Development of the teeth ch. 5 me
The mineral content of enamel is approximately ___% as it rapidly surpasses that of dentin (69%) to become the most highly calcified tissue in the human body.
95%
Because the permanent molars do not succeed the primary teeth, they do not form from the successional lamina but from the general lamina and are termed?
Accessional teeth
Matrix formation and mineralization are closely related; mineralization proceeds by an increase in mineral density of the _____.
Dentin
The first enamel deposited on the surface of the dentin establishes the _______ _______.
Dentinoenamel junction
Each stage of tooth formation is defined according to the shape of the ?
Ectodermally derived enamel organ; which is part of the developing tooth.
The initial deposition of mineral amounts to approximately 25% of the total ____. The other 70% of mineral in ____ is a result of growth of the crystals.( 5% of ___ is water.)
Enamel x3
What is an example of "cell signaling"
Epithelial-mesenchymal interaction in tooth development. See page 64
True or false: Many separate events occur within a few inches during development of the dentition.
False - its within a few "millimeters"
As the ameloblast differentiates, the matrix is synthesized within the RER, which then migrates to the ____ _____, where it is condensed and packaged in membrane-bound granules.
Golgi apparatus
Developmentally missing teeth can be a result of a genetic abnormality. When fewer than six teeth are missing, it is termed _____, and when more than six teeth are missing, it is called _____.
Hypodontia, oligodontia
What is the primary function of the apical cementum?
It involves the attachment of the principle periodontal ligament fibers.
Primary and permanent teeth develop very similarly, although the time needed for development of primary teeth is much ___ than for the permanent teeth.
Less
The cementum usually appears cellular, although the cementum near the cementoenamel junction is ___ cellular than at the apices of the root.
Less cellular
The primary and permanent teeth develop from the interaction of the oral ectodermal cells and the underlying ______ cells.
Mesenchymal
The neural crest cells arise and begin their migration from the mesencephalic portion of the developing neural tube at an early stage of development and migrate into the jaws, intermingling with ____?
Mesenchymal cells
The dental lamina develops into a sheet of epithelial cells that pushes into the underlying mesenchyme around the perimeter of both the maxillary and mandibular jaws beginning at the ?
Midline
What cells function in the development of the salivary glands, bone, cartilage, nerves, and muscles of the face?
Neural crest cells
The initiating dental lamina that forms both the successional and general lamina begins to function in ___ prenatal week and continues to function until the ____ year, producing all 52 teeth.
Sixth; fifteenth
Alveolar bone proper lines the tooth socket, sustained by supporting bone, which is composed of both ____ bone and ___ or ___ bone.
Spongy/ dense or compact
Some follicular cells, which lie immediately adjacent to the enamel organ, migrate during the cap and bell stages fro the enamel organ peripherally into the follicle to develop the ?
alveolar bone and the periodontal ligament
In the mature form, alveolar bone is composed of ____ ___ ____ and ____ ____.
alveolar bone proper and supporting bone
As amelogensis proceeds, both the ameloblasts and stratum intermedium, are held together by cell junction complexes termed ______, with synthesis of enamel occurring in both cells.
desomosomes
The second dentition does not ___ until after the primary teeth are formed and functioning.
develop
The time of function of permanent teeth includes 12 years of ______, 3 years longer than primary teeth.
development
Finally, after the ameloblasts have completed their contributions to the mineralization phase, they secrete an organic cuticle on the surface of the enamel, which is known as the ____ or primary cuticle.
developmental
At the bell stage, cells of the inner enamel epithelium _____.
differentiate; they elongate and are ready to become active secretory ameloblasts.
What is another term for dentition
diphyodont
The initial stage, bud stage, is a rounded, localized growth of _____ cells surrounded by proliferating _____ cells.
ectodermal cells/mesenchymal cells
Only a few ameloblasts at the tip of the cusps begin to function initially; as the process proceeds, more ameloblasts become active, and the increments of _____ matrix become more prominent
enamel
Ameloblasts begin ____ _____ after a few micrometers of dentin have been deposited at the dentinoenamel junction.
enamel deposition
At each cusp tip, an ____ ____ , or a condensation of cells, forms that coordinates crown development.
enamel knot (in teeth w/ multiple cusps, there is an enamel knot for each cusp)
When several increments of dentin have formed, the differentiated ameloblasts deposit an _____ _____.
enamel matrix
During the bell stage, the cells of the enamel organ have differentiated into the "outer enamel epithelial cells," which cover the ___ ____, and the "inner enamel epithelial cells, which become the ______ that forms the enamel of the tooth crown.
enamel organ; ameloblasts
Teeth develop from two types of cells: oral ectodermal cells form the enamel _____ and mesenchymal cells form the dental _____.
enamel organ; dental papilla
The inner cell layer of the root sheath forms from the inner enamel epithelium or ameloblasts in the crown, and _____ is produced. In the root, these cells induce odontoblasts of the dental papilla to differentiate and form ____.
enamel/dentin
As the cervical region of the crown mineralized, protein of the enamel changes or matures and is termed:
enamelin
During the bell stage, cells in the periphery of the dental papilla become _____.
odontoblasts (these cells differentiate from neural crest cells or synonymously, ectomesenchymal cells).
