Tooth Whitening

Question 1

What are extrinsic causes of tooth discolouration ?

Answer 1

Smoking.
Tannins - tea, coffee, red wine, Guinness.
Chromogenic bacteria.
Chlorhexidine.
Iron supplements.

Question 2

What are intrinsic causes of tooth discolouration ?

Answer 2

Fluorosis.
Tetracycline antibiotics.
Non-vitality.
Physiological age changes.
Dental materials - amalgam, root filling materials.
Medical conditions - porphyria, cystic fibrosis, thalassemia, sickle cell anaemia, hyperbilirubinemia.

Question 3

Porphyria - what tooth colour is this condition associated with ?

Answer 3

Red primary teeth.

Question 4

CF - what tooth colour is this condition associated with ?

Answer 4

Grey teeth.

Question 5

Thalassemia - what tooth colour is this condition associated with ?

Answer 5

Blue, green or brown teeth.

Question 6

Sickle cell anaemia - what tooth colour is this condition associated with ?

Answer 6

Blue, green or brown teeth.

Question 7

Hyperbilirubinemia - what tooth colour is this condition associated with ?

Answer 7

Green teeth.

Question 8

What circumstances should teeth bleaching be considered ?

Answer 8

Age related discolouration.
Mild fluorosis.
Post-smoking cessation.
Tetracycline staining.

Question 9

What discolouration does teeth whitening work best for ?

Answer 9

Yellow or orange (compared to blue/grey).

Question 10

When should external bleaching be carried out vs. internal ?

Answer 10

External - tooth vitality.
Internal - tooth non-vital.

Question 11

What causes discolouration of teeth ?

Answer 11

Formation of chemically stable, chromogenic products (long chain organic molecules) within tooth substance.

Question 12

How does external bleaching work ?

Answer 12

Hydrogen peroxide oxidises long chain organic molecules into smaller molecules (which are not pigmented) and ionic exchange in metallic molecules (leads to lighter colour).

Question 13

What are the components of bleaching gel ?

Answer 13

Carbamide peroxide.
Carbopol.
Urea.
Surfactant.
Pigment dispersers.
Preservatives.
Flavour.
Potassium nitrate.
Calcium phosphate.
Fluoride.

Question 14

What is the function of carbamide peroxide in bleaching gel ?

Answer 14

Active agent - breaks down to produce hydrogen peroxide and urea.

Question 15

What is the function of carbopol in bleaching gel ?

Answer 15

Thickening agent - slows release of oxygen, increases viscosity, slow diffusion in enamel.

Question 16

What is the function of urea in bleaching gel ?

Answer 16

Raises pH and stabilises hydrogen peroxide.

Question 17

What is the function of surfactant in bleaching gel ?

Answer 17

Allows gel to wet tooth surface.

Question 18

What is the function of potassium nitrate and calcium phosphate in bleaching gel ?

Answer 18

Tooth desensitising agents.

Question 19

What is the function of adding fluoride to bleaching gel ?

Answer 19

Prevents erosion.
Desensitising effect.

Question 20

What are 4 factors which will affect bleaching ?

Answer 20

Time - more time, more effect.
Cleanliness of tooth surface - cleaner, better.
Concentration of solution - higher concentration, more and quicker effect.
Temperature - higher, quicker.

Question 21

What warnings should be given to patient before undergoing external bleaching treatment ?

Answer 21

Sensitivity. Relapse. Restoration colour. Allergy. Might not work. Compliance with regime.

Question 22

What problems come with external bleaching treatment ?

Answer 22

Sensitivity. Wears off. Cytotoxicity. Gingival irritation. Tooth damage. Damage to restoration. Problems with bonding to tooth in future.

Question 23

Why does external bleaching pose problems to bonding to tooth in future ?

Answer 23

Remaining oxygen in enamel structure for hydrogen peroxide.

Question 24

What advice should be given to a patient regarding sensitivity post-external bleaching treatment ?

Answer 24

Resolves after 2-3 days.
Likely if pre-existing sensitivity, high conc. of bleaching agent, frequency of change, bleaching method and gingival recession.

Question 25

What percentage of external bleaching gel is given for home treatment ?

Answer 25

10-15% carbamide peroxide gel.

Question 26

What is the maximum legal strength of hydrogen peroxide allowed in external bleaching gels ?

Answer 26

16% hydrogen peroxide i.e. 16.7% carbamide peroxide.

Question 27

How does non-vitality cause tooth discolouration ?

Answer 27

Pulpal necrosis causing bleeding into dentine. Blood products diffuse and darken causing grey discolouration.

Question 28

What are indications for internal non-vital tooth bleaching ?

Answer 28

Non-vital tooth. Adequate RCT. No apical pathology.

Question 29

What are contraindications for internal non-vital tooth bleaching ?

Answer 29

Heavily restored tooth or staining due to amalgam.

Question 30

What are the risks associated with internal non-vital tooth bleaching ?

Answer 30

External cervical resorption due to diffusion of H2O2 through dentine into PD tissues.

Question 31

What % of carbamide peroxide gel is used in internal non-vital tooth bleaching ?

Answer 31

10%.

Question 32

Describe the process of non-vital internal bleaching.

Answer 32

1. Rubber dam. 2. Remove filling from access cavity and GP from pulp chamber to 1mm below ACJ. 3. Place 1mm RMGIC over GP to seal canal and prevent root resorption. 4. Remove dark dentine. 5. Etch internal surface of tooth with 37% phosphoric acid. 6. Place 10% carbamide peroxide gel into cavity with cotton wool over it. 7. Seal with GIC. 8. Repeat weekly for 3-4 visits. 9. Once shade achieved - restore palatally with white GP in pulp chamber and light shade of composite.

Question 33

How often will tooth internally bleached require re-treatment ?

Answer 33

Every 4-5 years.

Question 34

What is the function of micro-abrasion treatment alternative to internal non-vital bleaching ?

Answer 34

Remove discolouration limited to outer layers of enamel using combination of acid (erosion) and pumice (abrasion).

Question 35

What are indications for micro-abrasion ?

Answer 35

Fluorosis. Post-orthodontic demineralisation. Demineralisation with staining. Prior to veneering if dark staining present.

Question 36

What are the advantages of micro-abrasion ?

Answer 36

Quick, easy, no long term pulpal damage, no caries risk.

Question 37

What are the disadvantages of micro-abrasion ?

Answer 37

Acid, sensitivity, only superficial staining.

Question 38

Describe micro-abrasion technique.

Answer 38

1. Rubber dam with seal. 2. Mix 18% HCl and pumice. 3. Apply to all teeth and rub with prophy cup 5 seconds each tooth. 4. Wash and repeat up to 10x. 5. Polish teeth with fluoride prophy paste and apply fluoride varnish. 6. Review 1x month.

Question 39

What legislation is there in relation to tooth whitening ?

Answer 39

Cosmetic Products (Safety Amendment) Regulations 2012.

Question 40

What are the 4 laws in tooth whitening ?

Answer 40

Cannot contain >6% hydrogen peroxide. 0.1-6% hydrogen peroxide cannot be used on <18s. 0.1% hydrogen peroxide products - toothpaste, mouth rinse - can be available on market. 0.1-6% hydrogen peroxide should not be available directly to customer, other than through treatment from a dentist.

Question 41

What are the medical contraindications for tooth whitening ?

Answer 41

Glucose 6-phosphate dehydrogenase deficiency and actalasemia - neither groups can metabolise hydrogen peroxide.