- Email: [email protected]
VITAL TOOTH BLEACHING: SENSITIVITY AND PULPAL CONSIDERATIONS
VIIAlIOOIH Bl[ACHINli: S[NSIIIVllY
AND PUlPAl CONSIDfRAIIONS
DAN NATHANSON, D.M.D., M.S.D.
'A B
S
T
RAe T
For some patients, sensitivity and discomfort follow vital tooth bleaching. Clinical observations, however, suggest these are re-
ital tooth bleaching as a treatment modality includes various procedures that differ in materials and methods of application. One element common to most procedures is some form of peroxide. In the 1970s, when vital tooth bleaching
versible episodes with no irre-
became an accepted routine treatment in dental offices, the most
versible long-term effects. Using
common procedure involved the use of liquid hydrogen peroxide in
milder peroxide formulations or gels diminishes. postoperative
concentrations between 25 and 35 percent. To make the process
discomfort. The author recom-
more efficient, heat was applied with either a contact instrument or
mends careful treatment when
a specially designed heating lamp.
patients have large restorations, cervical erosion or enamel cracks. Fluoride treatment, sealing restorations and premedication may lessen discomfort.
The combination of high-concentration hydrogen peroxide and heat at 130 to 145 F invariably caused discomfort to patients, both during the procedure and postoperatively. Discomfort was considered an unavoidable side effect. Before treatment, patients would be informed of the risks involved, primarily the onset of pain, ranging from mild sensitivity to severe discomfort. Clinical observations suggested that these were reversible episodes with no irreversible long-term effects.' A clinical study by Cohen and Parkins" monitored vital bleaching procedures in six children with tetracycline-stained teeth. Teeth were treated with hydrogen peroxide and heat applications for 30
JADA, Vol. 128, April 1997
418
-TRfATlNG D1SCOLORfD THTH minutes each session. Heat levels were adjusted to be below the patient's pain threshold. Each child was treated for eight consecutive sessions at oneweek intervals. Pre- and posttreatment pulp vitality tests were performed on treated and control teeth. Throughout the study there were no changes in pulp vitality as a result of the treatment. IDENTIFYING PULPAL CHANGES
In another in vivo study, Cohen" attempted to measure the discomfort incidence related to vital bleaching procedures and to identify pulpal changes that would explain the sensitivity and pain phenomena. Cohen's study involved 19 patients in whom a total of 51 premolars were bleached. He used 35 percent hydrogen peroxide and heat (129 F) in 30-minute sessions. All tested (and control) teeth were slated for orthodontic extractions, which allowed subsequent histologic examination. Of the patients treated, 22 percent experienced no sensitivity at all, but 78 percent had various degrees of sensitivity resulting from bleaching. Sensitivity lasted up to 24 hours in most patients. In one patient, the discomfort lasted 48 hours. Histologic findings from the study showed that all pulps were normal except for moderate vasodilation and aspiration of odontoblast nuclei into the dental tubules. But this occurred with equal frequency in both the experimental and control groups. There were no other histologic findings that could explain the discomfort felt by a majority of the subjects. Cohen concluded that sensitivity and 428
JADA, Vol. 128, April 1997
discomfort during and after vital bleaching procedures are caused by heat application. He theorized that the heat builds up intrapulpal pressure that leads to the sensation of pain. The effect of vital bleaching on the pulp was also the object of an animal study by Seale and colleagues.' Dog canine teeth were bleached with 35 percent hydrogen peroxide with and without the application of heat (144 F). There were also control teeth to which only heat was applied or no treatment was given. Histologic examination
was done at three, 15 and 60 days after the procedures. The application of heat without peroxide caused some vasodilation in the dog tooth pulps, but there were no other changes. The application of 35 percent hydrogen peroxide with heat or alone caused some severe pulpal changes. These included obliteration of odontoblasts, hemorrhage, inflammation and internal resorption of dentin. Dentin resorption appeared as scaling of the dentin walls around the pulp. The 60-day histologic findings showed only a few changes, with otherwise normal pulps, suggesting that in spite of the acute (severe) changes, the
pulps recovered and returned to normal within that time. The severity of pulpal changes observed by Seale and colleagues' is in contrast to Cohen's findings." In addition, most histologic changes observed in the dog study were attributed to the peroxide, but in the human study, both sensitivity and vasodilation were attributed to the application of heat. The two studies agreed that the observed changes were all reversible. One explanation provided by Seale and others for the difference in findings is the difference in morphology of dog teeth compared to human teeth. In dog canine teeth, the combined average thickness of enamel and dentin is 1.7 millimeters. Human premolars have an average thickness of 3.8 mm, presumably providing better pulpal protection from the effect of the peroxide. Another reason for the difference may be in the use of two different species-humans vs. dogs. Seale and Wilson" also tested the effect in dogs of various application times on the removal. of induced tetracycline stains; they monitored pulpal changes through histologic examination. Tetracycline was administered to the dogs in food. Vital bleaching procedures were performed with 35 percent hydrogen peroxide and heat (144 F) applied for four consecutive sessions at two-week intervals. Application times varied from 15 minutes to 30 and 45 minutes. Histologic evaluations were done at 13, 62 and 92 days. Of 18 treated teeth, 17 showed decided pulpal changes ranging from flattening and disruption of the odontoblastic layer to total obliteration of the layer and internal resorption.
