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Tooth Whitening

In the pursuit of looking good, man has always tried to beautify his face. Since the alignment and appearance of teeth influence the personality, they have received considerable attention. Most modern citizens would prefer to have dazzling white teeth seen on the magazine covers, television and movie screen.  You should also read this article by Tim Huckabee DDS

A variety of tooth whitening options are available today. They include over the counter whitening systems, whitening tooth paste, and the latest high tech option- laser tooth whitening. For maximum effects , as of today, peroxide is usually the agent resorted to.

Currently available tooth whitening options are:

1. Office bleaching procedures.
2. At- home bleaching kits.
3. Bonding- A composite resin that is molded onto the tooth to change its color and to reshape it. The resin material can stain and chip with the passage of time.
4. Porcelain veneers- Shell like porcelain facings are bonded onto stained teeth. They are used to whiten, reshape, or lengthen teeth and require at least two appointments.
5. Whitening tooth pastes- these effectively keep the teeth cleaner and therefore looking whiter. Some of them may be more abrasive than others. The stronger tooth pastes rely more on abrasion to remove external stains than changing the color of teeth.

As the tooth bleaching continues to grow in popularity, research continues into all types of bleaching systems.

Before we go into the details of tooth whitening, lets take a brief look at the causes of tooth discoloration,

They can be broadly classified into
I. Extrinsic stains.
II Intrinsic stains.

I. Extrinsic stains:
-The pellicle on the tooth surface get easily stained and may display many colors ranging from white to red to green.
-Cigarette smoking produces yellowish brown to black discoloration, usually in the cervical portion of the teeth, primarily on the lingual surfaces.
-Tobacco chewing stains frequently penetrate the enamel, producing a deeper stain.
Coffee and tea cause severe, tenacious discoloration’s, usually brown to black.
Extrinsic stains are usually removed during a standard prophylaxis.

II. Intrinsic stains:
1.systemic origin A>during odontogenic period
may be caused
2.local origin B>post eruptively

Types.
1. Tetracycline staining.
a) First degree tetracycline staining. Light yellow, brown or gray uniformly distributed throughout the crown, with no evident banding.
b) Second degree staining. Darker or gray uniform staining, with no banding.
c) Third degree staining. Dark gray or blue staining with marked banding.
d) Fourth degree staining. These stains are too dark. You may have to go for veneers to treat such cases.

2. Fluorosis staining.
It is caused due to excessive intake of fluoride during the development of enamel formation and calcification.
Seen in population where drinking water contains more than 1ppm fluoride concentration. Fluorosis may be:
a) Simple fluorosis staining. Appears as brown pigmentation on a smooth enamel surface.
b) Opaque fluorosis. Appears as flat gray or white flecks on enamel surface.
c) Fluoride staining with pitting. Dark pigmentation with surface defects.
These cases respond to vital tooth bleaching. If stains are set deep into the tooth and are very opaque, then bleaching should be followed by veneers.

3.Discoloration from pulp necrosis.
This responds well to non vital bleaching techniques.

4.Iatrogenic discoloration.
From medications(formo cresol), silver amalgam etc.,

5.Discoloration due to heredity and dental history.
People are genetically programmed to have lighter or darker teeth, and are predisposed to respond more quickly and severely to staining agents.
Dental caries is a primary cause of unattractive pigmentation(opaque white halo or gray discoloration.)

6.Discoloration due to aging
-yellowish brown.

7. Discoloration from systemic conditions  
Dentinogenesis imperfecta, jaundice. Bleaching Techniques.

While the exact mechanism of bleaching tooth structure has not been fully explained, the general action of bleaches involves the breaking down of unstable peroxides into highly unstable free radicals. These free radicals then react with organic pigmented molecules and through oxidation, change the ring structures to unsaturated chains which are further degraded to individual hydroxyl groups.

With each step of this reaction, the pigments become lighter and lighter.
The bleaching procedures may be internal or external on the enamel surface, which depends on the vitality of the tooth. Vital teeth can be bleached by :

1. Dentist applied (Office) bleaching.
2. Patient applied (Home) bleaching.
3. By enamel microabrasion.

I. External (vital) bleaching.
The first published report of bleaching was by Chapple in 1877 and involved the use of oxalic acid.

