Clinical Research

Outcome of Orthograde Retreatment after FailedApicoectomy: Use of a Mineral Trioxide AggregateApical PlugJohannes Mente, Priv-Doz, Dr med dent,* Meltem Leo, Dr med dent,*

Annemarie Michel, Dr med dent,* Holger Gehrig, Dr med dent, MSc,* Daniel Saure, MSc,†

and Thorsten Pfefferle, Dr med dent*

Abstract

Introduction: This controlled, single-center historiccohort study project evaluates treatment outcomes of anonsurgical treatment approach after failed apicoectomy.Methods: The treatment outcomes of nonsurgical re-treatment after a failed apicoectomywere evaluated clin-ically and radiographically. The study cohort consisted ofteeth that had received primary root canal treatment andsubsequent apicoectomy elsewhere before the patientspresented with post-treatment disease. Orthograde re-treatment and obturation using an apical mineral trioxideaggregate plug was performed by postgraduate studentsand endodontic specialists in 25 cases between 2004 and2012. Pre-, intra-, and postoperative information and thepotential effect on the retreatment outcome were evalu-ated and statistically analyzed using the chi-square test.Results: Twenty-two patients with 23 teeth attendedthe follow-up examinations (recall rate = 92%). Thefollow-up periods ranged from 12 to 102 months(median = 35 months). Twenty teeth (87%) were classi-fied as ‘‘success,’’ and 3 teeth were considered (17%)‘‘failure.’’ The chi-square test confirmed that the preoper-ative factor ‘‘number of roots’’ had a statistically signifi-cant effect on treatment outcome (odds ratio = 0.08;95% confidence interval, 0–1.76; P = .03). The factor‘‘tooth location’’ was of borderline significance (odds ra-tio = 0.1; 95% confidence interval, 0–2.14; P = .05).Conclusions: The results of the present study suggestthat orthograde retreatment combined with orthogradeplacement of an apical mineral trioxide aggregate plugis a promising long-term treatment option for teethwith postsurgical pathosis. The success rates were higherfor single-rooted teeth. The use of cone-beam computedtomographic imaging in cases of inconclusive periapicalradiographs is recommended to minimize the risk ofmisinterpretation when assessing treatment outcome.(J Endod 2015;41:613–620)

From the *Division of Endodontics and Dental TraumatologyRuprecht-Karls-University of Heidelberg, Heidelberg, Germany.

Address requests for reprints to Dr Johannes Mente, Division ofHeidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany0099-2399/$ - see front matter

Copyright ª 2015 American Association of Endodontists.http://dx.doi.org/10.1016/j.joen.2015.01.002

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Key WordsFailed apicoectomy, mineral trioxide aggregate, orthograde retreatment, treatmentoutcome

Apical surgery is a valuable treatment option to maintain a tooth with persistent post-treatment apical periodontitis (1–3), but there is an evidence-based rationale for

when to perform this procedure. Regardless of the clinical performance, root-end resec-tion cannot compensate for poor orthograde endodontic treatment (4). In a retrospec-tive evaluation, Abramovitz et al (5) found that only 45%of the teeth that were referred forapical surgery were adequately selected. In addition, 83%of the teeth from this evaluationwere found to be inadequately obturated and required nonsurgical retreatment instead ofapical surgery. Thus, teeth that present with postsurgical pathosis often lack properorthograde endodontic treatment. In these cases, surgical retreatment with a traditionaltechnique is unlikely to be successful (6, 7). The first clinical results regarding thetreatment outcome after microresurgery are promising. However, the number ofcases is rather small, and the observation periods are relatively short (8). After failedprimary root canal treatment, orthograde retreatment should always be considered firstinstead of apical surgery (3, 9, 10). When a patient presents with post-treatment diseasein a tooth in which apicosurgery had already been performed instead of orthograde re-treatment, the endodontist must still come up with a treatment plan.

