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 Table of Contents  
ORIGINAL ARTICLE
Year : 2015  |  Volume : 5  |  Issue : 2  |  Page : 87-92

Evaluation of the effect of calcium hydroxide and propolis intracanal medicaments on the push-out bond strength of a resin-based endodontic sealer to the root canal dentin: An in vitro study


Department of Conservative Dentistry and Endodontics, College of Dental Sciences, Davangere, Karnataka, India

Date of Web Publication10-Mar-2016

Correspondence Address:
Dr. Ravi Bhargavi
Department of Conservative Dentistry and Endodontics, College of Dental Sciences, Davangere, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2231-6027.178498

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  Abstract 

Introduction: The aim of this study was to evaluate the effects of calcium hydroxide [Ca(OH)2] and propolis intracanal medicaments on the push-out bond strength of a resin-based sealer (AH Plus) to root dentin. Materials and Methods: After chemomechanical instrumentation using ProTaper rotary system, three groups of root canal specimens were prepared: 10 root canals were left untreated as controls (G1), 10 received Ca(OH)2intracanal medicament (G2), and another 10 received propolis intracanal medicament (G3). Canals were obturated with AH Plus and gutta-percha. After bond strength evaluation using push-out test, data was analyzed using 2- way ANOVA and Tukey post hoc tests (P = 0.05). Results: At coronal and middle thirds, there were no significant differences in bond strength among the three groups (P > 0.05). At apical third, G3 was significantly superior to G2 and G1 (P < 0.05), but there was no significant difference between G2 and G1 (P > 0.05). Conclusion: The use of propolis as an intracanal dressing material, with AH Plus used as the sealer in endodontic therapy was shown to have better sealer-dentin interfacial bond strength.

Keywords: AH plus, bond strength, calcium hydroxide, propolis


How to cite this article:
Shivanna V, Bhargavi R. Evaluation of the effect of calcium hydroxide and propolis intracanal medicaments on the push-out bond strength of a resin-based endodontic sealer to the root canal dentin: An in vitro study. Int J Oral Health Sci 2015;5:87-92

How to cite this URL:
Shivanna V, Bhargavi R. Evaluation of the effect of calcium hydroxide and propolis intracanal medicaments on the push-out bond strength of a resin-based endodontic sealer to the root canal dentin: An in vitro study. Int J Oral Health Sci [serial online] 2015 [cited 2019 Dec 7];5:87-92. Available from: http://www.ijohsjournal.org/text.asp?2015/5/2/87/178498


  Introduction Top


An effective cleaning and shaping of the root canal walls is one of the main goals of the endodontic treatment. Although root canal instrumentation procedures have been improved considerably over the years, no current technique is able to provide a complete cleaning of the root canal system, especially in narrow, curved or flattened roots.[1]

Even after meticulous biomechanical preparation, bacteria may survive, grow and multiply, having an important role in the outcome of endodontic treatment.[2] The use of an effective intracanal dressing has been suggested by several studies as an important procedure for bacterial reduction.[2],[3]

Ca(OH)2 is the most widely used and investigated intracanal dressing material in endodontics because of its antibacterial and biological properties.[2] However, clinical studies have shown that it is not possible to sterilize root canals in necrotic teeth, even with Ca(OH)2.[4],[5] Itis also shown to be potentially toxic due to its high pH.[6] Therefore, new therapeutic agents (such as chlorhexidine, antibiotics) and natural products (propolis) were suggested to be used as alternative intracanal medicaments.[7]

An antimicrobial agent, propolis has gained the attention of researchers in recent times because of its antibacterial, antiviral, antifungal, antiprotozoal, anti-inflammatory and antioxidant effects.[8] Propolis is a resinous hive product. The antibacterial activity of propolis is reportedly due to flavonoids, aromatic acids and esters present in the resin.[9] Ethanolic extract of propolis has proved to be an effective intracanal medicament in teeth infected with  E.faecalis Scientific Name Search .[10],[11] It was shown to be useful as a root canal dressing because of its low toxicity and broad antibacterial spectrum.[12]

In addition to the antimicrobial properties, intracanal medications should be easy to remove from the root canal walls.[13],[14] The obstruction of dentinal tubules, by either smear layer or intracanal medication can impair the performance of endodontic sealers.[15],[16]

The purpose of the present in vitro study was to evaluate the effect of propolis paste, used as an intracanal medicament, on the bond strength of AH Plus sealer (Dentsply DeTrey, Konstanz, Germany) to root dentin, using push-out test.


