ORIGINAL CONTRIBUTIONS
PAIN UPDATE
Persistent pain after endodontic therapy Asma A. Khan, BDS, PhD; William Maixner, DDS, PhD; Pei Feng Lim, BDS, MS
CLINICAL PROBLEM
A
middle-aged woman visited a clinician with the chief complaint that her tooth hurt despite having been treated several times by an endodontist to whom she had been referred. Over the previous year, the endodontist had performed nonsurgical endodontic therapy on her maxillary right first molar and six months later performed surgical endodontic therapy (that is, an apicoectomy and a retrograde root canal filling) in an attempt to resolve her pain. However, this treatment was unsuccessful. The patient then sought a second opinion from another dentist, who advised her to have the tooth extracted and an implant placed; however, she chose not to pursue these treatment options. The patient reported that her pain intensity had not changed since she underwent the original endodontic treatment. Analgesics such as ibuprofen and acetaminophen had little or no effect on her pain. The clinical examination did not reveal any dental pathology. A periapical radiograph of the tooth and a cone-beam computed tomographic scan of the quadrant failed to identify any pathological lesion that could have contributed to her pain. What are the most likely explanations for this situation? EXPLANATION
Definition and prevalence. Epidemiologic study findings indicate that odontalgia due to inflammation of the pulp or periapical tissues represents the most prevalent form of orofacial pain, with about 12 to 14 percent of the population reporting a history of odontalgia over a sixmonth period.1-3 In most cases, conventional endodontic therapy resolves odontalgia associated with pulpal pathology, periapical pathology or both. If the pathology fails to resolve, nonsurgical re-treatment or endodontic surgery is indicated. The success rates for conventional and surgical endodontic therapy are reported to be as high as 96 percent and 94 percent, respectively.4-9 A relatively small percentage of patients, however, continue to experience persistent tooth pain after endodontic therapy. This pain usually is nonresponsive to analgesics such as nonsteroidal anti-inflammatory drugs, and it may persist even after the tooth has been extracted.
270
JADA 145(3)
http://jada.ada.org
March 2014
Persistent pain in the area of endodontically treated teeth (defined as pain in the dentoalveolar region that persists for six or more months after completion of treatment) is a poorly understood phenomenon. In a study conducted 12 to 59 months after completion of endodontic treatment, Polycarpou and colleagues10 reported that the prevalence of persistent pain was 12 percent. However, discomfort after endodontic therapy could be due to odontogenic or nonodontogenic etiologies. The former includes teeth with fractures, missed (untreated) root canals and persistent infection. The latter includes neuropathic disorders, neurovascular disorders, headache, referred cardiogenic pain, pain of psychogenic origin and referred myofascial pain, as well as referred pain resulting from pathological conditions outside the immediate dentoalveolar region, such as cervicogenic pain.1,2,11-15 In a meta-analysis of the endodontic literature, Nixdorf and colleagues16 reported a 5.3 percent summary estimate for the frequency of persistent pain after endodontic treatment. These authors also conducted a systematic review and meta-analysis of persistent nonodontogenic pain after endodontic therapy and reported that the frequency of occurrence was 3.4 percent.17 Thus, nonodontogenic pain is not an uncommon outcome after endodontic therapy, and it may represent one-half or more of all cases of persistent tooth pain.17 The diagnostic challenge regarding persistent tooth pain of nonodontogenic origin is complicated by the numerous terms that have been used to describe it. Popular diagnostic terms have included “phantom toothache” and “atypical facial pain,” but both of these terms were replaced by the term “atypical odontalgia” (AO). In 2004, the International Classification of Headache Disorders18 defined AO as “continuous pain in the teeth or in a tooth socket after extraction in the absence of any identifiable dental cause.” In 2011, the term “persistent dentoalveolar pain” (PDAP) disorder was proposed, primarily on the basis of the presence of chronic, continuous pain localized in the dentoalveolar region and not caused by another disorder.19,20 The pain mechanism underlying AO or PDAP is hypothesized to be neuropathic.19,20 Risk factors. Although investigators in a large number of studies have evaluated risk factors associated with pain in the immediate period (that is, ≤ 72 hours) after endodontic therapy, relatively few investigators have evaluated risk factors associated with persistent posttreatment pain (≥ three months).10,21,22 Polycarpou and
ORIGINAL CONTRIBUTIONS
