One question we get quite often at Northside Dental Care is, “Do the tooth whitening kits from the drug store work as well as the more expensive professional ones you get at a dental office?” I suspect that most people have a hard time justifying the extra expense of purchasing a professional whitening system from their dentist—a cost of anywhere from $200 to over $500—versus spending less than $75 at the drug store. The answer is drug-store kits, such as Crest Whitestrips, do work…they just don’t work as quickly and comfortably as the professional systems. Why would this be?
Over-the-counter (OTC) whitening systems, such as Crest Whitestrips, use hydrogen peroxide as their active ingredient. This is the same active ingredient used in many of the professional tooth whitening systems but in a much lower concentration. With Crest Whitestrips, this relatively low concentration of hydrogen peroxide is mixed into a glycerin gel, which forms the gel on the backside of the application strips. The glycerin “goo” gets applied to the teeth just like a Band-Aid gets applied to a cut finger; the gel not only covers the teeth but covers a portion of the gum tissue as well. For this reason, the concentration of hydrogen peroxide in the gel must be kept relatively low. If it were higher, the hydrogen peroxide would chemically burn the gum tissue. This gel does whiten the teeth but because it’s a relatively low strength it takes significantly more applications and thus takes longer than the higher strength professional systems. You may be wondering how the professional systems are any different.
The main difference between the OTC systems and the professional systems is the way in which the chemically active gel is applied to the teeth. Professional systems use a custom-made “tray” that holds the hydrogen peroxide gel in contact with the teeth and prevents it from contacting the gum tissue. The tray is a thin flexible shell of clear plastic that gently rests over the teeth and forms a seal along the gum line.
Fig. 1—Whitening tray over teeth with seal along gum line (arrows).
The custom tray is fabricated with small reservoirs to hold the hydrogen peroxide gel on the fronts of each tooth to be whitened. Since the trays are custom made for each individual patient, impressions must be made of the teeth on the first visit so that duplicate models of the teeth can be made with a plaster-like substance. The plastic trays are made using a special machine in our office.
Fig. 2—Plaster models of teeth used to create clear plastic whitening trays.
On the second visit, the plastic trays are tried in the mouth to assure good fit and comfort. Detailed instructions are given to the patient on how to load the proper amount of bleaching gel into the trays and how to insert them, as well as how frequently they should be worn. In addition, the patient is given a small kit that includes:
- a protective case to store the bleaching trays in
- a shade guide, so the patient can monitor the whitening process at home
- an ample supply of bleach (four tubes)
- one tube of whitening toothpaste
- one tube of desensitizing gel
- a travel carrying case to hold all supplies
Fig. 3—Loading bleaching gel into the plastic tray.
At Northside Dental Care, we offer a variety of whitening gel strengths, which are chosen based upon the severity of tooth discoloration and age of the patient. Generally speaking, younger patients have less tooth staining than older patients and are more prone to developing tooth sensitivity during the whitening process. Younger teeth have larger pulps (nerves) that have nerve endings closer to the surface of the tooth, thus are more prone to sensitivity from whitening gel. Older teeth have pulps that are further receded toward the inside of the tooth and nerve channels within the dentin that are more calcified (shielded) from the whitening gel. Therefore, since younger teeth are generally whiter to begin with and more prone to sensitivity, we prescribe lower strength gel for younger patients. Conversely, since older teeth are generally darker to begin with and less prone to sensitivity, we can prescribe a higher strength gel for older patients. All concentrations of gel will work; it’s simply a matter of optimizing patient comfort and whitening effectiveness.
How long does it take to whiten teeth? That depends on how dark the teeth are to begin with, what degree of whitening is desired, and how frequently the whitening gel is applied. The most dramatic whitening is usually noticed within the first week or two and most people reach their desired shade within a month. Those results can be attained by whitening for thirty minutes per day, each day of the week. Darker teeth—or teeth that are stained intrinsically (from deep within the tooth)—will take longer to whiten, but most severe cases can be satisfactorily completed with about three months. It’s rare to find teeth that can’t be whitened at all; even teeth discolored from Tetracycline can be whitened to some degree with modern professional systems.
Please feel free to give us a call to ask questions about professional whitening, or ask about teeth whitening at your next visit. We’re here to help!