Exam 1 Flashcards
(240 cards)
1
Q
what is the primary epithelial band? what does it become?
A
thickened epithelium that becomes dental lamina and vestibular lamina
2
Q
what initiates tooth formation
A
dental epithelium initiates tooth formation (requires ectomesenchyme to progress to later stages)
3
Q
characteristic event of initiation stage
A
epithelial band splits.
dental lamina invaginates and forms lingual side
vestibule lamina forms invaginates and forms a trough labially
4
Q
what demarcates the initial site of each tooth bud forming in the oral cavity
A
dental lamina
5
Q
beginning at the ___, the ectomesenchyme determine the type of tooth formed and directs morphogenesis of the tooth
A
bud stage
6
Q
what condenses and surrounds epithelial bud at bud stage
A
ectomesenchyme
7
Q
what causes tooth bud epithelium to proliferate and epithelium to fold
A
signaling from ectomesenchyme
8
Q
what leads to change of bud shape
A
folding of epithelium occurring closest to ectomesenchyme (leads to cap stage)
9
Q
Cap stage functional stage
A
morphogenesis - process of changing tooth shape due to folding of epithelium
10
Q
what directs folding and shape changes of enamel organ?
A
aka morphogenesis directed by ectomesenchyme
11
Q
when is tooth germ first recognized
A
early cap
12
Q
early cap: proliferation and folding of epithelium of tooth bud (oral ectoderm) becomes what?
A
enamel (dental) organ
13
Q
early cap: ectomesenchyme condensing beneath tooth bud becomes?
A
dental papilla
14
Q
early cap: condensation of ectomesenchyme surrounding the outside of tooth bud and papilla becomes?
A
dental follicle/sac
15
Q
when does enamel knot appear?
A
begins at end of bud thru late cap
best visualized in late cap
16
Q
what stage:
enamel organ has shape of a cap with convex and concave border; cap sits on a ball of ectomesenchyme
A
early cap
17
Q
when is a tooth germ comprised of the following three structures first visible: enamel organ, dental papilla, and dental follicle?
A
early cap
18
Q
characteristic events of late cap stage
A
- dental epithelium of enamel organ aggregates to form enamel knot
- primary enamel knot located close to ectomesenchyme of dental papilla
19
Q
what is the primary enamel knot?
A
signaling center that causes both enamel organ and dental papilla to differentiate into specific cells
20
Q
when does the primary enamel knot undergo apoptosis
A
end of cap stage
21
Q
what regulates tooth shape, size of crown and cusp formation by controlling proliferation and differentiation of enamel organ and dental papilla
A
primary enamel knot
22
Q
what morphological stage: differentiation - enamel organ and dental papillae differentiate into specific cell types (cytodifferentiation)
A
bell stage
23
Q
characteristic events of early bell stage
A
- tooth germ differentiation (enamel organ becomes 4 layers)
- cervical loop is visible
- secondary enamel knot visible for multi0cusped teeth
- dental papilla starts to differentiate into pre-odontoblasts to odontoblasts
24
Q
what are the 4 epithelial layers first visible at early bell
A
OEE, stellate reticulum, stratum intermedium, and IEE
25
what secretes alkaline phosphatase needed for mineralization
stratum intermedium
26
what stage is this:
enamel organ shape of bell with convex and concave border; four cell layers are visible. Cervical loop visible, dental papilla enclosed within the concavity of the enamel organ. Dental follicle is visible surrounding convex surface
early bell
27
what is a characteristic event of late bell
cusp formation (dentinogenesis = denttin deposition)
28
cusp formation at late bell leads to?
