Removing Root Canal Obturation Materials

Removing Root Canal Obturation Materials

R E S E A R C H Removing root canal obturation materials A comparison of rotary file systems and re-treatment agents Jamie Ring, DMD; Peter E...

980KB Sizes 0 Downloads 13 Views

R

E

S

E

A

R

C

H

Removing root canal obturation materials A comparison of rotary file systems and re-treatment agents Jamie Ring, DMD; Peter E. Murray, PhD; Kenneth N. Namerow, DDS; B. Ivan Moldauer, DDS; Franklin Garcia-Godoy, DDS, MS

A

J

D

A

I

A

T

IO N

Background. The authors conducted a study to com✷ ✷ ® pare the effectiveness and working time of two rotary instrumentation file systems with two solvents for the N removal of gutta-percha (GP) (ProTaper Universal, C U U IN G ED Dentsply Tulsa Dental, Tulsa, Okla.) or resin-based com- A 2 RT ICLE posite (RBC) (RealSeal 1 Bonded Obturator, SybronEndo, Orange, Calif.) endodontic obturation materials. Methods. The authors instrumented 88 human extracted teeth and obturated the root canals of 80 of the teeth with either GP with AH Plus root canal sealer (Dentsply Maillefer, Tulsa, Okla.) or RBC with adhesive according to the manufacturers’ instructions. They re-treated each tooth by using one of two rotary instrumentation file systems. They assessed each file system by using chloroform or orange solvent re-treatment agents. The authors measured the time needed to remove the obturation material from each tooth. They processed the teeth for scanning electron microscopy, and two blinded reviewers categorized the micrographs according to several criteria. Results. The authors observed more RBC remnants on the root canal surfaces compared with GP remnants after re-treatment. The re-treatment solvents and file systems were equally effective in removing the obturation materials. Conclusion. The study results show that the quickest root canal retreatment can be accomplished by using EndoSequence rotary files (Brasseler, Savannah, Ga.) and orange solvent to remove RBC obturation material. Clinical Implications. Re-treatment with EndoSequence rotary files was quicker than re-treatment with ProTaper Universal re-treatment files (Dentsply Tulsa Dental). However, in this study, the file systems were similarly effective in removing GP and RBC. Orange solvent was as effective as chloroform in removing obturation materials, but its use is less timeconsuming. Key Words. Endodontic files; endodontic therapy; obturation; root canal; dental materials. JADA 2009;140(6):680-688. T

A

ABSTRACT CON

recent trend in endodontics has been the development of bonded obturating materials via the use of dentin adhesive technology transferred from restorative dentistry.1 Gutta-percha (GP) has been the most commonly used obturating material during the last century. Although successful, GP lacks the ability to completely seal the root canal surfaces, which may result in leakage of bacteria.2-5 GP is being challenged by a resin-based composite (RBC) material (RealSeal 1 Bonded Obturator, SybronEndo, Orange, Calif.), a new generation of root canal obturation materials. The primary component is Resilon, which was introduced in 2004.6,7 Several studies have shown that the RBC obturating material has superior properties to those of GP. Two recent in vitro and in vivo studies demonstrated that the RBC obturating material leaked less than did GP.6,7 In addition, Teixeira and colleagues8 reported that the RBC obturating material increased the fracture resistance of tooth roots compared with those filled with GP. The handling properties of the RBC obturating material are similar to those of

At the time this study was conducted, Dr. Ring was an endodontic resident, Department of Endodontics, College of Dental Medicine, Nova Southeastern University, Fort Lauderdale, Fla. He now is in private practice in Westminster, Colo. Dr. Murray is an associate professor, Department of Endodontics, College of Dental Medicine, Nova Southeastern University, 3200 S. University Drive, Fort Lauderdale, Fla. 33328, e-mail “[email protected]”. Address reprint requests to Dr. Murray. Dr. Namerow is the chair and postgraduate program director, Department of Endodontics, College of Dental Medicine, Nova Southeastern University, Fort Lauderdale, Fla. Dr. Moldauer is in private practice in Weston, Fla. At the time this study was conducted, Dr. Garcia-Godoy was the associate dean for research, College of Dental Medicine, Nova Southeastern University, Fort Lauderdale, Fla. He now is the executive dean for research, College of Dentistry, University of Tennessee, Memphis.

