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HEB 1420 > Lecture 20 - Teeth and Mastication > Flashcards

Lecture 20 - Teeth and Mastication Flashcards

1
Q

Tooth Anatomy

A
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2
Q

Which tooth tissues comprise the crown?

A

-enamel, dentine, pulp

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3
Q

Which tooth tissues comprise the roots?

A

-cementum, dentine, pulp

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4
Q

Peridontal Ligament

A
  • anchors tooth in jaw
  • site of many nerves that sense pain, pressure
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5
Q

Tooth Anatomical Directions

A
  • mesial = medial
  • lingual = towards tongue (tongue side)
  • buccal = towards cheek (cheek side)
  • labial = towards lips (lip side)
  • occlusal surface = surface of teeth
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6
Q

What are the 4 types of human teeth?

A
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7
Q

What is the human dental formula?

A
  1. 1.2.3 per quadrant
    - 2 incisors, 1 canine, 2 premolars, 3 molars per quadrant
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8
Q

What is field theory?

A

-canines set up a field that demarcates what tooth grows there

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9
Q

Steps for growing a tooth

A
  1. Thickening of the oral epithelium above condensing mesenchyme (stem cells) below
  2. Epithelium invaginates into mesenchyme, tooth shape begins to develop
  3. Dental tissues start to develop
  4. Erupted tooth

*interaction b/w epithelium and mesenchyme: ectoderm gives rise to teeth (EMT)

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10
Q

What does the size of the teeth determine?

A

The number of teeth formed

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11
Q

What is the shape organizer?

A
  • enamel knot: located at the future tips of cusps
  • # enamel knots = # cusps
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12
Q

What two cells form hard tooth tissue?

A
  • odontoblasts: secrete dentine, creating a single dentine tubule (70% mineral) (1 step)
  • ameloblasts: secrete enamel matrix, creating a single enamel prism. then, hydroxyapetite crystals grow and encompass this matrix (96% mineral) (2 steps)
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13
Q

What is the EDJ?

A
  • odontoblasts and ameloblasts line either side of the enamel-dentine junction
  • each cell moves away from the EDJ (odontoblasts inward, ameloblasts outward) secreting their substances as they move
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14
Q

How can you tell how long it took a fossil to grow a tooth?

A

-ameloblasts and odontoblasts secretion pauses everyday (circadian rhythym), leaving marks in tissues

[daily: cross striations (enamel) vs von Ebner’s lines (dentine)]

[long term: retzius lines (enamel) vs Andresen’s lines (dentine)]

  • 1st molar formed at birth = birth line
  • count from birth line to determine how long it took tooth to grow (like tree rings)
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15
Q

Why do we want to determine how long it took fossils to grow teeth?

A
  • linked to overall development rates
  • slower development = larger brains, longer childhood, more complex social systems
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16
Q

Why are teeth called inside scales instead of outside bones?

A

-shark denticles (scale-like) gave rise to teeth

17
Q

Homodonty

A
  • one type of tooth
  • most fish and early tetrapods
  • single cusped teeth, good for catching prey
18
Q

Heterodonty

A
  • mammalian innovation
  • different types of teeth, some with multiple cusps

*multiple “mortars and pestles” to make digestion easier is more energy efficient

*heterodonty reduces overall energetic cost of eating

19
Q

Tribosphenic Molar

A
  • addition of a grinding wedge and surface
  • requires precision occlusion between upper/lower teeth
20
Q

Permanent Teeth

A
  • evolutionarily lost P1 and P2
  • 3rd molars = wisdom teeth
  • 32 teeth total (8 per quadrant)
21
Q

Incisors

A
  • single, blade like cusp
  • single root
22
Q

Canines

A
  • single, pointed cusp
  • single root
23
Q

Premolars

A
  • 2 cusps
  • single root
24
Q

Molars

A
  • 4-5 cusps
  • lower have 2 roots
  • upper have 3 roots
25
Q

Incision vs Mastication

A

Incision: biting, using incisors

  • opening stroke: protraction, depression
  • closing stroke: elevation

Mastication: chewing, using premolars and molars

-concentrates forces on one side

*canines have no use/function in humans

26
Q

How does diet relate to tooth shape and function?

A
  • grinding teeth: good for grinding brittle, stiff foods
  • shearing teeth: good for ductile (malleable) foods

*human/ape postcanines good for grinding brittle, stiff foods

27
Q

Diphyodonty

A
  • having baby and then adult teeth
  • deciduous human dental formula: 2.1.2

*no molars in babies, premolars look like molars

*20 baby teeth vs 32 adult teeth

-roots send signals for baby teeth to disintegrate, adult enamel pushes up

28
Q

Odontoclasts

A

-cells responsible for root resorption

29
Q

TMJ

A
  • temporomandibular joint
  • glenoid fossa ligments: sphenomandibular, lateral, TMJ capsule, stylomandibular, articular disc
30
Q

TMJ Movements

A

depression/elevation: TMJ rotation up and down

retraction/protraction: TMJ sliding anterior/posterior

Bennett Shift: medial-lateral shift

31
Q

What are the four masticatory muscles?

A
  • Temporalis
  • Masseter
  • Medial Pterygoid
  • Lateral Pterygoid
32
Q

Temporalis

A

Attachment: lateral crania, coronoid process

Action: elevates mandible

Innervation: CN V3

33
Q

Masseter

A

Attachment: zygomatic arch, ramus, mandibular angle

Actions: elevates mandible, protraction, medio-lateral shifts

Innervation: CN V3

34
Q

Medial Pterygoids

A

Attachments: sphenoid lateral pterygoid plate, ramus, mandibular angle

Actions: elevates mandible, protraction, medio-lateral shifts

Innervation: CN V3

35
Q

Medial-Lateral Movement

A

-requires activation of the masseter on one side and the medial pterygoid on the other side

36
Q

Lateral Pterygoid

A

Attachments: sphenoid lateral pterygoid plate, TMJ, neck of the condyle

Action: protraction

Innervation: CN V3

HEB 1420 (7 decks)

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