1. maturation of IEE to ameloblasts
2. differentiation of odontoblasts
3. deposition of the unmineralized predentin matrix from odontoblast in region of cusp (will mineralize into dentin)
29
first site of IEE maturation is where? least mature is where?
first site: cusp tips
least mature: down at cervical loop and between cusps
30
where are undifferentiated pre-odontoblasts closest to?
cervical loop region
31
secondary enamel knots appear only where?
multi-cusped teeth - located at tips of future cusps that serve as signaling center
32
where does cusp formation occur in single cusp teeth
where primary knot was initially located
33
how does future pulp chamber form
cervical loop elongates due to growth/folding of cusps and encloses the dental papilla
34
the tooth loses contact with oral cavity as what happens?
as dental lamina degenerates
35
at late bell, the dental follicle remains _ until root forms
undifferentiated
36
at late bell, _ is visible lingual to anterior primary teeth
successional lamina
37
in ___, predentin is deposited and the dentin matrix is beginning to mineralize but enamel has not yet been formed
late bell
38
__ formation precedes __ deposition
dentin formation precedes enamel deposition
39
late bell: signals from enamel knot cause
1. ameloblasts begin to differentiate first from the enamel organ at level of cusp - no enamel secreted yet
2. odontoblasts mature and differentiates from dental papilla at level of cusp -> predentin deposition and dentin mineralization begins
40
cells of dental papilla closest to _ in enamel organ differentiate into mature odontoblasts
closest to ameloblasts
41
odontoblast maturation shape change
cuboidal -> columnar cell with odontoblastic process on apical surface of odontoblast
42
function of mature odontoblasts
1. synthesize and secretes daily increments of predentin matrix
2. odontoblastic processes facilitate mineralization of dentin after predentin deposited
3. mineralization occurs around odontoblastic process forming dentin tubule
4. odontoblasts move toward pulp with successive increments of denin matrix
43
what forms dentin tubule
mineralization of odontoblast around the odontoblastic processes
44
when is predentin first deposited? where?
first deposited in late bell
in area adjacent to ameloblasts (future DEJ) at futue cusp
45
what is always located along pulp border between dentin and odontoblasts? what is it comprised of?
predentin unmineralized organic matrix always located there
comprised of type I collage and organic dentin specific proteins (for scaffolding of hydroxyapatite)
46
what does incremental mineralization of pre-dentin matrix mean?
following predentin mineralization, dentin mineralization begins 24 hours after
- involves deposition and coalescing of hydroxyapatite crystal
- following mineralization, new layer of pre dentin deposited
47
what causes terminal differentiation and maturation of immature into secretory ameloblasts in cusps?
presence of dentin matrix and signaling from odontoblasts
48
__ and __ deposition continues for the life of the tooth - deposited in crown and root
predentin and dentin
49
two regions of dentin in crown
1. mantle dentin - closest to DEJ of cusps, first mineralized
2. circumpulpal dentin - bulk of dentin found in crown lies closest to predentin/pulp
50
what occurs in appositional stage
enamel and dentin deposited incrementally in successive layers
51
what occurs during crown stage
1. deposition of hard tissue begins at DEJ of cusps before continuing towards cervix/cervical loop
2. enamel and dentin deposited simultaneously
3. ameloblasts are at different stages of maturation
52
what initiates crown stage
immature ameloblasts mature into secretory ameloblasts and begin to deposit partially mineralized enamel matrix along DEJ at future cusp
53
what triggers ameloblast to terminally differentiate into secretory ameloblasts at the future cusps
presence of dentin matrix and signaling from odontoblast
54
what are the stages of ameloblast differentiation
1. pre-secretory (inductive stage)
2. secretory stage
3. maturation stage
4. protective stage
55
what is the pre-secretory stage of ameloblast differentiation
- aka inductive stage (occurs during crown stage)
- goes from cuboidal to columnar
- cell is polarized (apex and base)
- terminally differentiated
56
what is the secretory stage of ameloblast differentiation
two types of columnar polarized cell
1. no tomes process
2. tomes process on apical surface to determine orientation of enamel crystals
57
what is the maturation stage of ameloblast differentiation
removal of water/organic ECM; final mineralization
ruffled and smooth
58
what is the protective stage of ameloblast differentiation
ameloblasts become cuboidal again and fuses with remnants of enamel organ
59
where are immature IEE cells usually found
at cervical loop and intercuspal region of multicusped teeth
60
what are the cells involved in amelogenesis
1. secretory ameloblast
2. maturational ameloblast
61
steps of amelogenesis
1. secretory stage > partial mineralization of enamel into crysals (begins early crown stage and continues until full thickness deposited in a region)
2. maturation stage > pattern follows secretion, final maturation of enamel matrix increases hydroxyapatite and removes organic matrix
62
types of secretory ameloblast? function?
