Risks

Some of the common side effects involved in teeth whitening are increased sensitivity of the teeth, gum irritation, and extrinsic teeth discolouration.

Hypersensitivityedit

The use of bleach with extremely low pH levels in the tooth whitening procedure may lead to hypersensitive teeth, as it causes the dentinal tubules to open. Exposure to cold, hot, or sweet stimuli may further exacerbate the intensity of the hypersensitive response. Amongst those who receive in-office whitening treatment, between 67–78% of the individuals experience sensitivity after the procedure where hydrogen peroxide and heat is utilised. Although it varies from person to person, sensitivity after whitening treatment can last up to 4–39 days.

Potassium nitrate and sodium fluoride in toothpastes are used to ease discomfort following bleaching, however, there is no evidence to suggest that this is a permanent method to eradicate the issue of hypersensitivity.

Irritation of mucous membranesedit

Hydrogen peroxide is an irritant and cytotoxic. Hydrogen peroxide with concentrations of 10% or higher can cause tissue damage, be corrosive to mucous membranes and cause burning sensation to the skin. Chemical burns can commonly occur whilst bleaching, irritation and discolouration of the mucous membranes may occur if a high concentration of oxidising agent comes in to contact with unprotected tissue. Poorly fitting bleaching trays are amongst the most common reasons for chemical burns. The temporary burning induced by whitening treatments can be reduced by using custom-made plastic trays or nightguards provided by the dental professional. This prevents the leakage of solution onto the surrounding mucosa.

Uneven resultsedit

Uneven results are quite common after bleaching. Consuming less foods and drinks that cause surface staining of teeth can contribute to attaining a good result from tooth whitening.

Return to original pre-treatment shadeedit

Nearly half the initial change in colour provided by an intensive in-office treatment (i.e., one hour treatment in a dentist's chair) may be lost in seven days. Rebound is experienced when a large proportion of the tooth whitening has come from tooth dehydration (also a significant factor in causing sensitivity). As the tooth rehydrates, tooth colour "rebounds", back toward where it started.

Over-bleachingedit

Over-bleaching, more often known as the "bleached effect", occurs among treatments that promise a large change over a short period of time e.g., hours. Over-bleaching can emit a translucent and brittle appearance.

Damage to enameledit

Teeth enamel can have an adverse negative effect by whitening treatment. Evidence from studies show that carbamide peroxide present in whitening gels can damage the enamel surface. Although this effect is not as damaging as phosphoric acid etch, the increased irregularity of the teeth surface makes the teeth more susceptible to extrinsic staining, thus having an increased detrimental effect on the aesthetics. The increased porosity and changes in surface roughness may have an impact on the formation of supra- and subgingival plaque, thus increasing the adhesion of bacterial species such as Streptococcus mutans and Streptococcus sobrinus, significant contributors to dental caries. Dental restorations are susceptible to unacceptable colour change even when using the home-based systems.

Weakened dentineedit

Intracoronal bleaching is a tooth whitening method that uses 30% more hydrogen peroxide. Such tooth whitening methods can weaken the mechanical properties of dentine and could potentially lead to severe tooth sensitivity.

Effects on existing restorationsedit

Dental restorations are susceptible to unacceptable colour change even when using the home-based systems.

Ceramic Crowns – aggressive bleaching can chemically react with ceramic crowns and reduce their stability.

Dental amalgam – exposure to carbamide peroxide solutions increase mercury release for one to two days. The release of amalgam components is said to be due to active oxidation. This increase in amalgam mercury release is proportional to the concentration of carbamide peroxide.

Resin composite – bond strength between enamel and resin based fillings become weakened. Many studies have found that 10-16% carbamide peroxide tooth bleaching gels (containing approximately 3.6-5.76% hydrogen peroxide) leads to an increase in the surface roughness and porosity of composite resins. However, the saliva may exert a protective effect. In addition, changes in the reflectance of the composite have been analysed following whitening with high concentration (30-35%) hydrogen peroxide. This suggests that tooth whitening negatively impacts composite resin restorations.

Glass ionomer and other cements – studies suggest that solubility of these materials may increase.

Bleachorexiaedit

Bleachorexia is the term that is used to describe an individual that develops an unhealthy obsession with teeth whitening. This condition is similar to body dysmorphic disorder. The characteristics of bleachorexia are the continuous use of whitening products even though the teeth cannot possibly become whiter, despite the provision of repeated treatment. A person with bleachorexia will continually seek out for different whitening products, hence, it is recommended that a target shade is agreed upon before starting the treatment procedure to help with this problem.

Home teeth whitening risksedit

The use of personalised home whitening trays is a patient administered therapy that is prescribed and dispensed by a dentist. Patients need to actively participate in their treatment and follow the guidelines given by the dentist accurately. Erratic or inaccurate use of the bleaching trays could cause harm to the patient such as blistering or sensitivity of the teeth and the surrounding soft tissue. Inconsistent use of the bleaching trays can lead to the slowing and irregularity of the whitening process. Some patients with a substantial gag reflex may not be able to tolerate the trays and would need to consider other methods of teeth whitening.

Other risksedit

Evidence suggests that hydrogen peroxide might act as a tumour promoter. Although cervical root resorption is more evidently observed in thermocatalytic bleaching methods, intracoronal internal bleaching may also lead to tooth root resorption. Moreover, severe damage to intracoronal dentine and tooth crown fracture can occur due to this bleaching method.

However, the International Agency of Research on Cancer (IARC) has concluded that there is insufficient evidence to prove that hydrogen peroxide is a carcinogen to humans. Recently, the genotoxic potential of hydrogen peroxide was evaluated. The results indicated that the oral health products that contain or release hydrogen peroxide up to 3.6% will not increase the cancerous risk of an individual, hence, it is safe to use in moderation.