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Endodontic flare-ups and associated factors in a Taiwanese hospital YI-FEN CHEN YU-HEN LIN CHENG-CHANG CHEN HUI-LING CHEN Department of Dentistry, Chang Gung Memorial Hospital, Linkou, Taipei County, Taiwan, ROC. A flare-up following root canal treatment (RCT) is a frustrating problem to both patients and dentists. The purpose of this study was to evaluate the incidence of endodontic flare-ups of Taiwanese patients at Chang Gung Memorial Hospital (CGMH), Linkou, Taiwan in a prospective survey. An unscheduled phone call and/or an emergency visit due to severe pain and/or swelling following RCT was defined as a flare-up. Six hundred and fifty-eight teeth were treated in the Endodontic Department of CGMH by senior residents or attending doctors in a period of 3 months. Patient’s demographics, and clinical and radiographic data were recorded at the time of the RCT. We found that the overall incidence of flare-ups was relatively small (1.98%). The incidence of flare-ups was significantly correlated with presenting symptoms of spontaneous pain (5.48%, p=0.025), percussion pain (12%, p=0.000), and root canal overfilling (7.89%, p=0.034). However, there was no correlation between the incidence of flare-ups and patient age, gender, tooth position, periapical diagnosis, pulpal diagnosis, type of treatment, or type of operator. We concluded that the occurrence of flare-ups is significantly related to preoperative spontaneous pain, percussion pain, and root canal overfilling. (J Dent Sci, 2(1):39-44 , 2007) Key words: flare-ups, root canal treatment, overfilling, preoperative pain. Severe pain and/or swelling following root canal treatment (RCT) are serious sequelae. This is upsetting to both the patient and dentist. The flare-up phenomenon is complex, and the reasons for such exacerbations are not always clear. Undoubtedly it involves a number of aspects related to local tissue adaptation, changes in periapical tissue pressure, a microbial imbalance, immunological phenomena, and various psychological factors1. A flare-up is a true complication characterized by the development of pain or swelling both during and after endodontic therapy, and is of sufficient severity to require an unscheduled visit for emergency treatment. Different incidences of flare-up after RCT have been reported. These variations are the result of examining different factors and conditions related to flare-ups. For example, Morse et al.2 reported an incidence of flare-up of 20% (using swelling as the Received: December 1, 2006 Accepted: February 27, 2007 Reprint requests to: Dr. Yi-Fen Chen, Department of Dentistry, Chang Gung Memorial Hospital, No. 5, Fu-Hsing Street, Kweishan, Taoyuan, Taiwan 33375, ROC. J Dent Sci 2007‧Vol 2‧No1 only criterion) after treating asymptomatic teeth with pulp necrosis and chronic apical periodontitis. Walton and Fouad3 determined an incidence of flare-up of 3.17% using pain and/or swelling as the criteria in a prospective study, and with the same criteria, Imura and Zuolo4 found an incidence of flare-up of 1.58%. Other investigators5-7 have reported varying incidences of flare-ups, based on different criteria and sample sizes. Although many factors associated with flare-ups have been examined, those factors frequently related to the occurrence of flare-ups include the gender and age of patients8, the presence of a periapical lesion3,7-9, and a history of preoperative pain3,8. A prospective study involving a large number of teeth can clarify the factors related to the presence of posttreatment sequelae. Therefore, the purpose of this study was to examine the overall incidence of flare-ups in a total of 658 RCT cases performed during a period of 3 months at Chang Gung Memorial Hospital (CGMH), Linkou, Taiwan. Relationships of the incidence of flare-ups after RCT with patients’ demographics (age and gender), tooth type, pulp/periradicular diagnosis, the presence or absence of preoperative pain, initial RCT or retreatment, and type of operator were analyzed. 