Dental Anthropology Exam II

What happens in the first 8 weeks in utero?

What happens in the first 8 weeks in utero?

Cell migration and differentiation, differentiation of all major structures (head, arms, mouth, etc.)

What happens to the fetus up until birth (8 weeks +)?

The development of all organs occurs (organogenesis) which stems from the Epithelium

Why are teeth considered epithelial appendages?

Teeth are considered epithelial appendages because they grow from the epithelium. Teeth form in the maxillary and mandibular arches of the fetus, forming in between the outer layer epithelium and the mesenchyme.

What is the pharyngeal arch and when does it form?

The pharyngeal arch is the fetus’ mouth and throat structures. The pharyngeal arch forms in the 4^th week of development. These mouth and throat structures are centered along the pharynx.

What are the two major features within the primary epithelial band?

The two major features are the dental lamina and the vestibular lamina. The dental lamina forms the teeth. The vestibular lamina forms the external opening to the oral cavity.

What are the Clone Model and Field Model?

These models illustrate theories on how different teeth structures develop (incisors, canines, etc.).

Describe the Clone Model.

in the dental lamina, at a location where a tooth is forming, the cells under this tooth know to become a molar. Once the cells differentiate into a molar, these cells pass this information along to another cell. This cell receives this information and differentiates into a molar, this molar cell passes information to another cell and that cell differentiates into a molar cell. The last molar cell stops sending signals for molar differentiation because the cell knows that there is a set number of molars.

Describe the Field Model.

this model follows compartmentalization. All the cells within a compartment already know what structure they are supposed to be. The genes tied to each compartment will instruct each cell what structure it will become.

What is the main difference between the Clone Model and the Field Model?

There is no cell-to-cell communication in the Field Model, whereas the entire Clone Model relies on cell-to-cell communication.

Know which tooth types belong to each compartment: Incisiform, Caniniform, and Molariform

Incisiform (red): the compartment where incisors form

Caniniform (yellow): the compartment where canines form

Molariform (green): the compartment where molars form

Know the general developmental sequence. (from Dental Lamina to Eruption)

Dental lamina, placode, bud, cap, bell, eruption

Epithelial band, dental lamina, ectoderm, mesenchyme, bud, cap, bell, late bell, crown/eruption

Placode Stage – First signaling center

The placode is a dense ectodermcell formation.

The placode is where signaling for tooth development occurs.

The placode lies inside the oral epithelium and above the mesenchyme.

Bud Stage - Cell formation

This is the first stage where tooth development occurs. The epithelium (outer layer) burrows into the mesenchyme (inner layer). The mesenchyme cells condense around the bottom of the ‘bud’. Epithelial cells remain functioning as epithelial cells; do not change in shape or function.

Cap Stage - Cell Specialization

Cells start to change shape and function. The structure becomes more tooth-like. The cap forms, composed of the dental organ, tooth germ, and enamel organ. The dental papilla forms (round portion which eventually becomes dentin and pulp). The cap formation is atop the dental papilla, which is the early development of the enamel/crown. The dental follicle coats the entire structure (cap formation and dental papilla).

Bell Stage - Crown Forms

The enamel organ forms a bell shape while the bottom of the epithelial cap deepens. Morphodifferentiation occurs; crown assumes final 3D shape. Ameloblasts produce enamel. Odontoblasts produce dentin.

Epithelium

“outer layer”, this is where teeth structures form from. All organogenesis forms from the epithelium.

Forms 37 days into development.

Tooth germ

Forms in the “Cap Stage”.

Tooth germ is composed of the (C) dental follicle, (B) dental papilla, and (A)enamel organ.

This cell differentiates specific structures; tooth germ cells specialize into new cells (enamel, dentin, pulp, etc.).

Morphogenesis

A series of developmental stages producing new sets of genes which control new functions. Molecular signals that control cell growth, migration, and cell fate/differentiation.

Enamel Knot

Only occurs on the molars.

Forms in “Cap Stage”.

