Tooth Whitening Flashcards
what are the 2 main types of tooth discolouration
- extrinsic
- intrinsic
what are the causes of extrinsic tooth discolouration
○ Smoking
§ The most common cause
[Lot more discolouration in a pipe smoker than cigarette]
○ Tannins
○ Chromogenic Bacteria
[Commoner in children]
○ Chlorhexidine
[When taken in excessive amounts]
○ Iron supplements
what are tannins found in
§ Tea
§ Coffee
§ Red Wine
§ Guinness
what are the causes of intrinsic tooth discolouration
○ Fluorosis
[Quite common]
○ Tetracycline
[Used to be common, still can be likely in older people but now there is a lot more antibiotics available]
○ Non-vitality (blood products)
○ Physiological (age changes)
○ Dental Materials
○ Porphyria (red primary teeth)
○ Cystic Fibrosis (grey teeth)
○ Thalassemia, Sickle Cell anaemia (blue, green or brown teeth)
○ Hyperbilirubinaemia (green teeth)
[Theoretically this is true but never seen]
how can tetracycline cause intrinsic tooth discolouration
□ This relates to the formation of the tooth and to when the tetracycline was actually given so this can still be seen in teenagers who have been given this
□ Eg a wisdom tooth might have this banded discolouration on it because it was the only tooth still forming when the antibiotic was given
□ Can also make the bone around the tooth a different colour because the bone can absorb the drug too
what dental materials can cause intrinsic tooth discolouration
▪ Amalgam
▪ Root filling materials
□ Some materials that used to be used gave a pink colour to the tooth
what should the first method of tooth whitening for extrinsic staining always be
First method of tooth whitening for extrinsic staining should always be HPT
○ Ie clean the patients teeth
○ Hygiene phase therapy, scaling can remove staining
what are the 2 types of tooth bleaching
External Vital Bleaching
Internal Non-vital Bleaching
when can the 2 types of tooth bleaching be used together
Can be used together in non-vital teeth
what is discolouration caused by
• Discolouration is caused by the formation of chemically stable, chromogenic products within the tooth substance.
[Generally what causes discolouration is colour stable, long chain organic molecules which are within the teeth ie they are either present in the teeth initially or they are absorbed into the tooth surface]
These are long chain organic molecules.
how does bleaching work on discolouration
• Bleaching oxidises these compounds.
• Oxidation leads to smaller molecules which are often not pigmented
○ Either breaks them up into smaller compounds
- Or alternatively the other thing that can cause staining is metallic oxide groups and by oxidising these this can change the ionic level that the metallic group is at and this normally goes from being coloured to colourless
- Oxidation can cause ionic exchange in metallic molecules leading to lighter colour.
what role does hydrogen peroxide play in bleaching
- hydrogen peroxide breaks down to get oxygen free radicals
- This then reacts chemically with the large organic chromogenic molecules within your teeth and breaks them down into smaller molecules which don’t impact colour to the teeth
in vital external bleaching, what is hydrogen peroxide and how does it work
Hydrogen peroxide (H2O2) is the active agent
○ Forms an acidic solution in water
○ Breaks down to form water and oxygen
○ Free radical per hydroxyl (HO2)is formed.
§ This is the active oxidising agent
§ This is the important part that causes the breakdown of the molecules
○ Fast reacting oxidising agent
what are the uses of hydrogen peroxide
○ Used as bleaching agent in industry
○ Used to bleach hair
○ Used as a disinfectant
○ Seldom an ingredient in modern tooth bleaching products.