TREATING DISCOlORED TEETHThere was a correlation between the bleaching agent application time and the severity of pulpal changes. The 92-day observations for the 15-minute treatment revealed minimal pulpal changes. The 30-minute treatment observed at 92 days showed shortened abnormal odontoblasts, wide zones of tubular and atubular reparative dentin and areas of repaired internal resorption, indicating reversal of the changes. The 45minute bleaching treatment resulted in one nonvital pulp (at 92 days). The other pulp observed for this experimental variable showed chronic inflammatory cells, large amounts of reparative dentin and repaired internal resorption. But in the apical third, the pulp appeared normal. Seale and Wilson" concluded that the combination of 35 percent peroxide and heat produced observable pulpal changes in most dogs, with severity of changes associated with the length of treatment time. Most treated teeth (five of six) showed evidence of reversibility of changes and repair. Discomfort resulting from vital bleaching procedures was one of the parameters monitored in a clinical study reported by Nathanson and Parra." In this study, 15 patients ranging in age from 12 to 24 years were treated with 35 percent hydrogen peroxide and a bleaching lamp as a heat source. Of the 15 subjects, five (30 percent) had no postoperative discomfort. The majority of patients reported a mild sensitivity that did not last beyond 24 hours. Only one patient had postoperative sensitivity that lasted 48 hours. In a comparison of the discomfort levels among young and older
patients, no pattern was found to confirm the commonly believed theory that young patients (with wide pulps) are more susceptible to discomfort from office bleaching procedures involving heat and high concentration hydrogen peroxide. The two 12-year-old subjects in this study were among the patients who had no sensitivity. In contrast to the findings that all pulpal effects of vital bleaching are reversible, Glickman and co-workers? published a case report of a patient who suffered an acute flare-up
of sensitivity in a tooth as a result of vital bleaching. The authors stressed the importance of assessing the teeth before vital bleaching procedures, especially the pulpal and periradicular status. In a review of tooth bleaching, Powell and Bales" concluded that all patients who undergo the procedure should be advised of the possibility of postoperative thermal sensitivity that may last for several days. They recommended prescribing antiinflammatory drugs for premedication when necessary. HOME BLEACHING AGENTS
The advent of home bleaching
involved a procedure with a milder peroxide, usually a 10 to 15 percent carbamide peroxide applied without heat. This technique was assumed to be entirely free of sensitivity and adverse pulpal effects. Reinhardt and others" conducted a threeweek clinical trial to assess the efficiency of home bleaching agents. They reported no tissue inflammation or significant tooth sensitivity. In another clinical study on home bleaching, Sterrett and colleagues" reported that mild transient tooth sensitivity was common to all participants. A more significant response to home bleaching was reported by Schulte and others," who conducted a clinical study involving home bleaching with 10 percent carbamide peroxide. Of the 28 subjects in the study, four discontinued the procedure because of thermal sensitivity. But the remainder of the subjects showed no change in pulpal readings throughout the study. In a survey that Christensen conducted among dentists attending an annual meeting of the American Academy of Esthetic Dentistry, 97 percent of the respondents confirmed that at least some of their patients had temporary sensitivity as a result of home bleaching (G. Christensen, D.D.S., M.S.D., Ph.D., personal communication, August 1996). The reasons for sensitivity and discomfort are not totally clear. Microscopic examinations of enamel after bleaching do not show much alteration of its morphology. Lewinstein and others" examined the effect of 30 percent hydrogen peroxide at various temperatures and found a significant reduction in microJADA, Vol. 128, April 1997
