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Bleaching of Non-vital Discolored Teeth: Keys of Success


Bleaching of Non-vital Discolored Teeth: Keys of Success

Dental News March 2018 Issue

Dr Mayada Jemâa ( – Assistant Professor, Department of Dental Medicine, Military Principal Hospital of Instruction, Tunis, Tunisia. Dr T. Ben Neji – Resident in Restorative Dentistry and Endodontics, Military Principal Hospital of Instruction, Tunis, Tunisia. Pr N. Zokkar – Professor, Department of Restorative Dentistry and Endodontics, Dental Clinic, Monastir, Tunisia. Dr H. Ouertani – Assistant Professor, Department of Dental Medicine, Military Principal Hospital of Instruction, Tunis, Tunisia. Dr H. Jegham – Assistant Professor, Department of Dental Medicine, Military Principal Hospital of Instruction, Tunis, Tunisia. Pr L. Bhouri – Professor, Department of Restorative Dentistry and Endodontics, Dental Clinic, Monastir, Tunisia. Pr MB. Khattech – Professor, Department of Dental Medicine, Military Principal Hospital of Instruction, Tunis, Tunisia


Teeth discoloration is a fundamental aesthetic problem. It has a social impact on children, adolescents and adults. It is necessary for dentists to identify the etiology of teeth discoloration to establish an accurate and proper diagnosis. There are different options to treat discolored teeth such as restorative procedures, veneers, crowns… Actually, bleaching of non-vital teeth is a routine conservative approach to have a suitable esthetic result for endodontically treated teeth.

Various methods to bleach non-vital teeth have been proposed. Three techniques were described through the literature: the walking bleach technique, the inside/outside bleach technique and the in-office bleaching procedure. The most recommended one is the walking bleach technique since it is simple, safe, with lower risks and suitable for patients and dentists.

Different bleaching agents were used such as sodium perborate, hydrogen peroxide andcarbamide peroxide with various concentrations. Some side effects were reported like external root resorption, diminution of tooth resistance (fracture…), morphological alteration of dental hard tissues and alteration of the characteristics of dental materials.

The objectives of this article:

– To describe the causes of discolored non-vital teeth, – To explain the protocol of the different bleaching procedures and the agents used for, – To report different clinical cases of discolored non-vital teeth treated in our service of Dental Medicine with internal bleaching procedures.

Key words

Non-vital teeth, Discoloration, Bleaching, Carbamide peroxide, Hydrogen peroxide, Sodium perborate, Cervical root resorption.


In our daily dental practice, we observe the increasing demand for esthetics in all fields of dentistry. Esthetic procedures can vary from restorative techniques such as conventional crowns, veneers, or bonding to bleaching treatments. 26 Despite different methods that can improve esthetics; bleaching procedures are safe, minimally invasive, conservative, low cost and effective to treat discolored teeth. 11

Referring to Zarow et al. 2014, even the esthetic treatment plan is based on conservative or prosthodontic procedure; dentist should start with teeth bleaching.

Referring to Rona et al. 2009, the discolored teeth can have an incidence on the self-confidence, self-image, attractiveness and employability of every one. 6

Actually, bleaching of non-vital teeth is considered as a popular procedure because of the continuous need for white teeth and good looks. 1

The internal tooth-bleaching is used to lighten a discolored tooth that was endodontically treated and the procedure consists of the placement of a chemical oxidizing agent within the cavity access chamber to remove discoloration. 25

The first reports concerning bleaching of discolored non-vital teeth were published in the middle of the 19th century. 2, 3

Different chemical agents were used to bleach discolored teeth such as chlorinated lime, oxalic acid, acetic acid, chlorine compounds and solutions, sodium peroxide, sodium hypochlorite, different concentrations of hydrogen peroxide, carbamide peroxide and sodium perborate. 1, 2, 3, 4, 23

The mechanism of action of the different bleaching products is the same. The hydrogen peroxide will decompose into oxygen and water. Then, the oxygen will cause the oxidation and reduction of the organic pigments that are mainly concentrated in the dentin structure. As a result, we obtain the bleaching impact. 7 Referring to literature, we can use light, heat and even electric currents to activate the bleaching agents and to have a rapid result. 2

Clinical examination and radiographic exploration are important before establishing the treatment plan of bleaching. In case of discolored tooth, a periapical radiograph is necessary to evaluate the quality of endodontic filling, the periapex region and a possible alteration of a resorption process. 24 Dentist must define the etiology of the dental discoloration that will have a deep impact on the success of the bleaching treatment. 3

