Tanta Dental Journal

: 2017  |  Volume : 14  |  Issue : 4  |  Page : 181--186

Effect of different root canal disinfection protocols on push-out bond strength of two endodontic sealers

Neveen A Shaheen, Walaa M Ghoneim 
 Department of Endodontics, Faculty of Dentistry, Tanta University, Tanta, Egypt

Correspondence Address:
Walaa M Ghoneim
Department of Endodontics, Faculty of Dentistry, Tanta University, Tanta


Introduction The purpose of this study was to evaluate push-out bond strength of two endodontic sealers (MetaSeal, Endosequence BC) to radicular dentin following different disinfection protocols [sodium hypochlorite (NaOCl), photoactivated disinfection, and ozonated olive oil]. Materials and methods A total of 60 freshly extracted human single rooted premolars with single root canals were selected. The crowns were removed to obtain a standardized root length of 15 mm and working length was determined. Root canals were prepared using ProTaper Universal rotary instruments up to F4 and irrigation throughout instrumentation was performed using 3 ml of 0.9% sodium chloride. Roots were randomly divided into six groups (n=10). In groups 1 and 2, root canals were finally irrigated with 3 ml of 2.5% NaOCl (as control groups), in groups 3 and 4, final disinfection protocol was performed with photoactivated disinfection, but in groups 5 and 6, root canals were finally disinfected by coating ProTaper F4 file with ozonated olive oil. In groups 1, 3, and 5, root canals were obturated with gutta-percha/MetaSeal sealer while in groups 2, 4, and 6, obturation was performed using gutta-percha/Endosequence BC sealer. Three horizontal sections were prepared in a thickness of 2 mm each corresponding to apical, middle, and coronal parts of the root. Each section was subjected to a compressive load to evaluate push-out bond strength and the data were statistically analyzed using two-way analysis of variance and post-hoc Tukey test. Results PAD groups recorded the highest values while ozonated olive oil groups recorded the lowest values. Bond strength of Endosequence BC was significantly higher than MetaSeal (P ≤ 0.05). The bond strength in the coronal sections was higher than that in the middle and apical sections. Conclusion PDA final disinfection protocol performed similarly to NaOCl and does not negatively affect bond strength as ozonated olive oil. Endosequence BC was better than MetaSeal in terms of bond strength.

How to cite this article:
Shaheen NA, Ghoneim WM. Effect of different root canal disinfection protocols on push-out bond strength of two endodontic sealers.Tanta Dent J 2017;14:181-186

How to cite this URL:
Shaheen NA, Ghoneim WM. Effect of different root canal disinfection protocols on push-out bond strength of two endodontic sealers. Tanta Dent J [serial online] 2017 [cited 2018 Feb 24 ];14:181-186
Available from: http://www.tmj.eg.net/text.asp?2017/14/4/181/221381

Full Text


Insufficient removal of the microorganisms infecting the root canal system is considered a main reason accounting for unsuccessful treatment. Preparation of the root canal using either conventional hand or nickel–titanium rotary files do not permit full removal of the contaminated innermost layer of dentin because the effect of mechanical debridement is limited by the intricate internal anatomy, lateral canals, and apical ramifications [1],[2].

Therefore, chemical disinfection is needed to support the instrumental debridement where root canal irrigation with disinfectant agents such as sodium hypochlorite (NaOCl) or chlorhexidine is considered as an integral part of preparation [3],[4]. NaOCl has been widely used as an irrigation solution for the chemomechanical treatment of root canals because of its solvent activity on both necrotic and vital tissues. Moreover, it demonstrates stronger antimicrobial efficacy in root canals compared to other irrigation solutions [5]. However, NaOCl is highly irritating when in contact with periapical tissues [6], reduces the resistance of teeth to fracture [7], interferes negatively with the bond strength of adhesive restorations to dentin [8],[9], and does not eradicate the entire microbial flora in infected root canals [10],[11],[12].

Novel antimicrobial approaches to disinfect root canals have been proposed that include photodynamic therapy [13],[14] which also known as photoradiation therapy, phototherapy, photochemotherapy, or photoactivated chemotherapy. It is considered a medical treatment that utilizes activation of a photosensitizing agent (photosensitizer) by exposure to light of a specific wave length in the presence of oxygen (O2) [15]. There is an energy transfer from the activated photosensitizer to the available O2 that results in formation of toxic O2 species, such as singlet O2 and free radicals. Singlet O2 and radical species cause a rapid and selective destruction of microorganisms. Most photosensitizers are activated by light between 630 and 700 nm. The most commonly used photosensitizers are hematoporphyrin derivatives (620–650 nm), phenothiazine as toluidine blue (TB) and methylene blue (620–700 nm), cyanine (600–805 nm), phytotherapic agents (550–700 nm), and hytalocyanines (660–700 nm) [16],[17],[18].

