An Effective External Bleaching Technique: Treating Teeth Discolored From Trauma

INTRODUCTION
The occurrence of tooth discoloration in one or more anterior teeth can significantly impair smile aesthetics, prompting patients to seek cosmetic dental treatment. One possible treatment is dental bleaching, which is more conservative and less expensive than prosthetic procedures.

In this context, we turn attention to teeth that have suffered coronal trauma and subsequently a gradual change of color. These teeth can develop a calcific metamorphosis of pulp that, in addition to presenting radiographically as calcification of the pulp chamber, creates a yellow shade. Initially, the yellow shade is subtle, but with time it can become more perceptible and disturbing to the patient. It produces severe coronal discoloration that, through higher dentin thickness and the form of disorganization with which that dysplastic dentin is deposited, transmits through the relatively thin and translucent enamel as a very dark yellowish shade.¹ The clinical and radiographic presence of calcific metamorphosis of pulp indicates a history of previous dental trauma.²

The appearance of these discolored teeth can be improved by dental bleaching using carbamide peroxide with a relatively low concentration (10% to 20%), delivered in a custom-fabricated tray, or via in-office bleaching with a high concentration of hydrogen peroxide (35% to 38%). When correctly administered by a patient or a professional, both are safe, effective, and conservative aesthetic procedures.^2-4

The following clinical case will demonstrate an improvement in color achieved by using supervised at-home dental bleaching (Opalescence 15% [Ultradent Products]) combined with in-office bleaching (Opalescence XTRA Boost PF 38% [Ultradent Products]) of the teeth that suffered coronal trauma resulting in complete pulpal obliteration and teeth discoloration.

CASE REPORT
A 48-year-old patient showed generalized yellow-brown discolorations associated with coronary trauma in the right and left maxillary central incisors (Figure 1). Radiographic examination verified the presence of complete pulpal obliteration without any evidence of periapical pathology and, during this time, the patient did not exhibit any painful symptoms. Prophylactic root canal treatment was not done; therefore, annual clinical and radiographic controls were recommended due to the risk for developing pulpal necrosis (Figure 2).

Initially, bleaching was performed on all teeth in the maxillary and mandibular arches using 15% carbamide peroxide (Opalescence 15%) (Figure 3). This was accomplished by first taking alginate impressions, then fabricating custom bleaching trays for the maxillary and mandibular arches. The patient was instructed to place a small drop of the bleaching product into the spaces in the tray corresponding to his teeth, using the trays 4 hours daily for 3 weeks.

Figure 1. Maxillary right and left central incisor teeth presenting generalized yellow-brown discolorations associated with coronal trauma.	Figure 2. Periapical radiographic of maxillary right and left central incisors demonstrated complete pulpal obliteration without evidence of periapical pathology.
Figure 3. Bleaching was performed on all teeth in the maxillary and mandibular arches using a bleaching agent with 15% carbamide peroxide (Opalescence 15% [Ultradent Products]).	Figure 4. Bleaching of the maxillary right and left incisor teeth with 15% carbamide peroxide (Opalescence 15%).

Figure 5. In-office application of Opalescence Boost PF 38% (Ultradent Products).

After obtaining a satisfactory color in the teeth that did not have coronary trauma (Figure 4), bleaching was performed only on the right and left maxillary central incisor teeth, which had experienced coronal trauma, using 15% carbamide peroxide (Opalescence 15%) for 4 hours daily for 6 weeks. Once a week, these teeth also received an in-office application of dental bleaching with 38% hydrogen peroxide gel (Opalescence Boost PF 38%). The clinical procedures performed for the in-office bleaching began after prophylaxis with a mixture of plain pumice and water, and an application of a rubber dam.

The bleaching gel was applied over the entire vestibular face of the teeth and remained in contact for the manufacturer’s recommended time (Figure 5). Next, the bleaching gel was removed with cotton gauze, and the teeth were then washed and dried. The teeth then received an application of 2% neutral sodium fluoride gel for 4 minutes. Four bleaching sessions were done using the Opalescence Boost PF 38%.
To obtain the ideal color, the traumatized teeth required 9 weeks of bleaching with 15% carbamide peroxide, along with the previously described 4 sessions of in-office bleaching with 38% Opalescence Boost PF (Figure 6).

DISCUSSION
The patient reported that, throughout time, the traumatized teeth showed a gradual increase in discoloration without painful symptoms; this was verified via professional clinical observation as well. In addition, radiographic observations found complete pulpal obliteration without any evidence of periapical pathology. It has been reported^2,4,5 that endodontic treatment is usually not recommended for teeth affected by trauma; furthermore, throughout time, the presence of pulp canal obliteration without symptoms or radiographic signs of periapical pathology may present clinically with or without discoloration. These discolored teeth may receive external vital bleaching that might obtain a satisfactory aesthetic effect; however, traumatized teeth, with or without discoloration, should undergo clinical and radiographic monitoring.^2,4,5

Some changes in dental color might be related to the occurrence of pulpal hemorrhage caused by the coronal trauma. The breakdown of erythrocytes leads to the formation of iron compounds that play a role in the chromatic alteration of dentin to different shades from gray to orange.⁶ Kwon² in 2011 also reported that if the pulp survives a traumatic injury, pulp canal obliteration can occur, characterized by the rapid deposition of hard tissue; beginning within the pulp chamber and continuing along the root canal space, resulting in yellow to brown discoloration of the clinical crown, as observed in this clinical case. Furthermore, we can infer that the volumetric increase of coronal dentin tissue, which accompanies the process of pulp calcification, contributes to changes in the optical characteristics of teeth and the darkening of the coronary throughout time.⁴