680

JADA, Vol. 140

http://jada.ada.org

June 2009

Copyright © 2009 American Dental Association. All rights reserved. Reprinted by permission.

R E S E A R C H

GP6; however, results of a recent study showed that the type of file system can affect the amount of residual filling material remaining within the root canal system.9 Because data are scarce, the need exists to compare the effectiveness of file systems for the removal of RBC and GP obturating materials. Rotary nickel-titanium files are fast and effective when used in combination with chloroform solvent to remove RBC obturating material and vertically compacted GP from the root canal system.9 Nevertheless, because of carcinogenic concerns, some authors have advocated the use of alternative solvents.10-13 To date, the literature contains studies only of rotary instruments used with and without chloroform to remove RBC obturating material from root canals.14-16 Consequently, research is needed to investigate the effectiveness of alternative solvents, such as orange solvent, in the removal of RBC and GP obturating materials. In the 1960s, Dr. Herbert Schilder’s systematic cleaning and shaping regimen encompassed several principles, including filling the root canal in three dimensions, which led to our current predictable method of obturation.17 A study of 1.4 million endodontic procedures revealed that 97 percent were successful after eight years.18 For the small percentage of cases in which treatment is not successful, a comparison of file systems and solvents used for re-treatment could be beneficial. Nonsurgical endodontic re-treatment, when indicated,19 requires the clinician to regain access to the entire root canal system through complete removal of the endodontic filling material. This enables him or her to attempt to disinfect the root canal system through chemomechanical reinstrumentation, a prerequisite for a successful outcome.20 The purpose of this study was to compare the working time and effectiveness of two rotary instrumentation file systems with two solvents for the removal of GP or RBC endodontic obturating materials. SUBJECTS, MATERIALS AND METHODS

Specimen preparation. We collected 88 human teeth from an archive of extracted teeth, which we used after receiving institutional review board approval from Nova Southeastern University, Fort Lauderdale, Fla. The teeth were stored in a sterile saline solution at room temperature until use. One of us (J.R.) cleaned the outside of the

teeth by using hand instruments. He examined the teeth under an operating microscope to detect possible fractures. He examined radiographs of each tooth to ensure that each had a single root canal. One of us (P.E.M.) used a low-speed circular saw to remove the crowns of the teeth near the level of the cementoenamel junction and attained a root length of approximately 17 millimeters. He determined the patency of the root canal once a no. 10 K-file could be viewed at the apical foramen. He established the working lengths to be 1 mm short of this length. A single operator (J.R.) prepared the root canals by using a crown-down technique with tapered nickel titanium rotary instruments (ProFile .06 ISO Rotary Instruments, Dentsply Tulsa Dental, Tulsa, Okla.) to a master apical file 35/.06. He removed the smear layer during instrumentation by using a combination of 6 percent sodium hypochlorite and 17 percent ethylenediaminetetraacetic acid (EDTA) solutions.21 The clinician used 2 percent chlorhexidine solution as a final flush for teeth that were to be obturated with RBC, according to the manufacturer’s instructions. He dried the root canals with sterile paper points. We randomly divided 80 of the teeth into two groups of 40 each. They were to be obturated with GP (ProTaper Universal, Dentsply Tulsa Dental) or RBC (RealSeal 1 Bonded Obturator) by using warm vertical condensation. RBC. The clinician (J.R.) obturated 40 teeth using RBC according to the manufacturer’s directions. Using a microbrush, he placed two drops of primer (RealSeal) into the root canal space. The clinician wicked out excess primer by using a sterile paper point. He then placed the sealer (RealSeal SE self-etch sealant) into the canal by using a sterile paper point and a RealSeal master cone. The clinician obturated the canals using the continuous-wave compaction technique and backfilled them with RBC by using the Obtura II gun (Obtura Spartan, Fenton, Mo.). Gutta-percha. The clinician filled the second ABBREVIATION KEY. C: Chloroform. EDTA: Ethylenediaminetetraacetic acid. ES: EndoSequence rotary files (Brasseler, Savannah, Ga.). GP: Gutta-percha. OS: Orange solvent. PT: ProTaper Universal retreatment files (Dentsply Tulsa Dental, Tulsa, Okla.). RBC: Resin-based composite. SEM: Scanning electron microscopy.