what are the constituents of bleaching gel
○ Carbamide peroxide ○ Carbopol ○ Urea ○ Surfactant ○ Pigment dispersers ○ Preservative ○ Flavour ○ Potassium Nitrate ○ Calcium Phosphate ○ Fluoride
what is carbide peroxide role in bleaching gel
- Active Ingredient
- Breaks down to produce Hydrogen Peroxide and Urea
- 10% Carbamide peroxide → 3.6% H2O2 + 6.4% Urea
• Urea increases pH
○ Counteracts the acidic nature so that you don’t end up with as an acidic material as if you were using hydrogen peroxide on its own
what is the maximum amount of hydrogen peroxide that can be prescribed in a bleaching gel
The maximum amount of hydrogen peroxide that can be prescribed is 6%
what is carbopol role in bleaching gel
• Thickening agent
○ Without this it would be a very thin liquid being painted onto the teeth so it would just run straight off again
• Slows the release of oxygen
○ Slows reaction and keeps material in the tray for longer
• Increases the viscosity of the gel → stays where you put it
○ Stays on teeth
○ Stays in tray
• Slows diffusion into enamel
what is the role of urea in bleaching gel
- Raises pH
* Stabilises Hydrogen Peroxide
what is the role of surfactant
• Allows the gel to wet the tooth surface
what are the roles of potassium nitrate and calcium phosphate
• Tooth desensitising agents
○ Sensitivity is a problem with tooth bleaching
what is the role of fluoride in bleaching gels
• Prevents erosion
○ Hydrogen peroxide is an acidic substance despite the urea in it
• Desensitising effect
what factors affect bleaching
• Time
○ More time → more effect
○ Ie more time for the chemical reaction to occur then the more bleaching will take place
• Cleanliness of the tooth surface
○ Cleaner → better
○ If there is nothing between the tooth surface and the bleach then it will work better
• Concentration of solution
○ Higher concentration → more and quicker effect
• Temperature
○ Higher → quicker effect
what must you check before starting bleaching
- Before you start always check patient is dentally fit
Any leakage of the bleach around carious cavity margins will lead to pulpal damage - Take an initial shade, agree it with the patient and record it in their notes
○ Better still take a photo with a shade guide included in the picture
○ Good to ensure you don’t end up in a dispute with them later on if they think there has been no change as you can actually prove the difference then
what do you need to warn the patient about with bleaching
• Sensitivity
• Relapse
○ Ie the treatment doesn’t last forever
• Restoration colour
○ Restorations don’t change colour the same way teeth do
- Allergy
- Might not work
- Compliance with regime
what are the 2 types of external vital bleaching
Chair-side / in-office
Home
what are the advantages of in-office bleaching
○ Controlled by dentist
○ Can use heat/light
§ This can speed up the process
○ Quick results for patient
what are the disadvantages of in-office bleaching
○ Time for dentist
§ Dentist has to stay there while it is happening
§ Takes an hour, not a lot else to do during this time
○ Can be uncomfortable
§ Have to lie with your mouth open for an hour
§ Also the technique can be uncomfortable for the patient
○ Results tend to wear off quicker
§ For restorations want to select the composite before you put the dental dam on because the teeth can dry out and change colou
§ Patient might get a really good, white effect to begin with but actually a lot of this will be caused by dehydration of the tooth
○ Expensive
§ Eg have to pay for the dentist to be there
explain the in-office bleaching technique
• Thorough cleaning of teeth
• Ideally rubber dam
• At least gingival mask
○ Need to protect the gums
- Apply bleaching gel to tooth
- Apply heat/light
- Wash/dry/repeat
- Takes 30mins to an Hour
what is a gingival mask
Essentially a light curing material (similar to composite) which is placed around the gingival margins to protect them
what is the different to using light / laser techniques rather than using heat
- Often used with In-office bleaching
- Mainly a marketing technique
- No evidence of better bleaching with these additional procedures
• Light and Laser are really just heat sources
○ Heats up the area to speed up the reaction and also dehydrates your teeth
• Often a good initial result
○ Mainly due to dehydration
○ Wears off quickly
• Was very popular and still is to a certain extent
what is essential when carrying out in-office bleaching
Protection of gingivae is essential
Because everything is really dry you need to be careful you don’t cause damage to the gingiva
what are practices which offer in-office bleaching likely to also prescribe when carrying out teeth whitening treatment
Even practices which offer in-office bleaching are likely to also prescribe some home vital bleaching so as the dehydration wears off that these teeth are still treated
what is the concentration of carbamide peroxide gel used in home vital bleaching
10%-15% Carbamide Peroxide Gel
○ 16.7% Carbamide Peroxide equates to 6% hydrogen peroxide which is the maximum strength of solution.
[Anything stronger than this is illegal so this is the maximum amount of hydrogen peroxide that you can possibly use]
what does the dentist need to do to provide home vital bleaching for their patient
○ Full mouth cleaning/polishing of teeth in surgery
○ Fit trays and check extension/comfort
○ Instruction in use
