- Email: [email protected]
12-month Success of Cracked Teeth Treated with Orthograde Root Canal Treatment
Clinical Research
12-month Success of Cracked Teeth Treated with Orthograde Root Canal Treatment Keith V. Krell, DDS, MS, MA,* and Daniel J. Caplan, DDS, PhD† Abstract Introduction: Long-term studies examining the treatment outcomes of ‘‘cracked teeth’’ that received orthograde root canal treatment in the United States do not exist. The purpose of the present study was to examine the distribution and 1-year treatment outcomes of cracked teeth receiving orthograde root canal treatment in 1 private endodontic practice over a 25-year period. Methods: A total of 3038 cracked teeth were initially examined, and data from 2086 unique patients were analyzed. Pulpal and periapical diagnoses, year of treatment, tooth type, restorative material, and number of restored surfaces at the time of examination were recorded for all patients. Periodontal probing depths were also recorded. The patients’ age and sex were added retrospectively for all patients whose data were available. Univariate frequency distributions for all collected variables were evaluated. Bivariate associations were analyzed between explanatory variables and the success of the root canal therapy. Results: Of the 2086 cracked teeth observed among unique patients, the most common were mandibular second molars (36%) followed by mandibular first molars (27%) and maxillary first molars (18%). Among the 363 teeth eligible for multivariable regression analysis, 296 (82%) were deemed successes after 1 year. There were no statistically significant differences in success based on pulpal diagnosis (irreversible pulpitis, 85%; necrosis, 80%; previously treated, 74%), patients’ age, sex, year of treatment, tooth type, restorative material, or number of restored surfaces at the time of examination. The 3 factors most significant in bivariate analyses were pocket depth, distal marginal ridge crack, and periapical diagnosis, which were used to generate a prognostic index for success of orthograde root canal therapy in cracked teeth called the Iowa Staging Index. Conclusions: The results of this study suggest that cracked teeth that received root canal treatment can have prognoses at higher success rates than previously reported. The Iowa Staging Index may prove to be useful in clinical treatment decision making. (J Endod 2018;-:1–6)
Key Words Cracked teeth, Iowa Staging Index, orthograde root canal treatment, prognosis
C
racks in enamel and Significance extending into dentin This study is relevant to cracked teeth and outhave been formally recogcomes after orthograde root canal treatment. nized as a diagnostic problem since the 1950s (1, 2). The term ‘‘cracked tooth syndrome’’ was coined by Cameron (3) and referred to teeth with sensitivity to biting and unexplained thermal sensitivity. The cracks were usually mesial to distal, and mandibular second molars had the highest incidence of cracks. Since 1964, several studies have assessed factors associated with cracks and fractures in teeth. Some of these studies failed to define whether they were examining coronal-originating (enamel-dentin) cracks or radicular originating (cementumdentin) cracks. In 1997, the American Association of Endodontists published ‘‘Cracking the Cracked Tooth Code’’ in Colleagues for Excellence (4). In 2008, a revised edition entitled ‘‘Cracking the Cracked Tooth Code: Detection and Treatment of Various Longitudinal Tooth Fractures’’ (5) was published. In both publications, 5 types of cracks or fractures were defined: craze lines, fractured cusps, cracked tooth, split tooth, and vertical root fracture. Cracked teeth had a history of cold sensitivity and acute pain upon chewing and were considered ‘‘greenstick’’ fractures. Clinically, the cracks were in a mesial-to-distal plane, and identification might require the removal of any class II restoration. With the restoration removed, the mesial and distal marginal ridges could be examined for cracks in conjunction with dyes, transillumination, and magnification. An explorer may or may not be able to detect the crack. There would be no radiographic changes unless there had been pulpal necrosis caused by bacterial ingress through the crack. Periodontal probing depths would vary depending on the apical extension of the crack. Ailor (6) reported that the treatment of cracked teeth was dependent on tooth restorability and pulpal status. Kahler (7) suggested a decision tree to be used when evaluating and restoring cracked teeth. The final treatment was always cuspal coverage regardless of whether or not root canal treatment was needed. In a previous study of 127 cracked teeth diagnosed with reversible pulpitis, all teeth were provided crowns, and ultimately 20% of the teeth (n = 27) required root canal treatment after the crown was placed (8). Abbott and Leow (9) reported similar findings in a subsequent study. Opdam et al (10) placed bonded intracoronal composite and full-coverage restorations in teeth with early detection of cracks; 85% of the composite and 100% of the cuspal coverage restorations did not require root canal treatment after 7 years. When the pulpal diagnosis upon discovery of the crack is irreversible pulpitis or necrosis, the recommendation to proceed with root canal treatment becomes dependent on the restorability of the tooth. Teeth with deep pockets associated with the crack,
From the Departments of *Endodontics and †Preventive and Community Dentistry, University of Iowa, Iowa City, Iowa. Address requests for reprints to Dr Keith V. Krell, Department of Endodontics, University of Iowa, Iowa City, IA. E-mail address: [email protected] 0099-2399/$ - see front matter Copyright ª 2018 American Association of Endodontists. https://doi.org/10.1016/j.joen.2017.12.025
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Clinical Research when there is otherwise no periodontal bone loss, implies that the crack has extended onto the root surface and is most likely not restorable (ie, the crown margin would not be able to cover the extent of the crack). These teeth should be considered for extraction. When teeth have irreversible pulpitis and are restorable, root canal treatment followed with a crown has resulted in a 90% retention of teeth after 2 years (11). Treating cracked teeth with a pulpal diagnosis of necrosis has become controversial. Berman and Kuttler (12) suggest all cracked teeth with necrotic pulps should be extracted because of unpredictable outcomes and therefore needless expenses, but Kang et al (11) did not find that pulp necrosis was a factor in tooth survival. Long-term studies examining the treatment outcomes of cracked teeth receiving orthograde root canal treatment in the United States do not exist. The purpose of the present study was to examine the distribution and 1-year treatment outcomes of cracked teeth receiving orthograde root canal treatment in 1 private endodontic practice over a 25-year period.
