Case Study: Single Tooth
Non-vital Bleaching
Lance Pietropola
January 22, 2004
GP1
Mentors: Dr. Jones
Dr. Strassler
Case Introduction:
Patient X is a 26-year old dental student who presents to the dental school clinic for comprehensive care. Upon completion of initial treatment, patient X mentions that he is displeased with the esthetics of tooth #9 due to the fact that it is markedly darker than the adjacent teeth. The dental history indicates that trauma was sustained to the tooth at approximately the age of twelve. Subsequently, endodontic therapy was performed on the tooth and the patient reports that the tooth has become darker since root canal therapy. Intracoronal bleaching was selected as best treatment of choice for the patient and performed on tooth #9. The purpose of this case study is to evaluate treatment options, discuss intracoronal bleaching as a viable option, and review the method in which nonvital bleaching is performed.
Etiology of Discolored Nonvital Teeth
Teeth having undergone previous endodontic therapy may become discolored due to a number of factors including: remnants of necrotic pulpal tissue, hemorrhaging following trauma, and endodontic filling materials being left in the pulp chamber. Significant dental trauma often results in the rupturing of blood vessels located within the pulp chamber and is referred to as pulpal hemorrhaging. Pulpal hemorrhage in considered to be most frequently linked to the markedly darkening discoloration of endodontically treated teeth. The rupturing of blood vessels releases red blood cells into the pulp chamber, which then undergo hemolysis. Degradation of RBCs releases iron from the RBC-contained hemoglobin into the pulp chamber. The free iron particles then combine with hydrogen sulfide, a product of bacteria present, forming the dark brownish-black compound iron-sulfide causing the tooth to appear darker. It has also been suggested that protein degradation within the tooth, due to necrosis of the pulp, may further enhance the darkening affect on the tooth.
Brief History of Internal Bleaching
The technique of nonvital bleaching was first reported in the middle of the 19th century. Atkinson and Bogue first demonstrated the use of oxalic acid in 1862 in the restoration of natural color to teeth in which the pulp had been removed. Subsequently, a number of reports followed advocating the use of a variety of other compounds and in 1884, A.W. Harlan first suggested the use of hydrogen peroxide for intracoronal bleaching. Adjunctive theapy including the use of heat was suggested by Rosenthal in 1911 and electric light rays by Abbot in 1918 to increase the rate color transformation. Abbot is also credited with first introducing the use of superoxol(concentration of 30% H202) which is still used today. In 1961, Spasser introduced the use of perborate, which was placed into the pulp in between visits. The value of perborate is that it slowly releases hydrogen peroxide when combined with water and can be used to deliver the H202 outside of the dental office over an extended period of time.
Combining all the previous advances in internal bleaching, Nutting and Poe in 1963 coined the term ‘walking bleach’ in their paper describing the technique which is considered to be the widely accepted and employed by dentists today. The walking bleach technique consists of placing a combination of sodium perborate and superoxol into the pulp chamber and placing a temporary restoration sealing off the chamber from the intraoral cavity. The patient can then leave the dental office setting while the mixture within the tooth slowly releases hydrogen peroxide. The bleaching mixture is replaced every 5-7 days to maintain a constant level of hydrogen peroxide present in the tooth. The process is completed when the desired color is reached and a final restoration is then placed to permanently seal off the obturated canal(s). Recently, studies using 10% carbamide peroxide as the bleaching agent have achieved successful results as well.
Cervical Root Resorption
External cervical root resorption is a serious complication following nonvital bleaching of teeth. It is important to mention that any tooth that has undergone trauma, as often is the case with endodontically treated teeth, is at greater risk of undergoing external resorption regardless of whether or not internal bleaching is done. The process of root resorption is mostly asymptomatic and is detected only through follow-up radiographs. Harrington and Natkin(1979) were the first to do extensive research on internal bleaching as it relates to the root resorption phenomenon. In their research, they proposed that the resorption was a result of an inflammatory response within the periodontal space due to the presence of the bleaching agents leaking out of the teeth through the dentin tubules. Their hypothesis was later confirmed by a study done by Anderson and Ronning which showed that dye left within the pulp chamber over time diffuses through the dentinal tubules to the periphery of the tooth. In 1990, Madison and Walton published an extensive study done in animals demonstrating various elements that significantly increase the chances of the bleaching agent causing inflammatory cervical resorption. They determined that the application of heat along with H202 within the pulp chamber resulted most often in cervical resorption and therefore the use of heat is now considered to be detrimental to achieving a successful outcome. According to Rotstein(1991), using a thermocatalytic technique in nonvital bleaching causes the dentin tubules to expand allowing more H202 to diffuse through them and should be avoided. Madison and Walton also noted in their study that an intermediate base should be placed over the obturation material to minimize the amount of H202 permitted to enter the tubules and seal off the remainder of the tooth. In a 2001 study by Kinomoto, superoxyl was replaced with water in the walking bleach technique and the same bleaching effect was achieved with virtually no occurrence of root resorption. The elimination of superoxyl is still a relatively new concept and requires further evaluation.
