Sealing Ability of a New Polydimethylsiloxane-based Root Canal Filling Material

Sealing Ability of a New Polydimethylsiloxane-based Root Canal Filling Material

Basic Research—Technology Sealing Ability of a New Polydimethylsiloxane-based Root Canal Filling Material Ahmet R. Özok, PhD, Lucas W. M. van der Slu...

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Basic Research—Technology

Sealing Ability of a New Polydimethylsiloxane-based Root Canal Filling Material Ahmet R. Özok, PhD, Lucas W. M. van der Sluis, PhD, Min-Kai Wu, PhD, and Paul R. Wesselink, PhD Abstract We tested the null hypothesis that there is no difference in the sealing ability of GuttaFlow, RoekoSeal, and AH26 in root canals. Sixty extracted mandibular premolars were filled with AH26 (lateral compaction), RoekoSeal, or GuttaFlow (modified single-cone). The sealing ability of the root canal fillings was measured weekly (4 weeks) by using a glucose penetration model. Kruskal-Wallis test revealed significant differences in glucose penetration between the experimental groups at weeks 1, 2, 3, and 4. Whereas GuttaFlow showed the highest amount of leakage at all times, AH26 showed the lowest. There was no significant difference between RoekoSeal-filled and AH26-filled root canals throughout the experimental period. AH26 showed better sealing ability in root canals than GuttaFlow. (J Endod 2008;34:204 –207)

Key Words AH 26, GuttaFlow, leakage, polyvinlysiloxane, RoekoSeal, root canal filling material, sealing ability

From the Department of Cariology Endodontology Pedodontology, Academic Center for Dentistry Amsterdam (ACTA), Amsterdam, The Netherlands. Address requests for reprints to Ahmet R. Özok, PhD, Department of Cariology Endodontology Pedodontology, Academic Center for Dentistry Amsterdam (ACTA), Louwesweg 1, 1066 EA Amsterdam, The Netherlands. E-mail address: [email protected] acta.nl. 0099-2399/$0 - see front matter Copyright © 2008 by the American Association of Endodontists. doi:10.1016/j.joen.2007.11.005

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he major goal of a root canal filling is to prevent (re)infection of the root canal via leakage of microorganisms and their by-products. The sealing ability of a root canal filling material is, therefore, an important factor in achieving this goal. A new glucose penetration method (1, 2) appears to be a useful tool to quantitatively, nondestructively, and longitudinally measure the sealing ability of root canal filling materials. The sealing ability of Roekoseal (Coltène/Whaledent, Langenau, Germany), a polydimethylsiloxane-based root canal filling material, in combination with single-cone technique (3) or in combination with cold lateral compaction technique (4, 5), appears favorable. RoekoSeal expands by 0.2% during the first 4 weeks and remains stable thereafter (6). This feature might improve its sealing ability without forming excessive forces within the root canal. RoekoSeal is considerably less cytotoxic than epoxy resin– based root canal sealers, AH Plus (Dentsply/DeTrey, Konstanz, Germany) (7) and Top Seal (Dentsply/De Trey) (8), and has little apoptotic effect on cells exposed to it (9). A new polydimethylsiloxane-based root canal filling material, GuttaFlow (Coltène/ Whaledent), has the same composition as RoekoSeal, except for the added gutta-percha (⬍30 ␮m) and nanosilver particles. It has been introduced to the market as the first nonheated, flowable gutta-percha that, unlike heated gutta-percha, does not shrink. According to the manufacturer, GuttaFlow has excellent flow properties because its viscosity diminishes under shear stress (thixotropicity). GuttaFlow has similar cytotoxicity to Teflon controls at 24 hours after mixing (10), which increases over time (72 hours); however, it remains significantly less than that of AH Plus. We tested the null hypothesis that there is no difference in sealing ability between root canals filled with GuttaFlow or RoekoSeal in combination with a modified singlecone technique or with AH26 in combination with cold lateral compaction technique.

Material and Methods Seventy recently extracted human mandibular premolars with single canal and stored in 0.01% sodium azide (NaN3) were used. All the teeth had closed apices, no cracks, and no signs of excessive aging. On buccolingual and mesiodistal radiographs of the teeth, which were taken to exclude the presence of a second canal, the canal diameters at the apical 4 mm were measured. The teeth were then distributed among the experimental groups (groups 1–3) (n ⫽ 20) and the negative control group (n ⫽ 10), according to the average canal diameter. A Kruskal-Wallis test showed no statistically significant difference between the groups regarding their average diameters (P ⫽ .999).

