histology

Question 1

composition of enamel

Answer 1

96% inorganic 1% organic 3% water

Question 2

structure of enamel

Answer 2

enamel prisms(rods)
-(fish shaped)
made up of enamel crystallites

Question 3

Brown striae of Retzius

Answer 3

Brown lines indicating variations in enamel production / deposition. Brown lines run from ADJ to enamel surface

Question 4

Neonatal line

Answer 4

Line that marks the disruption in amelogenesis at time of birth.

Question 5

Hunter-Schreger Bands

Answer 5

Broad dark and light bands (viewed under light microscope) which run from ADJ into enamel (approx two 3rds into enamel)

Question 6

Enamel spindles

Answer 6

Dentinal tubules extend into enamel

Question 7

Lamellae

Answer 7

Sheet-like faults that run vertically through entire thickness of enamel.

Question 8

Enamel tufts

Answer 8

Pieces of incomplete mineralised enamel, extend from ADJ following direction of prisms.

Question 9

Amelo-dentinal junction

Answer 9

Enamel / dentine interface. Scalloped appearance.

Question 10

Dentine 
PHYSICAL PROPERTIES (4)

Answer 10

Pale yellow in colour

Harder than bone and cementum, softer than enamel

Greater compressive / tensile strength than enamel.

Traversed by tubules therefore easily permeable

Question 11

dentine composition

Answer 11

70% Inorganic material

20% Organic material

10% Water

Question 12

Dentinal tubules

Answer 12

Tubules run in parallel fashion
Tubules run from pulp to amelo-dentinal junction following a ‘double curved’ course.
Each tubule has an odontoblast process

Question 13

PHYSICAL PROPERTIES of enamel

Answer 13

Bluish white colour
Appears yellow-white due to underlying dentine
Semi-translucent
Crystalline material ( hydroxyapatite)
Hardest tissue in body
Low tensile strength.
Properties of enamel vary across tooth surface

Question 14

Reparative dentine (irregular secondary)

Answer 14

Laid down at pulpal interface of dentine in response to external stimuli

Question 15

Peritubular dentine

Answer 15

Highly mineralised dentine within dentinal tubule (furred pipe!)

Question 16

Sclerotic dentine (translucent dentine)

Answer 16

Peritubular dentine increases with age and sometimes tubules can become entirely obliterated

Question 17

Interglobular dentine

Answer 17

Remaining areas of unmineralised dentine

Question 18

Incremental lines (Contour lines of Owen)

Answer 18

Lines in dentine seen when there has been a disruption in dentinogenesis.

Question 19

Granular layer of Tomes

Answer 19

Granular dentine found in root dentine directly under cementum (thin layer).

Question 20

Dead Tract

Answer 20

Empty dentinal tubule due to necrosis of the tubule once the odontoblast process is destroyed (brought on by severe stimuli).

Question 21

changes to dentine

Answer 21

With age-more dentine forms (secondary dentine)
This reduces size of pulp chamber
Diameter of tubules reduces.
Tubules may become obliterated- dentine becomes more translucent (sclerotic dentine)

Question 22

dental pulp

Answer 22

Surrounded by dentine.
Contained in a rigid
compartment.
Soft vascular tissue.

Question 23

FUNCTIONS (5)

dental pulp

Answer 23

Provides nutrients to odontoblasts.
Sensory organ.
Responds to stimuli (caries/attrition) inducing the deposition of reparative or reactionary dentine.
Mobilises defence cells when invaded by bacteria.
Thought to play a role in tooth eruption.

Question 24

dental pulp

SHAPE AND FORM (6)

Answer 24

Follows the shape of the outer surface of tooth.
Pulp horns under cusps.
Pulp chamber in crown.
Root canals into root.
Number of root canals varies.
Foramen or foramina at root apex.

Question 25

dental pulp
CELLULAR STRUCTURE (4)

Answer 25

Odontoblasts.
Basal layer of Weil.
Fibroblasts.
Histocytes (fixed macrophages)- defence cells.

Question 26

dental pulp
INTERCELLULAR SUBSTANCE
(4)

Answer 26

Amorphous ground substance-gelatinous (gives pulp shape).
Blood and lymph vessels.
Nerves.
Collagen fibres-support to pulpal tissue.

Question 27

dental pulp

AGE CHANGES

Answer 27

Reduction in volume due to increase in dentine (secondary dentine).
More collagen.
Reduced cellular content.
Reduced nerve supply (less sensitivity).
Pulp stones (areas of irregular calcification/sclerosis).

Question 28

CEMENTUM properties

Answer 28

Pale yellow
Calcified tissue covering root dentine
Softer than dentine
Easily worn away.
Thickness varies-thickest apical third thinnest cervically

Question 29

CHEMICAL COMPOSITION

cementum

Answer 29

65% inorganic

23% organic

12% water

Question 30

STRUCTURE

cementum

Answer 30

Similar to bone
Can be classified in presence or absence of cells
Accellular cementum
Cellular cementum

Question 31

ACCELLULAR CEMENTUM

Answer 31

First to form (immediate cementum)
Covers root dentine from CEJ to near root apex.
Does not contain cells

Question 32

cellular cementum

Answer 32

Thin layer increasing in width in the apical third of tooth
Secondary cementum
Deposited throughout life.
Cementoblasts become embedded in cementum matrix during development (these inactive cells are known as cementocytes)

Question 33

Functional changes to cementum

Answer 33

throughout life cementum continues to form and the attachment of the perio fibres can alter depending on the functional needs of the tooth.

Question 34

Resorption of cementum

Answer 34

Can occur due to ortho/exessive masticatory stress.

Question 35

Hypercementosis

Answer 35

Increased thickening of cellular cementum.

Question 36

Ankylosis

Answer 36

Cementum of tooth is fused with alveolar bone of tooth socket.

Question 37

Concrescence

Answer 37

Term used when 2 teeth are fused by their cementum.

Question 38

FUNCTIONS
periodontal ligament (7)

Answer 38

Support
Protects against excessive forces
Prevents damage to blood and nerves at root apex
Maintains functional position-keeps teeth in contact/ prevents drifting or tilting
Sensors provide proprioceptive input
Provides nutrients to cementoblasts.
Continually changes-cells, for maintenance and repair of alveolar bone and cementum