Week 2 - Tooth Development & Anomalies of the Teeth Flashcards
What are the components of the teeth?
Enamel
Dentin
Cementum
Pulp
What are the components of the periodontium?
Gingiva
Periodontal ligament
Cementum
Alveolar bone proper
What are the 6 stages of tooth development?
- Initiation
- Bud stage
- Cap stage
- Bell stage
- Apposition
- Maturation
What occurs during the initiation stage?
Cellular induction
What occurs during the bud stage?
Cellular proliferation
What occurs during the cap stage?
Proliferation, differentiation and morphogenesis
What occurs during the bell stage?
Proliferation, differentiation and morphogenesis
What occurs during the appoisition stage?
Induction and proliferation
What occurs during the maturation stage?
Maturation
What role does the epithelium play during the pre-tooth bud stage of tooth formation?
“instructional role”
What is the fate of the neural crest cells during the pre-tooth bud stage?
Yet to be fully determined
What does the epithelium specify?
The “dental nature” of the mesenchyme
What does the mesenchyme specify?
The tooth type (incisor vs. molar) and nature of the product produced by the epithelium (i.e., enamel matrix)
What is present during the induction stage that occurs at 6-7 weeks?
Oral ectoderm
Neural crest cells
dental lamina
What occurs during the induction stage that occurs at 6-7 weeks?
- ectoderm invaginates into the mesenchyme, and is now called the dental lamina
What is the lamina separated from the surrounding mesenchyme by?
A basement membrane
What makes the transition into dental lamina?
Proliferating oral ectoderm
What stage is this?
And label
Cap stage
Red: dental lamina
Purple: enamel organ
Yellow: outer enamel epithelium
Green: stellate reticulum
Orange: inner enamel epithelium
At what stage can all layers of the enamel organ be differentiated?
Bell stage
What cells make up the O.E.E?
Cuboidal cells
What do O.E.E do?
Protective barrier
What cells make up the I.E.E?
Cuboidal cells
What do the I.E.E differentiate into?
Ameloblasts
What cells make up the stellate reticulum?
Star-shaped cells forming network inside enamel organ
What is the function of the stellate reticulum?
Supportive function in enamel production
What cells make up the stratum intermedium?
Compressed layer of flat cuboidal cells
What is the function of the stratum intermedium?
Supportive function in enamel production
What makes up the dental sac?
Collagen fibers around enamel organ
What does the dental sac differentiate into?
Cementum, PDL, and bone
What do cells of the dental papilla nearest IEE have?
Basement membrane separation
What do the outer cells of the dental papilla differentiate into?
Odontoblasts
What do the inner cells of the dental papilla differentiate into?
Pulp tissue
What is a cervical loop?
Junction of the outer and inner enamel epithelia
What is the cervical loop the site of?
Cemento-enamel junction (CEJ) in the adult tooth (aka cervix)
What is the hertwig’s root sheath?
Fusion and apical extension of the outer and inner enamel epithelia
What does the hertwig’s root sheath determine?
The outline of the root dentin and the number of roots a tooth will have
When is the hertwig’s root sheath removed?
Before the cementum is laid down
Where does enamel formation stop at?
The termination of the enamel organs
What happens when enamel formation stops?
Dentin formation continues, and pushes the tooth occlusally
What does a modification of Hertwig’s root sheath create?
“septa” that divide the pulpal tissue and create multiple roots
When is root length complete?
Not until 1-4 years after the tooth has emerged into the oral cavity
The pulp chamber narrows, and the apical opening constricts
What stage is this and label the colors
Apposition stage
Green: stellate reticulum
Light blue: stratum intermedium: inner enamel epithelium
Purple: peripheral cells of dental papilla
What does the stratum intermedium produce?
Alkaline phosphatase
What do inner enamel epithelium produce?
ameloblasts -> enamel
What do peripheral cells of dental papillae produce?
Odontoblasts -> dentin
What is the first formed dentin?
Mantle dentin
What kind of collagen does mantle dentin contain?