  Materials and Methods Top


Preparation of propolis

Three-hundred grams of frozen propolis was ground and dissolved in 300 ml 96% ethanol at 37°C to obtain 100% (w/v) extract. The mixture was poured into a bottle and incubated at 30°C for 2 weeks. After incubation, the supernatant mixture was filtered twice with Whatman no. 4 and 1 filter paper. The filtered mixture was concentrated at 30°C for 6 hours (1500 rpm). The final extraction of propolis powder obtained had a density of 150 mg/mL.[17] [prepared in collaboration with pharmaceutical college].

Root canal specimen groups

30 mandibular premolars were collected and the specimens were immersed in 0.5% Chloramine-T-solution (Global Chemicals, UK) for 48 hours for disinfection and then stored in distilled water until they were used.

After the teeth were cleaned, standardized root lengths of 15 mm were obtained by sectioning the roots perpendicularly at the cementoenamel junction using a diamond disk. The working length was determined using a size 10 K-file (Dentsply Maillefer) and further root canal preparation was done using ProTaper rotary instruments (Dentsply Maillefer) upto an F4 (size 40.,06 taper). At every instrument change, the canals were irrigated with 2 mL 2.5% sodium hypochlorite solution (NaOCl) (Nice Chemicals Pvt Ltd., India). A final flush was applied using 5 mL 17% EDTA (Raman Research Products, India) and 5 mL physiologic saline solution. The specimens were dried using sterile absorbent paper points.

After chemo-mechanical preparation, the roots were randomly divided into three groups according to the intracanal medicament received:

Group 1: Ten root canals did not receive any intracanal medicament.

Group 2: Ten root canals received Ca(OH)2 intracanal medicament. The Ca(OH)2 paste in this group was prepared by mixing calcium hydroxide powder with distilled water until a creamy consistency (1:1.5, p/l ratio) was reached.

Group 3: Ten root canals received propolis intracanal medicament, which was manipulated using glycerine until a creamy consistency was reached.

The prepared pastes were placed into the root canals using a size #40 Lentulo spiral. The coronal openings of the canals were sealed with a small cotton pellet and temporary filling material (Cavit G, 3M ESPE, Germany) to avoid leakage. In the control group, coronal access was directly sealed with Cavit G without intracanal medicament. The specimens were stored at 37°C in 100% humidity for 3 weeks to simulate clinical conditions.[18],[19]

After 3 weeks, the medicaments were rinsed with 10 mL 17% EDTA followed by 10 mL 2.5% NaOCl.[19] and a final irrigation with 5 mL physiologic saline solution. Subsequent to the procedures, the root canals were dried using paper points. A single gutta percha cone of F4 was then slightly coated with sealer and placed into the canals till working length. After root filling, the coronal opening was filled with Cavit G and the specimens were stored at 100% humidity at 37°C for 1 week to completely set.

