Tooth Whitening

Question 1

What are some extrinsic causes of tooth discoloration?

Answer 1

Environmental Factors
Smoking
Tannins (tea, coffee, red wine, Guinness)
Chromogenic bacteria
Chlorhexidine
Iron supplements

Question 2

What are some intrinsic causes of tooth discolouration?

Answer 2

Genetic Factors
Fluorosis
Tetracycline
Non-vitality (blood products)
Physiological (age changes)
Dental materials- amalgam, root filling materials
Porphyria (red primary teeth)
Cystic fibrosis (grey teeth)
Thalassemia, sickle cell anaemia (blue, green or brown teeth)
Hyperbilirubinemia (green teeth)

Question 3

What are the 2 types of tooth bleaching?

Answer 3

External vital bleaching
Internal non-vital bleaching

Question 4

What is external vital bleaching?

Answer 4

Discoloration is caused by the formation of chemically stable, chromogenic products within the tooth substance
These are long chain organic molecules
Bleaching oxidises these compounds
Oxidation can cause ionic change in metallic molecules leading to lighter colour

Question 5

What is the active agent in external bleaching?

Answer 5

Hydrogen peroxide (H2O2)
Forms an acidic solution in water
Breaks down to form water and oxygen
Free radical per hydroxyl is formed. This is the ACTIVE oxidising agent

Question 6

What are the constituents of Bleaching Gel?

Answer 6

Carbamide Peroxide
Carbopol
Urea
Surfactant
Pigment dispersers
Flavour
Potassium Nitrate
Calcium desensitising agents
Fluoride

Question 7

What is carbamide peroxide in bleaching gel?

Answer 7

Active ingredient
Breaks down to produce hydrogen peroxide and urea
10% carbamide peroxide consists of 3.6% of hydrogen peroxide and 6.4% of urea

Question 8

What is Carbopol for in bleaching gel?

Answer 8

Thickening agent
Slows the release of oxygen
Increases the viscosity of the gel- stays where you put it
–Stays on the teeth
–Stays in the tray
Slows diffusion into enamel

Question 9

What is Urea for in bleaching gel?

Answer 9

Increases the pH
Stabilises hydrogen peroxide

Question 10

What are the tooth desensiting agents in bleaching gel?

Answer 10

Potassium nitrate
Calcium phosphate

Question 11

What are the factors affecting bleaching?

Answer 11

Time
-More time gives a greater affect
Cleanliness of the tooth surface
-Cleaner the better
Concentration of solution
-Higher concentration results in a more and quicker effect
Temperature
-Higher, quicker effect of bleaching

Question 12

What is the max strength of hydrogen peroxide?

Answer 12

6%, anything more than this is illegal

Question 13

When should you perform bleaching?

Answer 13

Age related darkening/discolouration
-Yellow/orange discolouration responds best
Mild fluorosis
Post smoking cessation
Tetracycline staining
-Prolonged treatment
-Better with yellow and brown than grey
-Can take months

Question 14

What are some indications and contraindications for internal non-vital bleaching?

Answer 14

Indications
-Non-vital tooth
-Adequate RCT
-No apical path
Contraindications
-Heavily restored teeth (better with crown or veneer)
-Staining due to amalgam

Question 15

What are the risks of internal non-vital bleaching?

Answer 15

External cervical resorption
-Due to diffusion of hydrogen peroxide through dentine into the periodontal tissues
-High concentration hydrogen peroxide and heat

Question 16

What do you need to place over GP when performing internal non-vital bleaching?

Answer 16

1mm RMGIC to seal the canal
Seals dentine and prevents root resorption

Question 17

What is the internal non-vital bleaching technique?

Answer 17

Remove filling from access cavity
Remove GP from pulp chamber and 1mm below amelo-cemental junction
Place 1mm RMGIC over GP
Remove any very dark dentine
Etch the internal surface of the tooth with 37% phosphoric acid
Place 10% carbamide peroxide gel in cavity
Cotton wool over this
Seal with GIC
Repeat procedure at weekly intervals until required shade is achieved or there is no change

Question 18

What does micro-abrasion do?
Indications for this?

Answer 18

Removes discolouration limited to the outer layers of enamel
Combination of erosion (acid) and abrasion (pumice)
Indications
–Fluorosis
–Post orthodontic demineralisation
–Demineralisation with staining
–Prior to veneering if dark staining present