Exam 2 Flashcards
(206 cards)
1
Q
Central face development begins at week ___
A
4
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
3
Q
The upper lip forms at week ___ - ___
A
6-7
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
5
Q
The secondary palate makes up ___% of the hard and soft palate
A
90
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
7
Q
True or false… the palatal shelves are part of the maxillary processes
A
True
8
Q
Cleft lip is due to defective fusion of the ___ process with the ____ process
A
Medial nasal
Maxillary
9
Q
True or false… most cases of cleft lip are bilateral
A
False, 80% are unilateral
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
11
Q
Cleft palate failure of fusion of…
A
The palatal shelves
12
Q
True or false… cleft lip is usually due to developmental issues, not genetic
A
True
13
Q
The minimal manifestation of cleft palate is…
A
Bifid uvula
14
Q
At what age do you treat a patient with cleft palate?
A
1.5 years
15
Q
____ % of cases are CL+CP
____% of cases are only CP
____% of cases are only CL
A
45
30
25
16
Q
____ % of syndromic patients have CL+CP
A
30%
17
Q
____% of syndromic patients have cleft palate only
A
50
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
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
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
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
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
23
Q
True or false… orofacial clefts are one of the most common major congential defects
A
True
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
25
True or false... cleft palate only is more common in males
False.. it is more common in females
26
True or false... CP + CL is more common in males
True
27
Describe what a submucous palatal cleft is
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
28
Where are commissural lip pits found? Are the associated with facial or palate clefting?
They are mucosal invagination at the corners of the mouth on the vermilion border
They are not associated with facial or palatal clefting
29
Which is involved with syndromes, paramedian or commissural lip pits?
Paramedian
30
What are paramedian lip pits?
Congenital invaginations of the lower lip. Usually bilateral.
There is no treatment for this
31
Which syndrome has great association with paramedian lip pits?
Van der woude syndrome
32
What syndrome is the most common form of syndromic clefting? Is it autosomal dominant or recessive?
Van der woude syndrome (2% of all CL + CP)
Dominant
33
What is the difference between microglossia and aglossia?
Microglossia - abnormally small tongue
Aglossia - entirely missing tongue
34
True or false.. microglossia is usually syndromic
True
35
What are some other issues that are often associated with microglossia?
Micrognathia
Lower incisors missing
36
What is ankyloglossia? How common is it? Is it more common in males or females? What is the treatment?
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
37
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
7
Sulcus terminalis
Foramen cecum
90
38
What is the stafne defect?
AKA Lingual mandibular salivary gland depression.
Asymptomatic (no treatment required)
Located between the molars and the angle of the mandible
39
True or false... lingual thyroid is more common in females than in males
True. It is 7 times more common
40
True or false... most of the time, in a patient with lingual thyroid, the lingual thyroid is their only thyroid tissue
True. In 70% of patients
41
Lingual thyroid can cause symptoms such as ___, ___, and ____, and these symptoms arise during puberty, adolescence, pregnancy, or menopause
Dysphagia (difficulty swallowing) , dysphonia (hoarse voice), dyspnea (difficulty breathing)
42
True or false.. 1/3 of patients with lingual thyroid have hyperthyroidism, which results in lingual thyroid enlargement
False... 1/3 have HYPOthyroidism. The thyroid is enlarged to compensate for hypofunction
43
How is lingual thyroid usually diagnosed?
Thyroid scan with radioactive iodine
Biopsy is avoided to avoid risk of hemorrhage
44
Describe thyroglossal duct. ____% are diagnosed before age 20.
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
45
What is hemihyperplasia and what are some associated syndromes?
Rare developmental anomaly
Asymmetric overgrowth of one or more body parts
Beckwith-wiedemann syndrome, neurofibromatosis, proteus syndrome
46
What is crouzon syndrome (cranial dysostosis)
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
47
What is apert syndrome (acrocephalocyndactyly)
```
Ocular proptosis
Hypertelorism
Syndactyly
Mental retardation
Trapezoid shaped lips
```
48
What is tooth agenesis and cleidocranial dysplasia?
