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tooth development that takes place in many stages
does odontogenesis have a clear cut beginning or end point between these stages?
what is an example of another physiological process that occurs during the stages of odontogenesis that parallels the odontogenesis stage?
formation of other embronic structures such as the face
what organ in the body has the longest developmental period?
when does primary dentition develop?
during the embryonic and fetal period
when is most of the permanent dentition formed?
during the fetal period
does tooth development continue after birth?
yes, specifically the 2nd and 3rd molars
what is the initiation stage? and when does it take place?
- first stage of tooth development
- takes place during the embryonic period at 6-7th week of prenatal development
what physiological process involved in the intitiation stage?
induction-an interaction between embryonic tissues
__________tissues influence________________tissues, in order for _______________ to occur but the mechanisms are unknown
- initiation of odontogenesis
embryo's primitive mouth
when is the stomodeumlined with ectoderm?
beginning of the 6th week
what does oral epithelium form from?
the outer portion or ectoderm
describe the what the oral epithelium consists of and what it will become.
2 horse-shoe shaped bands of tissue at the surface of the stomodeum which will become the uppr and lower jaws
where did ectomesenchyme form from?
from the ectoderm
what is the ectomesenchyme influenced by?
neural crest cells
what is forming at the same time as the oral epithelium?
ectomesenchyme, forms deep to the forming oral epithelium
what does the basement membrane in teh stomodeum do?
separates the oral epithelium from the ectomesenchyme
when does the dental lamina form?
later portion of 7th week
what process produces the dental lamina layer?
the oral epithelium growing deeper and deeper into the ectomesenchyme
the production of dental lamina starts from the____________and progresses_______________
name 3 developmental disturbances that occur in the initiation stage of tooth development
- ectodermal dysplasia
- supernumerary teeth
what is anodontia?
lack of initiation; absence of single or multiple teeth
where does anodontia most commonly occur?
with permanent maxillary lateral incisors, third molars, and mandibular 2nd premolars
what are some other causes of anodontia besides lack of initiation?
- indocrine dysplasia
- systemic disease
- excessive radiation exposure
what is ectodermal dysplasia?
syndrome associated with anodontia
what is supernumerary teeth?
abnormal initiation leading to the development of extra teeth
where does supernumerary teeth often occur?
- between the maxillary central incisors
- distal to the maxillary 3rd molars
- premolar region of both arches
how do teeth appear in the case of supernumerary teeth?
- smaller than normal-and may be accidently discovered on a radiographic exam
- may or may not be erupted
- may cause crowding
what is the second stage of odontogenesis called?
the bud stage
when does the bud stage take place?
beginning of the 8th week of prenatal development for the primary dentition
what physiological process occurs during the bud stage?
- extensive proliferation or growth of the dental lamina into buds penetrating into the ectomesenchyme
- proliferation of underlying ectomesenchyme
at the end of the proliferation process, both the future mandible and maxillary arches will each have how many tooth buds?
what structure still remains between the bud and the growing mesenchyme throughout proliferation?
a basement membrane
what does each bud eventually develop into?
a tooth germ and its supporting tissues
is there any cellular structure change during the bud stage of tooth development?
what happens to the dental lamina in areas where teeth will not be forming?
it remains thickened and later disintegrates as developing oral mucosa comes to line the oral cavity
name 2 common dental developmental disturbances that occur during the bud stage
what is macrodontia? what causes it?
- abnormal proliferation leading to a single tooth or entire dentition to be larger than normal
- it's hereditary
Is macrodontia a result of splitting or fusion of enamel organs?
What is microdontia? And what causes it?
- abnormal proliferation leading to single tooth or entire dentition developing smaller than normal
- it's hereditary
where does microdontia most commonly occur?
- permanent maxillary lateral incisors (peg laterals)
- permanent 3rd molars (peg molars)
what can complete macro and microdontia be due to?
dysfunction of the pituitary gland
when does the cap stage of tooth development occur?