The function of the outer enamel epithelial cells is to ____ a network of capillaries that will bring nutrition to the _______.
organize; ameloblasts
Between the OEE and IEE layers, are the ____ _____ cells, which are star shaped w/ processes attached to each other.
stellate reticulum
From the "outer enamel epithelium," nutrients will percolate through the ____ _____ to the ameloblasts.
stellate reticulum
Substances needed for enamel production arrive via the blood vessels and pass thru the _____ _____ to the stratum intermedium and ameloblasts.
stellate reticulum ( in this manner the protein amelogenin is produced)
A fourth layer in the enamel organ is composed of ____ _______ cells; these cells lie adjacent to the inner enamel epithelial cells.
stratum intermedium
A hemidesmosome is half of a desmosome-attachment plaque. Whereas a desmosome functions in attaching a cell to an adjacent cell, a hemisdesmosome relates to the attachment of a cell to a _____ ______.
surface membrane
Junctional complexes called the _____ _____ ____, consisting of a series of desmosomes, appear at the junction of the cell bodies and Tomes processes and maintain contact between adjacent cells.
terminal bar apparatus
What does the "supporting bone" form?
the cortical plate, which covers the mandible
As the teeth develop, so does the alveolar bone, which keeps pace with what?
the lengthening of roots
At the bell stage, the "inner enamel epithelial cells" are characterized by the shape of the ____ they form.
tooth
Growth of individual cusps by incremental deposition continues until ____ _____.
tooth eruption
What do you call the bone that forms between the roots of the multirooted teeth?
interradicular bone
When a developing molar is sectioned thru the center of its root, it shows the root sheath as an ____ of cells.
island
At first, the alveolar process forms ____ and ____ plates between which a ___ is formed where the tooth organs develop.
labial-lingual plates/ trench
Densely packed cells characterized the dental papilla; this is evident in the early bud stage, during which cells proliferate around the enlarging tooth buds at the ____ ____ of the dental lamina.
leading edge
Primary teeth begin to develop in utero, and the crown undergoes complete _____ before birth, whereas the permanent teeth begin formation at or after birth.
mineralization
After further growth of the papilla and the enamel organ, the tooth reaches the _______ and _______ stage, aka the bell stage.
morphodifferentiation/histodifferentiation
Accessory root canals may connect the pulp with periodontal ligament at any point along the root, although is usually appears where?
near the root apex; pulp or periodontal infection can spread by means of this route to the adjacent tissue. A periodontal pocket that is resistant to treatment could be caused by this defect.
As the papilla grows, smaller vessels are also seen in the periphery of the organ, bringing nutrition to the elongating ______.
odontoblasts
When ameloblasts begin secretion, the overlying cells of the stratum intermedium change in shape from _____ to _____.
spindle/pyramidal
Primary teeth function in the mouth approximately 8.5 years; this period of time may be divided into what 3 periods?
1) crown and root development (about a year) 2) root maturation and root resorption (about 3.75 years) 3) shedding of the teeth (about 3.75 years)
Ameloblasts exhibit changes as they differentiate and pass thru what five functional stages:
1) morphogenesis 2) organization & differentiation 3) secretion 4) maturation 5) protection
The permanent molars may be in the mouth only from the ___year on until they are lost or death occurs.
25th year
At the proliferating end, the root sheath bends at a near __degree angle; this area is termed the _____ _____.
45 degrees/ epithelial diaphragm
Enamel synthesis, secretion, and subsequent mineralization is a complex process involving what structural proteins?
Amelogenin Ameloblastin Enamelin Two proteinases: Kallikren-4 and enamelysin
The dental lamina disappears in the _____ part of the mouth, although it remains active in the _____ region for many years.
Anterior/ posterior
In general, the teeth develop _______, which relates to the growing _____.
Anteroposteriorly; growing jaws
Although tooth formation is a continuous process, it is characterized by a series of easily distinguishable stages known as ____, ____, _____ stages.
