Intemational Endodontic Journal (1994) 27, 75-8]

Retreatment or radiographic monitoring io endodonticsJ.-P, VAN NIEUWENHUYSEN, M, AOUAR & W, D'HOORE*Department of Dental Medicine and Stomatology, and 'Department of Hospital Administration, Catholic University of

Loiivain, Belgium

Summary

The aim of this clinical study was to assess 1032endodontically treated roots in relation to; (i) thesuccess rate of retreatment (612 roots)—only casesthat had recall examinations of 6 months or longerwere evaluated; (it) the influence of various factors onthe technical and clinical results of the retreatment;and (Hi) the consequences of radiographic monitoringof 420 asymptomatic roots when the root tilling wasradiographically deflcient (short, overextended and/orpermeable root fillings).

Technical assessment of the retreatment showed thatthe root was adequately sealed in 52.3% of cases, theroot filling was improved in 33,8%, was identical withthe initial treatment in 11,1% and was worse than thefirst treatment in 2.8% of the canals. Clinical assess-ment of the retreatment of symptomatic roots showedthat 71.8% of the retreatments were judged sticcessftil,18,9% showed some healing and 9.3% had failed. Theinitial size of the periapical lesion, the use of rubberdam, the root filling technique and the apical level ofthe root filling had a statistically significant influenceon the result of the retreatment.

Monitoring radiographically (median time span 6years) led to maintenance of the status quo in 94.8% ofcases, healing in 2.4% and failure in 2.8% of thecanals. Retreatment is clearly indicated when peri-apical radiolucency, clinical signs and/or symptoms arepresent with relative success of up to 91%. When no orlittle radiographic evidence of periapical pathology waspresent, when dinical signs and symptoms were absentor when the root filing was radiographically deficient,radiographic monitoring led to complications in only alimited number of cases,

Kegwords.-clinical decision, endodontic retreatment,radiographic evaluation.

Correspondence: Dr J.-P. Van Nieuwenhuysen, Catholic University ofLouvain, Department of Dental Medicine and Stomatology, AvenueHippocrate 15, 1200 Brussels, Belgium.

Introduction

Studies have shown that success rates of root canaltherapy generally approach 90% (Lewis & Block 1988).When treatment fails, retreatment rather than extrac-tion is usually indicated (Allen et al 1989), but thesuccess rate of retreatment cases is generally poorer(Sjogren et al 1990). Methods of evaluating results ofendodontic treatment and retreatment include radio-graphic examination; the development or persistenceof periapical radiolucencies often sen'es as criteria ofclinical failure.

The aira of this clinical study was to analyse twoapproaches to apparent failure of initial root canaltherapy; retreatment or radiographic monitoring only.The answers to three questioris were sought; (i) whatare the success and failure rates of retreatment; (ii)what influence do various factors afFecting the techni-cal and clinical results of retreatment have on itsoutcome; (iii) how valid is radiographic monitoringalone, when clinical signs and sj'mptoms are notpresent, when no, or only small, evidence of periapicalpathology is visible despite the root filling being radio-graphically deficient,'

Material and methods

This clinical study was based on a retrospective assess-ment of 1032 root canal therapy cases carried out by asingle dentist. Among these roots, 612 were retreatedand 420 asymptomatic roots with a radiographicallydeficient filling (short, overextended and/or permeableendodontic fillings) were not retreated.

Ketreatment

Assessment criteria of the initial root filling was basedupon the level of the root filling in relation to the rootapex, its apparent density and the quality of the apicalsea! (Table 1). Also recorded were;

75

76 J.-P. Van Nieuwenhuysen et al.

Table 1, Criteria for assessment of initial root filling

Previous root fillingassessment Criteria

Bad Short (>5 mm), or overextended (>3 mm),and/or permeable root filling

Questionable Short (3 mm<IU<5 mm), or overextended(1 mni<fill<3 mm), and/or doubtfulapical seal

Satisfactory Short (1 mm<fill< 3 mm), or overextended(< 1 mm), and/or presence of a fewsmall voids

Good < 1 mm from the radiographic apex andan apparently sound apical seal

1. The name, sex and age of each patient: thefollowing age categories were used: 20 to 30, 31to 40. 41 to 50. 51 to 60, 61 to 70, more than 70years.

2. The nature of the initial root filling (empty canal,paste, gutta-percha or silver points), the presenceof posts and cores and any previous complicationssuch as broken endodontic instruments, the pres-ence of steps or ledges, furcal or root perforations,and transposition of the apical part of the rootcanal preparation.

