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
proliferation
differentiation
morphogenesis
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?
cytodifferentiation
histodifferentiation
morphodifferentiation
What is the predominant physoilogical process during the cap stage of tooth development?
morphogenesis
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?
the ectoderm
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?
yes
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?
peridontium:
perio ligament
cementum
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
germination
fusion
tubercles
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.
differentiation
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?
pulp tissue
What is the final stage of odontogenesis? And what happens in this stage?
Apposition
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?
bell stage
when IEE cells elongate and grow more columnar, what are they differentiating into?
pre-ameloblasts
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.
Yes
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?
dentinal tubule
maturation of enamel and dentin occur___________and in different___________
later
processes
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?
cervical loop
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
true
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?
they disintegrate
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
enamel pearls
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
no
define cementogenesis
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?
concrescence
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?
dilaceration
flexion
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?
mandibular
true or false. teeth in both jaw bons errupt in pairs
true
do permanent teeth usually errupt in girls or boys first?
girls
abou what age to primary central incisors errupt?
6 1/2 -8 months
about what age do primary lateral incisors errupt?
7-9 months
about what age to first molars errupt?
12-16 months
about what age to primary canines usually errupt
6-21 months
about what age do second primary molars usually errupt
21-30 months
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
define osteoclast
absorb the alveolar bone between primary and permanent teeth during eruption
odonoclasts
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?
maxillary
6-7 yrs
7-8 yrs
when do the permanent mandibular lateral incisors usually errupt? maxillary?
7-8 yrs
8-9 yrs
when do the permanent mandibular canines usually errupt? Maxllary?
