Whitening Risks Every Hygienist Should Know by Dr. Fadi Swaida

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Tips and considerations to protect patients during whitening procedures


by Dr. Fadi Swaida


An increasing number of people in the world are seeking teeth whitening procedures to improve their smiles.

While teeth whitening procedures have been popular for more than a century, at-home bleaching has become mainstream more recently with the introduction of over-the-counter products. Although whitening is considered safe, and thousands of patients benefit, there is continuing controversy regarding the potential of adverse effects on oral tissues.

Discourage people from teeth whitening procedures done by unqualified individuals, as these procedures may expose them to several risks.

Once aware of the risks associated with teeth whitening, hygienists can take adequate steps to minimize side-effects and maximize benefits for your patients.

Bleach concentration

Teeth whitening products invariably contain varying concentrations of bleach. The concentration of the formulation will depend on the desired result and the current color of the teeth.

For example, while over-the-counter teeth whitening products take about 31.85 cycles of 15 minutes each, in-office procedures require roughly three cycles to achieve the desired effect.

Every teeth whitening agent contains peroxide compounds as the active ingredient, with hydrogen peroxide and carbamide peroxide being the most common. Generally speaking, an in-office bleaching agent will contain approximately 10% carbamide peroxide and 3.5% hydrogen peroxide.

According to recommendations by the ADA, in-office bleaching for teeth whitening contains 15–38% peroxide.1

Enamel damage

For the purposes of in-office teeth whitening, products never contain toxic concentrations of peroxides. However, over-use of teeth whitening products can wear away the lighter outer enamel and expose the darker dentin layer below. Teeth whitening products can penetrate the enamel (which contains very little protein) and react with the collagen found in the dentin layer (which is rich in protein).

Carbamide peroxide releases urea, which attacks the organic material found in enamel by reacting with the protein. These proteins are broken into smaller peptides and then finally released from the enamel altogether. This leads to small, empty craters on the dental enamel through which hydrogen peroxide quickly spreads. The bleaching agents finally cross the dentin-enamel border and penetrate the dentin layer.

Studies show that teeth whitening agents have the potential to break down the collagen found in dentin into smaller fragments.2

Damage to the enamel and dentin layers can be permanent and irreversible. This is why it is best to evaluate the patient’s oral cavity carefully to determine if they are ideal candidates for teeth whitening. Worn down enamel will result in heightened sensitivity after the teeth whitening procedure. The dentist or hygienist may wish to suggest that patients avoid consumption of hot and cold foods 24–48 hours after teeth whitening.

Patients with tooth decay should be advised to get the decay treated as the peroxide component can irritate the site of decay and cause further inflammation and severe sensitivity.3

If the patient has chipped, cracked or fractured teeth, these should be treated first to avoid the whitening gel from leaking into the cavity and causing irritation to the nerves.

Determine the concentration and nature of the teeth whitening treatment depending on the cause for change in teeth.

Risks and irritations

While teeth whitening products are not known to cause permanent damage to gums, patients could experience a temporary irritation too.

Indirect cytotoxicity of 35% hydrogen peroxide is known to promote mild inflammation and pulp alteration since the gel can diffuse through enamel and dentin layers.4

Gum tissue is soft in texture and the patient may suffer from a chemical burn from the bleaching products (somewhat like a sunburn but caused by chemical instead).

The teeth whitening product causes a chemical burn which turn the gums white. This is because the peroxide has dissolved the sore tissue in the patient’s gums. The whiteness is not due to the bleaching effect of H2O2 but due to the release of oxygen micro-bubbles in and around the gingival cells.5

Within 24 hours, the gum tissue should return to normalcy and the white portion will generally flake off. You can protect the patient’s gums by using precisely fitted teeth whitening trays to avoid spillage of excess gel onto the gums. You can also consider using a cotton-tip applicator to immediately wipe off any excess gel. Carefully check the seal or barrier for any leakage of gel throughout the procedure.

Dentists or hygienists should avoid performing teeth whitening procedures on patients suffering from gingival diseases or periodontitis. The bleaching products will irritate the inflamed tissues even further. It is best to advise the patient to get the gum disease treated before getting their teeth whitened.

Use small amounts of teeth whitening gel and use additional amounts only as needed. Avoid using local anesthetic gel to numb the area so that the patient is able to instantly alert the dentist when whitening gel seeps into his or her gums.

Avoid taking too much whitening compound at once to avoid direct contact with gingival tissue. One option: advise the patient to apply a small drop of Vitamin E oil to the spot.

Considering restorations

Teeth whitening products may cause potential damage to dental restorations in the absence of adequate safeguards. They may cause cracking or roughening of the surface of the restorations. Whitening products also reduce the strength of the adhesive that secures the restoration to the tooth.

While the restorations themselves do not stain or whiten, the gel may impact the natural tooth that lies behind the restoration. Take particular care with amalgam restorations. Teeth whitening gels can cause the surface to deteriorate and release mercury.

It is best to avoid teeth whitening for patients with extensive amalgam restorations. Some dental offices use a special lacquer to cover amalgam restorations before applying teeth whitening gel.

Final thoughts

Teeth whitening is an accepted, safe, and popular dental procedure in cosmetic dentistry. Careful monitoring during the progress of treatment minimizes risks associated with poor quality bleaching materials, unsuitable application procedures and over-use of the product.

Potential risks and side-effects of teeth whitening may include irritation and burning of gum tissue, erosion of tooth enamel, heightened sensitivity, and damage to dental restorations. Lack of adequate gingival protection may result in severe irritation of gum tissue.


References
1. Tooth Whitening/Bleaching: Treatment Considerations for Dentists and Their Patients, ADA, September 2009.
2. Teeth Whitening Products Can Harm Protein-Rich Tooth Layer, Science Daily, April 9, 2009.
3. Dentistry Journal: A Critical Review of Modern Concepts for Teeth Whitening (Mathias Epple, Fredric Meyer and Joachim Enax, August, 2019).
4. Cytotoxic Effect of 35% Hydrogen Peroxide Bleaching Gel on Odontoblast-Like MDPC-23 Cells, October 2009.
5. Teeth Whitening: What We Now Know, published Feb 13, 2013, HHS Public Access.


Author Bio
Dr. Fadi Swaida graduated from the University of Western Ontario before graduating from the University of Manitoba’s Faculty of Dentistry. He is an active member of his church, enjoys football and being by the water.

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