3. The reasons for retreatment including radio-graphic signs and clinical symptoms (Table2).

4. The technique of tooth isolation used: either withcotton-wool rolls or with rubber dam.

5. The different root canal treatment procedures thathad been used (Table 3).

6. The number of appointments required.7. Canal medication: antiseptic medications were

used between the appointments (paraformalde-hyde was used in the early part of the study, butas this material has been shown to be mutagenicand carcinogenic its use was replaced by calciumhydroxide), irrigants used were 2.5% sodiumhypochlorite and also the chelating agents(EDTA+urea peroxide) followed by irrigation withsodium hypochlorite. Solvents (thymol+isoamylacetate+trichloroethane or cMorofonm) were alsoused for the removal of gutta-percha.

8. The root filling techniques used were either asingle-cone technique or lateral condensation ofgutta-percha. Zinc oxide-eugenol was used assealer.

9. The distance of the root flUing from the radio-graphic apex was recorded as follows: (i) under-

Table 2. Reasons for retreatment

Reasons for retreatment

1 Presence of apical radiolucency (0-1 mm, 1—3 mm. 3-5 mm,5-10 mm and >10 nun)

1 Pain, swelling or fistula, tenderness to apical and gingiv.alpain palpation and percussion

3 Permeable and/or incomplete root filling4 Further prosthetic or extensive restorative treatment

Table 3, Root canal treatment procedures

Root canal treatment procedures

1 No initial disinfection2 Previous disinfection before mechanical debridment and

irrigation3 Initial penetration, measurement of the working length and

disinfection of the root canal4 Initial penetration, measurement of the working length,

preparation and disinfection of the root canal

filling: 0 to — 1 mm, — 1 to — 3 mm, — 3 to— 5 mm, — 5 mm or more, canals left empty and(ii) overfilling: 0 to +1 mm, +1 mm to +3 mm.+3 mm to +5 mm, more than +5 mm,

10. The complications during retreatment. Theseincluded the root canal being blocked by second-ary or reparative dentine, impassable ledging incurved canals, furcal or root perforations, trans-position during apical preparation, and brokeninstruments.

Retreatment evaluation

The classification of endodontic retreatment as a suc-cess or failure was based on technical and healingassessments (Tables 4 and 5). Success or failure ofretreatment was evaluated from recall radiographs (6months, 1 year, 2 years and more than 2 years) andpatient records of clinical examination. Only cases thathad recall examinations of 6 months or more wereanalysed.

Radiographic monitoring only

The details recorded for each patient were; name, sexand age. date of first examination. Radiographic and

Decision to retreat in endodontics 77

Table 4. Technical assessment

Technicalassessment Retreatment/former treatment

Good The retreatment corresponded to the criteriafor a good root canal filling

Improvement The retreatment improved the former treatmentUnchanged The retreatment was as good as the former

treatmentWorse The retreatment was worse than the former

treatment

Table 5, Healing assessment

Healingassessment

Radiographic appearance, cfinicalsigns and/or symptoms

Complete healing Complete resolution of periapical radiolucency,no ciinicai signs and symptoms

Improvement Decrease in sise of periapical radioiucency,no clinical signs and symptoms

Unchanged (A) No periapical radiolucency,clinical signs and symptoms

Unchanged (B) Persistence of periapical radiolncency,clinical signs and symptoms

Deterioration Increase in size of periapical radiolucencyor occurrence of periapical radiolucency,exacerbation of cfinical signs and sjfmptomsor occurrence of clinical signs and symptoms

same criteria as those used for the healing assessmentof the retreatment cases (Tahle 5),.

Radiographic examination

la evaluating the results of retreatment and monitor-ing, the radiographs were assessed by two separateobservers, who had been trained for calibration. To testintra- and inter-observer agreement the radiographswere examined twice by the two observers at aninterval of 1 month. The intra-observer agreementwas, respectively, 96% and 93%, Agreement betweenthe two observers was 94% and 90%,

To avoid the risk of inter-observer agreement occur-ring by chance the kappa coefScient was used. Thecorrected agreement between the two observers was0.74.

Statistical analysis

All the data were recorded into a table (EXCEL) and thestatistical analysis was performed using SAS (StatisticalAnalysis System) on an JBM makiirame. The compari-son between the categories and the relationshipsbetween the factors were evaluated by the Wicoxon-Mann-Whitney rank sum test (and Kmskal-Wallistest) and the Spearman rank correlation.

