A comparative study of lateral condensation, heat-softened gutta-percha, and a modified master cone heat-softened backfilling technique

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1 A comparative study of lateral condensation, heat-softened gutta-percha, and a modified master cone heat-softened backfilling technique D. Da Silva 1,U.Endal 1, A. Reynaud 1,I.Portenier 1,D.Òrstavik 2 &M.Haapasalo 1 1 Department of Endodontics, Dental Faculty, University of Oslo, Oslo; and 2 NIOM, Scandinavian Institute of Dental Materials, Haslum, Norway Abstract DaSilvaD,EndalU,ReynaudA,PortenierI,Òrstavik D, Haapasalo M. A comparative study of lateral condensation, heat-softened gutta-percha, and a modified master cone heat-softened backfilling technique. International Endodontic Journal, 35, 1005 ^1011, Aim The aim of the study was to compare the quality of root llings completed by lateral condensation (LC), Therma l (TF), and a newtechnique using Therma l for back lling (BF), with special emphasis on control of over lling. Methodology Sixty curved canals in plastic blocks were prepared with the ProFile system to size 40/04 taper in the apical half and to 06 taper in the coronal half. The canals were divided into three groups of 20. Apical patency was veri ed with a size 15 K- le. The canals were then lled using three di erent techniques: LC (20 canals), TF (20 canals), and BF, where a size 40 master point with sealer was seated prior to the introduction of a size 30 Therma l point (20 canals). The same resin-based sealer was used on each occasion. The root llings were assessed using stereomicroscopy for material extrusion, digital radiography for occurrence of voids, and microscopy of sections for voids and thickness of sealer layer. Results Extrusion of both gutta-percha and sealer occurred in all 20 canals lled with the TF technique, but only three and ve cases of sealer extrusion were detected with LC and BF techniques, respectively. No voids were detected in the TF group, whereas small voids were present in most llings in the LC and BF groups. The average total length of the voids was less than 1 mm per canal. The thickness of the sealer layer in the middle and apical parts was greater in the LC and BF groups than in the TF group. Conclusions LC and BF techniques resulted in fewer over lls than TF. Voids were absent in TF llings, whilst small voids were found in the LC and BF groups. Keywords: back lling, lateral condensation, over lling, root lling, warm gutta-percha. Received 2 January 2002; accepted 23 August 2002 Introduction Root lling, particularly of curved canals, is often regarded as technically demanding and di cult. This is re ected by the high number of existing root- lling techniques and by the frequency of newtechniques being developed. Heat-softened gutta-percha on a solid carrier is a method that has rapidly gained popularity. It is an Correspondence: Dr Markus Haapasalo, Department of Endodontics, Dental Faculty, PO Box 1109, Blindern, N-0317 Oslo, Norway (Tel.: þ ; fax: þ ; haapasal@odont.uio.no). easy and rapid technique. The quality of root llings produced in this way, including apical and coronal leakage has been evaluated ina number of studies during the last 15 years (Lares et al. 1990, Gencoglu et al.1993a, Gutmann et al. 1993a,b, Bhambhani & Sprechman 1994, Dalat & Spangberg 1994, Dummer et al. 1994, Hata et al. 1995,Weller et al. 1997,Taylor et al. 1997, Gulabivala et al. 1998, Lee et al. 1998, Cohen et al. 1999, Kytridou et al. 1999). Although the methods used as well as the design of the carriers has varied between the di erent studies, there seems to be agreement that the method is simple to use and produces root llings of good quality ß 2002 Blackwell Science Ltd International Endodontic Journal, 35, 1005^1011,

