The client should be aware that existing tooth-colored restorations may not match the lighter shade of teeth after whitening.
Tooth whitening can be traced back to biblical times. It was first documented in the dental literature around 1872 when oxalic acid was used to lighten nonvital teeth. In fact, in-office bleaching with hydrogen peroxide has been an accepted technique for more than 30 years. Volumes of information support the viability, safety, and effectiveness of professionally supervised take-home tooth whitening.
Despite this background, some hygienists are still doubtful and apprehensive when it comes to discussing or implementing whitening protocols or conversations with clients.
The two major players in whitening are carbamide peroxide and hydrogen peroxide. The mode of action, oxidation, occurs when oxygen combines with stain molecules (chromagens) in enamel and dentin to make organic stains more soluble or invisible. The resulting oxidation penetrates both enamel and dentin to remove organic material within the tubial structures and is dissolved into the saliva and oral environment. The results include notable changes in the refractory index of the enamel, lighter color at the dentinal level, opaqueness of the enamel layer, and teeth that appear whiter and brighter.
Carbamide peroxide, a sustained release agent, whitens by breaking down into urea and hydrogen peroxide. These substances are well-tolerated and excised by the body. The hydrogen peroxide is further broken down into oxygen and water. Carbamide peroxide has a slower rate of reaction than hydrogen peroxide.
The delivery of carbamide peroxide usually occurs via a custom-made tray (usually for two hours or overnight). Carbamide peroxide products are available in concentrations ranging from 10 percent to 30 percent.
Hydrogen peroxide, an immediate-release agent, breaks down into water and oxygen, often accelerated by enzymes such as peroxidase. Hydrogen peroxide releases oxygen within the first few seconds of contact with tooth surfaces, and its substantiality can last up to 30 minutes.
Hydrogen peroxide products can be incorporated into tray-whitening strategies if the patient desires a limited wear time or prefers to whiten during the day (such as twice a day for 30 minutes, as well as in-office power procedures). Hydrogen peroxide products come in concentrations of 5.5 percent and 7.5 percent.
In 1994, the American Dental Association's Council on Dental Therapeutics published criteria for an acceptance program for home-use tooth whitening products. The intent of the guidelines is to document safety and efficacy.
Before gels can be awarded the ADA Seal of Acceptance, the program requires manufacturers to determine the degradation of bleaching gels in trays during use. In order for the whitening gel to be judged efficacious, the guidelines specify that results must indicate a tooth-shade change of at least two shades according to a value-oriented Vita™ shade guide.
The abundance of research documented during the past 10 years — as well as the thousands of successfully completed clinical cases — authenticates the safety and efficacy claims. In terms of safety, the research concludes that hydrogen peroxide up to 3 percent (10 percent for carbamide peroxide) is noncarcinogenic or co-carcinogenic. Many studies are continuously looking into any negative effects whitening has on tooth structure, the pulp, and restorations. No definitive conclusions have surfaced about long-term negative or irreversible results.
The dental hygiene assessment phase for new or current clients is an ideal time to begin offering whitening procedures to clients. Depending on what services your practice provides, some combinations include:
- Power whitening only
- Home whitening only
- Power whitening plus home whitening
- Laser whitening (not discussed here; but I do recommend reviewing "Laser Whitening" by Robyn Cabral in the September 2001 issue of RDH).
Begin by discovering the client's interest and goals about his or her smile. Then review the client's medical history to identify contraindications for tooth whitening, such as pregnancy or nursing patients. We also need to ensure the teeth will not be doubly treated, so determine if the client has used, or is currently using, any over-the-counter whitening products. Be sure to document information about the product and patient usage. It is equally valuable to assess the client's level of interest in advanced procedures.
Before any whitening treatment is diagnosed, a complete examination including radiographs (for evaluating the pulp chamber size) and a clinical evaluation should be performed. An intraoral examination of the teeth and soft tissues determines periodontal status.
Decay, calculus, and extrinsic stains should also be absent from the client's teeth before beginning treatment. It is strongly recommended that any client interested in initiating whitening procedures first receive full preventive and therapeutic dental hygiene care.
Additional considerations, such as recession and/or TMJ dysfunction, should be discussed with the patient prior to beginning a whitening program. Recessed areas do not whiten as well and may also be more sensitive during vital tooth whitening.
Also, before beginning treatment, the client should be aware that existing tooth-colored restorations may not match the lighter shade of teeth after treatment and, as a result, may need to be replaced.
The whitening procedure should cease at least two weeks before placing or replacing composites, veneers, or crowns in order to achieve a seamless match between definitive restorations and the new tooth color. This generally accepted time frame allows for complete color stabilization and hydration of the tooth structure.
After the completion of appropriate dental hygiene procedures, determine the pre-treatment shade using a shade guide and record it in the client's chart. Take pre-treatment photos prior to delivering the whitening trays and post-treatment photos following the completion of the whitening treatment. In determining a personalized whitening option and agent, the clinician must identify the client's preference for overnight or daytime whitening, or if instant whitening gratification is desired.
Clinicians need to thoroughly explain the whitening services and guide the client toward the most appropriate method.
While clinicians understand that whitening is never 100 percent guaranteed, observed tooth color change can be dependent on some basic factors, including type of whitening service, initial tooth color, etiology of stain, concentration of whitening product, accuracy of tray fabrication, and number of applications (laser and power).
Next month, we'll discuss benefits and disadvantages of power whitening systems and home-tray methods.
Kristine A. Hodsdon, RDH, BS, presents seminars nationally about
esthetic hygiene. She also has developed Pre-D Systems, a pre-diagnostic computerized clinical checklist for oral health professionals. She can be contacted through www.pre-d.com.