Materials and Methods The study was approved by the Institutional Review Board at the University of Iowa, Iowa City, IA. Study subjects were patients treated by 1 endodontist, and during the 25-year period, all patients were sent recall cards at 1 year, so there was at least an opportunity for 1year recall. The same endodontist provided the diagnosis, treatment, and recall examination over the study period. For each patient, name, tooth number, existing restoration, pulpal diagnosis, periapical diagnosis, and starting date and ending date of treatment were entered into a database. The location(s) of the crack and associated periodontal probing depths also were recorded. The categories of age and sex were added retrospectively in 2016 for patients whose records were still available. The following clinical tests and evaluations were performed on all teeth at the time of presentation and diagnosis: 1. 2. 3. 4.
Periapical radiograph Pulpal response to cold and/or hot Periapical response to pressure, palpation, and percussion Buccal and lingual periodontal probing depth recording in the mesial and distal interproximal spaces and furcas (directed precisely where marginal ridge cracks were identified to indicate the deepest probing of the crack) 5. Direct transillumination and visualization with and without magnification. The identified crack had to block light transmission and show a definite shadow with both buccal and lingual coronal light placement. Teeth not exhibiting a shadow were considered to have ‘‘crazings’’ and were not included in this analysis 6. Responses to biting on various cusps of the diagnosed tooth, with at least 1 cusp exhibiting pain to biting on either a Burlew wheel or Tooth Slooth (Professional Results, Inc, Laguna Niguel, CA). The endodontist’s instrumentation technique changed over the 25-year span as new technology was adapted. Ten years after beginning private practice, nickel-titanium instrumentation was incorporated into the debridement procedures of the endodontist. All teeth were filled using lateral condensation and Roth’s 801 sealer (Roth International, Chicago, IL). No teeth were included in this analysis that were not confirmed by direct visualization of the crack. Teeth diagnosed as cusp fractures, split teeth, and vertical root fractures also were excluded from this analysis (13). Restorations were removed only for patients with pulpal diagnoses who required root canal treatment. All patients who returned for the 1-year recall were evaluated for the presence or absence of symptoms, radiographic resolution of 2
Krell and Caplan
previous lesions, and the presence of a crown by the endodontist. Success of the root canal therapy was defined as the absence of signs or symptoms plus resolution of any previous radiographic pathosis. ‘‘Failure’’ was defined as the persistence of signs or symptoms with no change in the radiographic pathosis, enlarged radiographic pathosis, or the development of radiographic pathosis when there had been none previously. Questionable status was assigned when there was absence of signs and symptoms but failure of complete resolution of previous radiographic pathosis, even if there was a reduction in lesion size. All statistical analyses were conducted using SAS version 9.4 (SAS, Cary, NC). Univariate frequency distributions for all collected variables were evaluated. Because patients could have had more than 1 tooth treated during the study period, 1 tooth per patient was selected at random to avoid potentially correlated outcomes within patients (14). Bivariate associations were analyzed between explanatory variables and success of root canal therapy. Finally, the 3 variables deemed as most predictive of success in bivariate analyses were used to generate a ‘‘Cracked Tooth Prognostic Index’’ (also known as the ‘‘Iowa Index’’) for potential use by practitioners when informing patients about treatment options for cracked teeth.
Results Of the 3038 cracked teeth in the original database, 952 were excluded from the analysis because they represented multiple teeth from the same patient, leaving 1 tooth per patient in 2086 unique patients. Mandibular second molars (36%) had the highest incidence followed by the mandibular first molars (27%) for a total of 63% for all teeth. Figure 1 depicts the stratification of the 2086 teeth into 3 mutually exclusive subsets:
Diagnosed Cracked Teeth (n=2086)
Not treated with Root Canal Therapy (n=680)
Treated with Root Canal Therapy (n=1406)
Did not return for 12-month follow-up visit (n=1026)
Potentially Eligible for Bivariate Analysis (n=380) Ineligible for bivariate analysis (n=17): - Outcome “questionable” (n=13) - Patient <18 years old (n=1) - Wisdom tooth (n=1) - Reversible pulpitis (n=1) - Unknown size of restoration (n=1) Included in Bivariate Analysis (n=363)
Figure 1. Stratification of the 2086 teeth into 3 mutually exclusive subsets.
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Clinical Research 1. 680 teeth not treated with root canal therapy 2. 1026 teeth treated with root canal therapy but lost to follow-up 3. 380 teeth treated with root canal therapy and followed with a 12month recall examination Table 1 shows the presenting conditions of teeth in each of the 3 groups. P values are not presented in this table because most variables did not differ to a clinically meaningful degree among the 3 groups although teeth not treated with root canal therapy appeared more likely to have probing pocket depths $5 mm or to have had a pulpal diagnosis of reversible pulpitis. Of the 380 teeth eligible for further analyses, 17 were excluded, including 13 with a ‘‘questionable’’ outcome, 1 with reversible pulpitis, 1 with a missing value for restoration surfaces, 1 that was a wisdom tooth, and 1 in a patient under 18 years of age (Fig. 1). This left 363 nonwisdom teeth in adult patients, all with an initial pulpal diagnosis of irreversible pulpitis, necrosis, or previously treated and an outcome
of either ‘‘success’’ or ‘‘failure’’ at 12 months, which comprised the data set for the present analysis. Table 2 shows the results of bivariate analyses between the explanatory variables and 12-month success. A total of 296 teeth (82%) were classified as ‘‘successes,’’ with the 3 variables most predictive of failure being: 1. The presence of marginal ridge cracks (only 62% of teeth with cracks on both mesial and distal marginal ridges were successes) 2. Teeth with mesial or distal probing pocket depths $5 mm (ranging from 31%–39% success) 3. Periapical diagnosis of chronic apical periodontitis (CAP), suppurative apical periodontitis (SAP), or acute apical abscess (AAA), with only a 74% success rate in these teeth compared with an 85% success rate in teeth with periapical diagnosis of normal or acute apical periodontitis
TABLE 1. Percent of Teeth by Treatment and Follow-up (FU) Category Level
Overall (N = 2086)
Not RCT (n = 680)
RCT but lost to FU (n = 1026)
RCT and ollowed (n = 380)
18–44 45–54 55+ Missing Male Female #1996 1997–2005 $2006 Upper second molar Upper first molar Upper second premolar Upper first premolar Lower second molar Lower first molar Lower second premolar Lower first premolar Third molar Amalgam Composite Metal None Other/missing/temp 0 1 2 3 5 Yes No Yes No Yes No Missing Yes No Missing Reversible Irreversible Necrosis Previous Tx Normal AAP CAP SAP AAA
24 25 23 28 38 62 35 32 33 9 18 4 4 36 27 1 0 1 56 6 18 8 12 7 49 16 5 23 53 47 60 40 9 44 47 16 44 40 18 36 35 11 49 23 12 6 10
22 23 28 26 36 64 31 30 39 11 18 3 3 35 27 1 0 2 56 5 22 8 10 7 42 21 4 25 55 45 62 38 19 36 45 33 29 39 51 8 28 13 56 15 9 6 14
25 26 20 28 40 60 34 32 34 9 19 4 4 36 26 1 0 1 55 7 16 7 14 7 52 12 5 23 53 47 59 41 4 48 48 8 50 41 4 50 38 8 46 28 13 4 9
23 25 21 30 32 68 44 37 19 8 17 4 4 38 28 1 0 0 58 8 14 9 12 8 50 15 5 22 53 47 61 39 4 49 46 6 54 40 0 47 41 12 44 24 16 8 7
Variable Patient age (y)
Patient sex Date of treatment Tooth type
Restoration material
Restoration surfaces
Mesial MR crack Distal MR crack Mesial pocket $5 mm Distal pocket $5 mm Pulpal diagnosis
Periapical diagnosis
AAA, acute apical abscess; AAP, acute apical periodontitis; CAP, chronic apical periodontitis; MR, marginal ridge; RCT, root canal treatment; SAP, suppurative apical periodontitis; Tx, treatment.