Clusters of non-dividing epithelial cells visible in section of molar cap stage tooth germs. Enamel knots organize for the formation of cusps in the molariform compartment.

Tooth germ

Forms in the “Cap Stage”.

Tooth germ is composed of the dental follicle, dental papilla, and enamel organ.

This cell differentiates specific structures; tooth germ cells specialize into new cells (enamel, dentin, pulp, etc.).

Dental Follicle

Forms during “Bell Stage”.

A hard dental sac that is not erupted from the epithelium.

Cementoblasts form (create cementin).

Osteoblasts form (cells that create alveolar bone; tooth sockets).

Fibroblasts form (cells that create Sharpey’s fibers).

Hertwig’s Epithelial Root Sheath

Forms during “Bell Stage”. Crowns fully form when the Epithelial Rooth Sheath forms.

Heritability

Phenotypic variation within a population (genetic influences).

Genotype vs Phenotype

Genotype is genetic makeup, whereas phenotype is observable traits

Phenomics

Research on genetics

Dental Phenomics

Goal: to bridge to gap between the genotype and the phenotype of teeth

Dental Phenomics try to understand the molecular processes that occur for teeth to form.

How does genotype become a phenotype in the body?

Epigenetics

How behavior and the environment can cause changes that affect the way the genes work; genotype does NOT DETERMINE phenotype

Genetic code vs Epigenetic code

Epigenetic code controls gene expression. Epigenetics can modify how genes are expressed by choosing what to turn on/off based on environmental condition

What controls epigenetics?

Epigenetic code changes are caused by environmental stimuli; thus, the organism can adapt to different environments

Why are twin and family studies useful for understanding epigenetics?

Twins have the same genotype, but epigenetic codes can differ. Families have predictable transmission of genes (inheritance). Twin and family studies can help isolate genes that may be responsible for certain traits.

What do the Lim-homeobox genes do? (Lhx-6 and Lhx-7)

Lim-homeobox genes are responsible for initializing tooth development. If a person is missing Lhx genes then teeth will not form at all.

What is the Pax-9 gene responsible for?

Pax-9 is responsible for the location of tooth germs.

What does the Sonic the Hedgehog Gene control? What happens if it is missing or mutated?

SHG is released by the primary enamel knot. SHG is a signaling molecule. T

he SHG is responsible for the location of facial appendages (nose, etc.).

SHG is responsible for giving the positional information for enamel cusps and regulating cusp growth.

If SHG is absent, fetus will die & have condition holoprosencephaly (facial appendages mutated and in the wrong place).

If SHG is mutated, a person will have small incisors and molars.

Why is Amelogenin different for males and females?

Amelogenin is an enamel formation protein controlled by AMGX or AMGY (based on sex chromosomes: Y for male & X for female).

Amelogenin is the largest and most important protein released during enamel secretion

Which part of the tooth forms first? Last?

Crown forms first starting at the cusp tip to the CEJ.

The root forms last starting at the EDJ ending at the Root Apex.

Intrauterine tooth formation; this process begins when baby is in utero. Beginnings of dental development take place in fertilization to birth; roughly 34 - 42 weeks.

Which teeth are the first to form (14-19 weeks in utero)? (hint: anterior = front to back)?

Anterior

Deciduous Central Incisors, Deciduous Lateral Incisors, & Deciduous Canines.

Initiates Mesial & Distal shoulders=Incisors & Cone=Canines

Which teeth are the next to form (15-32 weeks in utero)? (hint: posterior = front to back)

Posterior

Deciduous 1st Molars, Deciduous 2nd Molars, & Permanent 1st Molar

Molar Cusp Formation MB, ML, DB, DL, Distal

What is the first permanent (adult) tooth to form and when?

Permanent first molar forms 15-32 weeks in utero

How many teeth are in occlusion at birth (*typically)?

Tends to be no teeth in occlusion; not true for everyone, esp. if infant has genetic markers or if infant is a late term birth.

What teeth are the first to start formation after birth (3-4 months, then 4-5 months)?