Bud; cap; bell stages
Papilla cells are believed to be significant in furthering enamel organ bud formation into the _____ and _____ stages.
Cap/bell
Cells interact thru a system of effectors, modulators, and receptors called ______.
Cell signaling
After the completed tooth crown erupts into the oral cavity, root formation and _____ continue until a functional tooth and its supporting structures are fully developed.
Cementogensis
Dentinogensis takes place in two phases. First is the _____ _____formation, followed by the deposition of _____ ____ crystals in the matrix.
Collagen matrix/calcium phosphate (hydroxyapatite):
With mineralization of enamel completes and its thickness established, the ____ of the tooth is formed. Meanwhile, the ____ formation proceeds. The next stage of development will be _____ formation.
Crown/dentin/root
The first sign of tooth formation is the proliferation of ectodermal cells overlying specific areas of the oral ectoderm; their proliferation results in the development of the?
Dental Lamina
After primary teeth develop from the buds, the leading edge of the lamina continues to grow to develop the permanent teeth, which succeed the 20 primary teeth. This part of the lamina is thus called the ?
Successional lamina; it continues posteriorly into the elongating jaw, and from it come the posterior teeth, which form behind the primary teeth.
True or false- Anterior teeth are more advanced in development than posterior teeth.
True
True or false: Only the newly formed band of dentinal matrix along the pulpal border is uncalcified.
True
True or false: The permanent teeth may function seven to eight times as long as the primary teeth.
True
True or false: the pattern of mineralization closely follows the pattern of matrix deposition.
True
True/false: the posterior molars do not develop until the space is available for them in the posterior jaw area.
True
The stratum intermedium cells assist the _______ in the formation of enamel.
ameloblasts
Short conical processes (Tomes processes) develop at the apical end of the _____ during the _____ stage.
ameloblasts/ secretory
Dentinogenesis ALWAYS PRECEEDES _________.
amelogenesis
As ameloegenesis is completed and _____ is deposited, the matrix begins to mineralize.
amelogenin
The Golgi apparatus appears centrally in the ameloblasts, and the amount of rough endoplasmic reticulum increases in the ____ ____.
apical area
Collagen fiber turnover takes place throughout the ligament, although the highest turnover is in the ____ area and the lowest is in the ____ region.
apical area/ cervical region
The epithelial diaphragm encircles the ____ ____ of the dental pulp during root development.
apical opening
After the enamel organ is differentiated, the dental lamina begins to degenerate by undergoing ______.
autolysis
Dentinogenesis imperfecta is an ____ _____ genetic disorder of tooth development which often makes the teeth susceptible to excessive wear. It can affect the ____ and ____ teeth with an incidence of between 1 in 6000 to 1 in 8000 people.
autosomal dominant/ primary and permanent teeth
Differentiation takes place in the ____ stage, setting the stage for ____ and ____ formation.
bell stage; enamel and dentin
The collagenous dentinal matrix is laid down in increments like ____ or ____, which is indicative of a daily rhythm for hard tissue formation.
bone/enamel
As the walls of the trench increase in height, ___ ___ appear between the teeth to complete the ____.
bony septa/ crypts
As the enamel matrix develops, it forms in continuous rods from the ________ _______ to the surface of the enamel.
dentinoenamel junction
The last of the teeth to develop are the third molars, which develop when?
by 15 years after birth
As each daily increment of predentin forms along the pulpal boundary, the adjacent peripheral increment of predentin formed the previous day ____ and becomes _____.
calcifies /dentin
During the initial bud stage, gradually, as the rounded epithelial bud enlarges, it gains a concave surface, which begins the ____ _____.
cap stage. (the ectodermal then differentiates to become the enamel organ and remain attached to the lamina)
When the odontoblasts are functioning, their nuclei occupy a more basal position in the cell, and the organelles become more evident in the ____ ______.
cell cytoplasm;
Cells of the dental follicle differentiate into ____-____ fibroblasts of the ligament and cementoblasts, which synthesize and secrete _____ on surface of the tooth roots.
collagen-forming/ cementum
The inner enamel epithelium forms the blueprint for the shape of the developing _____.
crown
The site of "initial formation" is at the ____ ____, and as further increments are formed, more odontoblasts are activated along the _____ _____.
cusp tips/dentinoenamel junction
The mesenchymal cells surrounding the teeth are known as ____ _____ or (dental sac).
dental follicle
The mesenchyme forms the dental papilla, which becomes the pulp; the tissue surrounding these two structures is the ______ _______.
dental follicle
As cellular changes result in formation of a mineralized tissue around the central papilla, the papilla then becomes known as the ____ ____.