438
-TREATING DISCOLORED TEETH hardness of dentin and enamel that occurred after 15 minutes of application. They concluded that solubility and possibly permeability increased with prolonged bleaching. In a laboratory study, Crim" examined microleakage related to bleaching procedures and concluded that 10 percent carbamide peroxide affected the marginal seal of restorations and increased microleakage around composite restorations bonded with any of the two dentin adhesives tested. This may be one mechanism by which home bleaching agents reach the dentinal tubules. It may also explain why some patients (perhaps those with restorations) experience more sensitivity than others. SUMMARV
Both office and home bleaching procedures have been reported to induce postoperative discomfort in a significant number of patients. The incidence and severity of these seem to have diminished considerably since
448
JADA, VoL 128, April 1997
the use of milder peroxide formulations (that is, home bleaching), or gels for shorter applications. Generally, vital tooth bleaching procedures when done within indications are not a cause of irreversible pulpal changes. Discomfort, if present, will diminish with time. Office procedures can cause more pronounced discomfort than at-home bleaching, but discomfort seldom lasts beyond 24 to 48 hours. Patients who have large or poor restorations, cervical erosions, enamel cracks or similar problems require special consideration. Fluoride treatment of eroded cervical areas, sealing of restorations and premedication may prove helpful in treating these patients and allowing them to partake in the benefits of vital tooth bleaching.• Dr. Nathanson is professor and chairman, Department of Biomaterials, and assistant dean for Continuing Education and External Affairs, Boston University, Goldman School of Dental Medicine, 100 E. Newton St., Boston, Mass. 02118. Address reprint requests to Dr. Nathanson.
1. Goldstein CE, Goldstein RE, Feinman RA, Garber DA. Bleaching vital teeth: state of the art. Chicago: Quintessence Int 1989;20(10):729-37. 2. Cohen S, Parkins FM. Bleaching tetracycline-stained vital teeth. Oral Surg Oral Med Oral Pathol 1970;29(3):465-71. 3. Cohen SC. Human pulpal response to bleaching procedures on vital teeth. J Endod 1979;5(5):134-8. 4. Seale NS, McIntosh JE, Taylor AN. Pulpal reaction to bleaching of teeth in dogs. J Dent Res 1981;60(5):948-53. 5. Seale NS, Wilson CF. Pulpal response to bleaching of teeth in dogs. Pediatr Dent 1985;7(3):209-14. 6. Nathanson D, Parra C. Bleaching vital teeth: a review and clinical study. Compend Contin Educ Dent 1987;8(7):490-7. 7. Glickman GN, Frys H, Baker FL. Adverse response to vital bleaching. J Endod 1992;18(7):351-4. 8. Powell LV, Bales DJ. Tooth bleaching: its effect on oral tissues. JADA 1991;122(12):50-4. 9. Reinhardt JW, Eivins SE, Swift EJ Jr., Denehy GE. A clinical study of nightguard vital bleaching. Quintessence Int 1993;24(6):379-84. 10. Sterrett J, Price RB, Bankey T. Effects of home bleaching on the tissues of the oral cavity. J Can Dent Assoc 1995;61(5):412-20. 11. Schulte JR, Morrissette DB, Gasior EJ, Czajewski MV. The effects of bleaching application time on the dental pulp. JADA 1994;125(10):1330-5. 12. Lewinstein I, Hirschfeld Z, Stabholz A, Rotstein I. Effect of hydrogen peroxide and sodium perborate on the microhardness of human enamel and dentin. J Endod 1994;20(2):61-3. 13. Crim GA. Post-operative bleaching: effect on microleakage. Am J Dent 1992;5(2): 109-12.