One possible agent of interest for dealing with persistent organisms is ozone [19] which is a triatomic molecule, thermodynamically highly unstable gas [20] that readily dissociates back into O2, liberating a reactive form of oxygen (O1) [21]. Since ozone is a powerful oxidizer, it effectively kills bacteria, fungi, viruses, and parasites at a dramatically lower concentration and faster time than chlorine, with no toxic side effects. Another interesting fact is that anaerobic-type microbes produce a positive-charged infection environment which attracts ozone to the area since O2 is the only gas that can carry an electrical charge [22].

In dentistry, ozone has been used either in gaseous form or in aqueous form (ozonated water or ozonated olive oil). Ozonated water and olive oil have the capacity to entrap and then release O2 that makes them ideal ozone delivery system 1, 3 [20]. Ozone dissolved in oil can be used as an intracanal medicament [23] or as a file coating for lubrication and disinfection [22]. Few studies in endodontic literature were evaluated the antibacterial activity of ozonated oil [24] and success rate of periradicular lesions after its use as intracanal medication [23].

Bioceramic sealers as EndoSequence BC Sealer have several advantages such as improved biocompatibility, sealing ability, high alkalinity (pH = 12.9) which enhances its bactericidal properties [25], ease of application and an increase in strength of root following obturation. Bioceramics are hydrophilic in nature and have the ability to form hydroxyapatite which form a chemical bond between the filling material and dentin walls [26]. It has a particle size of 2 μm aiding in its delivery by the means of a capillary tip [27].

Hybrid Root SEAL (MetaSEAL), is a polymethyl methacrylate-based sealer that contains an acidic resin monomer, 4-methacryloxyethyl trimelliate anhydride (4-META), has been recently introduced. This sealer is a dual-cured, self-etching, and self-adhesive sealer that does not require any additional priming or acid-etching to the root canal dentine [28].

Adhesion of sealers to root canal dentin by close contact is important to resist micromechanical forces during root canal treatment [29]. Numerous investigators have evaluated the adhesion of resin-based sealer to root dentin after NaOCl irrigation. However, there are limited data about the effect of photoactivated disinfection (PAD) on the adhesion of resin-based sealer to root dentin and up to date no data about the effect of PAD, ozonated olive oil on the adhesion of MetaSEAL resin-based and bioceramic sealers to root dentin. Therefore, the aim of this study was to evaluate the effects of PAD, ozonated olive oil on the bond strength of a resin-based sealer (MetaSEAL) and a Bioceramic sealer (Endosequence BC) to root canal dentin in comparison to NaOCl.

 Materials and Methods

Sample selection and preparation

A total of 60 freshly extracted human single rooted premolars with single root canals were selected. All patients were informed about the purpose and steps of this research and written consents were signed for using their extracted teeth in the research according to the Research Ethics Committee of Tanta Faculty of Dentistry, Tanta University. Teeth were cleaned by removing the hard deposits using curettes and the soft tissues were dissolved by soaking them in 5.25% NaOCl (Clorox Co., 10th of Ramadan, Egypt) for 10 min and then stored in daily-changed normal saline solution until use.

The crowns were removed using a water-cooled diamond disc (Komet; Brasseler, Lemgo, Germany) to obtain a standardized root length of 15 mm. Working length was determined by inserting #10 stainless steel hand K-file (Mani Inc., Tochigi, Japan) until its tip was just visible through the apical foramen and then 1 mm was subtracted from that length. The root canals were prepared using ProTaper Universal rotary instruments (Dentsply Maillefer, Ballaigues, Switzerland) up to an apical preparation size corresponding to F4 (#40, 0.06). Irrigation throughout instrumentation was performed using 3 ml of 0.9% sodium chloride (Alfath Co., Borg Alarab, Egypt) and then the root canals were dried with size 40 paper points (Dentsply Maillefer).

Roots were randomly divided into six groups (n = 10 each) according to the final disinfection protocol and the sealer used in root canal obturation as follows:

Group 1: root canals were finally irrigated with 3 ml of 2.5% NaOCl for 60 s and then obturated with gutta-percha/MetaSeal powder and liquid sealer (Parkell Inc., Edgewood, New York, USA) using single cone technique.Group 2: root canals were finally irrigated as in group 1 and then obturated with gutta-percha/Endosequence BC injectable sealer (Brasseler, Savannah, Georgia, USA) using single cone technique.Group 3: final disinfection protocol was performed with PAD (Lit-600; Apoza Enterprise Co. Ltd, New Taipei City, Taiwan) in which a watery solution of TB was prepared to 50 μg/ml concentration and stored in the dark at 4°C until used as photosensitizer. A volume of 75 μl of PAD solution (TB) was injected into the root canal using disposable syringe with gauge 29 NaviTip (Ultradent, South Jordan, Utah). The liquid was then agitated for 60 s using #40 K-file, and then the disposable tip of LED light source of PAD was inserted 3 mm short of the apex and light activated for 60 s at light wave length of 635 nm according to the manufacturer instructions. Root canals were obturated with gutta-percha/MetaSeal using single cone technique.Group 4: final disinfection protocol was performed as in group 3 and then obturated with gutta-percha/Endosequence BC using single cone technique.Group 5: root canals were finally disinfected by coating ProTaper F4 file with ozonated olive oil (Snow White, Cairo, Egypt) and inserting it in up and down motion for 60 s and then obturated with gutta-percha/MetaSeal using single cone technique.Group 6: root canals were finally disinfected as in group 5 and then obturated with gutta-percha/Endosequence BC using single cone technique.

Following the final disinfectin protocol, all root canals were rinsed with normal saline solution followed by 2 ml of 17% EDTA (Essential Dental Systems Inc., South Hackensack, New Jersey, USA) for 1 min to remove the smear layer followed by distilled water and then dried with size 40 paper points before obturation.

After root canal obturation, radiographs were taken at different angulations to verify the quality of root canal filling. The orifices of root canals were sealed with Cavit temporary filling (3M ESPE, Seefeld, Germany) and stored in 100% humidity at 37°C for 7 days to allow complete setting of the sealers.

Evaluation of push-out bond strength test

After fixation in acrylic blocks, each specimen was horizontally sectioned perpendicular to the long axis of the root using a slow-speed, water-cooled diamond disc (Komet) to produce three sections of ~2 ± 0.1 mm thickness for each root third (i.e. apical, middle, and coronal) as measured using a digital caliper (Pachymeter; Electronic Digital Instruments, Qingdao, Shandong Province, China). The coronal aspect of each disc was coded and marked, both apical and coronal aspects of each section were examined under stereomicroscope ×20 (SZ-PT; Olympus, Tokyo, Japan) before testing to confirm that the sealer filled the entire canal space without voids.

Loading was performed by means of a stainless steel plunger attached to the upper member of universal testing machine (Model 3345; Instron Industrial Products, Norwood, Massachusetts, USA) at a cross-head speed of 1 mm/min until failure occurred. Load was applied by three plungers of (1, 0.50, and 0.30 mm diameter) corresponding to the radicular third (coronal, middle, and apical) to be tested, respectively. The plunger tip was sized and positioned to touch only the filling, without stressing the surrounding dentin, in apical coronal direction to push the filling toward the larger diameter. Failure could be manifested by extrusion of filling material and confirmed by sudden drop along load-deflection curve recorded by Bluehill lite computer software.

Debonding values (maximum load) were used to calculate push-out bond strength for each root section in megapascals according to the following formula [30]:

Posh-out bond strength (MPa)=F/A.

F = maximum load (N).

A (adhesion surface area in mm 2)=π h (r1 + r2); where, π is the constant 3.14, r1: apical radius, r2: coronal one and h is the thickness of the slice in millimeters.

Statistical analysis

Data were analyzed using statistical package for the social sciences (SPSS) version 20 software for windows (SPSS Inc., Chicago, Illinois, USA). Two-way analysis of variance was performed to assess the effect of final disinfection protocol, endodontic sealer, and their interactions on push-out bond strength, then multiple comparisons were made using Tukey's post-hoc test. Statistical analysis was set at P value of less than or equal to 0.05.


The mean values of push-out bond strengths recorded for groups at different radicular thirds were presented in [Table 1]. When comparing push-out bond strength values of all groups, the highest mean values were recorded in groups 2, 4 while the lowest value was recorded with group 5 with statistical significant differences among groups at coronal and apical root levels (P < 0.0001 and 0.0042, respectively). Multiple pairwise comparisons revealed statistically significant differences between group 5 versus all groups and between group 6 versus group 2 and 4 apically. Similar findings were recorded at coronal level except no significant difference between group 5 and 6 as shown in [Table 1].{Table 1}

Results of two-way analysis of variance test revealed that a significant difference existed between the disinfection groups regardless the sealer used (P < 0.0001). PDA groups (group 3 + group 4) recorded the highest value (5.89 ± 1.79) followed by NaOCl groups (5.88 ± 1.83), while ozonated olive oil groups (group 5 + group 6) recorded the lowest value (4.44 ± 1.63). Multiple pairwise comparisons revealed a statistical significant difference between NaOCl groups (group 1 + group 2) and ozonated olive oil groups, and between PDA groups and ozonated olive oil groups while no statistical significant difference between NaOCl groups and PDA groups.

