1st year study

Question 1

How is an action potential generated?

Answer 1

1. Resting state
2. Depolarisation: Cell is stimulated and is depolarised to threshold potential. Na+ channels open and Na+ flows into cell at faster rate than K+ leaving the cell (K+ channels slower to open).
3. Repolarisation: : The Na+ channels close and K+ channels finally open, allowing K+ to rapidly diffuse out of the cell (this reestablishes the negative resting membrane potential and even goes past it.
4. Hyperpolarisation: The K+ voltage gated channels close. K+ leak channels and Na+/K+ pump restore the resting membrane potential.

Question 2

How does LA work?

Answer 2

LA works by moving to the inside of the cell, then binding to the ‘sodium channel’ and so blocking the influx of sodium ions. This prevents action potentials from propagating down the axon and means the pain signal will not reach the brain.

Question 3

What does oral mucosa consist of?

Answer 3

• Epithelium
• Lamina propria (papillary & reticular layer)
• Submucosa
• Periosteum

Question 4

What are the layers of oral epithelium?

Answer 4

• Keratinised layer
• Granular cell layer
• Prickle cell layer
• Basal cell layer

Question 5

What cells are present in oral mucosa?

Answer 5

• Keratinocytes
• Melanocytes
• Langerhan’s cells
• Merkel cells

Question 6

What papillae are present on anterior ⅔ of tongue?

Answer 6

• Filiform (no taste buds found)
• Fungiform
• Circumvallate
• Foliate

Question 7

What acini are each of the salivary glands?

Answer 7

• Parotid: serous
• Submandibular: sero-mucous
• Sublingual and minor salivary glands: mucous

Question 8

What are the 3 components of tooth buds?

Answer 8

• Enamel organ
• Dental Papilla
• Dental Follicle

Question 9

What does the enamel organ form into?

Answer 9

Enamel

Question 10

What does the dental papilla turn into?

Answer 10

• Dentine
• Pulp

Question 11

What does dental follicle turn into?

Answer 11

• Periodontal ligament
• Cementum
• Alveolar bone

Question 12

Describe microstructure or dentine

Answer 12

• Odontoblasts are located inside dentine tubules.
• Odontoblasts produce collagen and mineralize collagen matrix with apatite crystallites.

Question 13

Why is dentine adhesion difficult?

Answer 13

Dentine surface is hydrophilic (contains 60% water) and composite resins are hydrophobic.

Question 14

What is smear layer>

Answer 14

After preparation with rotating instruments a smear layer is formed at the dentine surface containing collagen pieces and cutting debris. Smear layer can clog dentinal tubules.

Question 15

What is the role of conditioner?

Answer 15

Removes smear layer, demineralises surface and exposes collagen fibres.

Question 16

What is the role of primer?

Answer 16

Changes collagen from hydrophilic to hydrophobic so bond can move into gaps between collagen.

Question 17

What is the hybrid layer?

Answer 17

Zone in which adhesive resin of bonding agent micromechanically interlocks with dentinal collagen

Question 18

What is 4th, 5th, 6th and 7th gen adhesive?

Answer 18

• 4th gen adhesive: phosphoric acid + primer + bond
• 5th gen adhesive: phosphoric acid etch + combined primer and bond.
• 6th gen adhesive: combined etch and primer + adhesive
• 7th gen adhesive: all in one

Question 19

What happened when conditioned dentine is dried too much vs too little?

Answer 19

• Too dry: exposed collagen fibres collapse (low bond strength and post op sensitivity).
• Too moist: too much water remains, causing reduced dentine bonding of hydrophobic composites.

Question 20

What are dentures made of?

Answer 20

Polymethylmethacrylate

Question 21

What are the main ingredients of a composite resin?

Answer 21

• Matrix (monomers)
• Filler
• Coupling agent (internal interface coupling agent (silane)

Question 22

What are the 2 main components of GIC?

Answer 22

• Weak polymeric acids
• Powdered glasses of basic character

Question 23

What is the role of fuji coat?

Answer 23

Protects the GIC from moisture loss. Moisture loss can lead to cracking and crazing of the cement surface.

Question 24

What happens if there is too much water contamination while GIC is setting?

Answer 24

GIC won’t set properly

Question 25

What causes polymerisation shrinkage of CR?

Answer 25

When you put light on resin it shrinks as chemical bonds are created between molecules, decreasing the distance between them. Material shrinks towards the light source causing leakage. To overcome this you use acid etch so the resin can flow into the pores.

Question 26

What can cause amalgam expansion?

Answer 26

Amalgam expansion possibly caused by saliva contamination during packing (Zinc containing amalgam will expand). Zinc is a scavenger for oxygen. When its reacts with H2O, ZnO is produced as well as H+. Hydrogen gas causes the amalgam to expand with time. This can lead to pulpal pain, post-operative sensitivity and cusp fractures.

Question 27

What are the 2 different types of cementum?

Answer 27

• Acellular cementum- slow deposition, relatively structureless, 1st formed cementum
• Cellular cementum- fast deposition, present in apical ⅓ of root.

Question 28

What are the 5 principle PDL fibres?

Answer 28

1. Alveolar crest fibres
2. Horizontal fibres
3. Oblique fibres
4. Apical fibres
5. Inter-radicular fibres

Question 29

What is enamel histology?

Answer 29

Enamel rod (prism) made up of hydroxyapatite crystals.

Question 30

What is the fluoride concentration in water?

Answer 30

0.6-1.1 mg/L