AND PUlPAl CONSIDfRAIIONS
DAN NATHANSON, D.M.D., M.S.D.
'A B
S
T
RAe T
For some patients, sensitivity and discomfort follow vital tooth bleaching. Clinical observations, however, suggest these are re-
ital tooth bleaching as a treatment modality includes various procedures that differ in materials and methods of application. One element common to most procedures is some form of peroxide. In the 1970s, when vital tooth bleaching
versible episodes with no irre-
became an accepted routine treatment in dental offices, the most
versible long-term effects. Using
common procedure involved the use of liquid hydrogen peroxide in
milder peroxide formulations or gels diminishes. postoperative
concentrations between 25 and 35 percent. To make the process
discomfort. The author recom-
more efficient, heat was applied with either a contact instrument or
mends careful treatment when
a specially designed heating lamp.
patients have large restorations, cervical erosion or enamel cracks. Fluoride treatment, sealing restorations and premedication may lessen discomfort.
The combination of high-concentration hydrogen peroxide and heat at 130 to 145 F invariably caused discomfort to patients, both during the procedure and postoperatively. Discomfort was considered an unavoidable side effect. Before treatment, patients would be informed of the risks involved, primarily the onset of pain, ranging from mild sensitivity to severe discomfort. Clinical observations suggested that these were reversible episodes with no irreversible long-term effects.' A clinical study by Cohen and Parkins" monitored vital bleaching procedures in six children with tetracycline-stained teeth. Teeth were treated with hydrogen peroxide and heat applications for 30
JADA, Vol. 128, April 1997
418
-TRfATlNG D1SCOLORfD THTH minutes each session. Heat levels were adjusted to be below the patient's pain threshold. Each child was treated for eight consecutive sessions at oneweek intervals. Pre- and posttreatment pulp vitality tests were performed on treated and control teeth. Throughout the study there were no changes in pulp vitality as a result of the treatment. IDENTIFYING PULPAL CHANGES
In another in vivo study, Cohen" attempted to measure the discomfort incidence related to vital bleaching procedures and to identify pulpal changes that would explain the sensitivity and pain phenomena. Cohen's study involved 19 patients in whom a total of 51 premolars were bleached. He used 35 percent hydrogen peroxide and heat (129 F) in 30-minute sessions. All tested (and control) teeth were slated for orthodontic extractions, which allowed subsequent histologic examination. Of the patients treated, 22 percent experienced no sensitivity at all, but 78 percent had various degrees of sensitivity resulting from bleaching. Sensitivity lasted up to 24 hours in most patients. In one patient, the discomfort lasted 48 hours. Histologic findings from the study showed that all pulps were normal except for moderate vasodilation and aspiration of odontoblast nuclei into the dental tubules. But this occurred with equal frequency in both the experimental and control groups. There were no other histologic findings that could explain the discomfort felt by a majority of the subjects. Cohen concluded that sensitivity and 428
JADA, Vol. 128, April 1997
discomfort during and after vital bleaching procedures are caused by heat application. He theorized that the heat builds up intrapulpal pressure that leads to the sensation of pain. The effect of vital bleaching on the pulp was also the object of an animal study by Seale and colleagues.' Dog canine teeth were bleached with 35 percent hydrogen peroxide with and without the application of heat (144 F). There were also control teeth to which only heat was applied or no treatment was given. Histologic examination
was done at three, 15 and 60 days after the procedures. The application of heat without peroxide caused some vasodilation in the dog tooth pulps, but there were no other changes. The application of 35 percent hydrogen peroxide with heat or alone caused some severe pulpal changes. These included obliteration of odontoblasts, hemorrhage, inflammation and internal resorption of dentin. Dentin resorption appeared as scaling of the dentin walls around the pulp. The 60-day histologic findings showed only a few changes, with otherwise normal pulps, suggesting that in spite of the acute (severe) changes, the
pulps recovered and returned to normal within that time. The severity of pulpal changes observed by Seale and colleagues' is in contrast to Cohen's findings." In addition, most histologic changes observed in the dog study were attributed to the peroxide, but in the human study, both sensitivity and vasodilation were attributed to the application of heat. The two studies agreed that the observed changes were all reversible. One explanation provided by Seale and others for the difference in findings is the difference in morphology of dog teeth compared to human teeth. In dog canine teeth, the combined average thickness of enamel and dentin is 1.7 millimeters. Human premolars have an average thickness of 3.8 mm, presumably providing better pulpal protection from the effect of the peroxide. Another reason for the difference may be in the use of two different species-humans vs. dogs. Seale and Wilson" also tested the effect in dogs of various application times on the removal. of induced tetracycline stains; they monitored pulpal changes through histologic examination. Tetracycline was administered to the dogs in food. Vital bleaching procedures were performed with 35 percent hydrogen peroxide and heat (144 F) applied for four consecutive sessions at two-week intervals. Application times varied from 15 minutes to 30 and 45 minutes. Histologic evaluations were done at 13, 62 and 92 days. Of 18 treated teeth, 17 showed decided pulpal changes ranging from flattening and disruption of the odontoblastic layer to total obliteration of the layer and internal resorption.