However, current data regarding the treatment outcome of nonsurgical retreat-ment after failed apicoectomy are limited. There are only a small number of case reportsthat describe a nonsurgical treatment approach after failed apicoectomy. The first stepis the complete removal of the root canal filling material and adequate cleaning andshaping of the root canal system. Next, the root canal is obturated by orthograde place-ment of an apical mineral trioxide aggregate (MTA) plug (11–13). Despite the low levelof evidence from case series based on the criteria of the Centre for Evidence-BasedMed-icine, Oxford, England (14), the reported treatment outcome appears favorable. Thus,it is important to further evaluate the clinical data regarding this treatment option.

The present study is part of a recently published clinical trial (15). The treatmentoutcome of MTA in open apex teeth was evaluated based on clinical and radiographicfindings. In contrast to the clinical trial published in 2013, in the present study, the onlyreason for the open apex was apicoectomy. Primary root canal treatment and apicoec-tomy had been completed elsewhere before these patients presented with post-treatment disease at the Division of Endodontics, University Hospital of Heidelberg,Heidelberg, Germany. Usually, the former treatment providers have only offered the

, Department of Conservative Dentistry and †Institute of Medical Biometry and Informatics,

Endodontics and Dental Traumatology, Department of Conservative Dentistry, University Hospital. E-mail address: johannes.mente@med.uni-heidelberg.de

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Clinical Research

extraction of the tooth as causal therapy after the surgical interventionhad failed. In every case, the existing root canal filling was radiograph-ically evaluated to be inadequate.

Orthograde retreatment and obturation using an apical MTA plugwere performed in all cases. The radiographic treatment outcome wasrecorded based on the well-established criteria described by Rud et al(16) and Molven et al (17). In addition, cone-beam computed tomo-graphic (CBCT) imaging was used as a diagnostic tool in uncertaincases.

The first aim of this clinical study was to systematically assess the 1-to 5-year treatment outcomes in teeth that had undergone orthograderetreatment and reobturation withMTA apical plugs after failed apicoec-tomy. The second aim of this study was to investigate the association ofpotential prognostic factors with the treatment outcome of this nonsur-gical treatment approach for teeth that present with post-treatment dis-ease after the apicoectomy has already been performed.

Materials and MethodsThe study protocol of this historical cohort study was approved by

the Ethics Committee of the University of Heidelberg (ref. 095/2010).The participants were recruited from among the patients of the Depart-ment of Conservative Dentistry, University Hospital of Heidelberg.Patients who had undergone nonsurgical retreatment after failed api-coectomy between November 2003 and June 2012 were selected forpotential inclusion.

Inclusion and Exclusion CriteriaSubjects were selected from among the patients who presented

with signs and symptoms after the apicoectomy had been performedelsewhere. Because the existing root canal filling was radiographicallyevaluated to be inadequate in every case included in the study, all pa-tients underwent nonsurgical retreatment followed by orthogradeplacement of an apical MTA plug. The study sample was confined toteeth with a follow-up period of at least 12 months. A tolerance of14 days was accepted. A compromised immune status or pregnancyat the time of follow-up resulted in exclusion from the study. Caseswith missing pre- and intraoperative information were excluded fromthe study. Any tooth diagnosed with either a longitudinal root fractureor a periodontal-endodontic lesion on the day of the nonsurgical re-treatment was excluded from the study.

Recruitment of PatientsThe recruitment of patients has been previously described in detail

(15). Briefly, patients who met the previously mentioned inclusioncriteria were contacted and invited to attend the follow-up examina-tions. The potential participants received detailed information aboutthe study. Clinical and radiographic follow-up examinations were per-formed only after written informed consent had been given.