with and without tomes process
fn: synthesize organic ECM and partially mineralize matrix at time of deposition
63
ameloblast secrete unique enamel matrix proteins. describe these proteins
- no collagen
- two classes: amelogenin proteins (90%) and non-amelogenin (10%)
64
steps of enamel secretion
1. ameloblast synthesizes unique enamel matrix proteins
2. partial mineralization of enamel
3. maturation stage
4. protective stage
65
three orientations of enamel crystals
1. aprismatic/structureless - enamel crystals deposited parallel to each other and perpendiculr to surface (tightly packed). located at initial layer of DEJ and final layer on outer surface
2. prismatic - rod
3. inter-prismatic - interrod, located at bulk of crown
66
describe aprismatic enamel on surface of tooth
crystals are well aligned and tightly packed, so minimal organic ECM
67
outcome of aprismatic enamel
highly mineralized, less porous = better caries protection when compared to subsurface enamel
68
cells involved in maturation stage
1. ruffled mature ameloblasts - enamel increases in mineral content
2. smooth mature ameloblasts - removal of water and organic proteins from the enamel by enzymatic digestion
69
outcome of maturation stage
increased mineral content
- achieved by enzymatic removal and degrading most of organic ECM originally deposited and increasing mineral content
- increasin crystal size by increasing width and amount of hydroxyapatite comprising enamel matrix
70
what percent of immature enamel is mineralized at time of secretion
25-30%
71
mature enamel contains how much hydroxyapaptite, water, and organic ECM
96% HAP
3% water
1% ECM
72
failure to deposit adequate HAP leads to
hypocalcified enamel
73
failure to remove water and organic proteins leads to
hypomature/immature enamel
can also occur due to defects in enzymes necessary for organic matrix removal
74
how are all hard tissue deposited?
incrementally in successive layers by appositional growth
75
incremental lines in enamel are
Stria of Retzius
76
incremental lines in dentin are
Contour lines of Owen
77
what can arise when a given antibiotic causes permanent stain in teeth undergoing crown development?
tetracycline bands
78
cells involved in protective stage of amelogenesis
protective ameloblast (post-maturational cells)
79
characteristic events during protective stage of amelogenesis
- protective ameloblasts are flattened squamous cells without tomes process
- adhere to final layer of enamel
- contributes to formation of REE
80
what is REE
reduced enamel epithelium also called Nasmyth's membrane or developmental enamel cuticl
during eruption, fuses with oral epithelium to form junctional epithelium
81
what happens to the remaining cells of enamel organ following mineralization?
SI, SR, and OEE collapse and fuse with layer of protective ameloblasts to form REE
82
what structure signifies end of crown and start of root formation
Hertwig's epithelial root sheath - structure formed by fused cervical loop
83
devlopment of deciduous tooth crown extends from when to when?
4th month of gestation to approcimately 12 months
84
development of crowns on permanent teeth extends from when to when
begins around five (first molars) with completion of all permanent at approximately 8 years (3rd molar exception at 16 years)
85
when will roots form following crown formation
primary - roots complete 1.5 years after emergence into oral cavity
permanent - root complete 3.5 years after emergence into oral cavity
86
what is the mechanism controlling root development
inductive signaling b/w HERS and dental papilla and dental follicle (ectomesenchyme derived)
87
differentiation of dental follicle into the periodontium (alveolar bone, PDL, cementum) depends on what/
root development
88
what are the general stages of root development and approximately how much of root is developed?
1. root initiatiion
2. early root (1/4 root)
3. mid root (2/3 root, begins to erupt)
4. latte root (3/4 root, still erupting, not yet in occlusion)
5. root complete (after tooth in functional occlusion, apical foramen narrowed by dentin/secondary cementum)
89
what initiates root formation
crown completion and development of HERS
90
what is the function of HERS
HERS grows apically between papilla and dental follicle to elongate the root and delineate root shape and guide root growth.
Function: guide root growth
91
what is epithelial diaphragm
Epithelial diaphragm (ED) is the free bottom edge of HERS grows inward below the dental papillae and encloses the primary apical foramen.
