The prospect of a treatment posing danger to a patient or to the oral environment is of particular concern when embarking on an elective procedure. The corrosive nature of super-oxol and its potential deleterious effects on various tissues are a definite drawback to the superoxol/heat/light bleaching system.
The tooth, which is more intimately and deliberately exposed to the bleaching agent than any other tissue, is the most at risk. The concerns about chemical and thermal intrusions on the pulp are not without foundation. It has been demonstrated that 35% hydrogen peroxide, alone in combination with heat, caused the obliteration of odontoblasts, hemorrhage, resorption, and inflammatory infiltration.12 While the pulpal changes appeared to be reversible after sixty days, there was no absolute indication that long term damage was not sustained.
In an earlier study, Cohen found the bleaching of vital teeth to be harmless to the pulp. Unfortunately, it appears that the differences between the Cohen study and the Seale study may be due to the fact that Cohen worked with bicuspids, whose enamel to pulp distance is twice as great as that of the central incisors. Furthermore, his findings may not have any direct application to normal clinical practice, since he bleached the teeth for a total of only 45 minutes on the buccal and 45 minutes on the lingual over three sessions. This is much shorter than the recommended times for vital bleaching today.
In addition to the potential pulpal problems, both 35% supcroxol and heat can cause or aggravate hypersensitivity of the dentin. It is for this reason that the presence of dentinal sensitivity is considered a contraindication to vital bleaching. Since dentinal tubules provide a readier conduit from the tooth exterior into the pulp than the enamel, any difficulties created by the passage of peroxide or heat penetration through enamel indicate the likelihood of even greater problems when these materials are applied to dentin.
Even enamel, the hardest and densest of the dental tissues, is not immune to the actions of 35% hydrogen peroxide. Titley et al. found that an etched enamel surface that was immersed in the Superoxol solution (without heat) showed an increased porosity after as little as ten minutes.14 In light of this, the wisdom of extensive bleaching procedures with caustic agents such as 35% hydrogen peroxide, which may total 500 minutes or more over several appointments, should be re-examined.
Should the rubber dam leak, or any superoxol accidentally splatter onto the gingiva, checks, tongue, etc., the resulting chemical burn will remain for several days. It is very important that the rubber dam placement be close to perfect in order to avoid almost certain discomfort to the patient.
The patient (as well as the dentist and staff) should wear protective goggles throughout the bleaching procedure. The remote possibility exists that a drop of superoxol will splash into the eyes, causing not only discomfort, but possibly long-lasting damage. Wrap-around goggles are the best choice of eyewear for the patient.
The chances that the solution will spill onto the exposed skin of the face or hands is everpresent. If immediately rinsed, the result is usually just a white patch which gradually returns to normal color in a few hours. If not quickly rinsed off, however, the liquid can leave a nasty white burn that will itch initially, and then form a scar as the burnt tissue sloughs off.
It is therefore a good idea to cover all the exposed skin on the patient's face and neck with a non-permeable material that will contain the 35% hydrogen peroxide. Naturally, the dentist and staff must be adequately protected as well. If the peroxide drips onto the patient's clothing, it will instantly bleach any area that it has come into contact with, ruining the garment.
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