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Oral Biology > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

Central face development begins at week ___

A

4

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2
Q

What happens in week 4 of orofacial development ?

A

Nasal placodes develop

Proliferation of ectomesenchyme on both sides of each placode results in medial and lateral nasal processes

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3
Q

The upper lip forms at week ___ - ___

A

6-7

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4
Q

The formation of the upper lip involves the primary palate and secondary palate. What fuses in each?

A

Primary palate - merging of the medial nasal process

Secondary palate - merging of the maxillary processes of the first pharyngeal arch

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5
Q

The secondary palate makes up ___% of the hard and soft palate

A

90

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6
Q

Developmental conditions can be ____, which means anomaly of development or hereditary/genetic. The two types of genetic conditions are ___ which means runs in families, or ___ which means present at birth

A

Developmental

Familial

Congenital

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7
Q

True or false… the palatal shelves are part of the maxillary processes

A

True

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8
Q

Cleft lip is due to defective fusion of the ___ process with the ____ process

A

Medial nasal

Maxillary

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9
Q

True or false… most cases of cleft lip are bilateral

A

False, 80% are unilateral

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10
Q

What conditions should be met in order to fix a cleft lip?

A

The infant should be 10 weeks, 10 lbs, and 10gm%/HM

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11
Q

Cleft palate failure of fusion of…

A

The palatal shelves

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12
Q

True or false… cleft lip is usually due to developmental issues, not genetic

A

True

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13
Q

The minimal manifestation of cleft palate is…

A

Bifid uvula

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14
Q

At what age do you treat a patient with cleft palate?

A

1.5 years

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15
Q

____ % of cases are CL+CP
____% of cases are only CP
____% of cases are only CL

A

45

30

25

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16
Q

____ % of syndromic patients have CL+CP

A

30%

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17
Q

____% of syndromic patients have cleft palate only

A

50

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18
Q

Name three symptoms of pierre robin sequence

A

Cleft palate

Mandibular micrognathia

Glossoptosis (downward displacement of tongue)

Note that pierre robin sequence is mostly developmental, not really genetic in nature

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19
Q

Name four non syndromic environmental factors that can lead to clefting

A

Maternal alcohol/cigarette use

Folic acid deficiency**

Corticosteroid use

Anticonvulsant therapy

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20
Q

Describe the lateral facial cleft

A

Lack of fusion of the maxillary and mandibular processes. Results in a hole in the cheek

Occurs in less than .5% of all facial clefts

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21
Q

Describe the oblique facial cleft.

A

Failure of fusion of the lateral nasal process with the maxillary process.

Can stretch from upper lip to eye

Patients with oblique facial clefts are usually associated with cleft palate

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22
Q

Describe the median cleft of the upper lip

A

Very rare

Failure of fusion of the medial nasal processes

Results in what looks like two noses

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23
Q

True or false… orofacial clefts are one of the most common major congential defects

A

True

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24
Q 
Describe the prevalence of orofacial clefting in the following populations...
Native americans
Asians
Caucasians
African americans
A

Native americans: 1/250
Asians: 1/300
Caucasians: 1/700
African Americans: 1/1500

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25
Q

True or false… cleft palate only is more common in males

A

False.. it is more common in females

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26
Q

True or false… CP + CL is more common in males

A

True

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27
Q

Describe what a submucous palatal cleft is

A

Soft palate is intact due to epithelium, but the underlying musculature is absent.

This results in a bluish midline discoloration (because it is fluid filled.. blue is reflected due to the depth (tyndall effect))

A bone notch will be present on the posterior portion of the hard palate margin

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28
Q

Where are commissural lip pits found? Are the associated with facial or palate clefting?

A

They are mucosal invagination at the corners of the mouth on the vermilion border

They are not associated with facial or palatal clefting

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29
Q

Which is involved with syndromes, paramedian or commissural lip pits?

A

Paramedian

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30
Q

What are paramedian lip pits?

A

Congenital invaginations of the lower lip. Usually bilateral.

There is no treatment for this

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31
Q

Which syndrome has great association with paramedian lip pits?

A

Van der woude syndrome

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32
Q

What syndrome is the most common form of syndromic clefting? Is it autosomal dominant or recessive?