Type I and III collagen
How are mantle dentin collagen fibers in the matrix oriented?
Perpendicular to the DEJ
What stage is this?
Label each color
Apposition stage
Yellow: stratum intermedium
Orange: ameloblasts
Red: enamel
Purple: dentin
Light purple: pre-dentin
Green: odontoblasts
What is occuring during the apposition stage?
Migration of ameloblasts peripherally
Migration of odontoblasts inward
What are actively secreting ameloblasts?
Tall columnar cells
What are inactive (aka reduced) ameloblasts?
Short columnar or elongated cuboidal cells
What happens during the final stage of apposition stage of mineralization?
The reduced ameloblasts with the remaining cells of the outer enamel epithelium, stellate reticulum, and stratum intermedium form a membrane on the surface of the enamel
Termed the PRIMARY CUTICLE (aka Nasmyth’s membrane)
What is anodontia?
Total lack of tooth development
What is hypodontia?
Lack of development of one or more teeth
What is oligodontia?
Lack of formation of six or more teeth (subdivision of hypodontia)
What is hyperdontia?
Development of an increased number of teeth (the additional teeth are termed supernumerary)
What are supernumerary teeth?
Defect that originates during initiation stage that results in development of one or more teeth
*too many dental laminas started to grow
What is the most common manifestation of supernumerary tooth formation?
Mesodens
*between 8 and 9
What is an odontoma?
Originates during the initiation stage and results in multiple small fragments of the structure consisting of dentin, enamel, cementum, or any combination
What is complex odontoma comprised of?
A conglomerate mass of enamel and dentin that bears no anatomic resemblance to a tooth
What are compound odontoma comprised of?
Multiple, small tooth like structures
What is taurodontism?
An enlargement of the body and pulp chamber of multirooted teeth with apical displacement of the bifurcation, i.e., an exceptionally long root trunk with very short roots
What is abnormal root formation due to?
Malfunction in hertwig’s root sheath
What is dilaceration?
Abnormal angulation or bend in the root due to malformation of epithelial root sheath
What is gemination?
Defect that originates during the cap stage of development that results in large single-rooted tooth with one pulp cavity and exhibits “twinning” in crown area
- tooth count is normal when the double tooth is counted as one
What is the difference between gemination and fusion?
Gemintation is when tooth count is normal when the double tooth is counted as one
Fusion is when a double tooth in which the tooth count reveals a missing tooth when the double tooth is counted as one
What is concrescence?
Defect occurring during apposition and maturation stages that results in union of root structure of two or more teeth by cementum
What is tubercle fformation?
Defect occurring during cap stage of development that results in an extra cusp due to effects in enamel organ
What do dentigerous cyts (aka follicular cysts) originate by?
Separation of the dental follicle (dental sac) from the crown of the unerupted tooth.
The cyst is attached at the CEJ
What cyst type comprises of 20% of all jaw cysts?
Dentigerous cyst
What do odontogenic keratocyst (OKC) or keratocystic odontogenic tumors arise from?
Cells rests of the dental lamina
OKC constitutes what percent of odontogenic cysts?
3%-11%
What ages do OKC cysts arise in?
10-40
Where are OKC cysts located?
In mandible but often present as multilocular lesions
What kind of cysts are bone expanding cysts?
OKC
What is the treatment for OKC?
Surgical removal, but has a 30% recurrence rate
What does a cyst wall consist of?
6-8 cell layer of stratified squamous epithelium with parakeratosis at the luminal surface
What is an OKC cyst filled with in the lumen?
Keratin
The presence of inflammation in an OKC causes?
Epithelial proliferation and pallisading of the basal cell layer
what is an ameloblastoma?
Slow growing, locally invasive tumor
What is the most common neoplastic lesion arising from odontgenic epithelium?
Ameloblastoma
What do ameloblastoma lesions have?
Multilocular or “soap bubble” appearancec on radiographs
Ameloblastomas are radio-________
Resistant