The adaptation achieved by four root canal filling techniques as assessed by three methods Constantine Amditis* Stephen M. Blacklert Roland W. Bryant$ George H. Hewitts

Key words: Adaptation, endodontics, leakage, root canal fillings. Abstract Four root canal filling techniques - lateral condensation, McSpadden compaction, ultrasonic activation (Enac), and thermoplastic injection (Ultrafil) were assessed for adaptation of the filling material to the canal wall. The adaptation and leakage were examined quantitatively using an electrochemical method and a linear dye penetration method, and qualitatively by radiographic evaluation. Using the electrochemical method, differences among obturation techniques were relatively small, although a greater proportion of the teeth that had been filled by lateral condensation exhibited no leakage. Radiographically, the techniques appeared to exhibit similar adaptation in the apical 6 mm. The techniques of lateral condensation and ultrasonic activation showed superior control of length of the root canal filling. (Received for publication September 1991. Accepted January 1992.)

Introduction Radiographic evaluation is the only method available clinically for assessing the adaptation of the

*Department of Preventive Dentistry, Westmead Hospital Dental Clinical School. TEndodontist, Sydney. $Department of Operative Dentistry, The University of Sydney. §Department of Clinical Dentistry, Westmead Hospital Dental Clinical School. Australian Dental Journal 1992;37(6):439-44

root filling to the canal wall. Because inadequate adaptation and seal have been shown to be the cause of more than 50 per cent of endodontic failues,' various in v i m tests for adaptation have been devised to evaluate different obturation techniques and materials. The most common laboratory method for assessing the seal of root canal fillings measures the penetration of dyes or radioisotopes along the Numerous dyes have been used and, of these, an aqueous solution of methylene blue has been among the most Following developmental work by Jacobson and von Fraunhofer,8 several studies have reported the results for an electrochemical method of determining leakage in an obturated anal.^,^‘" In addition to providing quantitative information of the leakage, the technique allows continuous assessment over a period of time. The purpose of this study was to examine the adaptation and seal achieved by four different endodontic obturation techniques, using three different assessment methods: the electrochemical method, linear dye penetration and radiographic evaluation.

Materials and method Selection and storage of teeth Human teeth, comprising maxillary and mandibular incisors and canines and mandibular premolars, were obtained from those extracted in the Oral Surgery Department of Westmead Hospital Dental Clinical School and were stored initially in 10 per cent normal saline. 439

T o determine their suitability for the study, the teeth were radiographed from both a facial and a proximal aspect and those with badly calcified or tortuous canals were discarded. Teeth with mature apical development and with single straight canals or canals with only slight apical curvatures were accepted. Forty teeth were divided randomly into four groups of ten teeth - one group for each of the proposed obturation techniques: Group I - lateral condensation; Group I1 - McSpadden compaction; 1 Group I11 - ultrasonically activated condensation with the Enac ultrasonic device1 Group IV - thermoplasticized injection with the Ultrafil system.** The teeth were stored in 1 per cent sodium hypochlorite solution for 48 hours prior to use to dissolve attached soft tissue. Subsequently, when not being instrumented or obturated, teeth were stored in normal saline.

Endodontic preparation of the teeth For each tooth in Groups I, I1 and 111, a conventional standardized technique was used to prepare the root canals. The apical seat region of the root canal was enlarged three sizes beyond the first instrument which bound at the working length. A step-back technique was employed, using progressively larger K filestt at 1 mm intervals short of the working length until 3 mm short of the apical seat. Hedstroem files?? were then used to within 3 mm of the working length to ensure adequate flaring of the root canal preparation. Canals were irrigated after the use of each file, using a 1 per cent sodium hypochlorite solution. Instrumentation of the teeth in Group IVYwhich were to be obturated using thermoplastic injection of gutta percha (Ultrafil),** was carried out according to the directions of the manufacturer. After instrumenting with a size 20 K-type file, a step back technique was carried out to 3 mm short of the working length (with a 35 K file). The canal was then flared so that a size 70 K file could reach to within 6 mm of the apical seat. The aim of the instrumentation was to create an apical seat which could resist firm pressure from a No. 20 K file.” For teeth in all four groups, at the completion of instrumentation a size 10 K-type file was inserted 2 mm through the apical foramen to ensure a patent

1 Ransom & Randolph, Toledo, USA. lOsada Electrical Company Limited, Tokyo, Japan. “Hygenic Corp, Akron, OH, USA. ttMani, Nippon Shoji, Osaka, Japan. 440

foramenI2 so that a valid comparison of adaptation and seal could be made.

