Op Tech

Question 1

Cavo-surface margin angle

Answer 1

• the angle at the junction between the prepared and unprepared surfaces
• should be between 60-120 degrees, 90 ideally

Question 2

cavity margins

Answer 2

the junction between the walls of the cavity and the unprepared tooth surface

Question 3

line angles

Answer 3

the line formed at the junction between two surfaces within the cavity

Question 4

point angles

Answer 4

the angle formed between three prepared surfaces in the cavity

Question 5

occlusal floor

Answer 5

the surface at the bottom of the cavity, parallel to the occlusal plane, that lies over the pulp

Question 6

gingival floor

Answer 6

the surface at the bottom of the cavity, parallel to the occlusal plane, bound by the gingival margin

Question 7

axial wall

Answer 7

a vertical wall within the cavity that is parallel to the long axis of the tooth

Question 8

pulpal axial wall

Answer 8

axial wall that surrounds the pulpal tissue

Question 9

buccal / lingual axial wall

Answer 9

axial wall that forms the border of the cavity, bounded by the Cavo-surface margin

Question 10

flat plastic

Answer 10

manipulation of shapeable materials ie composite or glass ionomer

Question 11

matrix band

Answer 11

used to rebuild margin walls

Question 12

excavator

Answer 12

removal of caries or thinned enamel, removal of materials

Question 13

tweezers

Answer 13

handling small objects ie wedges

Question 14

mirror

Answer 14

viewing intraorally, tissue retraction

Question 15

Describe the dentine bonding process.

Answer 15

• acid etch applied (35% phosphoric acid), opens tubules by removing smear layer, leaving collagen network, increased wettability
• prime and bond applied, primers hydrophilic end binds to the hydrophilic dentine tubules, the hydrophobic methacrylate binds to the hydrophobic adhesive

Question 16

What is in prime and bond?

Answer 16

HEMA
resin bis-GMA
camphorquinone
acetone

Question 17

What are the principles of caries removal?

Answer 17

1. Identify and removal carious enamel.
2. Remove enamel to identify the extent of caries and the ADJ.
3. Progressively remove caries in dentine, from ADJ and circumferentially deeper.
4. Remove deep caries over the pulp.
5. Modify cavity design, smooth edges, prepare for chosen filling material (ie retentive form = amalgam).
6. Smoothing of internal line and point angles.
7. Smoothing of the Cavo-surafce margins.

Question 18

What are the components of a dental handpiece?

Answer 18

• head (bearings, rotor, chuck, bur, backcap)
• neck
• body
• coupler

Question 19

What are the safe for use checks?

Answer 19

• check the backcap doesn’t rotate anticlockwise
• apply tension to bur to ensure it doesn’t come loose
• apply tension to the coupling to ensure it doesn’t come loose

Question 20

What are the fit for use checks?

Answer 20

• bur rotates freely
• apply lateral tension to the bur
• run device for >5s to ensure regular high pitch noise and bur rotates on its own axis

Question 21

What are the components of composite resin?

Answer 21

• filler particles
• resin
• camphorquinone (photointiator)
• low weight dimethacrylates
• silane coupling agents

Question 22

What is an example of a filler particle in composite resin?

Answer 22

• microfine silica

- quartz

Question 23

What is an example of a resin in composite resin?

Answer 23

bisGMA

Question 24

What is an example of a low weight dimethacrylate in composite resin?

Answer 24

• Triethylene glycol dimethacrylate (TEGDMA)

- adjusts viscosity and reactivity

Question 25

What is silane coupling agent in composite resin?

Answer 25

- allows for an intimate bond between the filler particles and the resin

Question 26

What is DOC?

Answer 26

- depth of cure - typically 2mm - the depth at which the material is at 80% of the hardness of the surface

Question 27

How is polymerisation contraction shrinkage avoided in cavities?

Answer 27

- two opposing surfaces should not be connected by a layer of composite - build in triangular increments

Question 28

What is in the powder component of RMGIC?

Answer 28

- fluoro-alumino-silicate glass - barium glass (radiopacity) - vacuum dried polyacrylic acid - potassium persulphate - ascorbic acid

Question 29

What is in the liquid component of RMGIC?

Answer 29

- HEMA - polyacrylic acid with methacrylate groups - tartaric acid - water - camphorquinone

Question 30

Describe the technique used for taking an impression.

Answer 30

- size check the tray - retract cheek - rotate tray from 90 degrees into the mouth - retract lip and line up the midline with the handle - seat the tray at the posterior and then the anterior - arrange the buccal and labial tissues to ensure proper impression of sulcus Maxillary stand behind Mandibular stand in-front

Question 31

How does temperature affect alginate setting times?

Answer 31

Hot = faster set

Question 32

What makes up the liquid component of GIC?

Answer 32

- polyacrylic acid - tartaric acid - itaconic aci d

Question 33

What makes up the powder component of GIC?

Answer 33

- silica - alumina - various salts (including calcium fluoride, sodium fluoride, aluminium fluoride, and aluminium phosphate)

Question 34

What are the 3 phases of GIC setting reaction?

Answer 34

- dissolution - gelation - hardening

Question 35

Describe the setting reaction of RMGIC.

Answer 35

Dual cure reaction - polymerisation reaction initiated by camphorquinone and light blue cure (initial set) - acid-base reaction as in GIC (over 24 hours) Tri cure reaction - polymerisation reaction initiated by camphorquinone and light blue cure (initial set) - REDOX reaction "dark cure" (5 minutes) - acid-base reaction as in GIC (over 24 hours)

Question 36

What problems does light curing pose?

Answer 36

Safety risk - exothermic reaction (could be damaging to the pulp) - thermal trauma to patient soft tissues if optic rod not placed correctly - ocular damage to operator (omitted by use of safety shields or glasses) Setting - larger increments placed than the DOC - polymerisation contraction shrinkage

Question 37

How do you mix GIC?

Answer 37

- 2 scoops of powder to 2 drops of water - 1 dry side and 1 wet side of spatula - mix one scoop of powder at a time - wipe spatula immediately after mixing

Question 38

How is RMGIC dispensed?

Answer 38

- capsule "popped" - mixed for 8 seconds - silver gun dispenses (fugi) OR - as two pastes, clicked out together and mixed (vitrebond)

Question 39

What are the components of calcium hydroxide cement?

Answer 39

Paste 1 - calcium hydroxide - zinc oxide - zinc stearate - ethyl toluene sulphonamide Paste 2 - glycol salicylate - titanium dioxide - calcium sulphate - calcium tungstate

Question 40

What can calcium hydroxide be used as?

Answer 40

- cavity liner | - pulp cap

Question 41

What is ZOE?

Answer 41

- zinc oxide eugenol cement

Question 42

What is ZOE used for?

Answer 42

- cavity liner / base - temporary restorations - root canal sealer - periodontal dressings

Question 43

How do you mix calcium hydroxide?

Answer 43

- a pea sized amount of base paste is dispensed - a pea sized amount of catalyst is added and the two mixed together until a uniform colour is reached - wipe the spatula clean

Question 44

What is the setting reaction of calcium hydroxide cement?

Answer 44

acid-base reaction

Question 45

What is the setting reaction of ZOE cement?

Answer 45

acid-base reaction, chelation

Question 46

What is the purpose of using dental dam?

Answer 46

- airway protection (!) - field isolation - improved vision

Question 47

What material is used for dental dam?

Answer 47

nitrile

Question 48

What is the purpose of floss ligatures?

Answer 48

- invert the dam into the gingival margin | - creates a good seal