Endodontic Treatment InterventionThe treatment providers were either postgraduate students or end-

odontic specialists. A dental operating microscope (Zeiss, Oberkochen,Germany) was used during the entire root canal treatment in every case.A rubber damwas applied, and the access cavity was then prepared. Theroot canal filling material was removed using nickel-titanium rotary in-struments or hand files. The treatment providers were free to choosefrom various types of endodontic files. The following nickel titanium ro-tary instruments were available for use: Flex Master and Reciproc files(VDW, Munich, Germany), ProTaper retreatment files (Dentsply Mail-lefer, Ballaigues, Switzerland), and GT rotary files (Dentsply Maillefer).The following hand files were available for use: nickel-titanium

614 Mente et al.

Hedstr€om files and nickel titanium K-type files (Brasseler, Lemgo, Ger-many), stainless steel Hedstr€om files and K-type files (VDW), and GThand instruments (Dentsply Maillefer). When necessary, posts werecarefully removed using ultrasound vibration (P5 XS; Acteon Group,M�erignac Cedex, France). There were no complications, such as rootperforation or instrument fracture, during the retreatments. The work-ing length was established with the aid of an apex locator (Raypex 4,VDW) and was confirmed radiographically. The root canals were inter-mittently irrigated with ultrasonically activated 3% sodium hypochlorite(Hedinger GmbH, Stuttgart, Germany) and 2% chlorhexidine (Engel-hard Arzneimittel GmbH, Niederdorfelden, Germany) using a 27-Gneedle (Transcoject, Neum€unster, Germany).

When switching from sodium hypochlorite to chlorhexidine orvice versa, root canals were irrigated with ethyl alcohol to prevent theprecipitate formation of parachloroaniline. After completion of root ca-nal instrumentation, the canals were irrigated with the EDTA containingSmear Clear (Sybron Endo, Orange, CA) for 60 seconds. The canalswere finally flushed with chlorhexidine and dried with sterile paperpoints (VDW). The nonsurgical retreatment was performed in 1 or mul-tiple sessions. In cases of multiple sessions, calcium hydroxide powderwas mixed with chlorhexidine to form a pasty consistency, and the pastewas applied with a Lentulo spiral (VDW) to form the intracanal dressing.The access cavities were temporarily sealed with zinc oxide–eugenolcement (IRM; Dentsply, Konstanz, Germany).

Orthograde Obturation and Application of Apical MTAPlug. Small portions of MTA were inserted with an MTA delivery car-rier (Dentsply Maillefer) and compacted apically with Machtou plug-gers of sizes 0, ½, and 3/4 (Dentsply Maillefer). The minimumthickness of the apical MTA plug was 4 mm. The correct position andthe adequate extent of the apical MTA plug were confirmed radiograph-ically. If the MTA plug was poorly placed and was too short or exhibitedvoids, then the MTA was removed with a small ultrasonic tip (S 25, Ac-teon Group) coupled with irrigation and subsequently replaced.

The residual root canal space was backfilled immediately afterplacement of the MTA plug. It was filled with injectable gutta-percha(Obtura III; Obtura Spartan, Fenton, MO) and AH Plus sealer (Dents-ply) with ProRoot MTA (Dentsply Maillefer) or with bonded compositeresin (Tetric EvoCeram bleach; Vivadent, Schaan, Lichtenstein). Aftercompletion of the root canal filling, the access cavities were sealedwith composite resin (Tetric Ceram, Vivadent). Post-treatment radio-graphs were taken immediately using the parallel technique with anRWT film holder (KKD GmbH, Ellwangen, Germany) and30 � 40 mm ISO classification E dental film (Kodak Ekta-SpeedPlus; Carestream Health Inc, New York, NY).

Pre- and Intraoperative DataThe acquisition of pre- and intraoperative information from the

patients’ records and data entry into a specifically designed databasespreadsheet were previously described in detail (15).

CalibrationClinical Calibration. Given the high interexaminer reliabilityachieved during the calibration process in phase 1 of the present study(18), we simplified the clinical calibration process for further similarstudy projects. The clinical calibration was performed using studymodels (A1 and B1; KaVo, Biberach Germany). The step-by-step proce-dure of this clinical calibration has recently been described in detail(19).

