doi:10.1111/iej.12257
The bond strength of endodontic sealers to root dentine exposed to different gutta-percha solvents
€ Tuncay1, H. Arslan3, B. Kesim1 & B. Yasßa4 lu1, S. Demirbuga2, O. H. S. Topcßuog 1 Department of Endodontics, Faculty of Dentistry, Erciyes University, Kayseri; 2Department of Restorative Dentistry, Faculty of Dentistry, Erciyes University, Kayseri; 3Department of Endodontics, Faculty of Dentistry, Katip C ß elebi University, Izmir; and 4 Department of Restorative Dentistry, Faculty of Dentistry, Katip C ß elebi University, Izmir, Turkey
Abstract € , Arslan H, lu HS, Demirbuga S, Tuncay O Topcßuog Kesim B, Yasßa B. The bond strength of endodontic sealers to root dentine exposed to different gutta-percha solvents. International Endodontic Journal, 47, 1100–1106, 2014.
Aim To evaluate the effects of various gutta-percha solvents on the push-out bond strength of several root canal sealers on root dentine. Methodology The root canals of 210 single-rooted human teeth were prepared with the ProTaper System (Dentsply Maillefer, Ballaigues, Switzerland) up to a master apical file size of F4, and the following variables evaluated for bond strength: solvent type (chloroform, eucalyptol and orange oil), time (2 and 5 min), sealer type (AH Plus, MTA Fillapex and Sealapex) and root thirds (coronal, middle and apical). After canal filling, three 1-mm-thick slices were obtained from each root sample, and the bond strength of the test materials was measured using a
Introduction The success of root canal treatment depends on completely cleaning and shaping, and then filling the root canal systems. If these parameters are not achieved, post-treatment disease may occur because of the persistence of bacteria in the root canal system (Siqueira 2001). When this occurs, nonsurgical root canal retreatment is often indicated as the first choice to
Correspondence: H€ useyin S. Topcßuo glu, Department of Endodontics, Faculty of Dentistry, Erciyes University, Melikgazi, Kayseri Zip code: 38039, Turkey (Tel.: +90 (352) 207 66 66; Fax: +90 (352) 438 06 57; e-mail: topcuogluhs@ hotmail.com).
1100
International Endodontic Journal, 47, 1100–1106, 2014
push-out test set-up at a cross-head speed of 1 mm min1. The data were analysed using four-way factorial ANOVA (P = 0.05). Results Bond strength was significantly affected by solvent type and time (P < 0.001). The use of chloroform for 5 min in the root canal decreased bond strength of all sealers (P < 0.001). Eucalyptol and orange oil did not affect the bond strength of the sealers (P > 0.05). In all conditions, the push-out bond strength was highest for AH Plus and lowest for MTA Fillapex (P < 0.001). Bond strength values decreased in a corono-apical direction in all groups (P < 0.001). Conclusions Chloroform used for 5 min during retreatment decreased the bond strength of AH Plus, Sealapex and MTA Fillapex to root dentine. Keywords: bond strength, root dentine, sealer, solvent. Received 12 August 2013; accepted 27 January 2014
eliminate the microbial infection. The retreatment aims to completely remove the old filling material from the root canal system to allow effective cleaning, shaping and refilling of the root canal (Kvist & Reit 1999, Mollo et al. 2012). In root canal retreatment, solvents are often used as an aid for removing gutta-percha. Chloroform, an organic solvent, has been shown to be effective when used with gutta-percha (Wilcox 1995, Sch€ afer & Zandbiglari 2002); however, it has carcinogenic potential (Vajrabhaya et al. 2004), and the search for alternative solvents continues (Hunter et al. 1991). Studies have shown that essential oils, such as eucalyptol, orange oil and turpentine oil, may be used in retreatment because they are safe and useful for dissolution
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
lu et al. Bond strength of endodontic sealers Topcß uog
of gutta-percha and root canal sealers (Uemura et al. 1997, Hansen 1998). Several chemical agents change the chemical structure of dentine and the Ca/P ratio of dentine surfaces. Alterations in the original Ca/P ratio between organic and inorganic components may change the permeability and solubility of root dentine and can affect the adhesion of dental materials to hard tissues (Hennequin et al. 1994, Rotstein et al. 1996). During root canal retreatment, the root and coronal dentine is exposed to gutta-percha solvents deposited in root canals. Kaufman et al. (1997) reported that solvents may alter the chemical composition of dentine surface and affect bond strength of restorative materials to dentine. Many studies have been conducted to evaluate the effects of various endodontic procedures on the bond strength of root canal sealers (Haragushiku et al. 2010, Amin et al. 2012, Vilanova et al. 2012). However, there is no information about the effects of various gutta-percha solvents used over different application times on the bond strength of sealers to root dentine. The purpose of this study was to compare the push-out bond strength of different endodontic sealers to root dentine exposed to various gutta-percha solvents for 2 or 5 min. The null hypothesis is that various gutta-percha solvents do not affect the bond strength of several root canal sealers.
