| Abstract|| |
Aim: To evaluate the effects of calcium hydroxide (CH), triple and double antibiotic pastes (DAPs) on the bond strength of Smart-Seal obturation, C-points with Endosequence Bio-ceramic (BC) sealer to the root canal dentin.
Materials and Methods: Sixty-four freshly extracted single-rooted human mandibular premolars were de-coronated and prepared using rotary Pro-taper system with full sequence till F3. The specimens were randomly divided into a control group (without intracanal dressing) and 3 experimental groups that received an intracanal dressing with either CH, DAP, or triple antibiotic paste (TAP) (n = 16). The intracanal dressing was removed after 3 weeks by rinsing with 10 mL 17% ethylenediaminetetraacetic acid, followed by 10 mL 3% sodium hypochlorite. The root canals were then obturated with C-points and Endosequence BC sealer. A push-out test was used to measure the bond strength between the root canal dentin and the obturating system. The data were analyzed using two-way analysis of variance and Tukey post-hoc test.
Results: The push-out bond strength values were significantly affected by the intracanal medicaments (P < 0.001), but not by the root canal thirds (P > 0.05). In the middle and apical third, the bond strength of the TAP group was higher than those of the CH and DAP groups (P < 0.05).
Conclusions: The DAP and CH did not affect the bond strength of the novel hydrophilic obutrating system. TAP improved the bond strength of Smart-Seal system in the middle and apical thirds.
Keywords: Hydrophilic; intracanal medicaments; push-out bond strength
|How to cite this article:|
Hegde V, Arora S. Effect of intracanal medicaments on push-out bond strength of Smart-Seal system. J Conserv Dent 2015;18:414-8
| Introduction|| |
The ultimate goal of root canal treatment is to eliminate bacteria and their by-products. Thus, the conjunction of instrumentation along with various irrigation solutions and medicaments has been suggested. ,, As the infections of the root canal system are known to be polymicrobial in nature, antibiotic combinations have been recommended.  Calcium hydroxide (CH) is the most frequently used medicament because of its antimicrobial efficacy against most bacterial species identified in endodontic infections.  Triple antibiotic paste (TAP) containing metronidazole, ciprofloxacin, and minocycline has been reported to be a successful regimen in controlling the root canal pathogen and in managing nonvital young permanent tooth. The triple-antibiotics regimen was first tested by Sato et al.  Studies have shown that minocycline causes visible crown discoloration  and therefore minocycline was eliminated in a double antibiotic paste (DAP) that consists of only ciprofloxacin and metronidazole.  In addition to the undesired discoloration, another problem in the use of antibiotic pastes is that it is not possible to remove the pastes from the root canals completely which could have an effect on the adhesion of endodontic sealers to the root canal dentinal walls.  In a recent study by Yassen et al. it was shown that CH and antibiotic pastes caused degradation or demineralization of the radicular dentin. Several studies showed that CH negatively affected various mechanical properties of the radicular dentin  and the alkaline pH of the CH could cause neutralization and denaturation of dentin organic proteins.  Adhesion of the sealers to the root canal dentin by close contact is important to resist micromechanical forces during root canal treatment.  In today's era newer obturating systems are being introduced in order to have a superior seal as compared to the gold standard hydrophobic Gutta-percha/AH Plus system. In the wake of concept on improving the bonding and achieving a hydrophilic seal C-points (EndoTechnologies, LLC, Shrewsbury, MA) were introduced. These obturating points (C-points) contain a polyamide core with an outer bonded hydrophilic polymer coating. The endodontic points are designed to expand laterally without expanding axially by absorbing residual water from the instrumented root canal space and the naturally present moisture in the dentinal tubules.  A bio-ceramic (BC) root canal sealer has been introduced, commercially known as Endosequence BC sealer (Brasseler USA, Savannah, GA). Endosequence BC sealer is a premixed and injectable endodontic sealer, and its nanoparticle size allows it to flow into canal irregularities and dentinal tubules. It is hydrophilic and uses the moisture in dentinal tubules to initiate and complete its setting reaction. Currently, there is no literature analyzing the effect of intracanal medicaments on the push-out bond strength of novel hydrophilic obturation systems, C-points and Endosequence BC sealer. Therefore, the aim of this study was to evaluate the effects of TAP, DAP, and CH on the bond strength of a hydrophilic system to root canal dentin. The null hypothesis was that there would be no difference between the medicaments in terms of the push-out bond strength of the C-points/Endosequence BC sealer.
