0099-2399/92/1807-0351/$03.00/0 JOURNAL OF ENDODONTICS Copyright © 1992 by The American Association of Endodontists
Printed in U.S.A. VOL. 18, NO. 7, JULY1992
CASE REPORT Adverse Response to Vital Bleaching Gerald N. Glickman, DDS, MS, Howard Frysh, BDS, DDS, and Frank L. Baker, DDS
maxillary central incisor. The case illustrates the importance of determining the preoperative pulpal states prior to any vital bleaching procedure and suggests that bleaching agents in a vehicle gel can diffuse into the pulp system and cause an alteration of both the pulpal and periradicular status of a tooth.
A case study is presented that described an acute flare-up of a tooth following a vital bleaching procedure. The case illustrates (a) the importance of assessing the pulpal and periradicular status of a tooth prior to any vital bleaching procedure; and (b) the alteration of the local adaptation syndrome by the bleaching agent.
CASE REPORT A 28-yr-old man reported to the Baylor College of Dentistry for evaluation of tooth 9. The patient stated that his tooth had been bleached and that 24 h following the treatment, he experienced intense pain and swelling. Upon further questioning, he stated that a blow had been dealt to the maxillary anterior region during a boating accident 10 yr previously and that the tooth had been slowly discoloring over the past 5 yr. It was determined that a consultation with his dentist could provide valuable information about the bleaching procedure used. The following are details of the evaluation and bleaching procedure as provided by the practitioner. The patient was concerned about his discolored "front tooth" and wanted it bleached. The dentist indicated that the tooth had a slight brownish tinge and that it appeared to be normal radiographically (Fig. 1); no diagnostic tests were performed. After consultation with the patient, a vital bleaching procedure was done using the Starbrite Bleaching System (Stardent Laboratories, Salt Lake City, UT). Prior to placement of the gel mixture, the patient's eyes and clothes were protected and the maxillary anterior teeth were pumiced to ensure sufficient debris and stain removal. Vaseline was used to protect the soft tissues before placement of the rubber dam. The dentist stated that Starbrite bleaching solution (35% H202) was mixed with the gelling agent to a viscosity similar to that of phosphoric acid gel. The bleaching gel was then placed with a cotton tip applicator in a 2-mm thick layer on both the facial and lingual surfaces of tooth 9. After a period of 20 min, the tooth was rinsed with water and air-dried. The dentist as well as the patient stated that the tooth was significantly lighter. He informed the patient that an additional appointment would be necessary to try to achieve the desired esthetic results. Twenty-four hours after the procedure, the patient reported back to the dentist with pain and swelling associated with the tooth. The patient's lip was slightly elevated and the
In-office power bleaching systems along with in-home "nightguard"-type bleaching systems have recently surfaced as the "new wave" of treating discolored vital teeth (1, 2). The inoffice power bleaching systems are administered by the clinician and utilize high concentrations of hydrogen peroxide (30 to 35%), often in conjunction with a bleaching light or other type of heat source, to lighten the teeth. The in-home matrix or carder types use weaker solutions of hydrogen peroxide or 10 to 15 % solutions ofcarbamide peroxide in stents fabricated from 0.020 coping material. These are placed and controlled by the patient according to the individual instructions. Although esthetic satisfaction produced by either method has proven to be dependent on a number of factors including case selection and patient expectations, these methods for bleaching discolored vital teeth have proven to be relatively effective. Recently, in-office bleaching systems using gels have been developed to allow for a more controlled chairside delivery of oxidizing agent (1). These systems simplify the application and do not advocate the use of heat or light that could cause pulpal problems. The viscosity of some of these gels is controlled by the practitioner; the thicker the gel, the lower the concentration of H202 delivered. A slower release of a less concentrated form of hydrogen peroxide, such as 25 %, would not only retard the penetration of hydrogen peroxide but also reduce the possibility of delivering sufficient bleaching agent to the pulp to cause irreversible pulpal damage. Although studies (3, 4) have supported the penetration of bleaching agents through enamel and dentin, there has been little documentation that these power bleaches can cause irreversible pulpal damage as long as the materials are used properly and the pulpal states of the teeth to be bleached are diagnosed as normal. The following report describes a case of an acute flare-up following the use of a gel bleaching system on a discolored
351
352
Glickman et al.
