Chapter 5: Embryological Tooth Development Flashcards
When does primary dentition begin to develop?
6th week of intrauterine life
What affects teeth formation?
Risk behaviours such as: tobacco, alcohol, drugs
What causes significant impact on the proper meshing of all pieces?
Any change in calcification, chronology, or eruption sequence
What are the causes of malocclusion?
General, endocrine, genetic factors, cysts, and number abnormalities
What’s responsible for the development of the face and when is it clearly distinguishable?
Primary or primitive processes
4th week of pregnancy
What is the stomodeum (primitive oral cavity) delimited by from the cranial position?
Frontonasal prominence which will lead to the lateral and medial nasal processes
What is the stomodeum (primitive oral cavity) delimited by from both sides?
Maxillary process
What is the stomodeum (primitive oral cavity) delimited by from the caudal position?
Mandibular process
What is the stomodeum (primitive oral cavity) delimited by in the frontal view?
Frontonasal prominence, nasal placode, maxillary process, and mandibular process
What is the stomodeum (primitive oral cavity) delimited by from the lateral view?
Buccopharyngeal membrane
What is the stomodeum separated from the pharynx from?
Buccopharyngeal membrane
- the maxillary processes grow forward and join with the lateral nasal processes
- the mandibular processes begin to merge into a single structure (mandibular depression is filled by the proliferation of mesenchyme)
These statements refer to which week?
5th week
What reduces the size of the mouth opening? And when does it happen?
When the maxillary and mandibular processes merge laterally to stomodeum
6th-7th week
The primitive palate derives from ?
The union and fusion of the medial nasal processes and the maxillary processes
When is the palatal triangle completed and what does it include?
During the 6th week
Includes:
The middle portion of the upper lip
Premaxilar area that will eventually give rise to the alveolar bone which will house the 4 upper incisors
The primary palate consists of a strong band of tissue with an ____ cover and a _____ interior ?
Ectodermal, mesenchymal
Place these statements in the order they occur:
A. Dental lamina form the teeth
B. Mesenchymal condensation
C. Vestibular lamina and dental lamina
D. Ectodermal cells proliferate into the mesenchymal tissue
E. Primary epithelial band
A. 5
B. 2
C. 4
D. 1
E. 3
What allows the separation between the lip and the future alveolar area?
The vestibular lamina (lip furrow)
Initial dental lamina= ___ teeth?
20
Where do the permanent teeth form from?
All except the permanent teeth form from extensions of the dental lamina
The secondary palate is formed from?
Formation of two palatal shelves on the maxillary prominences, elevation of these shelves to a horizontal position and fuse
The shelves also fuse anteriorly upon the primary palatal triangle with the nasal septum that grows downward
The incisive foramen is a ?
Vestige (remnant) of that fusion and is the landmark between the primary and secondary palate
What is the embryological process by which tooth buds form?
Odonto genesis
Teeth develop from 2 embryological tissues which are?
Ectoderm and mesoderm
Ectoderm forms?
Enamel and epithelium
Mesoderm forms?
Dentin, dental pulp, cement, and mesenchyme
5 periods of odontogenesis:
Initiation stage
Proliferation stage
Histodifferentiation stage
Morphodifferentation stage
Apposition/calcification stage
Initiation period is the ?
Bud stage and dental lamina
Proliferation period is the?
Cap stafe
Histodifferentiation period is the?
Early bud stage
Morphodifferentiation period is the ?
Late bud stage
Apposition/calcification period is the ?
Crown stage
What are the ectoderm and mesoderm separated by?
Basement membrane
Dental lamina—> initiation period:
- occurs at which week?
- what happens during?
- 6th week
- thickening of the epithelium that invaginates into the mesoderm by proliferation of the cells of the basal layer
- the dental lamina forms—> tooth germ
Bud stage—>initiation period:
- occurs at which week?
- what happens during?
- 7th-9th week
- cells multiply enter in the underlying connective tissue
- 10 buds develop in each arch
The buds of the permanent teeth, are formed from the? While the permanent molars are ?
the temporary buds
Permanent molars are independent buds.
Fewer buds mean?
Agenesis
Extra buds mean?
Supernumerary
- 9th-11th week
- Epithelial cells proliferate resulting in the formation of tooth germ.
- mesoderm produces the dental papilla which gives rise to the dentin and dental pulp.
- The ectodermal covering the papilla is called the enamel organ since it will produce the future enamel of the tooth.
- the mesenchyme condenses as the dental sac, which later forms the cement, periodontal ligament, and alveolar bone.
- In this period we distinguish the 3 formative elements of the tooth
The 3 formative elements of the tooth are?
Enamel organ or dental organ: enamel.
Dental papilla: dentin and dental pulp.
Dental sac: cement, PDL, and alveolar bone.
4 layers of the enamel organ are?
- IEE
- OEE
- Stellate reticulum
- intermediate reticulum
Shape of OEE? And location?
Cuboidal
In contact with dental sac
Which cells are capable of developing into ameloblasts (that produce enamel)?
IEE
Location of IEE?
In contact with dental papilla
Shape of stellate reticulum? Location?
Polymorphic, between IEE and OEE
Shape of intermediate reticulum? Function?