Table 6, Distribution of the root canals according to patient age

Age category in years Number of root canals

20<3031<404K505K6O61<70

>70Total

150192130110291

612

24.531.421,218,04,70,2

100.0

clinical diagnosis was based upon a possible presence ofa small periapical radiolucency and/or a permeable orincomplete root canal filling together with absence ofclinical signs and symptoms.

The assessment of the root filling, and any compli-cation, in these cases were based on the same criteria asin the retreatment cases (Table 4). Time intervalsbetween the &st and the last examination were noted.Assessment of cases left untreated was biased upon the

Results

Retreatment

Description of the sample. Male and female patientsrepresented 46,6% and 53,4%, respectively of thesample. Table 6 shows the distribution of the rootcanals according to patient age, Mandibular molarswere the most frequently retreated teeth (32,2%), par-ticularly the first molar. Maxillary anterior teeth wereretreated 20 times more frequently than mandibularanterior teeth. Among the retreated root canals, 67,8%(415) were sealed initially with paste (zinc oxide-eugenol or unknown) and/or gutta-percha, 9,8% (60)with silver points, 22,4% (137) had been left empty.The reason for the remaining retreatments was eitherbroken instruments or was unspecified. Followingqualitative assessment 92,6% of the initial rootfiUings were unacceptable being judged either bad orquestionable. Five per cent of the retreated canals had

78 ].-P. Van Meuwenhuysen et al.

Table 7, Distribution of the sample following the root canal treatment Table 8, Interappointment intracanal medication

procedures

Root canal treatment procedures

No preliminary disinfectionPreliminary disinfectionInitial penetration, measurement

of the working length of the rootcanal and disinfection

Initial penetration, measurement of theworking length, endodontic preparationof the root canal and disinfection

Total

Number ofroot canals

96304

132

80

612

• %

15.749.7

21.5

13.1100.0

previous complications. Retreatment for radiographicand/or clinical reasons involved 4:2(260 root canals). RetreatrDent of

!.5% of tie; sampleasymptomatic root

Antiseptic medication

Paraformaldehyde (Roclde's 4)Calcium hydroxide (Reogian Rapid)No medicationTotal

Table 9. Obturation techniques

Obturation techniques

Single-coneLateral condensation

Canals, left emptyTotal

Number ofroot canals

4872996

612

Number of

root canals

293284

356] 2

%

79.64.7

15.7100.0

%

47.946.4

5.71 nn n

canals for posts and/or defective root fillings involved57.5% of the sample (352 root canals).

More than 90% of the sample with periapical radi-olucency presented with size variations between 0and 5 mm. Rubber dam isolation was used in 51.1%of cases. The various root canal treatment proceduresused are shown in Table 7. Preliminary disinfectionbefore mechanical debridment and irrigation of theroot canal was the most frequent procedure. Themajority of the root canals required two appointmentsfor the retreatment (45.8%), with 15.7% being com-pleted in one visit, 27.4% in three visits and 11,1%requiring more than three appointments. The antisep-tic medications used between the appointments areshown in Table 8. The obturation techniques used aregiven in Table 9: single-cone and lateral condensationtechniques were employed equally. The level of theroot filling in relation to the radiographic apex isshown in Table 10. During retreatment, 62 compli-cations, arose (Table 11), Tables 12 and 13 illustratetechnical and the healing assessments of retreatment,respectively.

Factors affecting the outcome of retreatment

The patient. The outcome of retreatment according tosex was not statistically significant (Wilcoxon test,P=0,12). Spearman coefficient between a failed out-come for retreatment and an increase in age revealeda statistically significant correlation (rs=0,136;P=0.0012},

Table 10. Level of the root filling in relation to the radiographic apex

Distance of the root fillingirom the radiographic apex (mm)

Underfilling0 < l1<33<5>5Canals left empty

Overfilling0<I1<33<5>5

Total

Number ofroot canals

32897484335

501001

612

%

53.615.9

7.87.05.7

8.21.60.00.2

100.0

Retreatment procedure. Retreatment outcome was sig-nificantly improved when the following pertained: (i)rubber dam isolation (Wilcoxon test, P=0.0001); (ii)initial penetration, working length measurement, rootcanal preparation and disinfection in the first visit(rj=-0,106; P=0,0119); (iii) multiple appointments(rs=-0,145; P=0,006 and Wilcoxon test, P=0,0045);(iv) lateral condensation was performed (Wilcoxon test,P=0.0001); (v) root filling to within 1 mm of theradiographic apex (Wilcoxon test, P=0,0001),