Indications.
-Mild, uniform, yellow discoloration(age darkening and fluorosis).
-Yellow to brown extrinsic/intrinsic staining(age darkening, fluorosis, tetracycline)
-Discoloration in the gray, blue gray or black range do not respond well to bleaching and tend to darken more rapidly .
-Teeth that exhibit color banding from tetracycline require special procedures to minimize the band effect.

Longevity.
Treatment is seldom permanent and a reliable prediction of the exact duration of color change is impossible. Generally, the color lightening lasts from 1 to 4 years, with the teeth gradually returning to their original color, partly due to age darkening.
The effect seems to last longer in young patients and yellow stains recur more slowly than blue/gray/black discoloration.
Risks.
Over the years, bleaching has been shown to be a relatively safe procedure. Certain risks which are associated with it can be adequately controlled by following the technique properly.
-Bleaching agents and heat application can produce pulpal changes.
-Bleaching agents can alter enamel and dentin structure. Reduction in the microhardness of both enamel and dentin has been reported.
-Peroxides have mutagenic potential and boost the effects of known carcinogens.
-Long term use can alter the oral flora.
-Potential for chemical burns of the soft tissues
-Bleaching can cause a reduction in the bond strength between composite materials and the enamel surface.
-Use of hydrogen peroxide for internal bleaching can lead to external cervical root resorption.

Technique.
Due to the technical nature of the procedure and the caustic nature of the materials involved, bleaching should be performed by the dentist. However, in today’s practice, bleaching can be done either as an office procedure or the patient may apply special bleaching materials at home under the instructions and recall monitoring of the dentist.

I. Dentist applied(office) bleaching
Materials.
-The commonly used bleaching agent, superoxol, which is 30-35% hydrogen peroxide should be kept refrigerated in a tightly capped, amber colored bottle or other opaque container. Under these conditions, the shelf life should be approximately 1 year.
-Ethyl ether may be mixed with superoxol in a 1:5 ratio and the mixture used for bleaching. The addition of ether lowers the surface tension of the liquid for better wetting and enhances the penetration of superoxol into the tooth structure.
-Phosphoric acid etching gel. Etching the enamel surface prior to bleaching increases the porosity of the enamel and allows greater penetration of the bleach.

Activation.
The application of heat accelerate the reactivity of bleaching agent and shorten the treatment time. Effective temperature that do not produce undue pulpal reaction are in the range of 125-140° F (52-60° C).
-Heat can be applied with a metal instrument heated over a flame.
-But it is preferable to use a regulated heat source. there are three heating instruments currently marketed by Union Broach Company.
1.Union Broach heating paddle, a heating instrument with interchangeable metal tips and good heat regulation.
2. New Image Bleaching Unit, a heat lamp with built-in timer and temperature regulation.
3. The Illuminator, a combination unit with both heat lamp and heating paddle.

-New laser bleaching can be an option for some patients who want dramatic whitening effect quickly. In a recent report by Dr. Garber, lasers used for lightening do not bleach teeth, they merely create a reaction when the hydrogen peroxide comes in contact with the laser’s beam.
This procedure begins with the application of a gel to the teeth. When energized by special lasers, the gel acts as a catalyst to whiten the enamel. Two different lasers are usually used.
The Argon laser which emits a visible blue light is used first to activate the bleaching gel. This blue light will be absorbed by the dark stains and becomes less effective as the tooth whitens because the blue light will be reflected rather than absorbed by the whiter tooth surface.
Then the CO2 laser which emits invisible infrared energy is used to achieve deeper penetration of the energized oxygen leaking to a deeper, more efficient tooth whitening.

Treatment.
Pre operative evaluation
-Evaluate the suitability of the case.
-Inform the patient of the limitations and longevity of bleaching.
-Take radiographs and test the vitality of the teeth to be bleached.
-Replace or seal any defective restorations in the teeth to be bleached.
-Take pre operative color photograph and/or shade match for comparison later.
Isolation
-Apply petroleum jelly to soft tissues.
-Apply rubber dam.
-Clean the teeth with pumice and water.
Bleaching
-Cut and apply gauze strip to cover the entire facial and most of the lingual surfaces of the teeth. Loose mat of cotton can also be used.
-Saturate the gauze or cotton with the bleach. Change the gauze every 5-10 minutes.
-Apply heat.
-Continue treatment for 30-45 minutes unless patient becomes sensitive or color change is achieved.