Permanent incisors: 3 – 4 months (postnatal); central first, lateral follows

Permanent canines: 4 – 5 months; forms early than other because it has a taller crown

What teeth are forming between years 2 and 3?

Permanent Premolars and Second Molars form between years 2 & 3.

Root development: 2 ~ 4 years

What are the possible differences in formation timing of teeth in humans? Do any of these factors result in large variation in timing?

Differences in formation timing of human teeth can be caused by sex, ancestry, and generation.

None of these factors result in a huge variation in timing.

For sex, females may develop earlier than males due to amelogenin AMGX.

For ancestry, some ancestries may have variable development timings.

For generation, modern and ancient human populations likely have different development timings (possible caused by nutrition). Modern generations have more access to nutrients than ancestral populations.

Moorrees (1963)

A tooth aging method based on development. Established in 1963, comprised of 14 developmental stages (crown, root, apex), MFH was discovered using x-rays at 6-month intervals. This is an OUTDATED method. The Smith MFH (most updated version)

Demirjian

A tooth aging method which uses stages A – H2 based on dental maturity, score 0-100 and match up score to age rage, VERY time consuming but doable.

Gustafson and Koch (1974)

A tooth aging method which gathered data from multiple studies, this method does a better job at illustrating the variability of tooth development, method claims to be as accurate as 2 months within the actual age.

Is the third molar a reliable way to age someone?

The third molar aka the wisdom tooth is a reliable way to age teenagers and early adults. Research on this method is ongoing.  Table 5.6 in the textbook.

What is the difference between alveolar and gingival emergence?

Alveolar emergence is when the tooth emerges from the alveolar bone (tooth socket), Gingival emergence is when the tooth emerges from the gums.

What is exfoliation?

Exfoliation is tooth loss.

Why is the Ubelaker tooth chart most widely used?

The Ubelaker tooth chart is the first aging method developed by an anthropologist. The method follows a snapshot in time of the teeth; this is a common and most accessible method.

BUT this method was developed using a population of skeletons of pre-historic Native American children, thus the ancestry and generation may affect tooth development, for example compared to modern American children.

Why is the AlQahtani London Atlas better?

Dr. AlQahtani is a Dentist & Anthropologist. AlQahtani developed this atlas which could be described as the most comprehensive and accurate tooth aging methods. AlQahtani used a large amount of modern data to support his findings; this is the BEST aging method.

The AlQahtani method is better than the Ubelaker method because it is based on a large amount of modern data.

Be able to read the AlQahtani London Atlas and provide an age estimate based on a written description of the developing teeth.

What is the broadest definition/purpose of teeth?

Teeth are hardened structures which main purpose is to break down food. Natural selection [selective pressures] influenced the type of tooth structures and whether or not an organism had teeth.        

Why is it important to look for homologies in dental evolution?

Teeth homologies can indicate whether organisms share an ancient ancestor or not. Homology indicates shared ancestry but structures do not have the same function.  Watch out for convergent evolution.

What is the Outside-In Hypothesis?

Ex: Shark skin has dermal denticles [tooth-like structures on skin]

Outside-In Hypothesis states that our earliest ancestors had dermal denticles, and at some point those tooth structures moved into our mouths and evolved into our teeth

What is the Inside-Out Hypothesis?

Ex: Pharyngeal denticles: throat teeth [eels, turtles, etc.]

The Inside-out Hypothesis states, if throat teeth happened first, throat teeth migrated from the throat into our mouths.

What is the Inside and Out Model?

The Inside and Out Model assumes that both (Outside-In and Inside-out) theories are partially true. Teeth and dermal denticles come from the same basic structures (genes). Dermal denticles form similarly to how modern human teeth form to an extent.

What characteristics did the earliest teeth share?

Earliest teeth were hardened tooth caps made from enameloid, there was no dentin or pulp chamber. Early teeth had no complex structures or heterodontia (different tooth structures). Early teeth were anchored in the mouth and constantly grew (not just 2 generations).

