Nightguard Vital Bleaching of Tetracycline Stained Teeth

            The tetracycline family was discovered almost 45 years ago.  Chlortetracyline was introduced in 1948, followed by oxytetracycline in 1950 and tetracycline in 1952.²   According to encyclopedia.com, it is any of a group of antibiotics produced by bacteria of the genus Streptomyces. They are effective against a wide range of Gram positive and Gram negative bacteria, interfering with protein synthesis in these microorganisms. Tetracycline is used to treat rickettsial bacterial infections such as Rocky Mountain spotted fever, some eye, respiratory, intestinal, and urinary infections, some kinds of acne, and some diseases where the infecting microorganism is resistant to penicillin.³  It is a good “broad spectrum” antibiotic, and in 1950’s and 1960’s was the drug of choice for many common childhood infections.   About 1961, some evidence began to appear indicating that these drugs cause discoloration when taken during infancy and early childhood.²  That however did not decline their use, and in fact in 1967, 39 million doses of tetracycline were ordered, and it was still the preferred antibiotic.²  Only after 1972, did the FDA placed a warning on the packaging of the antibiotic contraindicating its use after midterm pregnancy and before the age of eight.²

            Tetracycline is incorporated into the tooth by traveling in the blood to the coronal portion of the pulp.  It is carried through the branching capillaries of the subodontoblastic area to the terminal loops, which extend upward between odontoblasts to end in pre-dentin.  The tetracycline molecule that is transported to this area is believed to bond chemically to calcium ions.  This complex diffuses into the tissues to the site of mineralization of the dentin, which is the junction of predentin and dentin.  Thus, a stable tetracycline-calcium orthophosphate complex is formed.⁴ As teeth are exposed to the sun, or more specifically the UV light radiating from the sun, they begin to darken.  This change is likely due to an oxidation product of tetracycline, which is light induced. ⁴  The color and the severity of the stain depends on the dose, brand of tetracycline, route of administration, as well as calcification activity of teeth.⁵  Staining can be localized or generalized in horizontal bands within the tooth, and discoloration may range from yellow to black.⁵

Bleaching Options

            For those people who think bleaching is a new fad, are sadly mistaking.  In fact, there is evidence of bleaching with hydrogen peroxide as early as 1860’s, when the topic of esthetic dentistry became popular.⁶  There are two main categories of bleaching: vital and non-vital. However, for the purposes of this paper only the vital bleaching option will be discussed.  Regardless of what method/technique one uses, the facts of bleaching remain the same.  If the discoloration is of a yellow type, it will usually respond well to bleaching.  Brown discolorations are the next hardest to bleach, followed by the blue-gray.  Finally, multicolored, or “banded” discolorations are the hardest to achieve positive results on.  For the latter, the teeth usually lighten, however, the banded areas can not be eradicated completely.⁷

The active agent in bleaching systems is hydrogen peroxide.  Carbamide peroxide is composed of 3% hydrogen peroxide and 7% urea.  Carbamide peroxide is commonly utilized because it is a more stable form of hydrogen peroxide. Hydrogen peroxide degrades into water and oxygen, while urea degrades into ammonia and carbon dioxide.⁸  When hydrogen peroxide breaks down, free radicals are released which penetrate enamel and dentin, changing stained molecules in the dentin to clear ones. The free radicals oxidize stains in the teeth.  During the bleaching process, enamel does not change color significantly, because the dentin is what is lightened.

The first technique invented for vital bleaching is the in-office technique, also known as power bleaching, and has been around pretty much unchanged for over 125 years.⁸ For this procedure, a 35% hydrogen peroxide solution is applied under a rubber dam isolation for 30-45 minutes; this solution may be activated by heat or light.⁷ Since anesthesia is not used, patient’s pain threshold is used to control heat and monitor tissue burning.⁸ It takes anywhere between three to six appointments to achieve a satisfactory outcome.  Even though this technique is relatively safe and effective, there are many disadvantages which prevent it from being utilized more often.  The first being that many patients do not like the rubber dam in their mouth, and it is really hard to isolate all of the teeth.  Some manufacturers now provide clinician with light cured flowable resin for gingival isolation which has solved much of the above concern.  Secondly, the patient experiences discomfort during and for about one week after the treatment.  In addition, the 35% hydrogen peroxide solution used is very caustic, and may burn the patient and the operator.  Finally, the success is very hard to predict, and therefore hard to determine the number of appointments necessary, as well as the projected cost of the treatment.⁸