Obturation of the canals Teeth in Group I were obturated using a standard lateral condensation technique. Walls of the canal were coated with ProcoSol sealer$$ and a size 20 finger spreader with a sharpened tip was used to create space for accessory finelfine gutta percha points§§ (every third accessory point was coated with sealer). Teeth in Group I1 were obturated using McSpadden compaction according to the manufacturer’s instructions. The fitted master gutta percha point was coated with ProcoSo16 and seated to working length. A compactor, which reached to within 3 mm of the working length without bending, was selected and used at 10 000 rpm. The compactor was advanced about 6 mm into the canal to heat the gutta percha (until it was ‘fluid soft‘) and then advanced in one fluent motion to the predetermined length and withdrawn whilst still rotating. Teeth in Group I11 were obturated using the technique described by M0ren0.I~This is essentially a combination of both lateral and thermomechanical condensation. Rather than using a K-type file, the shaft of a No. 20 finger spreader was secured to the Enac handpiece. A master gutta percha point was checked for fit, the canal walls were coated with ProcoSol sealer and, after coating with sealer, the gutta percha was inserted to working length. The spreader was inserted to within 2 mm of the working length and ultrasonically activated. This causes the gutta percha to plasticize sufficiently to provide adaptation to the canal walls. Accessory gutta percha points were added to the canal and a size 20 finger spreader was used to condense the mass laterally. After every second accessory point, the Enac spreader was used to mould the points together into a more homogeneous mass. Teeth in Group IV were obturated using an injection system in which thermoplasticized gutta percha, at approximately 70 “C, was injected from a delivery gun through a 22 gauge needle into the canals which had not been coated with sealer. Immediately after obturation, gutta percha was heated out from all obturated teeth to within 6 mm of the apical seat. The remaining mass of gutta percha was vertically condensed with a plugger to ensure the maintenance of adaptation. Radiographs were obtained from both the facial and proximal aspects of each tooth to enable assess-

ffSyntex Dental Products Inc, Valley Forge, PA, USA. $$Progress, Sure Products Ltd, Seoul, South Korea. Australian Dental Journal 1992;37:6.

ment of the quality of the obturation. Teeth were stored for 24 hours at 37 "C and 100 per cent relative humidity to allow the sealer to set. All root surfaces except the apical 1 mm were covered with two coats of nail varnish. An additional four teeth were selected and biomechanically prepared, as for teeth in Groups I, I1 and 111, for use as controls. These teeth were not obturated. The root surfaces of two teeth (negative controls) were entirely covered with two coats of nail varnish. The root surfaces of the remaining two teeth (positive controls) were covered with two coats of nail varnish except for the apical 1 mm; that is, the foramen remained patent. Assessment of the adaptation and seal of the obturated root canals The obturated canals were assessed for adaptation of the root filling using three methods electrochemical leakage, linear dye penetration and radiographic evaluation. 1. Electrochemical leakage

After obturation, the teeth in each group were continuously tested for electrochemical leakage over a 30-day period. The method used to test for electrochemical leakage was based on that described by Jacobson and von Fraunhofer.8 A plastic basin was used to hold the electrolyte solution of 1 per cent KC1. One stainless steel electrode functioned as the cathode and individual copper electrodes were used as anodes. The copper electrodes were sharpened to enable insertion from the coronal aspect into the root canal and contact with the gutta percha. The teeth were attached on the copper electrodes with sticky wax. Radiographs were taken of the teeth to ensure that the copper electrodes were contacting the gutta percha. The electrical circuit was arranged so that the current was not interrupted when the readings were recorded. An adjustable transformerlrectifier was used to convert 240 volts of alternating current (AC) into direct current (DC) and, during the experiment, voltage was kept constant at 20 volts (DC). Leakage was measured in terms of the amount of current which flowed through the root canal. The current flow was measured daily in microamps (pA) with a multimeter.