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Clinical Research TABLE 2. Bivariate Associations between Presenting Characteristics and Endodontic Success Variable
Level
Number of patients
Number (%) of successes
P value
Total patient age (y)
NA 18–44 45–54 55+ Missing Male Female #1996 1997–2005 $2006 Lower first molar Upper first molar Upper second molar Lower second molar Premolar Amalgam Composite Metal None Other/missing/temp 0 1 2 3 5 Neither MMR only DMR only Both Missing (1–2) 3 4 $5 Missing (1–2) 3 4 $5 Irreversible Necrosis Previous Tx Normal/AAP CAP/SAP/AAA
363 86 89 76 112 117 246 162 134 67 101 61 27 142 32 210 28 49 30 46 30 185 51 18 79 1 141 166 55 165 168 14 16 147 170 23 23 178 142 43 256 107
296 (82) 72 (84) 80 (90) 58 (76) 86 (77) 91 (78) 205 (83) 129 (80) 115 (86) 52 (78) 88 (87) 51 (84) 22 (81) 111 (78) 24 (75) 169 (80) 23 (82) 40 (82) 25 (83) 39 (85) 25 (83) 151 (82) 41 (80) 14 (78) 65 (82) 1 (100) 128 (91) 133 (80) 34 (62) 132 (80) 146 (87) 13 (93) 5 (31) 133 (90) 140 (82) 14 (61) 9 (39) 151 (85) 113 (80) 32 (74) 217 (85) 79 (74)
NA .059
Patient sex Date of first visit Tooth type
Restoration material
Restoration surfaces
Marginal ridge cracks
Mesial pocket (mm)
Distal pocket (mm)
Pulpal diagnosis Periapical diagnosis
.202 .249 .373
.968
.989
<.001
<.001
<.001
.220 .014
AAA, acute apical abscess; AAP, acute apical periodontitis; CAP, chronic apical periodontitis; DMR, distal marginal ridge; MMR, mesial marginal ridge; NA, not applicable; SAP, suppurative apical periodontitis; Tx, treatment. Bold values indicate P values where P < .05 and are significant.
The patient’s age, sex, year of treatment, tooth type, restorative material present at the time of examination, and number of surfaces restored were not associated with treatment success. Finally, Figure 2 shows how the 3 factors that were most significant in the bivariate analyses were used to generate the following novel prognostic index for the success of orthograde root canal therapy in cracked teeth: 1. Iowa stage I = no probing pocket depths $5 mm and no crack across the distal marginal ridge (37% of teeth, 93% success) 2. Iowa stage II = no probing pocket depths $5 mm, having a crack across the distal marginal ridge, and not having a periapical diagnosis of CAP/SAP/AAA (39% of teeth, 84% success) 3. Iowa stage III = no probing pocket depths $5 mm, having a crack across the distal marginal ridge, and having a periapical diagnosis of CAP/SAP/AAA (15% of teeth, 69% success) 4. Iowa stage IV = $1 mesial or distal probing pocket depth $5 mm (8% of teeth, 41% success).
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Discussion To date, this is the largest and most lengthy data collection effort with regard to cracked teeth by a single practitioner, with data collection occurring between 1989 and 2015. There was an opportunity for a 1-year recall for all treated patients (N = 46,253) during that time. During this time period, the periapical diagnostic terminology changed. Periapical diagnostic terms that did not change included ‘‘normal’’ and ‘‘acute apical abscess.’’ Periapical terms that changed effective 2009 include ‘‘chronic apical periodontitis’’ to ‘‘asymptomatic apical periodontitis,’’ ‘‘acute apical periodontitis’’ to ‘‘symptomatic apical periodontitis,’’ and ‘‘suppurative apical periodontitis’’ to ‘‘chronic apical abscess’’ (15). Because the data collection was started well in advance of the most recent terminology changes, the older terminology is used here. In the present analysis, the overall distribution of teeth identified with cracks did not differ from that reported in other published studies. The mandibular second molar (36%) had the highest incidence
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Clinical Research Distal Marginal Ridge cracked?
No
Iowa Stage I: 37% of cases (93% success)
No
Iowa Stage II: 39% of cases (84% success)
Yes No Periapical Diagnosis CAP, SAP, or AAA?
Mesial or Distal Probing Pocket Depth ≥5 mm?