Radiographic Calibration. Radiographs were independently in-terpreted by 2 experienced endodontists using the criteria and classifi-cation described by Rud et al (16) and Molven et al (17). Before the

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TABLE 1. Outcome Distribution by Preoperative Factors and Estimated Relative Rates of Success

Factor

Teeth Healed Disease

P value* OR† (95% CI)n % n % N %

Age .33 2.48 (0.1–56.18)#45 y 18 78 15 83 3 17>45 y 5 22 5 100 — 0

Sex .83 1.33 (0.1–17.29)Female 14 61 12 86 2 14Male 9 49 8 89 1 11

No. of roots .03 0.08 (0–1.76)1 13 57 13 100 — 0$2 10 43 7 70 3 30

Tooth type .27 0.32 (0.01–7.11)Anterior 6 26 6 100 — 0Posterior 17 74 14 82 3 18

Tooth location .05 0.1 (0–2.14)Maxilla 12 52 12 100 — 0Mandible 11 48 8 73 3 27

Signs or symptoms (preoperative) .59 2Absent 12 52 10 83 2 17 (0.15–25.76)Present 11 48 10 91 1 9

Apical periodontitis (preoperative) .57 1.06Absent 2 9 2 100 — 0 (0.06–18.01)Present 21 91 18 86 3 14

CI, confidence interval; OR, odds ratio.

Numbers in parentheses denote the lower and upper limits of the 95% CI. Bold denotes statistical significance at a 5% confidence level. Healing classification according to Rud et al (16); in cases in which

radiographic findings at follow-up were unclear, outcome was assessed using cone-beam computed tomographic imaging.

*Chi-square test.†Mantel-Haenszel odds ratio (the logit estimator was used if a cell contains a zero).

Clinical Research

interpretation of the study radiographs, both examiners assessedsample radiographs using the schematic depiction of different healingcategories published by Molven et al (17). The procedure has been pre-viously described elsewhere (2). The interexaminer agreement wascomputed according to Rud et al (16) and Molven et al (17).

Follow-up ExaminationTwo calibrated examiners (M.L. and T.P.) performed the follow-

up examinations at least 12 and up to 109 months after treatment. Adetailed description of the follow-up examination was previously pub-lished (15).

Outcome AssessmentThe treatment outcome was evaluated based on clinical and radio-

graphic findings. Periapical radiographs were taken using the paralleltechnique to ensure high reproducibility. The preoperative and follow-up radiographs were assessed independently and in a random sequenceby 2 experienced endodontists (T.P. and J.M.). All radiographs wereviewed in a darkened room using an illuminated viewer box (Kentzler-Kaschner Dental GmbH, Ellwangen, Germany) with 2� magnification.

Any radiographically visible pathological changes, such as persis-tence and recurrence of radiolucent lesions, root resorption, and apicalextrusion of MTA, were recorded. Postoperative periapical healing wasassessed radiographically using the well-established classification intro-duced by Rud et al (16) and Molven et al (17). The classification dis-tinguishes between the following 4 groups of healing:

1. Complete healing2. Incomplete healing (scar tissue)3. Uncertain healing4. Unsatisfactory healing

The treatment outcomes were recorded as ‘‘success’’ in cases of‘‘complete healing’’ or ‘‘incomplete healing (scar tissue)’’ (20).Furthermore, the tooth had to be free of clinical signs or symptoms

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and had to remain functional. The treatment outcome was recordedas ‘‘failure’’ in cases of ‘‘uncertain healing’’ or ‘‘unsatisfactory healing.’’If a tooth presented with clinical signs or symptoms or if it had lost func-tionality, then the treatment outcome was also recorded as ‘‘failure.’’

In cases of interobserver disagreement regarding the radiographicinterpretation, the 2 examiners discussed their findings and reached aconsensus. To minimize the risk of misinterpretation in cases in whichthe periapical radiographs were difficult to interpret, the periapical sit-uation was also assessed by CBCT imaging. The results of this additionaladvanced 3-dimensional imaging method were then used to decide be-tween ‘‘success’’ and ‘‘failure.’’

CBCT scans were obtained with the Veraviewepocs 3D (J MoritaMfg Corp, Kyoto, Japan). The imaging settings were as follows: smallfield of view (40 � 40 mm), high resolution (0.125-mm voxels),80 kV, and 7 mA. The CBCT images were viewed with i-dixel software(J Morita). Two experienced observers (H.G. and J.M.) evaluated theCBCT images independently.