Various procedures are available for non-vital tooth bleaching: In-office bleach technique, Inside/outside bleach technique and Walking bleach technique. Some side effects have been reported in non-vital tooth bleaching including external root resorption, alteration of morphology of dental tissues, modification of the properties of restorative materials and reduction of tooth resistance and adhesion. 7

Different causes of intrinsic discolorations

It is important that clinicians understand the etiology of tooth discoloration to establish the appropriate diagnosis and to define which treatment to apply. 2, 3

Referring to Zimmerli et al. 2010, the intrinsic discoloration is a discoloration that originates from the pulp chamber. Dental trauma or removal of the pulp tissue are the most common causes of intrinsic discoloration. 19

The optical properties and interaction with light of both enamel and dentin help to define the intrinsic color. 2

The modifications of enamel or dentine structures and the induction of different chromatogenic materials into the dental tissues during odontogenesis or in post eruption lead to the intrinsic tooth discoloration. 2, 5

The intrinsic discoloration can be brown, grey, red or yellow. 5 The regular prophylactic techniques cannot remove the intrinsic discoloration and the best treatment is bleaching using various penetrating agents into enamel and dentin to oxidize the chromogens. 8

– Pulp necrosis:

Pulp necrosis can be caused by mechanical, bacterial or chemical irritations. Chromogenic degradation products such as protein degradation products of the pulp tissues can be generated by pulp necrosis leading to tooth discoloration. 1

The degree and the severity of the intrinsic discoloration is proportional to the period that pulp tissues has been necrotic. 2, 3 The treatment of choice for this discoloration is the intracoronal bleaching. 2, 3

– Intrapulpal hemorrhage:

After dental trauma, the intrapulpal bleeding is the most common etiology of tooth discoloration. 1 After rupture of blood vessels, the blood will penetrate the tubules of dentin and its consecutive break down will lead to different chromogenic degradation products like hematoidin, hemine, hemosiderin and hematin. 1, 5 Added to that, pulp extirpation can generate hemorrhage in the pulp chamber. 1, 2, 3, 26

At first, a pink coloration of the crown can be noticed. 2, 3 The iron (Fe) formed by the combination of heme and the putrefying tissue of the pulp will be turned into dark colored iron sulfates by hydrogen sulfates causing a grey staining of the tooth2 Referring to Umar et al. 2014, the modification of tooth color is related to the degree of disintegrated hemoglobin.

– Calcification of the pulp:

In case of calcification of the pulp, there is an obliteration of the dentinal tubules and accumulation of reactionary tertiary dentin.1

Referring to Fearon et al. 2007, we observe a yellow discoloration in case of accumulation of tertiary dentin in the canal and the pulp chamber. This yellow discoloration is not only due to the important volume of additional dentin in the pulp chamber but also due to the translucent enamel.

Generally, the treatment of calcified and discolored tooth is invasive and not conserving the vitality of the pulp (direct or indirect veneers, or ceramic crowns). However, according to Ramos et al. 2013, when respecting the concepts of minimally invasive dentistry and preserving tooth vitality, performing an in- office external bleaching combined with supervised home bleaching is the recommended treatment especially when there is no indication for endodontic treatment.

– Endodontic materials:

The incomplete removal of filling materials, sealer residues and medicaments with tetracycline in endodontically treated tooth can cause coronal discoloration. 2, 3 , 26

Referring to Zimmerli et al. 2010, the combination of some irrigants like sodium hypochlorite and chlorhexidine will cause brownish-red precipitates. That is why a separate rinse between the two different solutions with distilled water or Ringer’s solution is recommended. Despite intracoronal bleaching is the best treatment; the prognosis is related to the type of materials and the contact period. 2, 3

– Incomplete removal of pulp tissue:

The incomplete removal of the pulp tissue especially in the pulp horn area during endodontic treatment can cause discoloration by the persistent residual tissue. 1, 5, 26

The residual tissues will disintegrate progressively, and blood components will infiltrate into the dentinal tubules, causing discoloration. 2, 3 The elimination of the remaining tissue and the intra-coronal bleaching is the recommended treatment. 3

– Coronal restorative materials:

Ancient composite restorations can lead to dark discoloration of margins and even discoloration of dental tissues due to the microleakage formed in resin composite. 2, 3