• Remove heat source and wash the teeth with warm water.

1. It is a two component system which is significantly more stable than Superoxol.
2. As it is light activated, it is safer than heat activated methods.
3. Incidence of post operative sensitivity is less.
4. Paste like consistency provides ease of precise placement.
5. Can be used for vital and non vital bleaching.

The Clinical technique
-Apply petroleum jelly to surrounding soft tissues.
-Rubber dam isolation.
-Clean the teeth with pumice slurry in a rubber cup, rinse and dry.
-Acid etch (not mandatory)
-Mix Hi Lite powder and liquid to a paste. The resulting green/blue mixture is applied over the areas to be bleached in 2 mm. Thickness.
-On competition of bleaching the green color will turn white, which takes about 5-8 minutes. This reaction can be speeded by exposure to a composite curing lite.

Patient Applied (Home) bleaching
In the late 1960’s a dentist was using Gly-oxide an OTC oral antiseptic gel which is 10% carbamide peroxide in his patient’s orthodontic posititioners to reduce tissue irritation. He noticed a lightening effect on the tetracycline stained teeth which were in contact with the gel. In 1986 Dr. John Munro presented his observations to a manufacturer (Omini International) to introduce the first commercial bleaching agent(White and Brite) in 1989.
-Indications for home bleaching are similar to those for office bleaching.
-Advantage Substantial reduction in chair time.
-Disadvantage Success is governed by patient compliance and bleaching period is greatly extended.

 Potential risks
-Adverse soft tissue response to long term contact with the chemicals.
-Excessive ingestion of the chemicals can cause possible systemic effects.
-Etching of enamel and dentin with associated hypersensitivity.
-Possible surface alteration of resin, ceramic, glass ionomer and metal restorations.
-Possible bite alterations and TMJ problems from extended use of trays.

Materials
-Carbamide peroxide- 10% concentration is most common. It breaks down to H2O2 and urea which is excreted by kidneys.
-Product examples Opalescence(Ultradent) Femmiles (Fem)

 Bleaching Trays
These may be made in office or by a lab.
-Thinner materials (0.02 inch) are generally more acceptable to patients and have less impact on occlusion.
-Take alginate impressions, pour models, outline extent of tray on the models (1 mm. Past teeth to be bleached) and block out undercuts.
-Vacuum adapt tray material to models.

Patient Instructions
-Instruct the patient to place 2-3 drops of bleaching agent per tooth in the tray along the facial wall and place the tray in the mouth.
-With in a minute of placing the tray, there will be slight foaming action. The patient can expectorate excess liquid.
-Wear 3-4 hours a day, replenishing bleach every 30-60 minutes.
-Discontinue usage if uncomfortable.
-Report to the dentist if tissue irritation or tooth sensitivity occurs.
-Expect 1-2 shade lightening.
-Treatment time 4-24 weeks.

Follow-up
-Call the patient after 1-2 weeks to evaluate tissue response and monitor compliance.
-Monitor lightening, check for complications and provide fresh bleaching agent.
-If complications occur, stop treatment for a few days and proceed with shorter wearing time or lower concentration.
-Take post operative photographs to verify changes.

Bleaching of non vital teeth.
 When the discoloration is from within the pulp chamber, from necrotic pulp tissue or from staining agents that are present in the pulp chamber, the bleaching treatment need to take place within the pulp chamber.
Non vital bleaching can be done by three methods.

1. Heat and light technique.
2. Bleaching with Shofu Hi Lite.
3. Walking bleach technique.

Contra indications

1. Extensively restored teeth which do not have enough enamel to respond properly to bleaching.
2. Cracks on enamel or hypoplastic or severely undermined enamel.
3. Discoloration from metallic salts, particularly silver amalgam. The dentinal tubules of the tooth become virtually saturated with the alloys and no amount of bleaching with the available products will significantly improve the shade.
4. If the root canal is not well condensed, refilling must be done.

Heat and light bleaching.
-After the isolation of the tooth, the access cavity is reestablished.
-Gutta percha filling is removed to the level of the crest of the alveolar bone.
-All the residual debris and stains are removed from the pulp chamber with a small round bur at slow speed.
-The root canal orifice is sealed with zinc polycarboxylate, cavit or IRM-thickness at least 1mm.
-The bleaching agent should be kept coronal to the cervical area to prevent external cervical resorption.
-Remaining procedure is similar to the vital bleaching, but here, in addition to the loose mat of cotton placed on the labial surface, another one is placed in the pulp chamber also.