Materials and methods Two hundred and ten freshly extracted, straight, single-rooted human mandibular premolar teeth were selected and stored in distilled water until required. Preoperative mesiodistal and buccolingual radiographs were taken to verify the presence of a single canal. Criteria for tooth selection included a completely formed apex and absence of previous root filling, resorption or calcifications. To ensure standardization, crowns of the selected teeth were partially removed to achieve a final length of 21 mm for each tooth. The crowns served as a reservoir for the solvent. Endodontic access cavities were prepared using diamond burs (Diatech; Coltene Whaledent, Altstatten, Switzerland) with a high-speed handpiece under water cooling. A size 10 K-file (Dentsply Maillefer) was then placed in the canal until it was visible at the apical foramen. The working length was determined by subtracting 1 mm from this measurement. The 210 roots were instrumented with the ProTaper rotary system (Dentsply Maillefer) up to size F4
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
(size 40, 0.06 taper) as the master apical file. During preparation, the root canal was irrigated with 5 mL of 2.5% sodium hypochlorite (NaOCl) solution using a syringe and a 30-gauge needle (NaviTip; Ultradent, South Jordan, UT, USA) between each instrument change. A total of 210 roots were then randomly assigned to six experimental groups (n = 30) according to the solvent type and time of exposure and one control group (n = 30) as follows: group 1: not exposed to any solvent (Control) group 2: chloroform for 2 min group 3: chloroform for 5 min group 4: eucalyptol for 2 min group 5: eucalyptol for 5 min group 6: orange oil for 2 min group 7: orange oil for 5 min. A total of 0.2 mL of each solvent was placed in the root canal and left in place up to completion of the exposure time and then removed with paper points (Dentsply Maillefer). All canals received a final rinse of 5 mL 17% EDTA for 1 min followed by 5 mL distilled water and dried with absorbent paper points. The roots within each of the six experimental groups and the control group were further randomly assigned to three subgroups (n = 10) according to the sealer used as follows: AH Plus (Dentsply DeTrey GmbH, Konstanz, Germany), MTA Fillapex (Angelus, Londrina, PR, Brazil) and Sealapex (Kerr, Romulus, MI, USA). Each sealer was mixed according to manufacturer’s instructions for use. All canals were filled using the single-cone technique with F4 gutta-percha cones (Dentsply Maillefer). Following canal filling, mesiodistal and buccolingual radiographs were taken to confirm complete filling. The coronal 1 mm of filling material was then removed, and the spaces were filled with a temporary filling material (Cavit; 3M ESPE, Seefeld, Germany). After being wrapped in pieces of sponge, all the specimens were stored at 37 °C in 100% humidity for 2 weeks.