Journal of Endodontics '\
FIG 2. Pedapical radiograph of tooth 9 taken 4 wk after bleaching. There is obvious destruction of the lamina dura in the apical one third and a periradicular radiolucency.
FIG 1. Prebleaching periapical radiograph of tooth 9. The canal system appears to be enlarged and there is discontinuity of the lamina dura in the apical one third.
tooth was extremely painful upon percussion. The dentist prescribed 500 mg of penicillin V (28 tablets) and 800 mg of ibuprofen (12 tablets) and informed the patient to return if the signs and symptoms did not dissipate. At the time of examination at the dental school, the patient was asymptomatic and there was no indication of swelling. However, due to the recent episode of pain and swelling and due to the past history of trauma to the region, a complete evaluation of the pulpal and periradicular status of tooth 9 was made. There was no response to ice and no response to the electric pulp tester (Analytic Technology, Redmond, WA). The tooth was not tender to percussion or palpation. A new periradicular radiograph was taken which clearly indicated destruction of lamina dura in the apical one third with an associated periradicular radiolucency (Fig. 2). A diagnosis of pulpal necrosis with chronic periradicular periodontitis was made. The tooth was planned for nonsurgical root canal therapy. Local anesthetic was administered. Upon access opening no evidence of hemorrhage or vital pulp was found in the canal. The canal was instrumented using a step-back technique. Due to canal weeping and apical resorption, a
Ca(OH)jBaSO4 interim dressing was placed. The tooth was sealed with a dry cotton pellet and an IRM (L. D. Caulk/ Dentsply, Milford, DE) temporary restoration. At the subsequent visit, tooth 9 was reopened without anesthesia and the Ca(OH)2 paste was removed with files. The apical 1V_~mm extent of the Ca(OH)2 paste was left as an apical plug. A #100 master gutta-percha cone was custom fit using chloroform as a softening agent (Fig. 3). Lateral condensation with gutta-percha and Roth's 801 sealer (Roth Int., Chicago, IL) was used to obturate the canal system. An IRM temporary restoration was placed to seal the access (Fig. 4). A 6-month recall radiograph indicated healing of the osseous defect and incomplete absorption of sealer (Fig. 5). The patient was asymptomatic. Although the tooth had maintained its postbleaching color, the patient was advised to return for a final bleach. DISCUSSION Bleaching vital teeth has become an integral part of the practice of cosmetic dentistry. The increasing concern for a "whiter" smile along with the advent of in-home, patientcontrollable procedures has led to the marketing of a number of products which both the practitioner or patient can use with ease in order to achieve an esthetic result. As with any bleaching procedure, however, results cannot be guaranteed and there are still many unknowns to vital bleaching (1, 2).
Vol. 18, No. 7, July 1992
FfG 3. Master gutta-percha cone radiograph. Note apical plug of Ca(OH)2.
These may include longevity of the bleach and the possible need for additional bleaching procedures; the short-term and long-term effects on the pulp, periradicular tissues, restorative materials, and oral soft tissues, especially if multiple trials are necessary; and the exact amount of time and concentration necessary to achieve the desired results since studies demonstrating optimum contact time and concentration have not been done. Tooth hypersensitivity following vital bleaching along with the possibility of cervical root resorption which has been associated with nonvital bleaching are additional concerns with any of the power bleaches or in-home bleaching techniques. The ability of substances to penetrate the enamel and dentin and reach the pulp is relatively well established. In 1951, Bartelstone (5) demonstrated the existence of a pathway from the enamel to pulp. In his study, radioactive iodine penetrated intact enamel, dentin, and pulp of feline teeth with subsequent uptake by the systemic circulation and the thyroid gland. In 1987, with particular concern about the penetrability of bleaching agents during vital bleaching techniques and its potential effects on the pulp, Bowles and Ugwuneri (3) found low concentrations (1 to 10%) of H202 in the pulp chambers of extracted teeth following external application. These amounts significantly increased upon the application of heat (50"C) indicating that permeability increases with increases in temperature. Bowles and Thompson (6) in 1986 also dem-
Adverse Response to Vital Bleaching
353
FiG 4. Postobturation radiograph of tooth 9.