JADA, Vol. 140

http://jada.ada.org

Copyright © 2009 American Dental Association. All rights reserved. Reprinted by permission.

June 2009

681

R E S E A R C H

group of 40 teeth with GP and AH Plus root canal Group 7. The clinician removed the RBC obtusealer (Dentsply Maillefer, Tulsa, Okla.) by using ration material and sealer by using ProTaper the continuous-wave compaction and backfill Universal re-treatment files and orange solvent techniques. We stored the specimens at room in a technique similar to that used in group 1. temperature in 100 percent humidity for two Group 8. The clinician removed the RBC obtuweeks.9 ration material and sealer by using EndoRe-treatment. We then further divided the Sequence rotary files and orange solvent in a obturated teeth into the following eight recrown-down technique similar to that used in treatment groups, consisting of 10 samples each: group 3. Group 1. The clinician removed the GP and Control groups. The clinician did not obtusealer by using ProTaper Universal re-treatment rate the remaining eight teeth, and we divided files and chloroform solvent. To create a small them into the following four re-treatment groups: reservoir for the chloroform solvent, the clinician Group 9. The clinician instrumented the teeth used a D1 file to remove a small amount of GP at with EndoSequence rotary files and irrigated the orifice. The dentist gently pressed the D1 file them with chloroform solvent. into the obturation material to remove it from the Group 10. The clinician instrumented the coronal one-third of the canal space. Next, the teeth with ProTaper Universal re-treatment files clinician used the D2 file to remove material and irrigated them with chloroform solvent. incrementally from the middle oneGroup 11. The clinician instruthird of the canal. Finally, the clinimented the teeth with EndoThe clinician was cian used the D3 file to remove Sequence rotary files and irrigated unable to completely material from the apical one-third them with orange solvent. of the canal space. The clinician Group 12. The clinician instruremove the obturation used the files in an electric motor mented the teeth with ProTaper materials from any of handpiece set at between 500 and Universal re-treatment files and the root canals. 700 revolutions per minute, irrigated them with orange solvent. according to the manufacturer’s We considered re-treatment comdirections. The dentist injected small increments plete when three objectives were met: of chloroform solvent into the canal between each dThe clinician could not visualize any obturation use of the file. material between the cutting flutes of the Group 2. The clinician removed GP and sealer instrument. as described in group 1, but he used orange soldThe clinician could not observe any visible vent in place of chloroform solvent. obturation material on the radiograph. Group 3. The clinician removed GP and sealer dThe clinician could not wick out any material as described in group 1, but he used Endofrom the canal space with a sterile paper point. Sequence rotary files (Brasseler, Savannah, Ga.) The clinician then performed a final irrigation in place of ProTaper Universal re-treatment files. protocol for teeth in groups 1 through 8, which The clinician removed the GP by using a crownconsisted of 6 percent sodium hypochlorite and down technique, starting with a .06 taper no. 45 17 percent EDTA.21 Using a stopwatch, two assistants recorded the working time (measured to the file and ending with a .06 taper no. 35 file. nearest second) needed to remove the obturation Group 4. The clinician removed the GP and material from each tooth. sealer by using EndoSequence rotary files and Preparing for scanning electron microsorange solvent in a crown-down technique similar copy. One of us (P.E.M.) fixed the teeth by subto that used in group 3. merging them in a 10 percent neutral-buffered Group 5. The clinician removed the RBC obtuformalin solution at 18oC for 24 hours. He then ration material and sealer by using Endodehydrated the teeth in a graded series of ethanol Sequence rotary files and chloroform solvent in a solutions: 80 percent, 90 percent and 95 percent crown-down technique similar to that used in for 15 minutes each, followed by three 10-minute group 3. washes in 100 percent ethanol. Using a chisel, the Group 6. The clinician removed the RBC obtuoperator then prepared the teeth for scanning ration material and sealer by using ProTaper electron microscopy (SEM) by fracturing them Universal re-treatment files and chloroform solinto halves along the longitudinal axis. He then vent in a technique similar to that used in group 1. 682

JADA, Vol. 140

http://jada.ada.org

June 2009

Copyright © 2009 American Dental Association. All rights reserved. Reprinted by permission.