39 Y.F. Chen, Y.H. Lin, C.C. Chen, et al. MATERIALS AND METHODS Data on 658 teeth receiving either non-surgical initial RCT or retreatment in the Department of Endodontics, CGMH during a 3-month period from July to September 2002 were collected. These RCTs were performed by either senior residents or attending doctors. Each patient’s demographics, the tooth position, presenting symptoms, and the presence or absence of preoperative pain (spontaneous or percussion pain) were obtained at the patient’s first visit. The pulpal diagnosis (normal, irreversible pulpitis, pulp necrosis, reversible pulpitis, or previously treated) and periapical diagnosis (normal, chronic apical periodontitis, acute apical periodontitis, chronic periapical abscess, acute periapical abscess, or a non-endodontic lesion) of each treated tooth were also recorded according to the definition of the Glossary of Endodontic Terms 200316. Periapical radiography after RCT was performed to determine whether there was root canal overfilling. A special sheet was used to record all data for each patient. Treatment protocols were standardized: each patient was anesthetized with 2% xylestesin with or without epinephrine, a rubber dam was put in place, and a 3.0% NaOCl solution was used for irrigation of the root canal throughout the treatment. The working length (from the crown to 0.5 mm above the anatomical root apex) was measured using an electronic apex locator and confirmed by periapical radiography. Apical preparation was completed to the working length with either hand-held stainless steel files or nickel-titanium rotary instruments. In retreatment cases, the previous root canal filling material was removed using Gates Glidden burs, hand files, and eucalyptol, and then the root canal preparation was performed. All RCT cases were obturated with either gutta-percha cones or root canal sealer of canals (Showa ShizaI Kako, Tokyo ) using a lateral condensation technique or with Roth 801 root canal sealer (Roth International, Chicago, IL) using a vertical condensation technique. Root canal overfilling was defined as finding gutta-percha or sealer beyond the radiographic apex. Operators decided the best time to obturate the root canals based on the diagnosis of each tooth, clinical findings, and available chair time. Calcium hydroxide was the only intra-canal medication put in place if completing the RCT required more than 1 visit. Patients were instructed to phone the dentist or come back for an 40 emergency visit if the tooth was severely painful or swelling developed at the gingival or alveolar mucosa during the first 2~3 days after treatment. If a patient called with a complaint of severe pain and/or swelling and returned to the clinic for emergency treatment, a flare-up was recorded. A second flare-up following the first flare-up was not included in this survey. All of the above procedures were performed by 2 attending doctors and 2 senior residents. No cases of RCT handled by dental students were included in this study. The overall incidence of endodontic flare-ups was calculated. The correlations between the incidence of flare-ups and various related factors such as patients’ demographics, the tooth position, pretreatment symptoms, the pulpal / periradicular diagnosis, type of treatment, type of operator, and the presence or absence of overfilling were analyzed by the Chi-squared test. A p value of ≤ 0.05 was considered statistically significant. RESULTS Of the 658 teeth with RCT, flare-ups occurred in 13 teeth (1.98%). The demographic and clinical data of the 13 flare-up cases are described in Table 1. Correlations between the incidence of endodontic flare-ups and the patients’ demographic, clinical, and radiographic data are shown in Table 2. There were no significant correlations between the incidence of endodontic flare-ups and patients’ age, gender, tooth position, periapical diagnosis, pulpal diagnosis, type of treatment, or type of operator. However, the incidence of endodontic flare-up was significantly correlated with pretreatment spontaneous pain (p=0.025), percussion pain (p=0.000), and root canal overfilling (p=0.034). DISCUSSION Both case randomization and a large sample size are critical to clinical studies involving many variables. These two factors are generally easier to achieve in a retrospective study than a prospective study. However, standardization of clinical