2 Thermafil backfilling technique Da Silva et al. (Dummeret al.1993, Gencoglu et al.1993b, Gutmann et al. 1993b, Dummer et al. 1994, Leung & Gulabivala 1994, Gulabivala et al. 1998). However, the majority of studies where over lling has been addressed, indicate that the possibility of extrusion of gutta-percha/sealer is higher than with several other methods, including lateral condensation (Clark & ElDeeb1993, Dummer et al.1993, Gutmann et al.1993b, Kytridou et al. 1999). Combining the speed and ease of the softened gutta-percha methodwith the apical precision of a master cone would seem advantageous. Therefore, the aim of the present study was to evaluate a back lling technique with Therma l in comparison with lateral condensation and Therma l, with special emphasis on the occurrence and control of over- lling and voids. Materials and methods Preparation Sixty plastic blocks (Endo-training-block 015_035, Maillefer, Ballaigues, Switzerland) with curved canals 17 mm in length were prepared with the ProFile system (Maillefer) to size 04/40 in the apical canal. The largest instrument, ProFile 06/40, was used to 14 mm (3 mm short of preparation length). The taper of the prepared canals was 04 between D0 (0.40 mm) and D9 (0.76mm),and06betweenD9andD17(1.24mm).The following ProFile instruments were used in order: 06/ 40(OS3),06/30(OS2),06/25,04/25,06/20,04/30,04/35, 06/40, 04/40. The same instrument set was used to prepare ve canals. A micromotor (Tecnica, ATR srl, Pistoia, Italy) was used at 300 r.p.m. with pre-programmed settings for the various instrument sizes, as recommended by the manufacturer. Apical patency after ProFile preparation was ensured with a size 15 hand K- le (Maillefer). Root lling The canals were examined under a stereomicroscope (Olympus SZ40, Olympus Optical,Tokyo, Japan) at a magni cation of 10 for the quality of the preparations. The criteria for acceptable preparations were: absence of steps, transportation of the canal and overinstrumentation that would result in a poorer apical stop. The canals were then divided into three groups of 20 each and coded randomly. The canals were then lled using one of the three di erent techniques: Therma l (TF group, 20 canals) (Maillefer), back lling with Therma l (BF group, 20 canals), and lateral condensation (LC group, 20 canals). An oven (Thermaprep Plus, Maillefer) was used to soften the gutta-percha on the Therma l points as recommended by the manufacturer. In the TF group, a thin layer of sealer (AH Plus, Dentsply,Tulsa, USA) was applied to the canal walls with a size 35 paper point (taper.02, Maillefer), before lling with a size 40 TF point (taper.04) following the manufacturers instructions. Excess coronal gutta-percha and the plastic handle were removed with a round bur (ISO 016, Maillefer) at 2000 r.p.m. without water cooling, and the gutta-percha was vertically condensed with pluggers (model LM 41^42 XSi, LM-Dental, Naantali, Finland). In the BF group, a gutta-percha master point (ISO size 40, taper.02, Maillefer), coated with sealer (AH Plus, Dentsply) was rst introduced into the canal. The master point was condensed with a size C nger spreader (Maillefer), and atherma l point size 04/30 was used for back- lling of the canal. Excess coronal gutta-percha and the plastic handle were removed with a round bur and the root lling was vertically condensed as with TF. In the LC group, a master point size 02/40 (Maillefer), coated with sealer (AH Plus, Dentsply) was introduced into the canal, condensed with nger spreader C (Maillefer, Dentsply) followed by three accessory gutta-percha points of size C (Maillefer) with sealer. Excess guttaperchawas removed using awarm excavator, and the lling was vertically compacted as above. Assessment of the root llings The presence orabsence of extruded sealer/gutta-percha through the apical opening was assessed through a stereo microscope at a magni cation of 10 (Olympus SZ40, Olympus Optical). The quality of the root llings was assessed on digital radiographs (CCD sensor, 0.04 s, 70 kv) (RVGui, Trex-Trophy Radiology Inc., Marne-la-Valle e, France) studied on a computer screen. Two projections with a 908 di erence were used for each lling. The occurrence of voids in the apical, middle and coronal third of the root lling was registered and the total length (SD) of the voids per canal was measured to the nearest 0.5 mm. The blocks were cut into four sections under water cooling (Accutom, Struers, Denmark) that allowed the cross-section of six surfaces in each root lling to be evaluated.the sectioning levels are indicated in Fig. 1. A light microscope (Leitz Aristoplan, LeitzWetzlar, Oberkochen, Germany) was used at a magni cation of 25 under re ected light.the sections were studied for the presence of voids and sealer International Endodontic Journal, 35, 1005^1011, 2002 ß 2002 Blackwell Science Ltd