The latest innovations to hit the market are the over-the-counter bleaching systems.  The more current and popular kits are the Crest whitening strips and the Colgate Simply White.  Crest whitening strips are the trayless delivery system for hydrogen peroxide.  It utilizes a clear flexible polyethylene strip dispenses H₂O₂ in controlled way.  Strips extend from canine to canine (six teeth), and come in two formulations of 6% (OTC) or 6.5% and 12%, which are the professional strength.  The other product Colgate Simply White, is a non-tray, paint-on 18% carbamide peroxide whitening gel (equivalent to 6.5% H₂O₂).  It is painted on 2 times a day for 30 minute, and can be painted on all of the teeth.  Even though there is evidence supporting their effectiveness, this is not a method of whitening for everyone.  The biggest problem with the over-the-counter bleaching agents is the patient compliance, which is usually caused by products being tricky to use.  Many people do not like the whitening strips because they do not stick well to teeth, and the Colgate product has to dry for 30 seconds before one can close their mouth.  The other concern is many patients do not realize there are teeth conditions that may not whiten, and these include anterior composite restorations or endodontically treated teeth.  Therefore, people would really benefit from a consultation with a dentist before they attempt using over-the-counter bleaching agents.

            Finally, there is nightguard bleaching.  The current technique as we know it was invented by Drs. Haywood and Heymann in 1989, and they called it nightguard vital bleaching (NGVB).⁸ This technique utilizes a custom-fitted prosthesis filled with 10% carbamide peroxide.  Many people have raised concerns with the safety of NGVB.  The first concern is the effect of hydrogen peroxide on tissues.  Since most of the by-products naturally occur in the body, the primary reason for any irritation is usually due to an ill-fitting prosthesis.  As concerning the safety of carbamide peroxide, many studies determined that toxicity and mutagenicity of hydrogen peroxide is dose related, and the concentrations used in home bleaching technique are not of sufficient strength to warrant concerns for soft tissue.⁹ Another concern is increased tooth sensitivity associated with bleaching.  Research shows that sensitivity tends to cease as soon as bleaching is terminated.⁹ Application of fluoride in the prosthesis immediately after bleaching, or use of sensitive teeth dentifrice containing potassium nitrate is also an option. 

            Nightguard vital bleaching has proved to be highly successful, with nine of ten patients experiencing a lightening effect in 2-6 weeks of application time.  For tetracycline stained teeth it may take anywhere up to 6 months.¹⁰  Besides each tooth responding different to bleaching, different parts of the same tooth may respond differently.  Generally, the incisal edge begins to lighten first, with the necks of the teeth being the last area to lighten.  This sequence is generally related to the physical thickness of the tooth from incisal to gingival, the longer availability of material in the prosthesis at the incisal portion, and the ratio of dentin to enamel thickness.⁹

Case Report

            There are 4 degrees of tetracycline staining.  Degree I is a minimal discoloration usually of a light yellow, brown, or gray uniformly confined to the incisal three quarters of the teeth.  This has the best prognosis for vital bleaching.  Degree II is a uniform deep yellow to brown or gray with no banding.  The prognosis is variable, depending on the specific degree and intensity of staining.  Degree III staining is a dark gray or blue discoloration usually with marked banding.  The prognosis for effective and esthetic vital bleaching is not good.  Although the teeth do lighten, results are not generally esthetically acceptable.  Degree IV staining includes severe stains that are too dark to even attempt vital bleaching for an esthetic result.¹¹

            Mr. G. presented to the dental school for comprehensive care.  Mr. G. is 42 years old. He has a non-contributory medical history, and denies smoking and drinking.  Being a son of a dentist, his oral hygiene is impeccable, and outside of a few failing amalgam restorations, the oral cavity is healthy.  Mr. G’s main concern is the color of his teeth (Fig. 1), and he wanted to know what can be done to whiten the teeth.  Mr. G. knew the reason his teeth were yellow was due to ingestion of tetracycline antibiotic for an ear infection at the age of three.  The patient was informed that NGVB may be an option; however the results to be achieved were uncertain.  Even though Mr. G’s staining status would place his in the degree II category, or mild-to-moderate staining category, he was still interested in attempting bleaching.  After determining there is no abnormal pulpal anatomy to his anterior teeth, new maxillary and mandibular alginate impressions in rim-lock stock trays were taken and models fabricated with microstone.  A scalloped, reservoir, custom-fitted soft tray (0.035 inch) was fabricated for both arches.  Patient was provided with 10% carbamide peroxide gel (Opalescence^®,Ultradent) and was informed to apply the gel nightly.  The initial shade was determined to be A4 using the Vita shade guide.  Both arches were to be whitened simultaneously.  After the first night of bleaching, Mr. G. reported sensitivity to tooth #14 which had a very large existing amalgam restoration.  Since no other teeth were sensitive, the patient was instructed not place bleaching gel for tooth #14 in the tray.  This method of selective bleaching completely eliminated his tooth sensitivity for the rest of the treatment.  Patient reported for 2 week, 1 month, 2 months, 3 months, and 4 months follow-ups.    After 2 weeks the teeth were significantly lighter at the incisal edge.  The new shade was determined to be A1.  At one month, the incisal ½ of the tooth reached its optimal color, but the cervical part of the tooth still remained dark.  Bleaching was discontinued after 4 months, because it was determined that there was no difference between the 3^rd and 4^th month follow-up.  The patient was very pleased with the results.  And though some evidence of tetracycline staining remained at the cervical part of the tooth, the final shade was determined to be just lighter than B1(Fig. 2). 