Push-out testing The specimens were sectioned horizontally into three 1 0.1 mm thickness serial slices using a low-speed precision diamond saw (Isomet; Buehler, Lake Bluff, IL, USA) under continuous water irrigation. The thickness of each slice was measured with a digital calliper (Teknikel, Istanbul, Turkey) with an accuracy of 0.001 mm. Both apical and coronal aspects of the
International Endodontic Journal, 47, 1100–1106, 2014
1101
1102
International Endodontic Journal, 47, 1100–1106, 2014
0.30 0.50 0.62 0.33 0.57 0.47 0.37 0.36 0.31 0.37 0.46 0.23 0.19 0.38 0.46 0.32 0.40 0.28 0.40 0.47 0.70
0.08
1.22 1.60 2.26 2.49 3.10 3.21 1.50 1.44 2.44 2.39 2.83 3.13 0.94 1.58 1.40 2.31 1.65 3.23 1.42 2.67 3.30
0.88
0.77 0.33 0.40 0.47 0.38 0.22 0.33 0.34 0.27 0.08 0.28 0.41 Fillapex
Sealapex
0.15 0.21 0.28 0.39 0.33 0.20
0.38
0.46
0.31
1.04
0.52 0.39
1.31 1.71
0.69 0.51
2.71 2.39
0.32 0.46
0.71 0.89 1.52 1.37
0.58 0.41 0.58
2.11
0.52 0.57
2.38 0.64
0.53 0.40
1.03 0.81
0.61 0.51
1.45 1.24
0.47 0.37
2.27 1.01
0.35 0.47
1.19
0.84
2.37 MTA
4.14
5 min 2 min
4.44 5.21
5 min 2 min
5.85 6.42
5 min 2 min
6.21 4.34
5 min 2 min
4.28 5.35
5 min 2 min
5.87 6.34
5 min 2 min
7.44 3.01
5 min 2 min
4.43 3.43
5 min 2 min
5.38 4.72
5 min 2 min
6.30
Middle Apical
Coronal
Middle
Apical
Coronal
Orange Oil Eucalyptol
Apical
4.24 5.57
Middle
7.20
Coronal
The mean and standard deviations of the groups are summarized in Table 1. All variables had a significant effect on the push-out bond strength of sealers (P < 0.001) (Table 2). There was a significant effect
AH Plus
Results
Middle
After measurement of bond strength, both sides of the failed bond were examined under a stereomicroscope (BX60; Olympus, Tokyo, Japan) at 309 magnification to determine the mode of fracture. The fracture mode was classified according to the following criteria: adhesive fracture at the sealer–dentine or sealer–core material interface, cohesive fracture within sealer and mixed fracture in both the sealer and dentine (Skidmore et al. 2006). Two specimens that were representative of the fracture modes from each group were further evaluated under a scanning electron microscope (SEM) (Leo-440; LEO Electron Microscopy Ltd., Cambridge, UK). Statistical analysis was carried out using four-way factorial ANOVA (P = 0.05) at the 95% confidence level. All statistical analyses were performed using SPSS 16.0 software (SPSS Inc., Chicago, IL, USA).
Coronal
Analysis of failure modes
Chloroform
where N = maximum load (N), A = adhesion area of root canal filling (mm2). The adhesion surface area of each section was calculated as: (p r1 + p r2) 9L, where L = √ (r1 – r2)2 + h2; p = 3.14, r1 and r2 = smaller and larger radii, respectively, and h = thickness of the slice in mm.
Control
Push-out bond strength (MPa) ¼ N/A
Table 1 Mean standard deviations of push-out bond strength values (MPa) for each sealer, solvent, third and time period
specimens were then examined microscopically to confirm a circular canal shape. The push-out test was performed in a universal testing machine (Instron 4444; Instron Corp., Canton, MA, USA) by applying a continuous load to the apical side of each slice using 0.7-, 0.8- and 0.9-mm-diameter cylindrical plungers, matching the canal diameter of each third. The diameter of each plunger was approximately 90% of the canal diameter. Loading was applied at a cross-head speed of 1 mm min1 from the apical to the coronal direction until bond fracture occurred. The maximum load applied to filling material before fracture was recorded in newtons and converted to megapascals (MPa) according to the following formula (Nagas et al. 2007):
Apical
lu et al. Bond strength of endodontic sealers Topcß uog
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
lu et al. Bond strength of endodontic sealers Topcß uog
Table 2 Summary of the statistical analysis showing the main effects of solvent, time, sealer and canal third on bond strength Variable
F-value
P-value
Solvent Time Sealer Third
104.719 186.188 4071.08 762.15
The bond strength of endodontic sealers to root dentine exposed to different gutta-percha solvents
€ Tuncay1, H. Arslan3, B. Kesim1 & B. Yasßa4 lu1, S. Demirbuga2, O. H. S. Topcßuog 1 Department of Endodontics, Faculty of Dentistry, Erciyes University, Kayseri; 2Department of Restorative Dentistry, Faculty of Dentistry, Erciyes University, Kayseri; 3Department of Endodontics, Faculty of Dentistry, Katip C ß elebi University, Izmir; and 4 Department of Restorative Dentistry, Faculty of Dentistry, Katip C ß elebi University, Izmir, Turkey
Abstract € , Arslan H, lu HS, Demirbuga S, Tuncay O Topcßuog Kesim B, Yasßa B. The bond strength of endodontic sealers to root dentine exposed to different gutta-percha solvents. International Endodontic Journal, 47, 1100–1106, 2014.
