Bleaching (also called whitening) is the only purely cosmetic procedure in dentistry. In other words, there is no functional component to bleaching. Lighter or whiter teeth are not any healthier than dark teeth, nor do they allow more effective chewing or more distinctive speech. Nevertheless, it is the rare individual who does not desire whiter teeth.
There are essentially two main types of bleach: power and home. A third type, assisted, has been used as a booster for home bleach. However, since several home bleaches are virtually the same concentration as those targeted for assisted procedures, the line between these subcategories is fuzzy at best.
Evaluating the Whitening Effect
With virtually all the manufacturers of bleaching materials and equipment claiming double digit shade changes, you may wonder the following questions:
1. How are shade changes calculated?
Most manufacturers and researchers use a Vita shade guide that has been rearranged from lightest to darkest. It seems the consensus of this rearrangement is:
Therefore, if a patient can be lightened from A3 to B1, that would count as 8 or 9 shades changes (depending on how you do the math). However, it is debatable whether this method of bleaching effectiveness is really valid. Therefore, we have discontinued using this scale and prefer to use a qualitative measurement comparing a bleached arch to an unbleached control. In this system, we can determine whether the bleached arch has lightened significantly, somewhat, or not at all. See #3 below.
2. When are the shade changes determined?
This is the biggie! If a manufacturer wants to tout the success of its bleach, it will take the "after" shade immediately at the conclusion of the procedure. However, this period is the most unreliable time to take the "after" shade. Typically, the teeth are dehydrated to some extent and this effect can distort the bleaching results. We believe the best way to evaluate the effectiveness of the bleaching procedure is to check for any color change after one week, then one month and three months later.
3. How do you determine the success of the procedure?
Most manufacturers want you to bleach the maxillary and mandibular teeth together, a protocol certainly also supported by patients. This means that you will need to use the aforementioned shade guide held up beside some of the anterior teeth and decide which comes closest. This is a notoriously difficult procedure and prone to error.
The far better way and much more reliable is to bleach only one arch initially, using the untreated arch as the control. In this scenario, the maxillary arch is usually the target of the initial bleaching, while the mandibular teeth wait their turn. If the bleaching process was successful for the maxillary teeth, then the mandibular can be whitened at a subsequent appointment or with home bleach and trays. But if the maxillary teeth were not whitened, comparing them edge-to-edge with the mandibular teeth will demonstrate another approach to whitening should be contemplated.
Power Bleaching Systems
With glitzy practice modes such as the dental spa movement, power bleaching continues to be heavily promoted. Nevertheless, the list of products in this subcategory is still relatively short.
Criteria for Choosing a Power Bleaching System
There are certain aspects of bleaching that all these systems share, but dissimilarities do exist. And many of the details of these protocols seem to be based more on empirical voodoo than solid clinical evidence.
Do you need to use a light?
This is, by far, the most controversial of all issues facing power bleaching. In our clinical evaluations, bleaching effectiveness did not seem to be influenced by a bleaching light, although our lab studies have shown that lights do indeed have a slight effect. Therefore, since lights have no apparent untoward effects, they still may be utilized IF you do not make unsubstantiated claims to the patient.
How important is application time?
Even though manufacturers vary with their application recommendations, we continue to recommend that bleaching is time-dependent. We suggest longer is better, although patients tend to become uncomfortable after 60 minutes. It is also uncertain whether reapplying the bleach every 15 minutes or so is better than one application for the entire bleaching session, although intuitively, the former seems to be more effective than the latter.
Does concentration of peroxide matter?
The products we tested ranged from 20%-38%. But, if "more is better", why would some manufacturers choose a concentration lower than others? There are two possible reasons: sensitivity and enamel damage. As the percentage of peroxide increases, the probability of sensitivity goes up proportionally. It follows, then, that lower concentrations should result in less sensitivity.
The same applies to enamel damage, the incidence of which has been reported periodically in the scientific literature. Even though the evidence for this damage is anything but definitive, using a potentially less destructive product (lower concentration) could help to silence the naysayers.
Nevertheless, until there is more definitive proof concerning the deleterious effects of high concentration materials, we suggest not being swayed by the proclamations of manufacturers touting the safety advantages of lower concentration products. After all, what good does it do anyone if a product with a lower concentration causes less sensitivity but its bleaching effect is minimal at best?
Does the pH matter?
