Updates on teeth bleaching

Neuman Haim, D.M.D, Israel 

www.lingualnews.com, Vol 1, No 3 - July 2003

In 1994, a survey carried out in the United States of America reported that 50% of the population desired whiter teeth. This demand has increased in dental offices in the USA and the western world. (1) The increased demand for cosmetic dentistry including the desire to achieve a whiter and more attractive smile, has led to the development of a variety of new products and techniques of vital tooth bleaching.

The three most commonly undertaken procedures for (vital) tooth bleaching are:

1. At home bleaching

2. In office bleaching

3. Whitening Tooth paste, (which abrade stained enamel surfaces, revealing a cleaner new enamel surface). 

The first report of tooth whitening was described in 1877. This procedure entailed the use of hydrogen peroxide. The use of superoxol and heat was first described in 1918. Tooth whitening is actually a bleaching process that lightens discolorations of tooth enamel. It removes most stains with a gentle action. As the active ingredient in the gel (carbamide peroxide), is broken down, oxygen acts upon the stained organic deposits. These oxidize which serves to cause them to become a whiter shade. This process makes the overall tooth color closer to its natural unstained color. The tooth structure remains unchanged. Crowns, bridges, bondings, and fillings do not lighten with dental bleaching systems.

At-home bleaching
The availability of "at home" vital bleaching has filled a niche in the patient population. This option is a breakthrough in tooth bleaching, since it, in its various forms, has considerably reduced the need for expensive chairside time. The first at-home bleaching procedures were based on carbamide peroxide or hydrogen peroxide. Today, the active ingredient of all the at-home bleaching kits is oxygen ion. The carbamide peroxide (usually 10%-16% concentration) degrades to ammonia, urea, carbonic acid and hydrogen peroxide. The hydrogen peroxide (3% at the end of the chemical reaction) is converted to oxygen and water. This procedure may cause soft tissue

irritation since it is produces a pH 5.3-6.25. Body heat supplies the activation energy for degradation of the oxygenizing agent. (2-7)

The at-home bleaching systems use a custom-fitted mouthpiece, in which is placed the whitening gel, and is worn over the teeth for 1-4 hours per day, or overnight.

Many people notice an immediate whitening of their teeth after just a few hours of bleaching. However, but it usually takes between 10 - 30 hours of cumulative

bleaching time to complete the whitening process (This is true for all at-home dental bleaching systems, regardless of the manufacturer).

The whitening process can be compressed into just a few days, or a few months. The most effective systems utilize Carbamide Peroxide in a concentration of 10% -

22%. Non glycerin-based formulas containing concentrations of 22% Carbamide Peroxide yield the best results. Professional strength whitening gel formulated with 16% carbamide peroxide is the most widely used. Tougher staining may require longer timeframes or a more concentrated gel. For most people, the treatment effect will  last for 18-24 months. Exposure to certain foods and/or beverages (especially coffee, tea, colas and red wines), or the moking of cigarettes etc. will gradually impact the changes cause by bleaching. It is recommended to periodically re-bleach the teeth as a maintenance procedure. It has been reported by patients that this most do "touch-ups" about once every 6-12 months.

There are a variety of at-home products and methods on the market today that claim to deliver effective dental whitening. Some of these methods and products work

better than others and some are completely ineffective. The active ingredient supplied in these whitening gels is very important, as well as is the type of application tray

in which it is placed. Listed below are the popular methods for at-home dental whitening.

The following easy-to-measure criterion may be useful to compare the effectiveness and value of the many dental whitening systems on the market today:

Compared to the in-office variety of bleaching " CARBAMIDE PEROXIDE - If a dental whitening system does not contain carbamide peroxide, it is unlikely to provide

the desired effect. The higher the percentage of carbamide peroxide, the more powerful the formula. However, a high percentage (22%) of carbamide peroxide is associated with tooth sensitivity and gum irritation. Fortunately, these are temporary. " MOLDABLE BLEACHING TRAYS - Whitening gels are required to stay in

contact with the tooth surface for a length of time in order to be effective. Therefore, any effective whitening system must contain custom moldable bleaching trays.

Of these there are two types: ThermoForm (boil-n-bite), and ProLab professional labcreated. Both are effective, but ProLab bleaching trays may be more convenient

and comfortable to use. Gels which are suspended in Glycerin tend to cause gum and mucosal sensitivity. Some products may add flavorings or desensitizers to reduce gum or tooth sensitivity during the bleaching process. Compared to the in office variety of bleaching procedures, the at-home procedures are relatively inexpensive. However, it is difficult to achieve the necessary patient compliance needed to maximize the potential of this approach.

