Bleaching / Teeth whitening/ Bleaching discoloured teeth

 Bleaching / Teeth whitening/ Bleaching discoloured teeth

Cosmetic dentistry has become an integral part of restorative dental practice. 

It is generally perceived that whiter teeth enhance the beauty of a person's smile. 

Etiology of Tooth discolouration-

What is teeth discolouration?? 

TOOTH DISCOLOURATION - It refers to change in the colour or translucency of a tooth due to extrinsic or intrinsic factors. 

Extrinsic discolouration-

These include strains that are deposited on the external surface of the tooth. 

Frequent intake of coffee, tea, red wine, carrot, oranges, etc can stain the teeth. 

Poor oral hygiene and chronic smoking are also frequent causes of extrinsic factor. 

Another common cause of extrinsic factor include chromogenic bacteria and prolonged use of mouthrinses containing chlorehexidine. 

Intrinsic discolouration-

These occurs because of stains incorporated within the tooth structure due to various reasons-

1) Intrapulpal hemorrhage

2) Pulp necrosis

3) Pulpal remnants after endodontic treatment

4) Residual obturating materials in pulp chamber

5) Metallic restoration like amalgam

6) Aging

7) Dental caries

8) Tetracycline stains

9) Flourosis

10) Erythoblastosis fetalis

11) Porphria

12) Amelogenesis imperfecta and dentinogenesis imperfecta. 

Tetracycline stains-

Ingestion of tetracycline in utero by the mother or upto 7- 8 years by the child can lead to the incorporation of tetracycline into dentin during tooth calcification. Tetracycline chelates with calcium to form tetracycline orthophosphate which produces a distinct stain. 

According to severity, there are three degrees of tetracycline stains:

1st degree -  Light yellow, brown or light grey discolouration. This occurs uniformly throughout the crown. 

2nd degree  -  More intense stains without banding. 

3rd degree-   very intense grey stains with horizontal banding especially in cervical region. 

Fluorosis-

Excessive ingestion of fluoride during tooth development can cause defects in ameloblast and improper calcification of teeth. Fluorosis discolouration can range from white opaque spots to dark brown patchy discolouration. Severe fluorosis causes pitting and disfigurement of enamel. 

What is bleaching?? 

Lightening of discolouration of teeth through the application of chemical agents to oxidize the organic pigmentation in teeth. 

What are bleaching agents?? 

These are powerful oxidizing  agents that decolourize the stains in teeth thereby restoring their normal colour. 

To remove pigmentation of teeth bleaching agents are used. 

Three commonly used bleaching agents in dentistry namely are-

1) Hydrogen peroxide

2) sodium perborate

3) Carbamide peroxide. 

1) Hydrogen peroxide-

It is commonly used bleaching agents in industry. At a concentration of 30% (Superoxol) , it is used for in office bleaching procedures. But at this concentration H2O2 is caustic and may cause soft tissue burns in case of accidental contact. Hence, it must be used with a lot of precautions. It is highly unstable at this concentration, therefore it must be refrigerated and stored in dark. 

The bleaching action of H2O2 is accelerated by heat, light or combination with sodium perborate. 

2) Sodium perborate-

This is an oxidising agent available as white powder. It is stable when dry but in the presence of acid or water, it decomposes into sodium metaborate, H2O2 and nascent oxygen. It is safer than concentrated H2O2 and therefore the material of choice in most intracoronal bleaching procedures. 

3) Carbamide peroxide-

This is an organic white crystalline  compound composed of urea and hydrogen peroxide. It is used in concentration of 10% to  35 % . It is supplied as gel by adding thickening agents like carbopol, glycerine, glycol etc. to increase its viscosity and prolong it's contact with tooth structure. It is more stable than H2O2 having a shelf life of upto 2 years. 10% carbamide peroxide release approximately 3% H2O2 and 7% urea. It's bleaching action is similar to H2O2 but is safer than   concentrated   H2O2. Hence this is currently the most popular bleaching agent for at home vital bleaching procedures. 

Removal of special stains of the teeth

1) To remove Iodine stains  - weak ammonia or saturated solution of thiosulphate is used. 

2) To remove Iron stains - Hypochlorite are used, if residual stains are still present they are removed by oxalic acid. 

3) To remove Silver stains-   Hypochlorite are used or iodine solution is used. 

4) Chlorinated lime or acetic acid is used to remove aniline dyes easily.