TREATING DISCOlORED TEETHThere was a correlation between the bleaching agent application time and the severity of pulpal changes. The 92-day observations for the 15-minute treatment revealed minimal pulpal changes. The 30-minute treatment observed at 92 days showed shortened abnormal odontoblasts, wide zones of tubular and atubular reparative dentin and areas of repaired internal resorption, indicating reversal of the changes. The 45minute bleaching treatment resulted in one nonvital pulp (at 92 days). The other pulp observed for this experimental variable showed chronic inflammatory cells, large amounts of reparative dentin and repaired internal resorption. But in the apical third, the pulp appeared normal. Seale and Wilson" concluded that the combination of 35 percent peroxide and heat produced observable pulpal changes in most dogs, with severity of changes associated with the length of treatment time. Most treated teeth (five of six) showed evidence of reversibility of changes and repair. Discomfort resulting from vital bleaching procedures was one of the parameters monitored in a clinical study reported by Nathanson and Parra." In this study, 15 patients ranging in age from 12 to 24 years were treated with 35 percent hydrogen peroxide and a bleaching lamp as a heat source. Of the 15 subjects, five (30 percent) had no postoperative discomfort. The majority of patients reported a mild sensitivity that did not last beyond 24 hours. Only one patient had postoperative sensitivity that lasted 48 hours. In a comparison of the discomfort levels among young and older
patients, no pattern was found to confirm the commonly believed theory that young patients (with wide pulps) are more susceptible to discomfort from office bleaching procedures involving heat and high concentration hydrogen peroxide. The two 12-year-old subjects in this study were among the patients who had no sensitivity. In contrast to the findings that all pulpal effects of vital bleaching are reversible, Glickman and co-workers? published a case report of a patient who suffered an acute flare-up
of sensitivity in a tooth as a result of vital bleaching. The authors stressed the importance of assessing the teeth before vital bleaching procedures, especially the pulpal and periradicular status. In a review of tooth bleaching, Powell and Bales" concluded that all patients who undergo the procedure should be advised of the possibility of postoperative thermal sensitivity that may last for several days. They recommended prescribing antiinflammatory drugs for premedication when necessary. HOME BLEACHING AGENTS
The advent of home bleaching
involved a procedure with a milder peroxide, usually a 10 to 15 percent carbamide peroxide applied without heat. This technique was assumed to be entirely free of sensitivity and adverse pulpal effects. Reinhardt and others" conducted a threeweek clinical trial to assess the efficiency of home bleaching agents. They reported no tissue inflammation or significant tooth sensitivity. In another clinical study on home bleaching, Sterrett and colleagues" reported that mild transient tooth sensitivity was common to all participants. A more significant response to home bleaching was reported by Schulte and others," who conducted a clinical study involving home bleaching with 10 percent carbamide peroxide. Of the 28 subjects in the study, four discontinued the procedure because of thermal sensitivity. But the remainder of the subjects showed no change in pulpal readings throughout the study. In a survey that Christensen conducted among dentists attending an annual meeting of the American Academy of Esthetic Dentistry, 97 percent of the respondents confirmed that at least some of their patients had temporary sensitivity as a result of home bleaching (G. Christensen, D.D.S., M.S.D., Ph.D., personal communication, August 1996). The reasons for sensitivity and discomfort are not totally clear. Microscopic examinations of enamel after bleaching do not show much alteration of its morphology. Lewinstein and others" examined the effect of 30 percent hydrogen peroxide at various temperatures and found a significant reduction in microJADA, Vol. 128, April 1997