Tooth agenesis - failure of teeth to form
Cleidocranial dysplasia - third layer of teeth form
49
Developmental events are reiterated during ___
Repair
50
What week in development does tooth morphogenesis start?
5
51
All organs develop from ___ and ___ layers
Epithelium
Mesenchyme
52
What is intracrine signaling?
The signaling factor never leaves the cell but is able to affect the cell's activity within the cell
53
Name some things that the neural crest cells form
```
Ganglia
Adrenal medulla
Dentin
Pulp
Cementum
PDL
Bones in face
Ectomesenchyme
```
54
What is ectomesenchyme?
Embryonic connective tissue
55
What structure will give rise to the dental lamina?
Primary epithelial band
56
What is the dental lamina?
Thickening of the oral epithelium in a band around the arches
57
Where is meckel's cartilage in relation to the dental lamina?
Directly inferior
58
How does signaling from the dental lamina initiate tooth development?
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
59
What causes the thickening of the dental lamina and underlying mesenchyme?
Cell proliferation
60
What are dental placodes
Specific portions in the dental lamina where the individual tooth actually forms
61
What signal is the dental lamina producing, and what signal is the underlying mesenchyme producing to begin tooth formation?
Dental lamina - LEF 1
Mesenchyme - MSX 1
62
What are the six stages in crown development?
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
63
What forms during the initiation stage of tooth development?
Lamina
Bud
64
What forms during the morphogenesis stage of tooth development?
Cap
Early bell
65
In which stage is tooth shape determined?
In the morphological stage which includes cap and early bell
66
During what structure does cell termination/differentiation occur?
Late bell
67
The condensed mesenchyme underlying the dental bud is called the _____
Condensed papilla mesenchyme
68
How many buds form in each arch along the dental lamina?
10 (10 primary teeth)
69
Each bud is the precursor of the ____ for each deciduous tooth
Enamel organ
70
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 ____
BMP
FGF-1
LEF-1
Shh
Msx-1
Msx-2
Egr-1
Pax-9
Syndecan
Tenascin
BMP-4
71
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 ____
Lef-1
Fgf-8
Pax-9 and Msx-1
BMP 2 and BMP 4 inhibit Fgf-8
72
What is the dental follicle?
Capsule that encases the developing tooth
73
The dental papilla is made up of ___ cells
Mesenchymal
74
During the ___ stage, ____ dental lamina branches off ____ which will form the permanent tooth
Cap
Successional
Lingually
75
_____ cells condense around the developing cap. These will become the dental papilla and dental ____
Ectomesenchyme
Sac (follicle)
76
What comprises the tooth germ?
Enamel organ
Dental papilla
Dental sac/follicle
77
The second primary molars have three permanent buds that run ___ to form ____
Posteriorly
The permanent molars
78
What is the epithelium called that connects the oral epithelium to the tooth germ?
Outer dental epithelium
| Also called enamel epithelium
79
The ____ is the star shaped cell tissue located in the enamel organ. It is filled with liquid, separating the cells and sequestering growth factors
Stellate reticulum
80
What are enamel niches?
Cross sectioning artifacts found in the enamel organ
81
What is the enamel knot and what is its function?
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
82
What signaling factor is strongly expressed in the enamel knot?
Fgf-4
83
If you have two enamel knots in a tooth, how many cusps will form?
2.. it will be a premolar
84
Does the enamel knot cause the underlying mesenchyme to increase proliferating or slow down proliferating?
Slow down. This causes it to form pointy cusps because everything else is proliferating faster
85
Where is the stratum intermedium located?
Part of the enamel organ. It is condensed cells between the stellate reticulum and the inner enamel epithelium
86
During the bell stage, the dental lamina connects the ___ to the ___. The enamel knot in this stage is better termed the ____
Tooth bell to the oral epithelium
Enamel cord
87
The dental follicle is responsible for the formation of the entire ____
Periodontium
88
During the bell stage, continued differentiation of what four distinct layers occurs?