Yes
Yes
Iowa Stage III: 15% of cases (69% success)
Iowa Stage IV: 8% of cases (41% success)
Figure 2. Iowa Staging Index.
followed by the mandibular first molar (27%) for a total of 63% for the mandibular molars (3, 6, 8, 9, 16, 17). Older age was found to be marginally associated with a lower success rate (76% success in patients >55 years old vs 90% in those ages 45–54 years) although age was not available for many patients in this analysis, which would have lowered the statistical power available to detect differences. In other studies (18), the incidence of cracked teeth was found to increase with age. There were slightly more females than males seen for cracked teeth in this analysis, but this might have resulted from referral patterns of the local dentists. Success rates throughout the time period did not differ significantly. Success decreased with increasing pulpal involvement (85% for teeth with irreversible pulpitis, 80% for necrotic teeth, and 74% for previously treated teeth). Although these differences were not statistically significant, these findings are similar to those of Tan et al (19). Pulpal diagnosis of necrosis associated with tooth fracture has been a source of debate regarding root canal therapy versus extraction as the appropriate treatment recommendation. Berman and Kuttler (12) have argued that because of variability in outcomes, extraction should be recommended for cracked teeth with necrotic pulps and minimal restorations. This study would refute that modality as long as there are not probing pocket depths $5 mm and a crown is placed after root canal treatment. In the present analysis, the single most important factor related to failure was having a probing pocket depth $5 mm. This is similar to the findings of Tan et al (19), Kim et al (18), and Kang et al (11). The presence of a distal marginal ridge crack also conferred more risk of failure than mesial cracks. This has been supported by Hilton et al (20) in an analysis of data from the National Dental Practice–Based Research Network.
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In our opinion, the most important limitation of this study was not having a higher recall rate. All patients were offered a 1-year recall visit at no charge at the time treatment was completed, but despite that only 27% of treated patients returned for recall. Other long-term outcomes studies have had monetary incentives and have yielded recall rates of 50% (21), and an institutional outcomes study on cracked teeth had a 43% recall rate (22). Speculation as to why patients did not return could range from ‘‘they were asymptomatic and didn’t think they needed to come’’ to ‘‘the tooth was extracted,’’ so nonresponse bias, a bias common to most in vivo endodontic follow-up studies, could potentially have affected our results. The ultimate question that this study tried to answer was ‘‘What should providers tell patients who have cracked teeth that need root canal treatment about the endodontic prognosis they could expect if the tooth were treated by an endodontist?’’ The Iowa Staging Index is our initial attempt to address this question and is based on the findings described here. The earlier the diagnosis, the better the prognosis, as illustrated in 3 previous studies of cracked teeth with reversible pulpitis (8–10). When endodontic treatment is deemed necessary, the Iowa Staging Index presented here potentially could help with treatment decision making and the informed consent process. Ideally, before this index is used in clinical practice, it should be validated using prospective cohort designs in various private practice and institutional settings.
Conclusions In this analysis of 363 cracked teeth treated with orthograde root canal therapy by a single endodontist in private practice over a 25-year period, 296 (82%) were deemed to be ‘‘successes’’ at the 1-year recall examination with the factors most associated with failure being the
Orthograde Root Canal Treatment
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Clinical Research presence of 1 probing pocket depth $5 mm; presence of a crack across the distal marginal ridge; and periapical diagnosis of CAP, SAP, or AAA. Results suggest that cracked teeth provided with root canal treatment can have prognoses that can result in higher success rates than previously reported.
Acknowledgments The authors deny any conflicts of interest related to this study.
References 1. Gibbs JW. Cuspal fracture odontalgia. Dent Digest 1954;60:158. 2. Ritchey B, Mendenhall R, Orban B. Pulpitis resulting from incomplete tooth fracture. Oral Surg Oral Med Oral Pathol 1957;10:665–70. 3. Cameron CE. Cracked-tooth syndrome. J Am Dent Assoc 1964;68:405–11. 4. American Association of Endodontists. Cracking the cracked tooth code. Colleagues for Excellence. Chicago: American Association of Endodontists; 1997: 1–13. 5. Rivera EM, Walton RE. Cracking the cracked tooth code: detection and treatment of various longitudinal tooth fractures. In: Colleagues for Excellence. Chicago: American Association of Endodontists; 2008. 6. Ailor JE Jr. Managing incomplete tooth fractures. J Am Dent Assoc 2000;131: 1168–74. 7. Kahler W. The cracked tooth conundrum: terminology, classification, diagnosis, and management. Am J Dent 2008;21:275–82. 8. Krell KV, Rivera EM. A six year evaluation of cracked teeth diagnosed with reversible pulpitis: treatment and prognosis. J Endod 2007;33:1405–7. 9. Abbott P, Leow N. Predictable management of cracked teeth with reversible pulpitis. Aust Dent J 2009;54:306–15.
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10. Opdam NJ, Roeters JJ, Loomans BA, Bronkhorst EM. Seven-year clinical evaluation of painful cracked teeth restored with a direct composite restoration. J Endod 2008; 34:808–11. 11. Kang SH, Kim BS, Kim Y. Cracked teeth: distribution, characteristics, and survival after root canal treatment. J Endod 2016;42:557–62. 12. Berman LH, Kuttler S. Fracture necrosis: diagnosis, prognosis assessment, and treatment recommendations. J Endod 2010;36:442–6. 13. Rivera EM, Walton RE. Longitudinal fractures. In: Torabinejad M, Walton RE, eds. Principles and Practice of Endodontics, 4th ed. Philadelphia: Saunders; 2009: 108–28. 14. Caplan DJ, Slade GD, Gansky SA. Complex sampling: implications for data analysis. J Public Health Dent 1999;59:52–9. 15. Gutmann JL, Baumgartner JC, Gluskin AH, et al. Identify and define all diagnostic terms for periapical/periradicular health and disease states. J Endod 2009;35: 1658–74. 16. Hiatt WH. Incomplete crown-root fracture in pulpal-periodontal disease. J Periodontol 1973;44:369–79. 17. Cameron CE. The cracked tooth syndrome: additional findings. J Am Dent Assoc 1976;93:971–5. 18. Kim SY, Kim SH, Cho SB, et al. Different treatment protocols for different pulpal and periapical diagnoses of 72 cracked teeth. J Endod 2013;39: 449–52. 19. Tan L, Chen NN, Poon CY, Wong HB. Survival of root filled cracked teeth in a tertiary institution. Int Endod J 2006;39:886–9. 20. Hilton TJ, Funkhouser E, Ferracane JL, et al. Correlation between symptoms and external characteristics of cracked teeth: findings from The National Dental Practice-Based Research Network. J Am Dent Assoc 2017;148: 246–2561. 21. Marquis VL, Dao T, Farzaneh M, et al. Treatment outcome in endodontics: the Toronto Study. Phase III: initial treatment. J Endod 2006;32:299–306. 22. Sim IG, Lim TS, Krishnaswamy G, Chen NN. Decision making for retention of endodontically treated posterior cracked teeth: a 5-year follow-up study. J Endod 2016;42:225–9.