A

Van der woude syndrome (2% of all CL + CP)

Dominant

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33
Q

What is the difference between microglossia and aglossia?

A

Microglossia - abnormally small tongue

Aglossia - entirely missing tongue

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34
Q

True or false.. microglossia is usually syndromic

A

True

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35
Q

What are some other issues that are often associated with microglossia?

A

Micrognathia

Lower incisors missing

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36
Q

What is ankyloglossia? How common is it? Is it more common in males or females? What is the treatment?

A

Tongue tied. Tongue has abnormally short, thick lingual frenum.

Prevalent in up to 4% neonate

4:1 M:F

No treatment required (can be asymptomatic or self-correcting). Frenotomy (cutting frenum) at age 4-5

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37
Q

During week ___ the thyroid bud normally descends from the apex of the _____ of the tongue (forming the ____) into the neck. ___% of ectopic thyroid are found between the base of the tongue and the epiglottis

A

7

Sulcus terminalis

Foramen cecum

90

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38
Q

What is the stafne defect?

A

AKA Lingual mandibular salivary gland depression.

Asymptomatic (no treatment required)

Located between the molars and the angle of the mandible

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39
Q

True or false… lingual thyroid is more common in females than in males

A

True. It is 7 times more common

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40
Q

True or false… most of the time, in a patient with lingual thyroid, the lingual thyroid is their only thyroid tissue

A

True. In 70% of patients

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41
Q

Lingual thyroid can cause symptoms such as ___, ___, and ____, and these symptoms arise during puberty, adolescence, pregnancy, or menopause

A

Dysphagia (difficulty swallowing) , dysphonia (hoarse voice), dyspnea (difficulty breathing)

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42
Q

True or false.. 1/3 of patients with lingual thyroid have hyperthyroidism, which results in lingual thyroid enlargement

A

False… 1/3 have HYPOthyroidism. The thyroid is enlarged to compensate for hypofunction

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43
Q

How is lingual thyroid usually diagnosed?

A

Thyroid scan with radioactive iodine

Biopsy is avoided to avoid risk of hemorrhage

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44
Q

Describe thyroglossal duct. ____% are diagnosed before age 20.

A

Develop from the epithelial remnants of the descending thyroid. Will always result in a swelling at or near the MIDLINE. Usually inferior to the hyoid bone.

50

1% of the time, it results in carcinoma

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45
Q

What is hemihyperplasia and what are some associated syndromes?

A

Rare developmental anomaly

Asymmetric overgrowth of one or more body parts

Beckwith-wiedemann syndrome, neurofibromatosis, proteus syndrome

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46
Q

What is crouzon syndrome (cranial dysostosis)

A

Characterized by craniosynostosis. (Brachyecephaly - short head. Scaphocephaly - boat shaped head)
Most severe cases demonstrate a cloverleaf skull (kleeblatt-schadel deformity).
Associated with ocular proptosis (underdeveloped maxilla)

Due to a mutation of the fibroblast growth factor receptor 2

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47
Q

What is apert syndrome (acrocephalocyndactyly)

A 
Ocular proptosis
Hypertelorism
Syndactyly
Mental retardation
Trapezoid shaped lips
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48
Q

What is tooth agenesis and cleidocranial dysplasia?

A

Tooth agenesis - failure of teeth to form

Cleidocranial dysplasia - third layer of teeth form

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49
Q

Developmental events are reiterated during ___

A

Repair

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50
Q

What week in development does tooth morphogenesis start?

A

5

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51
Q

All organs develop from ___ and ___ layers

A

Epithelium

Mesenchyme

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52
Q

What is intracrine signaling?

A

The signaling factor never leaves the cell but is able to affect the cell’s activity within the cell

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53
Q

Name some things that the neural crest cells form

A 
Ganglia
Adrenal medulla
Dentin
Pulp
Cementum
PDL 
Bones in face
Ectomesenchyme
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54
Q

What is ectomesenchyme?

A

Embryonic connective tissue

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55
Q

What structure will give rise to the dental lamina?

A

Primary epithelial band

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56
Q

What is the dental lamina?

A

Thickening of the oral epithelium in a band around the arches

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57
Q

Where is meckel’s cartilage in relation to the dental lamina?