colleagues10 identified some of the risk factors associated with persistent pain after apparently successful endodontic treatment. Some of these include the presence of previous chronic pain conditions (odds ratio [OR], 4.52), persistent (≥ three months) preoperative pain (OR, 8.6), preoperative tenderness to percussion (OR, 7.8) and interappointment odontogenic pain (OR, 3.93).10 These findings are consistent with those of other studies regarding persistent pain after limb amputations, breast surgery, thoracotomy and inguinal hernia repair.23-28 Predisposing factors for persistent postoperative pain in general may include genetic susceptibility, the pain sensitivity profile (neuroplasticity) and psychosocial traits.6-11 In addition, within-patient factors (such as pulpal or periapical pathosis) and external factors (such as trauma) also play an important role. Diagnosis and management. The first step in the diagnosis of persistent pain after endodontic therapy is to determine whether the pain is of odontogenic origin. This is done by using standard clinical and radiographic examinations. Cone-beam computed tomography is a useful aid for identifying periapical lesions, missed root canals and fractures. Nonsurgical re-treatment or endodontic surgery is indicated if the pain is determined to be due to a nonhealing periapical lesion or a missed canal.12-14 If the pain appears to be nonodontogenic in origin, referring the patient to an orofacial pain expert for diagnosis and appropriate treatment is warranted. Nonodontogenic pain can be of neuropathic, neurovascular, sinus, cardiogenic, psychogenic or myofascial origin.26 In addition, clinicians must rule out malignancy and other pathological conditions via additional investigations, as needed. Clinicians often perform a psychological assessment to assess the effect of psychological distress on pain and the influence of chronic pain on daily functions, as well as the patient’s ability to cope with his or her pain. Finally, referrals to other specialists (such as otorhinolaryngologists, neurologists and cardiologists) may be necessary for additional assessments. After a diagnosis has been established, practitioners can target pain management at the underlying pain mechanisms. Chronic neuropathic pain, for example, often is managed pharmacologically with anticonvulsants, antidepressants or both, in conjunction with psychological approaches such as cognitive behavioral therapy.29 Complementary alternative medicine (such as acupuncture) also may play a role in pain management.15,16 Therefore, the care of such patients is best managed in multidisciplinary pain clinics. PREVENTION
On the basis of the results of studies in which investigators evaluated risk factors for persistent postoperative pain,10 it appears that perioperative pain management is of great importance.24,27 Perioperative pain in endodon-
tic patients usually can be well controlled by means of preemptive measures such as occlusion reduction and multimodal analgesia (including administration of longacting local anesthetics and treatment with nonsteroidal anti-inflammatory drugs and other analgesics), along with psychological interventions.28 Because the severity of postoperative pain is predictive of persistent pain, early management of the care of patients who exhibit signs of developing persistent pain likely will be helpful. However, to accomplish this, better methods for assessing postoperative pain need to be established, and investigation of the factors involved in the transition from acute to chronic pain is needed.23,30 In addition, identifying vulnerable patients on the basis of a thorough medical history is important, because people (especially women) with chronic bodily pain (for example, fibromyalgia), a history of painful treatment in the orofacial region or elevated psychological distress (for example, depression and anxiety disorder) are known to be at a higher risk of experiencing poor treatment outcomes.10,23,24 Knowing these facts will aid the clinician in the risk-benefit analysis as he or she considers the need for and extent of the dental procedure in a patient. Finally, discussing the results of the risk assessment with the patient as a component of the informed consent process will establish trust, realistic expectations and a realistic prognosis, and this interaction can help guide the patient in making decisions about whether to proceed with a particular treatment or procedure. CONCLUSION
Persistent tooth pain after endodontic therapy may be due to odontogenic or nonodontogenic etiologies. Odontogenic pain usually resolves after surgical endodontic therapy or nonsurgical re-treatment, whereas nonodontogenic pain is best managed by an orofacial pain expert. ■ doi:10.14219/jada.2013.1 Dr. Khan is an assistant professor, Department of Endodontics and the Regional Center for Neurosensory Disorders, University of North Carolina, 1170 Old Dental Building, CB #7450, Chapel Hill, N.C. 27599, e-mail [email protected]. Address correspondence to Dr. Khan. Dr. Maixner is Kenan Distinguished Professor and the director, Regional Center for Neurosensory Disorders, University of North Carolina at Chapel Hill. Dr. Lim is a clinical associate professor and the director, Oral and Maxillofacial Pain Management Program, University of North Carolina at Chapel Hill. Disclosure. Dr. Maixner is an equity shareholder and officer of Algynomics, Chapel Hill, N.C. Drs. Khan and Lim did not report any disclosures. Pain Update is published in collaboration with the Neuroscience Group of the International Association for Dental Research. 1. Lipton JA, Ship JA, Larach-Robinson D. Estimated prevalence and distribution of reported orofacial pain in the United States. JADA 1993;124(10):115-121. 2. Locker D, Grushka M. The impact of dental and facial pain. J Dent Res 1987;66(9):1414-1417. 3. Riley JL 3rd, Myers CD, Robinson ME, Bulcourf B, Gremillion HA.