What is heterodontia? How is it related to mammalian teeth?

Heterodontia refers to different tooth structures that play different roles. Mammalian teeth illustrate dental division of labor, meaning the different teeth structures were designed to perform different tasks. Early mammals were able to eat different things

How did diphyodonty, horizontal chewing, and prismatic enamel differentiate mammals from other creatures?

Early mammals had a jaw joint that allowed for horizontal chewing motions. Early mammals had diphyodonty (2 generations of teeth) and prismatic enamel (developed enamel in prism form). Early mammals had more complex tooth and jaw structures compared to other organisms of that time and earlier.

What are tribosphenic molars?

Tribosphenic molars are a trait of early mammals, these molars have 6 cusps: 3 from cutting and 3 for crushing. This structure is used for different tasks. Tribosphenic molars are a great example of tooth structure evolution, since ancient organisms lacked advanced tooth structures. Due to independent evolutionary paths, mammals have different teeth structures (rabbits, humans, cows, etc.).

What is the dental formula of the primate common ancestor?

Dental Formula = 3143: 3 incisors, 1 canine, 4 premolars, 3 molars

What is the dental formula of Prosimians and New World Monkeys?

Dental Formula = 2133: 2 incisors, 1 canine, 3 premolars, 3 molars

What is the dental formula of Old World Monkeys and Apes?

Dental Formula = 2123: 2 incisors, 1 canine, 2 premolars, 3 molars

What is the dental formula for humans? What organisms share the same dental formula?

Dental Formula = 2123: 2 incisors, 1 canine, 2 premolars, 3 molars

Apes and Old World Monkeys have the same dental formula.

Why do humans have “P3” and “P4” premolars?

Humans have “P3” and “P4” molars according to mammalian dentition, because the “P1” and “P2” molars were lost in evolution. Humans have “P1” and “P2” molar genotypes but do not express the phenotypes.

Know the general dental traits of frugivores, folivores, insectivores, and omnivores.

Frugivores: fruit & seed eaters, have low rounded cusps (bunodont) & crenulations (folds w/in the molar to GRIND SEEDS)

Folivores: grass & leave eaters (cow-like), have higher cusp profile for grinding dense plant fibers

Insectivores: insect eaters (smaller primates), have sharp cusps

Omnivores: eat everything, general morphology (teeth not too sharp; teeth not too dull)

What is the overall dental trend of hominins (from the earliest hominins like Ardipithecus to modern humans)?

Head-to-teeth proportions changed over time; primates had small skulls and big teeth (megadontia) and humans have a larger skull and small teeth. Canines shrank over time. Primates had larger and less structured teeth, humans have smaller and more structured teeth.

Why are teeth a great way to study changes in hominins over time?

Hominin dentition is highly heritable, an indication of biological relatedness. Thus, changes in teeth indicate changes in hominins over time. For instance, as teeth shrank hominins likely indulged in different food sources

What are the three dental features for Neandertals?

1) Beveled wear on incisors; WORN at an angle

2) Retromolar gap: gap after the molars, early homo sapiens did not have that gap

3) Taurodont molar roots: roots are combined NOT fused, creating a large pulp chambers

The Dental arcade and dental structures for Neanderthals are larger than that of modern humans

What kinds of variations can you find using tooth measurements?

Sexual dimorphism and genetic variation

What tool is used to measure teeth?

The Caliper is used to measure teeth; the Hilson Caliper is the best way to measure teeth that are still in a socket.

Mesiodistal dimensions

Mesial to distal measurements, there can be a variety of placements. WIDEST POINT - CEJ – APEX. Decide where you want to measure, then measure all the teeth accordingly.

Buccolingual dimensions

Buccal to lingual measurements. Taking CDJ measurements would be more difficult; to get around measurement distortions created by the crown

Crown height dimensions

Cervix-occlusal measurements

Clinical crown heights

how much of the tooth is exposed

Anatomical crown heights

how much of the crown is exposed

Root Length

root tip to CEJ?

