Dental bleaching, commonly known as “Teeth Whitening” is a procedure aimed at reducing tooth discolouration through the chemical oxidation of organic chromogens. The stains can be intrinsic or extrinsic.
The bleaching is done by hydrogen peroxide or carbamide peroxide.Carbamide peroxide dissociates into hydrogen peroxide and urea upon contact with water.
The fundamental process is oxidation. Hydrogen peroxide acts as an oxidising agent which diffuses through the enamel and dentin to reach internal pigments. It generates reactive free radicals that attack complex organic molecules (chromogens). And breaks them into smaller, colourless chains, the optical properties of the tooth are modified to reflect more light, resulting in a whiter appearance.
Types of bleaching
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InOffice: Utilises high concentrations of peroxide for rapid results. Requires gingival barriers to prevent chemical burns.
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At Home: Uses custom trays and lower concentrations,
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Internal: For endodontically treated teeth; involves placing the agent directly into the pulp chamber.
Side Effects
Bleaching involves several documented adverseeffects:
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Dentinal Hypersensitivity: This is the most common side effect. According to the hydrodynamic theory, peroxide induces fluid movement in the dentinal tubules, stimulating pulpal nerve endings.
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Gingival Irritation: Soft tissue “blanching” or chemical burns occur if high-concentration gels contact the gingiva.
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Enamel Alterations: Excessive bleaching can increase enamel porosity and temporarily reduce microhardness.
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Restorative Interference: Bleaching does not lighten composite resins or porcelain. Furthermore, it can increase mercury release from amalgams and temporarily inhibit the bond strength of new adhesive restorations.
The Dentist’s Dilemma
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Dentists often face pressure to provide aggressive whitening for patients with healthy teeth. The clinician has to weigh the patient’s desire for aesthetics against the risk of permanent pulpal damage or sensitivity.
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“Bleachorexia”: This term refers to an obsessive compulsive dissatisfaction where patients perceive their teeth as perpetually yellow. Identifying these patients is critical to avoid unnecessary over-treatment.
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Treating minors for staining (e.g., fluorosis) involves high risk, as larger pulp chambers in young teeth are more susceptible to chemical inflammation.
Dental bleaching is a nuanced biochemical procedure rather than a simple cosmetic service. Success requires a balance between effective oxidation and the mitigation of pulpal and gingival trauma.
As clinicians, where do we draw the line between patient autonomy and non-maleficence
MBH/PS