When comparing between the used sealers regardless disinfection protocol, Endosequence BC groups (group 2 + group 4 + group 6) had higher value (5.83 ± 1.85) than MetaSeal groups (group 1 + group 3 + group 5) (4.98 ± 1.80) with a statistical significant difference (P < 0.0001).

Comparisons in terms of the radicular sections in each group and regardless the sealer and disinfection protocol revealed that the bond strength in the coronal sections were higher than in the middle and apical sections with a statistical significant difference among three root canal levels (P ≤ 0.05).


Disinfection of the root canals with antimicrobial agents is one of the important stages of root canal treatment. NaOCl is the most commonly used irrigant solution so it was used in control groups while PAD has been used to enhance the disinfection effect within the dentinal tubules [31]. In addition, Ozone oils can be used to disinfect the root canal systems by its virtue bactericidal and effervescent properties [32]. The use of different disinfection agents may change the chemical and structural composition of the root canal dentin as well as its permeability, which in turn may affect the adhesion of root canal sealers to radicular dentin [29],[33].

Many sealers were proposed in Endodontics to achieve good sealing and adhesion to radicular dentin which maintain the integrity of the sealer-dentin interface during mechanical stresses [34]. Recently introduced calcium silicate-based 'Endosequence BC' is claimed to perform successfully as a root canal sealer. However, there are limited studies regarding the bond strength of Endosequence BC after different disinfection protocols. Therefore, the aim of this study was to evaluate push-out bond strength of Endosequence BC and MetaSeal to radicular dentin following different disinfection protocols.

In this study, TB was prepared to 50 μg/ml concentration as recommended by Schlafer et al. [35]who used concentrations varying between 10 μg/ml and 100 μg/ml. Push-out test was used as it is reliable and effective method for evaluating bond strength, in which fracture occurs parallel to dentine-bonding interface and allows regional assessment of bond strength among root levels [36].

The current results showed that root canal disinfection using PAD recorded the best results followed by NaOCl with no significant differences between them. These results were supported by Ok et al. [37]who concluded that PAD did not adversely affect bond strength of resin-based sealer to radicular dentin. However, it may increase bond strength of adhesive sealer if laser activation was used as reported by Alfredo et al.[38], Pecora et al., [39]. Although NaOCl may negatively affect adhesion, the high bond strength values obtained in study may be related to 17% EDTA final rinse which improve bonding as reported by Ibrahim et al.[40].

The impaired bond strength values of ozonated olive oil groups (group 5 + group 6) may be due to presence of oil remnants that may interfere with adhesion of sealers to dentin. This was supported by Nainan et al. [41] and Vineeta et al. [42] studies who mentioned that oil vehicle is difficult to be removed even with 17% EDTA.

On the other hand, Endosequence BC sealer had better bond strength values than MetaSeal sealer. This may be explained by tag-like structures that formed at the interface between Endosequence BC sealer and dentine which in turn may directly influence the mechanical properties of this interface [43]. In addition, the resulting chemical interaction between calcium silicate sealers and dentine immediately after setting which has been described as a 'mineral infiltration zone' that results from an alkaline caustic etching derived from calcium hydroxide formed at the interface may play an important role in increasing its bond strength [44]. Additionally, its bioactivity, outstanding viscosity, and extremely small nanoparticle size may help the sealer to be adaptable to the surface of gutta-percha and flow readily into the dentinal tubules, lateral canals and irregularities.

The lower bond strength values recorded for MetaSeal groups may be due to its nature as a methacrylate resin-based sealer which is affected by the configuration of the root canal system which represents the greatest obstacle to root canal adhesion [45] because the unbounded surface area becomes small in root canals and there is insufficient stress relief by flow with associated high risk of pull-off or debond at the interfaces [46].

The results of this study were supported by; Bouillaguet et al. [47]who stated that polymerization shrinkage stresses that developed along the root dentine–resin based sealer interface might result in debonding of the sealer. Moreover, Zhang et al. [48]reported that I Root SP sealer which is based on a calcium silicate composition, does not shrink during setting and hardens in the presence of water. Our findings were in agreement with Ersahan and Aydin [49] and Shokouhinejad et al. [50] who reported that EndoSequence BC Sealer bond strength values were equivalent to those of AH Plus which was higher than that of Hybrid Root SEAL as reported by Lawson et al. [46].

The bond strength values decreased in a coronal to apical direction with statistically significant differences among the three root canal levels in all groups. This may be explained by the fact that apical dentine contains less patent dentinal tubules with more sclerotic dentin which is not favorable for sealer infiltration compared to its coronal counterpart [34]. This agrees with Nagas et al. [51] and Al-Hamed et al. [52].


The disinfection protocol affected push-out bond strength of calcium silicate and resin based sealers. MetaSeal resin-based sealer had lower push-out bond strength values compared with Endosequence BC sealer. Apical root segment showed lower bond strength values than middle and coronal segments.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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