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The Ins and Outs of Tooth Whitening

Author: Victoria Peters

A survey run in 2012 by the American Academy of Cosmetic Dentistry revealed that discoloured, strained or yellow teeth were the main reasons for an unattractive smile (Whitening survey, 2012). Furthermore, a UK survey uncovered that 28% of adults were unhappy with their smiles, with 50% of respondents stating their dissatisfaction was due to their tooth discoloration (Joiner, 2006). Along these lines, tooth whitening products have now become the most popularly marketed oral care product (Whitening survey, 2012).

Tooth discolouration is defined as the change in colour or transparency of a tooth (Watts, 2001). This can occur intrinsically (inside the tooth such as in the pulp) or extrinsically (outside the tooth creating superficial stains) (Demarco, 2009). Extrinsic discoloured is defined as the accumulation of substances on the surface of the tooth from smoking, pigments in food and drinks, or even from metals such as iron or copper (Viscio, 2000). These types of stains can be removed by routine procedures such as brushing. They can become darker and more persistent with time, but are quite responsive to bleaching (Viscio, 2000).

In contrast, intrinsic staining can stem from genetic disorders, antibiotic use, high levels of fluoride intake, cavities, or root filling materials (Carey, 2014; Kolosowski, 2014). Interestingly, high fevers during tooth development can cause a type of banding discoloration of tooth structures (Eachempati, 2018). Additionally, aging causes dentine to darken while enamel thins (Carey, 2014). In general, intrinsic stains cannot be removed by routine cleaning, but can be reduced with bleach agents that penetrate the enamel and dentine (Eachempati, 2018).

There are several methods to whiten teeth. It is also possible to perform internal bleaching on non-vital teeth (also known as a tooth without pulp) or external bleaching on vital teeth (a tooth that still has pulp) (Joiner, 2006). Usually after 6 weeks of bleach use, the maximum lightening potential has been reached (Joshi, 2016).

Internal bleaching is a process performed by an endodontist (a dentist who specializes in performing root canals) following a root canal treatment, which can not be performed at home (Joshi, 2016).

External bleaching is the form of tooth whitening that many of us are familiar with, from whitening gum, floss, mouthwash and whitening strips and trays. Bleaching works to remove stains by chemical degradation of dark compounds on the tooth (Carey, 2014). It’s important to note that external bleaching has something called an end-point, where it reaches its lightening potential for said tooth (Matis, 2000). Usually after 6 weeks of bleach use, the maximum lightening potential has been reached (Matis, 2000). It is also very important to point out the potential adverse effects that can accompany oral bleaching, such as gum sensitivity, tooth sensitivity, GI sensitivity, as well as tongue and throat sensitivity (Eachempati, 2018). However, despite the potential side effects, whitening your smile could provide a boost to your confidence and increase your quality of life.

If you are interested in exploring your whitening options make sure to discuss this with your dentist at your next appointment!


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[2] Demarco, F. F., Meireles, S. S., & Masotti, A. S. (2009). Over-the-counter whitening agents: A concise review. Brazilian Oral Research, 23(suppl 1), 64–70.

[3] Eachempati, P., Kumbargere Nagraj, S., Kiran Kumar Krishanappa, S., Gupta, P., & Yaylali, I. E. (2018). Home-based chemically-induced whitening (bleaching) of teeth in adults. Cochrane Database of Systematic Reviews, 2018(12).

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[6] Kolosowski, K. P., Sodhi, R. N. S., Kishen, A., & Basrani, B. R. (2014). Qualitative analysis of precipitate formation on the surface and in the tubules of dentin irrigated with sodium hypochlorite and a final rinse of chlorhexidine or qmix. Journal of Endodontics, 40(12), 2036–2040.

[7] Matis, B. A., Mousa, H. N., Cochran, M. A., & Eckert, G. J. (2000). Clinical evaluation of bleaching agents of different concentrations. Quintessence International , 31(5), 10.

[8] Viscio, D., Gaffar, A., Fakhry‐Smith , S., & Xu, T. (2000). Present and future technologies of tooth whitening. Compendium of Continuing Education in Dentistry, 28, 36–43.

[9] Watts, A., & Addy, M. (2001). Tooth Discolouration and staining: A review of the literature. British Dental Journal, 190(6), 309–316.

[10] Whitening survey. American Academy of Cosmetic Dentistry. (2012). Retrieved from

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