R E S E A R C H

WORKING TIME (MINUTES)

dried the teeth on filter paper for 30 minutes. The 10 operator then mounted the 7.0 9 tooth specimens onto aluminum stereoscan stubs 8 with rapid-set adhesive 4.8 7 (Araldite, Devcon, 5.7 5.4 Shannon, Ireland). He 6 4.6 then coated the dried mounted specimens with a 3.3 5 3.0 20- to 30-nanometer thin 4 metallic layer of gold/ 2.3 palladium in a sputter 3 coater (Polaron E5000, 2 Bio-Rad, Hercules, Calif.). SEM. The operator 1 (P.E.M.) viewed the speci0 mens in an SEM (Quanta 1 2 3 4 5 6 7 8 200, FEI, Hillsboro, Ore.). GP GP GP GP RBC RBC RBC RBC PT PT ES ES ES PT PT ES He scanned each of the C OS C OS C C OS OS root canals in its entirety to obtain an overview of RE-TREATMENT GROUP the general surface topography. The operator then Figure 1. Working time required to remove obturation materials. Bars indicate mean (standard deviation). GP: Gutta-percha. RBC: Resin-based composite. PT: ProTaper Universal re-treatment files divided the teeth into (Dentsply Tulsa Dental, Tulsa, Okla.). ES: EndoSequence rotary files (Brasseler, Savannah, Ga.). coronal, middle and apical C: Chloroform. OS: Orange solvent. thirds and, using digital image analysis software,22 obtained one represenutes, an average of 2.2 minutes less than the 5.8 tative SEM micrograph at ×2,000 magnification. minutes needed to remove GP (ANOVA, P < .001). Two blinded reviewers then categorized the 264 The mean time required to remove both obturaSEM micrographs (one of each one-third) accordtion materials with EndoSequence rotary files was 4.1 minutes, an average of 1.2 minutes less ing to the following criteria: than the 5.3 minutes required when using Prod0: No presence of obturation debris on the Taper Universal re-treatment files (ANOVA, dentin surface; P = .002). The mean time required to remove both d1: Less than 50 percent of the dentin surface covered with obturation debris; obturation materials by using chloroform was 5.0 minutes, an average of 0.6 minutes more than d2: Greater than or equal to 50 percent of the the 4.4 minutes required when using orange dentin surface covered with obturation debris; solvent (ANOVA, P = .149). d3: One hundred percent of the dentin surface Remnant obturation materials. The clinicovered with obturation debris. cian was unable to completely remove the obturaData analysis. We analyzed the re-treatment tion materials. As shown in Figure 2 (groups 1 time data by using an analysis of variance through 12), we observed remnants on each of the (ANOVA) test. We analyzed the SEM microSEM micrographs. As Figure 3 (page 685) shows, graphs that showed remnants of obturation the obturation materials (and smear layer) were materials on the root canal surfaces by using χ2 not removed entirely from any of the 88 restatistics for each of the re-treatment groups at treated root canals in the 12 groups. All of the rea significance of 95 percent (StatView, SAS treated teeth in groups 1 through 6 and group 8 Institute, Cary, N.C.). had root canal surfaces on which more than 50 RESULTS percent of the surface was covered with obturation debris, and the teeth in group 7 had root Working time. Figure 1 shows the working canal surfaces on which 100 percent of the surface times for the eight re-treatment groups. The was covered in obturation debris. The teeth in the mean time required to remove RBC was 3.6 minJADA, Vol. 140

http://jada.ada.org

Copyright © 2009 American Dental Association. All rights reserved. Reprinted by permission.

