Head and Neck I B Flashcards
What are the 2 forms of dentition in domestic mammals?
Deciduous
Permanent
- Known as Diphyodonts
What do brachyodont teeth have?
Crown, root and a narrowed neck at the fum line between crown and root
Explain hypsodont structure?
Body and a short root. The body protrudes above gum and has a long portion that is also embedded
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What inititates tooth development?
Interaction between ectoderm of dental lamina and underlying neural crest-derived mesenchyme
What occurs along the length of dental lamina?
Ectodermal projections named dental buds push into mesenchyme
What occurs to dental buds as they push into mesenchyme?
Become cap-shaped. Inner and outer layers are separated by a stellate reticulum.
What makes up dental papilla?
Mesenchyme beneath cap
What occurs as cap grows into mesenchyme?
Becomes bell-shaped (referred to as enamel organ
Where do buds of permanent teeth intitiate from
Cord of cells
What occurs to cord connection between surface epithelium and bell-shaped developing tooth?
Atrophies
How do ameloblasts come to be?
Reticular cells induce epithelial cells in inner layer of enamel organ to become ameloblasts
What do underlying mesenchymal cells of dental papilla develop into to?
Tall columnar odontoblasts
What forms enamel knot?
Small group of ectodermal cells in inner epithelial layer of enamel organ (near apex of papilla) will form a clump of non-dividing cells called the enamel knot
What does the enamel knot specify?
Site of cusp formation
What do enamel knots act as?
A signalling center to regulate tooth shape
What are key growth factors produced by enamel knots to stimulate growth of the enamel organ?
Fibroblast Growth Factor-4
Bone Morphogenetic Protein - 2 and 4
What extends down the sides and base of the developing crown?
Ameloblasts
What produces pedentin at tip of papilla?
Odontoblasts while ameloblasts extend down sides and base of developing crown
What does core of the dental papilla become?
Pulp cavity of tooth
What does dentin do to ameloblasts?
Dentin induces ameloblasts to produce more enamel
What does the base of enamel organ mark out?
Junction of crown and root of tooth
What forms from the extensions of inner and outer layers of enamel organ?
A tube-like epthelial root sheath within the mesenchyme
When does shaping of tooth crown occur?
Occurs as dentin and enamel are formed - proceeding from apex to base of enamel organ
WHat do the inner cells of the dental sac differentitate into?
Inner cells differentiate into cementoblasts that produce cementum
What cementocytes?
Cementoblasts which become entrapped within their matrix
What forms from outer layer of dental sac?
Osteoblasts
- produce bone that will help anchor teeth to jaw
What does the middle layer of dental sac become?
Periodontal ligament
When does enamel production stop?
When crown is formed
- leftover enamel organ is shed
How long to odontoblasts remain?
Throughout life of tooth and produce dentin
What is anodontia?
Absence of teeth - rare in domestic animals
How does anodontia occur?
Failure of either dental lamina or dental papillae to develop and induce tooth development
What is oligodontia?
Polyodontia?
Oligodontia - reduced tooth number
Polyodontia - excessive teeth
What causes for delayed shedding of deciduous teeth in dogs?
Secondary to failure of the periodontal ligament to detach from deciduous tooth.
What causes enamel lesions?
Due to malnutrition, infections