Aim To evaluate the effects of various gutta-percha solvents on the push-out bond strength of several root canal sealers on root dentine. Methodology The root canals of 210 single-rooted human teeth were prepared with the ProTaper System (Dentsply Maillefer, Ballaigues, Switzerland) up to a master apical file size of F4, and the following variables evaluated for bond strength: solvent type (chloroform, eucalyptol and orange oil), time (2 and 5 min), sealer type (AH Plus, MTA Fillapex and Sealapex) and root thirds (coronal, middle and apical). After canal filling, three 1-mm-thick slices were obtained from each root sample, and the bond strength of the test materials was measured using a
Introduction The success of root canal treatment depends on completely cleaning and shaping, and then filling the root canal systems. If these parameters are not achieved, post-treatment disease may occur because of the persistence of bacteria in the root canal system (Siqueira 2001). When this occurs, nonsurgical root canal retreatment is often indicated as the first choice to
Correspondence: H€ useyin S. Topcßuo glu, Department of Endodontics, Faculty of Dentistry, Erciyes University, Melikgazi, Kayseri Zip code: 38039, Turkey (Tel.: +90 (352) 207 66 66; Fax: +90 (352) 438 06 57; e-mail: topcuogluhs@ hotmail.com).
1100
International Endodontic Journal, 47, 1100–1106, 2014
push-out test set-up at a cross-head speed of 1 mm min1. The data were analysed using four-way factorial ANOVA (P = 0.05). Results Bond strength was significantly affected by solvent type and time (P < 0.001). The use of chloroform for 5 min in the root canal decreased bond strength of all sealers (P < 0.001). Eucalyptol and orange oil did not affect the bond strength of the sealers (P > 0.05). In all conditions, the push-out bond strength was highest for AH Plus and lowest for MTA Fillapex (P < 0.001). Bond strength values decreased in a corono-apical direction in all groups (P < 0.001). Conclusions Chloroform used for 5 min during retreatment decreased the bond strength of AH Plus, Sealapex and MTA Fillapex to root dentine. Keywords: bond strength, root dentine, sealer, solvent. Received 12 August 2013; accepted 27 January 2014
eliminate the microbial infection. The retreatment aims to completely remove the old filling material from the root canal system to allow effective cleaning, shaping and refilling of the root canal (Kvist & Reit 1999, Mollo et al. 2012). In root canal retreatment, solvents are often used as an aid for removing gutta-percha. Chloroform, an organic solvent, has been shown to be effective when used with gutta-percha (Wilcox 1995, Sch€ afer & Zandbiglari 2002); however, it has carcinogenic potential (Vajrabhaya et al. 2004), and the search for alternative solvents continues (Hunter et al. 1991). Studies have shown that essential oils, such as eucalyptol, orange oil and turpentine oil, may be used in retreatment because they are safe and useful for dissolution
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
lu et al. Bond strength of endodontic sealers Topcß uog
of gutta-percha and root canal sealers (Uemura et al. 1997, Hansen 1998). Several chemical agents change the chemical structure of dentine and the Ca/P ratio of dentine surfaces. Alterations in the original Ca/P ratio between organic and inorganic components may change the permeability and solubility of root dentine and can affect the adhesion of dental materials to hard tissues (Hennequin et al. 1994, Rotstein et al. 1996). During root canal retreatment, the root and coronal dentine is exposed to gutta-percha solvents deposited in root canals. Kaufman et al. (1997) reported that solvents may alter the chemical composition of dentine surface and affect bond strength of restorative materials to dentine. Many studies have been conducted to evaluate the effects of various endodontic procedures on the bond strength of root canal sealers (Haragushiku et al. 2010, Amin et al. 2012, Vilanova et al. 2012). However, there is no information about the effects of various gutta-percha solvents used over different application times on the bond strength of sealers to root dentine. The purpose of this study was to compare the push-out bond strength of different endodontic sealers to root dentine exposed to various gutta-percha solvents for 2 or 5 min. The null hypothesis is that various gutta-percha solvents do not affect the bond strength of several root canal sealers.