June 2009

683

R E S E A R C H

1

2

3

4

5

6

7

8

9

10

11

12

Figure 2. Scanning electron micrographs of root canal surfaces after re-treatment. Numbers indicate the re-treatment groups.

four control groups (9 through 12) had root canal surfaces on which 100 percent of the surface was covered with smear layer debris. GP was removed more completely from the root canal surfaces after re-treatment compared with RBC (χ2, P < .001). The mean percentage of retreated root canal surfaces covered completely (that is, 100 percent category) with GP remnants was 55.0 percent (groups 1 through 4) (Figure 3), compared with 94.2 percent of root canal surfaces covered completely with RBC remnants (groups 5 though 8) (Figure 3). The results showed little difference in the removal of RBC (groups 5 through 8), underlying the lack of effectiveness of RBC removal after re-treatment (χ2, P = .621). Rotary re-treatment file systems. The mean percentage of root canal surfaces covered completely (that is, 100 percent category) after retreatment with ProTaper Universal re-treatment files was 73.4 percent (groups 1, 2, 6 and 7) 684

JADA, Vol. 140

http://jada.ada.org

(Figure 3), compared with 75.9 percent of root canal surfaces covered completely after retreatment with EndoSequence rotary files (groups 3 through 5 and 8) (Figure 3). Thus, ProTaper Universal re-treatment files were slightly more effective at removing GP and RBC obturation materials from the root canal surfaces compared with EndoSequence rotary files (Figure 4), but the difference was not statistically significant across all re-treatment groups (χ2, P = .059). Both the ProTaper Universal re-treatment (χ2, P < .001) and EndoSequence rotary files were more effective (χ2, P < .001) at removing GP than RBC obturation materials (Figure 4). However, we observed little difference between the effectiveness of ProTaper Universal re-treatment and EndoSequence rotary files with regard to removal of GP (χ2, P = .176). Removal agents. The mean percentage of retreated root canal surfaces covered completely

June 2009

Copyright © 2009 American Dental Association. All rights reserved. Reprinted by permission.

R E S E A R C H

ROOT CANAL SURFACES WITH OBTURATION MATERIAL REMNANTS (%)

ROOT CANAL SURFACES IN RE-TREATMENT GROUPS (%)

with obturation material 100 (that is, 100 percent category) after re-treatment 90 with chloroform was 59.2 80 43.3 percent (groups 1, 3, 5 and 53.4 70 56.7 6) (Figure 3). This com66.7 60 pares with 73.4 percent of 83.3 root canal surfaces covered 96.7 96.7 50 100 100 100 100 100 completely with obturation 40 material after re43.3 23.3 33.3 30 treatment with orange solvent (groups 2, 4, 7 and 8) 20 33.3 (Figure 3). The results 6.7 10 20 show little difference 13.3 13.3 10 3.3 3.3 0 between chloroform and 1 2 3 4 5 6 7 8 9 10 11 12 orange solvents with regard to their effectiveRE-TREATMENT GROUP ness at removing obtura> 50% 0% < 50% 100% tion materials from root canal surfaces (χ2, Figure 3. The percentage of root canal surfaces with obturation material remnants after P = .789). Both the chlorore-treatment. See Figure 1 for descriptions of the re-treatment groups. 2 form solvent (χ , P < .009) and the orange solvent (χ2, P < .001) were more effective at removing GP com100 pared with RBC obturation materials (Figure 5). However, we observed little difference between > 50 the chloroform and orange solvents with regard to the removal of GP (χ2, P = .340). < 50 Control groups. The study results showed that the chloroform solvent removed the smear layer 0 Apical Middle Coronal Apical Middle Coronal equally well when the Gutta-percha and AH Plus RealSeal 1 Bonded Obturator canals were instrumented and RealSeal SE self-etch sealant with EndoSequence rotary files (group 9, Figures 2 OBTURATION MATERIAL AND SEALER and 3) or ProTaper UniRotary Re-treatment File System versal re-treatment files EndoSequence rotary files ProTaper Universal re-treatment files (group 10, Figures 2 and 3). Likewise, we found no Figure 4. Root canal surfaces with remnants of obturation material after use of rotary redifference in the ability of treatment file systems. Bars indicate mean (standard deviation). RealSeal 1 Bonded Obturator and RealSeal SE self-etch sealant are manufactured by SybronEndo, Orange, Calif. AH Plus root canal the orange solvent to sealer is manufactured by Dentsply Maillefer, Tulsa, Okla. EndoSequence rotary files are manufacremove the smear layer in tured by Brasseler, Savannah, Ga. ProTaper Universal re-treatment files are manufactured by Dentsply Tulsa Dental, Tulsa, Okla. canals instrumented with EndoSequence rotary files DISCUSSION (group 11, Figures 2 and 3) or ProTaper Universal re-treatment files (group 12, The goal of nonsurgical endodontic re-treatment Figures 2 and 3). is to remove all obturation material and to disinJADA, Vol. 140

http://jada.ada.org

Copyright © 2009 American Dental Association. All rights reserved. Reprinted by permission.