2. Linear dye penetration Immediately after completion of the 30 days of continuous electrochemical leakage testing, the teeth were tested for dye penetration. The apical one-third of the root of each tooth was Australian Dental Journal 1992;37:6

immersed in 2 per cent methylene blue dye for 48 hours. After removal from the dye, teeth were washed under running tap water to remove excess dye and allowed to dry. The teeth were sectioned horizontally at the cemento-enamel junction with a tungsten carbide bur running at high speed. The roots were grooved longitudinally on the facial and lingual surfaces with a diamond disc and were then split longitudinally by wedging a scalpel blade into the grooved surface. The amount of linear dye penetration in an apical-coronal direction was assessed in millimetres under direct vision. The apical reference point was the apical seat. 3. Radiographic evaluation The two radiographs of each obturated canal were assessed at 2 x magnification using two clinically relevant parameters. The adaptation to the root canal wall was assessed as either Good (no voids present, the filling was well adapted to the canal wall and showed a dense appearance), or Acceptable (voids less than 0.5 mm in length were present in the body of the root filling and/or against the walls of the root canal), or Poor (voids more than 0.5 mm in length were present in the body of the root filling and/or against the walls of the root canal). The length of the root filling was assessed as either Optimal (gutta percha within 0.5 mm of the apical seat, with or without sealer overfill), or Short (the filling being at least 1 mm short of the apical seat), or Long (gutta percha through the apex).

Results The two positive controls (canals prepared, not obturated, foramen patent) exhibited high one-day leakage (2,220 pA and 3,670 pA) which decreased rapidly with time. By day 15, the leakage readings were 300 pA, and 350 PA, respectively. The two negative controls (canals prepared, not obturated, foramen coated with two layers of nail varnish) showed no evidence of electrochemical leakage during the period of testing. For each obturation technique, the mean daily readings of current flow (electrochemical leakage) for the ten teeth are shown in Table 1, and the number of teeth exhibiting electrochemical leakage (ECL) at particular times during the course of the 30-day period of continuous testing is shown in Table 2. Group I teeth, obturated by lateral condensation, exhibited very low average levels of leakage during the 30-day period (range from 0 pA to 0.07 pA) and on 17 of the days when readings were taken none of the ten teeth was leaking. 44 1

Table 1. Mean daily electrochemical leakage (ECL) readings for the ten teeth in each group Day number 1

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

ECL @A) for the ten teeth in each group Group I Group I1 Group I11 Group IV ~~ ~

mean sd* mean 0.01 0.01 0.01 0.01 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.02 0.05 0.05 0.07 0.07 0.07 0.07 0.05 0.05

0.02 0.02 0.02 0.02 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.04 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05

sd

mean

sd

mean

sd

2.87 2.80 0.98 1.70 0.25 0.21 2.85 3.70 0.82 1.20 0.09 0.18 5.23 9.50 0.79 0.90 0.08 0.18 9.20 18.90 0.82 0.80 0.05 0.09 5.20 11.30 0.69 0.60 0.03 0.05 2.08 4.20 1.10 1.20 0.02 0.04 1.43 2.30 0.58 0.45 0.04 0.09 0.38 0.50 0.53 0.35 0.05 0.09 0.34 0.40 0.65 0.50 0.04 0.09 0.30 0.30 0.99 1.50 0.02 0.04 0.19 0.20 1.65 2.10 0.02 0.02 0.21 0.28 2.49 3.20 0.03 0.05 0.21 0.28 0.97 1.10 0.02 0.02 0.14 0.18 0.80 0.90 0.02 0.02 0.14 0.18 0.59 0.50 0.03 0.05 0.15 0.18 0.56 0.40 0.02 0.04 0.17 0.15 0.47 0.30 0.02 0.05 0.19 0.15 0.59 0.40 0.01 0.02 0.15 0.15 0.47 0.28 0.02 0.02 0.11 0.15 1.93 2.50 0.02 0.02 0.10 0.12 1.84 2.40 0.02 0.02 0.12 0.15 1.89 2.90 0.03 0.03 0.11 0.12 1.73 2.30 0.04 0.06 0.14 0.15 1.45 1.90 0.04 0.06 0.20 0.25 1.19 1.20 0.05 0.09 0.25 0.44 1.06 1.10 0.05 0.09 0.30 0.50 0.97 1.00 0.06 0.10 0.27 0.50 0.93 0.90 0.05 0.09 0.25 0.50 0.92 0.90 0.03 0.04 0.24 0.50 0.93 1.00 0.03 0.04