Retreatment outcome was significantly worse when;(i) periapical radiolucency size increase (rs=0,216;

Table 11. Complications during retreatment

Decision to retreat in endodontics 79

Table 14. Distribution of root canals according to patient age

Complications during retreatmentNumber ofroot canals

Age category in years Number of root canals

Impenetrable canalsCur¥ed canalsSteps or ledgesFurcal perforationsRoot perforationsApica! transpositionsBroken instrumentsTotal

3547312

1062

20<303 K 4 04 K 5 05 K 6 06 K 7 0

>70Total

87126108

6630

3420

20.730.025.715.77.20.7

100.0

Table 12. Technical asses,sment of retreatment

Number of

Table 15. Initial size of periapical radioiucency

Initial periapicai radiolucency size{mm)

Number ofroot canals

Tecimical assessment

Worse than previous treatmentEquivalent to previous treatmentImprovement on previous treatmentCorrect retreatmentTotal

root canals

1768

207320612

%

2.811.133.852.3

100.0

Absence of periapical pathosisDetectable widening of

periodontal space1<3Total

349

3833

420

83.1

9.07.9

100,0

Table 13. Healing assessment of retreatment

Healing assessmentNumber ofroot canals

Complete healing 171Improvement, but incomplete

healing 45Status quo without

periapical radioiucencyclinical signs or S3fmptoms 308

Persistence of periapicalradiolucency, with clinicalsigns and symptoms 17

Deterioration 20Periapical status unknowii 51Total 612

27.9

7.4

50.3

2,,83,38,3

100.0

P-G.0014); (ii) complications arose during retreatment{Wilcoxon test, P=0.OO55), (iii) when the technicalquality of the root filling was in the worst category(rs=-O.152;P=O.OOO3).

The outcome of overfilling was not analysed statisti-cally because of an imbalance in the distributionbetween groups.

Table 16. Level of the root filling in relation to tbe radiographic apex

Distance of the root filling Number offi'om the radiograpMc apex (mm) root canals %

Underfiihng

3<5>5

Canals left empts'Overfilling

3<5>5

Total

Radiographic monitoring only

Sample details

Male and female patients represented 28.1% and71.9%, respectively. Table 14 illustrates the distri-bution of the root canals according to age categories.Initial radiographic diagnosis is detailed in Table 15,98.6% of the root fillings were judged bad or question-able, with only 1.4% being either good or satisfactory.The level of the root filling in relation to the radio-graphic apex is illustrated in Table 16; in most

173275

22865

1011

420

4.17.6

17,954,J15,5

0.20.00.20.2

100.0

80 J.-P. Van Nieuwenhuysen et al.

Table 17, Outcome assessment

Outcome assessment

Complete healingImprovement but incomplete

healingStatus quo

no periapical radiolucency.no clinical signs and symptoms

Persistent periapicai radioiucencyQO clinicai signs and symptoms

DeteriorationPeriapical status unknownTotal

Ntimber ofroot canals

8

2

343

5566

420

%

1,9

0,5

81,7

13,11.41,4

100,0

instances, short root fillings were observed (95,3%),with overextended fills being rare. Complications, suchas broken instraments, were involved in 6,2% of theroot canals.

The median time interval between the first and lastexamination was 6 years. Final radiographic assess-ment is detailed in Table 17. Radiographic and clinicalexaminations in these cases showed that the initialsituation was stable in 94,8% of cases. Complete andpartial healing had occurred in 2,4% of cases. Initiationor increase in size of the initial small periapical radiolu-cency was observed in 2,8% of canals.

Factors which affected the outcome in those casesreceiving only radiographic monitoring. The sex(Wilcoxon test, P=0.7] and age (r,= -0 ,044 ; P=0,3) ofthe patient were not statistically significant. There wasa statistically significantly better outcome when noperiapical radiolucency was evident on the initial radio-graph (Wilcoxon test, P=0,0001), It was not possible toinvestigate adequately the influence of the quality ofthe root filling and distance of the root filling fromradiographic root apex because of the smafi number ofroot canals that had been correctly sealed.

Discussion

When making an assessment of healing it is necessaryto divide the sample of retreated root canals into twogroups, one with symptoms, the other without. It waspossible to estimate healing only in cases with initialradiographic, clinical signs and/or symptoms. Of casesthat had been recalled over more than 6 months,71,8% were judged successful, 18.9% were consideredto be uncertain (on the way to recovery), and 9,3% had

failed. These results are similar to those recorded byAllen et al. (1989), which were 65,6% (definitivelysuccessful) and 18,3% (uncertain), Sjogren et al.(1990) noted less favourable results with only 62%success for retreatment of teeth with initial periapicalpathology. Among the original asymptomatic rootcanals, 95,4% remained asymptomatic and 4,6% failed.