June 2009

685

R E S E A R C H

ROOT CANAL SURFACES WITH OBTURATION MATERIAL REMNANTS (%)

Universal re-treatment files are more timeconsuming may relate to the tip size of the last file 100 used during re-treatment. The tip of the D3 ProTaper Universal re-treatment file is size 20, whereas the last > 50 master apical file used in the EndoSequence protocol is size 35. Therefore, it may be beneficial to < 50 enlarge the canal space further after using the ProTaper Universal retreatment file system to 0 remove obturation materApical Middle Coronal Apical Middle Coronal ial more efficiently. Gutta-percha and AH Plus RealSeal 1 Bonded Obturator In this study, we found and RealSeal SE self-etch sealant that for all re-treatment OBTURATION MATERIAL AND SEALER groups, the working time required to remove RBC Removal Agent was a mean of 2.2 minutes less than that required to Chloroform Orange Solvent remove GP. These results are consistent with those of Figure 5. Root canal surfaces with remnants of obturation material after use of removal agents. Bars indicate mean (standard deviation). RealSeal 1 Bonded Obturator and RealSeal SE self-etch other published studies,9,10 sealant are manufactured by SybronEndo, Orange, Calif. AH Plus root canal sealer is manufactured but they are the opposite of by Dentsply Maillefer, Tulsa, Okla. those reported by Tasdemir ¸ fect the root canal system.23 The inability to and colleagues.25 One hypothesis for the faster reremove all debris may result in bacteria being left treatment time for RBC is that the core material behind, which may cause periapical disease to has a lower melting point and a higher molecular persist and result in eventual endodontic failure. weight than those for GP; as a result, when subTherefore, it is necessary to identify the optimum jected to frictional heat generated by rotary file system that will allow the fastest and most instruments, the RBC exhibits higher flowability effective removal of obturation material from the than does GP.9 root canal. To our knowledge, no investigators In the study by Tasdemir ¸ and colleagues,25 the have evaluated the effectiveness of EndoSequence obturation material was allowed to set for six rotary files to remove obturation material from weeks. By contrast, in our study, a setting time of root-filled teeth, and only a single group of two weeks elapsed before re-treatment, a protocol investigators24 has evaluated the effectiveness we based on that of de Oliveira and colleagues.9 of ProTaper Universal re-treatment files to In clinical practice, many months or years typiremove obturation material from root-filled teeth. cally pass before a tooth requires re-treatment. As Re-treatment files. In our study, the Endotime elapses, the setting, chemical and physical Sequence rotary and ProTaper Universal recharacteristics of the obturation materials and treatment files were similarly effective at sealers may change slightly according to environremoving GP and RBC obturation materials from mental conditions.26 Clinical data are lacking the apical, middle and coronal aspects of root regarding the precise nature of these changes, canal surfaces. A major advantage of the Endoparticularly for new formulations of obturation Sequence rotary files is that they required a mean materials and sealers. We anticipate that the of 1.2 minutes less working time per tooth comworking times needed to remove obturation pared with the ProTaper Universal re-treatment materials and sealers will not change signififiles. One possible reason why the ProTaper cantly once the materials have set fully, but veri686

JADA, Vol. 140

http://jada.ada.org

June 2009

Copyright © 2009 American Dental Association. All rights reserved. Reprinted by permission.