A

Directly inferior

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58
Q

How does signaling from the dental lamina initiate tooth development?

A

The dental lamina signals the underlying mesenchyme to condense. The condensing mesenchyme signals adjacent mesenchyme to suppress tooth development genes. This ensures that tooth generation only occurs where it is supposed to

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59
Q

What causes the thickening of the dental lamina and underlying mesenchyme?

A

Cell proliferation

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60
Q

What are dental placodes

A

Specific portions in the dental lamina where the individual tooth actually forms

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61
Q

What signal is the dental lamina producing, and what signal is the underlying mesenchyme producing to begin tooth formation?

A

Dental lamina - LEF 1

Mesenchyme - MSX 1

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62
Q

What are the six stages in crown development?

A

Initiation-induction
Bud stage-proliferation
Cap stage-proliferation, differentiation, morphogenesis
Bell stage-proliferation, differentiation, morphogenesis
Apposition stage- induction and proliferation (laying down of dentin and enamel)
Maturation stage - maturation

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63
Q

What forms during the initiation stage of tooth development?

A

Lamina

Bud

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64
Q

What forms during the morphogenesis stage of tooth development?

A

Cap

Early bell

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65
Q

In which stage is tooth shape determined?

A

In the morphological stage which includes cap and early bell

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66
Q

During what structure does cell termination/differentiation occur?

A

Late bell

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67
Q

The condensed mesenchyme underlying the dental bud is called the _____

A

Condensed papilla mesenchyme

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68
Q

How many buds form in each arch along the dental lamina?

A

10 (10 primary teeth)

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69
Q

Each bud is the precursor of the ____ for each deciduous tooth

A

Enamel organ

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70
Q

During the bug stage, ___ acts along with ___, ____, and ____ to stimulate the mesenchyme to express ___, ____, ____, early growth response 1 (___), and the ECM molecules ____ and ____ and more ____

A

BMP
FGF-1
LEF-1
Shh

Msx-1
Msx-2
Egr-1
Pax-9

Syndecan
Tenascin
BMP-4

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71
Q

During the initiation stage, ____ stimulates the pre-dental ectoderm to produce ____, which in turn induces the underlying matrix to express ____ and ____ beneath the thickened dental lamina. ____ and ____ inhibit ____

A

Lef-1

Fgf-8

Pax-9 and Msx-1

BMP 2 and BMP 4 inhibit Fgf-8

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72
Q

What is the dental follicle?

A

Capsule that encases the developing tooth

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73
Q

The dental papilla is made up of ___ cells

A

Mesenchymal

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74
Q

During the ___ stage, ____ dental lamina branches off ____ which will form the permanent tooth

A

Cap

Successional

Lingually

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75
Q

_____ cells condense around the developing cap. These will become the dental papilla and dental ____

A

Ectomesenchyme

Sac (follicle)

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76
Q

What comprises the tooth germ?

A

Enamel organ

Dental papilla

Dental sac/follicle

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77
Q

The second primary molars have three permanent buds that run ___ to form ____

A

Posteriorly

The permanent molars

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78
Q

What is the epithelium called that connects the oral epithelium to the tooth germ?

A

Outer dental epithelium

Also called enamel epithelium

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79
Q

The ____ is the star shaped cell tissue located in the enamel organ. It is filled with liquid, separating the cells and sequestering growth factors

A

Stellate reticulum

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80
Q

What are enamel niches?

A

Cross sectioning artifacts found in the enamel organ

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81
Q

What is the enamel knot and what is its function?

A

Signaling center located in the enamel organ that determines how many cusps will form.

The influence of shape and number of cusps goes from epithelium to mesenchyme

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82
Q

What signaling factor is strongly expressed in the enamel knot?

A

Fgf-4

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83
Q

If you have two enamel knots in a tooth, how many cusps will form?

A

2.. it will be a premolar

84
Q

Does the enamel knot cause the underlying mesenchyme to increase proliferating or slow down proliferating?

A

Slow down. This causes it to form pointy cusps because everything else is proliferating faster

85
Q

Where is the stratum intermedium located?