- during 9th and 10th week of prenatal development
- it is the third stage of tooth development
name the physiological processes that occur in the cap stage
describe proliferation as it pertains to the cap stage of tooth development
it is unequal growth in different parts of the tooth bud, which leads to the formation of a cap shape attached to the dental lamina.
which types of differentiation are active during the cap stage of tooth development?
What is the predominant physoilogical process during the cap stage of tooth development?
what structure is formed from morphogenesis in the cap stage of tooth development?
a primordium of the tooth, or tooth germ
define tooth germ. What will it develop into
- primoridium of tooth which develops with a specific form
- primary dentition
what does the tooth germ consist of?
- enamel organ
- dental papilla
- dental sac
define enamel organ. what will it eventually form?
- depression in the deepest part of the dental lamina forming a cap
- it will form the enamel for outer surface of the tooth
what was the enamel organ originally derived from?
define dental papilla. What will it eventually become?
- mass with in the concavity of the cap of the enamel organ
- it will eventually become the dentin and pulp of tooth
where was the dental papilla originally derived from?
the ectomesenchyme deep to the buds- the ectomesenchyme condensed into a mass within the concavity of the enamel organ
What structure (regarding tooth development) is influenced by neural crest cells?
ectomesenchyme - ectomesenchyme forms dental papilla which will become dentin and pulp, which is the part of your tooth that has NERVES **neural crest cells**
Does a basement membrane still exist between the now enamel organ and the dental papilla?
what does the basement membrane between the enamal organ and the dental papilla eventually become?
the dentinoenamel junction
define dental sac (dental follicle).
the remaining ectomesenchyme that's not the dental papilla, it surrounds the enamel organ
what does the dental sac eventually produce?
- perio ligament
- alveolar bone
what separates the enamal organ and the dental sac?
a basement membrane
when is initiation occuring for anterior teeth of the permanent dentition?
in the 10th week
where does the primoridium for the intially formed permanent teeth (successional dental lamina) appear?
as an extension of the dental lamina into the extomesenchyme lingual to the developing primary tooth germs.
define successional dental lamina.
primoridium of the permanent dentition, that extends from the dental lamin into the ectomesenchyme lingual to the forming of primary tooth germs.
Where do non-succadaneous (permanent molars) teeth develop from?
from a posterior extension of the dental lamina distal to the primary 2nd molar's dental lamina
name 4 common developmental disturbances during the cap stage
- dens in dente
what is dens in dente
enamel organ abnormally invaginates into the dental papilla; usually leave the tooth with a deep lingual pit, which can lead to pulpal exposure and pathology and possible endo therapy
how does dens in dente appear on a radiograph? what causes it?
- appears as a tooth within a tooth
- it has hereditary factors involved
what teeth does dens in dente commonly affect?
permanent maxillary incisors, especially the lateral incisors
what is germination
single tooth germ unsuccessfully attempt to divide into two. which results in single-rooted tooth with common pulp cavity, and the tooth exhibits twining in crown area.
where does germination usually occur?
usually in anterior teeth in either dentition
what causes germination? and what problems can it create?
- can be hereditary
- creates problems with spacing and appearance
what is fusion?
reults from the union of 2 adjacent tooth germs, possibly due to pressure in the area. There are 2 distinct pulp cavities, but enamel, dentin, and pulp are united
where does fusion usually occur?
- in crown area of tooth, bt can involve both crown and root
- occurs in anterior teeth of primary dentition
what are tubercles? And what may they be due to?
- extra cusps or extensions of enamel
- may be due to trauma, pressure, metabolic disease
where are tubercles usually found?