JADA 145(3)
http://jada.ada.org
March 2014
271
ORIGINAL CONTRIBUTIONS
Factors predicting orofacial pain patient satisfaction with improvement. J Orofac Pain 2001;15(1):29-35. 4. Ng YL, Mann V, Rahbaran S, Lewsey J, Gulabivala K. Outcome of primary root canal treatment: systematic review of the literature—part 2: influence of clinical factors. Int Endod J 2008;41(1):6-31. 5. Bernstein SD, Horowitz AJ, Man M, et al; Practitioners Engaged in Applied Research and Learning (PEARL) Network Group. Outcomes of endodontic therapy in general practice: a study by the Practitioners Engaged in Applied Research and Learning Network. JADA 2012;143(5): 478-487. 6. Ng YL, Mann V, Rahbaran S, Lewsey J, Gulabivala K. Outcome of primary root canal treatment: systematic review of the literature—part 1: effects of study characteristics on probability of success. Int Endod J 2007;40(12):921-939. 7. Tsesis I, Faivishevsky V, Kfir A, Rosen E. Outcome of surgical endodontic treatment performed by a modern technique: a meta-analysis of literature. J Endod 2009;35(11):1505-1511. 8. Setzer FC, Kohli MR, Shah SB, Karabucak B, Kim S. Outcome of endodontic surgery: a meta-analysis of the literature—part 2: comparison of endodontic microsurgical techniques with and without the use of higher magnification. J Endod 2012;38(1):1-10. 9. Torabinejad M, Corr R, Handysides R, Shabahang S. Outcomes of nonsurgical retreatment and endodontic surgery: a systematic review. J Endod 2009;35(7):930-937. 10. Polycarpou N, Ng YL, Canavan D, Moles DR, Gulabivala K. Prevalence of persistent pain after endodontic treatment and factors affecting its occurrence in cases with complete radiographic healing. Int Endod J 2005;38(3):169-178. 11. Baad-Hansen L. Atypical odontalgia: pathophysiology and clinical management. J Oral Rehabil 2008;35(1):1-11. 12. Mattscheck DJ, Law AS, Noblett WC. Retreatment versus initial root canal treatment: factors affecting posttreatment pain. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2001;92(3):321-324. 13. Alonso AA, Nixdorf DR. Case series of four different headache types presenting as tooth pain. J Endod 2006;32(11):1110-1113. 14. Wright EF. Referred craniofacial pain patterns in patients with temporomandibular disorder (published correction appears in JADA 2000;131[11]:1553). JADA 2000;131(9):1307-1315. 15. Israel HA, Ward JD, Horrell B, Scrivani SJ. Oral and maxillofacial surgery in patients with chronic orofacial pain. J Oral Maxillofac Surg
272
JADA 145(3)
http://jada.ada.org
March 2014
2003;61(6):662-667. 16. Nixdorf DR, Moana-Filho EJ, Law AS, McGuire LA, Hodges JS, John MT. Frequency of persistent tooth pain after root canal therapy: a systematic review and meta-analysis. J Endod 2010;36(2):224-230. 17. Nixdorf DR, Moana-Filho EJ, Law AS, McGuire LA, Hodges JS, John MT. Frequency of nonodontogenic pain after endodontic therapy: a systematic review and meta-analysis. J Endod 2010;36(9):1494-1498. 18. Headache Classification Subcommittee of the International Headache Society. The International Classification of Headache Disorders. 2nd ed. Cephalalgia 2004;24(suppl 1):1-150. 19. Nixdorf D, Moana-Filho E. Persistent dento-alveolar pain disorder (PDAP): working towards a better understanding. Review Pain 2011;5(4):18-25. 20. Nixdorf DR, Drangsholt MT, Ettlin DA, et al. Classifying orofacial pains: a new proposal of taxonomy based on ontology. J Oral Rehabil 2012;39(3):161-169. 