Tooth Whitening

Question 1

Extrinsic causes of tooth discolouration

Answer 1

• smoking
• tannins e.g. tea, coffee
• chromogenic bacteria
• chlorohexidine
• iron supplements

Question 2

intrinsic causes of tooth discolouration

Answer 2

• fluorosis
• tetracycline
• non-vitality
• amalgam
• cystic fibrosis - grey teeth
• sickle cell anaemia

Question 3

Two types of tooth bleaching

Answer 3

• external vital bleaching
• internal non-vital bleaching

Question 4

briefly describe how vital external bleaching works

Answer 4

• discolouration caused by formation of chemically stable, chromogenic products within tooth substance
• bleaching oxides compounds into smaller molecules which are often not pigmented
• oxidation can cause ionic exchange in metallic molecules = lighter colour

Question 5

active agent in vital external bleaching

Answer 5

hydrogen peroxide or carbamide peroxide

Question 6

What are the products of the breakdown of carbamide peroxide?

Answer 6

hydrogen peroxide and urea (urea increases pH)

Question 7

function of carbopol in bleaching gel

Answer 7

• thickening agent
• slows release of oxygen
• increases viscosity of gel so it stays on teeth and in tray
• slows diffusion into enamel

Question 8

function of urea in external tooth bleaching

Answer 8

• raises pH
• stabilises hydrogen peroxide

Question 9

function of surfactant in external tooth bleaching

Answer 9

allows gel to wet the tooth surface

Question 10

function of fluoride in external bleaching

Answer 10

• desensitising effect
• prevents erosion

Question 11

factors affecting external tooth bleaching

Answer 11

• time
• cleanliness of tooth surface
• concentration of solution
• temperature

Question 12

external vital bleaching - warnings to patients

Answer 12

• sensitivity
• relapse
• won’t bleach restorations
• allergy
• might not work
• compliance with regime

Question 13

Advantages of in office bleaching

Answer 13

• controlled by dentist
• can use heat/light
• quick results for patient

Question 14

disadvantages of in office bleaching

Answer 14

• time for dentist
• can be uncomfortable
• expensive
• results tend to wear off quicker

Question 15

in office bleaching technique

Answer 15

• thorough clean of teeth
• rubber dam or at least gingival mask
• apply bleaching gel to tooth
• apply heat and light
• wash, dry and repeat
• takes 30 mins to an hour

Question 16

home vital bleaching technique

Answer 16

• requires custom made tray
• bleaches slowly, over several weeks

Question 17

internal non-vital bleaching Indications

Answer 17

• non-vital tooth
• adequate RCT
• no apical pathology

Question 18

internal non-vital bleaching contraindications

Answer 18

• heavily restored tooth
• staining due to amalgam

Question 19

internal non-vital bleaching advantages

Answer 19

• easy
• conservative
• patient satisfaction

Question 20

internal non-vital bleaching - risks

Answer 20

external cervical resorption
- due to diffusion of H202 through dentine into periodontal tissues
- high conc H202 and heat

Question 21

Internal non-vital bleaching technique

Answer 21

record shade
prophylaxis
rubber dam
remove filling from access cavity
remove gp from pulp chamber and 1mm below ACJ
place 1mmm RMGIC over GP to seal canal
- seals dentine and prevents root resorption
remove any very dark dentine
etch internal surface of the tooth
place carbamide peroxide gel in cavity
cotton wool over this
seal with GIC
Repeat procedure at regular intervals

Question 22

What concentration phosphoric acid is used to etch the internal surface of the tooth?

Answer 22

37%

Question 23

what percentage of carbide peroxide os used in non vital internal bleaching?

Answer 23

10%

Question 24

How many times do you repeat the technique for internal non-vital bleaching?

Answer 24

until required shade achieved or there is no change
- usually takes 3-4 visits

Question 25

After 4 visits, if internal bleaching not worked, what other options do you have?

Answer 25

crown
veneer
composite build up

Question 26

Non-vital internal bleaching - what do you do when final shade is obtained?

Answer 26

restore palatal cavity
place white GP or similar in pulp chamber
restore with light shade of composite
will gradually darken again - pretreatment every 4-5 years?

Question 27

What is micorabrasion?

Answer 27

combination of erosion (acid) and abrasion (pumice)
- to remove discolouration limited to outer layers of enamel

Question 28

Microabrasion - indications

Answer 28

fluorosis
post orthodontic demineralisation
demineralisation with staining
prior to veneering if dark staining present

Question 29

micro abrasion technique

Answer 29

clean teeth thoroughly
rubber dam - seal very important
mic 19% HCL and pumice
apply to teeth
gently rub with prophy cup 5 seconds per tooth
wash
repeat up to 10x
remove rubber dam
polish teeth with proxy paste
apply fluoride varnish or gel
- regarded surface and decreases sensitivity
review after one month

Question 30

micro abrasion advantages

Answer 30

quick
easy
no long term problems

Question 31

micro-abrasion disadvantages

Answer 31

• acid
• sensitivity
• only works for superficial staining
• works better for brown staining than white marks