Function: Differential growth of the ED determines final shape and number of roots
92
in multirooted teeth, what determines root numberr
differential growth and invagination of ED
causes ED to grow together at specific points to form furcation zone/point
93
steps of root formation
1. HERS develops from cervical loop of enamel organ
2. HERS induces odontoblast differentiation
3. deposition of predentin/dentin
4. dentin induces fragmentation of HERS
94
___ of HERS induces odontoblast differentiation
IEE epithelial cells of HERS
95
what type of dentin lies adjacent to HERS during deposition
mineralized radicular dentin
96
dentin in root is sometimes called ___.
dentin in crown is called ___.
all dentin deposited in crown and root prior to entering occlusion is classified as ___.
radicular dentin
coronal dentin
primary dentin
97
when does HERS move away from root surface and break down
after primary radicular dentin is deposited in root (due to programmed cell death)
98
what is a remnant of HERS that forms clusters of epithelial cells
epithelial cell rests (ectoderm derived)
**the only epithelial derived structure found in PDL
99
function of ECRs
1. maintains PDL homeostasis/turnoverr
2. maintains periodontal space -> prevents ankylosis; prevents root resorption
3. maintains orthodontic movements
100
structures formed during dental follicle differentiation
1. cementum
2. PDL
3. alveolar bone
101
principal cell types during dental follicle differentiation
1. inner layer > cementoblasts > cementum
2. middle layer > fibroblasts > PDL
3. outer layer > osteoblasts > alveolar bone
102
___ forms the supporting structures
and is induced to differentiate during root
formation by cells of HERS/ECR and the presence
of dentin and dental papilla
dental follicle
103
during bud to crown stage, the dental follicle is ___
undifferentiated
104
At this early root stage, radicular (root) dentin has stimulated HERS to _.
start to break down near cervix but remains still intact apically.
105
Acellular (primary) cementum deposition first occurs in ___. When deposition begins it will occur closest to crown (cementum has not yet been
begun in this section).
early root
106
cementum composition
40-50% HAP
50% organic matrix (requires alkaline phosphatase for mineralization)
107
cementum functiton
protect dentin-pulp complex
anchor tooth to alveolar bone via PDL
adapt for occlusal wear once tooth in occlusion
108
When and where is cementum first deposited
in early root stage beginning in region of tooth cervix and establishes CEJ junction
109
cementoblasts continue to differentiate and deposit primary acellular extrinsic fiber cementum until when? where is it deposited?
until tooth enters occlusion in late root.
this type of cementum deposited in cervical 2/3 of root.
110
3 types of cementum in adult root
1. primary acellular extrinsic fiber cementum - early, mid, late
2. secondary cellular intrinsic fiber - late, root completion
3. secondary mixed fiber cementum - during late and root complete (combination of above two)
111
potential pattern of cementum deposition in early root
1. cementum overlaps enamel and deposited in crown
2. enamel and cementum meet at cervix
3. gap exists between cementum and enamel
112
what causes cementum to overlap enamel and become deposited into crown?
if REE covering enamel breaks, and exposes enamel. the cementum lacks collagen (afibrillar)
113
what causes a gap between cementum and enamel?
if there is a delay in breakdown and movement of HERS away from dentin surface
114
what establishes the cementum-dentin junction?
cementoblasts in contact with dentin and secrete unmineralized matrix cementum (aka cementoid)
CDJ can also be called intermediate cementum
115
PDL fibers differentiate from dental follicle and become embedded in cementum. What are these fibers now called?
sharpey's fibers
these PDL fibers mature once in occlusion
116
what type of deposition does primary acellular cementum exhibit? why?