21. Campbell RL, Parks KW, Dodds RN. Chronic facial pain associated with endodontic therapy. Oral Surg Oral Med Oral Pathol 1990;69(3): 287-290. 22. Fouad AF, Burleson J. The effect of diabetes mellitus on endodontic treatment outcome: data from an electronic patient record. JADA 2003;134(1):43-51. 23. Lavand’homme P. The progression from acute to chronic pain. Curr Opin Anaesthesiol 2011;24(5):545-550. 24. Katz J, Seltzer Z. Transition from acute to chronic postsurgical pain: risk factors and protective factors. Expert Rev Neurother 2009;9(5): 723-744. 25. Niraj G, Rowbotham DJ. Persistent postoperative pain: where are we now? Br J Anaesth 2011;107(1):25-29. 26. Okeson JP, Falace DA. Nonodontogenic toothache. Dent Clin North Am 1997;41(1):367-383. 27. Sinatra R. Causes and consequences of inadequate management of acute pain. Pain Med 2010;11(12):1859-1871. 28. Jerjes W, Hopper C, Kumar M, et al. Psychological intervention in acute dental pain: review. Br Dent J 2007;202(6):337-343. 29. Baad-Hansen L. Atypical odontalgia: pathophysiology and clinical management. J Oral Rehabil 2008;35(1):1-11. 30. Kehlet H, Dahl JB. Assessment of postoperative pain: need for action! Pain 2011;152(8):1699-1700.
PAIN UPDATE
Persistent pain after endodontic therapy Asma A. Khan, BDS, PhD; William Maixner, DDS, PhD; Pei Feng Lim, BDS, MS
CLINICAL PROBLEM
A
middle-aged woman visited a clinician with the chief complaint that her tooth hurt despite having been treated several times by an endodontist to whom she had been referred. Over the previous year, the endodontist had performed nonsurgical endodontic therapy on her maxillary right first molar and six months later performed surgical endodontic therapy (that is, an apicoectomy and a retrograde root canal filling) in an attempt to resolve her pain. However, this treatment was unsuccessful. The patient then sought a second opinion from another dentist, who advised her to have the tooth extracted and an implant placed; however, she chose not to pursue these treatment options. The patient reported that her pain intensity had not changed since she underwent the original endodontic treatment. Analgesics such as ibuprofen and acetaminophen had little or no effect on her pain. The clinical examination did not reveal any dental pathology. A periapical radiograph of the tooth and a cone-beam computed tomographic scan of the quadrant failed to identify any pathological lesion that could have contributed to her pain. What are the most likely explanations for this situation? EXPLANATION
Definition and prevalence. Epidemiologic study findings indicate that odontalgia due to inflammation of the pulp or periapical tissues represents the most prevalent form of orofacial pain, with about 12 to 14 percent of the population reporting a history of odontalgia over a sixmonth period.1-3 In most cases, conventional endodontic therapy resolves odontalgia associated with pulpal pathology, periapical pathology or both. If the pathology fails to resolve, nonsurgical re-treatment or endodontic surgery is indicated. The success rates for conventional and surgical endodontic therapy are reported to be as high as 96 percent and 94 percent, respectively.4-9 A relatively small percentage of patients, however, continue to experience persistent tooth pain after endodontic therapy. This pain usually is nonresponsive to analgesics such as nonsteroidal anti-inflammatory drugs, and it may persist even after the tooth has been extracted.
