External bleaching involves various tooth whitening procedures in which bleaching agents are applied externally (from the outside) to the teeth and coloring substances stored in the upper enamel layers are chemically converted into colorless reaction products. Today, a patient associates successful dental care not only with the desire to restore and maintain the health of his or her chewing function, but also hopes for aesthetic improvements that will help him or her achieve a more sympathetic and competent appearance through a radiantly beautiful smile. The most important contribution to radiant teeth is made by the patient himself through consistent, correct dental care at home, combined with the extensive avoidance of staining stimulants such as coffee, certain types of tea, red wine and, above all, nicotine. In addition, the first step in the dental practice is thorough professional tooth cleaning (PZR): discolorations that are deposited on the tooth surface are removed, for example, by cleaning the teeth with a powder jet and subsequent polishing with pastes of different grain sizes. Although these deposited discolorations are also captured by the chemical reactions that take place during bleaching, they should still be removed beforehand, as they otherwise make it more difficult for the bleaching agent to penetrate the tooth surface. Mode of action of the bleaching materials:
Bleaching materials are usually available as a gel and are easy to handle and apply in this dosage form. The chemically reactive substances are:
- Hydrogen peroxide (H2O2; hydrogen superoxide): decomposes and thereby unfolds both reducing and oxidizing effect; larger colored molecules are thereby degraded to smaller colorless reaction products, colored metal oxides are reduced to colorless.
- Carbamide peroxide: decomposes to hydrogen peroxide and urea. The latter further reacts to form carbon dioxide (CO2) and ammonia (NH3). Carbamide peroxide provides a depot for hydrogen peroxide as the actual active ingredient; which is gradually released. A bleaching with carbamide peroxide is accordingly buffered.
Indications (areas of application)
Discoloration that has penetrated into the uppermost layers of the enamel is not accessible to the methods of professional teeth cleaning. This is where the various methods of external bleaching are applied. Useful indications can be:
- Age-related tooth discoloration
- In the mineralization phase of the teeth occurred deposits, for example, tetracycline discoloration; here, however, only the bleaching of light discoloration is considered prognostically good.
Contraindications
For any purely cosmetic treatment, including bleaching, the contraindications should be particularly broad:
- Gravidity (pregnancy)
- Lactation phase (breastfeeding)
- Children and adolescents due to the still large expansion of the pulp (the dental pulp) and thus significantly increased risk of pulpitis (pulp inflammation), especially since no age-related discoloration can yet be present
- Hypersensitivities (hypersensitive tooth necks) – here, in particular, the highly concentrated office bleaching should be avoided
- Insufficient restorations (leaking crown and filling margins).
- Carious defects
- General enamel formation disorders, e.g. amelogenesis imperfecta (genetic disease in which there is a disorder of enamel formation).
- Repeated bleaching before the expiry of three years.
- Excessive consumption of coloring stimulants such as coffee, tea, tobacco, red wine, etc.
- Home bleaching with splint in alcohol abuse / alcohol dependence (night vomiting and other complications can not be ruled out).
Before external bleaching
Before external bleaching, the following measures are required, regardless of the procedure used:
- Informing the patient about health risks and possible complications.
- Clarification of expectations
- Clarification of the widely varying expected duration of the bleaching effect and recurrence (recurrence of the old condition).
- Diagnostics to exclude leaking filling and crown margins and exposed tooth necks.
- Sensitivity check of the teeth to be whitened.
- If necessary, replacement of leaking fillings or temporary sealing of margins on restorations, which should be replaced and color-matched – about four weeks – after bleaching.
- Professional teeth cleaning
- Photos taken in daylight without flash with reference tooth of the color ring to document the success of treatment.
The procedures
For external bleaching, there are basically three differently complex procedures to choose from:
- I. Office bleaching
- II. Home bleaching under dental guidance
- III. home bleaching with over-the-counter bleaching agents.
I. Office bleaching
Office bleaching (synonyms: office bleaching technique; bleaching treatment in the dental office; chairside bleaching) is the most complex procedure. Highly concentrated bleaching products are used. Since the complication rate is inevitably higher with increasing concentration, it is advisable to use office bleaching only in particularly severe cases where success of home bleaching (II. and III.) is highly doubtful from the outset. The following procedure is recommended:
- Installation of rubber dam or application of “liquid rubber dam” on the gingiva (the gums) to minimize irritation caused by the bleaching material.
- Protective goggles for practitioner and patient
- Application of 30-36% hydrogen peroxide gel (H2O2) or 20-30% carbamide peroxide gel to the enamel with due distance to exposed tooth necks and gingiva.
- Exposure time 30 min under constant control; if necessary, premature termination in case of pain sensation.
- Bleaching lamps: increase the penetrating capacity of hydrogen peroxide due to the effect of temperature and thus also the risk of pulpitis (inflammation of the tooth pulp).
- Over-bleaching beyond the targeted shade, as the teeth darken again somewhat in the first four weeks.
- First careful, then intensive spraying of the bleaching gel.
- Removal of the rubber dam or protective varnish from the gingiva.
- Post-treatment of the teeth with fluoride gel or potassium nitrate gel.
- Repeat sessions up to five times
II. Home bleaching under the guidance of a dentist.
This method of home bleaching (synonym: home bleaching treatment) is the lowest-risk procedure, which is easy to use, but requires the reliability and perseverance of the patient:
- Impression of one or both jaws depending on the extent of bleaching.
- Manufacture of a flexible, soft splint (in the dental laboratory by thermoforming technique), the manufacture of which is subject to the following requirements: Recess for bleaching gel depot; recess must have at least 1 mm distance to the gingiva (to the gums); exposed dentin (dentine) such as tooth necks must not be covered by the splint.
- Incorporate the splint on the patient under
- Instructions for applying the bleaching gel: only in the recess area of the splint, apply once, do not constantly replace the gel during the daily wearing time.
- Wearing time daily 1-6 hours, whether during the day or at night.
- Duration of therapy 7-10 days under regular control
Alternatively, the dentist has the option of handing out industrially manufactured applicator splints to the patient under guidance, which are cheaper for the patient, but also bring the disadvantages resulting from poorer fit. III. Home bleaching with over-the-counter bleaching agents
This method of home bleaching is mentioned only for the sake of completeness, as it involves significant risks compared to guided home bleaching. It involves either bleaching gels applied on a universal tray or foil, or varnishes applied with a brush:
- Usually, the patient does not present to the dentist in advance for clarification, risks such as leaking restorations and exposed necks of teeth remain undetected
- A previous professional dental cleaning (PZR) does not take place
- Due to not individualized fit especially the universal trays, it comes to increased swallowing of the bleaching agent.
Possible complications
- Pain reactions, which usually subside after removal of the bleaching gel
- Inflammatory reactions of the pulp (of the tooth pulp).
- Hypersensitivity (hypersensitivity)
- Inflammatory damage to the gingiva (gums) and periodontium (the gums and periodontium) and pharyngeal mucosa.
- Reduced flexural strength of the enamel.
- Reduced hardness of enamel and dentin (dentine)
- Poorer adhesion of adhesively cemented filling materials; for this reason (and others) place adhesive fillings after one week at the earliest.
- Reversible moisture removal from the tooth hard substances.
- Insufficient whitening effect: not every tooth color can be whitened, so the result is unpredictable