A

Part of the enamel organ. It is condensed cells between the stellate reticulum and the inner enamel epithelium

86
Q

During the bell stage, the dental lamina connects the ___ to the ___. The enamel knot in this stage is better termed the ____

A

Tooth bell to the oral epithelium

Enamel cord

87
Q

The dental follicle is responsible for the formation of the entire ____

A

Periodontium

88
Q

During the bell stage, continued differentiation of what four distinct layers occurs?

A

Outer enamel epithelium

Stellate reticulum

Stratum intermedium

Inner enamel epithelium

89
Q

The cervical loop forms at the junction of the ___ and the ___ and will form the future ___

A

Outer enamel epithelium

Inner enamel epithelium

CEJ

90
Q

During the bell stage, the dental papilla cells continue to proliferate into the ___ cells and ___ cells

A

Outer dental papilla

Inner dental papilla

91
Q

True or false… during the bell stage, the dental sac/follicle cells develop into periodontal tissues

A

False… although they continue to proliferate, they develop into periodontal tissues in a later stage

92
Q

Describe the function of each…

Outer enamel epithelium
Stellate reticulum
Stratum intermedium
Inner enamel epithelium

A

Outer enamel epithelium - protective barrier for enamel organ.

Stellate reticulum - supports enamel production.

Stratum intermedium - supports enamel mineralization - alkaline phosphatase

Inner enamel epithelium - differentiate into ameloblasts

93
Q

What occurs during the apposition stage?

A

Stage during which organic matrix of enamel and dentin are laid down followed by initial calcification. Series of reciprocal inductions occur between enamel organ and dental papilla outer cells.

94
Q

Describe the events of reciprocal induction (part of the apposition stage) in their order.

A

Inner enamel epithelial cells differentiate into preameloblasts - cells become polarized

Preameloblasts induce the outer dental papilla cells to differentiate into preodontoblasts which secrete present in and will continue differentating into odontoblasts

95
Q

Why is it that the inner enamel epithelial cells change shape as they mature into preameloblasts and into ameloblasts?

A

They must grow lengthwise and move their nucleus to the opposite side to allow room for organelles for the production of enamel rods

96
Q

The mesenchymal cells of the dental papilla condensate against the basement membrane of the enamel organ. These cells are called ___; these cells become the ____.

A

Outer cells

Preodontoblasts

97
Q

As soon as predentin is secreted, the preameloblasts start laying down enamel. What is he difference between predentin and dentin?

A

Predentin is strictly organic; there is no mineral component

98
Q

Where would you find Tome’s process?

A

On the apical side of ameloblasts (side where enamel is being laid down)

99
Q

At what point in development do you call the dental papilla pulp?

A

After you see differentiation of the odontoblasts and separation from the ameloblasts

100
Q

Describe the apposition stage.

A

DEJ forms after disintegration of basement membrane

Odontoblasts retreat from the DEJ leaving odontoblastic processes within predentin.

Space containing process is a dentinal tubule

Ameloblasts retreat from the DEJ as enamel matrix is deposited

Reismless enamel is formed by early ameloblasts

Enamel rods are formed by tomes processes of late ameloblasts

101
Q

____ is secreted by odontoblasts and is strictly organic in nature. It induces differentiation of preameloblasts into ameloblasts

A

Predentin

102
Q

Upon induction, ameloblasts begin secreting enamel which ____ calcifies to ____% of full mineralization

A

Immediately

25

103
Q

Name three cell types that make up the dental follicle and what they give rise to.

A

Cementoblasts - cementum

Fibroblasts - PDL

Osteoblasts - alveolar bone

104
Q

Name what cells make up the dental papilla and what they give rise to

A

Odontoblasts - dentin

Undifferentiated mesenchymal cells, fibroblasts - pulp

105
Q

Name the seven stages of the ameloblast life cycle

A

Inner enamel epithelial cell

Preameloblast -cell reverses polarity

Initial secretory ameloblast - no tomes process - rodless enamel

Secretory ameloblast-tomes process - enamel rods

Smooth-ended maturation ameloblast-removal of protein and water

Ruffled-ended maturation ameloblast-introduction of inorganic material

Protective ameloblast - enamel cuticle

106
Q

Apposition and maturation of dentin and enamel occur in ____ from the ___ in a ___ direction

A

Increments/waves

Cusp tip

Cervical

(Think tree rings)

107
Q

During the maturation stage of enamel.. after deposition and initial mineralization of enamel, secretory ameloblasts lose…

A

Tomes processes

108
Q

What do maturation ameloblasts do?

