Tooth whitening

Question 1

Discuss the difference between ‘bleaching’ and ‘tooth whitening’

Answer 1

• “Bleaching” is permitted to be used only when the teeth can be whitened beyond their natural color. Typically hydrogen peroxide or carbamide peroxide (1/3 of the effect of H2O2)
• The term “whitening,” on the other hand, refers to restoring a tooth’s surface color by removing dirt and debris. So any product that cleans (like a toothpaste) is considered a whitener.

Question 2

Describe the mechanisms of action for hydrogen peroxide

Answer 2

• Peroxide solutions flow freely through enamel and dentine due to low molecular weight of H2O2 molecule
• From the H2O2 , free radicals are generated– catalyzed by water, light, heat, chemical etc. (H2O2 degrades to H2O and O)
• Free radicals can “oxidize some of the larger organic unsaturated chromagens (pigments) into smaller less pigmented constituents, such as carboxylic acids and alcohol that are colour-free”

In a nutshell, hydrogen peroxide is a strong oxidising agent and oxidises staining macromolecules, breaking them down to smaller fragments which diffuse across the tooth surface, thus causing a lightening effect

Question 3

Describe the mechanisms of action for carbamide peroxide in the tooth whitening process

Answer 3

• Carbamide peroxide contains hydrogen peroxide at a ratio of 1:3. For example, a product with 30% carbamide peroxide has about 10% hydrogen peroxide.
• Hydrogen peroxide is the main active ingredient
• Carbamide peroxide works a lot slower
• Carbamide peroxide can be used at home without dental supervision; however it’s recommended consulting with the dentist first. Using hydrogen peroxide is associated with higher sensitivity

Question 4

Discuss what needs to be considered prior to tooth whitening (or bleaching) for various dental conditions and older patients

Answer 4

• If the patient presents with cracks and fractures in the teeth, the patient may experience some sensitivity. Thus it is recommended to place a temporary sealant and then whiten the tooth
• Blue to grey discolouration’s may be difficult to whiten. It is important to lower their expectations before treatment
• Restorations may not changed colour. Thus it might be wise to whiten the tooth then replace the restoration so it matches the colour of the tooth
• Response to whitening agent has more to do with age of teeth than baseline shade
• Leaking restorations or chips exposing dentine
• Pulp status
• Dentine exposure e.g. cavitated caries, toothbrush abrasion
• Effect on some dental materials E.g. GIC – bleaching products can cause reduced fluoride count, dissolution of the matrix and exposure of filler particle
• Risk of external resorption with non-vital tooth bleaching
• May have limited effect on intrinsic staining. For example, tetracycline stains may not have their stains completely removed
• Crowns with exposed margins (as well as bridges, partial dentures) will need replacement after treatment
• Bleaching will not change tooth shape, enamel quality e.g. Amelogenesis imperfecta
• Single dark tooth almost always indicates a non-vital tooth, requiring further investigation and treatment. It increase risk of sensitivity and staining
• Localised demineralised areas should be noted as bleaching may not mask completely
• Abraded teeth (and those with attrition and erosion) with exposed dentine are likely to become sensitive and will contrast even more with whitened teeth

Question 5

Discuss the precautions a clinician must first address prior to tooth whitening or bleaching

Answer 5

• Patient should have good gingival and general oral health
• Advised not to carry out vital bleaching during pregnancy (peroxide is cytotoxic and carcinogenic)
• Patients you should not use cigarettes or alcoholic beverages while undergoing whitening/bleaching (suggestion, but no evidence, that peroxides could potentiate the action of some carcinogens)
• Do not use whitening/bleaching agents on patients who are allergic to peroxides, glycerine, carbopol etc.
• Avoid treatment of patients who may swallow (young age) or aspirate whitening/bleaching product

Question 6

List the 4 types of tooth whitening/bleaching systems available to patients in the office (professionally) and over-the-counter

Answer 6

• Dentist applied prophylaxis paste (abrasion)
• Home applied (Tray Bleaching)/dentist monitored

• In Office or Power
bleaching

• Walking bleaching (non-vital teeth) heat, light or laser to accelerate the reaction
• Over the counter (OTC) - Whitening strips E.g. Crest Whitening strip, paint-on gels eg Colgate Simply White, tray systems and toothpaste

Question 7

Briefly explain in office/ power bleaching using a light source

Answer 7

Whitening agent has a photocatalyst. When light is added, the hydrogen peroxide is readily broken down and this helps breakdown the stains which are macromolecules

Question 8

Briefly explain bleaching of a non vital tooth

Answer 8

• Because the dentinal tubules are s shaped, bleaching needs to be done below the gingival margin
• Whitening occurs from within the tooth
• The gutta percha is eliminated 2mm below the CEJ. A 2mm barrier of GIC or flowable is placed to seal the endodontic filling material
• The whitening material is placed into the pulp chamber
• There is a risk for internal and external resorption as the bleach will diffuse through the dentinal tubules

Question 9

List the 8 indications for tooth whitening/bleaching

Answer 9

• Generalised yellow, orange or light brown discolouration
• Age- related yellow discolouration
• Mild tetracycline staining
• Superficial brown fluorosis stains
• Discolouration due to smoking, coffee, tea and other chromogenic foods
• Patients with genetically yellow or grey teeth
• Patients wanting shade improvement with minimally invasive treatment
• Yellow discolouration of a single vital anterior teeth

Question 10

List the 9 contraindications for tooth whitening/bleaching

Answer 10

• Amelogenesis imperfecta and Dentinogenesis imperfecta
• Severe tetracycline discolouration
• Discolouration due to restorative materials
• Pregnant or nursing women
• Severe surface damage due to attrition., abrasion or erosion
• Lack of compliance
• Inability to tolerate the tray or taste of the product
• Unrealistic expectations
• Teeth with severe pre-existing sensitivity

Question 11

List the 9 side effects of tooth whitening/bleaching

Answer 11

• Chemical irritation
• Tooth sensitivity
• Gingival sensitivity
• Gingival hyperaemia
• Loss of epithelial integrity
• Allergic reaction
• Gastro-intestinal sensitivity – throat, tongue, etc
• Pulpal necrosis is usually only associated with bleaching if excessive heat or trauma exists
• May reduce the strength of a CR bond. May last for 1 week after bleaching

Question 12

Discuss post- tooth whitening/bleaching recommendations

Answer 12

• Avoid foods that stain e.g. beetroot, curries, tea, coffee, red wine,
• Some colourings in cordials, fizzy drinks, colas, ice-blocks, lollies should be avoided for at least 1 week after tooth whitening/bleaching