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12-month Success of Cracked Teeth Treated with Orthograde Root Canal Treatment Keith V. Krell, DDS, MS, MA,* and Daniel J. Caplan, DDS, PhD† Abstract Introduction: Long-term studies examining the treatment outcomes of ‘‘cracked teeth’’ that received orthograde root canal treatment in the United States do not exist. The purpose of the present study was to examine the distribution and 1-year treatment outcomes of cracked teeth receiving orthograde root canal treatment in 1 private endodontic practice over a 25-year period. Methods: A total of 3038 cracked teeth were initially examined, and data from 2086 unique patients were analyzed. Pulpal and periapical diagnoses, year of treatment, tooth type, restorative material, and number of restored surfaces at the time of examination were recorded for all patients. Periodontal probing depths were also recorded. The patients’ age and sex were added retrospectively for all patients whose data were available. Univariate frequency distributions for all collected variables were evaluated. Bivariate associations were analyzed between explanatory variables and the success of the root canal therapy. Results: Of the 2086 cracked teeth observed among unique patients, the most common were mandibular second molars (36%) followed by mandibular first molars (27%) and maxillary first molars (18%). Among the 363 teeth eligible for multivariable regression analysis, 296 (82%) were deemed successes after 1 year. There were no statistically significant differences in success based on pulpal diagnosis (irreversible pulpitis, 85%; necrosis, 80%; previously treated, 74%), patients’ age, sex, year of treatment, tooth type, restorative material, or number of restored surfaces at the time of examination. The 3 factors most significant in bivariate analyses were pocket depth, distal marginal ridge crack, and periapical diagnosis, which were used to generate a prognostic index for success of orthograde root canal therapy in cracked teeth called the Iowa Staging Index. Conclusions: The results of this study suggest that cracked teeth that received root canal treatment can have prognoses at higher success rates than previously reported. The Iowa Staging Index may prove to be useful in clinical treatment decision making. (J Endod 2018;-:1–6)
Key Words Cracked teeth, Iowa Staging Index, orthograde root canal treatment, prognosis
C
racks in enamel and Significance extending into dentin This study is relevant to cracked teeth and outhave been formally recogcomes after orthograde root canal treatment. nized as a diagnostic problem since the 1950s (1, 2). The term ‘‘cracked tooth syndrome’’ was coined by Cameron (3) and referred to teeth with sensitivity to biting and unexplained thermal sensitivity. The cracks were usually mesial to distal, and mandibular second molars had the highest incidence of cracks. Since 1964, several studies have assessed factors associated with cracks and fractures in teeth. Some of these studies failed to define whether they were examining coronal-originating (enamel-dentin) cracks or radicular originating (cementumdentin) cracks. In 1997, the American Association of Endodontists published ‘‘Cracking the Cracked Tooth Code’’ in Colleagues for Excellence (4). In 2008, a revised edition entitled ‘‘Cracking the Cracked Tooth Code: Detection and Treatment of Various Longitudinal Tooth Fractures’’ (5) was published. In both publications, 5 types of cracks or fractures were defined: craze lines, fractured cusps, cracked tooth, split tooth, and vertical root fracture. Cracked teeth had a history of cold sensitivity and acute pain upon chewing and were considered ‘‘greenstick’’ fractures. Clinically, the cracks were in a mesial-to-distal plane, and identification might require the removal of any class II restoration. With the restoration removed, the mesial and distal marginal ridges could be examined for cracks in conjunction with dyes, transillumination, and magnification. An explorer may or may not be able to detect the crack. There would be no radiographic changes unless there had been pulpal necrosis caused by bacterial ingress through the crack. Periodontal probing depths would vary depending on the apical extension of the crack. Ailor (6) reported that the treatment of cracked teeth was dependent on tooth restorability and pulpal status. Kahler (7) suggested a decision tree to be used when evaluating and restoring cracked teeth. The final treatment was always cuspal coverage regardless of whether or not root canal treatment was needed. In a previous study of 127 cracked teeth diagnosed with reversible pulpitis, all teeth were provided crowns, and ultimately 20% of the teeth (n = 27) required root canal treatment after the crown was placed (8). Abbott and Leow (9) reported similar findings in a subsequent study. Opdam et al (10) placed bonded intracoronal composite and full-coverage restorations in teeth with early detection of cracks; 85% of the composite and 100% of the cuspal coverage restorations did not require root canal treatment after 7 years. When the pulpal diagnosis upon discovery of the crack is irreversible pulpitis or necrosis, the recommendation to proceed with root canal treatment becomes dependent on the restorability of the tooth. Teeth with deep pockets associated with the crack,
From the Departments of *Endodontics and †Preventive and Community Dentistry, University of Iowa, Iowa City, Iowa. Address requests for reprints to Dr Keith V. Krell, Department of Endodontics, University of Iowa, Iowa City, IA. E-mail address: [email protected] 0099-2399/$ - see front matter Copyright ª 2018 American Association of Endodontists. https://doi.org/10.1016/j.joen.2017.12.025
JOE — Volume -, Number -, - 2018
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Clinical Research when there is otherwise no periodontal bone loss, implies that the crack has extended onto the root surface and is most likely not restorable (ie, the crown margin would not be able to cover the extent of the crack). These teeth should be considered for extraction. When teeth have irreversible pulpitis and are restorable, root canal treatment followed with a crown has resulted in a 90% retention of teeth after 2 years (11). Treating cracked teeth with a pulpal diagnosis of necrosis has become controversial. Berman and Kuttler (12) suggest all cracked teeth with necrotic pulps should be extracted because of unpredictable outcomes and therefore needless expenses, but Kang et al (11) did not find that pulp necrosis was a factor in tooth survival. Long-term studies examining the treatment outcomes of cracked teeth receiving orthograde root canal treatment in the United States do not exist. The purpose of the present study was to examine the distribution and 1-year treatment outcomes of cracked teeth receiving orthograde root canal treatment in 1 private endodontic practice over a 25-year period.