Statistical AnalysisThe interexaminer agreement regarding radiographic examina-

tion was quantified using the Kappa-Cohen test. The median, first andthird quartile, minimum and maximum, and relative and absolute fre-quencies were calculated for descriptive analyses. The chi-square testwas applied to investigate the effect of potential outcome predictors.The data were analyzed using the SAS statistical package (Version9.3; SAS Institute Inc, Cary, NC). There were no adjustments madefor multiple testing because of the exploratory nature of the study. Alltests were performed at a significance level of 0.05.

ResultsCalibration Process

The clinical calibration resulted in a high level of consensus withthe ‘‘authorized measurements.’’ There were 1008 measurements ofprobing depths and 144 measurements of furcation involvement

Orthograde Retreatment after Failed Apicoectomy 615

TABLE 2. Outcome Distribution by Intraoperative Factors and Estimated Relative Rates of Success

Factor

Teeth Healed Disease

P value* OR† (95% CI)n % n % n %

Treatment sessions for whole endodontic treatment .83 0.75 (0.05–9.72)#2 9 39 8 89 1 11>2 14 61 12 86 2 14

Root canal backfill technique coronal to MTA plug .73 1.27 (0.03–41.56)Lateral compaction — — — — — —Warm vertical compaction 11 48 9 82 2 18Pure MTA filling 2 9 2 100 — 0MTA plug + composite filling 10 43 9 90 1 10

Extruded MTA .59 0.5 (0.03–6.44)Absent 11 48 10 91 1 9Present 12 52 10 83 2 17

Treatment provider .46 1.9 (0.08–44.16)Postgraduate student 19 83 16 84 3 16Specialist 4 17 4 100 0 0

CI, confidence interval; OR, odds ratio.

Numbers in parentheses denote the lower and upper limits of the 95% CI. Healing classification according to Rud et al (16); in cases in which radiographic findings at follow-up were unclear, outcome was

assessed using cone-beam computed tomographic imaging.

*Chi-square test.†Mantel-Haenszel odds ratio (the logit estimator was used if a cell contains a 0).

Clinical Research

reviewed by each examiner and statistically analyzed for concordancewith the ‘‘authorized measurements.’’ The interexaminer agreementregarding probing depth measurements was 95% and 96%, respec-tively. The interexaminer agreement regarding the assessment of furca-tion involvement was 93% for both examiners. The intraexaminerreliability regarding probing depth measurements was 96.5% and98%, respectively. The intraexaminer reliability regarding furcationinvolvement measurements was 91.5% for both examiners. The radio-graphic calibration according to revealed ‘‘substantial agreement’’ (21)was k = 0.774.

Study GroupTwenty-four patients were initially identified for potential inclusion

in the study. There were 22 patients with a total of 23 teeth in the follow-up examinations. The time of follow-up ranged from 12 to 102 months(median = 35 months, 92% recall rate). The patient ages ranged from

TABLE 3. Outcome Distribution by Postoperative Factors and Estimated Relative R

Factor

Teeth

N %

Quality of coronal restoration after retreatment‡§

Acceptable 21 9Unacceptable 1 4Unknown (tooth extracted) 1 4

Type of coronal restoration after retreatment‡

Composite filling 5 2Crown and access cavity sealed with composite filling 12 5Crown or partial crown 5 2Unknown (tooth extracted) 1 4

Post or screw after retreatment‡

Absent 20 8Present/Post 2 9Unknown (tooth extracted) 1 4

CI, confidence interval; OR, odds ratio.

Numbers in parentheses denote the lower and upper limits of the 95% CI. Healing classification according

assessed using cone-beam computed tomographic imaging.

*Chi-square test.†Mantel-Haenszel odds ratio (the logit estimator was used if a cell contains a zero).‡One missing value because 1 tooth was extracted elsewhere before follow-up.§Based on radiographic and clinical assessment.

616 Mente et al.

23–60 years, and themedian age was 36 years (first quartile = 30 years,third quartile = 44 years). The reasons for study dropout were re-corded, and there were 2 patients (8%) who refused to participate inthe recall.