- permanent molars, especilly 3rd molars, but can be found on any tooth
- also lingual extension on the cingulum of permanent maxillary anterior teeth, especially lateral incisors and canines
when does the bell stage of tooth development occur for primary dentition?
between the 11th and 12th week, it is the 4th stage
what physiological processes occur in the bell stage of tooth development?
continuation of the ongoing processes of proliferation, differentiation, and morphogenesis
_____________on all levels occurs to it's furthest extent in the bell stage of tooth development.
what results from the strong differentiation process in the bell stage of tooth development?
4 different types of cells are found in the enamel organ
name the 4 new cell types developed in the bell stage of tooth development.
- inner enamel epithelium
- outer enamel epithelium
- stellate reticulum
- stratum intermedium
what has the cap shape of the enamal organ changed to in the bell stage?
a bell shape
what is happening to the dental sac during the bell stage of tooth development? what will this differentiate into?
- increasing amount of collagen fibers are forming aroung the enamal organ
- cementum, perioligament, and alveolar bone
what is the outer enamel epithelium (OEE)? and what does it serve as?
- outer cuboidal cells of enamel organ
- pretective barrier for enamel organ
what is the stellate reticulum? What is it's function?
- more outer star-shaped cells in many layers, forming a network within the enamel
- it supports the production of the enamel matrix
what is the stratum intermedium? and what is it's function?
- more inner layer of flat to cuboidal cells
- it supports the production of the enamal matrix
what is the inner enamel epithelium (IEE)? and what does it differentiate into?
- innermost tall, columnar cells of enamel organ
- differentiates into ameloblasts, and enamal matrix
during the bell stage of tooth development, what other structure besides the enamel organ is undergoing extensive differentation?
the dental papilla within the concavity of the enamel organ
after extensive differentiation of the dental papilla during the bell stage of tooth development, what two types of tissues does it now consist of?
- outer cells of dental papilla
- inner cells of dental papilla
what are outer cells of dental papilla? and what do they give rise to?
- outer layer of cells of the dental papilla nearest the IEE, there is a basement membrane between these two layers
- it will give rise to odonotoblasts that form the dentin matrix
what will the inner cells of dental papilla differentiate into?
What is the final stage of odontogenesis? And what happens in this stage?
- the enamel, dentin, and cementum are secreted in successive layers
how are the enamel, dentin, and cementum initially secreted?
as a matrix
what is a matrix? And what does it serve for?
extracellular substance that serves as framework for later calcification
many inductions occur in the apposition stage of tooth development. wat tissues do these inductions occur between?
between the ectodermal tissue of the enamal organ and mesenchymal tissues of the dental papilla and dental sac.
what does the basement membrane do for the tissue of enamel organ and mesenchymal tissue?
conveys communication between the tissues, and acts as a boundary
why are interactions between ectodermal tissues and mesenchymal tissues during the apposition stage in tooth development necessary?
for the production of enamel, dentin, and cementum by the proliferation of cellular byproducts
what is maturation in tooth development?
other final stage which is reached when the dental tissues are fully mineralized
name 5 common developmental disturbances that occur in the apposition and maturation stages of tooth development
- enamel dysplasia
- enamel hypoplasia
- enamel hypocalcification
- amelogenesis imperfecta
- dentinogenesis imperfecta
what is enamel dysplasia?
faulty development of the enamel resulting from interference of metabolic processes of ameloblasts. may involve individual areas (localized) or large number of ameloblasts (systematic)
what is enamel hypoplasia?
results from the quantity of enamel matrix; teeth appear pitted and grooved
name and describe two conditions that count as enamal hypoplasia
- hutchinson's incisors-crown has screwdriver shape with notched incisal edge
- mulberry molars-have enamel tubercles on the occlusal surfaces
what is enamel hypcalcification?
disturbance results in the reduction of quality of enamel maturation- teeth appear more opaque, yellower, or browner due to intrinsic staining of enamel
What is amelogenesis imperfecta?
- enamel dysplasia which is hereditary, can affect all teeth of both dentitions
- teeth have very thin enamel portions that chip off or have no enamel at all
- crowns are yellow and composed of dentin
- severe attrition can occur due to chewing
- no treatment required, but may want to place crowns for appearanc and prevent further attrition
what is dentinogenesis imperfecta?