slow deposition prior to eruption. this allows PDL fibers to become trapped within cementum
117
what forms the main anchor for the tooth in the jaw
sharpey's fibers inserted into primary cementum
118
principal cell of PDL
fibroblast
- intermediate layer of follicle differentiates into fibroblast
- otherr cell types present including stem cells
119
ECM of PDL
collagen fibers and non-collagenous proteins deposited between cementum and alveolar bone
organic matrix: collagen (I, III, XII) and oxytalan (elastic)
synthesis of collagen depends on vitamin C
120
function of PDL
tooth attachment and adaptive response to occlusal load
121
PDL fiber function
serve to attch primary acellular cementum to bone
Collagen fibers synthesized by fibroblasts in PDL become embedded in primary cementum-fibers are known as extrinsic fibers (acellular extrinsic fiber cementum)
Distinct bundles of PDL, known as principal fiber group, are not recognized until tooth erupts in the oral cavity and in occlusion
122
principal fiber group
bundles of PDL not recognized until tooth erupts in oral cavity and in occlusion
123
PDL attachment
point of fiber attachment to bone and cementum via Sharpey's fibers
124
principal cell type of alveolar process
osteoblasts - differentiate from outer layer of dental follicle
125
what stimulates alveolar process development
depends on tooth development and eruption
stress helps maintain structure
126
during root formation, what does the alveolar process form?
labial and lingual bone
127
increased bone deposition forms a __ around the tooth and the __ separates adjacent teeth
crypt; interdental septum
128
two regions of jaw bone
1. basal bone - body of mandible or maxilla
2. alveolar process - stimulated to develop when tooth is present
129
what is the tooth socket also called
alveolar bone proper
130
types of hard tissue deposited in late root thru post-eruption/occlusion
1. formation of secondary dentin - dentin continues to be deposited throughout life of tooth
2. secondary cementum - two types occurs after tooth erupts and is in occlusion along apical 1/3 of root
131
types of secondary cementum
1. secondary intrinsic cellular fiber cementum
- formed once tooth in occlusion
- cementoctyes trapped within this matrix also synthesize collagen fibers
- location: mid to apical 1/3 and interradicular
- function: repair and adaption to occlusal wear
2. secondary cellular mixed fiber cementum
- mix of cellular intrinsic and acellular extrinsic found once in occlusion to adapt to occlusal wear
- near apical third to apex of tooth and furcation
- function: adaption to occlusal wear, ANCHORAGE, and aids in repair
132
two regions of mature alveolar process
1. supportive regions: outer cortical (compact bone) plate and cancellous (spongy central portion)
2. alveolar bone proper (alveolus): tooth socket - comprised of compact bone that anchors tooth
133
three regions associated with alveolar bone proper
1. interdental septum
2. interradicular septum
3. alveolar crest
134
area of mucoperiosteum
lamina propria attached directly to periosteum of bone
135
alveolar bone proper appearance
alveolus/tooth socket anchoring tooth
136
alveolar crest
part where alveolus and outer cortical plate of alveolar process meet
137
outer cortical plate
where attached gingiva is anchored to the bone
138
how to determine if section is in lower or upper third
lower: cells are present in cementum
upper: no cells in cementum
139
9 steps of root formation
1. HERS develops
2. HERS induce odontoblast differentiation
3. deposition of dentin in root
4. HERS root sheath breaks down
5. ECR remnant of HERS
6. ECR and dentin induce differentiation of dental follicle
7. cementoblast cells from dental follicle migrate b/w ECR and deposit primary acellular cementum on dentin matrix
8. PDL fibers differentiate from dental follicle
9. alveolar bone proper (tooth socket) differentiates from dental follicle
140
ankylosis
fusion of root dentin/cementum to bone due to loss of PDL
141
reciprocal signaling between what controls eruption
HERS/REE and dental follicle
142
3 phases of eruptive movements
1. pre-eruptive
2. eruptive; pre-functional
3. post eruptive
143
when do pre-eruptive movements occur
from cap stage until crown completion
144
purpose of pre-eruptive movements
accommodate growing tooth size and number, formation of bony crypts between primary and permanent, and jaw growth
145
function of pre-eruptive movements
to position tooth in jaw for eruptive process and emergence
146
what do pre-eruptive movements do
change tooth's orientation and physical position within the jaw to allow for emergence
147
position in jaw during pre-eruptive movements
submerged within bony crypt
all movements occur within jaw below oral mucosa
148
eruptive, pre-functional movements
1. intra-osseous
2. supra-osseous
149
purpose of pre-functional movements
moves tooth from bony crypt to emerge into oral cavity and into functional occlusion
- starts with root initiation
150
direction of pre-functional movements
