A BRIGHTER SMILE

When do you suggest a whitening procedure to your patients?

There are three times when recommending bleaching is appropriate. The first is when a patient comes in for an initial examination. At this point, I comment on the shade of the teeth to my dental assistant, I make notes in the chart, and I may ask the patient if he wants to change the color of his teeth or improve his smile. However, you must be careful not to insult patients with your comments because they might be perfectly happy with the color of their teeth. The examination time is the most delicate.

The more logical time is when patients have their teeth cleaned because one of the primary motivations for a teeth cleaning is to look good. People receiving cleanings are the most interested in whiter teeth. Typically during the cleaning appointment, I ask if the patient is happy with the color of his teeth or if he uses a whitening toothpaste. This line of questioning is also appropriate on a medical history form.

Lastly, whenever I do any type of restorative procedure that requires taking the tooth shade for a composite, a crown, or a veneer, I always ask the patient if he is happy with the color of his teeth because we are matching the restoration to it and if we ever want to change it, now is the time.

How can we identify patients for whom bleaching is not a good recommendation?

For most patients, bleaching is a reasonable consideration—if they are unhappy with the color of their teeth. On the other hand, people who have expensive restorative work that would cost more to replace than what would be gained from bleaching are not good candidates. I am often asked if age is a factor. As long as the teeth are discolored, they are good candidates—young and old.

Bleaching does not have major contraindications but there are some precautions. We typically don’t treat pregnant women because receiving elective treatment during pregnancy is never a good idea. From a psychological standpoint, you never want the mother or the office to feel responsible if something goes wrong with the pregnancy. Probably the biggest caution is people with a history of sensitive teeth. There are ways to mitigate sensitivity and direct the treatment so this possibility is minimized.

Why do some patients experience tooth sensitivity during bleaching?

The primary reason for tooth sensitivity is the easy passage of peroxide through the tooth. It is more patient specific than material specific. However, some materials can create more sensitivity, such as those with lower pH, higher concentrations, and more dosage per unit time.

Sensitivity goes away once treatment is stopped and it doesn’t come back. The low pH products have another danger in that they etch the enamel, which etches off the smear layer causing a different kind of sensitivity. However, the same is true of white wine, yogurt, orange juice, apple juice, and cola drinks. Much of the general tooth sensitivity encountered correlates to dietary habits. Hygienists play an important role in treating sensitivity because they can quickly find out which teeth are sensitive and what types of foods patients eat. Hygienists can then counsel patients on diet and on their oral hygiene habits. Even though hygienists recommend soft toothbrushes, much of the American public still buys hard toothbrushes, meaning many are still using abrasive scrubbing behavior that just creates more sensitivity and more yellowness because it takes away the white enamel.

Hygienists can easily discuss desensitizing toothpastes with patients. In the United States, all desensitizing toothpastes contain potassium nitrate, the only Food and Drug Administration (FDA)-approved drug for sensitive teeth. This is fairly effective in a toothbrush but it takes 2 to 3 weeks to build the resistance necessary to lessen the sensitivity. We published a study that found that using desensitizing toothpaste in a bleaching tray was highly effective in reducing sensitivity, producing results in 10-30 minutes.¹

How effective are stannous fluoride products in treating sensitivity?

Fluoride products function as tubular blockers. They reduce the fluid flow within the dentin tubules by occluding them. Potassium nitrate products penetrate the enamel and pass through the dentin to the pulp and almost anesthetize the tooth. Potassium nitrate keeps the tooth from beginning the pain cycle. The best approach is to use a toothpaste that has fluoride and potassium nitrate. In addition, you can apply fluoride topically but it has a different mechanism of action. The patient can also put a prescription fluoride toothpaste in the bleaching trays to deal with ongoing sensitivity issues.

Can tooth sensitivity be addressed before bleaching?

Patients who are sensitive before bleaching should be treated by applying a fluoride varnish or another desensitizing product. If a patient has a history of sensitive teeth, advise him to brush with potassium nitrate desensitizing toothpaste. A bleaching tray can be made and then the patient can wear the tray for a week with the potassium nitrate toothpaste before starting the bleaching.

There are different concentrations of bleaching materials. The most common concentration is 10% but a 5% concentration is available. Patients can apply the treatment for 1 hour a day thereby building up a tolerance to the bleaching material.

Tooth sensitivity is also an issue when scaling and root planing. There is a technique that can really help patients with sensitivity undergo scaling and root planing more comfortably. A bleaching style tray is made and patients are instructed to wear it 30 minutes before their scheduled appointment filled with the potassium nitrate toothpaste or a professionally-dispensed potassium nitrate product. It basically numbs their teeth for the scaling and root planing procedure. This is what sparked the idea of using potassium nitrate in a bleaching tray to treat hypersensitivity following bleaching. This technique is helpful for patients who dread dental scalings, complain profusely, or cancel appointments due to pain.

Will the same whitening effect occur with this slower method used for sensitive patients?

