discolouration

Question 1

What should the pre-op records include for all discoloured teeth?

Answer 1

Clinical photos
Shade - of defect and background of tooth
Sensibility testing
Diagram of defect
Radiographs if clinically indicated
Patient assessment

Question 2

What are the treatment options for discoloured teeth?

Answer 2

Do nothing
Enamel microabrasion
Bleaching
Resin infiltration
Localised composite restoration
Veneers

Question 3

What is microabrasion?

Answer 3

The removal of the surface layer of opaque enamel

Question 4

Name 3 advantages of microabrasion

Answer 4

Any from:
- easy to perform
- consertative
- inexpensive
- results are permanent
- minimal subsequent maintenance

Question 5

Name 3 disadvantages of microabrasion

Answer 5

Any from:
- removes enamel, causing sensitivity and teeth may be susceptible to more staining
- HCl is caustic
- must be done in dental surgery by dentist
- production of outcome is difficult, teeth may become more yellow

Question 6

Describe the clinical technique prior to microabrasion

Answer 6

1. PPE
2. Clean teeth with pumice and water
3. Soft tissue protection with petroleum jelly
4. Rubber dam
5. Sodium bicarbonate guard for gingival protection

Question 7

Describe the clinical technique of microabrasion

Answer 7

HCl pumice slurry used in slowly rotating rubber cups for 5 seconds on each tooth
Maximum application is 10x of 5 second applications
Wash directly into aspirador after every application, review colour and shape
White fluoride varnish is then applied and polish with fine so-flex discs

Question 8

How much enamel does 10x 5 seconds HCl pumice microabrasion remove?

Answer 8

100 microns

Question 9

What are the different bleaching options?

Answer 9

Vital bleaching (external vital bleaching) - chairside or night guard at home
Non-vital bleaching (internal non-vital bleaching) - inside out technique or walking bleach technique

Question 10

What strength bleach is used in vital bleaching?

Answer 10

15-38% hydrogen peroxide
Equivalent to 75% carbamide peroxide - for chairside
Night guard - 10% carbamide peroxide

Question 11

List the patient instructions for night guard vital bleaching

Answer 11

Brush teeth thoroughly
Apply gel to the tray
Set over teeth and press down
Remove excess
Rinse gently, do not swallow
Wear overnight (or for at least two hours)
Remove tray and rinse with cold water
Sensitive toothpaste may be required
Timescale approx 3-6 weeks, keep going until acceptable colour
Side effects include sensitivity and gingival irritation

Question 12

Name 3 advantages of non-vital bleaching

Answer 12

Any from:
- tooth conserving
- original tooth morphology
- gingival tissues not irritated
- adolescent gingival level not a restorative consideration
- no lab assistance

Question 13

What percentage HCl is used for microabrasion

Answer 13

18%

Question 14

What indicates a tooth is viable for non-vital bleaching?

Answer 14

Must have adequate root filling - no clinical or radiological disease
Anterior teeth without large restorations
Discolouration isn’t due to amalgam, fluorosis or tetracycline

Question 15

Describe the technique for non-vital bleaching?

Answer 15

Root filling removed to below CEJ
Clean with ultrasonic
Place bleaching agent on cotton wool
Cover with dry cotton wool
Seal with GIC/RMGIC
Ideally no more than 2 weeks between appointments
If no change after 3-4 appointments then stop

Question 16

Describe combination (inside out) bleaching

Answer 16

Access cavity of tooth open and patient given custom mouth guard
Patient applies bleaching agent to back of tooth and tray
Worn all the time except eating and cleaning
Gel changed every 2 hours or so except during the night

Question 17

How is the tooth restored after non vital bleaching?

Answer 17

Non-setting CaOH for 2 weeks, seal in with GIC, then either:
- white GP and composite resin, allows to re-bleach
- incrementally cured composite - cannot re-bleach but tooth will be stronger

Question 18

Name 3 complications of non-vital bleaching?

Answer 18

Any from:
- external cervical resorption
- spillage of bleaching agents
- failure to bleach
- overbleach
- brittleness of tooth crown

Question 19

What is the brand name for resin infiltration?

Answer 19

ICON

Question 20

Name 4 factors the decision to reduce enamel for a veneer depend on

Answer 20

Any from:
- aesthetics
- relative tooth position
- whether masking dark stains
- age
- psyche
- plaque removal

Question 21

What is the advantage and disadvantage of reducing the enamel for a veneer

Answer 21

Reducing enamel increases plaque retention at the gingival margin, especially if the patient has poor OH
Bond strength to composite is increased

Question 22

How much enamel is removed with prophy with toothpaste?

Answer 22

5-10 microns

Question 23

How much enamel is removed with prophy with pumice?

Answer 23

5-50 microns

Question 24

How much enamel is removed with ortho bracket bonding?

Answer 24

5-50 microns

Question 25

How much enamel is removed in acid etching?

Answer 25

10 microns

Question 26

Why are sandpaper discs used after microabrasion?

Answer 26

SEM shows a prismless layer of surface enamel
This changes the optical properties of the enamel so the areas of intrinsic discolouration become less perceptible

Question 27

How is 10% carbamide peroxide broken down?

Answer 27

3% hydrogen peroxide and 7% urea
Catalases and peroxidases break this down further to water, ammonia and carbon dioxide

Question 28

Describe how resin infiltration works

Answer 28

Infiltration of enamel lesions with low-viscosity light curing resins
Surface layer is eroded, lesion desiccated and a resin infiltrant is applied
Resin penetrates lesion driven by capillary forces
Infiltrated lesions lose their discoloured appearance and look similar to sound enamel