Oral Anatomy & Histology (Review: Outcome 4)

Question 1

Odontogenesis

Answer 1

The process of tooth development

Question 2

When does tooth development begin?

Answer 2

7th week of embryonic development
Continues until late teens:
- exfoliation of primary dentitions
- development and eruption of permanent teeth

Question 3

Tooth Tissues

Answer 3

• All tooth tissues are specialized forms of connective tissue, except enamel
• Each tooth is the product of 2 tissues that interact during tooth development: Ectoderm & Mesoderm (mesenchyme)
• Enamel (ectoderm)
• Cementum (mesenchyme)
• Dentin (Mesenchyme)
• Pulp (Mesenchyme)

Question 4

General Processes

Answer 4

1. Induction: 1 group of cells directs the development of another group of cells
2. Proliferation: results in an increase of the number of cells
3. Differentiation: when one cell begins to look different from another (cells become more specialized)
4. Morphogenesis: causes a tissue or organ to develop its shape
5. Maturation: creates mature form

Question 5

Stages of Tooth Development

Answer 5

1. Initiation (6-7th week): ectoderm gives rise to the oral epithelium & then to the dental lamina with its dental placodes
2. Bud stage (8th week): growth of the dental placode into a bud shape that penetrates the growing ectomesenchyme
3. Cap stage (9-10th week): future shape of the tooth becomes evident; cells specialized to form the enamel organ
4. Bell stage (11-12th week): differentiation of the enamel organ into a bell stage with 4 cell types and the dental papilla into 2 cell types
5. Apposition (various times): dental tissues secreted in successive layers as a matrix
6. Maturation (various times): dental tissue types fully mineralize to their mature form

Question 6

Epithelial components (ectoderm)

Answer 6

1. Enamel organ - tooth germ becomes organized develops into 4 layers
   - proliferation, differentiation and morphogenesis
   - bell stage

Question 7

Active eruption

Answer 7

The actual vertical movement of the tooth

Question 8

Passive eruption

Answer 8

No actual tooth movement takes place when the gingival tissue recedes (occurs with aging)

Question 9

Nasmyth Membrane

Answer 9

Green-grey residue consists of the fused tissue of the REE, oral epithelium, dental cuticle (placed by ameloblasts on the newly-formed outer enamel surface)

• This residue may form on newly erupted teeth of both dentitions that may leave the teeth extrinsically stained

Question 10

Supra-eruption

Answer 10

This occurs when there is a loss of an opposing tooth
- this condition allows the tooth or teeth to erupt further than normal into the space

• means serious problems in replacement of missing teeth with a partial denture or fixed bridge

Question 11

Ankylosis

Answer 11

The fusion of tooth roots (cementum) to the bony socket (alveolar bone) or to the crown of a permanent tooth. (lack of eruption)

The union of 2 similar or dissimilar hard tissues previously detached but beside each other
- cementum of primary tooth fuses at the cervical line with adjacent bone

Question 12

Ectopic Teeth

Answer 12

Out of place arising or produced at an abnormal site

Cause: lack of harmony in the rate of jaw growth, eruption time, and sizes of teeth