In the present study, the original size ofthe periapicallesion had an effect on the rate of healing. The obser-vation period was perhaps too short however to observecomplete healing of the largest lesions, Sjogren et al.(1990) also reported a low rate of healing when rootfilled teeth with large periapical lesions were retreated.The outcome of retreatment was found to be dependenton the distance of the root filling from the radiographicapex, with the best prognosis being when the fillingreached to within 1 mm ofthe apex. This observation isaiso in agreement with the results of Sjogren et al(1990),

Complications during the retreatment led to anunfavourable prognosis and confirms the importance ofcontrolling the iatrogenic factors in root canal therapy(Morand 1992),

In the present study, the need for multiple appoint-ments arose mainly from difficulties encounteredduring the retreatment procedure. The outcome wasimproved hy completing root canal preparation at thefirst appointment and using a disinfective agentbetween visits, It may be unwise to make an inferencefrom these two ohservations because of the very lowcorrelation, but the use of calcium hydroxide, in someinstances, may be an explanation for the greater suc-cess. The outcome of retreatment was also better withaseptic tooth isolation, perhaps hecause more effectiveirrigation of the root canal is possible when a rubberdam is applied.

The decision not to initiate retreatment of the rootwhere a root filling appears deficient but rather tomonitor radiographically is a common practice. Thisstudy shows that such review leads to complications inonly a limited number of cases. It could be consideredpractical, perhaps, in cases where the coronal resto-ration does not require replacement, to keep the rootfilling under review. However, Torabinejad et al. (1992)have recently reported that a lack of integrity of coronalseal can result in recontamination of sealed root canalsafter a short time. If the coronal filling is deficient orlost, the risk of percolation and the possibility of bac-terial (re)Gontaniination of a poorly sealed root canal isvery high, Retreatment of an inadequately sealed rootcanal is indicated, therefore, when the canal is to be

Decision to retreat in endodontics 8 1

retained, as the periapical stability could he upsetby bacterial invasion. When replacing coronal resto-rations, it is essential to ensure a coronal seal of theroot canal system.

Conclusions

Technical assessment of retreatment in this study indi-cated that;1, The root canal was adequately sealed (the filling

extended to vvithin 1 mm of the apex) in 52,3% ofcases,

2, The root lilling -was improved in 33,8% of canals,3, The root fllling appeared identical to the initial

treatment in 11.1% of cases.4, The root filling was worse than the initial treat-

ment in 2.8% of canals.

Clinical assessment of the retreatment of sympto-matic roots indicated that:1, 71.8% of retreatment were judged to be successful.2, 18.9% showed some healing.3, 9,3% failed.

The initial size of the periapical lesion, the use ofrubber dam, the obturation technique and the apicallevel of the root filling all had a statistically significantinfluence on the result of the retreatment.

Avoidance of retreatment with only radiographicmonitoring (median time span 6 years) resulted in:1, no change in 94.8% of canals,2, healing in 2,4% of canals,3, failure in 2,8% of cases.

Retreatment is clearly indicated when a periapicalradiolucency is accompanied by clinical signs and/orsymptoms, and the relative success of such treatmentrises to 91%. When no or onJy small radiographicevidence of periapical pathology is present,, and clinicalsigns and symptoms are absent no treatment appears toresult in complications in only a small percentage ofcases, despite what appears to be a less than ideal rootfilling. If radiographic monitoring alone is contem-plated there should be no suspicion of more sinisterpathology.

Acknowledgements

The authors express special thanks to Dr ElizabethSaunders for her editorial assistance.

References

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LEWIS RD, BLOCK RM (1988) Management of endodontic failures. OralSurgery, Oral Medicine and Oral Pathohgii 66, 711—21.

MoEAND' MA (1992) The true reasons for endodontic failures. Journalof Dental Research 71, 565 (Abs 397).

SjOGKEN U, HAGGLUND B, SDNDQVIST G, WING K .(1990) Factors affectingthe long-term results of endodontic treatment, journal of Endodon-tics 16, 498-504.

TOEABINEJAD M, CHEE V, SoNG H (1992) Coronal leaicage of unsealedendodontically treated teeth, journal of Dental Research 71, 564(Abs 394).