onstrated that a number of pulpal enzymes became very sensitive to combinations of H202 and heat, although the actual quantities of H202 required for inhibition were quite large. More significantly, in a recent study by Cooper et al. (7) in 1991, it was demonstrated that even the 3 to 5% H_,O~ that is released from 10% solutions of carbamide peroxide can reach the pulp. Most reports (8-10) in the literature suggest that there are minimal short-term risks (e.g. hypersensitivity) to pulpal tissues following vital bleaching with 30% H202 and local heat application. However, in order to reduce postoperative complications and other risks case selection is critical. Therefore, it is mandatory that before using any bleaching procedure the following should be ascertained: a complete dental history with particular attention to any previous trauma, a recent preoperative radiograph of diagnostic quality, the clinical condition of the crown including assessment of leaky restorations, and, most important, the pulpal and periradicular status of the teeth. This study is the first reported cases of an acute exacerbation of a chronic lesion following the application of an inoffice power bleach such as Starbrite. Although the gelling agent reduces the effective concentration of H202 from 35% to approximately 25% and there is no heat application, it can be surmised that some concentration of H202 penetrated the chamber and altered the existing pulpal and periradicular state. Based upon the report from the patient's dentist, it was
354
Journal of Endodontics
Glickman et al.
at the time of the power bleach. The penetration of the bleaching agent into the pulpal system without the use of heat suggests that the agent itself was a sufficient noxious stimulant to cause an alteration of the local adaptation syndrome as proposed by Selye ( 1 l). This phenomenon is used by some to explain the increased incidence of flare-ups following root canal therapy on asymptomatic teeth with chronic lesions. Pushing the necrotic debris/microorganisms beyond the root end, for example, can be enough of an irritant to "stir up" a lesion to which the host has adapted (12). Similarly the H202 that entered the quiescent "diseased" pulp in this case may have been enough to upset the delicate balance between host resistance and a disease process. Dr. Glickman is associate professor, Department of Endodontics, Dr. Frysh is assistant professor, Department of General Dentistry, and Dr. Baker is assistant professor, Department of General Dentistry, Baylor College of Dentistry, Dallas, TX. Address requests for reprints to Dr. Gerald Glickman, Department of Endodontics, Baylor College of Dentistry, 3302 Gaston Ave., Dallas, TX 75246.
References
FiG 5. Six-month recall. There appears to be some resolution of the periradicular radiolucency and incomplete absorption of sealer.
concluded that this tooth, due to the past history of trauma, the discoloration, and the "questionable" radiographic appearance of the prebleaching radiograph (Fig. 1), probably had a necrotic pulp with chronic periradicular periodontitis
1. Feinman RA. Reviewing vital bleaching and chemical alterations. J Am Dent Assoc 1991 ;122:55-6. 2. Haywood VB, Heymann HO. Nightguard vital bleaching: how safe is it? Quintessence Int 1991 ;22:515-23. 3. Bowles WH, Ugwuneri Z. Pulp chamber penetration by hydrogen peroxide following vital bleaching procedures. J Endodon 1987;13:375-7. 4. Fuss Z, Szajkis S, Tagger M. Tubular permeability to calcium hydroxide and to bleaching agents. J Endodon 1989;15:362-4. 5. Bartelstone HJ. Radioiodine penetration through intact enamel with uptake by bloodstream and thyroid gland. J Dent Res 1951 ;30:728-33. 6. Bowles WH, Thompson LR. Vital bleaching: the effect of heat and hydrogen peroxide on pulpal enzymes. J Endodon 1986;12:108-12. 7. Cooper JS, Bokmeyer T J, Bowles WH. Penetration of the pulp chamber by carbamide peroxide bleaching agents. J Endodon (in press). 8. Cohen SC. Human pulpal response to bleaching procedures on vital teeth. J Endodon 1979;5:134-8. 9, RobertsonWD, Melfi RC. Pulpal responses to vital bleaching procedures. J Endodon 1980;6:645-9. 10. Seale NS, Wilson CFG. Pulpal response to bleaching of teeth in dogs. Pediatr Dent 1985;7:209-14. 11. Selye H. The part of inflammation in the local adaptation syndrome. In: Jasmin G, Robert A, eds. The mechanism of inflammation. Montreal: Acta, 1953:53-74. 12. Seltzer S, Naidorf IJ. Flare-ups in endodontics: I. Etiological factors. J Endodon 1985;11:472-8.