270
JADA 145(3)
http://jada.ada.org
March 2014
Persistent pain in the area of endodontically treated teeth (defined as pain in the dentoalveolar region that persists for six or more months after completion of treatment) is a poorly understood phenomenon. In a study conducted 12 to 59 months after completion of endodontic treatment, Polycarpou and colleagues10 reported that the prevalence of persistent pain was 12 percent. However, discomfort after endodontic therapy could be due to odontogenic or nonodontogenic etiologies. The former includes teeth with fractures, missed (untreated) root canals and persistent infection. The latter includes neuropathic disorders, neurovascular disorders, headache, referred cardiogenic pain, pain of psychogenic origin and referred myofascial pain, as well as referred pain resulting from pathological conditions outside the immediate dentoalveolar region, such as cervicogenic pain.1,2,11-15 In a meta-analysis of the endodontic literature, Nixdorf and colleagues16 reported a 5.3 percent summary estimate for the frequency of persistent pain after endodontic treatment. These authors also conducted a systematic review and meta-analysis of persistent nonodontogenic pain after endodontic therapy and reported that the frequency of occurrence was 3.4 percent.17 Thus, nonodontogenic pain is not an uncommon outcome after endodontic therapy, and it may represent one-half or more of all cases of persistent tooth pain.17 The diagnostic challenge regarding persistent tooth pain of nonodontogenic origin is complicated by the numerous terms that have been used to describe it. Popular diagnostic terms have included “phantom toothache” and “atypical facial pain,” but both of these terms were replaced by the term “atypical odontalgia” (AO). In 2004, the International Classification of Headache Disorders18 defined AO as “continuous pain in the teeth or in a tooth socket after extraction in the absence of any identifiable dental cause.” In 2011, the term “persistent dentoalveolar pain” (PDAP) disorder was proposed, primarily on the basis of the presence of chronic, continuous pain localized in the dentoalveolar region and not caused by another disorder.19,20 The pain mechanism underlying AO or PDAP is hypothesized to be neuropathic.19,20 Risk factors. Although investigators in a large number of studies have evaluated risk factors associated with pain in the immediate period (that is, ≤ 72 hours) after endodontic therapy, relatively few investigators have evaluated risk factors associated with persistent posttreatment pain (≥ three months).10,21,22 Polycarpou and
ORIGINAL CONTRIBUTIONS
colleagues10 identified some of the risk factors associated with persistent pain after apparently successful endodontic treatment. Some of these include the presence of previous chronic pain conditions (odds ratio [OR], 4.52), persistent (≥ three months) preoperative pain (OR, 8.6), preoperative tenderness to percussion (OR, 7.8) and interappointment odontogenic pain (OR, 3.93).10 These findings are consistent with those of other studies regarding persistent pain after limb amputations, breast surgery, thoracotomy and inguinal hernia repair.23-28 Predisposing factors for persistent postoperative pain in general may include genetic susceptibility, the pain sensitivity profile (neuroplasticity) and psychosocial traits.6-11 In addition, within-patient factors (such as pulpal or periapical pathosis) and external factors (such as trauma) also play an important role. Diagnosis and management. The first step in the diagnosis of persistent pain after endodontic therapy is to determine whether the pain is of odontogenic origin. This is done by using standard clinical and radiographic examinations. Cone-beam computed tomography is a useful aid for identifying periapical lesions, missed root canals and fractures. Nonsurgical re-treatment or endodontic surgery is indicated if the pain is determined to be due to a nonhealing periapical lesion or a missed canal.12-14 If the pain appears to be nonodontogenic in origin, referring the patient to an orofacial pain expert for diagnosis and appropriate treatment is warranted. Nonodontogenic pain can be of neuropathic, neurovascular, sinus, cardiogenic, psychogenic or myofascial origin.26 In