Each specimen was sectioned perpendicular to the longitudinal axis of the root by using a low-speed diamond saw (Minitom, Struer, Denmark) under water cooling. Three slices of 1 ± 0.1 mm thickness were obtained from each tooth (n = 30 for each group) at depths of 4, 7, and 10mm (apical, middle, and coronal regions). The diameter of each hole from the apical and coronal aspects was measured under a stereomicroscope at 32X magnification. The push-out test was performed on each specimen with a universal testing machine at a crosshead speed of 1mm/min using 0.6-, 0.7-, and 0.8-mm diameter cylindrical pluggers, matching the diameter of each canal third. The diameter of the plugger used was approximately (at least) 80% of the diameter of the canal. The maximum load 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)

The adhesion area of the root canal filling was calculated using the following equation:

is the smaller radius, r2 is the larger radius of the canal diameter (mm), h represents the thickness of the root section (mm), and π is the constant 3.14. After the test procedure, each specimen was visually examined under a stereomicroscope at 32X magnification to evaluate the failure type. Three types of failure were categorized: Adhesive failure (between the sealer and root dentin), cohesive failure (within the sealer or root dentin), and mixed (a combination of cohesive and adhesive).[20]

Stastistical analysis

The data was analysed using 2-way analysis of variance and Tukey posthoc tests to detect the effect of the independent variables (intracanal medicaments and root canal thirds) and their interactions on the push-out bond strength of the root canal filling material to the root dentin (P = 0.05). The failure mode data was statistically analysed using the Chi-square test (P = 0.05). All statistical analyses were performed by using software (SigmaStat for Windows Version 3.5; Systat Software, Inc, Erkrath, Germany) at a significance level of 0.05 and a confidence interval of 95%.


  Results Top


Push-out strength

At each root canal region, statistical comparisons were performed among the three experimental groups. At apical-third region, there was significant differences between Ca(OH)2 and propolis groups (P < 0.05), while there was no significant difference between Ca(OH)2 and control groups (P > 0.05). At coronal and middle third regions, there were no significant differences among the three experimental groups (P > 0.05) [Table 1] and [Figure 1].
Table 1: Mean and standard deviation values of push-out strength (in MPa) of the root canal filling material to the root dentin after being treated with different intracanal medicaments according to the root canal thirds. For each root third, different letters in superscript indicates statistically significant difference amongst them (P < 0.05)

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Figure 1: Comparison of Mean push-out bond strength values (MPa) of sealer to root canal dentin according to different intracanal medicaments and root canal thirds

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Failure modes

Adhesive failure was the least observed failure mode for all the three groups. Cohesive and mixed failure modes accounted for most of the failures which occurred [Table 2].
Table 2: Failure mode distribution of Groups 1-3 (in percentage, %) according to root canal region

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  Discussion Top


The success of endodontic treatment depends on what is removed during cleaning and disinfection as well as what is placed during obturation. To render the root canal system optimally bacteria-free, intracanal medicaments have been highly advocated for root canal disinfection.[21],[22]

The dissociation of Ca(OH)2 into OH - and Ca 2+ depends on the vehicle used to prepare the paste. Simon et al.[23] demonstrated that the vehicle can exert a great influence on the release of ions. Safavi and Nakayama [24] concluded that high concentrations of glycerin and propylene glycol as mixing vehicles may decrease the effectiveness of Ca(OH)2 as a root canal dressing. The calcium hydroxide-water combination showed significantly higher pH values than the other pastes in clinical use.[25]

Ca(OH)2 is not an effective intracanal medicament against all types of bacterial species found in endodontic infections.[26] For example, Ca(OH)2 could not efficiently eliminate enterococci, which were isolated in one third of the endodontic retreatment cases, due to their abilities to survive in a high-pH environment and to invade dentinal tubules and adhere to collagen in the presence of human serum.[27]

Propolis, a centuries-old natural antibiotic, has also been used as an intracanal medicament owing to its good antimicrobial activity against a wide range of bacterial species.[28],[29] Therefore, propolis could be used as an alternative intracanal medicament in cases of persistent endodontic infections.