You Might Like to Know Contraction of rabies by a human is a tragic occurrence and is associated by most people with a bite from a rabid dog. However, in the past 10 years only four people in the U.S.A. have acquired rabies and three of the four were infected by a bat bite (JAMA 265:1365). J. Bowser
Printed in U.S.A. VOL. 18, NO. 7, JULY1992
CASE REPORT Adverse Response to Vital Bleaching Gerald N. Glickman, DDS, MS, Howard Frysh, BDS, DDS, and Frank L. Baker, DDS
maxillary central incisor. The case illustrates the importance of determining the preoperative pulpal states prior to any vital bleaching procedure and suggests that bleaching agents in a vehicle gel can diffuse into the pulp system and cause an alteration of both the pulpal and periradicular status of a tooth.
A case study is presented that described an acute flare-up of a tooth following a vital bleaching procedure. The case illustrates (a) the importance of assessing the pulpal and periradicular status of a tooth prior to any vital bleaching procedure; and (b) the alteration of the local adaptation syndrome by the bleaching agent.
CASE REPORT A 28-yr-old man reported to the Baylor College of Dentistry for evaluation of tooth 9. The patient stated that his tooth had been bleached and that 24 h following the treatment, he experienced intense pain and swelling. Upon further questioning, he stated that a blow had been dealt to the maxillary anterior region during a boating accident 10 yr previously and that the tooth had been slowly discoloring over the past 5 yr. It was determined that a consultation with his dentist could provide valuable information about the bleaching procedure used. The following are details of the evaluation and bleaching procedure as provided by the practitioner. The patient was concerned about his discolored "front tooth" and wanted it bleached. The dentist indicated that the tooth had a slight brownish tinge and that it appeared to be normal radiographically (Fig. 1); no diagnostic tests were performed. After consultation with the patient, a vital bleaching procedure was done using the Starbrite Bleaching System (Stardent Laboratories, Salt Lake City, UT). Prior to placement of the gel mixture, the patient's eyes and clothes were protected and the maxillary anterior teeth were pumiced to ensure sufficient debris and stain removal. Vaseline was used to protect the soft tissues before placement of the rubber dam. The dentist stated that Starbrite bleaching solution (35% H202) was mixed with the gelling agent to a viscosity similar to that of phosphoric acid gel. The bleaching gel was then placed with a cotton tip applicator in a 2-mm thick layer on both the facial and lingual surfaces of tooth 9. After a period of 20 min, the tooth was rinsed with water and air-dried. The dentist as well as the patient stated that the tooth was significantly lighter. He informed the patient that an additional appointment would be necessary to try to achieve the desired esthetic results. Twenty-four hours after the procedure, the patient reported back to the dentist with pain and swelling associated with the tooth. The patient's lip was slightly elevated and the
In-office power bleaching systems along with in-home "nightguard"-type bleaching systems have recently surfaced as the "new wave" of treating discolored vital teeth (1, 2). The inoffice power bleaching systems are administered by the clinician and utilize high concentrations of hydrogen peroxide (30 to 35%), often in conjunction with a bleaching light or other type of heat source, to lighten the teeth. The in-home matrix or carder types use weaker solutions of hydrogen peroxide or 10 to 15 % solutions ofcarbamide peroxide in stents fabricated from 0.020 coping material. These are placed and controlled by the patient according to the individual instructions. Although esthetic satisfaction produced by either method has proven to be dependent on a number of factors including case selection and patient expectations, these methods for bleaching discolored vital teeth have proven to be relatively effective. Recently, in-office bleaching systems using gels have been developed to allow for a more controlled chairside delivery of oxidizing agent (1). These systems simplify the application and do not advocate the use of heat or light that could cause pulpal problems. The viscosity of some of these gels is controlled by the practitioner; the thicker the gel, the lower the concentration of H202 delivered. A slower release of a less concentrated form of hydrogen peroxide, such as 25 %, would not only retard the penetration of hydrogen peroxide but also reduce the possibility of delivering sufficient bleaching agent to the pulp to cause irreversible pulpal damage. Although studies (3, 4) have supported the penetration of bleaching agents through enamel and dentin, there has been little documentation that these power bleaches can cause irreversible pulpal damage as long as the materials are used properly and the pulpal states of the teeth to be bleached are diagnosed as normal. The following report describes a case of an acute flare-up following the use of a gel bleaching system on a discolored
351
352
Glickman et al.
Journal of Endodontics '\
FIG 2. Pedapical radiograph of tooth 9 taken 4 wk after bleaching. There is obvious destruction of the lamina dura in the apical one third and a periradicular radiolucency.