Preparation of the Specimens The teeth were embedded in self-polymerizing methyl methacrylate resin cylinders (Dentimex, Zeist, Netherlands), leaving the apical one third of the root uncovered, and were decoronated at 14 mm from the apex. The margins adjoining the root and resin were sealed with cyanoacrylate glue (Permacol, Ede, Netherlands). Except for the apical foramen and the coronal access, the whole specimen surface was covered with 2 layers of nail varnish. In the controls, the whole surface was covered. The samples were kept at 37°C and 100% humidity at all times.

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Basic Research—Technology (Henry Schein, Gillingham, UK) was lightly coated with the AH26 paste and inserted into the canal to working length. With a spreader size B and 8 –10 size 25 cones, the root canals were filled (cold lateral compaction).

Group 2 RoekoSeal (Lot 008, 2008-08) was mixed according to the manufacturer’s recommendations and introduced into the root canals with lentulo spirals rotating slowly to 1 mm short of the working length. A size 30 gutta-percha master cone at working length and then two size 25 gutta-percha cones were inserted passively (modified single-cone). Group 3 GuttaFlow (Lot 106027, 2006-09) was mixed on a Silamat S5 (Vivadent, Schaan, Liechtenstein) according to the manufacturer’s recommendations. The canals were filled with GuttaFlow in the same manner as described in group 2. In a pilot study, root canals filled with gutta-percha cones without any sealer and any warm vertical forces were used as positive controls. These samples exhibited substantial amount of leakage within the first week. Root canals filled in the same manner as described in group 1 were completely sealed with nail varnish (including the apical foramen and the coronal access) to serve as negative controls. Figure 1. Schematic drawing of the glucose penetration setup used to measure the sealing ability of the root canal filling materials in the present study.

Instrumentation and Obturation of the Root Canals A size 15 K-file was inserted in the root canal until it was just visible at the apical foramen. The root canals were prepared 1 mm short of this length by using GT-rotary instruments (Dentsply Maillefer, Ballaigues, Switzerland) to a 0.06 taper master apical size of 30. After each instrument size, canals were rinsed with 2 mL 2% sodium hypochlorite (NaOCl). After completion of the preparations, the canals were also rinsed with 2 mL 2% NaOCl, a size 15 K-file was inserted in the root canal, and the remaining irrigant was ultrasonically activated (P5-Suprasson; Satelec, Merignac, France) (1 minute). The canals were then flushed with 0.5 mL 17% ethylenediaminetetraacetic acid solution (1 minute). Subsequently, the canals were rinsed with 2 mL NaOCl, deionized water, and 80% ethanol, respectively, and dried with paper points. The patency of the apical foramen was ascertained by inserting the tip of a size 15 file through it. Group 1 AH26 (Lot 0411000575, 2009-10) was mixed according to the manufacturer’s recommendations. A size 30 gutta-percha master cone

Measurement of the Sealing Ability We used a modified glucose penetration setup (1, 2). Briefly, the specimen was connected to a 16-cm-long glass pipette (Pyrex, Acton, MA) via a silicon-rubber tube and stainless steel wires (Fig. 1). The assembly was then placed in a sterile bottle with a screw cap. An open system was created by drilling a uniform hole in the screw cap. The upper chamber contained 14 cm of 1 mol/L glucose and 0.02% NaN3 solution (approximately 4.5 mL), which created a hydrostatic pressure of 1.5 kPa (2). Lower chamber contained 2 mL 0.02% NaN3 solution. The whole setup was stored in a closed jar (100% humidity, 37°C) throughout the experiment. On days 7, 14, 21, and 28, a 100-␮L aliquot from the lower chamber was taken, and 100 ␮L sterile NaN3 solution was added. The glucose concentration (g/L) in the aliquot was measured with a glucose assay kit (D-glucose-HK; Megazyme, Wicklow, Ireland) and a spectrophotometer (Spectramax plus; Molecular Devices, Sunnyvale, CA) at 340 nm wavelength. In a pilot study, triplicate measurements were reproducible (with differences at the third decimal); therefore, here the measurements were taken only once. The glucose assay has a lower detection limit of 0.04 g/L. The values below this were considered unreliable and recorded as 0 (no leakage). Similarly, once leakage exceeded 0.8 g/L, samples were no longer observed because the glucose concentration in the lower chamber suggested substantial leakage had occurred.

