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.
Although there are at least two home bleaching products above the 30% carbamide peroxide level, assisted bleaches continue to be marketed, despite the fact that one product in this category contains 35% carbamide peroxide, which is virtually the same as home bleaches.
Originally used as a first-appointment booster for a home bleaching program, these products were not necessarily promoted as a stand-alone office bleach. This is due to the fact that carbamide peroxide is not as strong as hydrogen peroxide. Therefore, you would not expect to get the same results from these products as compared to the hydrogen peroxide gels.
We found these materials were able to produce a slight change in shade after one 30-minute bleaching session, with their efficacy virtually the same. It is clear their real contribution could be as high-powered home bleaches for patients who do not have any pretreatment sensitivity and want the absolutely fastest results.
With this impending dispensing change, direct application without a tray would seem to be a time-consuming, labor-intensive, unnecessary option. A more logical approach would have the patient fill and wear the tray for the first session in the office. Assuming the patient does not experience any untoward effects, the patient would then take the bleach with him or her and continue an abbreviated home bleaching schedule. Be careful not to overlap the gingiva with the bleaching tray to keep these products off the soft tissue. Even though they are not as caustic as high concentration hydrogen peroxide gels, these products do have the capability to irritate the gingiva.