Dental Bleaching

Principle: A chemical reaction based on oxidation causing a coloured structure to transform into a less coloured structure or even a colourless material.

Hydrogen peroxide breaks down and releases free radicals. These free radicals split double bonds causing cyclic compounds to open. This changes the molecular structure and causes a shift of spectrum of absorption.

Discoloration

External causes: drinks: tea, coffee, wine, bevarages, Tobacco: these can be helped with prophylactic measures e.g. brushing
Internal causes: drugs(tetracylines, fluorides), trauma, endodontic treatment: these can be helped with bleaching

Examples of dental bleach

  • Hydrogen Peroxide (3%-35%)
  • Carbamide Peroxide (10%-30%) >>> urea + hydrogen peroxide
  • Sodium Perborate >>> sodium metaborate + hydrogen peroxide
  • Calcium Peroxide

Methods of bleaching

  • External bleaching for artificial discoloration
    • Direct (In-office)
    • Assisted (Home)
  • Internal Bleaching/Non-Vital
    • Intracoronal

External Bleaching

Direct (In-office)

  • This procedure is provided by a suitably trained dental professional in a clinical setting
  • Uses a high concentration of peroxide solution e.g 35% hydrogen peroxide applied directly to the teeth
  • Sometimes a heat or light source is used
  • Requires very good isolation to prevent chemical damage to the soft tissues
  • Useful for patients who struggle with home bleaching
  • Disadvantages: difficult to control extent of whitening- risk of under/over bleaching, risk of severe post-op sensitivity

Assisted (Home)

  • Involves taking an alginate impression of the teeth and having a lab fabricate a bleaching tray
  • Requires patient to take and apply the peroxide bleach to the trays and wear at home; usually overnight
  • Low concentrations used e.g.6% Hydrogen peroxide 10-20% Carbamide Peroxide
  • Disadvantage: takes longer – weeks-months to achieve desired results

Internal (Non-vital) Bleaching

Intracoronal (In-office)

  • Used in endodontically treated teeth
  • Involves sealing bleach within the pulp chamber of the tooth and restored temporarily
  • The procedure is repeated every 3-4 days
  • Generally, uses hydrogen peroxide or sodium perborate
  • Disadvantage – requires a well-sealed root canal to prevent bleach reaching the periapical space (seal with GI/composite)