axial.occlusal direction
151
post-eruptive movement, functional eruption timing
following eruption
152
post-eruptive movement, functional eruption purpose
required to maintain occlusal contact position while jaw grows and compensates for occlusal wear/interproximal wear
153
post-eruptive movement, functional eruption position in jaw
functional occlusion with contact -> continues life of tooth
154
what are pre-eruptive movements
movements occur prior to eruption
- movements of deciduous and permanent teeth prior to root formation
155
where do pre-eruptive movements occur
within bony crypts that surround growing tooth germ crown
156
function of pre-eruptive movements
- move teeth in position for functional eruption into oral cavity
- to accommodate growth of: developing jaw-bone, crown, adjacent teeth, increase in tooth number
157
Movements related to tooth eruption begin during crown formation and require adjustments relative to the formation of ___
bony crypt and neighboring tooth
158
Crowding due to increase crown size and increased tooth number is alleviated by ___
jaw growth and requires tooth movement
159
type of movements for primary teeth
1. mesial/distal -> vertical position (due to lengthening of jaw and increase height)
2. lingual position -> facial (due to increase in length and width of jaw)
3. occlusal (Vertical) -> due to height increase of jaw
160
why does the jaw increase in length during development
length: allows primary molars to move backward and anterior teeth to shift forward
161
whey does the jaw increase in height during development
allows developing teeth to move axial (upward)
162
why does the jaw increase in width during development
allows development teeth to move outward to accommodate the succedaneous teeth developing lingually
163
pre-eruptive movement of anterior permanent teeth
teeth develop in same crypt
as primary erupts, bone is deposited between erupting primary crown and permanent
- permanent now sits lingual to apical 1/3 of primary. during eruption, will shift lingual to facial and begin root resorption
164
pre-eruptive movement of posterior permanent teeth
physical displacement occurring as a result of jaw growth called BODILY MOVEMENT
PM: shift from lingual/occlusal position to interradicular position of primary molar
Molars: involves a rotational movement as jaw increases in length and height
165
what is the angle at which permanent molars move pre-eruptively
maxillary molar crown - developing distal inclination shifts vertical
mandibular molar crown - developing mesial inclination rotates into vertical
166
do both permanent premolars and molars develop interradicularly?
NO. PM does. Molars undergo bodily movement
167
function of eruptive pre-functional tooth movements
to bring developing tooth into oral cavity and accommodate root elongation
168
rate of movement between eruptive pre-functional tooth movements
intra-osseous: slow
supra-osseous: fast
169
what must be done to facilitate eruptive, pre-functional movement?
1. establish eruption pathway (remove overlying bone and remove overlying CT)
2. fusion of REE to OE allowing for tooth to penetrate oral mucosa
3. differentiation/remodeling of alveolar bone and PDL
170
how does the removal of overlying bone and CT occur to allow tooth to move into oral cavity?
REE covering tooth crown signals dental follicle to activate osteoclasts and digestive enzymes
outcome
1. resorption of bone above crown occurs thru osteoclasts
2. enzymes degrade overlying CT
3. once CT of coronal dental follicle removed, REE begins to proliferate
171
events during intra-osseous stage for primary tooth
1. creation of eruption pathway
2. root elongation continues as tooth moves axially
172
Is a root required for eruption
NO
a rootless tooth can erupt as long as DF is present and functional
173
events during supra-osseous stage
1. clinical eruption (1/2 to 2/3 root formed)
2. active eruption (2/3 to 3/4 root formed)
174
what occurs during clinical eruption
1/2-2/3 root formed
- fusion of OE and REE
- tip of crown breaks thru fused epithelium
175
what occurs during active eruption
2/3 to 3/4 root formed
- continued occlusal movement results in exposure of clinical crown
- active eruption continues until tooth enters occlusion
176
mechanism of action for clinical eruption
penetration of crown thru oral mucosa due to occlusal/axial movement and thinning of epithelial/CT barrier
177
outcomes of clinical eruption
1. tip of crown breaks thru fused epithelium
2. eruption establishes DGJ
3. REE surrounds crown like a cuff and becomes junctional epithelium
178
mechanism of action for active eruption
- HERS signals to dental follicle to deposit and remove bone apically as needed to accommodate root elongation (root continues to grow during active eruption)
- increased deposition/bone formation at alveolar crest (and inter-radicular septum for multirooted tooth) to maintain tooth position
179
outcomes of active eruption
1. exposure of clinical crown