- dentinal dysplasia which may be hereditary
- blue/gray or brown with opalescent sheen
- enamel is normal, but chips off due to lack of dentin support
- results in dentinal crown leading to sever attrition
- no treatment required but may want to place crowns for appearance and further attrition
during what stage do IEE cells grow even more columnar or elongate?
when IEE cells elongate and grow more columnar, what are they differentiating into?
describe repolarization in regards to the IEE cells growing more columnar
the nuclei of all the cells move away from the center and position themselves farthest away from the basement membrane
what do the preameloblasts eventually differentiate into? And what do preameloblasts induce?
- differentiate into cells secreting the enamel matrix
- induce dental papilla cells to differentiate
when are the outer cells of the dental papilla induced to differentiate into odontoblasts? Who induces them?
- after the IEE differentiates into preameloblasts
- preameloblasts induce them
does repolarization occur in the dental papilla cells? If so, describe.
- the nuclei move away from the center to the position farthest from the basement membrane, they are in a mirror image with the repolarized preameloblasts.
what is dentinogenesis? And when does it happen?
- production of the dentin matrix (predentin) on the odontoblast side of the basement membrane
- it occurs after the odontoblasts have undergone repolarization
why is the dentin layer slightly thicker than the corresponding layer of enamel matrix?
because odontoblasts start their secretory activity before the enamel matrix production begins
when does the basement membrane between preameloblasts and odontoblasts disintegrate? And why does it do so?
- after the differentiation of odontoblasts and formation of predentin
- it allows the preamaloblasts to come in contact with the new formed predentin, and induces preameloblasts to differentiate into ameloblasts
where to ameloblasts begin amelogenesis (apposition of enamel matrix)?
on their side of the now disintegrating basement membrane
what is amelogenesis?
apposition of enamal matrix
define Tome's process
a tapered portion of each ameloblast facing the disentegrating basement layer which secretes enamel matrix
what is the dentinoenamel junction? And it forms as a result of what?
- the inner junction between the dentin and enamel tissues
- as a result of the mineralization of the disintegrating basement membrane and joining of the dentin and enamel matrixes
define odontoblast process
attached cellular extensions in the length of the predentin left by the odontoblasts
what are the odontoblast processes contained in?
maturation of enamel and dentin occur___________and in different___________
where do cell bodies of odontoblasts end up?
remain within pulp tissue
where do cell bodies of ameloblasts end up?
involved in eruption and mineralization process, but are lost after eruption
when do the processes of root development occur?
after the crown is completely shaped and the tooth is beginning to erupt into the oral cavity
What structure is responsible for root development?
what type of tissue does the cervical loop consist of?
only inner and outer enamel epithelium
describe growth of the cervical loop
it continues to grow deeper into the surrounding ectomesenchyme of the dental sac, elongating and moving away from the newly completed crown, enclosing more of dental papilla tissue
what forms from the deeper growth of the cervical loop?
Hertwig's epithelial root sheath
what is the function of Hertwig's epithelial root sheath?
functions to shape the root/roots and induce dentin formation in the root so it is continous with coronal dentin
true or false. Root dentin forms in the same manner as crown dentin. dental papilla is induced to differentiate and become odontoblasts
howcome there is no enamel in the roots?
it is due to the absence of intermediate layers (stellate reticulum and stratum intermedium) HERS induces odontoblastic differentiation, but fails to differentiate into enamel forming ameloblasts
in roots where does dentinogenesis begin? and what is formed as a result?
- in the root
- predentin is formed from it
what happens to the basement membrane and HERS sheath when root formation is completed?
define epithelial rests of malessez
HERS roog sheath disintegrates and may become these groups of epithelial cells located in the mature perio ligament which may become cysitc and cause future problems
name and describe a developmental disturbance that may occur during root development
what are enamel pearls?
misplaced ameloblasts migrating to the root area abnormally forming enamel on root surfaces
how do enamel pearls appear on radiographs? What can they be confused as? And can they be removed?