Yes, regardless of the concentration or the time, the end point is the same for all bleaching techniques if they are used long enough. Although the average treatment time is 2 weeks for tray bleaching, some teeth can take as long as 6 weeks to get white. Many people stop because they are afraid of damaging their teeth. This fear is unfounded. We bleach people’s teeth for 6 months every night with 10% carbomide peroxide and can’t find any damage to the enamel or problems with the pulp 7 and a half years later.^2,3

Is it contraindicated to bleach children’s teeth?

Not that I can find. I very seldom have any problems in terms of sensitivity because, even though children have large pulps, they have large apices on the teeth.

Permanent teeth erupt during the middle school age range and this is the most sensitive time for psychological development. So even though they are young and only have four permanent teeth, this may be one of the most crucial times to whiten their teeth if they have some marked discoloration. There are some cost-effective ways to make bleaching trays, like trays that are made directly in the patient’s mouth, to cut down on treatment costs for this age range. Generally, the population most seeking bleaching are women in the 16-35 range. But I bleach people’s teeth as old as 80!

Can bleaching cause pulpal damage?

There is no indication that bleaching has ever caused endodontic or root canal therapy for any patient and bleaching has been around since the late 1800s. There is no indication of pulpal damage mainly because of the free passage of the peroxide in and out.

Is there a risk that patients can overwhiten teeth and cause irreparable damage to the enamel?

Enamel starts to decalcify at 5.5 pH; dentin begins at 6.8. By using a reasonable product—there are three American Dental Association-approved products—there is no problem for long-term treatment other than, after a certain timeframe, time and money are wasted because the tooth will not whiten any further. Teeth whiten and get lighter and lighter but, eventually, they stop whitening. When you stop treatment, bleaching regresses about half a shade. This is the shade they stay at anywhere from 2 to 10 years. There will be an immediate relapse because the teeth are basically dehydrated. A 2-3 week waiting period is necessary after bleaching. Then the actual color of the patient’s teeth is revealed.

How should unused bleaching material be stored?

The shelf life is anywhere from 1-3 years, but we have materials that have lasted longer. The worst case scenario in using old materials is that the material is ineffective. Refrigeration will preserve shelf life but using the product while cold will cause acute sensitivity during treatment. I encourage storing materials at room temperature during actual treatment but if a few syringes are left over, I would put them in the refrigerator.

Are over-the-counter products effective?

They can be effective. The main problem I have is the lack of diagnosis. Patients may misdiagnose the cause of discoloration and potentially mask symptoms that should prompt them to see a dentist. A tooth typically becomes dark when it gets abscessed. With external resorption, the first clue, other than a radiograph, is that it turns dark. Of course, decay causes teeth to turn dark, so people may try to bleach decay out of their teeth when they really need restorative work.

However, over-the-counter products can be effective. Hydrogen peroxide (HP) is only active anywhere from 30 minutes to 1 hour, which is why some products are short-term, high concentration. The strips are 6%-6.5% HP. Ten percent carbamide peroxide (CP) is only 3% HP, so the dose of bleaching material is double or triple the concentration used in tray bleaching with a shorter length of application time. The problems that can arise with the higher concentration are increased gingival irritation or tooth sensitivity.

Please discuss tray design.

Tray design should be related to the type of bleaching material used. The tray can extend onto or be kept off of the gingiva. The tray will seal better if it extends onto the gingiva but there is less chance for irritation if it is off. Patients with thin, friable gingiva may be better suited with a scalloped tray design. If a patient has really high bony prominences over the canines, a tray extending upon the gingiva will create irritation. Also the material that the tray is made out of should be soft.

Reservoir spaces in the tray are created by placing small spacers on the teeth of the plaster model. This tray design takes the pressure off of the tooth and reduces sensitivity. By the same token, if a reservoir tray is scalloped, a nonwater soluble bleaching material needs to be used because it will readily wash out. Some of the materials are designed specifically for reservoired scalloped trays and others work better in a nonscalloped, nonreservoired tray.

The third kind of tray I use, especially in mixed dentition and with sensitive teeth, is one made directly in the mouth without taking an alginate impression. This new type of tray can be created in 3 minutes with a cup of water and a pair of crown and bridge scissors. We have bleached many people’s teeth with this type and we also use it for sensitivity treatment. It works well with mixed dentition because when more teeth come in, another tray can be made without great expense.

References

1. Haywood VB, Caughman WF, Frazier KB, Myers ML. Tray delivery of potassium nitrate-fluoride to reduce bleaching sensitivity. Quintessence Int. 2001;32:105-109.
2. Leonard RH Jr, Haywood VB, Caplan DJ, Tart ND. Nightguard vital bleaching of tetracycline-stained teeth: 90 months post treatment. J Esthet Restor Dent. 2003;15:142-152.
   
3. Ritter AV, Leonard RH Jr, St Georges AJ, Caplan DJ, Haywood VB. Safety and stability of nightguard vital bleaching: 9 to 12 years post-treatment. J Esthet Restor Dent. 2002; 14:275-285.

 From Dimensions of Dental Hygiene. March 2004;2(3):28, 30, 35.