A

Differentiate and remove enamel proteins and water, and pump additional calcium in the matrix

109
Q

In the maturation stage, the final differentiation of ameloblasts takes place into what type of ameloblast?

A

Protective ameloblast

110
Q

In the maturation stage… the enamel cuticle (a ____ type material) is secreted and ameloblasts attach to the enamel surface via ____. This will become the ____

A

Basal lamina

Hemidesmosomes

Epithelial attachment after eruption

111
Q

When does the reduced enamel epithelium form? What is it?

A

After the enamel is fully matured.

REE consists of outer enamel epithelium, stellate reticulum, stratum reticulum, and inner enamel epithelium.

112
Q

True or false… dentin mineralizes as it is deposited

A

True

113
Q

Initial mineralization of dentin is in the form of ____, producing ____

A

Globules

Globular dentin

The globules fuse together as mineralization proceeds

114
Q

What is mantle dentin?

A

Initial layer of dentin next to the DEJ

Collagen fibers perpendicular to DEJ

Higher mineral content

115
Q

What is the circumpulpal dentin?

A

Remaining dentin around pulp

Collagen fibers parallel to DEJ

Lower mineral content

116
Q

What is hertwig’s root sheath?

A

Structure that determines how roots are sized, shaped and numbered

Stimulates the outer enamel epithelium to become cementoblasts

117
Q

Reduced enamel epithelium grows in an ___ direction at the ____ and becomes the ____

A

Apical

Cervical loop

Hertwig’s epithelial root sheath

118
Q

Hertwig’s epithelial root sheath induces ___ outer cells to become ___. These cells secrete ____. HERS then detaches from root dentin and disintegrates. Some remnants persist and are called _____

A

Dental papilla

Hertwig’s epithelial root sheath

Predentin

Epithelial rests of malassez

119
Q

What do the epithelial rest cells of malassez help form?

A

PDL

120
Q

True or false… roots are not complete until after the tooth has erupted and is in function

A

True

121
Q

Describe the formation of cementum

A

Dental sac migrates in and contacts root dentin surface.

Dental sac cells are induced to differentiate into cementoblasts

Cementoblasts secrete organic matrix (cementoid) on new dentin surface

122
Q

Cementoblasts secrete an organic matrix called ___ on new dentin surface. The cementoid then ____ into cementum. This occurs in the apical 1/2 to 2/3 of the root. Cementoblasts become entrapped in lacunae to become ____

A

Cementoid

Mineralizes

Cementocytes

123
Q

True or false.. the newly formed PDL is highly organized

A

False.. it is not very organized until it is functioning

124
Q

In the PDL, fibroblasts are produced by differentiated ____

A

Ectomesenchyme cells

125
Q

What are fibroblasts role in the PDL formation?

A

They secrete collagen that anchor the cementum into bone as it is deposited

126
Q

Describe the formation of alveolar bone

A

Dental sac ectomesenchyme cells differentiate into osteoprogenitor cells, then osteoblasts lay down alveolar bone

Developing collagen fibers of the PDL become anchored in alveolar bone

127
Q

Roots are between ___ and ___ of the way formed by the time eruption begins

A

1/3rd and 2/3rds

128
Q

True or false… there is a primary pellicle that is formed over the enamel during the eruptive phase that protects the enamel, but it is soon destroyed

A

True

129
Q

Enamel is ___ in origin

A

Ectodermal

130
Q

True or false… enamel is nominal while dentin is vital

A

True.. dentin has odontoblasts processes in the dentin that make it vital

131
Q

What structure gives the enamel some flex so that it is not overly brittle?

A

DEJ

132
Q

Mature enamel is thicker at the ___ and thin at the ___

A

Crown (around 2.5mm)

Cervical line

133
Q

What percent of enamel is inorganic material, organic material, and water?

A

Inorganic - 96%
Organic - 1% (provides organization)
Water- 3%

134
Q

True or false.. the organic component of enamel is mostly composed of collagen

A

False!!! No collagen. NO COLLAGEN. NO COLLAGEN. NO. COLLOGEN

135
Q

What are the major enamel proteins in enamel?