parameters in evaluating results is more accurate for a prospective study compared with a retrospective study. Because this clinical study was related to posttreatment flare-ups, many variables such as the criteria for evaluating the results and the RCT technique needed to be clarified J Dent Sci 2007‧Vol 2‧No1 Endodontic flare-ups Table 1. Demographic and clinical data of 13 flare-up cases Case number Tooth position Gender Pulpal diagnosis Periapical diagnosis Spontaneous pain Percussion pain Overfilling 1 #11 F PT CAP - - + 2 #21 F PT CAP - - - 3 #46 M IP N - + + 4 #24 M IP N - + + 5 #22 F PN CAP - - - 6 #13 F PT CAP - - - 7 #37 F PT CAP - + - 8 #12 F N N + - - 9 #46 F PT CAP + + - 10 #47 F RP N - - - 11 #37 M IP N + + - 12 #46 F PT CAP - - - 13 #37 F PT CAP + + - PT, previously treated; IP, irreversible pulpitis; PN, pulp necrosis; N, normal; RP, reversible pulpitis; CAP, chronic apical periodontitis. before the study began for comparison. Therefore, our investigation used a prospective study format which enabled us to analyze the association of demographic, clinical, and radiographic data of 658 RCT teeth with the incidence of endodontic flare-ups. The results of our study showed a low incidence of flare-ups (1.98%) after RCT, which was similar to those reported by Imura and Zuolo (1.58%)4 and Siqueira et al. (1.90%)11. It appears that when RCT is conducted under sound biological principles, with contemporary scientifically based techniques, by skillful operators like senior attending doctors or residents, a low overall incidence of endodontic flare-ups can be expected. The results of the present study showed no significant relationship of patients’ age, gender, or tooth type with the incidence of endodontic flare-ups. Our findings are in agreement with those from several previous studies3,4,12. In contrast, a retrospective study by Torabinejad8 showed a significant positive correlation of flare-ups with patients’ ages of between 40 and 59 years, female patients, and mandibular teeth. The present study also showed that 10 female patients experienced flare-ups among the 13 patients (Tables 1, 2). In general, female patients have more-sensitive responses to RCT than male patients. Since the J Dent Sci 2007‧Vol 2‧No 1 definition of flare-ups is relatively subjective, it may be easier for female than male patients to feel and remember the discomfort after RCT even when they undergo the same treatment. This might have led to more female cases of flare-ups being reported by this prospective study. An important diagnostic factor is the presence of preoperative pain when evaluating acute exacerbations after RCT. Many other studies3,4,8 showed higher frequencies of flare-ups in patients with preoperative pain. In this study, we also showed a significant relationship of the presence of preoperative spontaneous pain (4/13) and percussion pain (6/13) with a higher incidence of flare-ups. It appears that the presence of preoperative complaints is an excellent predicator for flare-ups. Many studies3,4,7,11 showed a significantly higher incidence of flare-ups in cases with a periapical lesion than in those without a periapical lesion. On the other hand, Fox et al.14 and Frank et al.15 found that an absence of periapical radiolucency was associated with a higher incidence of flare-ups and a higher level of postoperative pain. In the present study, the classification of the pulpal/periradicular diagnosis was based on terms defined by the American Association of Endodontists16. According to our survey, there was 41 Y.F. Chen, Y.H. Lin, C.C. Chen, et al. Table 2. Correlations between the incidence of endodontic flare-ups and patients’ demographic, clinical, and radiographic data Total No. of cases No. of cases of flare-up (%) 0.371 Patient age (year) 66 126 121 145 133 67 3 (4.55) 1 (0.79) 2 (1.65) 4 (2.76) 2 (1.50) 1 (1.49) Patient gender Male Female 248 410 3 (1.21) 10 (2.44) Tooth position Maxillary anterior Maxillary premolar Maxillary molar Mandibular anterior Mandibular premolar Mandibular molar 45 82 117 220 94 100 0 (0.00) 0 (0.00) 3 (2.56) 6 (2.73) 2 (2.13) 2 (2.00) Periapical diagnosis Normal Chronic apical periodontitis Acute apical periodontitis Chronic periapical abscess Acute