FIG 1. Prebleaching periapical radiograph of tooth 9. The canal system appears to be enlarged and there is discontinuity of the lamina dura in the apical one third.
tooth was extremely painful upon percussion. The dentist prescribed 500 mg of penicillin V (28 tablets) and 800 mg of ibuprofen (12 tablets) and informed the patient to return if the signs and symptoms did not dissipate. At the time of examination at the dental school, the patient was asymptomatic and there was no indication of swelling. However, due to the recent episode of pain and swelling and due to the past history of trauma to the region, a complete evaluation of the pulpal and periradicular status of tooth 9 was made. There was no response to ice and no response to the electric pulp tester (Analytic Technology, Redmond, WA). The tooth was not tender to percussion or palpation. A new periradicular radiograph was taken which clearly indicated destruction of lamina dura in the apical one third with an associated periradicular radiolucency (Fig. 2). A diagnosis of pulpal necrosis with chronic periradicular periodontitis was made. The tooth was planned for nonsurgical root canal therapy. Local anesthetic was administered. Upon access opening no evidence of hemorrhage or vital pulp was found in the canal. The canal was instrumented using a step-back technique. Due to canal weeping and apical resorption, a
Ca(OH)jBaSO4 interim dressing was placed. The tooth was sealed with a dry cotton pellet and an IRM (L. D. Caulk/ Dentsply, Milford, DE) temporary restoration. At the subsequent visit, tooth 9 was reopened without anesthesia and the Ca(OH)2 paste was removed with files. The apical 1V_~mm extent of the Ca(OH)2 paste was left as an apical plug. A #100 master gutta-percha cone was custom fit using chloroform as a softening agent (Fig. 3). Lateral condensation with gutta-percha and Roth's 801 sealer (Roth Int., Chicago, IL) was used to obturate the canal system. An IRM temporary restoration was placed to seal the access (Fig. 4). A 6-month recall radiograph indicated healing of the osseous defect and incomplete absorption of sealer (Fig. 5). The patient was asymptomatic. Although the tooth had maintained its postbleaching color, the patient was advised to return for a final bleach. DISCUSSION Bleaching vital teeth has become an integral part of the practice of cosmetic dentistry. The increasing concern for a "whiter" smile along with the advent of in-home, patientcontrollable procedures has led to the marketing of a number of products which both the practitioner or patient can use with ease in order to achieve an esthetic result. As with any bleaching procedure, however, results cannot be guaranteed and there are still many unknowns to vital bleaching (1, 2).
Vol. 18, No. 7, July 1992
FfG 3. Master gutta-percha cone radiograph. Note apical plug of Ca(OH)2.
These may include longevity of the bleach and the possible need for additional bleaching procedures; the short-term and long-term effects on the pulp, periradicular tissues, restorative materials, and oral soft tissues, especially if multiple trials are necessary; and the exact amount of time and concentration necessary to achieve the desired results since studies demonstrating optimum contact time and concentration have not been done. Tooth hypersensitivity following vital bleaching along with the possibility of cervical root resorption which has been associated with nonvital bleaching are additional concerns with any of the power bleaches or in-home bleaching techniques. The ability of substances to penetrate the enamel and dentin and reach the pulp is relatively well established. In 1951, Bartelstone (5) demonstrated the existence of a pathway from the enamel to pulp. In his study, radioactive iodine penetrated intact enamel, dentin, and pulp of feline teeth with subsequent uptake by the systemic circulation and the thyroid gland. In 1987, with particular concern about the penetrability of bleaching agents during vital bleaching techniques and its potential effects on the pulp, Bowles and Ugwuneri (3) found low concentrations (1 to 10%) of H202 in the pulp chambers of extracted teeth following external application. These amounts significantly increased upon the application of heat (50"C) indicating that permeability increases with increases in temperature. Bowles and Thompson (6) in 1986 also dem-
Adverse Response to Vital Bleaching
353
FiG 4. Postobturation radiograph of tooth 9.