Outer enamel epithelium
Stellate reticulum
Stratum intermedium
Inner enamel epithelium
89
The cervical loop forms at the junction of the ___ and the ___ and will form the future ___
Outer enamel epithelium
Inner enamel epithelium
CEJ
90
During the bell stage, the dental papilla cells continue to proliferate into the ___ cells and ___ cells
Outer dental papilla
Inner dental papilla
91
True or false... during the bell stage, the dental sac/follicle cells develop into periodontal tissues
False... although they continue to proliferate, they develop into periodontal tissues in a later stage
92
Describe the function of each...
Outer enamel epithelium
Stellate reticulum
Stratum intermedium
Inner enamel epithelium
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
What occurs during the apposition stage?
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
Describe the events of reciprocal induction (part of the apposition stage) in their order.
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
Why is it that the inner enamel epithelial cells change shape as they mature into preameloblasts and into ameloblasts?
They must grow lengthwise and move their nucleus to the opposite side to allow room for organelles for the production of enamel rods
96
The mesenchymal cells of the dental papilla condensate against the basement membrane of the enamel organ. These cells are called ___; these cells become the ____.
Outer cells
Preodontoblasts
97
As soon as predentin is secreted, the preameloblasts start laying down enamel. What is he difference between predentin and dentin?
Predentin is strictly organic; there is no mineral component
98
Where would you find Tome's process?
On the apical side of ameloblasts (side where enamel is being laid down)
99
At what point in development do you call the dental papilla pulp?
After you see differentiation of the odontoblasts and separation from the ameloblasts
100
Describe the apposition stage.
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
____ is secreted by odontoblasts and is strictly organic in nature. It induces differentiation of preameloblasts into ameloblasts
Predentin
102
Upon induction, ameloblasts begin secreting enamel which ____ calcifies to ____% of full mineralization
Immediately
25
103
Name three cell types that make up the dental follicle and what they give rise to.
Cementoblasts - cementum
Fibroblasts - PDL
Osteoblasts - alveolar bone
104
Name what cells make up the dental papilla and what they give rise to
Odontoblasts - dentin
Undifferentiated mesenchymal cells, fibroblasts - pulp
105
Name the seven stages of the ameloblast life cycle
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
Apposition and maturation of dentin and enamel occur in ____ from the ___ in a ___ direction
Increments/waves
Cusp tip
Cervical
(Think tree rings)
107
During the maturation stage of enamel.. after deposition and initial mineralization of enamel, secretory ameloblasts lose...
Tomes processes
108
What do maturation ameloblasts do?
Differentiate and remove enamel proteins and water, and pump additional calcium in the matrix
109
In the maturation stage, the final differentiation of ameloblasts takes place into what type of ameloblast?
Protective ameloblast
110
In the maturation stage... the enamel cuticle (a ____ type material) is secreted and ameloblasts attach to the enamel surface via ____. This will become the ____
Basal lamina
Hemidesmosomes
Epithelial attachment after eruption
111
When does the reduced enamel epithelium form? What is it?
After the enamel is fully matured.
REE consists of outer enamel epithelium, stellate reticulum, stratum reticulum, and inner enamel epithelium.
112
True or false... dentin mineralizes as it is deposited
True
113
Initial mineralization of dentin is in the form of ____, producing ____
Globules
Globular dentin
The globules fuse together as mineralization proceeds
114
What is mantle dentin?
Initial layer of dentin next to the DEJ
Collagen fibers perpendicular to DEJ
Higher mineral content
115
What is the circumpulpal dentin?
Remaining dentin around pulp
Collagen fibers parallel to DEJ
Lower mineral content
116
What is hertwig's root sheath?
Structure that determines how roots are sized, shaped and numbered
Stimulates the outer enamel epithelium to become cementoblasts
117
Reduced enamel epithelium grows in an ___ direction at the ____ and becomes the ____
Apical
Cervical loop
Hertwig's epithelial root sheath
118
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 _____
Dental papilla
Hertwig's epithelial root sheath
Predentin
Epithelial rests of malassez
119
What do the epithelial rest cells of malassez help form?
PDL
120
True or false... roots are not complete until after the tooth has erupted and is in function
True
121
Describe the formation of cementum
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
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 ____
Cementoid
Mineralizes
Cementocytes
123
True or false.. the newly formed PDL is highly organized
False.. it is not very organized until it is functioning
124
In the PDL, fibroblasts are produced by differentiated ____
Ectomesenchyme cells
125
What are fibroblasts role in the PDL formation?
