Tooth Whitening and Sensitivity Reduction

Tooth whitening, or “bleaching,” continues to be an important part of today’s aesthetic armamentarium. Television programs such as Extreme Makeover and The Swan have exposed tooth whitening and smile makeovers to such a degree that these procedures are becoming commonplace for many people. More and more patients are seeking advice from their dental professionals to help them achieve a whiter and brighter smile.

A myriad of products and systems have been introduced to the dental profession and directly to patients in the tooth-whitening arena that produce desirable aesthetic effects. However, tooth whitening is still unpredictable and is best monitored by the dental professional for consistent results. With patient compliance having such an effect on the outcome for at-home whitening systems, many patients choose in-office tooth whitening for convenience and immediate gratification.

Tooth-whitening systems work by oxidization that neutralizes internal pigments that may become trapped in the enamel prismatic structure. Desiccation of the tooth structure and contact with exposed root structure can cause temporary sensitivity during the oxidation reaction. Dental hypersensitivity (cold temperature sensitivity) can be a common sequela of many in-office and take-home whitening systems. Although usually short-lived, the prospect of tooth sensitivity causes many patients who may otherwise be good candidates to choose not to brighten their smiles.

Several desensitizing agents are on the market that can help eliminate or reduce this transient sensitivity. These chemicals, when applied to the tooth structure, can seal the tooth and insulate it from the agents that cause the pain response. Several of these contain HEMA, a low molecular weight monomer and an antimicrobial agent in an aqueous solution. A few contain fluoride.

Even though I try to remain generic in my writing, there is a unique product that has addressed the sensitivity issue. Therefore, I will discuss it here and demonstrate an innovative new technique designed by Shannon Pace, my dental assistant and director of the dental assisting programs at the Nash Institute for Dental Learning.

MATERIALS

The whitening product is AcquaBrite (AcquaMed Technologies). The desensitizer developed by the company is called AcquaSeal. It contains benzylkonium chloride, hydroxyethyl methacrylate (HEMA), fluoride, and water. The patented formula is said to eliminate dentinal hypersensitivity related to pathology, trauma, or dental procedures, including desiccation due to tooth-whitening products. Benzylkonium chloride is a well-known antimicrobial agent and protein cross-linker. In low concentrations, it can be safely used on tooth surfaces adjacent to soft tissue. HEMA is a low molecular weight monomer that is an effective wetting/rewetting agent found in many adhesive systems. It is hydrophilic in nature and chases water down the dentinal tubules. Because of HEMA penetration, application of AcquaSeal results in dentin tubule occlusion as much as 27 µm deep, according to the manufacturer’s SEM studies. The fluoride ion from the neutral sodium fluoride in the product is said to substitute for the hydroxyl ion on the hydroxyapatite crystals, leading to a stronger, remineralized inorganic tooth structure.

The tooth-whitening product, AcquaBrite, contains the desensitizing chemistry found in AcquaSeal. By using the 20% formulation as an in-office tooth whitener, it can be safely applied to the tooth surfaces without the use of a rubber dam or other types of tissue-protecting paraphernalia. We have seen acceptable results with and without the use of light activation. For patients with gingival recession who may be prone to postoperative dentinal hypersensitivity, AcquaSeal (B) is available in a take-home disposable swab that is easily activated and applied to exposed areas. Because benzylkonium chloride is kind to soft tissues, irritation or burning of the gingiva is not a problem as it may be with other desensitizing agents.

TECHNIQUE

Figure 1. Tetracycline-stained teeth before treatment.

In the case presented, the patient presented with tetracycline-stained teeth (Figure 1). The technique that Ms. Pace developed incorporates a tray similar to the one a take-home product would have. Even though the whitening agent can also be applied directly to the tooth structure, the tray seems to hold the solution in closer contact with the tooth structure, and our best results have occurred with this technique. Unlike other products, no gingival protection is usually needed. If tissue protection is desired or rarely needed, a self-curing polyvinyl material (AcquaDam) is available for use.

Figure 2. Stone model with block-out resin. Figure 3. AcquaBrite whitening agent injected into bleaching tray.
Figure 4. Bleaching tray placed on teeth to be whitened. Figure 5. Excess whitening agent removed with evacuator tip.
Figure 6. Light activation. Figure 7. AcquaSeal applied with swab.

An impression of both arches is performed, and fast-setting stone models are fabricated. The impression can be taken at a previous consultation appointment or at the whitening appointment itself. A resin spacer is placed on the model, and a vacuum-formed tray is made (Figure 2). The whitening agent is dispensed with a self-mixing applicator directly into the trays and placed on the patient’s teeth (Figures 3 and 4). Excess whitening agent is removed with an evacuator tip (Figure 5). The patient is asked to close on cotton roles or bite blocks. If light activation is desired, the light is focused on both arches at once (Figure 6). The whitening solution is allowed to work for 20 minutes, and the trays are removed. The excess material is removed with an evacuator tip, and more solution is applied in the same fashion for another 20 minutes. The trays are then removed, and the teeth are thoroughly rinsed and dried. The desensitizing solution is applied (Figure 7), and the patient is asked not to rinse or drink water for 20 minutes.

Figure 8. Tetracycline-stained teeth after whitening.

We have performed this procedure for several dozen patients so far. Only one patient experienced sensitivity during the procedure. For this patient, we removed the trays and applied the dam material with no further problem. None of the patients have complained of postoperative sensitivity, and the results we have achieved are at least equal to other materials we have used (Figure 8).

CONCLUSION

Tooth whitening is a procedure that continues to provide patients with a noninvasive way to brighten their smiles and increase their self-confidence. The prospect of transient dentinal hypersensitivity can cause some patients to elect not to go forward with treatment. The materials and technique described in this article help resolve this issue and allow more patients to accept in-office procedures.



Dr. Nash is president of the Nash Institute for Dental Learning in Charlotte, NC, and has been a clinical instructor at the Medical College of Georgia School of Dentistry. He is a member of the Esthetic Dentistry Research Group, which publishes Reality. Dr. Nash is a fellow in the American Academy of Cosmetic Dentistry and a diplomate for the American Board of Aesthetic Dentistry. He lectures internationally on cosmetic and aesthetic dentistry and is a consultant to a number of dental products manufacturers. He can be reached by calling his director of continuing education at the Nash Institute, Mark J. Cody, at (888) 442-0242 or by visiting nashinstitute.com.




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