Dental Hard Tissue

Question 1

List the mineralised and 4 non-mineralised dental tissue

Answer 1

Mineralised (hard) tissue 
- Alveolar Bone 
- Cementum
- Dentine 
- Enamel 
Non-mineralised (soft) tissue
- Oral Mucosae
- Dental Pulp 
- Gingivae 
- Periodontal ligaments: can provide stem cells which differentiate into mineralised bone

Question 2

Composition equation for dentine and enamel

Answer 2

70% Inorganic mineral salts + 20% Organic substance + 10% H2O
96-97% Mineral Salts + 3-4% Organic substance

Question 3

Name three main features of dentine tubules.

Answer 3

• stem from odontoblasts cell body
• Hollow, responsible for dentine’s permeability
• S shaped more coronally aka shreger lines/ 1^0 curvature

Question 4

Function of dentine (3)

Answer 4

Vital tissue
Sensitive to stimuli
Act as a shock absorber

Question 5

List the 3 main types of dentine, 1 has 4 more and 3 has 2

Answer 5

Primary: Formed prior to apical completion; more formed rapidly and mineralised than 2o
- Peritubular: located in walls of tubules; highly calcified
- Intratubular: located between tubules; highly calcified
- Mantle: Outermost layer of 1o
- Circumpulpal: located around the pulp, uniform structure except around the edges, bulk of dentine
Secondary: formed post root completion; more slowly formed and less mineralised than 1o
Tertiary: formed as a result of injury; irregular pattern of tubules and produced by local cells in area of trauma/stimulus
- Reactionary: derived from pre-existing dentine
- Reparative: derives from newly odontoblasts (created pulpal progenitor cells)

Question 6

Define these types of dentine…

• Translucent
• Sceloric
• Dead tracks

Answer 6

Translucent: caused as of aging tubules, blocked via peritubular, more pronounced at the root apex

Sclerotic: occlusion/blocking of tubules caused via external stimulus (similar to translucent but linked with stimulus NOT formed by odontoblasts)

Dead tracts: odontoblasts killed by external stimulus; leaving hollow tubules which can then be filled with sclerotic. Appear dark under microscope

Question 7

2 terms that are used as features of dentine.

Answer 7

Lines of Von Ebner (cyclic activity of odontoblasts during dentine formation)
Schreger Liners/primary curvature : tubules following sigmoid route

Question 8

List 4 functions of enamel

Answer 8

Mastication
Aesthetic
Protective
Dissipation of forces

Question 9

Describe the structure of enamel using its 3 main features

Answer 9

A. Enamel Rods (prisms)
Long, thin; extend from dentino-enamel junction to the surface of enamel
In cross section appear like fish scales
Direction of rods (generally) at right angles to the DEJ and tooth surface
In cervical and primary
dentition direction different

B. Rod sheaths
Distinct thin layer peripheral to the rods (under light microscope)
Has different refractive index, stains darker and more acid-resistant than rods
Less calcified and more organic substance like enamel protein (than rods)

C. Inter rod substance (cement)
Rods linked to each other via inter-rod substance
Slightly higher refractive index than the rods
Crystals arranged slightly in different direction to inter-rod region

Question 10

What do the following terms mean…

• Striae of Retzius
• Bands of Hunter and Schreger
• Gnarled Enamel
• Perikymata

Answer 10

Striae of Retzius: Dark lines form DEJ towards surface of tooth, form because of weekly rhythm of enamel production causing structural alteration of rods

Bands of Hunter and Schreger: Optical phenomena caused by changing orientation of adjacent rods

Gnarled Enamel: are like a geological fault, project from the DEJ for a short distance into the enamel contain greater concentration of enamel than the rest of the enamel

Perikymata: Enamel lamella, wave like transverse groves, external incremental lines of retzius, project from DEJ for short distance into enamel - No clinical significance

Question 11

Define the hydrodynamic theory

Answer 11

describes pain transmission through small, rapid movements of fluid that occur within dentinal tubules