A conservative approach for internal bleaching of a vital anterior tooth with calcified pulp chamber

Drs. David Keinan and Eugene A. Pantera Jr. solve a common endodontic problem in a conservative way

Abstract 

This article presents a case demonstrating a new and conservative approach for bleaching anterior teeth with yellowish-brown discoloration secondary to pulp chamber calcification. There was also no response to cold stimulation, and the periodontal ligament was radiographically continuous and normal in width.

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The patient preferred to avoid the option of external bleaching or tooth preparation for laminate veneer. The presented technique offers a comparatively conservative approach in the treatment of anterior tooth discoloration associated with pulp chamber obliteration. The esthetic results are consistent with non-vital tooth internal bleaching; yet pre-bleaching root canal treatment is not requested. 

Introduction

Internal bleaching is a well-known commonly used clinical procedure for the treatment of discoloration of endodontically treated anterior teeth (Rotstein, Zalkind, et al., 1991; Amato, Scaravilli, et al., 2006). However, it is not uncommon to have a discolored vital anterior tooth due to pulp chamber calcification (Abbott and Heah, 2009). This pulp chamber calcification is caused by excessive dentin apposition by the odontoblasts that may be accelerated because of trauma to the tooth (Abbott and Heah, 2009). Consequently, there is a decrease in the translucency of the tooth resulting in a yellowing to dark discoloration (Abbott, 1997). 

There are several approaches to deal with this esthetic problem. The common and often most predictable technique involves tooth preparation for a laminate veneer or full porcelain crown (Chen and Raigrodski, 2008; Jun and Wilson, 2008; Sadighpour, Geramipanah, et al., 2009; Freire and Archegas 2010; Alghazzawi, Lemons, et al., 2012; Beier, Kapferer, et al., 2012). However, these options result in irreversible removal of tooth structure and may present barriers in expense and esthetics. 

Using external vital tooth bleaching procedure for color change secondary to a calcified pulp chamber has limited efficacy. External bleaching techniques involve the use of a customized mouth tray with carbamide peroxide gels as the bleaching medium (Fasanaro 1992; Haywood 1992; Haywood 1992; Kielbassa, Attin, et al., 1995; Attin, Paque, et al., 2003). External bleaching of a single tooth is carried out by using 20% carbamide peroxide gel for a period of 4 to 6 weeks or until the single tooth matches all the adjacent teeth. The technique requires modifying the bleaching tray in order to make space for the bleaching agent and limit its action to the discolored tooth. 

The high success rate and simplicity of non-vital tooth bleaching technique requires endodontic treatment prior to initiating internal bleaching (Rotstein, Zalkind, et al., 1991; Amato, Scaravilli, et al., 2006). This approach is also used to reduce tetracycline and other sources of discoloration (Abou-Rass 1982). However, this method for bleaching of a tooth with a calcified pulp chamber has two main disadvantages. First, the endodontic treatment can be a costly procedure as well as being irreversible. Second, since there is calcific metamorphosis, there is a risk for crown or root perforation while trying to find or negotiate the calcified canal space.

The presented case report offers a conservative approach for treating discoloration due to pulp chamber obliteration. This approach may reduce the amount of unnecessary laminate veneers or root canal treatments performed before internal bleaching in refractory cases to external bleaching. 

Case report

A 35-year-old man complained about discoloration of his maxillary left central incisor (Figure 1A).  The patient did not report pain or sensitivity to temperature changes or percussion. Radiographic examination revealed complete calcification of the pulp chamber and the root canal space. The periodontal ligament was continuous with no widening, and the lamina dura appeared normal (Figure 2A). 