The reasons why patients had been referred to the Division of End-odontics, University Hospital of Heidelberg and why nonsurgical ortho-grade retreatment after failed apicoectomy was considered were asfollows: a persistent or increasing periapical lesion of more than1 year after apicoectomy (21/23 teeth, 91%); clinical signs and symp-toms 11 and 98 months after an apicoectomy, respectively (2/23 teeth,9%); and persistent or increasing periapical radiolucency combinedwith clinical signs and symptoms (9/23 teeth, 39%).

Success RateThe treatment outcome relative to recorded pre-, intra-, and post-

operative variables is shown in Tables 1–3. There were 20 teeth (87%)

ates of Success

Healed Disease

P value* OR† (95% CI)n % N %

.75 0.38 (0.01–12.25)2 19 90 2 10

1 100 — 0— 0 1 100

.51 0.69 (0.02–20.03)2 5 100 — 02 11 92 1 82 4 80 1 20

— 0 1 100.56 1 (0.03–25.69)

7 17 85 3 152 100 — 0— 0 1 100

to Rud et al (16); in cases in which radiographic findings at follow-up were unclear, outcome was

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Figure 1. A mandibular first molar was radiographically recorded as a ‘‘failure’’ 5 years after orthograde retreatment and placement of apical MTA plugs. (A) Apreoperative radiograph 7.5 years after apicoectomy showing persistent apical radiolucency. (B) A follow-up radiograph 5 years after orthograde retreatment andplacement of apical MTA plugs. (C) A sagittal CBCT view at the 5-year follow-up. (D) A coronal CBCT view at the 5-year follow-up (distal root). Images C and Ddisplay persisting periapical pathosis.

Clinical Research

classified as ‘‘success’’ and 3 teeth (13%) classified as ‘‘failure.’’ Onetooth had been extracted at the time of follow-up because the patientpresented with persistent clinical signs and symptoms 4 months afternonsurgical retreatment. One tooth was extracted because of a symp-tomatic longitudinal root fracture 21 months after nonsurgical retreat-ment. The third failed tooth showed decreased, albeit still present,periapical radiolucency 5 years after nonsurgical retreatment. TheCBCT analysis confirmed the persistent periapical lesion in this case(Fig. 1B–D).

Influence of Potential Prognostic FactorsWe identified 2 preoperative variables that were associated with

higher healing rates. The success rates were higher in anterior (6/6teeth healed, 100%) than in posterior teeth (14/17 teeth healed,82%). Additionally, the healing rates of single-rooted teeth (13/13 teethhealed, 100%) were higher than those of multirooted teeth (7/10 teethhealed, 70%). The healing rates differed by more than 15% with regardto 2 intraoperative factors (root canal backfill technique coronal toMTA plug and experience of treatment provider). The data aredescribed in detail in Table 2. Postoperatively, only the type of restora-tion was associated with notable differences in treatment outcome(Table 3). The chi-square test found that ‘‘number of roots’’ was a sta-tistically significant influence on treatment outcome (odds ratio

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[OR] = 0.08; 95% confidence interval [CI], 0–1.76; P = .03). The var-iable ‘‘tooth location’’ was borderline between significant and not signif-icant (OR = 0.1; 95% CI, 0–2.14; P = .05). Because of the relativelysmall sample size, a multivariate analysis was not performed.

DiscussionThis single-center, historic cohort study project is part of a

recently published clinical trial (15). In this study, clinical interven-tions were assessed retrospectively, whereas treatment outcome wasassessed prospectively. The treatment outcomes of nonsurgical re-treatment after failed apicoectomies that were reobturated by ortho-grade placement of MTA apical plugs were evaluated independently bycalibrated examiners. The patient follow-up periods ranged from 12to 102 months after treatment. The radiographic evidence of periap-ical healing requires a follow-up period of at least 1 year (22, 23).Longer follow-up periods are particularly important in the case ofpersistent lesions after surgical endodontic treatment (24). These re-quirements were met with the relatively long follow-up periods in thisstudy. Despite the low number of cases, the high recall rate of 92%increases the level of evidence (25, 26).

