Physical

Question 1

Morphogenetic fields

Answer 1

• A group of cells able to respond to discrete, localised biochemical signals leading to the development of specific morphological structures or organs
• Spatial and temporal extent of the embryonic fields are dynamic, and within the field is a collection of interacting cells out of which a particular organ is formed
• Cells within a given morphogenetic field are constrained
• Specific cellular programming of individual cells in a field is flexible

Question 2

Paracrine and autocrine secretions

Answer 2

paracrine = nearby
autocrine = self

influence activity of adjacent or self-cells (act locally, generally don’t enter bloodstream

e.g., mast cells = paracrine, histamine released and act on adjacent blood vessels; increase vasodilation and permeability

Question 3

Neurohormones

Answer 3

Secreted by specialised neurons (neurosecretory/ neuroendocrine cells rather than glandular epithelial cells) into blood.
Meet definition of hormone as they diffuse into bloodstream and act on target cells.
May also serve as a neurotransmitter or as autocrine/ paracrine messengers
e.g., ADH

Question 4

Hormones

Answer 4

Released from endocrine cells.
Chemical messengers that regulate activity of target cells

Question 5

Endocrine cells

Answer 5

• Secrete hormones into the blood stream that caries them to target cells often distant from the endocrine cells
• Single scattered cells or clumped into glands
• Target cells have the appropriate receptors for endocrine signals making them specificC

Question 6

Characteristics of root caries

Answer 6

• Follows gingival recession
• Often starts over a large area of exposed root
• Is ‘circumferential’: cannot distinguish between proximal, B and L
• Most often seen in older people and those with a dry mouth
• Can spread coronally to undermine enamel
• Teeth at increased risk of fracture

Question 7

Clinical appearance of root caries

Answer 7

If active: soft, yellowish/ light brown
If slow progressing: harder and more darkly stained
If arrested: darkly stained, often almost black

Question 8

Titratable acid

Answer 8

No. of H+ ions available to react related to the chelating effect (calcium brought out and bound to things like juices)

Question 9

Hypersensitivity to heat

Answer 9

1. Heat gradient: expansion/ contraction of dentinal fluid in tubules
2. Pressure gradient
3. Fluid movement
4. Movement stimulates nerve endings
5. Action potential (transduction)
6. Nerve fibres to CNS
7. Pain

Question 10

Types of fissure sealants

Answer 10

Resin-based: good retention, up to 70% survival rate, moisture sensitive if contaminated

GIC/ RMGIC: ‘poorer’ retention = chemical bond to tooth surface, advantageous in moist areas, fluoride release

Question 11

Aprismatic enamel

Answer 11

• Not as highly crystallised structure
• Modified technique for etching: longer
• Often in pits and fissures

Question 12

Diagnosing gingivitis

Answer 12

Local: 10-30% BOP
Generalised: >30% BOP
Less than 10% BOP = periodontal health

Question 13

GIC setting reaction

Answer 13

(acid-base reaction contributes to the setting process)
1. Polyacid attacks glass particles (20-30% glass breaks-down), calcium, strontium, aluminium and fluoride ions are released
2. Precipitation of salts = ‘gelation’ and hardening
3. Maturation phase = acid/ base reaction, continues for a few days

Question 14

Composition of GICs

Answer 14

Glass powder (silicate glass), or glass powder + dried polyacrylic acid

Liquid: polyacrylic acid, water

Other additives: maleic acid (improves shelf life), tartaric acid (helps working time)

Question 15

Unfilled resin on primer

Answer 15

• Chases/ bonds the hydrophobic end of the primer
• Partly enters. the collagen framework and forms a layer on top
• Creates resin tags in dentinal tubules
• Micro mechanical retention with CR on top
• fluid will still come up from tubules: ‘weak zone’

Question 16

Role of primer

Answer 16

• Hydrophobic to facilitate placement of CR on dentine
• HEMA (hydrophobic) is often contained
• Often contains alcohol/ acetone to assist in drying
• Must be evaporated prior to unfilled resin placement
• Either displaces water remaining in collagen framework (wet/ moist bonding), or rehydrates collapsed collagen framework (dry bonding)

Question 17

Wet/ moist vs. dry bonding to dentine with primer

Answer 17

Wet/ moist bonding: primer displaces water remaining in collagen framework
Dry bonding: primer rehydrates collapsed collagen framework

Question 18

Biocompatibility of CR

Answer 18

• Unpolymerised resin is toxic to the pulp
• Occurs when composite: placed in large increments, in a wet environment, exposed to air
• HEMA + water = swelling + breakdown of resin overtime
• Response to gingival tissues: inflammatory response (especially if uncured)