They secrete collagen that anchor the cementum into bone as it is deposited
126
Describe the formation of alveolar bone
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
Roots are between ___ and ___ of the way formed by the time eruption begins
1/3rd and 2/3rds
128
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
True
129
Enamel is ___ in origin
Ectodermal
130
True or false... enamel is nominal while dentin is vital
True.. dentin has odontoblasts processes in the dentin that make it vital
131
What structure gives the enamel some flex so that it is not overly brittle?
DEJ
132
Mature enamel is thicker at the ___ and thin at the ___
Crown (around 2.5mm)
Cervical line
133
What percent of enamel is inorganic material, organic material, and water?
Inorganic - 96%
Organic - 1% (provides organization)
Water- 3%
134
True or false.. the organic component of enamel is mostly composed of collagen
False!!! No collagen. NO COLLAGEN. NO COLLAGEN. NO. COLLOGEN
135
What are the major enamel proteins in enamel?
Amelogenins, ameloblast is, enamelin, tuftelin, and others
136
Each enamel rod traces the path of an ___ thus doesn't run completely straight
Ameloblast
137
True or false... rod and interrod enamel have different protein compositions
False. They are identical in their composition
138
The main mineral component of enamel is ___ although a lot is actually ___
Hydroxyapatite
Carbonatoapatite
139
Hydroxyapatite easily swaps out other minerals in its structure. True or false.. although some are anti caries, some are pro caries
True
Fluoride is anticavities
Magnesium makes teeth more vulnerable to acid attack
140
What is the formula for hydroxyapatite?
Ca5(PO4)3(OH)X2
141
In order to form carbonatoapatite, CO3 2- can substitute for both ___ and ___
PO4 3- (usually)
OH- (sometimes)
142
___ 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?
Carbonate and magnesium
Fluoride
Outer enamel
143
Due to the shape of each unit "cell" of hydroxyapatite, each crystal is somewhat ____ in shape
Hexagonal
144
What are the dimensions of mature hydroxyapatite crystals?
60-70nm wide, 25-30nm thick
145
True or false... enamel crystals are very long and may well run the entire length of enamel thickness (mm in length)
True
146
Hexagonal symmetry ___ as crystals mature, and ___ their shape as they fully mature
Increases
Lose (somewhat)
147
Describe enamel rods
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
True or false.. all rods run in the same direction
False.. although they are organized into rows, they run in alternating directions.
149
True or false.. you can identify the orientation of enamel rods through light microscopy
False.. you must use SEM
150
True or false.. ameloblasts directly produce the hydroxyapatite crystals
False.. they produce the proteins for a scaffolding for the crystals to form
151
Describe rod sheaths
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
What occurs in the gaps of rod sheath?
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
Name two rod sheath proteins
Ameloblastins and amelogenins
154
What portion of enamel do caries progress?
They penetrate through the higher protein rod sheath areas, thus between rod and interrod enamel.
155
The initial deposition of enamel is only around ___% mineralized
30
156
As enamel matures, ___ component decreases while ____ increases
Organic
Mineralization
157
What are the three general phases to ameloblast maturation?
Pre-secretory - mature from pre-ameloblasts to ameloblasts
Secretory - deposition of enamel
Maturation - reduction of organic matrix, increase mineralization via ion transport
158
Ameloblasts deposit organic matrix via ____ which exit the cell ___
Secretory vesicles
Apically
159
True or false.. the basal lamina between the predentin and ameloblasts remains and becomes the DEJ
False. The basal lamina is broken down as it is penetrated by cell projections
160
____ projects into the developing enamel and is a site of much secretory activity
Tome's processes
161
True or false... Initial enamel in apposition to dentin does not have a rod arrangement, it is uniform
True
162
True or false... tome's fibers are involved in the deposition of enamel
False. Tome's processes are involved in the deposition of enamel, not fibers!
163
The distal portion of tome's process is towards the ___ while the proximal portion is towards the ___
Enamel
Stratum intermedium
164
Describe the formation of interrod enamel by Tome's processes
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
What happens to ameloblasts after they have laid down their enamel?
