Greening of tlie Tooth-Amalgam Interface during Exterided 10% Carbarnide Peroxide Bleaching of Tetracvcline-Stained Teeth: A Case Report

V A N B. HAYWOOD, D M D

ABSTRACT

At-home bleaching with 10% carbamide peroxide in a custom-fitted tray has been shown to have some minor effects on certain brands of amalgam, pertaining to mercury release, but gener- ally, effects on amalgam are not considered clinically significant. However, in this case report, a greening of the tooth structure in certain areas immediately adjacent to amalgam restorations in the maxillary and mandibular first molars occurred during tooth whitening. Other amalgam restorations in mandibular and maxillary second molars in the same mouth did not demonstrate any green discoloration of the teeth. Upon removal of the affected amalgam restorations, recur- rent decay was present in the areas of tooth greening but not in other areas adjacent to the restoration. The teeth were restored with posterior composite restorations. Whether the green discoloration was a result of some loss of material from a particular brand of amalgam, indicating leakage, or indicative of original or recurrent tooth decay is unclear in this single-patient situation. Other patients in the same study did not demonstrate this occurrence. Dentists should be ready to replace amalgam restorations should this green discoloration in adjacent tooth structure occur during bleaching, in case decay is present.

CLINICAL SIGNIFICANCE

The unusual discoloration cited suggests that amalgam restorations in potentially esthetic areas, including the lingual of anterior teeth, should be replaced prior to bleaching, to avoid the prob- lem of difficult stain removal or translucency allowing restoration visibility following bleaching.

Esthet Restor Dent 14: 12-1 7,2002)

t-home or nightguard vital A bleaching involves the use of a 10% carbamide peroxide material applied to the teeth either nightly or daily in a custom-fitted tray for 2 to 6 weeks to whiten the teeth. ' Previous research demon- strated that tetracycline-stained teeth generally require 2 to 6

months of treatment with 10% carbamide peroxide to lessen the staining.2-8 Minimal effects on the various dental materials in typical treatment times have been reported to be associated with at- home b l e a ~ h i n g . ~ Certain brands of amalgam in conjunction with certain brands of carbamide per-

oxide have been cited as releasing mercury.'"~'' The purpose of this case report is to identify the phe- nomenon of tooth greening adja- cent to certain amalgam restora- tions during extended bleaching times and to present the subse- quent findings upon removal of the amalgam restorations.

"l'rofessor, Department of Orizl Rehabditutaon, School of Dentistry, Medical College of Grorgiu, Augusta, Georgia

12 J 0 U K N A L. 0 F E S T H E T I C A N 0 K E S ' I 0 R A 1 1 V E I) E N 'TI 5 T K Y

H A Y W O O D

C 4 S E R E P O R T

h 29-year-old white male presented to participate in a research project to have his tetracycline-stained teeth whitened in an extended treat- ment time evaluation (Figure 1). The patient was given a nonscal- loped, no-reservoir tray design that covered all the teeth (ArchTek Dual Tray system, ArchTek Inc., Lake- wood, Colorado) and an American Dental Association-accepted 10%

carbamide peroxide material (Platinum, Colgate Oral Pharma- ceuticals, Canton, Massachusetts) to apply nightly.12 The patient was seen on monthly recall visits.13J4 After 4 months (approximately 720 hr of nightly application), the maxillary arch was completed. The patient continued bleaching for 6 additional months to eliminate the slight discoloration at the gingival third of the canines (Figure 2). At

that time, the mandibular arch bleaching treatment was initiated. After 1 month of treatment, there was a remarkable improvement. However, the patient did not con- sider the mandibular treatment completed until after 7 months, again requesting additional treat- ment time to maximize the stain removal on the gingival third of the mandibular canines (Figure 3 ) . Dur- ing the seventh month of treatment

Figure 1 . Preoperative condition of teeth prior to at-home bleaching.

Figure 2. Final color outcome of the maxillary arch after bleaching with 10% carbamide peroxide in a custom-fitted thermoplastic tray for 10 months.

Figure 3. Final color outcome of mandibular arch after bleach- ing 7 months at night using a 10% carbamide peroxide.