438
-TREATING DISCOLORED TEETH hardness of dentin and enamel that occurred after 15 minutes of application. They concluded that solubility and possibly permeability increased with prolonged bleaching. In a laboratory study, Crim" examined microleakage related to bleaching procedures and concluded that 10 percent carbamide peroxide affected the marginal seal of restorations and increased microleakage around composite restorations bonded with any of the two dentin adhesives tested. This may be one mechanism by which home bleaching agents reach the dentinal tubules. It may also explain why some patients (perhaps those with restorations) experience more sensitivity than others. SUMMARV
Both office and home bleaching procedures have been reported to induce postoperative discomfort in a significant number of patients. The incidence and severity of these seem to have diminished considerably since
448
JADA, VoL 128, April 1997
the use of milder peroxide formulations (that is, home bleaching), or gels for shorter applications. Generally, vital tooth bleaching procedures when done within indications are not a cause of irreversible pulpal changes. Discomfort, if present, will diminish with time. Office procedures can cause more pronounced discomfort than at-home bleaching, but discomfort seldom lasts beyond 24 to 48 hours. Patients who have large or poor restorations, cervical erosions, enamel cracks or similar problems require special consideration. Fluoride treatment of eroded cervical areas, sealing of restorations and premedication may prove helpful in treating these patients and allowing them to partake in the benefits of vital tooth bleaching.• Dr. Nathanson is professor and chairman, Department of Biomaterials, and assistant dean for Continuing Education and External Affairs, Boston University, Goldman School of Dental Medicine, 100 E. Newton St., Boston, Mass. 02118. Address reprint requests to Dr. Nathanson.
1. Goldstein CE, Goldstein RE, Feinman RA, Garber DA. Bleaching vital teeth: state of the art. Chicago: Quintessence Int 1989;20(10):729-37. 2. Cohen S, Parkins FM. Bleaching tetracycline-stained vital teeth. Oral Surg Oral Med Oral Pathol 1970;29(3):465-71. 3. Cohen SC. Human pulpal response to bleaching procedures on vital teeth. J Endod 1979;5(5):134-8. 4. Seale NS, McIntosh JE, Taylor AN. Pulpal reaction to bleaching of teeth in dogs. J Dent Res 1981;60(5):948-53. 5. Seale NS, Wilson CF. Pulpal response to bleaching of teeth in dogs. Pediatr Dent 1985;7(3):209-14. 6. Nathanson D, Parra C. Bleaching vital teeth: a review and clinical study. Compend Contin Educ Dent 1987;8(7):490-7. 7. Glickman GN, Frys H, Baker FL. Adverse response to vital bleaching. J Endod 1992;18(7):351-4. 8. Powell LV, Bales DJ. Tooth bleaching: its effect on oral tissues. JADA 1991;122(12):50-4. 9. Reinhardt JW, Eivins SE, Swift EJ Jr., Denehy GE. A clinical study of nightguard vital bleaching. Quintessence Int 1993;24(6):379-84. 10. Sterrett J, Price RB, Bankey T. Effects of home bleaching on the tissues of the oral cavity. J Can Dent Assoc 1995;61(5):412-20. 11. Schulte JR, Morrissette DB, Gasior EJ, Czajewski MV. The effects of bleaching application time on the dental pulp. JADA 1994;125(10):1330-5. 12. Lewinstein I, Hirschfeld Z, Stabholz A, Rotstein I. Effect of hydrogen peroxide and sodium perborate on the microhardness of human enamel and dentin. J Endod 1994;20(2):61-3. 13. Crim GA. Post-operative bleaching: effect on microleakage. Am J Dent 1992;5(2): 109-12.