Dentist dispensed and supervised tray-based at-home teeth whitening using 10% carbamide peroxide first became popular and a widely utilized technique in the early 1990's. Since then numerous published case studies and clinical trials have established the effectiveness and safety of this technique and this type of whitening product. It is research into tray-based teeth whitening using 10% carbamide peroxide that is the source of the information found here on our whitener safety pages.
A concern associated with the use of peroxide-based teeth whitening products is related to the presence (or creation) of hydrogen peroxide and the fact that hydrogen peroxide produces "free radicals".
A free radical can be thought of as a fragment of a molecule. These fragments are very reactive because they actively seek to reconnect with their missing parts. Free radicals have been implicated in various stages of cancer formation. Additionally the oxidative damage they can cause to biological molecules may be associated with aging, strokes, and other degenerative diseases.
First off, as bad as the presence of hydrogen peroxide in our bodies might sound this compound does in fact play an important role in normal metabolism. The human liver produces on the order of about 6.5 grams of hydrogen peroxide per day. Hydrogen peroxide is also a by-product of the metabolism of oxygen and therefore is even a component of our breath. Additionally, hydrogen peroxide plays an important role in our body's defenses against bacteria and viruses.
Research into this topic has largely diminished concerns about the presence of hydrogen peroxide in teeth whitening products. Of primary consideration here is the fact that the hydrogen peroxide exposure from whiteners is limited to the oral environment. It is not known to produce a systemic effect.
The reasons for this is that many of the enzymes our bodies create to protect us from the effects of hydrogen peroxide exist in saliva. Studies have estimated that a tray-based whitening technique utilizing 10% carbamide peroxide as the whitener will produce a dosing of 3.5 mg of hydrogen peroxide. It's been calculated that the enzymes found in the oral cavity are capable of decomposing more than 29 mg of hydrogen peroxide each minute.`
While no study involving carbamide peroxide has shown evidence of initiation of cancer formation by the hydrogen peroxide it produces, some studies do suggest that the presence of hydrogen peroxide can enhance the action of known carcinogens. One study specifically felt it had found evidence that hydrogen peroxide promoted the effect of one of the carcinogens found in cigarette smoke. For this reason it is advised that a person should refrain from smoking while they perform bleaching treatments.
Dental researchers evaluated samples looking for changes in the enamel of teeth that have been treated with peroxide-based teeth whitening products. They have looked for altered morphology (enamel surface changes) and changes in the enamel's microhardness. The general consensus of the dental literature is that appropriate application of a
neutral pH (non-acidic, non-alkaline) 10% carbamide peroxide bleaching gel produces no adverse effects.
There is mention in the literature where dental researchers have identified enamel changes ("shallow depressions", "increased porosity", and "slight erosions") produced by the use of some at-home bleaching products. The presence of these changes varied by individual whitening product and were associated with those products that either utilized an acidic pre-rinse as part of the bleaching technique or else utilized a bleaching gel that was itself acidic in nature.
(Related link about this topic).
Gum sensitivity is a common side effect produced by the use of peroxide-based teeth whitening products. Typically this irritation is mild and transient and diminishes after the whitening process has been completed. This topic is discussed in more detail on our
peroxide teeth whiteners side effects page.
By way of studies involving animals researchers have investigated the potential for peroxide-based teeth whiteners to create pathologic changes in oral soft tissues. None of these investigations have found evidence of pathologic changes with oral mucosa when 10% to 22% carbamide peroxide whiteners were applied for up to 6 weeks.
Dental science has shown that the peroxides generated by teeth whitening gels penetrate through the hard portions of the tooth (the tooth enamel and dentin layers) and ultimately reach a tooth's pulp tissue (nerve tissue), all within just a few minutes after application. Despite this knowledge there have been relatively few studies that have evaluated the effects of teeth whitening products on a tooth's nerve.
One evaluation into this phenomenon determined that using a 10% carbamide peroxide bleaching gel resulted in, at most, 4 micrograms of hydrogen peroxide reaching the tooth's pulp tissue. This same study calculated that it took 50,000 micrograms of hydrogen peroxide to inhibit the enzymes found in the pulp tissue (a "bad thing"). The overall conclusion of the study was that the amount of hydrogen peroxide reaching the tooth's pulp tissue during the whitening process was at a low enough level as to not be a concern.
There is another methodology by which this same conclusion could be reached. Dentists have been using at-home teeth whitening products utilizing 10% carbamide peroxide as the whitener on a wide spread basis with patients for well over 10 years. There is no evidence (either clinical or x-ray based) that person's who have undergone this teeth whitening process have a higher incident of nerve tissue pathology (a condition that would lead to the need for root canal treatment).
While some detrimental effects of peroxide-based teeth whiteners on dental work have been identified the clinical significance of these effects has not been conclusively demonstrated. Some studies have shown that peroxide products do microscopically deteriorate the surface of white fillings (dental composite fillings). Others have shown that some dental cements may be dissolved by 10% carbamide peroxide. Fresh amalgam fillings (silver dental fillings) may release mercury during the bleaching process and this may be a reason to delay the initiation of bleaching treatments.