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G R E E N I N G O F T H E T O O T H - A M A L G A M I N T E R F A C E D U R I N G E X T E N D E D 10% C A R B A M I D E P E R O X I D E B L E A C H I N G O F T E T R A C Y C L I N E - S T A I N E D T E E T H : A C A S E R E P O R T

Figure 4 . Mandibular first molar demonstrates tooth greening primarily in the distal areas where nonfused grooves exist. However, there is no obvi- ous break in the amalgam-tooth interface.

of the maxillary arch, a green dis- coloration was noted around por- tions of the amalgam restorations in the maxillary first molars. This had not been present on the initial clinical examination. There was no similar discoloration noted on the adjacent second molars that also contained amalgam restorations. Similar discolorations occurred on portions of the amalgam restora- tions in the mandibular first molars at the fifth month of the bleaching process (Figure 4) but not on a mandibular second molar that con- tained an amalgam restoration.

At termination of bleaching ther- apy, treatment was halted for at least 2 weeks to allow the shade to stabilize and the bond strengths for planned composite restorations to be maximized.l F, lh Then the amalgam restorations with the adjacent green discoloration were removed and replaced with posterior composite

restorations. During the replace- ment of the amalgam restorations, carious dentin was noted at the dentinoenamal junction (DEJ) and in all areas of the tooth that con- tained the green discoloration near the amalgam (Figure 5 ) . Caries in the dentin was removed with a slow-speed round bur in a latch- type handpiece. This carious dentin often undermined remaining enamel. The outline was extended until a nondiscolored DEJ was present. Deep areas of caries removal in some teeth received a Vitrebond base (3M ESPE, St. Paul, Minnesota), followed by acid etching with 37% phosphoric acid, priming and bond- ing (Optibond FL No. 1 and No. 2, Kerr Corp., Orange, California), and placement of a posterior hybrid composite, shade B1, to the DEJ (Herculite XRV, Kerr Corp.). Because the post-bleaching shade of the teeth was lighter than B1, an ultralight shade of hybrid compos-

ite, shade B2 (Amelogen UltraLite, Ultradent Products Inc., South Jordan, Utah) was used for the final occlusal layer (Figure 6).173*s After finishing and occlusal adjustment, the composite restoration was cleaned with acid etchant, rinsed, dried, and surface-sealed with Opti- Guard (Kerr Corp.). The amalgam restorations in the maxillary second molars were not removed, and no discoloration was evident. At the patient’s request, the facial amal- gam in the mandibular second molar was replaced, along with the sealant. There was no carious dentin found under the amalgam in the second molar upon removal.

D I S C U S S I O N

In the case described, the amalgam restorations appeared to be clinically satisfactory at the prebleaching clini- cal examination. No restorations were present in the premolars or the anterior teeth, so there was no opportunity for comparative evalua- tions. Since preoperative photo- graphs or radiographs were not taken of the posterior teeth prior to initiating bleaching, it cannot be determined if there was extensive discoloration present of a different color in these teeth, or if there was any indication of decay under restorations. Experience has shown that some amalgam restorations seem to stain tooth structure clini- cally more extensively than others, which may be a result of the amal- gam formulation or poor physical proper tie^.'^ Also, it is unknown at

14 J O U R N A L O F E S T H E T I C A N D R E S T O R A T I V F . D E N T I S T R Y

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Figure 5. A, Initial removal of the amalgam demonstrates that the green discoloration radiates from the dentoenamel junction into the enamel but not completely to the surface. B, Further removal of tooth structure is required to follow the decay, which is located in the green areas only. C, The bright green discoloration is still present at the DEJ, with decay remaining in that area.

what time in the bleaching process the traces of the discoloration may have appeared. Since the anterior teeth were the subject of the research project, subtle changes in the poste- rior teeth could have occurred earlier that were not detected.