Return to being a squat cell, much like a preameloblast
166
Describe the formation of the reduced enamel epithelium
Loss of stellate reticulum and fusion of the outer enamel epithelium and the inner enamel epithelium give rise to the REE.
167
Prior to eruption, enamel hardens and becomes highly mineralized... how? How long does this take?
Through the removal of water, organic material, and increased HA crystal diameter
Up to 5 years
168
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?
Helps regulate movement of fluid/material
Not made with collagen 4
169
What is the process of modulation in regards to enamel maturation?
Process by which water and proteins are removed. Fluctuations in the distal membrane of ameloblast layers. "Ruffling and smoothing"
170
What do ruffles cells do?
"Putting stuff in"
Infiltration and incorporation of calcium ions into crystals. Occurs during ruffling, lower pH favors mineralization. Secretes proteolytic enzymes
171
What do smooth cells do?
"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
What is the fate of the enamel organ?
Enamel organ remnants fuse with the oral epithelium, forming a covering over the tooth
173
Both the primary and secondary enamel cuticles comprise nasmynth's membrane. What is the primary and secondary cuticle?
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
Of the following receptors.. categorize each one as cell surface or intracellular.. Steroids, FGFR, TGF-B, retinoids, thyroid hormone
Cell surface: TGF-B, FGFR
Intracellular: steroids, retinoids, thyroid hormone
175
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
True
176
Enamel formation is not simultaneous. What is one reason why the enamel is thicker coronally than cervically?
Tooth formation goes apically, thus as the crown grows, new ameloblasts are coming into play cervically
177
Name three enamel proteins that are deposited during apposition
Ameloginins
Ameloblastin
Enamelin
178
Name two enzymes that are involved in the organic component degradation during enamel maturation.
Enamelysin
Enamel matrix serine protease (kallikrein 4)
179
What enamel proteins are involved in maturation of the basal lamina?
Amelotin
ODAM (odontogenic ameloblast associated protein)
180
Describe Amelogenins
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
Describe Ameloblastin
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
describe enamelin
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
Describe enamelysin
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
Describe enamel matrix serine protease
Secreted during modulation events of enamel maturation. Degrades amelogenins.
Loss of function leads to immature enamel
185
What are included in the basal lamina proteins?
ODAM and Amelotin
No collagen IV!
186
Name two functions of enamel acid etching
Provides better bonding surface by increasing the porosity of enamel to increase infiltration of bonding material. Also removes "crap" from the surface
187
Why is it that enamel crystals dissolve best from the inside out and from the ends?
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
What are the three different types of enamel etching patterns?
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
True or false... it is more harmful to remove enamel proteins than mineral because the mineral can regenerate while the proteins cannot
True
190
Describe how age changes the enamel in regards to color, nature of surface layer, water content, brittleness, and permeability.
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
Explain how the age changes in enamel over time contribute to an overall decreased risk for caries
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
Name the two periodic features of enamel
Striae of Retzius/perikymata
Cross striations
193
Name the two optical features of enamel.
Hunter-schreger bands
Gnarled enamel
194
Name the three histological features of enamel
Enamel tufts
Enamel lamellae
Enamel spindles
195
Describe striae of retzius
"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
An accentuated striae (darker) called the _____ reflects physiological changes occurring during birth. These are found in all ____ teeth, and sometimes ____
Neonatal line
Primary
Cusps of first molars (because these teeth are starting to form around the time of birth)
197
What are perikymata?
Surface manifestations of striae of retzius visible on the enamel surface
There are shallow furrows where the stria intersect on the surface.
198
What direction do cross striations run? How far apart are they?
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
Stria of retzius appear best in ____ sections
Longitudinal
200
What are bands of Hunter-schreger?
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
What is gnarled enamel?
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
What are enamel tufts?
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
What are enamel lamellae?
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
What are enamel spindles?
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
True or false... ameloblasts are very susceptible to physiological changes
True
206
Why is too much fluoride during tooth formation bad?
It can lead to fluorosis. Excess fluoride interferes with amelogenesis and makes hypermineralized enamel with a chalky white appearance with pits in teeth
