Tooth Whitening

Question 1

What are some extrinsic causes of tooth discolouration?

Answer 1

Smoking, tannins, chromogenic bacteria, chlorohexidine, iron supplements

Question 2

What are some intrinsic causes of tooth disocolouration?

Answer 2

Fluorosis
Tetracycline
Non-vitality
Amalgam
Age changes
Porphyria (red primary teeth)

Question 3

What is the molecular action of external vital bleaching?

Answer 3

Oxidisation of long chain organic molecules, resulting in smaller molecules which are often not pigmented

Question 4

What is the active agent in external vital bleaching?

Answer 4

Hydrogen peroxide (free radical per hydroxyl)

Often in bleaching solution as carbamate peroxide -breaks down to give hydrogen and urea (less acidic)

Question 5

4 factors affecting external bleaching?

Answer 5

Time, cleanliness of tooth, concentration of solution , temperature

Question 6

6 warnings for patient before external bleaching

Answer 6

Sensitivity
Relapse
Restoration colour will not change
Allergy
Might not work
Compliance with regime is important

Question 7

Procedure of in office external vital bleaching

Answer 7

Clean teeth
Record initial shade
Place rubber dam/ gingival mask
Apply bleach to tooth
Apply heat/ light (speeds up reaction)
Wash/ dry/ repeat
Takes 30 mins/ 1 hour

Question 8

What is the maximum percentage hydrogen peroxide in home vital bleaching?

Answer 8

6%

Question 9

Describe the process of at home bleaching?

Answer 9

Alguna te impression
0.5mm thick soft splint, stopping 1mm of gingival margin with buccal spacer

Brush and floss teeth
Load tray 1mm dot buccal
Wear for 2hours/ overnight

Question 10

If no results after what period of time should bleaching be stopped?

Answer 10

2 weeks

Question 11

Why does external bleaching wear off?

Answer 11

Oxidised chromogens gradually reduce with time

Question 12

How long should restoration placement be delayed post bleaching?

Answer 12

24 hours/ a week

Question 13

Why is chlorine dioxide not used?

Answer 13

Has a ph of 3, strips enamel
More prone to re staining
Extreme sensitivity

Question 14

What are some indications and contraindications for internal bleaching?

Answer 14

Non-vital tooth
Adequate RCT
No apical pathology

Contraindications- heavily restored tooth/ amalgam staining

Question 15

What is a risk of internal bleaching and the cause of this?

Answer 15

External cervical resorption - due to diffusion of hydrogen peroxide through dentine into periodontal tissues
More common in trauma
Can also be due to heat during bleaching

Question 16

Process of internal bleaching

Answer 16

Record shade
Clean tooth externally
Rubber dam
Remove filling from access cavity
Remove GP from pulp chamber and 1mm below ADJ
place 1mm RMBIC over GP to seal canal
Remove darkened dentine
Etch with 37% phosphoric acid
Place 10% carbamide peroxide gel in cavity
Place cotton wool over this
Seal with GIC
Repeat weekly until required shade is achieved (normally takes 3-4 visits)
Once final shade obtained- place white GP in pulp chamber and restore with light shade of composite

Question 17

How often should internal bleaching be repeated?

Answer 17

4-5 years

Question 18

What is combination bleaching?

Answer 18

Remove GP and cover with RMGIC
make bleaching tray with palatial reservoir
Bleach placed in tray and replaced frequently over a week
Need to wear tray full time

Question 19

What is microabrasion

Answer 19

Combination of erosion and abrasion (acid and pumice) to remove outer layer of enamel
Used in superficial staining - fluoride, post ortho demineralisation, prior to veneer

Question 20

Microabrasion procedure

Answer 20

Clean teeth
Rubber dam
18% HCl and pumice applied to teeth (or 37% phosphoric acid)
Gently rub with prophy cup 5 sec per tooth
Wash
Repeat up to 10x
Remove dam and polish with fluoride prophy paste
Apply fluoride gel/ varnish
Review in a month

Question 21

What is resin infiltration?

Answer 21

Hydrophilic resin impregnating of the porous enamel in the white area,
Changes the refractive index of the white area, making it look like surrounding enamel.

Question 22

What concentration of hydrogen peroxide products are only available through registered dentist?

Answer 22

0.1-6%

Excess of 6% is prohibited - will be prosecuted by Trading standards, face fitness to practice and prosecuted by GDC

Question 23

What percentage of pts experience sensitivity after bleaching?

Answer 23

60%

Question 24

What are some predictors of pt sensitivity post bleaching?

Answer 24

Concentration of hydrogen peroxide
Previous sensitivity
Gingival recession