~~

Table 2. Number of teeth for each obturation technique exhibiting electrochemical leakage (ECL) at times during the 30-day period of testing Number of teeth exhibiting ECL on particular days Obturation technique Day Day Day Day Day Day Day code (n = 10) 1 5 10 15 20 25 30 Group Group Group Group

I I1 I11 IV

3 10 9 8

0 5 8 5

0 3 9 4

0 3 8 4

0 3 8 3

1 4 8 4

1 4 8 5

measurements exhibited by the teeth in Groups I, 11, I11 and IV were 2.80 mm, 1.60 mm, 2.50 mm and 2.30 mm, respectively. The radiographic assessment, in addition to the clinically relevant view from the facial aspect, included also a radiograph taken from the proximal aspect. The evaluation of the two radiographs resulted in an assessment of the root canal filling’s adaptation and length. Findings are shown in Table 4. Differences among the obturation techniques, in the adaptation of the root filling, were relatively small. At least nine of the ten root canal fillings for each technique were rated as having good or acceptable adaptation. However, differences among the techniques in their ability to provide optimum control of length were statistically significant (Chi square test, I’< 0.05). The techniques coded I and I11 provided superior control of length of the root canal filling.

*Value for one standard deviation.

All Group. I1 teeth, obturated using the McSpadden compaction technique, leaked at day one. The average amount of leakage each day and the number of teeth leaking declined rapidly after day four and, after day nine, the average amount of leakage for the ten teeth did not exceed 0.3 pA. The Group I11 teeth, obturated using ultrasonically activated condensation, exhibited a relatively constant number of teeth (8 or 9) leaking during the 30-day period. The average daily leakage fluctuated between 0.47 pA and 2.49 pA. Group IV teeth, obturated using the thermoplasticized injection technique, showed low average levels of leakage during the 30-day period (range from 0.01 to 0.25 pA). The testing and assessment of the linear dye penetration was carried out after completion of 30 days’ electrochemical leakage testing. Findings are shown in Table 3. Average linear dye penetration 442

Discussion Compared with the positive controls, all obturated canals exhibited very low levels of leakage during the period of 30 days of continous electrochemical leakage testing. As measured by the number of days when no teeth were leaking and by the mean daily leakage readings, the adaptation achieved by the lateral condensation technique was comparable with or superior to the other three techniques. Results for all obturation techniques fluctuated both in the mean daily readings and in the number of teeth leaking. Mattison and von Fraunhofer’O noted variability among results for roots that were instrumented to the same degree and suggested that a similar effect might account for variability among sealed teeth. Direct comparison, among the various studies that have examined adaptation by electrochemical leakage, is difficult. Although most have tested the leakage over a period of 30 days, one study was Australian Dental Journal 1992;37:6.