Squamous
Help ameloblasts produce enamel
Excess initiation and proliferation of thickening, bud, and cap stage causes?
Cysts, odontomas, supernumeraries
Defect in initiation and proliferation of thickening, bud, and cap stage causes?
Agenesis, oligodontia/anodontia
Early bell stage—> histodifferentaion period:
- occurs at which week?
- what happens during?
- 14th week
- Tooth germ cells begin to specialise.
- The tissue inside this bell is the dental papilla.
- The Internal dental epithelium will form the enamel.
- The condensation of the mesodermal tissue will have created the dental sac that will give rise to the cement and the periodontal ligament.
- The enamel organ is still attached to the oral epithelium by the enamel cord (joins the tooth germ to the maxillary epithelium).
- An extension begins to form —> dental lamina of the permanent tooth
Function of the OEE?
Protection
Function of the IEE?
Enamel formation
Function of the intermediate reticulum?
Nutrition of the IEE
Function of the stellate reticulum?
Protection and nutrition
Where is the dental lamina of the permanent tooth located ?
lingually and distally to the primary tooth
What’sthe cause of enamel or dentin structure anomalies?
The disorders of endogenous or exogenous origin that alter the differentiation of the cells that form the dental germ
Late bell stage—> morphodifferentiation period:
- occurs at which week?
- what happens during?
18th week
- The dental germ is independent of the oral epithelium. (Because the enamel cord disintegrated).
- The four layers of the enamel organ are fully differentiated and at the site of the neck of the
future tooth, internal and external epithelium form a vertical handle from which it derives the
tooth root.
- The ectomesenchymal cells of the dental papilla closest to the IEE are differentiated into odontoblasts, that are in charge of the dentin development.
- Cells from the IEE closest to the stellate reticulum (preameloblasts) differentiate into ameloblasts to form enamel
- Simultaneously with this process the central part of the dental papilla will become the pulp.
Enamel forms first in? Then in?
first in the future incisal edges and later in the
future cervical edge
This double cell layer composed by ameloblasts and odontoblasts is named
amelo-dentine or bilaminar membrane
The anomalies suffered by the dental germ during its morphological differentiation, will result in teeth of
abnormal shape and/or size
Any systemic or local disturbance that damages the ameloblasts during the enamel formation
phase can cause an
interruption of the apposition of the matrix, resulting in a hypoplasia of the enamel
Crown stage—> calcification period:
- The calcification starts in the areas that will later correspond to the cusp tip and the incisal edge, followed by concentric layers in different areas.
When is the crown morphology established before or after the apposition and mineralisation?
before the apposition and mineralization of the dental tissues begin.
Calcification is?
precipitation of mineral salts mainly calcium and phosphorus on the previously developed tissue matrix. It consists of layered appositional growth
The enamel of what region will be the last to be formed?
cervical region
Temporary teeth: intrauterine:
• CI: ? week.
• LI: ? week.
• 1st molar: ? week.
• C: ? week.
• 2nd molar: ? week.
• Apical closure takes place between the ? year after the eruption.
• CI: 14 week.
• LI: 16 week.
• 1st molar: 15.5 week.
• C: 17 week.
• 2nd molar: 18 week.
• Apical closure takes place between the 1-1.5 year after the eruption.
- Permanent teeth: postnatal:
• 1st molar: ?
• Central incisor, lower lateral incisor: ?
• Upper lateral incisor: ? year old.
• 1st premolars: ? years old.
• 2nd premolar: ? years old, the lowers sometimes up to ? years old.
• The apical closure of permanent teeth occur about ? and a half years after it’s eruption.
- Permanent teeth: postnatal:
• 1st molar: at birth time
• Central incisor, lower lateral incisor: first months of life
• Upper lateral incisor: 1 year old.
• 1st premolars: 2 years old.
• 2nd premolar: 2.5 years old, the lowers sometimes up to 4-5 years old.
• The apical closure of permanent teeth occur about 3 and a half years after it’s eruption.
Arrange the nolla stages:
A. Crown almost completed
B. 2/3 root completed (the tooth breaks the alveolar process and appears in the mouth)
C. Crypt present
D. Root almost completed
E. 1/3 crown completed
F. Crypt absent
G. 1/3 root completed
H. 2/3 crown completed
I. Initial calcification
J. Crown completed (eruptive period begins)
K. Root apex completed
A. 5
B. 8
C. 1
D. 9
E. 3
F. 0
G. 7
H. 4
I. 2
J. 6
K. 10
When does root formation begin?
After enamel and dentin are well developed
The inner and outer enamel epithelium come together in the ? region and form an epithelial
fold, the epithelial root sheath or Hertwig epithelial root sheath (HERS), which grows into the mesenchyme and begins the formation of the root.
Neck region
What happens to the pulp cavity as the dentin increases?
Gets smaller and becomes a narrow canal for the vessels and nerves to enter to the root
Union between IEE and OEE is?
Hertwigs epithelial root sheath
What produces cementoblasts?
The inner cells of the dental sac
Where do the cementum and enamel meet?
The neck of the tooth
CEJ
Hertwig epithelial root sheath (HERS) disintegrates and its remnants are called?
epithelial rests of Malassez
