Teeth Whitening
Teeth Whiteningby Jasmine Chan
INTRODUCTION TO TEETH WHITENING
Teeth whitening has been widely popular, especially due to the rise of ‘perfect teeth’ from social media influencers and famous figures on the internet. This caused a surge in demand for teeth whitening due to this rise in popularity. Teeth whitening, also known as teeth bleaching, is the process of lightening teeth in the mouth. As teeth can become stained due to a variety of reasons, such as from wine, smoking, it has gained popularity - becoming one of the most popular cosmetic procedures. This process can only work on natural teeth which has not been through any alterations. [1]
INTRODUCTION TO NATURAL TEETH COLOUR
White is not a natural teeth colour. Despite it being incredibly popularised, all natural teeth have an underlying colour tone which is determined by genetics. There are 4 basic categories of natural teeth colour: reddish brown, reddish yellow, reddish grey and grey. As age increases, the stains may become more obvious and prominent. The average natural tooth colour has a reddish yellow tint. [2] This is because under the hard outer layer of the teeth known as the enamel, there is a layer below it known as the dentin which is a bony tissue that is naturally yellow. As time goes on, the enamel starts to wear out, causing more of the dentin to see through. [3]
TYPES OF TOOTH STAINING
Before I move on to talk about the scientific mechanism behind teeth whitening, reasons for tooth discolouration must be understood. There are two types of staining: intrinsic and extrinsic staining.
Intrinsic staining, also known as internal staining, is caused by genetics due to the overexposure of enamel wear to yellower dentin, usage of antibiotics, high concentrations of fluoride and some developmental disorders. [1] The enamel is made of tightly packed crystal structures known as rods. Despite this layer seemingly smooth to the naked eye, there are actually small ridges which allows substances to get stuck between the rods, deep into the enamel. [4]
Extrinsic staining or external staining is heavily influenced by the environment such as smoking, pigments in food and drinks, and metals. These stains contain coloured compounds which are adsorbed to the dentin layer of the teeth and hence causing a stain. [1] With effective oral habits such as brushing the teeth, extrinsic staining can usually be avoided. Extrinsic stains can be a variety of colours, such as green, brown, black, yellow etc. Green and orange stains are typically due to poor hygiene when chromogenic bacteria are present. Brown stains are most likely due tobacco which are found in cigarettes, or beverages such as red wine. Yellow stains are due to the heavy plaque and tartar build up and black stains are caused from iron found in saliva. [3,5]
Both types of staining are composed of chromogens, which are colourless compounds which have the potential to become pigmented. They are able to stick to the tooth’s enamel and collect pigments inside the tooth and hence produce stains. [2] Chromogens can either be accumulated in the tooth, causing intrinsic staining, or on the tooth, causing extrinsic staining. They can either be large organic compounds which have conjugated double bonds, or metal-containing compounds. [1]
The most active ingredients in teeth whitening is carbamide peroxide - a stable complex which breaks down through hydrolysis to release hydrogen peroxide, or hydrogen peroxide by itself. [1] Hydrogen peroxide acts as a bleaching agent which becomes oxidised when it is penetrated into the teeth, causing the double bond of chromogens to become a lighter colour. [4] Hydrogen peroxide is able to diffuse easily through gaps in the rods of the enamel, allowing the enamel and dentin to be exposed to this chemical. [6]
TYPES OF TEETH WHITENING SYSTEMS
There are a large variety of teeth whitening treatments, however, in this article I would only be addressing 3: whitening toothpastes, whitening strips and in-office whitening.
Whitening toothpaste contains low concentrations of carbamide peroxide or hydrogen to bleach the teeth. They are usually able to lighten the teeth by one to two shades. However, they usually contain high amounts of abrasives and detergents compared to regular toothpastes. [1] Alongside with hydrogen peroxide and regular toothpaste ingredients, there are additional agents such as enzymes, citrate, pyrophosphate and hexametaphosphate which can all improve whiteness of the teeth. Whitening toothpastes typically are only able to whiten natural teeth colours or light stains such as tea stains, and can only be seen somewhat effective over a course of 2-6 weeks. [7]
Whitening strips are thin layers of gel which contain hydrogen peroxide or carbamide peroxide which are designed to fit over the teeth surface which can lighten the teeth colour by 1-2 shades. [1] Whitening strips are made of small flexible plastic made of polyethylene and are applied to the fronts of the teeth. Despite teeth whitening strips being easy to use, it has more risks compared to teeth whitening toothpaste as it can damage the gum tissue if placed incorrectly. Additionally, spotting can occur if the strip is not placed fully over the teeth, meaning that there can be patches of whitened areas and natural colour. [8]
In-office whitening is one of the most common procedures as it can achieve immediate effect and have higher concentrations of hydrogen peroxide or carbamide peroxide compared to whitening toothpastes and strips. [1] In-office whitening is often the best system since dentists are trained for this process to be reliable and safe. Prior to the procedure, the dentist would clear any plaque or debris on the teeth, ensuring the area of surface is cleaned. Then, a cheek retractor would be used to expose the teeth and a liquid hardening resin/rubber dam would be used around the teeth to protect the gum tissue. The gel is then left on for 15-30 minutes and it is cleaned off. [9]
RISKS OF TEETH WHITENING
Teeth whitening increases tooth sensitivity and can cause mild gingival irritation. The severity of these risks depends on the concentration of the bleaching agent, duration of these treatments. [1] If using at-home whitening treatments such as whitening strips, there is a high chance of overdoing this process and damaging the teeth. Over-whitening can cause the enamel to soften, causing the teeth to turn into a greyish colour which is the opposite of the desired look. [8]
BIBLIOGRAPHY
[2] “The Science of Teeth Whitening.” The Sadati Center For Aesthetic Dentistry, floridassmiles.com/the-science-of-teeth-whitening/.
[3] “The Science Behind Teeth Whitening.” Narberth PA Dentist, www.mainlinedentalhealth.com/blog/88721-the-science-behind-teeth-whitening.
[4] “The Science Behind Teeth Whitening.” Ala Moana Dental Care, 12 Dec. 2016, alamoanadentalcare.com/the-science-behind-teeth-whitening/.
[5] Kupiec, Lesley McGovern, and Jane L. Forrest. “Staining Types and Causes: What to Know About Whitening.” Continuing Education Course, www.dentalcare.com/en-us/professional-education/ce-courses/ce491/staining-types-and-causes.
[6] “Whitening.” American Dental Association, www.ada.org/en/member-center/oral-health-topics/whitening.
[7] Joiner, Andrew. “Whitening Toothpastes: A Review of the Literature.” Journal of Dentistry, U.S. National Library of Medicine, 2010, pubmed.ncbi.nlm.nih.gov/20562012/.
[8] “Do Whitening Strips Actually Work?” Scott 72 Dental Centre, www.scott72dental.com/site/blog/2019/09/06/do-whitening-strips-actually-work.
[9] “In-Office vs At-Home Teeth Whitening.” Consumer Guide to Dentistry, 19 Dec. 2017, www.yourdentistryguide.com/inoffice-vs-athome/.
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