Odontogenesis III

Question 1

Hartwig’s epithelial root sheath (HERS)

Answer 1

• Apical development of cervical loop region - OEE and IEE meeting
• Defines root morphology
• Has an inductive influence:
  – Root dentinogenesis
  – Cementogenesis (Indirect)
  – proliferates apically
  – Disintegrates cervically
  Cells are proliferating into the dental papilla as HERS develops

Question 2

Contains 3 layers

Answer 2

Inner investing layer - vascular - become cementoblasts
- Loose connective tissue layer
- Outer layer - lines alveolus with bone

Question 3

Hyaline layer (of Hopewell-smith)

Answer 3

• Between dentine and cementum
• Highly mineralised
• Origin from epithelial cells - enamel matrix proteins
• Induces cementoblast formation
• cements cementum to tooth

Question 4

Cementogenesis

Answer 4

• The formation of cementum, the calcified connective tissue that covers the roots of the teeth, from the root sheath
• two types-acellular (primary) and cellular secondary

Question 5

alveolar bone

Answer 5

As teeth develop bone extends around tooth germ- this is alveolus. It comes from the outer layer of condensed mesenchyme. When the tooth erupts there is resorption of the bone to allow the tooth through

Question 6

Gubernacular canals

Answer 6

Area between apex of deciduous and permanent tooth germ. It is a connective tissue through the alveolus bone to make an eruption canal

Question 7

Periodontal ligament

Answer 7

A connective tissue located between the cementum and alveolar bone, which is part of the periodontium tissue complex participating in the support of the tooth

Question 8

How is root shape determined?

Answer 8

By the HERS and dental papilla. The HERS cells will go into the dental papilla which will determine the number of roots the tooth has