Materials and methods Two hundred and ten freshly extracted, straight, single-rooted human mandibular premolar teeth were selected and stored in distilled water until required. Preoperative mesiodistal and buccolingual radiographs were taken to verify the presence of a single canal. Criteria for tooth selection included a completely formed apex and absence of previous root filling, resorption or calcifications. To ensure standardization, crowns of the selected teeth were partially removed to achieve a final length of 21 mm for each tooth. The crowns served as a reservoir for the solvent. Endodontic access cavities were prepared using diamond burs (Diatech; Coltene Whaledent, Altstatten, Switzerland) with a high-speed handpiece under water cooling. A size 10 K-file (Dentsply Maillefer) was then placed in the canal until it was visible at the apical foramen. The working length was determined by subtracting 1 mm from this measurement. The 210 roots were instrumented with the ProTaper rotary system (Dentsply Maillefer) up to size F4
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
(size 40, 0.06 taper) as the master apical file. During preparation, the root canal was irrigated with 5 mL of 2.5% sodium hypochlorite (NaOCl) solution using a syringe and a 30-gauge needle (NaviTip; Ultradent, South Jordan, UT, USA) between each instrument change. A total of 210 roots were then randomly assigned to six experimental groups (n = 30) according to the solvent type and time of exposure and one control group (n = 30) as follows: group 1: not exposed to any solvent (Control) group 2: chloroform for 2 min group 3: chloroform for 5 min group 4: eucalyptol for 2 min group 5: eucalyptol for 5 min group 6: orange oil for 2 min group 7: orange oil for 5 min. A total of 0.2 mL of each solvent was placed in the root canal and left in place up to completion of the exposure time and then removed with paper points (Dentsply Maillefer). All canals received a final rinse of 5 mL 17% EDTA for 1 min followed by 5 mL distilled water and dried with absorbent paper points. The roots within each of the six experimental groups and the control group were further randomly assigned to three subgroups (n = 10) according to the sealer used as follows: AH Plus (Dentsply DeTrey GmbH, Konstanz, Germany), MTA Fillapex (Angelus, Londrina, PR, Brazil) and Sealapex (Kerr, Romulus, MI, USA). Each sealer was mixed according to manufacturer’s instructions for use. All canals were filled using the single-cone technique with F4 gutta-percha cones (Dentsply Maillefer). Following canal filling, mesiodistal and buccolingual radiographs were taken to confirm complete filling. The coronal 1 mm of filling material was then removed, and the spaces were filled with a temporary filling material (Cavit; 3M ESPE, Seefeld, Germany). After being wrapped in pieces of sponge, all the specimens were stored at 37 °C in 100% humidity for 2 weeks.