TABLE 1. Mean (standard deviation [SD]) and Median (range) of Glucose Penetration (g/L) along the Root Canal Filling Group AH26 Mean (SD) Median (range) RoekoSeal Mean (SD) Median (range) GuttaFlow Mean (SD) Median (range)

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Week 1

2

3

4

0.02 (0.06) 0.0 (0–0.2)

0.1 (0.2) 0.0 (0–0.8)

0.2 (0.3) 0.0 (0–0.8)

0.2 (0.3) 0.0 (0–0.8)

0.08 (0.2) 0.0 (0–0.6)

0.2 (0.3) 0.0 (0–0.8)

0.2 (0.3) 0.0 (0–0.8)

0.3 (0.3) 0.0 (0–0.8)

0.3 (0.4) 0.0 (0–0.8)

0.4 (0.4) 0.2 (0–0.8)

0.5 (0.4) 0.8 (0–0.8)

0.5 (0.4) 0.6 (0–0.8)

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Figure 2. Mean glucose penetration along the root canal filling per group over time.

Statistical Analysis Data were analyzed on SPSS 12.0.1 software for Windows (SPSS Benelux, Gorinchem, Netherlands). A Kruskal-Wallis test assessed overall differences between the groups. Once overall differences were observed, pair-wise comparisons were performed with a Mann-Whitney U test. We considered values of P ⬍ .05 as significant.

Results The results are summarized in Table 1. Fig. 2 shows the mean glucose penetration in root-filled teeth. Negative control specimens showed no detectable glucose penetration for 4 weeks. The differences between the groups at weeks 1, 2, 3, and 4 were significant (P ⫽ .022, .034, .002, and .026, respectively). No significant difference in glucose penetration between root canals filled with AH26 or RoekoSeal was found throughout the experi-

mental period. AH26 showed significantly less glucose penetration than GuttaFlow throughout the experiment (at weeks 1, 2, 3, and 4) (P ⫽ .010, .018, .004, and .008, respectively). At weeks 1, 2, and 4, there was no statistically significant difference between RoekoSeal-filled and GuttaFlow-filled root canals. At the third week, RoekoSeal showed significantly less glucose penetration than GuttaFlow (P ⫽ .004). GuttaFlow showed the highest amount of glucose penetration at all time points. The percentages of specimens with detectable glucose penetration to the whole group are shown in Fig. 3. At weeks 1 and 2, no significant difference was observed in the percentage of root canal fillings with glucose penetration between the groups. At week 3, both AH26 and RoekoSeal groups had significantly lower percentage of specimens with glucose penetration than GuttaFlow (P ⫽ .030). At week 4, only AH26 showed significantly less percentage of specimens than GuttaFlow (P ⫽ .030). Throughout the experiment, no significant difference between

Figure 3. Percentage of specimens with detectable glucose penetration along the root canal filling. Bars with the same superscript letters are not statistically significantly different (P ⬎ .05).

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Basic Research—Technology AH26 and RoekoSeal groups in percentage of specimens with glucose penetration was observed.

Discussion

increased possibility of communication between these voids and the apical and coronal ends of the root canal filling. They also observed that in this group the voids were almost always within the sealer itself but not at the sealer-dentin interface. The porosity of the sealer might be a result of using a lentulo spiral to place the highly viscous gutta-percha paste into the canal or simply because of the manufacturing process. In this in vitro study, AH26 showed the lowest amount of leakage and GuttaFlow the highest. There was no significant difference between the sealing ability of AH26 and RoekoSeal at all times.