- appear radiopaque
- be confused as calculus
apposition of cementum occurs when HERS disintegrates allowing undifferentiated cells of the dental sac to come into contact with the newly formed surface of root dentin, inducing these cells to become immature cementoblasts
what do cementoblasts do?
move to cover the root dentin laying down cementum matrix known as cementoid
what are cementocytes?
cementoblasts entrapped in cementum
what is cementum?
matrued, calcified cementoid surrounding the cementocytes
what is pulp made from?
central cells of the dental papilla, it is surrounded by the new dentin
what is a developmental disturbance in cementum and pulp formation?
what is concrescence?
- excess cementum formation; union of the root structure of two or more teeth thru the cementum only
- teeth involved originally separate, but join as a result of excessive cementum deposition on one or more teeth after eruption
where does concrescence usually occur? And what may be the cause?
- in permanent maxillary molars
- cause may be traumatic injury or crowding of teeth during apposition and maturation stage
what do the periodontal ligament and alveolar bone develop from?
- ectomesenchyme from denal sac forms the PDL
- ectomesenchyme begins to mineralize and form the aveoli of the alveolar bone surrounding the PDL
what are collogen fibers? And what is their function?
- they are formed and immediately organized into fiber bundles of PDL
- the ends of these fibers insert into the outer portion of the cementum and the surrounding alveolar bone for tooth support
define root trunk
structure where all multirooted teeth originate from, it is a single root
what causes the root trunk to divide?
differential growth in HERS
what are 3 developmental disturbances during root formation?
- accessory roots
what is dilaceration?
distorted roots or crown angulation in a formed tooth; it results from distortion of HERS caused by injury or pressure.
what is flexion?
deviation or bend restricted to only the root portion of the tooth-may be a result from trauma to developing tooth
what are accessory roots?
extra roots or supernumerary roots; may be due to trauma, injury, or pressure affecting HERS
where do disturbances in root formations usually occur?
in permanent third molars
define active eruption of teeth
actual vertical movement of the teeth
define passive eruption
occurs as we age as gingival recedes, no actual tooth movement occurs
do mandibular or maxillary teeth passively erupt first?
true or false. teeth in both jaw bons errupt in pairs
do permanent teeth usually errupt in girls or boys first?
abou what age to primary central incisors errupt?
6 1/2 -8 months
about what age do primary lateral incisors errupt?
about what age to first molars errupt?
about what age to primary canines usually errupt
about what age do second primary molars usually errupt
define reduced enamel epithelium
it is layers of the enamel organ that are compressed and overly the new enamel surface
what happens between the REE and oral epithelium to allow for the eruption process?
they fuse togethe
what process causes 'teething'?
enzymes from REE disintegrate the central portion of the fused tissue, leaving an epithelial tunnel for the toothe to erupt through into the surroundingn oral epitheliaum of the oral cavity
define Nasmyth's membrane
residue formed on newly erupted tooth consisting of the fused tissue of the REE and oral epithelium as well as the dental cuticle placed by ameloblasts on new enamel. it is easily removeable
absorb the alveolar bone between primary and permanent teeth during eruption
cause resorption or removal of portions of the primary root of dentin and cementum as well as small protions of the enamel crown
why is it important to keep primary teeth as long as possible?
they serve as place holders for permanent teeth
when do the permanent mandilbular central incisors usually errupt?
when do the permanent mandibular lateral incisors usually errupt? maxillary?
when do the permanent mandibular canines usually errupt? Maxllary?
when do the permanent premolars usually errupt?
when do the permanent 1st molars usually errupt?
when do the permanent 2nd molars usually errupt?
when do the permanent 3rd molars usually errupt?
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