Each of the amalgam restorations in the first molars exhibited a green tooth discoloration that was con- fined to certain areas; subsequently, decay was noted only in those areas. Since the amalgam restora- tions in the second molars did not

exhibit this discoloration, there are a number of possibilities to con- sider for the difference. The green- ing could have been the result of the use of a different brand or type of amalgam restoration on the dif- ferent molars. The first and second

Figure 6. Postoperative view of the tooth restored with a pos- terior composite.

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GREENING OF T H E TOOTH-AMALGAM INTERFACE DURING E X T E N D E D 1 0 % CARBAMIDE PEROXIDE BLEACHING OF T E T R A C Y C L I N E - S T A I N E D T E E T H : A CASE REPORT

molars would have erupted approx- imately 6 years apart, so the same dentist could have been using a dif- ferent amalgam material. However, the use of a different brand does not explain why the restorations were not uniformly discolored but rather were discolored only where carious tooth structure was present. Other considerations include that the patient could have had a differ- ent dentist, or patient management may have been easier in the later years, resulting in better restora- tions. The extent of the carious process or patient management problems could have influenced the treating dentist to choose to leave some decay in the first molar teeth. The patient was unable to obtain information about the dentist or the dental treatment of the teeth.

Whether the carbamide peroxide bleaching material actually identi- fied the carious tooth structure or leached some component of the amalgam stain that is indicative of underlying carious dentin or leak- age is unclear. It is known that car- bamide peroxide easily passes through enamel and dentin,2°.21 so the entire amalgam was subjected to contact with the material, regardless of the marginal integrity of the restoration. However, certain parts of the amalgam did not demonstrate the green discoloration in the tooth, and in these areas no decay was found. It is also

unknown why some amalgams in the same mouth had the discol- oration, whereas others did not, when both were Subjected to the same treatment protocol. It is note- worthy that when the one facial amalgam was iemoved that had no green staining associated with it, no decay was found.

It is known that 10% carbamide peroxide materials do not all have identical characteristics.22 These differences can be attributable to the base vehicle and other con- stituent parts of their composition. Even the penetration of 10% car- bamide peroxide products through enamel and dentin can differ because of other ingredients in their f ~ r m u l a t i o n . ~ ~ This tooth greening could be specific for both the brand of amalgam and, possibly, the brand of carbamide peroxide. However, this patient was in a larger clinical research project, and none of the other 30 patients, many of whom had amalgam restorations present, had any tooth greening. Nor had the author, who has exten- sive clinical experience using this bleaching technique, encountered this green discoloration in any other patient prior to this time. Subsequent to this report, another patient with older amalgams has exhibited this greening adjacent to old amalgams during an extended treatment time for tetracycline staining. This observation favors

either the presence of caries or the unusual nature of this brand of amalgam and its interaction with tooth structure and caries over an extended period of bleaching. One other consideration might be that the decay occurred during the bleaching. However, carbamide per- oxide has a history of uses to com- bat caries in children with pitted teeth and is used in patients with root caries because of the bacterio- static nature of the material and the removal of plaque by the bleaching

needed to determine if the occur- rence of this green discoloration is always predictable for underlying decay or whether the green discol- oration relates to some element in a particular brand of amalgam or some unusual combination of brand of amalgam and carious tooth structure left in the tooth at the initial restoration.

Further research is

In light of this discoloration obser- vation, dentists should consider the replacement of amalgams on the lingual of anterior teeth prior to extended bleaching, to avoid the potential for the greening of tooth structure causing an esthetic com- promise. Another reason to con- sider replacement is that anterior teeth with lingual amalgams may also exhibit discoloration from the gray of the amalgam as the tooth becomes more translucent.

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H A Y W O O D

CONCLUSION

Caries was found to be present after green discoloration occurred in tooth structure adjacent to amal- gam restorations that had been subjected to extended bleaching times. Whether the green discol- oration was a result of some loss of material from a particular brand of amalgam that is associated with leakage or was indicative of tooth decay is unclear in this single- patient situation. However, dentists should be ready to replace amalgam restorations that cause green discol- oration in adjacent tooth structure following bleaching, because of the possibility of caries.

DISCLOSURE

The author has no financial interest in any of the companies or products mentioned in this article.

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vha~wood@mail~mcg~edu 02002 BC Decker Inc

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