A

Amelogenins, ameloblast is, enamelin, tuftelin, and others

136
Q

Each enamel rod traces the path of an ___ thus doesn’t run completely straight

A

Ameloblast

137
Q

True or false… rod and interrod enamel have different protein compositions

A

False. They are identical in their composition

138
Q

The main mineral component of enamel is ___ although a lot is actually ___

A

Hydroxyapatite

Carbonatoapatite

139
Q

Hydroxyapatite easily swaps out other minerals in its structure. True or false.. although some are anti caries, some are pro caries

A

True

Fluoride is anticavities

Magnesium makes teeth more vulnerable to acid attack

140
Q

What is the formula for hydroxyapatite?

A

Ca5(PO4)3(OH)X2

141
Q

In order to form carbonatoapatite, CO3 2- can substitute for both ___ and ___

A

PO4 3- (usually)

OH- (sometimes)

142
Q

___ and ___ is incorporated more in the inner enamel, while ___ is incorporated in the outer enamel. Which is more resilient in the face of acid attack?

A

Carbonate and magnesium

Fluoride

Outer enamel

143
Q

Due to the shape of each unit “cell” of hydroxyapatite, each crystal is somewhat ____ in shape

A

Hexagonal

144
Q

What are the dimensions of mature hydroxyapatite crystals?

A

60-70nm wide, 25-30nm thick

145
Q

True or false… enamel crystals are very long and may well run the entire length of enamel thickness (mm in length)

A

True

146
Q

Hexagonal symmetry ___ as crystals mature, and ___ their shape as they fully mature

A

Increases

Lose (somewhat)

147
Q

Describe enamel rods

A

Cylindrical accumulation of enamel crystals, lined up along the long axis of the rod.

Run perpendicular to the DEJ and radiate outwards

Rods are not completely straight, they curve somewhat as they progress towards surface (due to path of ameloblasts)

148
Q

True or false.. all rods run in the same direction

A

False.. although they are organized into rows, they run in alternating directions.

149
Q

True or false.. you can identify the orientation of enamel rods through light microscopy

A

False.. you must use SEM

150
Q

True or false.. ameloblasts directly produce the hydroxyapatite crystals

A

False.. they produce the proteins for a scaffolding for the crystals to form

151
Q

Describe rod sheaths

A

Is a relatively protein reach area of enamel that surround the rods, running about 3/4 of the way around each rod (for the most part separating rod and interrod enamel

152
Q

What occurs in the gaps of rod sheath?

A

Enamel crystals are continuous with the interrod enamel , linking the two together. While crystal orientation is mainly parallel to the long axis of rods: in the gaps, they bend outwards and become continuous with the interrod enamel

153
Q

Name two rod sheath proteins

A

Ameloblastins and amelogenins

154
Q

What portion of enamel do caries progress?

A

They penetrate through the higher protein rod sheath areas, thus between rod and interrod enamel.

155
Q

The initial deposition of enamel is only around ___% mineralized

A

30

156
Q

As enamel matures, ___ component decreases while ____ increases

A

Organic

Mineralization

157
Q

What are the three general phases to ameloblast maturation?

A

Pre-secretory - mature from pre-ameloblasts to ameloblasts

Secretory - deposition of enamel

Maturation - reduction of organic matrix, increase mineralization via ion transport

158
Q

Ameloblasts deposit organic matrix via ____ which exit the cell ___

A

Secretory vesicles

Apically

159
Q

True or false.. the basal lamina between the predentin and ameloblasts remains and becomes the DEJ

A

False. The basal lamina is broken down as it is penetrated by cell projections

160
Q

____ projects into the developing enamel and is a site of much secretory activity

A

Tome’s processes

161
Q

True or false… Initial enamel in apposition to dentin does not have a rod arrangement, it is uniform

A

True

162
Q

True or false… tome’s fibers are involved in the deposition of enamel

A

False. Tome’s processes are involved in the deposition of enamel, not fibers!