Along with concentration of peroxide, pH has been implicated in causing sensitivity. It follows, therefore, that a more neutral pH bleach would be less likely to cause sensitivity.
How thick does the layer of bleach need to be?
A general guideline would be a fairly thick layer, about 1.5-2.0mm. However, we believe the most important factor is to cover the facial surfaces of the teeth completely and keep the gel from drying out.
Is sensitivity inevitable?
Most patients will accept minor discomfort (no pain, no gain), but few will endure any level beyond slight sensitivity. Even though sensitivity did occur in our evaluations at various levels in the first 24 hours, it was virtually nonexistent after 24 hours. This means it will be short-term and should not be a factor for any patients. Nevertheless, several systems have companion products for desensitization to be on the safe side. And suggesting to patients to prophylactically medicate themselves with an OTC analgesic such as acetaminophen or ibuprofen can minimize any minor discomfort caused by bleaching.
Should you encourage home bleaching to enhance the efficacy?
If a patient was willing to wear a tray, why even bother with the power technique? With the leading candidates for power bleaching being those patients who do not want to be bothered using a tray, it would seem that combining these two approaches would be an exercise in futility. That is, unless you realize superior results when both methods are utilized. It is no surprise, then, that home bleach and tray material are either standard or optional in most power bleach kits.
Does it require mixing?
Most current products do not require messy hand-mixing of powder and liquid, although at least one product still includes a component that utilizes this outdated concept. Other products either do not have to be mixed at all or use some type of automixing, which is easier, less messy and less labor-intensive.
Does it need to be stored in the refrigerator?
Virtually all current power bleaches require cold storage. It is very important that the peroxide is fresh when used. Otherwise, its ability to bleach teeth is reduced. All peroxides tend to oxidize when the bottle or syringe is opened or uncapped. The important message is to keep all bottles and syringes of peroxide tightly capped and refrigerated.
However, just like most materials, you should bring the bleach back to room temperature prior to using it. The safest routine would be to take enough bleach out of the refrigerator to whiten all the patients that are scheduled the next day. If the next practice day occurs after a weekend or holiday, then the first staffer to arrive at the office in the morning should take the bleach out of the refrigerator. In this instance, it may be prudent to place the syringe of bleach in warm water if the first patient of the day is scheduled for bleaching. Cold bleach will probably not be as effective as room temperature or warm bleach. Cold bleach can also affect the viscosity of the material, which is another reason to bring it to room temperature.
What is the cost/patient/appointment?
This is usually the cost of the materials you would typically use during a power bleaching session assuming you bleach both arches for one hour, changing the bleach every 15 minutes (four applications). However, one system has a fixed charge for the use of its light along with the bleaching kit.
How do you protect the soft tissue?
Due to their caustic nature, power bleaching materials have the potential to cause significant soft tissue injuries (that tend to heal uneventfully in 1-2 weeks). Even though power bleaching can be performed using several different types of gingival protection, the safest and most reliable is still a properly placed and sealed rubber dam.
A well-sealed dental dam allows the placement of the bleaching gel on the lingual as well as the facial of the teeth to be bleached. While we have no definitive proof that this total coverage hastens the bleaching effect, our clinical impression suggests this protocol is most effective. In addition, you can retract the gingiva around each tooth by ligating with waxed floss. This retraction allows you to bleach the entire tooth.
However, most patients (and staff members) view the dental dam as cumbersome to apply and uncomfortable. Therefore, a resin shield is the more popular method to protect the tissue and material for this shield is usually included in power bleach kits.
Most, if not all of these materials are dispensed directly on the tissue from its syringe. If the material is runny, you need to cure for a few seconds as you place it around each tooth. If you try to apply to more than one tooth before curing, it will flow over the tooth, requiring you to chip off the excess using a #15 scalpel. This is time-consuming and a nuisance, since some of these materials set very hard.
Unlike a dental dam that is ligated around each tooth, there is no gingival retraction with a resin shield. As a matter of fact, you need to cover at least a narrow band of cervical tooth structure to ensure the gingiva is well protected. This area that is covered with the resin shield will not be bleached.
Once you finish the arch, cure for an additional 20 seconds, although the heat produced by curing some of these products can cause discomfort. When you are finished bleaching, merely dislodge one end with an explorer or other instrument and the entire resin shield usually will peel off the gingiva in one piece.
What protection is necessary for dental team members?
Gloves, masks, and safety glasses will usually suffice when handling these caustic materials.