| Materials and Methods|| |
Sixty-four freshly extracted human mandibular premolars were selected for this study. The specimens were immersed in 0.5% Chloramine T solution (Merck, Darmstadt, Germany) for 48 h for disinfection. They were then stored in distilled water until they were used. The soft tissue and calculus were removed mechanically from the root surfaces with a periodontal scaler. The teeth were verified radiographically as having a single root canal without calcification. The exclusion criteria consisted of a tooth having more than a single root canal and apical foramen, root canal treatment, internal/external resorption, immature root apices, caries/cracks/fractures on the root surface, and/or root canal curvature of more than 10°. The specimens were de-coronated using a diamond disk to acquire a standardized root length of 15 mm. A size 10 K-file (DentsplyMaillefer, Ballaigues, Switzerland) was placed in the canal until it was visible at the major apical foramen, and the working length was determined by subtracting 1 mm from this measurement. The root canals were prepared using Pro-taper rotary instruments (DentsplyMaillefer) to F3 (size 30/.06 taper). The root canals were irrigated with 2 mL 5% sodium hypochlorite (NaOCl) between the instrument changes. A final flush was applied using 5 mL 17% ethylenediaminetetraacetic acid (EDTA) for 60 s and 5 mL 3% NaOCl for 60 s. The specimens were dried using paper points (DentsplyMaillefer) and were randomly divided into a control group (without intracanal dressing) and 3 experimental groups that received an intracanal dressing with either CH, DAP, or TAP (n = 16).
Preparation of the intracanal medicaments
In the CH group, the CH paste in this group was prepared by mixing CH powder (Kalsin; Spot Dis Deposu AS, Izmir, Turkey) and distilled water. In the DAP group, equal amounts of metronidazole and ciprofloxacin were mixed with distilled water. Equal amounts of metronidazole, ciprofloxacin, and minocycline were mixed with distilled water in the TAP group. The powder/liquid ratios of the pastes were 3:1 with similar concentrations as those used in the study by Hoshino et al. The prepared pastes were placed into the root canals using a size no. 40 Lentulo spiral. The coronal openings of the root canals were sealed with a small cotton pellet and temporary filling material (Cavit, 3M ESPE, Germany) to avoid leakage. The specimens were stored at 37°C in 100% humidity for 3 weeks to simulate clinical conditions.  After 3 weeks, the medicaments were rinsed with 10 mL 17% EDTA followed by 10 mL 3% NaOCl and a final irrigation with 5 mL distilled water. Subsequent to the procedures, the root canal was dried using paper points (DentsplyMaillefer). A C-point (F3, Endotechnologies. Pvt. Ltd.,) was then coated at the apical third with Endosequence BC sealer and placed in the root canal to the working length. Because the root canals were prepared using rotary instruments up to F3 files, all specimens were obturated using the single cone technique with matching taper F3 C-points cones to obtain standard specimens for the push-out test. Mesiodistal and buccolingual radiographs were taken to confirm complete filling. After root filling, the coronal opening was filled with a temporary filling material, and the specimens were stored at 100% humidity at 37°C for 1 week to set completely. Each specimen was sectioned perpendicular to its long axis using a precision saw (IsoMet 1000; Buehler, Lake Bluff, IL) at a slow speed under water cooling. Three slices were obtained from each tooth (n = 48 for each group) at depths of 4, 7, and 10 mm (apical, middle, and coronal) and approximately 1 ± 0.1 mm thickness. The diameter of each hole from the apical and coronal aspects was measured under a stereomicroscope (Zeiss Stemi2000C; Carl Zeiss, Jena, Germany) at ×32 magnification. The push-out test was performed on each specimen with a universal test machine (AGS-X; Shimadzu Corp, Tokyo, Japan) at a crosshead speed of 1 mm/min using 0.6, 0.7, and 0.8 mm diameter cylindrical pluggers, matching the diameter of each canal third. The diameter of the pluggers was approximately (at least) 80% of the diameter of the canal. The maximum load had applied to the filling material before failure was recorded in newtons and converted to megapascals (MPa) according to the following formula:
Push-out bond strength (MPa) = maximum load (N)/adhesion area of root filling (A) (mm 2 )
| Results|| |
A two-way analysis of variance indicated that the push-out bond strength values were significantly affected by the intracanal medicaments (P < 0.001) but not by the root canal thirds (P > 0.05). However, there were significant interactions between the intracanal medicaments and the root canal thirds (P = 0.003). The mean and standard deviation of the push-out bond strength values (MPa) of the sealer to the root canal dentin according to the various intracanal medicaments in the root canal third are indicated in [Table 1] and [Figure 1]. In the coronal third, there were no statistically significant differences among the groups (P > 0.05). In the middle third, the bond strengths after CH and DAP were similar to that of the control group, and the bond strength after TAP was also similar to that of the control group (P > 0.05). However, the bond strength of the TAP group was higher than those of the CH and DAP groups in the middle third (P < 0.05). In the apical third, the bond strength of the TAP group was higher than those of the control groups and the CH (P < 0.05) and DAP (P < 0.05) groups.