The amalgam can produce a dark grey coloration of dentin when it is used after endodontic treatment because of the black metallic compounds. 2, 3 The use of metal posts for realizing a core can cause discoloration of the crown because of the metallic ion release and transparent enamel. 2, 3

Bleaching agents of Root-filled Teeth

Referring to Carey et al. 2014, bleaching procedure is determined as the chemical degradation of the chromogens. The most used bleaching agents are hydrogen peroxide, carbamide peroxide and sodium perborate. Other ingredients may be present in the different bleaching products like thickening agents, surfactant, carrier and pigment dispersant, preservative, and flavoring. 8

– Hydrogen peroxide HP (H2O2): 2, 4, 9, 26

Nowadays, it is the active and most commonly used ingredient in whitening products. It is used directly or resulting from a reaction involving sodium perborate or cabamide peroxide. Referring to Bahuguna et al. 2013, the commonly used bleaching chemical agents are oxidizers since they degrade the organic structures of the tooth into shorter lighter in color molecules.

– Carbamide peroxide CP (CH4N2O • H2O2): 1, 2, 9, 19, 25

It is also called urea peroxide. An organic white crystalline compound formed by hydrogen peroxide and urea. Bleaching agents with 10% carbamide peroxide will release 3.5% hydrogen. The stable complex will decompose in contact with water to release hydrogen peroxide. Most of the time, carbamide peroxide is used in a 37% concentration for internal bleaching.

Referring to Douglas et al. 2016, the use of carbamide peroxide for non-vital bleaching is a safe and secure alternative since the diffusion of the hydrogen peroxide to the external root surface is lower and the pH in the external root surface is higher. Added to that, the use of 37% carbamide peroxide generates less structural weakening of the bleached structure compared with sodium perborate.

– Sodium perborate: 1, 2, 25, 26

It is also called perboric acid. Different forms: mono-, tri- (NaBO2 • H2O2 • 3H2O) or tetrahydrate. It is an oxidizing agent presented as a powder.

Sodium perborate will decompose to form sodium metaborate, hydrogen peroxide and nascent oxygen when it is in contact with water, acid or even warm air.

It is often used for internal bleaching since it has excellent results and it respects the periodontal tissues.

Different authors recommend the use of a mixture of sodium perborate and distilled water. However, Kwon et al. 2011 suggested that when we use 30% of hydrogen peroxide mixed with sodium perborate (ratio 2:1 g/mL), we obtain an alkaline pH and the bleaching agent will be more effective.

Importance of the Initial Examination 26, 27

The initial examination is very important in the treatment plan. It includes the evaluation of the color of teeth and the adjacent gingiva.

Added to that, the vitality of teeth must be tested and a radiographic examination is recommended. Dentists must question patients that are presenting a discolored tooth about any history of traumatic injury.

Referring to Van B. Haywood et al. 2010, pulpal problems can happen from 1 to 20 years after dental trauma. Dentists should evaluate the color of the gingival tissues, their thickness and their level. In addition, the color of the root must be taken into consideration.

The discolorations of the gingival tissues may lead to a tooth with a not harmonious color match. Referring to Kwon et al. 2011, the root dentin is different from the dentin in the crown and does not bleach well if at all, nevertheless internal or external bleaching is done. In case that the patient suffers from a gummy smile or hyperactive lip, these problems will be more evident.

The different bleaching techniques

– The walking bleach technique:

In this therapy, clinician applies a bleaching agent into the empty pulp chamber of an endodontically treated and discolored tooth.5

This technique was first described using a mixture of sodium perborate and distilled water. Later, some authors suggested replacing water by 30% hydrogen peroxide to ameliorate the bleaching efficiency. 1, 2

However, referring to Zimmerli et al. 2010, there is no difference in efficiency between the two methods and that using carbamide peroxide in concentrations of 10% or 35% mixed with sodium perborate will improve the bleaching effectiveness.

Treatment steps referring to Kwon et al, 2011:

• Make a radiographic exam to evaluate the presence or not of a root canal filling and to assess the quality of the endodontic filling.

• Isolate the tooth by means of a rubber dam.

• Clean the pulp chamber and the pulp horns of any debris or pulpal remnants to have the entire pulpal cavity visible and cleanable.

• Eliminate the gutta percha with a heated instrument or a low-speed small round bur to 2 mm below the cementoenamel junction CEJ. We can also use Gates-Glidden or Largo burs. This step can be controlled with a periodontal probe.