Materials and Methods The study was approved by the Institutional Review Board at the University of Iowa, Iowa City, IA. Study subjects were patients treated by 1 endodontist, and during the 25-year period, all patients were sent recall cards at 1 year, so there was at least an opportunity for 1year recall. The same endodontist provided the diagnosis, treatment, and recall examination over the study period. For each patient, name, tooth number, existing restoration, pulpal diagnosis, periapical diagnosis, and starting date and ending date of treatment were entered into a database. The location(s) of the crack and associated periodontal probing depths also were recorded. The categories of age and sex were added retrospectively in 2016 for patients whose records were still available. The following clinical tests and evaluations were performed on all teeth at the time of presentation and diagnosis: 1. 2. 3. 4.
Periapical radiograph Pulpal response to cold and/or hot Periapical response to pressure, palpation, and percussion Buccal and lingual periodontal probing depth recording in the mesial and distal interproximal spaces and furcas (directed precisely where marginal ridge cracks were identified to indicate the deepest probing of the crack) 5. Direct transillumination and visualization with and without magnification. The identified crack had to block light transmission and show a definite shadow with both buccal and lingual coronal light placement. Teeth not exhibiting a shadow were considered to have ‘‘crazings’’ and were not included in this analysis 6. Responses to biting on various cusps of the diagnosed tooth, with at least 1 cusp exhibiting pain to biting on either a Burlew wheel or Tooth Slooth (Professional Results, Inc, Laguna Niguel, CA). The endodontist’s instrumentation technique changed over the 25-year span as new technology was adapted. Ten years after beginning private practice, nickel-titanium instrumentation was incorporated into the debridement procedures of the endodontist. All teeth were filled using lateral condensation and Roth’s 801 sealer (Roth International, Chicago, IL). No teeth were included in this analysis that were not confirmed by direct visualization of the crack. Teeth diagnosed as cusp fractures, split teeth, and vertical root fractures also were excluded from this analysis (13). Restorations were removed only for patients with pulpal diagnoses who required root canal treatment. All patients who returned for the 1-year recall were evaluated for the presence or absence of symptoms, radiographic resolution of 2
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previous lesions, and the presence of a crown by the endodontist. Success of the root canal therapy was defined as the absence of signs or symptoms plus resolution of any previous radiographic pathosis. ‘‘Failure’’ was defined as the persistence of signs or symptoms with no change in the radiographic pathosis, enlarged radiographic pathosis, or the development of radiographic pathosis when there had been none previously. Questionable status was assigned when there was absence of signs and symptoms but failure of complete resolution of previous radiographic pathosis, even if there was a reduction in lesion size. All statistical analyses were conducted using SAS version 9.4 (SAS, Cary, NC). Univariate frequency distributions for all collected variables were evaluated. Because patients could have had more than 1 tooth treated during the study period, 1 tooth per patient was selected at random to avoid potentially correlated outcomes within patients (14). Bivariate associations were analyzed between explanatory variables and success of root canal therapy. Finally, the 3 variables deemed as most predictive of success in bivariate analyses were used to generate a ‘‘Cracked Tooth Prognostic Index’’ (also known as the ‘‘Iowa Index’’) for potential use by practitioners when informing patients about treatment options for cracked teeth.
Results Of the 3038 cracked teeth in the original database, 952 were excluded from the analysis because they represented multiple teeth from the same patient, leaving 1 tooth per patient in 2086 unique patients. Mandibular second molars (36%) had the highest incidence followed by the mandibular first molars (27%) for a total of 63% for all teeth. Figure 1 depicts the stratification of the 2086 teeth into 3 mutually exclusive subsets:
Diagnosed Cracked Teeth (n=2086)
Not treated with Root Canal Therapy (n=680)
Treated with Root Canal Therapy (n=1406)
Did not return for 12-month follow-up visit (n=1026)
Potentially Eligible for Bivariate Analysis (n=380) Ineligible for bivariate analysis (n=17): - Outcome “questionable” (n=13) - Patient <18 years old (n=1) - Wisdom tooth (n=1) - Reversible pulpitis (n=1) - Unknown size of restoration (n=1) Included in Bivariate Analysis (n=363)
Figure 1. Stratification of the 2086 teeth into 3 mutually exclusive subsets.