Literature Review

            In 1996, there was a study published by Drs. Haywood, Leonard and Dickinson describing efficacy of six months of night guard vital bleaching of tetracycline-stained teeth.  They selected 10 patients with at least 4 vital anterior teeth, with no dental problems and no pulp size variation. All of these patients had moderate to severe tetracycline staining, and where interested in lightening.  Patients were provided with a custom-fitted tray for the maxillary arch, and provided with enough bleaching material (Opalescence^®,Ultradent) to last 6 months.  Out of the 10 patients that began the study, only 6 managed to last the whole 6 months.  All the patients that finished were very satisfied with the results achieved.  It was also determined that an indicator of a good prognosis was not the severity of discoloration, but the location of the discoloration.¹²

            In October 2001, Drs. Haywood and Caugman put out a case report of a 35 year old man with moderate-to-severe tetracycline staining.  It was determined that the shade of his anterior teeth to be A3.  The patient was told that the teeth may not lighten much, but he was still interested in trying.  In this study they decided to try to attempt at-home whitening with 10% carbamide peroxide.  After 13 ½ months of whitening, the final color was determined to be lighter than B1.  This study reported no obvious color change for 1 month after discontinuing bleaching.¹³

            In 1999, there was a study done by Drs. Leonard, Haywood et al to investigate the result of Nightguard Vital Bleaching of Tetracycline-Stained Teeth: 54 Months Post Treatment.  The purpose of this study was to determine the stability, post treatment side effects, and patient satisfaction after 6 months of active treatment of tetracycline-stained teeth with 10% carbamide peroxide at 54 months post treatment.  They contacted 12 patients who originally completed the study and determined that 83% reported no obvious shade change or only a slight darkening not noticed by others.  Two people reported slight darkening noted by other people, and no one reported severe darkening.  Examiners who compared the pre-operative photographs and post-operative photographs agreed with the patients’ perceptions of shade change.  This study determined that nightguard vital bleaching can whiten tetracycline stained teeth effectively using extended period of time, and the stability may last at least 54 months.¹⁴

            In 2003, Drs. Leonard, Haywood, Caplan, and Tart published a study on nightguard vital bleaching of tetracycline-stained teeth: 90 months post treatment.  These patients had originally undergone 6 months active treatment with 10% carbamide peroxide.  The purpose of this whitening study was to determine the stability, post-treatment side effects, and patient satisfaction 90 months after finishing bleaching. Fifteen of 21 participants enrolled in the study (71%) were contacted and asked to participate in a survey concerning their whitening experience. Participants were asked whether there had been any change in the shade of their teeth after treatment and if they had experienced any side effects that they believed were treatment related. Eight of the 15 participated in a clinical examination. Nine participants (60%) reported no obvious shade change or only a slight darkening not noticed by others. None reported darkening back to the original shade; however, four had re-treated their teeth. Examiners were in agreement with the participants' perception of shade change upon comparing pretreatment and post-treatment photographs. The results of this study of nightguard vital bleaching indicate that tetracycline-stained teeth can be whitened successfully using extended treatment time and that shade stability may last at least 90 months post treatment.¹⁵

Discussion and conclusion

            For those that desire the “Hollywood” white smile there is good news, because no matter if they choose the professional in-office treatment, nightguard treatment, or over over-the-counter bleaching solutions, odds are they can be successful with it.  Even those patients that have tetracycline stained teeth should know that with a little bit of patience, their teeth can be whiter too.  As stated above, Mr. G. who had stained teeth from tetracycline ingestion at an early age began with his teeth being shade A4, and successfully whitened them to slightly lighter than B1.  That is a difference of 15 shades based on value ordered Vita shade guide.  Yes, there are still some dark remnants at the cervical part of the tooth, but it does not compare to what the patient had before.  And the most important part is that the patient is very happy with the results.  To conclude, mild-to-moderate tetracycline staining can be bleached using the nightguard technique and 10% carbamide peroxide, but it could take up to 6 months.  As noted previously, the literature supports patients retaining the lighter shade up to 90 months.

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