R E S E A R C H

fication is needed through research. Obturation material remnants. In our study, the GP and RBC obturation materials were not removed completely from the 80 root canals; in each of the SEM micrographs, we observed some remnants. These findings are in agreement with those of Cunha and colleagues.27 The results of our study revealed that GP is removed more easily from the coronal and middle aspects of the root canal compared with RBC. These results indicate that bonding to the root canals is more complete for RBC than for GP; however, further research is needed to explore the “monoblock” theory of bonding core material to the canal walls so thoroughly that the tooth and material become a single block.6 Our findings are in contrast with those of Cunha and colleagues27 and de Oliveira and colleagues,9 who reported that the canals obturated with RBC were cleaner (that is, less obturation debris) after re-treatment compared with those obturated with GP. Obturation methods. One explanation for the divergence in study results is the difference between the obturation methods. In our study, we obturated the root canals by using a continuous wave of warm vertical compaction. Cunha and colleagues27 obturated the root canals with a hybridization of lateral condensation and vertical compaction, while de Oliveira and colleagues9 obturated the root canals by using lateral condensation only. A single operator obturated the canals in our study to minimize the variability that might have resulted from using multiple operators. Removal agents. The mean working time required to remove the obturation materials with orange solvent was 0.6 minutes less than the 5.0 minutes required for chloroform. Nevertheless, both chloroform and orange solvents were similarly effective in removing obturation materials from the root canal surfaces. Both the chloroform and orange solvents were more effective in removing the GP obturation material than they were in removing the RBC obturation material. The operator removed GP most effectively—from most to least effective—from the coronal, middle and apical aspects of the root canal. By contrast, the operator was unable to remove the RBC effectively from any aspect of the root canal. However, we observed little difference between the effectiveness of chloroform and orange solvents in removing the GP. Despite its reported toxicity and possible carcinogenic activity, chloro-

form has been proven to be safe for use during endodontic re-treatment procedures.28,29 Our findings favor the use of orange solvent, because it is as effective as chloroform but can lessen the working time. CONCLUSION

The results of this ex vivo study demonstrate that re-treated root canals still contain extensive remnants of obturation material. The clinician removed GP more completely from the coronal and middle root canal surfaces compared with RBC. However, the clinician was able to remove RBC more quickly than GP. Re-treatment with EndoSequence rotary files was quicker than retreatment with ProTaper Universal re-treatment files; however, the file systems were similarly effective in removing GP and RBC. Orange solvent was as effective as chloroform for the removal of obturation materials, but its use is less time-consuming. These observations support our conclusion that the file systems, removal agents and obturation materials are not yet fully optimized and there is room for improvement. ■ Disclosure. None of the authors reported any disclosures. This study was supported by Nova Southeastern University Health Professions Division, Fort Lauderdale, Fla. The authors give special thanks to Drs. Mansi Malavia and Rhona Guilarte for their help with this project and Drs. Karla Ring and Sonia Chopra for reviewing the scanning electron micrographs. 1. Schwartz RS. Adhesive dentistry and endodontics, part 2: bonding in the root canal system—the promise and the problems: a review. J Endod 2006;32(12):1125-1134. 2. Swanson K, Madison S. An evaluation of coronal microleakage in endodontically treated teeth, part I: time periods. J Endod 1987;13(2): 56-59. 3. Madison S, Wilcox L. An evaluation of coronal microleakage in endodontically treated teeth, part III: in vivo study. J Endod 1988; 14(9):455-458. 4. Torabinejad M, Ung B, Kettering JD. In vitro bacterial penetration of coronally unsealed endodontically treated teeth. J Endod 1990; 16(12):566-569. 5. Khayat A, Lee SJ, Torabinejad M. Human saliva penetration of coronally unsealed obturated root canals. J Endod 1993;19(9):458-461. 6. Shipper G, Ørstavik D, Teixeira FB, Trope M. An evaluation of microbial leakage in roots filled with a thermoplastic synthetic polymer-based root canal filling material (Resilon). J Endod 2004;30(5): 342-347. 7. Shipper G, Teixeira FB, Arnold RR, Trope M. Periapical inflammation after coronal microbial inoculation of dog roots filled with guttapercha or Resilon. J Endod 2005;31(2):91-96. 8. Teixeira FB, Teixeira EC, Thompson JY, Trope M. Fracture resistance of roots endodontically treated with a new resin filling material (published correction appears in JADA 2004;135[7]:868). JADA 2004; 135(5):646-652. 9. de Oliveira DP, Barbizam JV, Trope M, Teixeira FB. Comparison between gutta-percha and resilon removal using two different techniques in endodontic retreatment. J Endod 2006;32(4):362-364. 10. Ezzie E, Fleury A, Solomon E, Spears R, He J. Efficacy of retreatment techniques for a resin-based root canal obturation material. J Endod 2006;32(4):341-344. 11. Schirrmeister JF, Meyer KM, Hermanns P, Altenburger MJ, Wrbas KT. Effectiveness of hand and rotary instrumentation for

JADA, Vol. 140

http://jada.ada.org

Copyright © 2009 American Dental Association. All rights reserved. Reprinted by permission.

