| Abstract|| |
Aim: The aim of this in vitro study was to compare the effects of herbal irrigants with conventional irrigants on microhardness and flexural strength of root dentin.
Materials and Methods: Sixty extracted permanent maxillary canines were selected. Decoronated roots were sectioned longitudinally into buccal and lingual segments to get 120 specimens. These were embedded in auto polymerizing acrylic resin and further grounded with fine emery papers under distilled water. Of these, 100 root segments without any defects were selected , further divided into four test groups and a control group according to the irrigants used (n = 20). Group 1: 2.5% Sodium hypochlorite, Group 2: Miswak stick extract, Group 3: Cashew leaves extract. Group 4: Mango leaves extract and Group 5: Normal saline (control). All specimens were treated with 5 ml of each irrigant for 10 minutes and rinsed immediately. Dentin microhardness was measured with a Vickers indenter, and the flexural strength test was done using a universal testing machine. The data were analyzed using one-way ANOVA and the intergroup comparison by student t-test.
Results: The experimental groups showed a significant reduction in microhardness values when compared with the control group. Intragroup comparison among experimental groups, herbal irrigants showed the least reduction in microhardness values at cervical, middle, and apical thirds. When compared to the control group, the flexural strength values decreased significantly with experimental groups.
Conclusion: Within the limitation of this study, it was concluded that herbal irrigants were least detrimental to root dentin microhardness when compared with conventional irrigant. But the flexural strength was equally reduced by both conventional and herbal irrigants.
Keywords: Anacardium occidentale; dentine microhardness; flexural strength; Mangifera indica; Salvadora persica; sodium hypochlorite
|How to cite this article:|
Philip PM, Sindhu J, Poornima M, Naveen D N, Nirupama D N, Nainan MT. Effects of conventional and herbal irrigants on microhardness and flexural strength of root canal dentin: An in vitro study. J Conserv Dent 2021;24:83-7
|How to cite this URL:|
Philip PM, Sindhu J, Poornima M, Naveen D N, Nirupama D N, Nainan MT. Effects of conventional and herbal irrigants on microhardness and flexural strength of root canal dentin: An in vitro study. J Conserv Dent [serial online] 2021 [cited 2022 Jan 19];24:83-7. Available from: https://www.jcd.org.in/text.asp?2021/24/1/83/320669
| Introduction|| |
The persistence of microorganisms owing to the complex anatomy of the root canals is the primary cause of endodontic failure. A successful endodontic treatment involves complete elimination/disinfection of the bacteria and their byproducts from the infected root canal, which is achieved partly through shaping of the canals but predominantly through antimicrobial irrigants., Excellent antibacterial and tissue dissolution properties make sodium hypochlorite (NaOCl) a widely preferred endodontic irrigant. Some of the disadvantages of using NaOCl include instrument corrosion, burning of surrounding tissues, unpleasant taste, high toxicity, the inability to remove the smear layer, reduction in elastic modulus, and flexural strength of dentin. It has led to the testing of various herbal alternatives as endodontic irrigants. The advantages of using herbal extracts in endodontics are that they have low cost, easy availability, increased shelf life, low toxicity, lack of microbial resistance, better tolerated by patients, and renewable.
Salvadora persica (miswak-siwak) chewing sticks contain trimethylamine, salvadorime chloride, and fluoride in large amounts. A significant reduction in the microbial count observed when 15% ethanolic extract of S. persica used., 5 mg/ml of S. persica solution found to be as active as 17% EDTA in smear layer removal from the coronal third of the root canal. Mangifera indica (mango) and Anacardium occidentale (cashew) belong to the family Anacardiaceae. M. indica stem bark, leaves, roots, and fruits contain mangiferin, a major C-glucosyl xanthone., This has numerous pharmacological activities such as antioxidative, antibacterial, antiviral, anti-inflammatory, and immunomodulatory effects. Mango kernel showed a higher zone of inhibition in a study where the antibacterial efficacy of M. indica L. kernel and Ocimum sanctum L. leaves (tulsi) extracts compared with NaOCl and CHX against Enterococcus faecalis biofilm. Alcoholic and aqueous extract of cashew apple (A. occidentale) displayed significant antimicrobial properties. Leaf extract of A. occidentale had proven to have antibacterial activity against E. faecalis, which was equivalent to chlorhexidine.