Dental bleaching with hydrogen peroxide, combined with a conservative clinical procedure, make it possible to obtain satisfactory aesthetic results for the discolored teeth,7,8 including those that become discolored after coronal trauma.^2,4 However, even with the safe and effective bleaching techniques as presented here, the clinician should consider the importance of a correct indication and also offer proper informed consent to the patient regarding the limitations, benefits, and various choices in bleaching products.^2,4,7,8

External dental bleaching is based on the direct application of hydrogen peroxide to the dental structure, creating the perception of a lighter color through the formation of oxidative free radicals generated by the interaction of hydrogen peroxide with the organic pigment molecules, breaking them into smaller molecules or breaking the double bonds of pigmented molecules, changing their configurations and, consequently, their optical properties.² The aesthetic result obtained with dental bleaching depends on the bleach agent’s concentration, its ability to affect the chromospheres molecules, and the duration and number of times it is in contact with the chromosphere molecules.⁹

Dental bleaching can be performed at home and in the office, offering proven efficacy in both settings, if properly indicated and performed under the guidance and supervision of a trained professional.^2,7,8 The home bleaching agent uses a lower concentration of hydrogen peroxide (10% to 20%) and requires longer periods of daily contact with the tooth structure to be effective. The in-office bleaching agent uses a higher concentration (35% to 38%) and obtains aesthetic results faster with less contact time in contact required between the bleaching product and tooth enamel. In addition, prolonged and direct contact with gingival tissues of these more concentrated bleaching agents is not recommended, a fact that encouraged us to use both bleaching techniques in this clinical case.²

Despite recent research on the cytotoxic potential of highly concentrated peroxide bleach, therapy of this intensity was used only after the analysis of large tissue depositions in the pulp chamber dentin. In this context, Costa et al¹⁰ performed an in vivo study to assess the pulpal condition of premolars and incisors after bleaching with hydrogen peroxide (38% concentration) and found that only the lower incisors had irreversible damage to the pulp. Thus, it is believed that the intensity of the response on the pulp is modulated by the thickness of the hard tissues. It is worth mentioning that, in this clinical case, all the maxillary and mandibular teeth received dental bleaching with 15% carbamide peroxide; this is because the patient wished to the lighten the color of all the teeth, and the color obtained was used as a reference for the teeth with calcified pulp chambers. We believe that the combination of bleaching agents with 15% carbamide peroxide and 38% hydrogen peroxide contributed significantly to the bleaching of the discolored teeth that presented with pulp chamber calcification.

IN SUMMARY
External dental bleaching of traumatically involved teeth, using a combination of carbamide peroxide with a relatively low concentration agent—delivered in a custom-fabricated tray and in-office bleaching with a high concentration of hydrogen peroxide—yielded satisfactory bleaching of the discolored teeth.

References

1. Consolaro A, Bernardini VR. Metamorfose cálcica da polpa e necrose pulpar asséptica no planejamento ortodôntico [in Portuguese]. Rev Dent Press Ortodon Ortop Facial. 2007;12(6):21-23.
2. Kwon SR. Whitening the single discolored tooth. Dent Clin North Am. 2011;55:229-239.
3. Heymann HO. Tooth whitening: facts and fallacies. Br Dent J. 2005;198:514.
4. Sundfeld RH, Briso AL, Mauro SJ. Smile recovery IV: external whitening of traumatized teeth [in Portuguese]. J Bras Clin Estet Odonto. 2000;4(21):29-35.
5. McCabe PS, Dummer PM. Pulp canal obliteration: an endodontic diagnosis and treatment challenge. Int Endod J. 2012;45:177-197.
6. Rihel H. Cord a vaidade. Rev Assoc Bras Odontol. 1998;6:7-11.
7. Haywood VB, Heymann HO. Nightguard vital bleaching. Quintessence Int. 1989;20:173-176.
8. Sundfeld RH, Croll TP, Briso AL, et al. Considerations about enamel microabrasion after 18 years. Am J Dent. 2007;20:67-72.
9. Dahl JE, Pallesen U. Tooth bleaching—a critical review of the biological aspects. Crit Rev Oral Biol Med. 2003;14:292-304.
10. Costa CA, Riehl H, Kina JF, et al. Human pulp responses to in-office tooth bleaching. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2010;109:e59-e64.

Dr. Franco works in the department of restorative dentistry at the Araçatuba Dental School in Araçatuba, Brazil. She can be reached at lauramolinarfranco@hotmail.com.

Dr. Briso is an associate professor in the department of restorative dentistry, Araçatuba Dental School in Araçatuba, Brazil. He can be reached at alfbriso@foa.unesp.br.

Dr. dos Santos is an associate professor in the department of dental materials at the Araçatuba Dental School in Araçatuba, Brazil. He can be reached via e-mail at the address paulosantos@foa.unesp.br.

Dr. Sundfeld is an associate professor in the department of restorative dentistry at the Araçatuba Dental School in Araçatuba, Brazil. He can be reached via e-mail at the address sundfeld@foa.unesp.br.

Dr. Machado works in the department of restorative dentistry at the Araçatuba Dental School in Araçatuba, Brazil. He can be reached at lucassilveira@yahoo.com.br.

Dr. Neto works in the department of restorative dentistry at Piracicaba Dental School in Piracicaba, Brazil. He can be reached via e-mail at daniel_bozy@hotmail.com.

Disclosure: The authors report no disclosures.