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Clinical Research 1. 680 teeth not treated with root canal therapy 2. 1026 teeth treated with root canal therapy but lost to follow-up 3. 380 teeth treated with root canal therapy and followed with a 12month recall examination Table 1 shows the presenting conditions of teeth in each of the 3 groups. P values are not presented in this table because most variables did not differ to a clinically meaningful degree among the 3 groups although teeth not treated with root canal therapy appeared more likely to have probing pocket depths $5 mm or to have had a pulpal diagnosis of reversible pulpitis. Of the 380 teeth eligible for further analyses, 17 were excluded, including 13 with a ‘‘questionable’’ outcome, 1 with reversible pulpitis, 1 with a missing value for restoration surfaces, 1 that was a wisdom tooth, and 1 in a patient under 18 years of age (Fig. 1). This left 363 nonwisdom teeth in adult patients, all with an initial pulpal diagnosis of irreversible pulpitis, necrosis, or previously treated and an outcome
of either ‘‘success’’ or ‘‘failure’’ at 12 months, which comprised the data set for the present analysis. Table 2 shows the results of bivariate analyses between the explanatory variables and 12-month success. A total of 296 teeth (82%) were classified as ‘‘successes,’’ with the 3 variables most predictive of failure being: 1. The presence of marginal ridge cracks (only 62% of teeth with cracks on both mesial and distal marginal ridges were successes) 2. Teeth with mesial or distal probing pocket depths $5 mm (ranging from 31%–39% success) 3. Periapical diagnosis of chronic apical periodontitis (CAP), suppurative apical periodontitis (SAP), or acute apical abscess (AAA), with only a 74% success rate in these teeth compared with an 85% success rate in teeth with periapical diagnosis of normal or acute apical periodontitis
TABLE 1. Percent of Teeth by Treatment and Follow-up (FU) Category Level
Overall (N = 2086)
Not RCT (n = 680)
RCT but lost to FU (n = 1026)
RCT and ollowed (n = 380)
18–44 45–54 55+ Missing Male Female #1996 1997–2005 $2006 Upper second molar Upper first molar Upper second premolar Upper first premolar Lower second molar Lower first molar Lower second premolar Lower first premolar Third molar Amalgam Composite Metal None Other/missing/temp 0 1 2 3 5 Yes No Yes No Yes No Missing Yes No Missing Reversible Irreversible Necrosis Previous Tx Normal AAP CAP SAP AAA
24 25 23 28 38 62 35 32 33 9 18 4 4 36 27 1 0 1 56 6 18 8 12 7 49 16 5 23 53 47 60 40 9 44 47 16 44 40 18 36 35 11 49 23 12 6 10
22 23 28 26 36 64 31 30 39 11 18 3 3 35 27 1 0 2 56 5 22 8 10 7 42 21 4 25 55 45 62 38 19 36 45 33 29 39 51 8 28 13 56 15 9 6 14
25 26 20 28 40 60 34 32 34 9 19 4 4 36 26 1 0 1 55 7 16 7 14 7 52 12 5 23 53 47 59 41 4 48 48 8 50 41 4 50 38 8 46 28 13 4 9
23 25 21 30 32 68 44 37 19 8 17 4 4 38 28 1 0 0 58 8 14 9 12 8 50 15 5 22 53 47 61 39 4 49 46 6 54 40 0 47 41 12 44 24 16 8 7
Variable Patient age (y)
Patient sex Date of treatment Tooth type
Restoration material
Restoration surfaces
Mesial MR crack Distal MR crack Mesial pocket $5 mm Distal pocket $5 mm Pulpal diagnosis
Periapical diagnosis
AAA, acute apical abscess; AAP, acute apical periodontitis; CAP, chronic apical periodontitis; MR, marginal ridge; RCT, root canal treatment; SAP, suppurative apical periodontitis; Tx, treatment.
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Clinical Research TABLE 2. Bivariate Associations between Presenting Characteristics and Endodontic Success Variable
Level
Number of patients
Number (%) of successes
P value
Total patient age (y)
NA 18–44 45–54 55+ Missing Male Female #1996 1997–2005 $2006 Lower first molar Upper first molar Upper second molar Lower second molar Premolar Amalgam Composite Metal None Other/missing/temp 0 1 2 3 5 Neither MMR only DMR only Both Missing (1–2) 3 4 $5 Missing (1–2) 3 4 $5 Irreversible Necrosis Previous Tx Normal/AAP CAP/SAP/AAA
363 86 89 76 112 117 246 162 134 67 101 61 27 142 32 210 28 49 30 46 30 185 51 18 79 1 141 166 55 165 168 14 16 147 170 23 23 178 142 43 256 107
296 (82) 72 (84) 80 (90) 58 (76) 86 (77) 91 (78) 205 (83) 129 (80) 115 (86) 52 (78) 88 (87) 51 (84) 22 (81) 111 (78) 24 (75) 169 (80) 23 (82) 40 (82) 25 (83) 39 (85) 25 (83) 151 (82) 41 (80) 14 (78) 65 (82) 1 (100) 128 (91) 133 (80) 34 (62) 132 (80) 146 (87) 13 (93) 5 (31) 133 (90) 140 (82) 14 (61) 9 (39) 151 (85) 113 (80) 32 (74) 217 (85) 79 (74)
NA .059
Patient sex Date of first visit Tooth type
Restoration material
Restoration surfaces
Marginal ridge cracks
Mesial pocket (mm)
Distal pocket (mm)
Pulpal diagnosis Periapical diagnosis
.202 .249 .373
.968
.989
<.001
<.001
<.001
.220 .014
AAA, acute apical abscess; AAP, acute apical periodontitis; CAP, chronic apical periodontitis; DMR, distal marginal ridge; MMR, mesial marginal ridge; NA, not applicable; SAP, suppurative apical periodontitis; Tx, treatment. Bold values indicate P values where P < .05 and are significant.
The patient’s age, sex, year of treatment, tooth type, restorative material present at the time of examination, and number of surfaces restored were not associated with treatment success. Finally, Figure 2 shows how the 3 factors that were most significant in the bivariate analyses were used to generate the following novel prognostic index for the success of orthograde root canal therapy in cracked teeth: 1. Iowa stage I = no probing pocket depths $5 mm and no crack across the distal marginal ridge (37% of teeth, 93% success) 2. Iowa stage II = no probing pocket depths $5 mm, having a crack across the distal marginal ridge, and not having a periapical diagnosis of CAP/SAP/AAA (39% of teeth, 84% success) 3. Iowa stage III = no probing pocket depths $5 mm, having a crack across the distal marginal ridge, and having a periapical diagnosis of CAP/SAP/AAA (15% of teeth, 69% success) 4. Iowa stage IV = $1 mesial or distal probing pocket depth $5 mm (8% of teeth, 41% success).
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Discussion To date, this is the largest and most lengthy data collection effort with regard to cracked teeth by a single practitioner, with data collection occurring between 1989 and 2015. There was an opportunity for a 1-year recall for all treated patients (N = 46,253) during that time. During this time period, the periapical diagnostic terminology changed. Periapical diagnostic terms that did not change included ‘‘normal’’ and ‘‘acute apical abscess.’’ Periapical terms that changed effective 2009 include ‘‘chronic apical periodontitis’’ to ‘‘asymptomatic apical periodontitis,’’ ‘‘acute apical periodontitis’’ to ‘‘symptomatic apical periodontitis,’’ and ‘‘suppurative apical periodontitis’’ to ‘‘chronic apical abscess’’ (15). Because the data collection was started well in advance of the most recent terminology changes, the older terminology is used here. In the present analysis, the overall distribution of teeth identified with cracks did not differ from that reported in other published studies. The mandibular second molar (36%) had the highest incidence
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Clinical Research Distal Marginal Ridge cracked?