2. continued eruption of tooth thru mucosa results in position of DJG to shift apically relative to tooth
180
passive eruption
continued exposure of anatomical crown due to an apical shift of gingiva and junctional epithelium (no tooth movement)
181
gingival recession
due to periodontal disease/inflammation will expose more cementum as JE moves below CEJ due to loss of attachment epithelium
182
clinical crown
exposed crown extending from cusp tip to area of gingival attacchment
183
anatomical crown
entire crown, extending from cusp tip to CEJ
184
DGJ
point where free gingival margin, sulcular epithelium, and JE meet
185
what must be present for eruption to occur
dental follicle
removing DF removes signalling and cannot know to erupt
186
what happens if DF is removed in coronal region
- no bone resorption
- no eruption
187
what happens if DF is removed in apical region
- no bone deposition
- no eruption
188
jaw growth and bone remodeling results in
pre-eruptive movements
189
signaling from REE/HERS and DF (coronal bone resorption) results in
pre-functional intra-osseous
190
root elongation and bone remodeling results in
pre-functional supra-osseous
191
gingival resorption (e.g. removal of intervening CT of dental follicle) results in
clinical eruption
192
late root formation and bone remodeling results in
active eruption
193
bone and PDL remodeling, deposition of cementum, and mesial drift result in
post-occlusion
194
major difference between permanent and primary tooth eruption
permanent tooth eruption requires exfoliation of primary tooth
195
eruption pathway for anterior teeth
forms gubernacular canal (eruption canal) lingual to primary
196
gubernacular canal contents
canal is a remnant remnant of successional dental lamina - aka gubernacular cord
gubernacular cord directs path of eruption for permanent anterior teetth
197
eruption pathway for premolars
positioned between roots following pre-eruptive movement and being inter-radicular resorption between roots of primary molars
198
eruption pathway for molars
must create a new eruption canal following pre-eruptive bodily movement since there is no primary tooth
199
how are anterior primary teeth exfoliated for permanent anteriors
start resorption lingual to apical 1/3 of primary root -> moves facial/labial to erupts
200
how are primary teeth molars exfoliated for PM
begins interradicular between roots primary molar, and PM graduallt moves occlusally
201
is there primary tooth resorption to make room for permanent molars
No. Remodeling crypt to allow for mesial or distal rotation of tooth germ to vertical position to create eruption path
202
pre-eruptive movement of primary teeth
movement due to jaw and increased tooth number
203
eruptive action of primary teeth
- coronal removal of overlying bone and CT by osteoclast/enzymes to establish eruption path
- bone deposition/root elongation apically
204
pre-eruptive movement of anterior permanent teeth
separate bony crypt formed, lingual to primary tooth
205
pre-eruptive movement of PM permanent teeth
facial shift to interradicular position between primary molars
*pre-eruptive bodily
206
pre-eruptive movement of molar permanent teeth
shifts crown position due to jaw growth
- maxillary distal incline to vertical
- mandibular distal incline to vertical
*pre-eruptive bodily movement
207
eruptive, intra-osseous movement of anterior permanent teeth
remove overlying bone/CT
- forms gubernacular canal: eruption pathway for anterior teeth
- permanent moves lingual to facial in jaw, resorbing primary anterior root
- root resorption of primary tooth
- bone deposition/root elongation apically of secondary
208
eruptive, intra-osseous movement of PM permanent teeth
inter-radicular root resorption of primary molars
209
eruptive, intra-osseous movement of molar permanent teeth
removal of overlying bone and CT
- no resorption of primary tooth
- intra-osseous path similar to primary teeth
210
histological features of exfoliation
1. coronal resorption of alveolar bone crypt
2. resorption of cementum of primary tooth and repair is possible of cementum
3. resorption of dentin of primary tooth (osteoclasts/odontoclasts)
4. localized necrosis of radicular pulp (and coronal pulp intact)
5. loss of PDL fibers of primary tooth
6. remodeling of PDL of permanent tooth
211
root resorption and repair
shown by reversal line
- signs of repair in secondary cementum and PDL reanchorage
212
mechanisms controlling exfoliation
extrinsic signals originating from permanent tooth and intrinsic signals from primary tooth
213
extrinsic signaling during exfoliation
between REE and dental follicle
facilitates breakdown of overlying gingival CT and bone and dental hard tissue of primary tooth by producing enzymes and recruiting osteoclasts/odontoclasts to the area
214
intrinsic signaling during exfoliation
comes from the pulp, cementum, and PDL of the primary tooth
serve in recruitment of odontoclasts/osteoclasts to begin root resorption
215
when do all crowns of primary teeth start to calcify? when are all crowns complete?