The treatment outcome was successful in 86% of the cases(Table 1). This result compares with the success rates reported for con-ventional orthograde root canal retreatment of previously nonsurgically

Orthograde Retreatment after Failed Apicoectomy 617

Figure 2. A mandibular first molar recorded as a ‘‘success’’ 4.5 years after orthograde retreatment and placement of apical MTA plugs. (A) A preoperative radio-graph 7 months after apicoectomy showing persistent apical radiolucency. (B) A follow-up radiograph 4.5 years after orthograde retreatment and placement ofapical MTA plugs. (C) A sagittal CBCT view at the 55-month follow-up. (D) A coronal CBCT view at the 55-month follow-up (distal root). Images C and D displaycomplete bone repair although the bone bordering the apical area still does not consistently have the same density as the surrounding bone.

Clinical Research

treated teeth (3, 9, 10) and is superior to the healing rates reported forsurgical retreatment using a traditional technique (6, 7). In addition,these results are slightly below the healing rates for endodonticmicroresurgery of teeth with post-treatment disease (8).

Data of the present study suggest that the decision for endodonticsurgery is sometimes made independent of the factors responsible forpostendodontic apical periodontitis. The presence of persistentcontamination of the root canal system because of coronal or apicalleakage (27, 28), untreated root canals (29), inadequate root canaldisinfection during primary root canal treatment (30), and poor qualityof the root canal filling (31, 32) respond very well to conventionalorthograde retreatment (3, 9). Thus, after failed primary root canaltreatment, orthograde retreatment should always be considered firstand ideally performed by an endodontist using a dental operatingmicroscope (3). The majority of teeth treated in this manner wouldhave been healed without additional therapy (9, 10). However, apicalsurgery is still performed ignoring the factors that lead to apicalpathosis in the first place. Importantly, clinicians might be able tooffer these patients a reasonable treatment approach in addition toextraction. The statistical analysis in this study identified 1 outcomefactor (ie, ‘‘number of roots’’ [OR = 0.08; 95% CI, 0–1.76;P = .03]) out of all of the potential prognostic factors evaluated

618 Mente et al.

within this study (Tables 1–3). All failures occurred in multirootedteeth (Table 1). This result was consistent with findings obtained byother studies that showed worse healing rates for multirooted teeth(33, 34). The root canal system of multirooted teeth is generallymore complex than in single-rooted teeth (35), which may accountfor the difference in success rates.

The potential prognostic factor ‘‘tooth location’’ was of borderlinesignificance (OR = 0.1; 95% CI, 0–2.14; P = .05) and should be re-evaluated in further clinical studies with a larger sample size. The ‘‘api-cal extrusion of MTA’’ did not negatively affect treatment outcome(OR = 0.59; 95% CI, 0.03–6.44; P = .5). MTA is a material suitedfor areas in which there is a physical communication between theroot canal system and the periodontium (15, 19, 36, 37). MTA setsin moist environments, including blood (38, 39). This materialshows excellent sealing properties (40–42). Given the favorablecharacteristics of MTA, it is not surprising that the ‘‘apical extrusionof MTA’’ did not significantly affect treatment outcome.

When recording treatment outcome, all examiners should be cali-brated clinically and radiographically before the examinations (26).Outcome in endodontics should always be assessed using a combina-tion of clinical and radiographic findings. The radiographic appearanceof teeth after periapical surgery differs somewhat from teeth after

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Figure 3. A maxillary premolar recorded as a ‘‘success’’ 45 months after orthograde retreatment and placement of apical MTA plugs. (A) A preoperative radio-graph more than 10 years after apicoectomy showing persistent apical radiolucency and the coronal restoration was insufficient. (B) A follow-up radiograph16 months after orthograde retreatment and placement of apical MTA plugs; only small defects can be identified in the lamina dura adjacent to the apically extrudedMTA. (C) A follow-up radiograph 45 months after orthograde retreatment and placement of apical MTA plugs; complete bone repair with regeneration of theperiodontal space to a normal width around the apex and extruded MTA.