Push-out testing The specimens were sectioned horizontally into three 1 0.1 mm thickness serial slices using a low-speed precision diamond saw (Isomet; Buehler, Lake Bluff, IL, USA) under continuous water irrigation. The thickness of each slice was measured with a digital calliper (Teknikel, Istanbul, Turkey) with an accuracy of 0.001 mm. Both apical and coronal aspects of the
International Endodontic Journal, 47, 1100–1106, 2014
1101
1102
International Endodontic Journal, 47, 1100–1106, 2014
0.30 0.50 0.62 0.33 0.57 0.47 0.37 0.36 0.31 0.37 0.46 0.23 0.19 0.38 0.46 0.32 0.40 0.28 0.40 0.47 0.70
0.08
1.22 1.60 2.26 2.49 3.10 3.21 1.50 1.44 2.44 2.39 2.83 3.13 0.94 1.58 1.40 2.31 1.65 3.23 1.42 2.67 3.30
0.88
0.77 0.33 0.40 0.47 0.38 0.22 0.33 0.34 0.27 0.08 0.28 0.41 Fillapex
Sealapex
0.15 0.21 0.28 0.39 0.33 0.20
0.38
0.46
0.31
1.04
0.52 0.39
1.31 1.71
0.69 0.51
2.71 2.39
0.32 0.46
0.71 0.89 1.52 1.37
0.58 0.41 0.58
2.11
0.52 0.57
2.38 0.64
0.53 0.40
1.03 0.81
0.61 0.51
1.45 1.24
0.47 0.37
2.27 1.01
0.35 0.47
1.19
0.84
2.37 MTA
4.14
5 min 2 min
4.44 5.21
5 min 2 min
5.85 6.42
5 min 2 min
6.21 4.34
5 min 2 min
4.28 5.35
5 min 2 min
5.87 6.34
5 min 2 min
7.44 3.01
5 min 2 min
4.43 3.43
5 min 2 min
5.38 4.72
5 min 2 min
6.30
Middle Apical
Coronal
Middle
Apical
Coronal
Orange Oil Eucalyptol
Apical
4.24 5.57
Middle
7.20
Coronal
The mean and standard deviations of the groups are summarized in Table 1. All variables had a significant effect on the push-out bond strength of sealers (P < 0.001) (Table 2). There was a significant effect
AH Plus
Results
Middle
After measurement of bond strength, both sides of the failed bond were examined under a stereomicroscope (BX60; Olympus, Tokyo, Japan) at 309 magnification to determine the mode of fracture. The fracture mode was classified according to the following criteria: adhesive fracture at the sealer–dentine or sealer–core material interface, cohesive fracture within sealer and mixed fracture in both the sealer and dentine (Skidmore et al. 2006). Two specimens that were representative of the fracture modes from each group were further evaluated under a scanning electron microscope (SEM) (Leo-440; LEO Electron Microscopy Ltd., Cambridge, UK). Statistical analysis was carried out using four-way factorial ANOVA (P = 0.05) at the 95% confidence level. All statistical analyses were performed using SPSS 16.0 software (SPSS Inc., Chicago, IL, USA).
Coronal
Analysis of failure modes
Chloroform
where N = maximum load (N), A = adhesion area of root canal filling (mm2). The adhesion surface area of each section was calculated as: (p r1 + p r2) 9L, where L = √ (r1 – r2)2 + h2; p = 3.14, r1 and r2 = smaller and larger radii, respectively, and h = thickness of the slice in mm.
Control
Push-out bond strength (MPa) ¼ N/A
Table 1 Mean standard deviations of push-out bond strength values (MPa) for each sealer, solvent, third and time period
specimens were then examined microscopically to confirm a circular canal shape. The push-out test was performed in a universal testing machine (Instron 4444; Instron Corp., Canton, MA, USA) by applying a continuous load to the apical side of each slice using 0.7-, 0.8- and 0.9-mm-diameter cylindrical plungers, matching the canal diameter of each third. The diameter of each plunger was approximately 90% of the canal diameter. Loading was applied at a cross-head speed of 1 mm min1 from the apical to the coronal direction until bond fracture occurred. The maximum load applied to filling material before fracture was recorded in newtons and converted to megapascals (MPa) according to the following formula (Nagas et al. 2007):
Apical
lu et al. Bond strength of endodontic sealers Topcß uog
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
lu et al. Bond strength of endodontic sealers Topcß uog
Table 2 Summary of the statistical analysis showing the main effects of solvent, time, sealer and canal third on bond strength Variable
F-value
P-value
Solvent Time Sealer Third
104.719 186.188 4071.08 762.15
