Inside Dental Assisting
Professionally Dispensed Vital Tooth Bleaching
Howard E. Strassler, DMD
Even during these current economic challenging times, patients are still interested in having the appearance of their teeth changed with esthetic dentistry. They are inquiring about the more conservative, noninvasive technique of tooth whitening with vital bleaching as a less costly alternative to bonded restorative dentistry. Professionally dispensed vital tooth bleaching refers to the materials, techniques, and devices used or dispensed by the dentist. These techniques can include a variety of concentrations of hydrogen and carbamide peroxide, in-office techniques with and without light or heat enhancement, professionally dispensed whitening strips, and tray bleaching.
Research has demonstrated safety and effectiveness of tooth whitening with peroxide products.1-6 In all cases, the agents evaluated lightened the color of the teeth safely and effectively with minimal, transient adverse reactions reported. When the bleaching procedure was completed, these adverse reactions reported during treatment were no longer present. Based on a comprehensive literature review, the use of bleaching products containing hydrogen and carbamide peroxide does not appear to pose an increased risk of oral cancer in the general population, including those persons who are alcohol abusers and/or heavy cigarette smokers.7
Vital tooth bleaching has become a well-accepted and successful procedure in dental practices with tray bleaching as most popular. In-office bleaching has recently become more popular. The availability of over-the-counter (OCT) tooth-whitening products has also increased significantly in the past decade.
Today the clinician has many choices for whitening. These include a variety of different types of tray and trayless systems with peroxides in a wide range of concentrations. When comparing chemical concentrations, an approximate ratio to use is that 3% hydrogen peroxide is approximately equivalent to 10% carbamide peroxide. The addition of a carbopol to carbamide peroxide vital tooth-bleaching gels extend the bleaching potential of the gel over the course of as long as 8 hours so that a recommendation can be made to wear a tray overnight.8 This is not true of hydrogen peroxide-based vital tooth-bleaching products. Hydrogen peroxide will lose more than 50% of its bleaching potential within 30 minutes. Therefore, the recommendation for hydrogen peroxide bleaching is that it be used for only 30 minutes at a time. Higher concentrations of hydrogen and carbamide peroxides allow the patient to decrease the total wear time of the tray by days or even weeks and decrease the time necessary for a whitening result. Higher-concentration hydrogen peroxides (25% to 35%) are used for in-office bleaching with and without light and heat enhancement.
Patient Selection for Vital Tooth Bleaching
When treatment planning patients for tooth whitening with bleaching there are certain tooth discolorations that have better prognoses for success. Key factors that have an effect on the final result after bleaching include concentration of the bleaching agent, duration of use of the bleaching agent, type of tooth discoloration, color of the teeth, and the patient's age.1 It has been reported that tooth discolorations with the best prognosis for whitening are:
- yellowing of the teeth without any systemic or developmental cause (food, smoking, aging staining);
- mild fluorosis staining;
- mild tooth darkening due to trauma;
- mild tetracycline staining.4,5
It has been reported that moderate to severe tetracycline discoloration can be lightened in shade with overnight use of a vital mouthguard bleaching over a period of 6 months.9
Tray bleaching is highly effective (Figure 1 and Figure 2). Adverse reactions have been reported including gingival irritation, uneven tooth bleaching, an uneven coloration during early stages of bleaching, and tooth hypersensitivity while bleaching. Gingival irritation has been reported due to poor tray fabrication, or due to the need for scalloping the tray for higher concentrations of hydrogen and carbamide peroxide bleaching gels.10 During the initial bleaching, especially with higher concentrations of tray bleaching gels, patients have reported uneven coloration in the appearance of the teeth during the first week.10 This uneven coloration of the teeth being bleached disappears after the first week of bleaching.
Transient tooth sensitivity has been the highest reported adverse reaction during bleaching, with at-home tray delivery and in-office procedures in a range of 18% to 78% of patients.11-14 It has been shown that gingival recession is not a factor in the occurrence of tooth hypersensitivity when bleaching.15 Use of a lower concentration of carbamide/hydrogen peroxide can help reduce or prevent sensitivity, as may less frequent application (for instance, once versus twice daily, or every other day) and/or shorter applications. To minimize tooth sensitivity during vital tooth bleaching, the clinician can recommend that the patient decrease the time the tray is worn the first week to no more than an hour a day for carbamide peroxide products or, for higher-concentration hydrogen peroxides, as little as 15 minutes a day or use lower concentrations of peroxide.