Clinical Research

nonsurgical endodontic treatment. Thus, periapical radiographs werenot interpreted using the periapical index (PAI) (43). The examinersused the well-established radiographic classifications of Rud et al(16) and Molven et al (17), which are particularly suited forassessing periapical healing after endodontic surgery (2, 44–48).

The authors suspect that the additional evaluation of periapical tis-sues by CBCT in cases of inconclusive periapical radiographs resulted inless misinterpretations concerning periapical healing. CBCT images areknown to show periapical bone loss as a sign of apical pathosis moreaccurately than periapical radiographs (49–53).

In the present study, several cases exemplify the diagnosticvalue of CBCT imaging in detecting periapical pathosis. A mandib-ular first molar 7.5 years after apicoectomy is shown in Figure 1A.Radiographically, periapical pathosis is evident both on the mesialand distal root. The follow-up radiograph 5 years after the ortho-grade retreatment showed a substantial reduction in periapicalradiolucency (Fig. 1B) compared with the preoperative radiograph(Fig. 1A). The examiners found that the periapical radiographs didnot provide sufficient data to determine whether the tooth shouldbe classified as a ‘‘success’’ or ‘‘failure.’’ Periapical pathosis is ex-pected to resolve within 4 to 5 years after treatment (20). Thus, itwas particularly important to accurately assess treatment outcome.The CBCT images revealed persisting periapical pathosis (Fig. 1Cand D). The usefulness of additional CBCT imaging can also beseen in another case, which is shown in Figure 2A–D. A mandib-ular first molar before and 4.5 years after orthograde retreatmentis shown in Figure 2A and B. The follow-up radiograph shows thatthe bone bordering the periapical area is less dense than the sur-rounding bone. The 3-dimensional assessment of periapical tissueconfirmed complete periapical healing with bone tissue present indirect contact with the resected root tips (Fig. 2C and D). Althoughthe bone bordering the apical area still does not consistently havethe same radiopacity as the surrounding bone that was not involvedin the apical surgery, this case would still be considered a ‘‘suc-cess.’’ In contrast, CBCT imaging was not considered necessaryin the case presented in Figure 3. The preoperatively existing peri-apical pathosis is radiographically visible (Fig. 3A). In addition, the

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patient reported that he had felt pain originating from this tooth.Furthermore, a fracture of the distal part of the coronal restorationwas evident before orthograde retreatment was performed. Thefollow-up radiograph 16 months after orthograde retreatment stillshowed small defects in the lamina dura adjacent to notableamounts of apically extruded root MTA (Fig. 3B). After 45 months,complete regeneration of the periodontal ligament space aroundthe resected root tip and the extruded MTA was visible(Fig. 3C). In this case, additional CBCT imaging was not consid-ered necessary to confirm complete healing of the periapical tis-sues. Despite the advantages of CBCT images in assessingperiapical pathosis, the general use of CBCT scans instead of orin combination with periapical radiographs cannot be recommen-ded. Because of the comparatively high radiation dose (54), therisks might outweigh the benefits. The authors advise using CBCTimaging when the periapical status cannot be clearly assessed using2-dimensional periapical radiography.

ConclusionsThe results of the present study indicate that orthograde nonsur-

gical retreatment after failed apicoectomy may present a treatment op-tion with favorable prognosis if the orthograde revision is performedusing a dental operating microscope and orthograde inserted MTA api-cal plugs are used for reobturation. The authors recommend the use ofCBCT imaging in cases of inconclusive periapical radiographs to mini-mize the risk of misinterpretation when assessing treatment outcome.

Despite the promising results reported in the present study, furtherclinical research is necessary to confirm the reported success rates andto clarify the effect of potential factors on treatment outcome.

AcknowledgmentsThe authors thank Mrs Joanna Voerste for linguistic support,

Mrs Kirsten Stoik for assistance in preparation of the figures, andMrs Ingrid Mente and Mr Marc Ohle for their valuable contributionto this study.

The authors deny any conflicts of interest related to this study.

Orthograde Retreatment after Failed Apicoectomy 619

Clinical Research

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JOE — Volume 41, Number 5, May 2015