addition, clinicians must rule out malignancy and other pathological conditions via additional investigations, as needed. Clinicians often perform a psychological assessment to assess the effect of psychological distress on pain and the influence of chronic pain on daily functions, as well as the patient’s ability to cope with his or her pain. Finally, referrals to other specialists (such as otorhinolaryngologists, neurologists and cardiologists) may be necessary for additional assessments. After a diagnosis has been established, practitioners can target pain management at the underlying pain mechanisms. Chronic neuropathic pain, for example, often is managed pharmacologically with anticonvulsants, antidepressants or both, in conjunction with psychological approaches such as cognitive behavioral therapy.29 Complementary alternative medicine (such as acupuncture) also may play a role in pain management.15,16 Therefore, the care of such patients is best managed in multidisciplinary pain clinics. PREVENTION
On the basis of the results of studies in which investigators evaluated risk factors for persistent postoperative pain,10 it appears that perioperative pain management is of great importance.24,27 Perioperative pain in endodon-
tic patients usually can be well controlled by means of preemptive measures such as occlusion reduction and multimodal analgesia (including administration of longacting local anesthetics and treatment with nonsteroidal anti-inflammatory drugs and other analgesics), along with psychological interventions.28 Because the severity of postoperative pain is predictive of persistent pain, early management of the care of patients who exhibit signs of developing persistent pain likely will be helpful. However, to accomplish this, better methods for assessing postoperative pain need to be established, and investigation of the factors involved in the transition from acute to chronic pain is needed.23,30 In addition, identifying vulnerable patients on the basis of a thorough medical history is important, because people (especially women) with chronic bodily pain (for example, fibromyalgia), a history of painful treatment in the orofacial region or elevated psychological distress (for example, depression and anxiety disorder) are known to be at a higher risk of experiencing poor treatment outcomes.10,23,24 Knowing these facts will aid the clinician in the risk-benefit analysis as he or she considers the need for and extent of the dental procedure in a patient. Finally, discussing the results of the risk assessment with the patient as a component of the informed consent process will establish trust, realistic expectations and a realistic prognosis, and this interaction can help guide the patient in making decisions about whether to proceed with a particular treatment or procedure. CONCLUSION
Persistent tooth pain after endodontic therapy may be due to odontogenic or nonodontogenic etiologies. Odontogenic pain usually resolves after surgical endodontic therapy or nonsurgical re-treatment, whereas nonodontogenic pain is best managed by an orofacial pain expert. ■ doi:10.14219/jada.2013.1 Dr. Khan is an assistant professor, Department of Endodontics and the Regional Center for Neurosensory Disorders, University of North Carolina, 1170 Old Dental Building, CB #7450, Chapel Hill, N.C. 27599, e-mail [email protected]. Address correspondence to Dr. Khan. Dr. Maixner is Kenan Distinguished Professor and the director, Regional Center for Neurosensory Disorders, University of North Carolina at Chapel Hill. Dr. Lim is a clinical associate professor and the director, Oral and Maxillofacial Pain Management Program, University of North Carolina at Chapel Hill. Disclosure. Dr. Maixner is an equity shareholder and officer of Algynomics, Chapel Hill, N.C. Drs. Khan and Lim did not report any disclosures. Pain Update is published in collaboration with the Neuroscience Group of the International Association for Dental Research. 1. Lipton JA, Ship JA, Larach-Robinson D. Estimated prevalence and distribution of reported orofacial pain in the United States. JADA 1993;124(10):115-121. 2. Locker D, Grushka M. The impact of dental and facial pain. J Dent Res 1987;66(9):1414-1417. 3. Riley JL 3rd, Myers CD, Robinson ME, Bulcourf B, Gremillion HA.