A 5% potassium nitrate (KNO3) formulation has been shown to be an effective desensitizer in toothpastes.16-18 Some bleaching gels have added a 5% KNO3 desensitizing agent. Two effective strategies using a KNO3 desensitizing toothpaste that have been clinically evaluated are brushing with the desensitizing toothpaste for 2 weeks prior to initiating bleaching11 and having the patient place a sensitivity toothpaste containing a 5% KNO3 1 week prior to the initiation of bleaching in the tray that will be used for bleaching for 30 minutes a day.19 Another strategy is to have a patient use a professionally dispensed desensitizing gel with 5% KNO3 for use with bleaching.20 Amorphous calcium phosphate (ACP) has been shown to be an effective desensitizer.21-23
Tray adaptation to the cast is important. The casts should be trimmed to a horseshoe configuration to allow for optimal tray adaptation during fabrication. Once vacuumed to the cast, the tray is generally removed and trimmed with scissors. In the author's experience, when trimming the tray on the cast using an electric, soft tray trimmer, there is less concern about distortion that occurs when trimming with a scissor. Based on current research one can conclude the following:
• thin, flexible, vacuum-formed materials are the standard (Figure 3);
• the use of spacers on the stone model to create reservoirs is not necessary but the use of reservoirs can lead to the patient swallowing less of the bleaching gel;24,25
• scalloping the tray to follow the gingival contours is not necessary when using a 10% carbamide peroxide but should be done for higher concentrations of carbamide peroxide or hydrogen peroxide equivalents.21,24
• over-trimming the tray and leaving a portion of the tooth uncovered is not a problem because the bleach will penetrate beyond the tray;26 • custom-fitted trays provide improved bleaching gel—tooth contact;25
• most companies provide bleaching gel for a 2-week time of application;
• higher concentrations of carbamide peroxide bleach worn in a tray show faster initial improvements, but over a 6-week period of time comparing 10% carbamide peroxide to higher concentrations, there is no difference in the final result.27,28
In-Office, One-Hour Whitening
The first bleaching of teeth to change color was an in-office procedure. Currently, the most popular systems for in-office bleaching use high-concentration hydrogen peroxides (25% to 35%) and are often referred to as "1-hour bleaching" (Figure 4). In-office bleaching can be provided to patients as either a one-visit, 1- or 1.5-hour treatment or a multiple-visit procedure.29-31 One can use one of the light-enhanced bleaching techniques (Figure 5 and Figure 6), a laser-activated bleach, or merely a paint-on bleaching gel (Figure 7 and Figure 8). In-office professional whitening can be a perfect complement to the at-home whitening system.32 In-office whitening can offer patients the convenience of whitening their teeth in one or more dental appointments without the need for wearing a tray for 2 weeks.
How effective is in-office bleaching? Studies have been done to compare in-office bleaching to at-home tray bleaching.33-35 All bleaching regimens provide for tooth whitening. The results of in-office bleaching with light enhancements have been controversial. Within the dental literature there are conflicting studies as to whether or not high-concentration hydrogen-peroxide bleaching compounds are effective. Some studies have shown that the use of a light-activated/enhanced bleaching product provides better whitening,29,30,36 while other studies demonstrate that there is no benefit to using an accessory light.36-38 In-office tooth whitening may require multiple visits to get optimal results or, in some cases, in-office bleaching with 1-week at-home tray whitening is recommended after the in-office procedure.31,33,34 There have been reports of sensitivity during this chairside procedure.39,40 Using a protocol of administering preoperative ibuprofen prior to chairside bleaching has reduced the clinical symptoms of sensitivity but not the postoperative sensitivity.41 Use of a desensitizing gel prior to tooth bleaching has also been effective.42
To understand and evaluate bleaching relapse, the clinician should record the patient's tooth shade before initiating any bleaching procedure. From all clinical and research accounts, tooth whitening with the latest generation of vital bleaching products is safe, effective,4-6,29-31,38,43,44 and also relatively long-lasting. Bleaching relapse has been reported. With in-office bleaching, CRA reported relapse of 41% at 1 year.38 For tray bleaching, Haywood reports 26% at 18 months.45 Others have reported varying degrees of bleaching relapse over time.46-48 The original concentration of the bleaching agent had no effect on bleaching relapse.49 It is not uncommon for the patient to see greater whitening immediately after the removal of the tray or after completion of in-office whitening due to the dehydration effect on the enamel surfaces. Final shade evaluation is best done 1 to 2 days after bleaching. To prevent bleaching relapse, a patient would have better success with a power toothbrush with a whitening toothpaste over manual toothbrushing.45 Bleaching can be maintained through the use of whitening toothpastes and bleaching toothpastes with yearly touch-up bleaching using a peroxide bleaching agent in the patient's custom fitted tray.
When patients are in treatment with tooth bleaching, there are special considerations that should be taken into account. For this author, any restorative treatment in the esthetic zone should be delayed until bleaching is completed and the color of the teeth has stabilized. In the author's experience, it is not possible to predict what level of shade change will occur during whitening. Also, research has shown that bleaching can have a negative effect on dentin and enamel bonding.50 Based on these research findings, before any bonded restoration is placed, the clinician should wait a minimum of 1 week after the completion of bleaching.
Vital tooth bleaching is an effective treatment modality that can change the appearance of teeth. Patient satisfaction has been demonstrated after use of both professionally dispensed bleaching treatments and OTC products. Based on the clinical results reported with professional vital tooth bleaching, it is a viable, esthetic treatment for the discolored dentition.47 Its conservative nature and little if any risk make it an important part of an esthetic dentistry treatment plan.
Dr. Strassler has received grant/research support from DenMat and Ultradent.
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About the Author
Howard E. Strassler, DMD
Professor, Division of Operative Dentistry
Department of Endodontics, Prosthodontics and Operative Dentistry
University of Maryland Dental School