dental pulp
Current evidence suggest that dentinogenesis imperfecta is caused by a mutation in the gene that produces ____ ______, a substance necessary for the proper mineralization of dentin by the odontoblasts.
dentin sialophosphoprotein (DSPP)
When the outer root sheath cells disperses into small clusters, they move away from the root surface as ____ ____.
epithelial rests
The presence of what, will determine whether a root will be curved or straight, short or long, or single or multiple?
epithelial root sheath
When the crown is completed, the cells in this region of the enamel organ continue to grow, forming a double layer of cells termed the _____ _____ _____, or Hertwig's epithelial root sheath (HERS).
epithelial root sheath
True or false: Because the apical cementum is thicker, it is said to require less cells to maintain vitality.
false- requires "more" cells
True or false: the root sheath originates at the point that enamel deposits begin.
false- where enamel deposits "end"
True or false: the time between enamel matrix deposition and its mineralization is long.
false-short
Cells of the dental papilla are found on close examination to be _____ and appear to be in a delicate reticulum.
fibroblasts
The increased mineral content in enamel is dependent on the removal of ____ and ____.
fluid and protein
Maturation of the ligament occurs when the teeth reach _____ occlusion. At this time, the ___ of fiber bundles increase notably.
functional/density
The roots of multirooted teeth develop in a fashion similar to those of single-rooted teeth until the ____ ____ begins to form.
furcation zone
Amelogenesis imperfect is ____ problem in which the enamel is poorly developed and mineralized. This can result of cellular malfunction resulting in defective enamel matrix formation.
genetic
In radiographs, cusps initially appear separated and are joined together as ____ _____.
growth processes
As the root sheath lengthens, it becomes the architect of the root. The length, curvature, thickness, and number of roots are all dependent on the ____ ____ ____ cells.
inner root sheath
As the formation of the root dentin takes place, cells of the outer root sheath function in the deposition of ______ _____, a thin layer of accellular cementum that covers the ends of the dentinal tubule and seals the root surface and is composed of a ____-____ protein.
intermediate cementum/ keratin-like
Blood vessels appear early in the dental papilla, initially in the central region along with _____ ______ nerve fibers associated w/ these vessels.
postganglion sympathetic
The dentinal matrix is first a meshwork of collagen fibers, but within 24 hours it becomes calcified. It is called ____ before calcification, and _____ after calcification.
predentin/dentin
After the odontoblasts elongate, become predentin and dentin, they form an extracellular matrix of 90% type I collagen fibers and 10% noncollagenous proteins termed _____; After 24 hours, this increment of matrix calcifies and becomes _____.
predentin; dentin
Any prenatal systemic disturbance will affect mineralization of the ___ tooth crowns, whereas "postnatal" disturbances may affect the _____ tooth crowns.
primary /permanent
The hemidesmosome-attachment plaque is developed by the ameloblast, and this stage of plaque formation and attachment is known as the _____ stage of ameloblast function.
protective stage
As the odontoblasts differentiate along the pulpal boundary root dentinogenesis proceeds and the root lengthens. Dentin formation continues from the crown into the root to the apical epithelial diaphragm. In the pulp adjacent to the epithelial diaphragm, cellular proliferation occurs, this is known as the _____ _____ zone.
pulp proliferation zone-(it is believed that this area produces new cells needed for root lengthening)
The ameloblasts shorten and contact the stratum intermedium and other enamel epithelium, which fuse together to form the ____ _____ epithelium. This cellular organic covering remains on the enamel surface until the tooth ____ into the oral cavity.
reduced enamel epithelium/ erupts
The Tomes process of the ameloblasts indents the surface of the enamel; this is because the center of the rod does not form at the same rate as the ___ ____.
rod walls
Dentinogenesis continues until the appropriate ____ ____ is developed. The root then thickens until the apical opening is restricted to approximately __-__ mm, which is sufficient to allow neural and vascular communication between the pulp and the ______.
root length/ 1-3mm / periodontium
As the crown develops, cell proliferation continues at the cervical region or base of the enamel organ, where the inner and outer enamel epithelial cells fuse to form the ____ ____.
root sheath
As the ameloblast completes the matrix deposition phase, its terminal bar apparatus disappears, and the surface enamel becomes _____.
smooth
With the increase in root length, the tooth begins eruptive movements, which provide ____ for further lengthening of the root. The root lengthens at the ____ rate as the tooth eruptive movements occur.
space/ same rate
Because of the high mineral content of enamel, almost all ____ and ____ materials are removed during maturation.
water and organic materials