periapical abscess Non-endodontic lesion 299 319 24 12 3 1 5 (1.67) 7 (2.19) 1 (4.17) 0 (0.00) 0 (0.00) 0 (0.00) Pulpal diagnosis Normal Irreversible pulpitis Pulpal necrosis Reversible pulpitis Previously treated 110 74 116 11 347 1 (0.91) 2 (2.70) 2 (1.72) 1 (9.09) 7 (2.02) Type of treatment Initial treatment Retreatment 274 384 5 (1.82) 8 (2.08) Type of operator Attending doctor Senior resident 389 269 7 (1.80) 6 (2.23) Spontaneous pain With Without 73 585 4 (5.48) 9 (1.54) Percussion pain With Without 50 608 6 (12.0) 7 (1.15) 0~18 19~29 30~39 40~49 50~64 > 65 1.000 0.731 0.626 0.378 1.000 0.750 0.025 0.000 Overfilling With Without 42 p value 0.034 38 620 3 (7.89) 10 (1.61) J Dent Sci 2007‧Vol 2‧No1 Endodontic flare-ups no significant difference in the frequency of flare-ups among cases with different previous periapical manifestations. These results might have been due to the small sample size in some groups of periapical pathoses such as acute and chronic periapical abscess. In addition, pulpal and periradicular diagnoses are often determined after clinical and radiographic examinations, and it usually takes some time to detect periradicular lesions on radiographs. Patients with a preoperative lesion might have had a higher pain threshold and been less sensitive to discomfort. In case 8 (Table 1), the patient had preoperative pain caused by a periodontal ligament (PDL) injury from heavy occlusion or traumatic force of bruxism. In this situation, the PDL may have been inflamed with abundant chemotactic factors around the tooth, and this much more easily can cause postoperative pain of the tooth. The retreatment procedure did not cause any additional posttreatment flare-ups in the present study. This finding was in agreement with those of Walton and Fouad3 and Siqueira11. Removal of the inflamed contents and administration of appropriate medications may account for the lower incidence of flare-ups. In contrast, Trope et al.7 and Imura and Zuolo4 showed a significantly higher incidence of flare-ups in retreatment cases than in the initial treatment cases. Mechanical irritation, including over-instrumentation and root canal overfilling, can cause periradicular inflammation13. Apical extrusion of debris during gutta-percha point removal may cause acute exacerbation of chronic inflammatory conditions17. Therefore, apical over-instrumentation and overfilling can disrupt normal periapical healing, and lead to the development of new periapical lesions18. Clinically, extrusion of filling materials beyond the root apex can occur in teeth with an unsatisfactory apical stop as with an over-instrumented apex. Georgopoulou et al.10 observed an increase in flare-ups in cases with over-instrumentation. In fact, penetration of the apical foramen with large instruments not only can result in severe periapical tissue injury, but it can also cause lack of an apical stop and extrusion of filling materials during obturation of the root canal system. In a long-term follow-up study, non-vital teeth with periapical lesions that were overfilled had a significantly reduced success rate of just 76%, compared to 94% for those teeth which were filled close to the apex19. Several other follow-up studies J Dent Sci 2007‧Vol 2‧No 1 have also reported that the presence of excess root filling material is associated with impaired healing of periapical lesions19,20. Although the reasons for this have not yet been clarified, there may be several events which occur individually or collectively to interrupt healing. These include procedures involved in canal preparation that may lead to overfilling such as: (i) damage to the root apex and periapical tissues through over-instrumentation, (ii) extrusion of debris which may contain microorganisms, elements of necrotic pulp, and infected or uninfected dentin chips from the root canal21,22, and (iii) the presence of excess root filling material in the periapical tissue which may act as a foreign body and cause retardation of the tissue repair process. In the present study, 38 (7.89%) cases of root canal overfilling (37 cases of guttapercha point and 1 case of cement overfilling) experienced endodontic flare-ups. However, Morse et al.2 intentionally enlarged the