Elliptical Fourier Analysis (EFA)

Uses computers, take a picture of a tooth (any side; multiple sides) —> outline the dimensions of the tooth

—> gives volume of the surface as well as the metrics

Know the major dental measurements

Mesiodistal dimensions

Buccolingual dimensions

Crown height dimensions

Clinical crown heights

Anatomical crown heights

Root length

Elliptical Fourier Analysis (EFA)

What is interobserver and intraobserver error?

Interobserver error: difference between levels of experience between researchers, different measurement placements between researchers, error must be within 0.01 mm.

Intraobserver error: experience of a single researcher (how well the researcher can make accurate placed measurements [consistency of accurate measurements])

How can interproximal wear and attrition affect dental measurements?

Interproximal wear can cause the reduction (wear) of mesial/distal surfaces, thus mesiodistal measurements may be smaller compared to the rest of the population

Attrition occurs when the maxillary & mandibular teeth rub against another, wearing down crowns flattening the bite & occlusal surfaces. Attrition will shorten crown height dimensions.

What does the Crown Module tell you about a tooth?

Crown Module equation: (MD diameter + BL diameter) / 2 =

The Crown Module is indicative of the average crown dimensions.

The Crown module can be used to compare crown dimensions between populations.

Crown modules DISREGARD shape.

What does the Crown Index tell you about a tooth?

Crown Index equation: (100 x BL diameter) / MD diameter =

MD Longer teeth = small crown index #

What does the Robustness Index tell you about a tooth?

Robustness Index equation: MD diameter x BL diameter =

RI demonstrates the overall tooth size.

Summary Tooth Size: sum of the robustness indices for all tooth classes / # of tooth classes

Can teeth be used to distinguish between races?

No, biological race does not impact teeth phenotypes. Teeth can be used to determine biodistance.

What are clines and why are they used to think about the distribution of phenotypic traits?

Clines: a geographic gradation of phenotypic traits; tooth variation distributes geographically; no hard line thus there can be shared tooth variations

Clines use geography to indicate where specific tooth variations can be found.

What is ASUDAS? What are some of the reasons why it is better than earlier versions?

ASUDAS is the Arizona State University Dental Anthropology System. This system is comprised of plaques with descriptions of traits. ASUDAS is universally used. ASUDAS features traits that are easily identified, less susceptible to crown wear, low/no sexual dimorphism, and are highly heritable. The ASUDAS has all the tooth types.

Why do we no longer use “Sinodont”, “Eurodont”, and “Afridont”?

These groupings are no longer used because all of these supposedly “location specific”  features have been found in ALL populations across the globe.

These groupings indicate that a large percent of a specific location’s population could have these features.

What is Biodistance Analysis

Biodistance analysis is the best way to determine global tooth variation. Biodistance is an indicator of hominin relationships.

Why is collecting data on non-metric traits so difficult?

Collecting data on non-metric traits is very difficult due to high error rates based on experience levels, familiarity with teeth is crucial, inter/intraobserver error is high, and scores change over time.

Know how non-metric traits can be used to look for variation/relationships in hominins, global populations, regional populations, local populations, and individuals.

Non-metric traits can be used to determine hominin relationships, global variations, intraregional variation, intracemetery variation (cemetery population/living people), and individual level variation (compare individual to another individual).

a.      Shoveling (incisors)

-          Central & lateral incisors that have enamel that curves around the mesial-distal surface; giving the tooth a curved appearance

-          Anthropologists used to think shoveling indicated Native American ancestry

-          0-6

-          Shovel shaped incisors have flat lingual surfaces

b.      Cingulum (MAX 1 & C) – Talon Cusp

-          Overpronounced cingulum

-          Specific to certain teeth

c.       UTO- Aztecan Upper Premolar

-          Cheek side of upper premolar

-          No bilateral symmetry

-          Aztecan: people who historically spoke Aztecan language are likely to have an upper premolar

d.      Distal Accessory Ridge – Maxillary Canines

-          Extra ridge of tooth (this can be observed from the occlusal-lingual surfaces)