3 Da Silva et al. Thermafil backfilling technique 2; Fig. 2). Over lling with gutta-percha was not found inanyof the specimens inthe LC and BFgroups; however, extrusion of sealer was detected in ve canals in the BF group and three in the LC group (Table 1; Figs 3^5). The risk for over lling with either gutta-percha or sealer was statistically signi cantly (P ¼ 0.000) higher in the Therma l group than in the two other groups (Table 2). No di erences could be detected between the LC and BF groups (Table 2). Voids Radiographic evaluation by digital radiography of the llings revealed no voids in thetf group, whereas small voids were present in 18 and 19 of the 20 llings in the LC and BF groups, respectively (Tables 1 and 2; Figs 4 and 5). The average total length of the voids (SD) per canal was mm for the LC group and 0.6 Figure 1 Sectioning of the root lled plastic block. The sections were done 2,7 and12 mm from the apex. Ca.1 mm was lost in each section because of the thickness of the cutting blade. Statistical analysis Fisher s exact tests (two-sided) were used to assess the probability of a hypothesis of no di erence between the back lling with Therma l versus thetherma l and versus the lateral condensation technique. Table 1 The occurrence of over lling and voids with the three techniques Overfilling with gutta-percha Overfilling with sealer Voids Thermafil 20/20 20/20 0/20 BackfillThermafil 0/20 5/20 19/20 Lateral condensation 0/20 3/20 18/20 Table 2 Statistical evaluation of the hypothesis of no di erence between the lling techniques (Fisher s exact tests, two-sided) Results Overfilling with gutta-percha Overfilling with sealer Voids Extrusion of root- lling material Over lling with both gutta-percha and sealer was detected in all 20 canals in the TF group (Tables 1 and Backfill withthermafil vs.thermafil Backfill withthermafil vs. lateral condensation P ¼ P ¼ P ¼ P ¼ 1 P ¼ 0.69 P ¼ 1 Figure 2 (A, B) A radiograph showing two plastic canals lled with thetf technique. Projections A and B are taken at 08 and 908. Note the high quality of the lling in the canal where no voids can be detected. Apical extrusion of the root lling is evident. ß 2002 Blackwell Science Ltd International Endodontic Journal, 35, 1005^1011,

4 Thermafil backfilling technique Da Silva et al. 0.3 mm for the BF group.the majority of the voids (71%) were in the middle part of the root lling, whilst 12% were in the apical lling and 17% in the coronal lling. The risk of voids was statistically signi cantly lower (P ¼ 0.000) inthetfgroup than inthe LC and BF groups. No di erences could be detected between the LC and BF groups (Table 2). In the BF technique, sections studied with the microscope revealed no gaps between the master cone and thetherma l plastic core or thetherma l gutta-percha (Fig. 6). Sealer Figure 3 Minor apical extrusion of sealer was detected in some canals lled with the BFand LC techniques. Sections studied under the microscope showed no gaps between the root llings/sealer and the canal wall in any of the three groups. In TF llings, no sealer could be seen under the microscope. In the LC and BF groups, the sealer layer was thickest in the lower middle third of the canal, usually between 10 and 100 mm. Voids demonstrated in the radiographs were also veri ed in Figure 4 (A, B) A radiograph showing two plastic canals lled with the BF technique. Despite apical patency, no extrusion of the root- lling material canbe seen. Smallvoids canbe seen in the root lling (arrows). Figure 5 (A, B) A radiograph showing plastic canals lled with the LC technique. Small voids can be seen in the root lling (arrows) International Endodontic Journal, 35, 1005^1011, 2002 ß 2002 Blackwell Science Ltd