June 2009

687

R E S E A R C H

removing a new synthetic polymer-based root canal obturation material (Epiphany) during retreatment. Int Endod J 2006;39(2):150-156. 12. Ferreira JJ, Rhodes JS, Ford TR. The efficacy of gutta-percha removal using Profiles. Int Endod J 2001;34(4):267-274. 13. Tamse A, Unger U, Metzger Z, Rosenberg M. Gutta-percha solvents: a comparative study. J Endod 1986;12(8):337-339. 14. Wourms DJ, Campbell AD, Hicks ML, Pelleu GB Jr. Alternative solvents to chloroform for gutta-percha removal. J Endod 1990;16(5): 224-226. 15. Hunter KR, Doblecki W, Pelleu GB Jr. Halothane and eucalyptol as alternatives to chloroform for softening gutta-percha. J Endod 1991; 17(7):310-311. 16. Wilcox LR. Endodontic retreatment with halothane versus chloroform solvent. J Endod 1995;21(6):305-307. 17. Langford A, Cunningham PJ. An evaluation of Schilder’s endodontic technique. Aust Dent J 1972;17(5):353-354. 18. Salehrabi R, Rotstein I. Endodontic treatment outcomes in a large patient population in the USA: an epidemiological study. J Endod 2004; 30(12):846-850. 19. Friedman S, Stabholz A. Endodontic retreatment: case selection and technique, part 1: criteria for case selection. J Endod 1986;12(1): 28-33. 20. Bergenholtz G, Lekholm U, Milthon R, Heden G, Odesjö B, Engström B. Retreatment of endodontic fillings. Scand J Dent Res 1979;87(3):217-224. 21. Yamada RS, Armas A, Goldman M, Lin PS. A scanning electron

688

JADA, Vol. 140

http://jada.ada.org

microscopic comparison of a high volume final flush with several irrigating solutions: part 3. J Endod 1983;9(4):137-142. 22. Murray PE, Farber RM, Namerow KN, Kuttler S, Garcia-Godoy F. Evaluation of Morinda citrifolia as an endodontic irrigant. J Endod 2008;34(1):66-70. 23. Gordon MP. The removal of gutta-percha and root canal sealers from root canals. N Z Dent J 2005;101(2):44-52. 24. Gu LS, Ling JQ, Wei X, Huang XY. Efficacy of ProTaper Universal rotary retreatment system for gutta-percha removal from root canals. Int Endod J 2008;41(4):288-295. 25. Tasdemir ¸ T, Yildirim T, Celik D. Comparative study of removal of current endodontic fillings. J Endod 2008;34(3):326-329. 26. Nielsen BA, Beeler WJ, Vy C, Baumgartner JC. Setting times of Resilon and other sealers in aerobic and anaerobic environments. J Endod 2006;32(2):130-132. 27. Cunha RS, De Martin AS, Barros PP, et al. In vitro evaluation of the cleansing working time and analysis of the amount of gutta-percha or Resilon remnants in the root canal walls after instrumentation for endodontic retreatment. J Endod 2007;33(12):1426-1428. 28. Chutich MJ, Kaminski EJ, Miller DA, Lautenschlager EP. Risk assessment of the toxicity of solvents of gutta-percha used in endodontic retreatment. J Endod 1998;24(4):213-216. 29. Wilcox LR, Krell KV, Madison S, Rittman B. Endodontic retreatment: evaluation of gutta-percha and sealer removal and canal reinstrumentation. J Endod 1987;13(9):453-457.

June 2009

Copyright © 2009 American Dental Association. All rights reserved. Reprinted by permission.