-          Commonly scored across global populations

-          Easy to find; easy to score

-          Not tied to any specific region

e.       Carabelli’s Cusp – Maxillary Molars

-          Large or small

-          Common in people who originate from certain parts of Eastern Europe and Western Asia

-          Extra cusp on the lingual surface of the maxillary molars

f.        Parastyle of Upper Molars

-          Similar to an extra cusp; looks like a Carabelli’s cusp à but the enamel of the parastyle is not fully connected to the molar

-          A hard extra piece of enamel

-          Can be found on any surface

g.      Groove and Fissure Patterns

-          Grooves: hard lines

-          Fissures: pattern created by cusps

-          Y Fissure, + Fissure, X Fissure

-          Score Fissures: A – D (A is harsh crease and deep – D is shallow)

-          Heritable traits

a.      Deflecting Wrinkle

-          Fold in the distal side of the ML cusps of permanent 1^st molars and deciduous 2^nd molars

-          Not common

b.      Prostylid of Lower Molars

-          Extra cusp

c.       Taurodontism

-          A-B: roots appear to be fused together, but the pulp chamber is open and very large

Not common

What is hydroxyapatite?

Hydroxyapatite is what teeth are made out of [enamel, dentin, etc.]. The hydroxyapatite formula is Ca10(PO4)6(OH)2.

How can minerals change the color of teeth?

Minerals are able to stain teeth in taxphonomic processes (time period of death until discovery).

Ground water minerals can cause staining and color changing in teeth and bone

Calcite: stains cementum and dentin brownish-red

Vivianite: stains teeth and bone blue/purple (also dental tissues)

Copper: stains teeth and bone green

What affect can high level of fluorine have on teeth? What part of hydroxyapatite can be substituted by elements like fluoride?

Too much fluorine can cause dental fluorosis. Fluorine can be found in water and food sources. Dental fluorosis causes teeth opacities and pitting. When you drink fluorine it is introduced into the bloodstream and makes its way into the enamel. Fluorine in teeth can be used in dating techniques.

The hydroxides (OH-) in hydroxyapatite can be substituted by fluorine.

How can dentin be used to study diet?

Studying the amount of carbon and nitrogen in dentin can determine an organism’s diet.

How can enamel be used to study diet and migration?

By studying the hydroxyapatite in the enamel, traces of strontium, lead, phosphate, oxygen, carbon/ate, can indicate what the organism’s diet and migration was like.

How can the Carbon-13 of teeth be used to study diet?

Carbon-13 is the stable form of the carbon isotope. Photosynthetic pathways create the carbon in the hydroxyapatite. In C3 plants (shrubs and trees, adapted to cool environment), carbon-13 travels through food chain. In C4 plants (grasses and corn, in tropical/subtropical regions), carbon-13 traveled through the food chain. In modern society, humans get carbon-13 from a mix of C3 and C4 plants. However, in the past C3 and C4 plants indicated diet and possible demographic/graphic location for humans.

How can Carbon-14 of teeth be used to figure out how old a tooth is?

Carbon-14 is the radioactive, unstable carbon isotope. Carbon-14 will radioactive decay, thus it is not good for determining old diets.

How does carbon-14 end up in teeth? Carbon-14 is consumed during childhood à carbon-14 introduced into teeth (enamel & dentin) à carbon begins to decay at a predictable rate

The molar is used in the Carbon-14 dating process because of its large surface area and large amount of enamel & dentin. Cut the root of the molar, remove enamel from the dentin, pulverize enamel & dentin into powder, lastly these materials are tested separately. A mass spectrometer measures the Carbon-14 in the enamel and dentin samples and gives a range of time for the formation year.

 Note: Atomic bomb changed how much Carbon-14 is inside modern humans

What is forensic odontology?

Forensic odontology is the examination and evaluation of dental evidence and remains.

What are some of the situations where dental identification would be useful?

Some situations include, to identify unidentified remains, trauma identification, age estimation, mass fatalities, or to confirm suspect.