No
Iowa Stage I: 37% of cases (93% success)
No
Iowa Stage II: 39% of cases (84% success)
Yes No Periapical Diagnosis CAP, SAP, or AAA?
Mesial or Distal Probing Pocket Depth ≥5 mm?
Yes
Yes
Iowa Stage III: 15% of cases (69% success)
Iowa Stage IV: 8% of cases (41% success)
Figure 2. Iowa Staging Index.
followed by the mandibular first molar (27%) for a total of 63% for the mandibular molars (3, 6, 8, 9, 16, 17). Older age was found to be marginally associated with a lower success rate (76% success in patients >55 years old vs 90% in those ages 45–54 years) although age was not available for many patients in this analysis, which would have lowered the statistical power available to detect differences. In other studies (18), the incidence of cracked teeth was found to increase with age. There were slightly more females than males seen for cracked teeth in this analysis, but this might have resulted from referral patterns of the local dentists. Success rates throughout the time period did not differ significantly. Success decreased with increasing pulpal involvement (85% for teeth with irreversible pulpitis, 80% for necrotic teeth, and 74% for previously treated teeth). Although these differences were not statistically significant, these findings are similar to those of Tan et al (19). Pulpal diagnosis of necrosis associated with tooth fracture has been a source of debate regarding root canal therapy versus extraction as the appropriate treatment recommendation. Berman and Kuttler (12) have argued that because of variability in outcomes, extraction should be recommended for cracked teeth with necrotic pulps and minimal restorations. This study would refute that modality as long as there are not probing pocket depths $5 mm and a crown is placed after root canal treatment. In the present analysis, the single most important factor related to failure was having a probing pocket depth $5 mm. This is similar to the findings of Tan et al (19), Kim et al (18), and Kang et al (11). The presence of a distal marginal ridge crack also conferred more risk of failure than mesial cracks. This has been supported by Hilton et al (20) in an analysis of data from the National Dental Practice–Based Research Network.
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In our opinion, the most important limitation of this study was not having a higher recall rate. All patients were offered a 1-year recall visit at no charge at the time treatment was completed, but despite that only 27% of treated patients returned for recall. Other long-term outcomes studies have had monetary incentives and have yielded recall rates of 50% (21), and an institutional outcomes study on cracked teeth had a 43% recall rate (22). Speculation as to why patients did not return could range from ‘‘they were asymptomatic and didn’t think they needed to come’’ to ‘‘the tooth was extracted,’’ so nonresponse bias, a bias common to most in vivo endodontic follow-up studies, could potentially have affected our results. The ultimate question that this study tried to answer was ‘‘What should providers tell patients who have cracked teeth that need root canal treatment about the endodontic prognosis they could expect if the tooth were treated by an endodontist?’’ The Iowa Staging Index is our initial attempt to address this question and is based on the findings described here. The earlier the diagnosis, the better the prognosis, as illustrated in 3 previous studies of cracked teeth with reversible pulpitis (8–10). When endodontic treatment is deemed necessary, the Iowa Staging Index presented here potentially could help with treatment decision making and the informed consent process. Ideally, before this index is used in clinical practice, it should be validated using prospective cohort designs in various private practice and institutional settings.
Conclusions In this analysis of 363 cracked teeth treated with orthograde root canal therapy by a single endodontist in private practice over a 25-year period, 296 (82%) were deemed to be ‘‘successes’’ at the 1-year recall examination with the factors most associated with failure being the
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Clinical Research presence of 1 probing pocket depth $5 mm; presence of a crack across the distal marginal ridge; and periapical diagnosis of CAP, SAP, or AAA. Results suggest that cracked teeth provided with root canal treatment can have prognoses that can result in higher success rates than previously reported.
Acknowledgments The authors deny any conflicts of interest related to this study.
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10. Opdam NJ, Roeters JJ, Loomans BA, Bronkhorst EM. Seven-year clinical evaluation of painful cracked teeth restored with a direct composite restoration. J Endod 2008; 34:808–11. 11. Kang SH, Kim BS, Kim Y. Cracked teeth: distribution, characteristics, and survival after root canal treatment. J Endod 2016;42:557–62. 12. Berman LH, Kuttler S. Fracture necrosis: diagnosis, prognosis assessment, and treatment recommendations. J Endod 2010;36:442–6. 13. Rivera EM, Walton RE. Longitudinal fractures. In: Torabinejad M, Walton RE, eds. Principles and Practice of Endodontics, 4th ed. Philadelphia: Saunders; 2009: 108–28. 14. Caplan DJ, Slade GD, Gansky SA. Complex sampling: implications for data analysis. J Public Health Dent 1999;59:52–9. 15. Gutmann JL, Baumgartner JC, Gluskin AH, et al. Identify and define all diagnostic terms for periapical/periradicular health and disease states. J Endod 2009;35: 1658–74. 16. Hiatt WH. Incomplete crown-root fracture in pulpal-periodontal disease. J Periodontol 1973;44:369–79. 17. Cameron CE. The cracked tooth syndrome: additional findings. J Am Dent Assoc 1976;93:971–5. 18. Kim SY, Kim SH, Cho SB, et al. Different treatment protocols for different pulpal and periapical diagnoses of 72 cracked teeth. J Endod 2013;39: 449–52. 19. Tan L, Chen NN, Poon CY, Wong HB. Survival of root filled cracked teeth in a tertiary institution. Int Endod J 2006;39:886–9. 20. Hilton TJ, Funkhouser E, Ferracane JL, et al. Correlation between symptoms and external characteristics of cracked teeth: findings from The National Dental Practice-Based Research Network. J Am Dent Assoc 2017;148: 246–2561. 21. Marquis VL, Dao T, Farzaneh M, et al. Treatment outcome in endodontics: the Toronto Study. Phase III: initial treatment. J Endod 2006;32:299–306. 22. Sim IG, Lim TS, Krishnaswamy G, Chen NN. Decision making for retention of endodontically treated posterior cracked teeth: a 5-year follow-up study. J Endod 2016;42:225–9.
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