In office bleaching

Doctor administered, or in-office, bleaching is typically performed over a series of visits. It is characterized by the placement of rubber dam isolation, the use of high concentration peroxides (30-35%), and a heat source. This type of isolation is necessary in order to protect the gingival and mucosal tissues from the caustic effect of

the peroxides. This procedure requires multiple applications to whiten the maxillary and mandibular teeth separately. Present developments in the area of tooth  bleaching are focused on producing sensitivity-free bleaching using inoffice alone or in combination with at-home bleaching, or peroxide based light-activated (laser) bleaching.

Laser whitening:

It has been demonstrated that certain lasers can provide the activation energy for the oxidation of dark pigment molecules. (8) Unlike yellow halogen light, the laser

beam is mostly absorbed by the bleaching material and not by the tooth or pulp tissue. Therefore, the procedure is more efficient and less damaging. The blue Argon  laser beam (wave length =448nm),has been found to be effective at the beginning of the bleaching procedure. However, the CO2 laser (10600 nm) is more efficient for lighter spots.

Procedure:

Soft tissues are protected from the bleaching agents by a silicone-glycerine gel and a flexible wax layer. The patient has a bite block between the jaws which isolates

the tongue and throat. Tooth surfaces are first cleaned with alcohol and then covered with the bleaching material. The latter is composed of bleaching powder mixed with 50% hydrogen peroxide. Each tooth is scanned 3 times with the argon laser, while simultaneously heated with infrared light. Then it is scanned with the CO2 laser. The teeth are cleaned with alcohol and covered with fresh bleaching material prior to each exposure to the laser engery. The procedure requires approximately two hours of chair time. It does not illicit any pain or discomfort and no local anesthesia is needed. Patients have no limitations after undergoing the procedure. However  during the treatment the patients' eyes must be covered to avoid any damage by the laser beam or bleaching materials. The treatment can be difficult for patients with TMJ problems, severe gag reflex, or tongue thrust habit. It is contraindicated for patients with active caries, enamel cracks or during active orthodontic treatment.

It is most important to avoid patients with unrealistic expectations. Success is dependent on addressing patient expectations.(9,10)

Light activated whitening

The activation of bleaching gels by visible light has also become available. This whitening technique is performed using a combination of a whitening agent such as peroxide and an auxiliary such as light. All the teeth are whitened simultaneously in an approximately 60 minute single office visit. Low concentration gels (15%) are used for less time than without the addition of light activation which reduces the probability of developing even a transient sensitivity. Addition of a concentrated dose of visible light augments the effects of peroxide tooth whitening. It most likely has a tooth whitening effect of its own. This procedure is most effective in reducing the yellowing of teeth associated with aging. Tooth sensitivity with this procedure was mild, transient and similar to sensitivity reported for at-home whitening.

Evaluation of soft tissue irritation was also mild and transient. The tooth whitening persisted for a minimum of six months with minor transient tooth sensitivity (11).

References
1) Burmahl, Beth, "Bleaching business is blooming" AGD (Academy of General Dentistry) Impact, April 1998, vol 26, No.4, 28-29.
2) "Fact sheet - Academy of General Dentistry - Bleaching", AGD Impact, April 1998, vol 26, No. 4, 28-29.
3) Yarborough, DavidK., "The safety and efficacy of tooth bleaching: a review of the literature 1988-1990", Compend contin. Educ. Dent; VolXII, No3,191-196
4) Christensen, Gordon, D.D.S, Ph.D, "Bleaching Teeth", Journal of the American Dental Association, April 1997, Vol. 128, Suppl., pp. 16S-18S.
5) Garber, David, D.M.D., "Dentist-Monitored Bleaching", Journal of the American Dental Association, April 1997, Vol. 128, Suppl., pp. 11S-15S.
6) Goldstein, Ronald, D.D.S., "In-Office Bleaching", Journal of the American Dental Association, April 1997, Vol. 128 suppl., pp 26S-30S.
7) Haywood, Van, D.M.D., "Nightguard Vital Bleaching", Journal of the American Dental Association, April 1997, Vol. 128' Suppl., pp. 19S-25S.
8) Nathoo, Salim, Ph.D., D.D.S., "The Chemistry and Mechanisms of Extrinsic and Intrinsic Discoloration", Journal of the American Dental Association, April.
9) Freedman, George, D.D.S., Reyto, Robert, D.D.S., "Laser Bleaching: A Clinical Survey Dentistry Today", May 1997, Vol. 16.
10) McCann, Daniel, "Lasers for Bleaching: Safe or Not ?", ADA News, February 3, 1997, Vol. 28, No.3, pp 1-2 .
11) TavaresM, StultzJ, Newman M, Smith V, KentR, Carpino E, GoodsonJM. Light augments tooth whitening with peroxide. J Am Dent Assoc. 2003;134:167-75.
12) Miles, Pontier, Bahiraei, and Close, Effect of carbamide bleach on bond strength: AM J ORTHOD DENTOFAC ORTHOP 1994;106:371-5.

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