Carbamide peroxide or hydrogen peroxide is used as bleaching agent. They are usually contained in gels based on glycerin. All degradation products of the bleaching agents are also materials produced naturally in the body and are consequently harmless. The oxygen released produces the bleaching effect. If the patient is allergic to any constituent in the bleaching material, the bleaching treatment should not be started or continued.
Peroxides have been used for many years as oral antiseptics (disinfectant mouthrinses). Only recently have they served as bleaching agents for teeth.
Possible side effects of bleaching are:
1. Gingiva irritation
2. Temporary hypersensitivity of the dental necks
3. Short-term nausea
4. Pain in the temporomandibular joint region
The bleaching agents bleach only natural tooth structures. Large fillings or crowns are not bleached and may have to be renewed later, since they no longer match the tooth color of the bleached teeth.
Instructions for Home Bleaching
1. Clean mouth and teeth.
2. Place a small quantity of the bleaching gel into the tray and position the tray slowly.
3. Remove excess bleaching agent.
4. Do not eat while you are wearing the tray. Do not chew on the tray. Do not try to suck out bleaching agents from the tray.
5. Leave tray in place for 45-60 minutes.
6. Remove the tray. Rinse mouth with water.
7. If desired, repeat steps 2 to 6. Increase the bleaching time step-by-step.
8. Never leave the tray in place for the entire night. Maximum bleaching time is five hours per day.
9. If you should have any problems with the bleaching treatment, stop bleaching and call your dentist's office.
10. Return to the dental office as agreed for checkups on the bleaching treatment.
What You, the Patient, Must Observe
Patients should not smoke during the bleaching process. It is possible that the effect of carcinogens present in cigarette smoke can be enhanced with the relase of oxygen.
Pregnant and nursing mothers should not bleach their teeth. It is not yet known whether there could be an interaction between free oxygen radicals released and other substances and whether they can affect the pregnancy. Patients with very sensitive dental necks should not bleach their teeth.
Attainable Coals of the Bleaching Treatment
The dentist has determined the tooth color on a shade guide before the bleaching treatment starts. One can expect the teeth to become about one to two shades brighter.
The average treatment time with the home bleaching method amounts to two to six weeks. The first results are usually already recognizable after five days. Particularly strong discolorations can make a longer treatment period necessary. Strong discolorations in deeper layers of the tooth cannot be altered through the bleaching treatment.
Yellow-brown color changes (age-induced stains) can usually be bleached very easily. According to type and cause of the discoloration repetition (after approx. one to two years) of bleaching is necessary. Therefore, the individually fabricated bleaching tray must be stored safely.
Bleaching Nonvital Teeth
When bleaching nonvital teeth, the bleaching agent is placed into the pulp chamber of the tooth. This method is effective when one wants to brighten nonvital teeth that have changed color after root canal treatments.
History and State of the Art of the Technique
One of the first successful attempts to perform internal bleaching was described by Brown (1965). He mixed sodium perborate and hydrogen peroxide and placed the mixture into the pulp chamber. In 1963, Nutting and Poe proposed the technique in combination with the bleaching process of vital teeth. They used Superoxol, a stabilized hydrogen peroxide, and mixed it with sodium perborate. The mixture was put into the pulp chamber, which was then closed. Since the bleaching process extends over a relativel long period, it has also been called “walking bleach” in the American literature. If the internal dentin has been etched with 37% phosphoric acid before the bleaching agent is placed in the pulp chamber, the penetration of the bleaching agent is increased.
The bleaching process can be accelerated further if the tooth is heated. The bleaching agent in the pulp chamber is renewed after a few minutes' interval and heat applied to the tooth surface. This is known as “power bleaching.” This treatment requires chemicals such as Superoxol (30% stabilized H2O2) and sodium perborate (Amosan by Oral B or sodium peroxyborate-monohydrate from a drugstore). The two products (Superoxol and sodium perborat) are mixed together.
71 Bleaching nonvital teeth
Left: The coronal part of the root canal filling is removed.
Middle: Bleaching agent is inserted into the pulp chamber.
Right: The pulp chamber is closed with a temporary filling material (Cavit). After multiple changes of the bleaching agent and an approx. two-week total treatment period, the bleaching process is completed.
72 Placing the bleaching agent in the pulp chamber
Side Effects and Treatment Preparation
Patients must be informed about effects and side effects of the bleaching process. One of the side effects is that bleaching can cause internal root resorption. The teeth can become brittle with repeated internal bleaching and after time this can cause spontaneous fracture of the clinical crown. Root canal treatments should be completed before bleaching therapy is begun.
The coronal part of the root canal filling must be completely removed, including residual filling material located in the pulp horns. If it is a root canal filling with silver thread, the entire filling needs to be removed and filled again with gutta-percha. The root canal filling must be sealed before bleaching. A small quantity of glass ionomer cement is suitable for this purpose.
Treatment Procedure for Power Bleaching
1. Determine tooth color and take photographs.
2. Isolate the treatment area with rubber dam.
3. Seal the root canal filling with a resin-modified glass ionomer cement. Perform radiographic control.
4. Etch the pulp chamber for no longer than 30 seconds with a 37% phosphoric acid.
5. Mix Superoxol and sodium perborate. Place it in the pulp chamber.
6. Apply heat for two to five minutes. Then remove the bleaching mixture and bring in new bleaching gel. Repeat this process every five minutes over a period of 30 minutes. Overly strong heat development can lead to root resorption.
7. When the bleaching process is finished, the tooth should be rinsed and the tooth color should be checked. Under some circumstances another bleaching session may be necessary.
8. To neutralize the pulp chamber, calcium hydroxide paste is brought into the tooth and left there for about two days.