Is it safe for patients to whiten their teeth overnight? While most of us feel like this is a straightforward and easy question, there was a recent discussion about this on Dentaltown. An assistant expressed concern about the wear on enamel if patients bleached overnight, let alone for longer than an hour a day. They claimed the acidity of the gel will eat away at the enamel. While this topic can be explored about the length of bleaching in general, we’re just focusing on whether or not bleaching overnight can hurt the enamel.
As you may already know, overnight whitening products use carbamide peroxide in contrast to its more potent counterpart; hydrogen peroxide. Carbamide peroxide is a mixture of hydrogen peroxide and urea at a 1:3 ratio. With the urea as a stabilizing force for the active agent, it releases the peroxide slower and elevates the pH levels in the mouth during the treatment. In the first two hours, the carbamide peroxide will have released 50 percent of its peroxide and can stay active for up to 6 additional hours.
The concern about the “acidity” of whitening products is that it will cause a demineralization of the tooth enamel. Normal mouth pH can range from 6.2 to 7.0, so the demineralization of enamel will typically occur if the pH levels decline to 5.7 or less. It’s at that point when enamel erosion can occur. Given that the urea in carbamide peroxide gels keeps the pH from falling, there should be no concern for enamel erosion even from overnight bleaching.
Rule of Thumb
The rule of thumb for many dentists has been to bleach until the teeth become sensitive, take a break for a minimum of a week, then continue as needed. This idea allows for flexibility given that patients are unique and widely differ from each other. That’s why the pre-whitening examinations are key. Determine the condition of the patient's mouth, the best whitening regimen specifically for them, and go from there.