Non Vital Tooth Bleaching – A Successful Case Report

INTRODUCTION

Tooth discolouration can be both intrinsic, extrinsic in origin or combination of both and may occur due to various factors differing in etiology, appearance, localization, severity, and adherence to tooth structure.¹ Intrinsic discoloration is caused by incorporation of chromatogenic material into dentin and enamel during odontogenesis or after eruption. Pre-eruptive discoloration could occur due to exposure to high levels of fluoride, tetracycline administration, inherited developmental disorders, and trauma to the developing tooth. Post-eruptive discoloration is seen due to aging, pulp necrosis and iatrogenic factors.⁶

Discolouration of tooth due to trauma can occur in children as well as adults. It is due to the internal bleeding in the pulp chamber following trauma. Blood components flow into the dentinal tubules, following which surrounding dentin will be discoloured.¹ Trauma to the anterior tooth impairs the esthetics of the patient. Formerly such problems were approached by invasive and expensive conventional restorative procedures such as full crowns. Minimally invasive treatment options have come to the forefront due to the dramatic improvement in the field of esthetic dentistry as well as increased wide spread concerns for dental esthetics.⁵ Newer materials and whitening techniques are introduced everyday due to the increasing popularity of non-invasive dental treatment.²

Non vital tooth bleaching techniques such as walking bleach technique offers a conservative and esthetic solution to the tooth discoloured due to trauma or endodontic treatment in the esthetic zone with minimal loss of coronal tooth structure.⁴ The basic principle of bleaching is splitting of long-chained, dark-colored chromophore molecules into smaller, less coloured, and more diffusible molecules by the action of hydrogen peroxide which acts as a strong oxidizing agent through the formation of free radicals.³

The present article reports the successful bleaching of discolored non-vital, endodontically treated tooth using walking bleach technique.

CASE REPORT

A 19 year old female patient reported to the department of conservative dentistry and Endodontics of SDM College of dental sciences with the complaint of discoloured and unesthetic appearance of upper front teeth. Patient gave a history of trauma 2 years ago. Clinical and radiological examinations were conducted. Intraoral examination revealed discoloured 21 with no fracture and discoloured composite restoration in relation to 21.Vitality test was performed using cold test (endo frost) using adjacent and contralateral teeth as controls. The tooth was diagnosed as non vital which was confirmed by intra oral periapical radiograph which revealed PDL widening. Based on this diagnosis a treatment plan of endodontic therapy and walking bleach technique was decided.

Endodontic therapy was performed with 21. In the next visit after 2 weeks the access cavity was opened and gutta percha filling was removed from the access cavity till 2mm from the cemento enamel junction using peeso reamer. Plug of glass ionomer cement(GC gold label universal restorative powder) was placed on top of the guttapercha filling to prevent percolation of bleaching agent into the cervical and apical region. Amixture of sodium perborate and 6% hydrogen peroxide was placed inside the cavity and condensed with a wet cotton pellet. A piece of dry cotton was placed over this mixture and the access cavity was sealed with modified zinc oxide eugenol cement (IRM, Dentsply). Patient was recalled once in every 7 days, for changing bleaching agent. After 3 visits there was a drastic change in the tooth colour with satisfactory results. The sodium perborate – hydrogen peroxide mixture was removed from the pulp chamber and the access cavity was sealed with composite resin (Filtek Z350 XT, Ivoclar vivadent). The discoloured composite restoration was re restored with composite (Filtek Z350 XT, Ivoclar vivadent). Patient was followed regularly to check the occurrence of external cervical resorption and color stability. Radiographs were taken to serve as a comparison for the subsequent follow up visits. After 1 year follow up esthetic result remained satisfactory with no reversal of discoloration and periapical radiograph showed absence of external cervical resorption in relation to the bleached tooth.

DISCUSSION

Numerous reviews on the bleaching of non vital teeth have been reported in the literature but there are extremely few published case reports on successful non-vital bleaching.

The "walking bleach" technique that was introduced in 1961 involved placement of a mixture of sodium perborate and water into the pulp chamber that was sealed off between the patient's visits to the clinician (Spasser, 1961). The method was later modified and water replaced by 30-35% hydrogen peroxide, to improve the whitening effect (Nutting and Poe, 1963).¹

The other bleaching options involve the thermocatalytic technique and in-office external bleaching technique using high concentrated hydrogen peroxide and carbamide peroxide gel. It is not advisable to use the thermocatalytic method with heating of a 30% H2O2 solution, as this procedure increases the risk of external cervical resorption which is a serious complication.² Inoffice bleaching can often only produce short-term success, based largely on the dehydration of the tooth and by short application time of the bleaching agent.⁵

External cervical resorption is a serious complication that occurs after internal bleaching procedures .Cervical root resorption is an inflammatory-mediated external resorption of the root, which can be seen after trauma and following intracoronal bleaching of non vital teeth.⁶ Cervical root resorption can be prevented by Adhering to the proper barrier placement methods.

Extra radicular diffusion of the bleaching agent can be prevented by the placement of the intra-coronal bleach barrier based on Steiner and West's protocol. The protective barrier was placed 2 mm below the facial CEJ because it resulted in more acceptable aesthetic results, particularly in the cervical region.⁴

Several barrier materials and suppleme ntary barriers have been proposed in the literature. They range from materials like Cavit to Modified Zinc Oxide eugenol (IRM), glass ionomer cement, calcium hydroxide and resin modified glass 10 ionomer cement. Rotstein et al demonstrated that a 2-mm layer of glass-ionomer cement was effective in preventing penetration of 30% hydrogen peroxide solution into the root canal. Thus, the use of this material as a base during bleaching presents the additional advantage that it can be left in place after bleaching and can serve as a base for the final restoration.¹

Numerous studies have been reported in the literature on prognosis of bleached non-vital teeth. According to Howell, walking bleach techniques have an immediate success rate of 89.5%. However, there is a possibility of recurring discoloration, which means that the initial results cannot be considered permanent.⁹ Several authors have evaluated the incidence of color regression one to six years after internal bleaching and reported different percentages of darkening.⁹ While Holmstrup et al¹¹ and Brown¹² both reported a success rate of 75% or more after one to five years.¹¹ In the present case we found more than 90% success rate without change in the colour and with no periapical changes in the tooth.

Some authors have suggested that teeth that have been discolored for several years do not respond as well to bleaching as teeth that are stained for a short period of time.⁹ Some studies have reported that stained teeth in young patients are easier to bleach than discoloration in older patients, presumably because the wide open dentinal tubules in young teeth enable a better diffusion of the bleaching agent.^13,14 Brown et al reported that trauma or necrosis-induced discoloration can be successfully bleached in about 95% of the cases, compared with lower percentages for teeth discolored as a result of medicaments or restorations.¹²

CONCLUSION

When compared to the other post endodontic treatment options like full veneer crowns, non vital bleaching is a conservative treatment option. The possible drawbacks of the full coverage restorations include difficulties in shade matching, achieving the life like appearance and the emergence profile of the natural teeth. In contrast, non vital bleaching is a non invasive procedure. It is also less time consuming, economical and most importantly the patient's natural tooth structure is preserved.