Tooth Whitening Flashcards
List the main extrinsic causes of tooth discoloration
Smoking
Tannins (tea, coffee, red wine, Guinness),
Chromogenic bacteria
Chlorhexidine
Iron supplements
What are the intrinsic causes of tooth discoloration?
Fluorosis
Tetracycline
Non-vitality (blood products)
Physiological (age changes)
Dental materials (amalgam, root filling materials)
Porphyria
Cystic fibrosis
Thalassemia
Sickle cell anemia
Hyperbilirubinaemia
Which genetic/medical conditions cause discolored teeth and what colors result?
Porphyria (red primary teeth)
Cystic fibrosis (grey teeth)
Thalassemia/sickle cell anemia (blue, green or brown teeth)
Hyperbilirubinaemia (green teeth)
What are the two types of tooth bleaching?
External vital bleaching and internal non-vital bleaching
What is the chemical process behind vital external bleaching?
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.
What is the active agent in tooth bleaching and how does it work?
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.
What are the main constituents of bleaching gel?
Carbamide peroxide, carbopol, urea, surfactant, pigment dispersers, preservative, flavor, potassium nitrate, calcium phosphate, fluoride
What is carbamide peroxide and how does it relate to hydrogen peroxide?
Carbamide peroxide is the active ingredient that breaks down to produce hydrogen peroxide and urea. 10% carbamide peroxide → 3.6% H₂O₂ + 6.4% urea.
What is the purpose of carbopol in bleaching gel?
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.
What functions do urea and surfactants serve in bleaching gel?
Urea raises pH and stabilizes hydrogen peroxide. Surfactants allow the gel to wet the tooth surface.
What is the purpose of potassium nitrate, calcium phosphate, and fluoride in bleaching gel?
Potassium nitrate and calcium phosphate are tooth desensitizing agents. Fluoride prevents erosion and has a desensitizing effect.
What factors affect bleaching efficacy?
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)
What preparations should be made before starting external vital bleaching?
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.
What warnings should patients receive before bleaching?
Sensitivity, relapse, restoration color (won’t change), allergy, might not work, compliance with regime is required
What are the two types of vital external bleaching?
Chair-side/in-office bleaching and home bleaching
Describe the in-office bleaching technique
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
What is the truth about heat/light/laser use in in-office bleaching?
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.
What is the maximum legal concentration of hydrogen peroxide that can be used for bleaching?
6% hydrogen peroxide (equivalent to 16.7% carbamide peroxide)
What characterizes home vital bleaching?
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
Describe the technique for making custom trays for home bleaching
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
What is the proper home bleaching procedure for patients?
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)
What are the expected results and timeline for home bleaching?
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
What conditions respond well to bleaching?
Age-related darkening/discoloration (yellow/orange responds better than bluish/grey), mild fluorosis, post-smoking cessation
How does tetracycline staining respond to bleaching?
Requires prolonged treatment, better results with yellow and brown staining than grey, can take months
What are the common problems associated with bleaching?
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
What do we know about sensitivity during bleaching?
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.
How long do bleaching results last?
Oxidized chromogens gradually reduce with time, requiring retreatment every 1-3 years (varies by individual)
What safety concerns exist for carbamide peroxide and hydrogen peroxide?
No evidence of cytotoxicity/mutagenicity for 10% carbamide peroxide, but high concentration H₂O₂ can cause problems
How does bleaching affect dental restorations?
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.
Why should restorative procedures be delayed after bleaching?
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.
What causes discoloration in non-vital teeth?
Dead pulp leads to bleeding into dentine, blood products diffuse and darken, resulting in grey discoloration
What are the indications and contraindications for internal non-vital bleaching?
Indications: non-vital tooth, adequate root canal treatment, no apical pathology
Contraindications: heavily restored tooth (better with crown or veneer), staining due to amalgam
What are the advantages and risks of internal non-vital bleaching?
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)
Describe the technique for internal non-vital bleaching
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
How long does internal non-vital bleaching typically take and how long do results last?
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).
What is inside-outside bleaching?
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.
What is micro-abrasion and what is it used for?
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.
Describe the micro-abrasion technique
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
What are the advantages and disadvantages of micro-abrasion?
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
How do HCl and phosphoric acid differ in micro-abrasion?
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.
What clinical considerations must be addressed before tooth whitening?
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)
What are the regulations regarding hydrogen peroxide concentration and age restrictions?
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.
How should tooth whitening products containing between 0.1% and 6% hydrogen peroxide be used?
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.
What are the legal restrictions on higher concentration hydrogen peroxide products?
Concentrations exceeding 6% hydrogen peroxide remain prohibited unless wholly for the purpose of disease prevention. It is a criminal offense to breach these guidelines.
What are the consequences of breaching tooth whitening regulations?
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.