Table 3. Linear dye penetration (LDP) Number of teeth Obturation Teeth exhibiting LDP (Distance from technique Teeth not exhibiting apical seat at which LDP first detected) code LDP l m m 2mm 3mm 4mm 5mm 6 m m Group I Group I1 Group 111 Group IV

1 4 1 2

3 2 2 2

1 0 3 3

0 2 1 1

3 2 1 0

1 0 2 0

1 0 0 2

conducted over 26 weeks." The number of teeth in each test group has varied from the comprehensive study by Delivanis and ChapmanY4which used 100 teeth, to a study which used four teeth for each set of test condition^.^ Most commonly, 10 to 14 teeth have been used for each set of One study4 examined lateral condensation alone, but other studies have examined variables in the vertical condensation te~hnique,~ the effect of two different sealers on the adaptation achieved with lateral condensation" or the sealing of canals filled only with sealer.'" No previous study has assessed a similar range of obturation techniques. Linear dye penetration (LDP) was examined after 30 days of continuous electrochemical leakage testing. The relatively poor LDP result for teeth obturated with lateral condensation may reflect some loss of ProcoSol sealer during the electrochemical leakage experiment.'" Mattison and von Fraunhofer'" observed that a significant amount of ProcoSol sealer dissolved during their electrochemical leakage testing. The teeth most likely to have been affected by any dissolution of sealer during electrochemical testing were those obturated by the lateral condensation technique in which not only were the canal wall and the master gutta percha point coated with sealer but a proportion of the accessory gutta percha points were also coated before insertion. Two studies8.'" reported an increase in electrochemical leakage between days 10 and 25 with particular sealers, including ProcoSol. This increase was attributed to the dissolution of some sealer. An examination of electrochemical leakage and linear dye penetration results suggests that, although sealer dissolution during electrochemical leakage testing may have contributed to the higher linear dye penetration for the lateral condensation group, this group of teeth still achieved a superior overall seal as measured by electrochemical leakage, despite any loss of sealer. Furthermore, there is no evidence to suggest that the electrochemical conditions generAustralian Dental Journal 1992;37:6.

Table 4. Radiographic assessment of adaptation and length of the root canal filling Number of teeth assessed with each rating Obturation Length technique code Adaptation (n = 10) Good Acceptable Poor Optimal Short Long Group Group Group Group

I I1

8 7

111

5

IV

6

2 2 4 3

0 1 1 1

1

0 6 9 3

0 2 1 5

0 2 0 2

ated in the electrochemical leakage technique normally operate in the clinical situation to dissolve sealer. In this study, linear dye penetration was examined after longitudinal sectioning of the roots. This has been a commonly used t e ~ h n i q u e * + ~ . ' ~ because the root filling remains intact and undisturbed until after the sectioning process has been completed. Multiple transverse sectioning of the root has also been a popular t e ~ h n i q u e , ' ~ ' ~because -'~ it enables the operator very easily to evaluate to what level dye penetration has o c ~ u r r e d . ~A. 'disadvantage ~ of the technique however is that the sectioning process produces a distorted root filling because the cutting blade heats and plasticizes the gutta p e r ~ h a . ' ~ , ' ~ The findings of the radiographic assessment clearly demonstrated the superior control of length of root fillings achieved with the lateral condensation technique and with the ultrasonic activation technique. It is, of course, possible that the operator's greater previous clinical experience with the lateral condensation technique influenced the results. The extent of this effect is difficult to assess. However, prior to the test specimens, the operator received training in and substantial practice in each technique with which he had not previously been familiar. It can probably best be stated that the operator, while most familiar with the lateral condensation technique, was probably more experienced with the other techniques than are many clinicians before they first use one of the alternative techniques. Beyer-Olsen et al. reported a significant association between the radiographically satisfactory root filling and resistance to leakage, although there were differences among materials. They suggested that, where the adaptation appears radiographically to be deficient, there may, in fact, be adequate material and that the radiopacity of the material in that section of the canal might be inadequate. The 443

finding, by ElDeeb et uZ.,'~ that there was a definite correlation between radiographic density and leakage, particularly in the middle one-third of the root canal, may not be applicable to this study where only the apical 6 mm of the root filling was left in the canal. Conclusions In this study the adaptation and seal achieved by four techniques of obturation were assessed using three methods. 1. Using the electrochemical technique for assessing leakage, differences among the four obturation techniques were relatively small although the lateral condensation technique more frequently produced canals exhibiting no leakage. 2. Results for linear dye penetration may have been influenced by the prior testing for electrochemical leakage which, it has been suggested, may cause dissolution of some sealer. 3. Differences among obturation techniques, for the adaptation evident on radiographs, were small. The lateral condensation technique and the ultrasonic activation technique, which is essentially a combination of both lateral and thermomechanical condensation, exhibited superior control of the length of the root filling. 4. Despite considerable pre-test training, the findings may have been influenced by the operator's greater clinical experience in the use of the lateral condensation technique. Acknowledgement The authors wish to acknowledge the support received from the Australian Dental Research Fund Inc. and Westmead Hospital Dental Clinical School in this research.