apical foramen of teeth that required RCT and reported a lower incidence of “flare-ups” than those without apical penetration. An unexpected result was that there was no significantly higher incidence of flare-ups in teeth treated by senior residents compared to teeth treated by attending doctors. This can possibly be explained by operators with sufficient RCT experience using sound biological principles and contemporary techniques can achieve good endodontic outcomes after RCT, resulting in no difference in the occurrence of flare-ups between the senior resident and attending doctor groups. We concluded that the incidence of endodontic flare-up was 1.98% after RCT in this study. The occurrence of flare-ups was significantly related to preoperative symptoms, such as spontaneous pain and percussion pain. There was also a highly significant association of the frequency of flare-ups with the presence of root canal overfilling. REFERENCES 1. Samuel S, Irving J, Naidorf D. Flare-ups in endodontics: I. etiological factors. J Endod, 30: 476-481, 2004. 2. Morse D, Koren L, Positojv E. Infections flare-ups: induction and prevention. Int J Psychosom, 33 (Special Issue): 5-63, 1986. 3. Richard W, Ashraf F. Endodontic interappointment flare-ups: a prospective study of incidence and related factors. J Endod, 18: 172-177, 1992. 4. Imura N, Zuolo ML. Factors associated with endodontic 43 Y.F. Chen, Y.H. Lin, C.C. Chen, et al. flare-ups: a prospective study. Int Endod J, 28: 261-265, 1995. 5. Mata E, Koren LZ, Morse DR, Sinai IH. Prophylactic use of Penicillin V in teeth with necrotic pulps and asymptomatic periapical radiolucencies. Oral Surg, 60: 201-207, 1985. 6. Balban FS, Skidmore AE, Griffin JA. Acite exacerbations following initial treatment of necrotic pulp. J Endod, 10: 78-81, 1984. 7. Trope M. Relationship of intracanal medicaments to endodontic flare-ups. Endod Dent Traumatol, 6: 226-229, 1990. 8. Torabinejad M, Kettering JD, Mcgraw JC, Cummings RR, Dwyer TG, Tobias TT. Factors associated with endodontic interappointment emergencies of teeth with necrotic pulps. J Endod, 14: 261-266, 1988. 9. Goldman M, Rankin C, Mehlman R, Santa C. The immunologic implications and clinical management of the endodontic flare-up. Compend Contin Educ Dent, 10: 126-130, 1987. 10. Georgopoulou M, Anastassiadis P, Sykara S. Pain after chempmechanical preparation. Int Endod J, 19: 309-314, 1986. 11. Siqueira JF. Incidence of postoperative pain after intracanal procedures based on an antimicrobial strategy. J Endod, 28: 457-460, 2002. 12. Eleazer PD, Eleazea KR. Flare-up rate in pulpally necrotic molars in one-visit versus two-visit endodontic treatment. J Endod, 24: 614-616, 1998. 13. Siqueira JF. Microbial causes of endodontic flare-ups. Int Endod J, 36: 453-463, 2003. 44 14. Fox J, Atkinson JS, Dinin AP, Greenfield E, Hechtman, Reeman CA, Salkind M, Todaro CJ. Incidence of pain following one-visit endodontic treatment. Oral Surg Oral Med Oral Pathol, 30: 123-130, 1970. 15. Frank AL, Glick DH, Weichman JA, Harvey H. The intracanal use of sulfathiazole in endodontics to reduce pain. J Am Dent Assoc, 77: 102-106, 1968. 16. The Glossary terms of American Association of Endodontists 2003. 17. Seltzer S, Naidorf IJ. Flare-ups in endodontics: I. Etiological factors. J Endod, 11: 472-478, 1985. 18. Bergenholtz G, Lekholm U, Milthon R, Engstrom B. Influence of apical over-instrumentation and overfilling on re-treated root canals. J Endod, 5: 310-314, 1979. 19. Sjogren U, Hagglund B, Sundqvist G, Wing K. Factors affecting the long-term results of endodontic treatment. J Endod, 16: 498-504, 1990. 20. Kerekes K, Tronstad L. Long-term results of endodontic treatment performed with a standardized technique. J Endod, 5: 83-90, 1979. 21. Holland R, De Souza V, Nery MJ, de Mello W, Bernabe PF, Otoboni Filho JA. Tissue reactions following apical plugging of the root canal with infected dentin chips. A histological study in dogs' teeth. Oral Surg Oral Med Oral Pathol, 49: 366-369, 1980. 22. Yoshida M, Fukushima H, Yamamoto K, Ogawa K, Toda T, Sagawa H. Correlation between clinical symptoms and microorganisms isolated from root canals of teeth with periapical pathosis. J Endod, 13: 24-28, 1987. J Dent Sci 2007‧Vol 2‧No1