An Innovative, Heat-Accelerated, In-Office Whitening Technique for Nonvital Teeth

Figure 1. Pretreatment view.

A single anterior incisor that has darkened following endodontic treatment can be a difficult problem to resolve. A conventional complete-coverage crown or ceramic veneer may not be deemed the most appropriate approach if there has been only minimal removal of tooth structure to gain proper access for endodontic root canal therapy. Matching a single crown with adjacent natural teeth can be a difficult task. Even if the resulting crown matches well upon seating, darkening of the natural teeth with age may cause the crown to become noticeable in the future.


Many conservative tooth-whitening techniques have been used to attempt to return a darkened tooth to its original appearance. The “walking bleach” technique involves removing the restorative material, sealing the canal opening space from the root canal area apical to the osseous crest, and placing either the agent itself or a cotton pellet soaked with a whitening material in the vacant pulp chamber.1 Agents used include 20­% to 50% hydrogen peroxide, carbamide peroxide, and sodium perborate.

Figure 2. Agent placed in Calset composite warmer.

One or a combination of these materials is placed into the pulp chamber and the access opening sealed. The patient returns, and the process is repeated for as many times as deemed appropriate. The in-office technique involves the placement of high-concentration peroxide on the outer surface of the tooth as well as inside the pulp chamber. Techniques incorporate the use of heat, heat lamps, curing lights, lasers, and special catalysts.2-6 The purpose of the various outside energy stimuli is to accelerate the process. Many of the devices can be quite cumbersome and may be perceived as intrusive by the patient.


Patients often want immediate results and seek rapid treatment. Dentists want to have control over the entire process. Therefore, the in-office techniques are popular with both patients and dentists. 

How can we achieve predictable results in a timely fashion? What if we could provide the increased energy prior to placing the whitening material and without threatening devices? Rather than placing the tooth-whitening solution on the tooth, then providing the activation, why not pre-activate the solution? That is exactly the concept behind a new, commercially available whitening solution using high-concentration hydrogen peroxide that is pre-activated by heat.

 
Figure 3. Facial view of agent placed around protected tissue.
Figure 4. Lingual view of agent placed within pulp chamber.
Figure 5. Additional light activation of agent.

MATERIALS
Niveous (Shofu) is a tooth-whitening gel that contains 27% hydrogen peroxide in a sealed gel capsule. The gel-like material contains proprietary pigments and catalysts that respond to light and to a special applicator tip (Booster Brush) that is impregnated with an activator. This simple unit-dose system is convenient and safe. The capsule is placed in a heater that warms the gel to 130°F, making the gel more reactive and eliminating the need for auxiliary equipment. The heater used in the case report presented in this article is the Calset heater (AdDent Inc), which is designed to heat to 130°F and also can be used to warm composite resin, allowing a better handling material with enhanced polymerization conversion rates.7 The energized tooth whitener reacts with the stain on the teeth, giving improved and quicker results. Chair time and patient discomfort are significantly reduced.

Case Report
A patient presented to the office after undergoing endodontic therapy on tooth No. 8 several years before. The tooth had subsequently darkened and was not aesthetically pleasing to the patient. He had received whitening treatments on several occasions. The results of these “walking bleach” technique treatments can be seen in Figure 1. He inquired about his options and was not interested in a complete coverage crown or a ceramic veneer since the access opening for endodontic root canal therapy was minimal. The patient was aware of several conservative methods of whitening the tooth. Traditional tray-assisted home-bleaching methods would lighten all the teeth, possibly making it even more difficult to match the darkened tooth to the lightened adjacent teeth. It was decided that the whitening procedure should be limited to the right central incisor. A new method of heating the hydrogen peroxide prior to placement on the tooth was presented and readily accepted by the pa­tient.

PROCEDURE
Prior to beginning the tooth- whitening process, radiographs were taken to evaluate the integrity of the root canal filling and bone around the tooth to be treated. The root canal filling must be of a material that can be partially removed without disturbing the apical section. If a silver point had been placed, it must be removed and the tooth re-treated and obturated with a semisolid root canal filling material. The filling material should be removed internally approximately 4 to 5 mm apical to the corresponding location of the free gingival margin on the midfacial aspect of the tooth.


