General Pathology Flashcards
What is a primary epithelial band?
It is a horse-shoe shaped thickening of epithelium. It is located at the future maxillary and mandibular arches. It gives rise to dental lamina and vestibular lamina.
What are the five histologically identifiable stages of tooth development?
- Bud stage
- Cap stage
- Bell stage
- Apposition
- Maturation
What occurs in bud stage?
Individual epithelial cells on the deep surface of dental lamina swell up and become visible. Hence why it is called a bud
What occurs in cap stage?
Proliferation of epithelial bud & invagination of the deeper surface of the epithelial bud forms the cap shape. Early histogenesis occurs.
What occurs during bell stage?
Shape has changed and epithelial component shape resembles the final occlusal shape. Enamel organ now has histologically distinct components.
What are 5 main cellular processes in early odontogenesis?
- Initiation
- Proliferation
- Differentiation
- Morphogenesis
- Maturation (all of these process may overlap)
When does initiation of odontogenesis occur?
Between 6 and 7 weeks in utero
What is an epithelial – mesenchymal interaction?
Tooth development involves interaction between epithelial and ectomesenchyme elements. This may involve chemical messengers, direct cell contact or effects of extracellular matrix.
What influences tooth shape during odontogenesis?
Dental papilla
What is the field model of tooth development?
It states that “Factors responsible for tooth development exist in the ectomesenchyme. Distinct overlapping fields for each type of tooth cells within each field express specific genes.”
What is the clone model of tooth development?
It states that: “clone of ectomesenchyme cells programmed early by epithelium to producer teeth of a given pattern”
What happens during the proliferation stage?
Controlled cell growth
What happens during the differentiation stage?
Cells become more specialised
What happens during morphogenesis?
Specific tissue structures develop.
What happens during the maturation stage?
Attainment of adult/final function and size. Complete mineralisation of dental hard tissue.
What is amelogenesis?
It is enamel matrix formation. It starts with laying down of the organic matrix and up to 30% mineralisation. After, organic matrix is broken down and the tooth in mineralised for up to 96%
What are the three stages of lifecycle of an ameloblast?
- Presecretory
- Secretory
- Maturation
What are the steps to differentiation of odontoblasts?
- Siganlling molecules induce the differentiation of odontoblasts from dental papilla cells
- The cells separate from ameloblasts by an acellular zone containing fine collagen fibrils
- Each dental papilla cell divides to two cells: one becomes terminally differentiated odontoblast and the other remains undifferentiated
- The undifferentiated cells are a reservoir for differentiation into odontoblast like cells in case the odontoblasts are lost
What are the steps to formation of mantle dentine?
- Odontoblasts produce the organic matrix
- von Korff’s fibres signal the initial dentin formation (von Korff’s fibres are large collagen fibrils
- Odontoblasts also produce collagen type I oriented parallel to the future DEJ
What is the importance of mantle dentine?
It is dentine that is closest to the enamel and is created by new odontoblasts
What is the vascular supply to the dentine?
During mantle dentinogenesis: it is the ecm beneath the odontoblasts
Durin circumpulpal dentinogenesis: some capillaries aree found between odontoblasts
What is circumpulpal dentine?
It is the dentine that is layed in the middle of the tooth
What are the two patterns of dentine mineralisation?
Globular and linear
When does root development occur?
Root development occurs in late bell stage after crown formation. It also coincides with tooth eruption.
What are the three layers that are involved in root formation?
- Inner layer – adjacent root sheath
- Outer layer – adjacent developing alveolar bone
- Intermediate layer
What are the steps of root formation?
- Cells on the internal layer of the root sheath induce dental papilla cells to differentiate into odontoblasts
- Root sheath fragment occurs after onset of root dentinogenesis
- Dentaal follicle mesenchymal cells differentiate into cementoblasts and start laying down cementum
What are epithelial rests of Malassez?
They are small cells present in the periodontal ligament. They are active in periodontal repair anmd regeneration. They can give rise to odontogenic cysts
With what stage of tooth development do both amelogenesis imperfecta and dentinogenesis imperfecta associate with?
Apposition and maturation stages
What are some of the developmental animalities’ can occur?
- Localised developmental defects of teeth – such as enamel or dentine defects
- Acquired defects – fluorosis
- Morphological abnormalities
- Multisystem genetic disorders – ectodermal dysplasia
What is amelogenesis imperfecta?
It is a genetic condition associated with incorrect coding for enamel matrix proteins like ameloblastin, enamelin and tuftelin. Enamel may appear hypoplastic or hypomineralised or both
What is hypoplastic amelogenesis imperfecta?
It is the lack of matrix formation. It creates pitted, grooved or thin enamel but hard and translucent.
What is hypomature amelogenesis imperfecta?
Soft enamel that is vulnerable for attrition. May appear yellow or brown.
What is hypocalcified amelogenesis imperfecta?
It is normal enamel matrix quantity but poor calcification. Enamel thickness normal at eruption. May occur yellow.
What do we need for diagnosis amelogenesis imperfecta?
- Family history
- Clinical observations
- Radiographs
What are the three main ways humans can have dental abnormalities?
- Genetic
- Non-genetic
- Acquired