163
Q

The distal portion of tome’s process is towards the ___ while the proximal portion is towards the ___

A

Enamel

Stratum intermedium

164
Q

Describe the formation of interrod enamel by Tome’s processes

A

Interrod enamel is laid down first. A groove is formed within the interrod enamel to make room for the rods. Small gap around 3/4 of the process fills with organic material and forms the rod sheath

165
Q

What happens to ameloblasts after they have laid down their enamel?

A

Return to being a squat cell, much like a preameloblast

166
Q

Describe the formation of the reduced enamel epithelium

A

Loss of stellate reticulum and fusion of the outer enamel epithelium and the inner enamel epithelium give rise to the REE.

167
Q

Prior to eruption, enamel hardens and becomes highly mineralized… how? How long does this take?

A

Through the removal of water, organic material, and increased HA crystal diameter

Up to 5 years

168
Q

During the maturation phase of enamel, a unique basal lamina is formed at the external enamel surface. What is its function and what is it not made out of?

A

Helps regulate movement of fluid/material

Not made with collagen 4

169
Q

What is the process of modulation in regards to enamel maturation?

A

Process by which water and proteins are removed. Fluctuations in the distal membrane of ameloblast layers. “Ruffling and smoothing”

170
Q

What do ruffles cells do?

A

“Putting stuff in”

Infiltration and incorporation of calcium ions into crystals. Occurs during ruffling, lower pH favors mineralization. Secretes proteolytic enzymes

171
Q

What do smooth cells do?

A

“Letting stuff out”

Allow diffusion of protein fragments out of enamel, which leak in between cells and laterally defuse through cell layer. It does this by modifying gap junctions

172
Q

What is the fate of the enamel organ?

A

Enamel organ remnants fuse with the oral epithelium, forming a covering over the tooth

173
Q

Both the primary and secondary enamel cuticles comprise nasmynth’s membrane. What is the primary and secondary cuticle?

A

Primary enamel cuticle - a mineralized coating, which is the last secretory products of the ameloblasts

Secondary enamel cuticle - formed from remains of the reduced enamel epithelium fused with the oral epithelium and is removed due to mechanical forces

174
Q

Of the following receptors.. categorize each one as cell surface or intracellular.. Steroids, FGFR, TGF-B, retinoids, thyroid hormone

A

Cell surface: TGF-B, FGFR

Intracellular: steroids, retinoids, thyroid hormone

175
Q

True or false… the orientation of rods in relation to each other are straighter in the outer 1/3 of enamel compared to the inner 2/3rds

A

True

176
Q

Enamel formation is not simultaneous. What is one reason why the enamel is thicker coronally than cervically?

A

Tooth formation goes apically, thus as the crown grows, new ameloblasts are coming into play cervically

177
Q

Name three enamel proteins that are deposited during apposition

A

Ameloginins

Ameloblastin

Enamelin

178
Q

Name two enzymes that are involved in the organic component degradation during enamel maturation.

A

Enamelysin

Enamel matrix serine protease (kallikrein 4)

179
Q

What enamel proteins are involved in maturation of the basal lamina?

A

Amelotin

ODAM (odontogenic ameloblast associated protein)

180
Q

Describe Amelogenins

A

Main protein family in developing enamel (80-90%)

Only expressed when enamel is being produced, stops during maturation***

It restricts the HA crystal growth, preventing crystal fusion, and making them run the correct directions.

Loss of amelogenin function = no enamel rods

181
Q

Describe Ameloblastin

A

Around 10% of the enamel organic content.

Expressed all the way through to maturation.

Functions to adhere ameloblastins to developing enamel.

Loss of function causes the ameloblasts to ‘fall off’ = no enamel

182
Q

describe enamelin

A

Least abundant enamel protein (<5%), but largest in size

Only protein at the leading edge of enamel deposition.

Function is unknown but possible crystal elongation.

Loss of function = no enamel

183
Q

Describe enamelysin

A

This is an MMP involved in organic component degradation. Found during enamel deposition

Functions to chop up ameloblastin and enamelin. Critical for removal of these organic components for increased mineralization

Loss of function = thin immature enamel

184
Q

Describe enamel matrix serine protease

A

Secreted during modulation events of enamel maturation. Degrades amelogenins.

Loss of function leads to immature enamel

185
Q

What are included in the basal lamina proteins?

A

ODAM and Amelotin

No collagen IV!