At the first visit, the tooth was isolated by using a rubber dam (Hygenic^®, Coltène^®/Whaledent) and an access cavity was designed similar to a normal pulp chamber to the level of the cemental-enamel junction. This step was performed without anesthesia in order to get feedback from the patient for the possibility of neural fibers within a microscopic canal.  A resin modified glass ionomer (RMGI) liner (3M^™ ESPE^™ Vitrebond^™ Light Cure Glass Ionomer Liner/Base, VB) was lined over the calcified canal orifice. A mixture of sodium perborate (SP) was inserted as the common protocol for internal bleaching. A week later, on the second visit, there was major color change, and the bleaching process was repeated again. In the final visit, the color change satisfied the patient (Figure 2B), the SP was flushed out, and a temporary restoration with a zinc oxide-calcium sulfate premixed material (Coltosol^®, Colten, Langenau, Germany) was placed. The patient was referred to his dentist for placement of a permanent restoration. The patient presented after 1 year to a follow-up examination with no symptoms, and the recall radiograph revealed a continuous PDL (Figure 1B). The last follow-up examination, 3 years after treatment, also revealed no symptoms, color satisfaction (Figure 3A), and the same conical root with continuous PDL (Figure 3B).

Discussion

The presented technique recommends a relatively conservative approach in cases with vital tooth discoloration due to pulp chamber obliteration that did not respond to external bleaching. Clinically, as in the presented cases, it is not uncommon to see some color improvement after the first step of making an access cavity. This may be attributed to improving some of the tooth transparency that was reduced by the dentin apposition (Abbott, 1997). We recommend offering the patient trying external bleaching first since it does not involve any tooth preparation. The patient should also be informed about the limited possibility to predict the effect of external bleaching in those cases. 

The presented bleaching option should be carefully selected for asymptomatic cases with pulp chamber calcification. When using the technique previously described, the patient should be informed about the risk of irritating the remaining pulp tissue in the canal, yet it is minimal for several reasons. First, H2O2 is synthesized by the human body itself as a mean of defense (McKenna and Davies, 1988); second, the GIC lining on the access cavity floor prevents H2O2 penetrating the canal. Furthermore, even during external bleaching, a small amount of H2O2 penetrates into the pulp chamber (Bowles and Ugwuneri, 1987). Third, when the favorable prognosis of external vital tooth bleaching is weighed against minimal risk of irritating the pulp, it can be assumed that even if small amount of H2O2 penetrates the GIC barrier, it would have minimal influence; and finally, if there are signs of pulpal disease, then endodontic treatment should be performed as is done with the less conservative non-vital bleaching technique.

Sodium perborate (SP) has been widely used to bleach non-vital teeth with predictable results (Amato, Scaravilli, et al., 2006). The bleaching agent releases active oxygen radicals inside the pulp chamber where it diffuses into the dentinal tubules (Kawamoto and Tsujimoto, 2004). It oxidizes and bleaches the iron sulfide and other pigments present in the dentinal tubules (Attin, Paque, et al., 2003). Free radicals can cause oxidative effects to lipids, proteins, and nucleic acids (Floyd 1997; Park and Floyd, 1997; Kwon, Lee, et al., 1998). Although free radicals are suspected of being mutagenic and carcinogenic (Attin, Paque, et al., 2003), this risk is mitigated with appropriate use of H2O2 during (Rotstein, Zyskind, et al., 1992; Steiner and West, 1994) and after (Li, Sole, et al., 1998) bleaching therapy. Yet, since sensitivity increases with age, high concentrations of H2O2 or extended contact of H2O2 with tissues (Floyd and Carney, 1992; Smith, Carney, et al., 1992; Stadtman, Starke-Reed, et al., 1992; Li, Yan, et al., 1998) should be avoided. Care should be taken to minimize the number of times SP is refreshed as well in order to decrease risk of coronal fracture (Tam, Kuo, et al., 2007; Azevedo, Silva-Sousa, et al., 2011).

The recommended clinical steps for our modified technique include : 

1.Access cavity preparation in the pulp chamber without entering the canal. 

2.Sealing the floor of the access cavity with glass ionomer cement.

3.Applying sodium perborate mixed with saline. 

4.Placing an intermediate restoration for 4-7 days.

This procedure may be repeated several times (2-5), while laminate veneers should be considered for refractory cases. Additionally, this treatment may be followed by external bleaching with carbamide peroxide, especially in cases of persistent discoloration due to external layer stain (West, 1997).

Included in any informed consent regarding bleaching procedures is the need to inform the patient of possibility of requiring endodontic treatment if symptoms of pulpal disease develop.

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