|Figure 1: Mean push-out bond strength values (megapascals) of sealer to root canal dentin according to the different medicaments and the root canal thirds|
Click here to view
| Discussion|| |
TAP has been used most often during revascularization procedures to disinfect the root canal system in necrotic immature teeth.  In addition, the paste can also be used traditionally in root canal treatment in infected root canals before root canal obturation with sealer because of its good antimicrobial properties.  Antibiotic pastes can influence the bond strength of the root filings negatively or positively. The null hypothesis was that there would be no difference between the medicaments in terms of the push-out bond strength of the Smart-Seal obturation. However, our findings indicated that the bond strength of the TAP group was higher than those of the CH and DAP groups in the middle and apical thirds. Thus, the null hypothesis was rejected. The number and density of dentinal tubules vary along the root canal thirds.  However, it has been reported that the alterations in tubular density along the canal walls are unlikely to change the adhesion of root canal sealers.  In this study, the bond strength primarily decreased in the coronal to apical direction without any medicaments. This result is comparable with results from several studies showing that the adhesion of root sealers generally decreased in the coronal to apical direction.  This can be explained by the decreasing tubule density from coronal to apical, which reduces sealer penetration into the smaller tubule diameter in the apical thirds.  The lack of access to the apical region of irrigation solutions and the consequent incomplete removal of the smear layer may decrease the penetration of sealer into dentinal tubules and may thereby affect adhesion in the apical region.  C-points are endodontic points designed to expand laterally without expanding axially by absorbing residual dihydrogen monoxide from the instrumented root canal space and the naturally present moisture in the dentinal tubules.  The inner core of C-points is composed of two proprietary nylon polymers: Trogamid T and Trogamid CX. The polymer coating is a cross-linked copolymer of acrylonitrile and vinyl-pyrrole, which has been polymerized and cross-linked utilizing allyl methacrylate and a thermal initiator. The lateral expansion of C-points occurs nonuniformly, with the expand-ability depending on the extent to which the hydrophilic polymer is prestressed (i.e., contact with a canal wall will reduce the rate or extent of polymer expansion).  Thus, C-points may also play a key role in enhancing the push-out bond strength itself as well as the sealer. Arslan et al. compared the efficacy of different irrigation protocols on the removal of TAP from artificial grooves in root canals in a recent study, and they showed that it was difficult to remove TAP from the root canals using irrigating solutions. In another current study, Berkhoff et al.  showed that TAP was not effectively removed from the root canal systems, and more than 80% of the TAP is retained in the root canal system regardless of the irrigation technique used. Meanwhile, CH was effectively removed with significantly less residual presence; circumferentially. These results were attributed to the penetration and binding into the dentin of the TAP. Tanase et al. also indicated that minocycline in the TAP binds to calcium ions via chelation to form an insoluble complex in the tooth matrix. The highest bond strength values after TAP application could depend on a number of reasons, the most likely being the binding of residual minocycline to the calcium ions via chelation, which could increase bond strength after the application of TAP with minocycline. Moreover, the increasing bond strength of TAP may be related to less irrigant reaching the apex by the extension of a greater residual minocycline presence. In this study, the residual antibiotic paste on the root canal walls was not evaluated. Future studies should be conducted to understand the mechanisms between the materials and residual minocycline. In the present study, a resin based BC sealer was used. Greater bond strengths in the middle and apical third with this sealer can be attributed to the interaction between the epoxy resins based sealer and exposed amino groups from the collagen to create a covalent bond between them.  Another factor could be that apical level has marked variation in structure, including irregular secondary dentin, accessory canals.
Limited data are available in the literature about the effects of antibiotic pastes on the bond strength of C-points/Endosequence BC sealer to root dentin. Thus, the findings of this study can only be compared with the research in which the effects of various medicaments on the bond strength of root canal sealers were evaluated. In this study, the TAP group showed significantly superior push-out bond strength compared with the CH and DAP groups at the middle third as well as being superior to all of the groups in the apical third. A recent study showed that it was difficult to remove TAP from the root canals using irrigating solutions. Nevertheless, the researchers found that the use of 2.5% NaOCl improved the removal of TAP.  In a different study by Rödig et al. the efficacy of different irrigating solutions in the removal of CH from the root canals was evaluated. According to those findings, chelating agents like citric acid and EDTA displayed the best results. Based on the findings of the aforementioned studies, in the present study, 10 mL 17% EDTA, followed by 10 mL 3% NaOCl was used to remove intracanal medicaments. Therefore, with the greater use of hydrophilic root canal obturating material and concurrent and undeniable use of the intracanal medicaments, it is important to know the clinic effects that they exhibit on each other.
| Conclusion|| |
The use of TAP increased the push-out bond strength of the hydrophilic obturating material. This can be attributed to the remaining minocycline present in the canal due to chelation. Greater bond strengths were observed in the middle and apical third with TAP. Furthermore, studies would be required to evaluate the exact mechanism of the increase in the bond strength as well as the setting mechanisms of hydrophilic obturating materials.
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Conflicts of interest
There are no conflicts of interest.
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Dr. Shashank Arora
1301 Glen Eagle Apt. Ambedkar Road, Parel, Mumbai 400012, Maharashtra
Source of Support: None, Conflict of Interest: None