186
Q

Name two functions of enamel acid etching

A

Provides better bonding surface by increasing the porosity of enamel to increase infiltration of bonding material. Also removes “crap” from the surface

187
Q

Why is it that enamel crystals dissolve best from the inside out and from the ends?

A

Carbonated apatite is mostly located in the center of the crystals. This is more vulnerable to acid attack.

The orientation of the crystals is important because it dissolves better when directly on the blunt end of a crystal

188
Q

What are the three different types of enamel etching patterns?

A

Type 1 - preferential removal of rods (most common because rods are typically facing you)

Type 2 - preferential removal of interrod enamel

Type 3 - irregular, indiscriminate pattern (least common)

189
Q

True or false… it is more harmful to remove enamel proteins than mineral because the mineral can regenerate while the proteins cannot

A

True

190
Q

Describe how age changes the enamel in regards to color, nature of surface layer, water content, brittleness, and permeability.

A

Color - staining, darker because its thinner

Nature of surface layer - changes due to ionic exchange with oral environment (fluoride)

Water content- decreases with age as crystals enlarge

Brittleness - increases as water is excluded

Permeability - decreases with age due to increases crystal size

191
Q

Explain how the age changes in enamel over time contribute to an overall decreased risk for caries

A

Increased fluoride content

Smoother surface of teeth = less area for biofilm to hide

Extrinsic factors - less refined carbohydrates consumed by adults

Danger time zone for caries is up to 20s. After that, perio is more of a problem

192
Q

Name the two periodic features of enamel

A

Striae of Retzius/perikymata

Cross striations

193
Q

Name the two optical features of enamel.

A

Hunter-schreger bands

Gnarled enamel

194
Q

Name the three histological features of enamel

A

Enamel tufts

Enamel lamellae

Enamel spindles

195
Q

Describe striae of retzius

A

“Rings on a tree”.

Appear as longitudinal lines running from the DEJ to enamel surface, marking weekly rhythm in enamel deposition

Each line has an increased organic content

196
Q

An accentuated striae (darker) called the _____ reflects physiological changes occurring during birth. These are found in all ____ teeth, and sometimes ____

A

Neonatal line

Primary

Cusps of first molars (because these teeth are starting to form around the time of birth)

197
Q

What are perikymata?

A

Surface manifestations of striae of retzius visible on the enamel surface

There are shallow furrows where the stria intersect on the surface.

198
Q

What direction do cross striations run? How far apart are they?

A

Perpendicular to the rod direction (parallel to the DEJ)

These are about 4 micrometers away from each other because enamel grows about 4 microns a day.

These show a day/night cycle of enamel deposition. Physiologic disturbances can leave more exaggerated cross sections

199
Q

Stria of retzius appear best in ____ sections

A

Longitudinal

200
Q

What are bands of Hunter-schreger?

A

Optical phenomenon due to scattering of light of rods running in an alternate direction.

Appear as alternating light/dark bands

Generally only extend from DEJ to 2/3 of enamel towards surface (outer 1/3rd is more straight)

201
Q

What is gnarled enamel?

A

Similar to bands of hunter-schereger, except they occur around the DEJ under cusps.

Due to complex twisting of rods as they approach cusp tips.

202
Q

What are enamel tufts?

A

Developmental feature caused by abrupt changes in enamel rod direction (crowding)

Project 1/3 to 1/2 of the way into enamel.

Contain more enamel proteins and are hypocalcified.

These give some ‘give’ to enamel, preventing fracture

203
Q

What are enamel lamellae?

A

Appear as ‘cracks’ that traverse the whole length of enamel

Contain proteins

Developmental area where enemy proteins are not removed, or remnants of the enamel organ

May give enamel more structural support

204
Q

What are enamel spindles?

A

Result from odontoblastic processes that traverse the DEJ and penetrate the enamel

Short distance into enamel

Since they are not enamel, and actually dentin, there are trace amounts of collagen

205
Q

True or false… ameloblasts are very susceptible to physiological changes

A

True

206
Q

Why is too much fluoride during tooth formation bad?

A

It can lead to fluorosis. Excess fluoride interferes with amelogenesis and makes hypermineralized enamel with a chalky white appearance with pits in teeth

Oral Biology (4 decks)

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