Several authors have evaluated the difficulty of removing intracanal medicaments from root canal walls, especially in their apical part [30] that could adversely affect dentinal bond strength and compromise endodontic sealing. A study done by Rodig et al.[31] on the efficacy of different irrigating solutions in the removal of Ca(OH)2 from root canals, showed that chelating agents like citric acid and EDTA displayed the best results. Victorino et al.,[12] evaluated the removal efficiency of inter-appointment endodontic dressing materials [Ca(OH)2 paste and propolis paste] using 2.5% NaOCl and 17% EDTA and saline as final irrigation solutions. They found no significant differences in root canal cleanliness for the removal of propolis or Ca(OH)2 root canal dressings with these irrigants.

The single cone technique was developed to overcome the disadvantages of lateral condensation technique, such as: Lack of gutta-percha homogeneity, high percentage of endodontic cement at the apical portion of the root, poor adaptation to the root canal walls, apical extrusion of the gutta-percha and high incidence of vertical root fractures.[32] The single cone technique speeds the root canal filling while minimizes the pressure applied to the root canal walls. The combination of single cone and endodontic cement results in a uniform mass which prevents failures observed among multiple cones.[33]

Limited data are available in the literature about the effects of propolis pastes on the bond strength of an epoxy resin-based 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. Akcay et al.[34] investigated the effects of calcium hydroxide and double and triple antibiotic pastes on the bond strength of epoxy resin-based sealer (AH Plus Jet) to root dentin. They reported that there was no significant affect on the bond strength of the epoxy resin-based sealer with the use of double antibiotic paste and calcium hydroxide. Additionally, TAP improved the bond strength of the epoxy resin-based sealer in the middle and apical thirds which was attributed to the binding capacity of minocycline to calcium ions via chelation. Amin et al.[35] showed that the use of Ca (OH)2 as intracanal medicament, did not affect the bond strength of an epoxy resin-based sealer (AH Plus), which was in in agreement with the above study done by Akcay et al.[34]

In the present study, at apical third, the propolis group showed significantly superior push-out bond strength compared with the Ca(OH)2 and the control group. These results are in accordance with the study done by Ustun et al.,[7] in which the micro push-out bond strength of propolis group was significantly superior to those of Ca(OH)2 and control groups (P < 0.05) at apical third. The possible reasons behind this might be due to the binding of the hydrophilic components of propolis paste preferably to the hydrophilic dentin surface. Moreover, since the circulation volume of irrigation solutions at apical third was lower than at coronal and middle thirds, removal of propolis paste which had a resinous sticky form from the root dentin walls became more difficult.[7] Apart from this, the resin ingredients of propolis paste [36] could be responsible for binding to AH Plus sealer, thus accounting for the higher push-out bond strength at apical third.

At coronal and middle thirds, there were no significant differences in micro push-out bond strength among the three experimental groups in this study (P > 0.05), which was in agreement with the study done by Ustun et al.[7] The reason for this being that, root canal space at coronal and middle thirds is anatomically larger than that at apical third. Therefore, with a higher circulation volume of irrigation solutions at the coronal and middle thirds of root canal space than at apical third, it facilitates the removal of smear layers and intracanal medicaments.[7]

No adhesive failures were observed for propolis group at apical third in the present study, but not so for the control and Ca(OH)2 groups [Table 2], which could be explained by the high bond strength of propolis group at apical third. Similar results were obtained in the study done by Ustun et al.[7] The predominant occurrence of cohesive and mixed failures in this study could be explained by the size similarity between the diameter of cylindrical plunger and that of prepared root canals. Therefore, the plunger was in full contact with the root filling material on loading, consequently leaving only root canal sealer on dentin.[30]

Based on the results of the present study, the use of propolis as an inter-appointment dressing material improved the push-out bond strength of AH Plus root canal sealer at apical third. However, the chemical reaction between the resin ingredients of propolis and epoxy resin should be further investigated.


  Conclusion Top


Within the limitations of the present study, it can be concluded that propolis group showed significantly superior push-out bond strength than Ca(OH)2 and control groups at apical third when used with an epoxy resin-based sealer such as AH Plus. But, further studies are needed to prove that propolis could be a better intracanal medicament than Ca(OH)2 as it also improved dentin bond strength.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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