It is also important to consider the anatomy of teeth in relation to external root resorption. Dentin tubules size and permeability are known to decrease with age. Also, it has been proven that cementum permeability decreases with age, as well as increases in thickness. Therefore, it is reasonable to believe that a nonvital tooth in an older patient undergoing internal bleaching will have a better prognosis due to the inability of the bleach to reach the periodontum. Finally, histological studies have shown that approximately 10% of teeth in normal adults the cementoenamel junction does not meet exposing dentin directly to the periodontal attachment. In cases such as these where dentin is exposed, it imperative that an intermediate barrier be placed to prevent leakage of the bleaching material resulting in resorption.
Summary of Nonvital Bleaching Protocol
1.) A proper dental history of the tooth should be obtained including any previous trauma to the tooth.
2.) The dentist should discuss with the patient all viable treatment options including crowning, veneering, and intracoronal bleaching to obtain a positive esthetic result.
3.) An effective intermediate base (usually glass ionomer) should be placed over the obturation material sealing off the canal prior to bleaching. The base is placed approximately 1-2 mm below the CEJ.
4.) The pulp chamber is etched with 30% phosphoric acid liquid to open the tubules and eliminate the smear layer.
5.) The ‘walking bleach’ consisting of a superoxyl and perborate saturated cotton ball is placed into the pulp chamber and sealed with a temporary filling. The bleaching material is replaced every 5-7 days until the desired color is obtained. A small amount of relapse in color can be expected, and it is recommended to usually go one or two shades lighter than desired shade. Note: Heating the bleaching material should be avoided as it has been linked to causing external resorption.
6.) Once desired shade is achieved, remove all bleaching material, irrigate with sterile water, and place permanent adhesive restoration to seal off canal space.
7.) A follow-up radiograph should be taken at six months to verify that no resorption has occurred.
Case Treatment
Patient X was treated applying these principles in internal bleaching. First, different options were briefly discussed and it was determined that internal bleaching would be the most cost-effective, conservative, and fast. The patient was informed that this is an elective procedure, a relatively small risk of resorption has been associated with such a procedure, and the resulting shade may not be exactly the same as adjacent teeth. Understanding the procedure and the risks involved, patient X elected to undergo in the internal bleaching procedure.
A rubber dam was placed over #9, and the previous composite restoration was removed. Gutta percha was then removed to a depth of 2mm below the CEJ to permit access of the bleach. A layer of glass ionomer was then placed over the gutta percha remaining, sealing off the canal. The chamber was then etched with 30% phosphoric acid liquid and rinsed thoroughly to open up the dentin tubules. A cotton pellet dipped in a mixture of sodium perborate and superoxyl was place in the pulp chamber and sealed off with a cavit temporary restoration. The bleaching solution was left in place for 7 days until the desired shade was achieved. The tooth was actually bleached 2 shades lighter to account for the expected shade relapse. Only one round of bleaching was needed to reach the shade desired. The tooth was then irrigated to remove any residual bleaching material and restored with a hybrid composite. A final radiograph was taken two weeks following the procedure.
As with any procedure, it is necessary to weigh the risks and benefits of intracoronal bleaching. Research has shown that the risk of cervical resorption can be minimized by ensuring a proper intermediate base is placed, the application of heat is avoided, and a mixture of perborate and superoxyl is used. The results of this case and current literature related to nonvital bleaching indicate that this treatment is a sound option for attaining good esthetic results when proper protocol is followed.
Bibliography
1.) Attin T, Paque F, Ajam F, Lennon M. Review of the current status of
tooth whitening with the walking bleach technique. Int Endod J 2003, 36:313-329.
2.) Freccia WF, Peters DD, Lorton L, Bernier WE. An in vitro comparison of nonvital bleaching techniques in the discolored tooth. J Endod 1982;8:70.
3.) Hara TA, Pimenta LA. Nonvital tooth bleaching: A 2-year case report. Quint Int 1999, 30: 748-753.
4.) Harrington G, Natkin E. External resorption associated with bleaching of pulpless teeth. J Endod 1979;5:344.
5.) Ho S, Goerig AC. An in vitro comparison of different bleaching agents in the discolored tooth. J Endod 1979;15:106.
6.) Madison S, Walton R. Cervical root resorption following bleaching of endodontically treated teeth. J Endod. 1990 Dec;16(12):570-4.
7.) Nutting EB, Poe GS. Chemical bleaching of discolored endodontically treated teeth. Dent Clin North Am. 1967 Nov;:655-62.