4 - Tooth whitening Flashcards
What are the extrinsic causes of tooth discolouration?
- smoking
- tannins
- chromogenic bacteria
- chlorohexadine
- iron supplements
What are intrinsic causes of tooth discolouration? (9)
- fluorosis
- tertracycline (old antibiotic)
- loss of vitality
- age
- dental materials
- porphyria
- CF
- thalassemia, sickle cell anaemia
- hyperbilirubinaemia
What discolouration does porphyria cause?
Red primary teeth
What discolouration does CF cause?
Grey
What discolouration does thalassemia or sickle cell disease cause?
Blue, green or brown
What discolouration does hyperbilirubinaemia cause?
Green
What are the different types of tooth bleaching?
- external vital
- internal non-vital
Describe external vital bleaching.
- good for discolouration caused by chromogenic products
- bleaching oxides organic molecules, the smaller molecules are less pigmented
- hydrogen peroxide is the active agent
Describe how hydrogen peroxide acts as the active bleaching agent.
- forms acidic solution in water
- free radical is formed (hydroxyl) which is the active oxidising agent
- oxidises long organic molecules to breakdown into smaller molecules which are less pigmented
What are the constituents of external bleaching gel?
- carbamide peroxide
- carbopol
- urea
- surfactant
- pigment dispersers
- preservative
- flavour
- potassium nitrate
- calcium phosphate
- fluoride
What is carbamide peroxide?
- active ingredient
- breakdowns to produce urea and hydrogen peroxide
- maximum 16.7% carbamide peroxide in gel
What is carbopol?
- thickening agent, increases viscosity to keep gel where placed
- slow release of oxygen
- diffuses slowly into enamel
What is urea?
- raises pH of gel
- stabilises hydrogen peroxide and slows reaction
What is surfactant?
Allows gel to wet the tooth surface
What factors affect the bleaching result?
- time increases effect
- cleanliness of tooth surfaces increases effect
- concentration increases effect
- higher temperature increases speed of effect
What should you warn your patient of before beginning external bleaching?
- sensitivity
- relapse
- colour of restoration won’t change
- allergy
- may not work
- compliance is key
What are the advantages of in office bleaching?
- controlled by dentist
- can use heat/light as catalyst
- quick results
What are the disadvantages of in office bleaching?
- increased time in chair
- can be uncomfortable
- results wear off quicker
- expensive
Describe the process of in office bleaching.
- thorough cleaning of teeth
- rubber dam placed with gingival mask
- bleaching gel applied
- apply heat or light
- wash/dry/repeat
- 30-60 mins
Describe the process of at home bleaching.
- custom tray made (0.5mm thick, soft acrylic)
- patient prescribed carbamide peroxide gel 10-15%
- patient wears trays overnight ideally
- bleaching occurs slowly over several weeks
When is it appropriate to using external bleaching?
- age related discolouration (yellow/orange responds best)
- mild fluorosis
- post smoking cessation
- tetracycline staining if prolonged treatment
What are the problems associated with external bleaching?
- sensitivity
- wears off
- gingival irritation
- tooth damage
- damage to restorations
- can impact effectiveness of bonding to teeth
- cytotoxicity
What are predictors of sensitivity post-bleaching?
- preexisting sensitivity
- high concentration agent
- frequency
- bleaching method
- gingival recession
How do you combat problems with bonding to newly bleaching teeth?
- wait at least 24 hours
- a week is best
What is chlorine dioxide?
- used to whiten teeth by some beauty salons and cruise liners
- pH of 3 softens enamel
- teeth become more prone to staining and develop roughened appearance
- teeth become extremely sensitive
What are the indications for internal non-vital bleaching?
- non-vital tooth
- adequate RCT
- no apical pathology
What are the contra-indications for internal non-vital bleaching?
- heavily restored tooth (crown or veneer instead)
- staining caused by amalgam
What are the advantages associated with internal beaching?
- easy
- conservative
- good patient satisfaction
What are the risks associated with internal bleaching?
- external cervical resorption
- due to diffusion of hydrogen peroxide through dentine into periodontal tissues
- theoretical problem
Describe the process of internal bleaching.
- record shade
- place rubber dam
- remove restoration from access cavity
- remove GP from pulp chamber and 1mm below ACJ
- place RMGIC over GP to seal canal
- remove dark dentine
- etch internal surface with 37% phosphoric acid
- place 10% carbamide peroxide gel
- place cotton wool over this
- seal with GIC
- repeat at weekly intervals
- restore tooth with white GP after no further change
What is combination bleaching?
- internal and external bleaching
- prepare cavity as with internal bleaching
- custom tray with palatal reservoir for 24 hour wear
- carbamide peroxide gel placed in reservoir and within cavity for around a week, topping up as necessary
What is mircoabrasion?
- combination of erosion using acid, and abrasion using pumice
- removes discolouration which is limited to the outer layers of enamel
What are the indications for microabrasion?
- superficial fluorosis
- post orthodontic demineralisation
- demineralisation with staining
- prior to veneer preparation if dark staining
What is the technique for microabrasion?
- clean teeth thoroughly
- rubber dam placed
- 18% HCl and pumice mix applied to teeth
- prophy cup used for 5s/tooth
- washed
- repeat up to 10x
- remove dam
- polish teeth with fluoride paste
- apply fluoride gel/varnish
- review at 1 month
What are the advantages of microabrasion?
- quick
- easy
- no long term problems
What are the disadvantages of microabrasion?
- acid
- sensitivity
- only works for superficial staining
- works better on brown stains that white
What is resin infiltration?
- surface layer is not removed
- area is infiltrated with resin
- changes the refraction index of the white area
- masks the area (more porous enamel) to make it look like the surrounding areas
What are the indications for resin infiltration?
- white spot lesions
- arresting very early caries
What are medical contra-indications for tooth bleaching?
- glucose-6-phosphate dehydrogenase deficiency (v rare)
- acatalasemia (low levels of catalase enzyme)
- neither group can metabolise hydrogen peroxide
What is the maximum strength of hydrogen peroxide that can be used in tooth bleaching products?
16.7% carbamide peroxide which equates to 6% hydrogen peroxide
At what age can you conduct tooth bleaching?
- over 18s
- under 18s can only bleach their teeth if it is wholly intended for the purpose of preventing disease