5 Da Silva et al. Thermafil backfilling technique Figure 6 Across-section of a BF lling. Master point (MP),Therma l plastic core (TF-core), gutta-percha from the Therma l point (TF-GP) and sealer are seen in the section, level 2a (see Fig. 1). the sections studied with the microscope when the sectioning had occurred through such an area. The voids were typically located between the canal wall and the gutta-percha; however, a thin but continuous layer of sealer was seen covering the canal wall (Figs 7 and 8). Figure 7 Avoid (shown in Fig. 5A, right arrow) between the sealer and the gutta-percha in a LC lling (section level 3b, see Fig.1). Discussion A modi cationof the lateral condensation method witha Therma l back lling technique was presented and evaluated in this study. The newtechnique can be regarded as a combination of the lateral condensation and the Therma l techniques with the goal being to add the ease of use of the TF technique to the successful control of the length of the root lling in the master cone/lc technique. Extrusion of gutta-percha and/or sealer is frequently seen in vivo in connection with TF. In the present study, all TF llings produced over lling with both sealer and gutta-percha. However, these in vitro observations in the plastic canals cannot be regarded as directly representative of the clinical situation. Apical patency with size15 K- le was established after the canal preparation, whereas in the clinical situation, apical patency cannot always be obtained. Moreover, resistance by the periapical tissues and tissue pressure in the in vivo situation may reduce the occurrence/extent of over lling, although the exact e ect of these variables is di cult to determine. Inpreliminaryexperiments with extracted teeth, less over lling with the Therma l technique was observed than in the present study with standardized simulated canals (data not shown). Similarly, pilot experiments to the present study, where apical patency was not established with the small K- les, showed that ß 2002 Blackwell Science Ltd International Endodontic Journal, 35, 1005^1011,

6 Thermafil backfilling technique Da Silva et al. Figure 8 Avoid (shown in Fig. 4A, arrow) between the sealer and the gutta-percha in a BF lling (section level 3a, see Fig. 1). over lling with TF seldom occurred. This can be explained through the packing of plastic chips at the apical foramen during preparation. Packing of dentine chips has been suggested in vivo for better control of over lling when using the TF technique (Scott & Vire 1992). However, dentine chips may contain infectious or antigenic material, and therefore, apical packing of dentine chips should be considered only in vital cases. The present study showed clearly that under the experimental conditions employed, the possibility of over lling was greatly reduced with the back lling technique and was similar to lateral condensation. Although the warm gutta-percha from the TF points seamlessly united with the gutta-percha of the master point as seen in the sections studied under the microscope, the heat capacity of the intruding warm gutta-percha was not high enough to cause melting of the master cone in the apical portion, which could have resulted in extrusion of the lling material. Moreover, no sealer was extruded from the canal during lling. Radiographic analysis of the root llings demonstrated good adaptation of the TF llings to the canal walls in all parts of the canal. However, visual observations made during lling emphasized the importance of vertical compaction.vertical condensation had a clear e ect on the root lling down to the apical part of the canal, but did not, in any case, cause more extrusion of the root lling. Small voids were detected in both LC and BF llings. The total number of voids was 42 in 40 canals,0^2 voids per canal. However, the size of the voids was small, and their average total length per canal was less than 1 mm. It seems that voids were created as a result of air being trapped in the lling after the apical opening was sealed with the mastercone in the LC and BF techniques. The voids in the sealer were typically trapped between the gutta-percha and the canal wall. However, also in such areas, a thin and continuous layer of sealer was seen covering the canal wall resin. In order to measure the volume of the voids, pilot experiments were completed using a micro CT-scan technique. However, the resolution and sensitivity of the method was not su cient to detect the voids that were seen on radiographs and veri ed by stereo microscopy of thin sections. The BF technique was easy to use and the lling was completed quickly. In the TF technique, the sealer was introduced into the canal with a paper point, whereas in the BF technique, the master gutta-percha point was used. The only additional step in the BF technique compared to TF alone was the condensation of the master gutta-percha point with the spreader before introducing 1010 International Endodontic Journal, 35, 1005^1011, 2002 ß 2002 Blackwell Science Ltd