4. Delivanis PD, Chapman KA. Comparison and reliability of techniques for measuring leakage and marginal penetration. Oral Surg Oral Med Oral Pathol 1982;53:410-6. 5. Zakariasen KL, Stadem PS. Microleakage associated with modified eucapercha and chloropercha rootcanal-filling techniques. Int Endod J 1982;15:67-70. 6. Ishley DJ, ElDeeb ME. An in vitro assessment of the quality of apical seal of thermomechanically obturated canals with and without sealer. J Endod 1983;9:242-5. 7. Mann SR, McWalter GM. Evaluation of apical seal and placement control in straight and curved canals obturated by laterally condensed and thermoplasticized gutta percha. J Endod 1987;13:10-7. 8. Jacobson SM, von Fraunhofer JA. The investigation of microleakagein root canal therapy. Oral Surg Oral Med Oral Pathol 1976;42:817-23. 9. Osins BA, Carter JM, Shih-Levine M. Microleakage of four root canal sealer cements as determined by an electrochemical technique. Oral Surg Oral Med Oral Pathol 1983;56:80-7. 10. Mattison GD, von Fraunhofer JA. Electrochemical microleakage study of endodontic sealerkements. Oral Surg Oral Med Oral Pathol 1983;55:402-7. 11. Lim KC, Tidmarsh BG. The sealing ability of Sealapex compared with AH26. J Endod 1986;12:564-6. 12. George JW, Michanowicz AE, Michanowicz JP.A method of canal preparation to control apical extrusion of lowtemperature thermoplasticized gutta-percha. J Endod 1987;13: 18-23. 13. Moreno A. Thermomechanically softened gutta percha root canal filling. J Endod 1977;3:186.8. 14. Zmener 0. Evaluation of the apical seal obtained with two calcium hydroxide based endodontic sealers. Int Endod J 1987;20:87-90. 15. Kerekes K, Rowe AHR. Thermo-mechanical compaction of gutta percha root filling. Int Endo J 1982;15:27-35. 16. Santini A. Obturation of root canals by the standardized and step back techniques. Endod Dent Traumatol 1987;3:68-74. 17. Beyer-Olsen EM, 0rstavik D, Eriksen HM. Radiographic voids and leakage along root fillings in vitro. Int Endod J 1983; 16151-8. 18. Kersten HW, Fransman R, Thoden Van Velzen SK. Thermomechanical compaction of gutta percha. 1. A comparison of several compaction procedures. Int Endod J 1986; 19:125-33. 19. ElDeeb ME, Zucker KJ, Messer H. Apical leakage in relation to radiographic density of gutta percha using different obturation techniques. J Endod 1985;11:25-9.

References 1. Ingle JI, Glick DH. Modern endodontic therapy. In: Ingle JI, ed. Endodontics. Philadelphia: Lea and Febiger, 196564. 2. Grieve AR. Sealing properties of cements used in root filling. Br Dent J 1972;132:19-22. 3. Barry GN, Fried IL. Sealing quality of two polycarboxylate cements used as root canal sealers. J Endod 1975;l: 107-11.

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Address for correspondenceheprints: Associate Professor Roland W. Bryant, Department of Operative Dentistry, The University of Sydney, C/o Westmead Hospital Dental Clinical School, Westmead, New South Wales, 2145.

Australian Dental Journal 1992:37:6.

The adaptation achieved by four root canal filling techniques as assessed by three methods.

Four root canal filling techniques--lateral condensation, McSpadden compaction, ultrasonic activation (Enac), and thermoplastic injection (Ultrafil)--...
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