JADA 145(3)
http://jada.ada.org
March 2014
271
ORIGINAL CONTRIBUTIONS
Factors predicting orofacial pain patient satisfaction with improvement. J Orofac Pain 2001;15(1):29-35. 4. Ng YL, Mann V, Rahbaran S, Lewsey J, Gulabivala K. Outcome of primary root canal treatment: systematic review of the literature—part 2: influence of clinical factors. Int Endod J 2008;41(1):6-31. 5. Bernstein SD, Horowitz AJ, Man M, et al; Practitioners Engaged in Applied Research and Learning (PEARL) Network Group. Outcomes of endodontic therapy in general practice: a study by the Practitioners Engaged in Applied Research and Learning Network. JADA 2012;143(5): 478-487. 6. Ng YL, Mann V, Rahbaran S, Lewsey J, Gulabivala K. Outcome of primary root canal treatment: systematic review of the literature—part 1: effects of study characteristics on probability of success. Int Endod J 2007;40(12):921-939. 7. Tsesis I, Faivishevsky V, Kfir A, Rosen E. Outcome of surgical endodontic treatment performed by a modern technique: a meta-analysis of literature. J Endod 2009;35(11):1505-1511. 8. Setzer FC, Kohli MR, Shah SB, Karabucak B, Kim S. Outcome of endodontic surgery: a meta-analysis of the literature—part 2: comparison of endodontic microsurgical techniques with and without the use of higher magnification. J Endod 2012;38(1):1-10. 9. Torabinejad M, Corr R, Handysides R, Shabahang S. Outcomes of nonsurgical retreatment and endodontic surgery: a systematic review. J Endod 2009;35(7):930-937. 10. Polycarpou N, Ng YL, Canavan D, Moles DR, Gulabivala K. Prevalence of persistent pain after endodontic treatment and factors affecting its occurrence in cases with complete radiographic healing. Int Endod J 2005;38(3):169-178. 11. Baad-Hansen L. Atypical odontalgia: pathophysiology and clinical management. J Oral Rehabil 2008;35(1):1-11. 12. Mattscheck DJ, Law AS, Noblett WC. Retreatment versus initial root canal treatment: factors affecting posttreatment pain. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2001;92(3):321-324. 13. Alonso AA, Nixdorf DR. Case series of four different headache types presenting as tooth pain. J Endod 2006;32(11):1110-1113. 14. Wright EF. Referred craniofacial pain patterns in patients with temporomandibular disorder (published correction appears in JADA 2000;131[11]:1553). JADA 2000;131(9):1307-1315. 15. Israel HA, Ward JD, Horrell B, Scrivani SJ. Oral and maxillofacial surgery in patients with chronic orofacial pain. J Oral Maxillofac Surg
272
JADA 145(3)
http://jada.ada.org
March 2014
2003;61(6):662-667. 16. Nixdorf DR, Moana-Filho EJ, Law AS, McGuire LA, Hodges JS, John MT. Frequency of persistent tooth pain after root canal therapy: a systematic review and meta-analysis. J Endod 2010;36(2):224-230. 17. Nixdorf DR, Moana-Filho EJ, Law AS, McGuire LA, Hodges JS, John MT. Frequency of nonodontogenic pain after endodontic therapy: a systematic review and meta-analysis. J Endod 2010;36(9):1494-1498. 18. Headache Classification Subcommittee of the International Headache Society. The International Classification of Headache Disorders. 2nd ed. Cephalalgia 2004;24(suppl 1):1-150. 19. Nixdorf D, Moana-Filho E. Persistent dento-alveolar pain disorder (PDAP): working towards a better understanding. Review Pain 2011;5(4):18-25. 20. Nixdorf DR, Drangsholt MT, Ettlin DA, et al. Classifying orofacial pains: a new proposal of taxonomy based on ontology. J Oral Rehabil 2012;39(3):161-169. 21. Campbell RL, Parks KW, Dodds RN. Chronic facial pain associated with endodontic therapy. Oral Surg Oral Med Oral Pathol 1990;69(3): 287-290. 22. Fouad AF, Burleson J. The effect of diabetes mellitus on endodontic treatment outcome: data from an electronic patient record. JADA 2003;134(1):43-51. 23. Lavand’homme P. The progression from acute to chronic pain. Curr Opin Anaesthesiol 2011;24(5):545-550. 24. Katz J, Seltzer Z. Transition from acute to chronic postsurgical pain: risk factors and protective factors. Expert Rev Neurother 2009;9(5): 723-744. 25. Niraj G, Rowbotham DJ. Persistent postoperative pain: where are we now? Br J Anaesth 2011;107(1):25-29. 26. Okeson JP, Falace DA. Nonodontogenic toothache. Dent Clin North Am 1997;41(1):367-383. 27. Sinatra R. Causes and consequences of inadequate management of acute pain. Pain Med 2010;11(12):1859-1871. 28. Jerjes W, Hopper C, Kumar M, et al. Psychological intervention in acute dental pain: review. Br Dent J 2007;202(6):337-343. 29. Baad-Hansen L. Atypical odontalgia: pathophysiology and clinical management. J Oral Rehabil 2008;35(1):1-11. 30. Kehlet H, Dahl JB. Assessment of postoperative pain: need for action! Pain 2011;152(8):1699-1700.
