibular Molar Cusp Pattern – continued
genetically unstable; common to have irregular cusp pattern l Bass, tables 4-2, 4-3, 4-4
l 3rd molar:

Teeth – Extra Cusps
l May

be on various maxillary and mandibular molar surfaces l Protostylid: extra cusp on anterior buccal surface of mandibular molars; e.g. South African Australopithecines, Meganthropus (Java), Sinanthropus (China); in modern Pima Indians (Bass; Bass figure 4-15b)

Teeth – extra cusps mesial

protostylid lingual buccal

distal Protostylid: extra cusp on anterior buccal surface of mandibular molars

Teeth – Extra Cusps continued
l Carabelli’s

cusps (tuberculum Carabelli, tuberculum anomale): on anterior lingual surfaces of maxillary molars l Multiple forms, from pit to cusp l Cusp: modern populations l Pit: prehistoric, e.g. Australopithecines (none in fossil hominoids) (Bass)

Teeth – extra cusps mesial Carabelli’s cusp buccal lingual

distal Carabelli’s cusps: on anterior lingual surfaces of maxillary molars

Teeth – Shovel-Shaped
l Especially in Mongoloid populations

extension of incisor lateral borders l Occasional buccal extension of lateral borders: double shovel-shaped incisor (usually maxillary) (Bass, fig. 4-4) l Marked lingual extension of incisor lateral borders: barrel shape (maxillary lateral incisors)

l Lingual

Teeth – shovel shaped Especially in mongoloid populations Lingual extension of incisor lateral borders

From Brothwell

Teeth – Peg-Shaped
l Teeth

are particularly small l Especially 3rd molars, lateral incisors l Often related to congenital absence

Teeth – peg shaped Abnormally small Especially lateral incisors, 3rd molars

From Brothwell

Teeth – peg shaped Abnormally small Lateral incisors, 3rd molars Incisor example

From Brothwell

Teeth - Taurodontism
l In

molars l Pulp cavity enlarged, roots reduced l Neanderthals, other fossils l Occasionally in modern populations l Subtypes: cynodont, hypotaurodont, mesotaurodont, hypertaurodont (Bass, fig. 4-17a)

Teeth – taurodontism In molars Pulp cavity enlarged, roots reduced Mainly protohumans

From Brothwell

Teeth – Extra or Missing Roots
molar to 3rd molar is trend for roots to be less divergent, more fused l Similar trend in premolars (Bass)
l From 1st

Teeth – extra or missing roots From M1-M3 trend is for roots to be less divergent, more fused

From Brothwell

Teeth – Enamel Extensions, Pearls
l In

some molars, premolars l Extension of crown enamel may extend between roots l May terminate in enamel cluster: enamel pearl (may be obscured in alveolus) l In many modern groups (Bass, fig. 4-17b)

Teeth – enamel extensions, pearls In some molars, premolars Extension of crown enamel between roots

From Brothwell

Teeth – Occlusal Wear
l Mastication

(chewing): upper and lower arch teeth rub each other and any contained dietary 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

From Brothwell

Teeth – Occlusal Wear continued
l If

population rate of attrition is known, then amount of attrition can be used to help determine age of individual at death l Molars very useful: changes in cusp patterns with attrition allows staging and correlation with age at death (Bass)

Teeth – occlusal wear – if population rate of attrition is known, then amount of attrition can be used to help determine age of individual at death

From Brothwell

Teeth – Occlusal Wear continued
l Molar

attrition: varies with eruption times of molars (1st molars exposed to at least 12 years more wear than 3rd molars, and 6 years more wear than 2nd molars) (Bass; Bass, fig. 4-18)

Teeth – occlusal wear – molar attrition varies with time of molar eruption – 1st molars exposed to 12 years more wear than 3rd molars, and 6 more years than 2nd molars

From Brothwell

Teeth – Occlusal Wear continued
l Different

rates of attrition in different populations – age estimation from attrition in one population may be different from another l Within a group, there is individual variation in attrition – again, limits accuracy of aging (Bass)

Teeth – occlusal wear : different rates of attrition in different populations – age estimation from attrition in one population may be different from another; also individual variation within group – limits accuracy

From Brothwell

Teeth – Cultural Deformation
l Filed,

chipped, drilled, incised – decorative l Multiple different population groups l Mainly incisors: easier to work on, most visible to others l Interproximal grooves (especially molar): often associated with caries, alveolar abscesses - ? pain relief efforts (Bass)

Teeth – cultural deformation Filed, chipped, drilled, incised Mainly incisors – easier to work on, most visible to others

From Brothwell

Teeth – Dental Development
l Sequence

of calcification and eruption very useful in aging, particularly in young l Aging by 3rd molar development is of questionable accuracy (Bass) l See Bass, fig 4-22: eight stages of crown and root formation

Dental development Sequence of calcification and eruption very useful in aging, particularly in young

From Brothwell

Dental development Sequence of calcification and eruption very useful in aging, particularly in young

From Brothwell

Teeth - Occlusion
l Mongoloid:

frequent edge-edge occlusion l Caucasoids: usually slight overbite l Underbites uncommon in all groups

Types of dental occlusion patterns Caucasoids – usually slight overbite Mongoloids – frequent edge to edge occlusion

From Brothwell

Teeth – Sexual Dimorphism
§

Neither adult nor deciduous teeth have distinct dimorphic indicators § Male teeth may be larger than female teeth within a given population

END


								
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