7 Da Silva et al. Thermafil backfilling technique the Therma l point. In the model used in the present study, BF gave full control of over lling and was an acceptable alternative totf technique.the present study was completed in standardized plastic canals with round cross-sections; further studies are required to determine the suitability of the BF technique in natural root canals. Acknowledgements We thank Dr AsbjÖrn Jokstad, Oslo, for help in statistical analysis. This work was supported in part by Maillefer Dentsply, Switzerland. References Bhambhani SM, Sprechman K (1994) Microleakage comparison of therma l versus vertical condensation using two di erent sealers. Oral Surgery, Oral Medicine and Oral Pathology 78, 105^8. Clark DS, ElDeeb ME (1993) Apical sealingabilityof metalversus plastic carrier Therma l obturators. Journal of Endodontics 19,4^9. Cohen BI, Pagnillo MK, Musikant BL, Deutsch AS (1999) The evaluation of apical leakage for three endodontic ll systems. General Dentistry 46, 618^23. Dalat DM, Spangberg LS (1994) Comparison of apical leakage in root canals obturated with various gutta-percha techniques using a dye vacuum tracing method. Journal of Endodontics 20, 315^9. Dummer PM, Kelly T, Meghji A, Sheikn I,Vanitchai JT (1993) An in vitro study of the quality of root llings in teeth obturated by lateral condensation of gutta-percha or Therma l obturators. International EndodonticJournal 26,99^105. Dummer PM, Lyle L, Rawle J, Kennedy JK (1994) A laboratory study of root llings in teeth obturated by lateral condensation of gutta-percha or Therma l obturators. International EndodonticJournal 27,32^8. Gencoglu N, Samani S, Gunday M (1993a) Evaluation of sealing properties of Therma l and Ultra l techniques inthe absence or presence of smear layer. Journal of Endodontics19,599^603. Gencoglu N, Samani S, Gunday M (1993b) Dentinal wall adaptation of thermoplasticized gutta-percha in the absence or presence of smear layer: a scanning electron microscopic study. Journal of Endodontics19, 558^62. Gulabivala K, Holt R, Long B (1998) An in vitro comparison of thermoplasticized gutta-percha obturation techniques with cold lateral condensation. Endodontics and Dental Traumatology14, 262^9. Gutmann JL, SaundersWP, Saunders EM, Nguyen L (1993a) An assessment of the plastic Therma l obturation technique. Part 2. Materialadaptationand sealability. InternationalEndodonticJournal 26, 179^83. Gutmann JL, SaundersWP, SaundersWP, Nguyen L (1993b) An assessment of the plastic Therma l obturation technique. Part1. Radiographic evaluation of adaptation and placement. International EndodonticJournal 26,173^8. Hata G, Kawazoe S,TodaT,Weine FS (1995) Sealingabilityof thermoplasticized gutta-percha ll techniques as assessed by a newmethod of determining apical leakage. Journal of Endodontics 21, 167^72. KytridouV, Gutmann JL, Nunn MH (1999) Adaptation and sealability of two contemporary obturation techniques in the absence of the dentinal smear layer. International Endodontic Journal 32,464^74. Lares C, eldeeb ME (1990) The sealing ability of Therma l obturation technique. Journal of Endodontics16, 474^9. Lee CQ, Cobb CM, Robinson SJ, Lamartina T,Vo T (1998) In vitro evaluation of the Therma l technique with and without gutta-percha coating. General Dentistry 46,378^81. Leung SF, Gulabivala K (1994) An invitro evaluation of the in uence of canal curvature on the sealing ability of Therma l. International EndodonticJournal 27,190^6. Scott AC,Vire DE (1992) An evaluation of the ability of a dentin plug to control extrusion of thermoplasticized gutta-percha. Journal of Endodontics 18,52^57. Taylor JK, Jeansonne BG, Lemon RR (1997) Coronal leakage: e ects of smear layer, obturation technique, and sealer. Journal of Endodontics 23,508^12. Weller RN, KimbroughWF, Anderson RW (1997) A comparison of thermoplastic obturation techniques: adaptation to the canal walls. Journal of Endodontics 23,703^6. ß 2002 Blackwell Science Ltd International Endodontic Journal, 35, 1005^1011,