A periodontal probe was used to evaluate the depth of the filling removal. A 3-mm plug of sealing material must be placed to prevent the whitening solution from entering into the apical root canal area. Poorly sealed access, allowing peroxide into the root canal system, has been implicated as a source of internal resorption.8 This plug can be any material that provides a complete seal. Resin-modified glass ionomer restorative material is an excellent choice for this. Any excess material can be easily removed using a diamond instrument in a high-speed handpiece. The proper depth was rechecked using the probe.

The tooth-whitening capsule was placed in the preheated warmer 5 minutes prior to intended usage (Figure 2). A light-curable block-out resin was applied along the buccal gingiva and extended along the interproximal surfaces of the adjacent teeth. This material was carefully placed a little at a time to control the flow of the material and quickly light-cured with a halogen light. Block-out resins readily absorb the longer wavelengths of the light and give off heat during polymerization. The lingual gingival margins should likewise be protected with the resin.

Figure 6. Restored lingual view.

The facial surface of the tooth was scrubbed with pumice and thoroughly washed and dried. The warm capsule of tooth-whitening material was removed from the heater, opened with scissors, and an appropriate amount dispensed into a dappen dish. This was quickly painted onto the buccal surface and the entire inside pulp chamber with the activating brush. The brush was then rubbed across the surface of the tooth until a foaming reaction was observed. This indicates that the peroxide has been activated. The re­maining encapsulated mate­rial was returned to the heating unit. The solution was left on the tooth for 15 minutes (Figures 3 and 4). Additional heat energy was applied by placing a curing light near the surface of the tooth (Figure 5). Assistance must be provided to prevent any of the whitening solution from contacting the tissue during this interval. After the appropriate time, the solution was carefully washed off and the process repeated 2 more times.


The gingival block-out material was removed and the tooth was pumiced again. A dry cotton pellet was placed into the pulp chamber, and the area was sealed with zinc phosphate cement. The patient was reappointed for another treatment or a definitive restoration. 

The patient returned to the office several weeks later and the process was repeated to achieve satisfactory re­sults. The temporary was removed and a bleach-shaded composite material (Beautifil, Shofu) was selected. The internal aspect of the pulp chamber was etched using 37% phosphoric acid, then thoroughly washed and dried. A dentin bonding agent was placed and light- cured. The composite restorative material was carefully added in layers and cured incrementally to reduce the negative effects of polymerization shrinkage stress. The occlusion was carefully check­ed and adjusted, and the lingual surface was polished using mounted polishing points (Figure 6).

The results were outstanding, with the color of the root canal-treated tooth and adjacent tooth indistinguishable (Figure 7). The pa­tient was extremely de­lighted with the appearance (Figure 8).

Figure 7. Post-treatment view. Figure 8. Satisfied patient.

CONCLUSION
Dentists and patients committed to conservative treatment of darkened endodontically treated teeth have desired a quick, easy, predictable method of lightening teeth without the use of elaborate activation systems. This innovative technique can be used in the pursuit of those desires. When carefully followed on select patients, this method can give excellent results.


References

  1. Pearson HH. Bleaching of the discolored pulpless tooth. J Am Dent Assoc. 1958:56;64-68.
  2. Hodosh M, Mirman M, Shklar G, et al. A new method of bleaching discolored teeth by the use of a solid state direct heating device. Dent Dig. 1970:76:344-346.
  3. Tavares M, Stultz J, Newman M, et al. Light augments tooth whitening with peroxide. J Am Dent Assoc. 2003:134:167-175.
  4. Smigel I. Laser tooth whitening. Dent Today. 1996:15:32-36.
  5. Nutting EB, Poe GS. Chemical bleaching of discolored endodontically treated teeth. Dent Clin North Am. November 1967:655-662.
  6. Clinical Research Associates. New generation in-office vital tooth bleaching, part 2. CRA Newsletter. 2003;27(3):1.
  7. Freedman, G. Thermally assisted flow and polymerization of composite resins. Contemp Esthet Restor Pract. 2003:7(2) -46.
  8. Bearham A. The consequences of internal tooth bleaching. Aust Endod J. 1999;25(3):136-139.

Dr. Ward maintains a private practice in Columbus, Ohio, and is a clinical instructor in the Department of Restorative and Prosthetic Dentistry at The Ohio State University College of Dentistry. He is a diplomate of the American Board of Aesthetics, a member of the American Society for Dental Aesthetics, and serves as editor of the ASDA Journal. He has served as examiner of the postgraduate programs in aesthetic dentistry (continuing dental education) at the University of Minnesota, SUNY Buffalo, and the University of Florida. He has lectured internationally and can be reached at (614) 430-8990 or at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .