Tooth Whitening

Question 1

List the main extrinsic causes of tooth discoloration

Answer 1

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

Question 2

What are the intrinsic causes of tooth discoloration?

Answer 2

Fluorosis
Tetracycline
Non-vitality (blood products)
Physiological (age changes)
Dental materials (amalgam, root filling materials)
Porphyria
Cystic fibrosis
Thalassemia
Sickle cell anemia
Hyperbilirubinaemia

Question 3

Which genetic/medical conditions cause discolored teeth and what colors result?

Answer 3

Porphyria (red primary teeth)
Cystic fibrosis (grey teeth)
Thalassemia/sickle cell anemia (blue, green or brown teeth)
Hyperbilirubinaemia (green teeth)

Question 4

What are the two types of tooth bleaching?

Answer 4

External vital bleaching and internal non-vital bleaching

Question 5

What is the chemical process behind vital external bleaching?

Answer 5

Discoloration is caused by chemically stable, chromogenic products (long chain organic molecules) within tooth substance. Bleaching oxidizes these compounds into smaller, often non-pigmented molecules. Oxidation can cause ionic exchange in metallic molecules leading to lighter color.

Question 6

What is the active agent in tooth bleaching and how does it work?

Answer 6

Hydrogen peroxide (H₂O₂) is the active agent. It forms an acidic solution in water, breaks down to form water and oxygen, and creates the free radical perhydroxyl (HO₂), which is the active oxidizing agent.

Question 7

What are the main constituents of bleaching gel?

Answer 7

Carbamide peroxide, carbopol, urea, surfactant, pigment dispersers, preservative, flavor, potassium nitrate, calcium phosphate, fluoride

Question 8

What is carbamide peroxide and how does it relate to hydrogen peroxide?

Answer 8

Carbamide peroxide is the active ingredient that breaks down to produce hydrogen peroxide and urea. 10% carbamide peroxide → 3.6% H₂O₂ + 6.4% urea.

Question 9

What is the purpose of carbopol in bleaching gel?

Answer 9

Carbopol is a thickening agent that slows the release of oxygen, increases the viscosity of the gel (so it stays where you put it), and slows diffusion into enamel.

Question 10

What functions do urea and surfactants serve in bleaching gel?

Answer 10

Urea raises pH and stabilizes hydrogen peroxide. Surfactants allow the gel to wet the tooth surface.

Question 11

What is the purpose of potassium nitrate, calcium phosphate, and fluoride in bleaching gel?

Answer 11

Potassium nitrate and calcium phosphate are tooth desensitizing agents. Fluoride prevents erosion and has a desensitizing effect.

Question 12

What factors affect bleaching efficacy?

Answer 12

Time (more time → more effect)
Cleanliness of the tooth surface (cleaner → better)
Concentration of solution (higher concentration → more and quicker effect)
Temperature (higher → quicker effect)

Question 13

What preparations should be made before starting external vital bleaching?

Answer 13

Check patient is dentally fit (any leakage around carious cavity margins will lead to pulpal damage), take an initial shade, agree it with the patient, record it in their notes, and ideally take a photo with a shade guide.

Question 14

What warnings should patients receive before bleaching?

Answer 14

Sensitivity, relapse, restoration color (won’t change), allergy, might not work, compliance with regime is required

Question 15

What are the two types of vital external bleaching?

Answer 15

Chair-side/in-office bleaching and home bleaching

Question 16

Describe the in-office bleaching technique

Answer 16

Thorough cleaning of teeth, rubber dam (or at least gingival mask), apply bleaching gel to tooth, apply heat/light, wash/dry/repeat, takes 30 mins to an hour

Question 17

What is the truth about heat/light/laser use in in-office bleaching?

Answer 17

They are mainly marketing techniques with no evidence of better bleaching results. Light and laser are really just heat sources. They often provide good initial results, but this is mainly due to dehydration and wears off quickly.

Question 18

What is the maximum legal concentration of hydrogen peroxide that can be used for bleaching?

Answer 18

6% hydrogen peroxide (equivalent to 16.7% carbamide peroxide)

Question 19

What characterizes home vital bleaching?

Answer 19

Most common technique, uses 10%-16% carbamide peroxide gel (max 16.7% which equals 6% hydrogen peroxide), patient uses solution at home in custom-made tray, bleaches slowly over several weeks, easy for dentist and patient

Question 20

Describe the technique for making custom trays for home bleaching

Answer 20

Take alginate impressions of teeth, make 0.5mm thick soft, acrylic, vacuum-formed soft splint, should stop short of gingival margin (1mm), include buccal spacer to allow for placement of gel

Question 21

What is the proper home bleaching procedure for patients?

Answer 21

In-surgery: full mouth cleaning/polishing, fit trays and check extension/comfort, provide instruction.

At home: brush and floss teeth, load tray (1mm² dot buccally on each tooth), fit tray in mouth, leave in place for at least 2 hours (preferably overnight)

Question 22

What are the expected results and timeline for home bleaching?

Answer 22

Results are variable, most patients see results within 2-3 days, normally reaches maximum by 3-4 weeks, if no change in 2 weeks it is not going to work

Question 23

What conditions respond well to bleaching?

Answer 23

Age-related darkening/discoloration (yellow/orange responds better than bluish/grey), mild fluorosis, post-smoking cessation

Question 24

How does tetracycline staining respond to bleaching?

Answer 24

Requires prolonged treatment, better results with yellow and brown staining than grey, can take months

Question 25

What are the common problems associated with bleaching?

Answer 25

Sensitivity, wearing off of effect, potential cytotoxicity/mutagenicity, gingival irritation, possible tooth damage, issues with restoration color matching, problems with bonding to tooth after bleaching

Question 26

What do we know about sensitivity during bleaching?

Answer 26

Common (60%+), worse initially, resolves over 2-3 days post-bleaching. Predictors include pre-existing sensitivity, high concentration of bleaching agent, frequency of change, bleaching method, and gingival recession.

Question 27

How long do bleaching results last?

Answer 27

Oxidized chromogens gradually reduce with time, requiring retreatment every 1-3 years (varies by individual)

Question 28

What safety concerns exist for carbamide peroxide and hydrogen peroxide?

Answer 28

No evidence of cytotoxicity/mutagenicity for 10% carbamide peroxide, but high concentration H₂O₂ can cause problems

Question 29

How does bleaching affect dental restorations?

Answer 29

Probably doesn't damage restorations, but teeth bleach while composite doesn't. Patients must be aware of this before treatment. If restorations are changed to match bleached teeth, continued bleaching will be required or fillings will appear too light.

Question 30

Why should restorative procedures be delayed after bleaching?

Answer 30

Residual oxygen from the peroxide remains within the enamel structure initially, which can interfere with bonding. Delay for at least 24 hours post-bleaching, preferably a week.

Question 31

What causes discoloration in non-vital teeth?

Answer 31

Dead pulp leads to bleeding into dentine, blood products diffuse and darken, resulting in grey discoloration

Question 32

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

Answer 32

Indications: non-vital tooth, adequate root canal treatment, no apical pathology Contraindications: heavily restored tooth (better with crown or veneer), staining due to amalgam

Question 33

What are the advantages and risks of internal non-vital bleaching?

Answer 33

Advantages: easy, conservative, patient satisfaction Risks: external cervical resorption due to diffusion of H₂O₂ through dentine into periodontal tissues (particularly with high concentration H₂O₂ and heat, or history of trauma)

Question 34

Describe the technique for internal non-vital bleaching

Answer 34

Record shade prophylaxis apply rubber dam remove filling from access cavity remove GP from pulp chamber and 1mm below amelo-cemental junction place 1mm RMGIC over GP to seal canal remove any very dark dentine etch internal surface with 37% phosphoric acid place 10% carbamide peroxide gel in cavity cover with cotton wool seal with GIC, repeat procedure at weekly intervals

Question 35

How long does internal non-vital bleaching typically take and how long do results last?

Answer 35

Normally takes 3-4 visits; if no change after 4 visits, consider crown/veneer/composite build-up. Results will gradually darken again, requiring retreatment every 4-5 years (variable).

Question 36

What is inside-outside bleaching?

Answer 36

A technique for non-vital RCT'd teeth: remove GP, cover with RMGIC, make bleaching tray with palatal reservoir, place bleach in open access cavity and in tray, replace frequently (every 2-3 hours) over about a week. Patient must wear tray the whole time.

Question 37

What is micro-abrasion and what is it used for?

Answer 37

A combination of erosion (acid) and abrasion (pumice) that removes discoloration limited to the outer layers of enamel. Indications: fluorosis, post-orthodontic demineralization, demineralization with staining, prior to veneering if dark staining is present.

Question 38

Describe the micro-abrasion technique

Answer 38

Clean teeth thoroughly apply rubber dam (seal is very important) mix 18% HCl and pumice apply to teeth gently rub with prophy cup for 5 seconds/tooth wash repeat up to 10 times remove rubber dam polish teeth with fluoride prophy paste apply fluoride gel or varnish

Question 39

What are the advantages and disadvantages of micro-abrasion?

Answer 39

Advantages: quick, easy, no long-term problems (pulpal damage, caries) Disadvantages: acid use, sensitivity, only works for superficial staining, works much better for brown staining than white marks

Question 40

How do HCl and phosphoric acid differ in micro-abrasion?

Answer 40

HCl removes 100 microns of enamel, while phosphoric acid only removes 10 microns. Phosphoric acid is readily available to general dental practitioners but not as effective. Technique: etch first with phosphoric acid for longer (30s) prior to using pumice.

Question 41

What clinical considerations must be addressed before tooth whitening?

Answer 41

An appropriate clinical examination must be carried out, the patient must be free of dental pathology, and medical contraindications must be considered (very rare: glucose-6-phosphate dehydrogenase deficiency, acatalasemia - neither group can metabolize hydrogen peroxide)

Question 42

What are the regulations regarding hydrogen peroxide concentration and age restrictions?

Answer 42

Products containing or releasing between 0.1% and 6% hydrogen peroxide cannot be used on persons under 18 years of age except for disease prevention. Products containing ≤0.1% hydrogen peroxide (including mouth rinse, toothpaste, and whitening products) are considered safe and available on the market.

Question 43

How should tooth whitening products containing between 0.1% and 6% hydrogen peroxide be used?

Answer 43

Exposure should be limited in frequency and duration of application products should only be available through dental professionals (dentist, hygienist therapist, or clinical dental technician) the first cycle of treatment must be supervised, after which the product may be provided for use by the consumer.

Question 44

What are the legal restrictions on higher concentration hydrogen peroxide products?

Answer 44

Concentrations exceeding 6% hydrogen peroxide remain prohibited unless wholly for the purpose of disease prevention. It is a criminal offense to breach these guidelines.

Question 45

What are the consequences of breaching tooth whitening regulations?

Answer 45

Dental professionals using products exceeding 6% for cosmetic purposes face fitness to practice proceedings. Non-registrants providing tooth whitening will be prosecuted by the GDC under the Dentists Act 1984 for illegal practice of dentistry. Non-dentists supplying bleaching products exceeding 6% will be prosecuted by Trading Standards.