onstrated that a number of pulpal enzymes became very sensitive to combinations of H202 and heat, although the actual quantities of H202 required for inhibition were quite large. More significantly, in a recent study by Cooper et al. (7) in 1991, it was demonstrated that even the 3 to 5% H_,O~ that is released from 10% solutions of carbamide peroxide can reach the pulp. Most reports (8-10) in the literature suggest that there are minimal short-term risks (e.g. hypersensitivity) to pulpal tissues following vital bleaching with 30% H202 and local heat application. However, in order to reduce postoperative complications and other risks case selection is critical. Therefore, it is mandatory that before using any bleaching procedure the following should be ascertained: a complete dental history with particular attention to any previous trauma, a recent preoperative radiograph of diagnostic quality, the clinical condition of the crown including assessment of leaky restorations, and, most important, the pulpal and periradicular status of the teeth. This study is the first reported cases of an acute exacerbation of a chronic lesion following the application of an inoffice power bleach such as Starbrite. Although the gelling agent reduces the effective concentration of H202 from 35% to approximately 25% and there is no heat application, it can be surmised that some concentration of H202 penetrated the chamber and altered the existing pulpal and periradicular state. Based upon the report from the patient's dentist, it was
354
Journal of Endodontics
Glickman et al.
at the time of the power bleach. The penetration of the bleaching agent into the pulpal system without the use of heat suggests that the agent itself was a sufficient noxious stimulant to cause an alteration of the local adaptation syndrome as proposed by Selye ( 1 l). This phenomenon is used by some to explain the increased incidence of flare-ups following root canal therapy on asymptomatic teeth with chronic lesions. Pushing the necrotic debris/microorganisms beyond the root end, for example, can be enough of an irritant to "stir up" a lesion to which the host has adapted (12). Similarly the H202 that entered the quiescent "diseased" pulp in this case may have been enough to upset the delicate balance between host resistance and a disease process. Dr. Glickman is associate professor, Department of Endodontics, Dr. Frysh is assistant professor, Department of General Dentistry, and Dr. Baker is assistant professor, Department of General Dentistry, Baylor College of Dentistry, Dallas, TX. Address requests for reprints to Dr. Gerald Glickman, Department of Endodontics, Baylor College of Dentistry, 3302 Gaston Ave., Dallas, TX 75246.
References
FiG 5. Six-month recall. There appears to be some resolution of the periradicular radiolucency and incomplete absorption of sealer.
concluded that this tooth, due to the past history of trauma, the discoloration, and the "questionable" radiographic appearance of the prebleaching radiograph (Fig. 1), probably had a necrotic pulp with chronic periradicular periodontitis
1. Feinman RA. Reviewing vital bleaching and chemical alterations. J Am Dent Assoc 1991 ;122:55-6. 2. Haywood VB, Heymann HO. Nightguard vital bleaching: how safe is it? Quintessence Int 1991 ;22:515-23. 3. Bowles WH, Ugwuneri Z. Pulp chamber penetration by hydrogen peroxide following vital bleaching procedures. J Endodon 1987;13:375-7. 4. Fuss Z, Szajkis S, Tagger M. Tubular permeability to calcium hydroxide and to bleaching agents. J Endodon 1989;15:362-4. 5. Bartelstone HJ. Radioiodine penetration through intact enamel with uptake by bloodstream and thyroid gland. J Dent Res 1951 ;30:728-33. 6. Bowles WH, Thompson LR. Vital bleaching: the effect of heat and hydrogen peroxide on pulpal enzymes. J Endodon 1986;12:108-12. 7. Cooper JS, Bokmeyer T J, Bowles WH. Penetration of the pulp chamber by carbamide peroxide bleaching agents. J Endodon (in press). 8. Cohen SC. Human pulpal response to bleaching procedures on vital teeth. J Endodon 1979;5:134-8. 9, RobertsonWD, Melfi RC. Pulpal responses to vital bleaching procedures. J Endodon 1980;6:645-9. 10. Seale NS, Wilson CFG. Pulpal response to bleaching of teeth in dogs. Pediatr Dent 1985;7:209-14. 11. Selye H. The part of inflammation in the local adaptation syndrome. In: Jasmin G, Robert A, eds. The mechanism of inflammation. Montreal: Acta, 1953:53-74. 12. Seltzer S, Naidorf IJ. Flare-ups in endodontics: I. Etiological factors. J Endodon 1985;11:472-8.
You Might Like to Know Contraction of rabies by a human is a tragic occurrence and is associated by most people with a bite from a rabid dog. However, in the past 10 years only four people in the U.S.A. have acquired rabies and three of the four were infected by a bat bite (JAMA 265:1365). J. Bowser