start to calcify prior to birth (5 mo. in utero)
crowns complete by 1 year
216
6/4 rule
from birth, 4 teeth erupt for each 6 mo. of age
typically 2/3 of root formed at clinical eruption
217
Eruption begins with the primary Mandibular central incisors around __ mo.
Eruption begins with the primary mandibular central incisors around 6mo.
218
Eruption sequence for primary teeth:
CI, LI, M1, C, M2
219
Primary M1 erupts @ __ and M2 erupts @ __
1 yr; 2 yrs
220
primary teeth root isn't complete until __ post-eruption
1-1.5 years
221
what is one of the last permanent teeth to erupt due to having longest eruption path
maxillary canine
222
when do permanent first molars begin crown formation
at birth
223
what are the first permanent teeth to erupt
first mandibular molars followed by maxillary molar at 6 years
224
what are the first teeth to erupt that develop from successional lamina
mandibular central incisors - erupts at 6 years (all about the same time as first molars)
225
eruption sequence of permanent teeth
M1, CI, LI, canines, PM1, PM2, M2, M3
mandibular arch ahead of maxillary arch
226
how old when permanent canines and PM erupt? when do the second permanent molars erupt?
canines and PM: 9-11
second permanent molars: 12 yrs
227
do permanent teeth follow the rule of 4's?
yes, except for 3rd molars
228
what is premature exfoliation? causes?
exfoliation prior to normal age
causes: dental caries, defective root formation (short roots), defective tooth anchorage (hypoplasia cementum or dentin dysplasia), trauma, infection/inflammation, or systemic disease
229
what is delayed exfoliation? causes?
retention of primary tooth (occurs beyond normal exfoliation time)
causes: hypodontia (congenital absence) of successor, primary tooth in submerged position due to ankylosis of primary tooth with bone, abnormal position of permanent tooth leads to ectopic eruption, impaction of successor's teeth, or delayed eruption of successor
230
enamel organ germ layer
ectoderm
231
dental papilla germ layer
ectomesenchyme
232
dental follicle germ layer
ectomesenchyme
233
when primary tooth at bell stage, successional tooth at _ stage
bud
234
primary anterior tooth at crown stage, successional tooth at _ stage
cap
235
primary anterior tooth at early root stage, successional tooth at _
late bell
236
primary tooth at functional stage, successional tooth at
early to mid crown
237
primary anterior tooth shedding, successional tooth at
early root
238
if there is an absence of a primary second molar, what corresponding permanent tooth is missing? why?
permanent second pre molar would be missing. permanent 2nd PM develops from successional lamina of primary tooth predecessor
239
when does initiation, bud, cap, early bell, late bell, crown and root stage occur in primary teeth?
initiation: 6-8 weeks prenatal
bud: 8-10 weeks
cap: 10-12 week
early bell: 12-14 weeks
late bell: 14-18 weeks
crown stage: 18 weeks prenatal (all crowns begins to calcify by 6 months in utero and complete before 1 year post natal
root stage: roots complete 1-1.5 years post eruption, all complete by 3 years
240
when does initiation, bud, cap, early bell, late bell, crown and root stage occur in permanent teeth?
initiation -> late bell: 4 months prenatal 1st molar, 5 months incisor, and all other begin post natal starting 10 months
crown stage: 1st M calcify at birth, CI 4 months post natal, all other by 4 years. all crowns complete by 8 years and 3rd molar is last to calcify at 8-10 years
root: root complete 3 years post-eruption. all complete by 16 years EXCEPT 3rd which occurs at 25 years