Walking Bleach.
-It is an effective and safe procedure which can be utilised in all situations requiring internal bleaching.
-Recent study show that 30% hydrogen peroxide reduces the microhardness of enamel and dentin, whereas treatment with sodium perborate mixed with H2O2 did not alter the microhardness of either enamel or dentin.
-Its disadvantage is that it requires more chair time.
 After the preliminary preparations, the walking bleach paste made by mixing sodium perborate with H2O2. It can also be mixed with distilled water or anaesthetic solution.
-The thick paste is placed into the pulp chamber, a cotton pellet is placed over it and the access cavity is sealed with zinc phosphate or IRM.
-The maximum bleaching effect is attained within 24 hours after the placement of bleaching agent into the pulp chamber. The patient is called in 3-7 days, for evaluation of the result and retreatment if necessary.

Enamel microabrasion
 The dental profession has removed superficial discolorations of enamel with various abrasives/acid dissolution techniques for years.
-1916-Kane applied Muriatic acid to teeth and heated the solution with an alcohol torch to remove surface stains.
-1966-Mc Innes reported the use of 30% H2O2, 36% HCL, and Ether in a 5:5:1 solution for the same purpose.
-1984-Mc Closkey suggested a direct application of 18% HCL.
-1988-Croll Cavanaugh described a technique of enamel microabrasion using 18% HCL and pumice mixture rubbed on stains. They obtained good results and described it as Croll technique.
-1990-The Premier company working in conjunction with Dr. Croll marketed a commercial enamel microabrasion product called PREMA.
-The PREMA contains a reduced concentration of HCL(approx.10%) in an abrasive prophylaxis paste.
-The mechanism of action is three fold. First, there is physical removal of stained outer enamel layer by the stripping action of acid and abrasive action of pumice. A 5 seconds application with Croll technique removes 7-22 microns (10 microns).
-Secondly, the etching action of acid removes interprismatic substances and changes light refraction characteristics.
-Thirdly, there’s oxidation of some pigments.

Indications
-Enamel microabrasion is suitable only for superficial stains located in the outer layer of enamel. These are external stains not removable by prophylaxis.
-White hypocalcified spots.
-Cream, yellow and brown flourosis, particularly speckled stains.

Risks involved
-Post operative sensitivity if cementum is exposed to the acid paste.

Technique
-Apply petroleum jelly to soft tissues, isolate with rubber dam.
-Place PREMA compound for 5 secs with wooden applicator. Prophy cup in 10:1 gear reduction hand piece can also be used.
-Rinse thoroughly for 5 seconds and check for color change.
-Repeat as necessary , up to 5 applications.
-Stop after 2-3 applications if no color change is noticed.
-Rinse for 30 seconds and dry.
-Apply neutral NaF gel for 3 minutes.
-Polish enamel.
So, we have seen a wide variety of bleaching techniques. Recent trend is to combine office(power) bleaching with home bleaching. This is accomplished by treating the teeth for 30 minutes with a concentrated formula of H2O2 and then providing two weeks of treatment for 30 minutes each day at home.

  References:

1. Grossman, Oliet et al: Endodontic Practice II Ed. Varghese publishing house,1988
2. Gerald Mc Laughlin,George Freedman: Color atlas of tooth whitening.Tshyaku Euvo America Inc 1991
3. Lewinstein I, Hirshfeld Z et al., Effect of hydrogen peroxide and sodium perborate on the microhardness of human enamel and dentin. J Endodont 20:61-3, 1994
4. Ronald Goldstein: Change your smile.II Ed. Quint publ. Co.1988
5. Ronald Feinman et al., Bleaching teeth. Quint publ Co. 1987
6. Rotstein I, Zalkind et al., In vitro efficiency of sodium perborate preparation used for intracoronal bleaching of discolored nonvital teeth. Endo and Dental Traumatology 7(4):177-180, 1991
7. Theodore P Croll: Enamel Microabrasion followed by dental bleaching case reports.Quint Int 23(5):317-322, 1992
8. Theodore P Croll: Enamel Microabrasion. Quint books. 1991
   
   
   

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