We should reject the null hypothesis because after 2 weeks AH26filled root canals showed significantly better sealing ability than root canals filled with GuttaFlow. In a fluid-filtration study (11), GuttaFlow with single-cone provided inferior coronal seal than that of AH Plus. The authors recommended placement of accessory cones to reduce sealer thickness coronally (11). In another fluid filtration study (12), GuttaFlow also showed inferior sealing than AH Plus in combination with different obturation techniques. When a lentulo spiral and no gutta-percha cones were used, GuttaFlow provided a similar seal to that of AH Plus. Because we used lentulo spiral to introduce GuttaFlow into the canals, the difference between the findings can be due to use of gutta-percha cones in this study. We speculate that the matrix of this thixotropic sealer might flow under the pressure applied by the inserted gutta-percha cones, leaving only the gutta-percha particles between the cones and the dentin wall. Another possible explanation might be the higher sensitivity of the glucose penetration setup over the fluid filtration (2). At week 4, a slight decrease in glucose penetration but no change in the percentage of leaking samples was seen in the AH26 and GuttaFlow groups. The amount of gutta-percha in these groups might explain this. AH26 (lateral compaction) and GuttaFlow (gutta-percha powder) groups contained more gutta-percha than RoekoSeal group. Gutta-percha might expand after prolonged storage in water (13). ElAyouti et al (14) evaluated the presence and area of the voids within GuttaFlow fillings and between the sealer and the root canal wall at 5 apical-coronal levels. Although they observed that the mean area of the voids was the lowest in GuttaFlow group, the frequency of the voids was significantly higher than the conventional cold lateral and warm vertical compaction of gutta-percha in combination with AH Plus. This is somewhat in accord with our findings. The glucose leakage model used in the present study is able to detect a true void (a through-and-through void that communicates with both ends of the filling), but a cul-de-sac type void (porosity) might remain undetected. In the study by ElAyouti et al, the significantly high frequency of the voids at all measurement levels in the GuttaFlow group, although smaller in area, indicates an

1. Xu Q, Fan MW, Fan B, Cheung GS, Hu HL. A new quantitative method using glucose for analysis of endodontic leakage. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2005;99:107–11. 2. Shemesh H, Wu M-K, Wesselink PR. Leakage along apical root fillings with and without smear layer using two different leakage models: a two-month longitudinal ex vivo study. Int Endod J 2006;39:968 –76. 3. Wu M-K, van der Sluis LWM, Wesselink PR. A 1-year follow-up study on leakage of single-cone fillings with RoekoRSA sealer. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006;101:662–7. 4. Kont Çobankara F, Adanır N, Belli S, Pashley DH. A quantitative evaluation of apical leakage of four root-canal sealers. Int Endod J 2002;35:979 – 84. 5. Wu M-K, Tigos E, Wesselink PR. An 18-month longitudinal study on a new siliconbased sealer, RSA RoekoSeal: a leakage study in vitro. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;94:499 –502. 6. Ørstavik D, Nordahl I, Tibballs JE. Dimensional change following setting of root canal sealer materials. Dent Mater 2001;17:512–9. 7. Miletic´ I, Devcˇic´ N, Anic´ I, Borcˇic´ J, Karlovic´ Z, Osmak M. The cytotoxicity of RoekoSeal and AH Plus compared during different setting periods. J Endod 2005;31:307–9. 8. Bouillaguet S, Wataha JC, Lockwood PE, Galgano C, Golay A, Krejci I. Cytotoxicity and sealing properties of four classes of endodontic sealers evaluated by succinic dehydrogenase activity and confocal laser scanning microscopy. Eur J Oral Sci 2004;112:182–7. 9. Al-Awadhi S, Spears R, Gutmann JL, Opperman LA. Cultured primary osteoblast viability and apoptosis in the presence of root canal sealers. J Endod 2004;30:527–33. 10. Bouillaguet S, Wataha JC, Tay FR, Brackett MG, Lockwood PE. Initial in vitro biological response to contemporary endodontic sealers. J Endod 2006;32:989 –92. 11. Monticelli F, Sword J, Martin RL, et al. Sealing properties of two contemporary single-cone obturation systems. Int Endod J 2007;40:374 – 85. 12. Brackett MG, Martin R, Sword J, et al. Comparison of seal after obturation techniques using a polydimethylsiloxane-based root canal sealer. J Endod 2006;32:1188 –90. 13. Wu M-K, Fan B, Wesselink PR. Diminished leakage along root canals filled with guttapercha without sealer over time: a laboratory study. Int Endod J 2000;33:121–5. 14. ElAyouti A, Achleithner C, Löst C, Weiger R. Homogeneity and adaptation of a new gutta-percha paste to root canal walls. J Endod 2005;31:687–90.

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Sealing Ability of New Polydimethylsiloxane-based Root Canal Filling Material

References

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