In our literature search, we found numerous studies on the antimicrobial effects of the herbal irrigants of Miswak, Mango, and Cashew. Till date, there is limited evidence pertaining to the effect of herbal irrigants on the microhardness and flexural strength of root canal dentin. Hence, only these properties were evaluated. Studies have shown that the microhardness and flexural strength act as physical indicators of dentin.,, Therefore, it is essential to evaluate the effect of irrigating solutions on these mechanical properties of root dentin as they remain in contact with the surface during irrigation. Thus, this study aims to compare the effect of 2.5% NaOCl and herbal extract on microhardness and the flexural strength of root dentine. The null hypothesis was that the herbal irrigants do not have any effect on the microhardness and flexural strength of root canal dentin.
| Materials and Methods|| |
Sixty human noncaries single-rooted maxillary canines, extracted for periodontal reasons, were used in the study. Tissue remnants were gently removed from the extracted tooth surfaces with an ultrasonic scaler (Cavitron; Dentsply, York, PA, USA) further stored in normal saline till use. Decoronation of all teeth at cementoenamel junction, using a diamond disc with low-speed straight handpiece (Horico, Berlin, Germany) underwater cooling is done. One hundred and twenty specimens obtained from longitudinally sectioning the tooth into the buccal and lingual segments. Root segments were mounted horizontally with dentin surfaces exposed using auto polymerizing acrylic resin and further grounded smooth with a series of fine emery papers (Shor International Corporation, Mt. Vernon, NY, USA) under distilled water [Figure 1]. A total of 100 samples without any surface defects were selected after examination under the dental operating microscope (Seiler Revelation Microscope, St. Louis, MO, USA).
|Figure 1: (a) Decoronation, (b) Buccal and lingual segments, (c) root segment embedded in autopolymerising resin, (d) Vickers testing machine |
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Preparation of herbal extracts
Preparation of miswak crude extract
Small pieces of fresh miswak sticks were dried at room temperature for 2 weeks and ground to powder. 10 g of powder was put into a sterile screw-capped bottle to which 100 ml of deionized water was added. The extract was left to soak for 48 h at 4°C and centrifuged for 10 min at 2000 rpm. The supernatant was filtered using a Whatman filter paper. The extract was prepared at 50% concentration and stored at 4°C till use.
Preparation of cashew and mango leaf extract
Leaves free from insect infestation and infection were obtained and shade dried. The dried samples were powdered using a blender, and the extract was obtained by maceration technique. The supernatant collected after the powder was kept immersed in ethanol for 24 h with occasional shaking, filtered through the muslin cloth and Whatman filter paper. Using a rotary evaporator (Heidolph, Germany) at 105°C for 6 h, the solutions of mango and cashew leaves were dried. The dried extracts were then re-dissolved in 10% dimethyl sulfoxide to yield solutions containing 100 mg of extract per millimters. The obtained extracts were stored in an airtight screw cap tubes at −4°C till use.
The specimens randomly divided into four test groups and a control group according to the irrigants used (n = 20): (G1) 2.5% NaOCl, (G2) Miswak stick extract, (G3) Cashew leaves extract, (G4) Mango leaves extract, and (G5) Normal saline (control). All specimens treated with 5 ml of each irrigant for 10 min. Following which the samples were rinsed immediately with distilled water.
Evaluation of microhardness
The specimens kept hydrated in saline during the microhardness experiment. Pretreatment dentin microhardness values (M1) of all samples were measured with Vickers diamond indenter (Matsuzawa MMT7, Matsuzawa SEIKI Co. Ltd., Tokyo, Japan) at three different locations (cervical, middle, and apical part) using a 200 g load and a 20 s dwell time. The indentations were placed at 0.5 mm level to the root canal wall at a depth of 100 μm from the pulp-dentin interface, without any overlap between them. Posttreatment microhardness values (M2) were recorded for each specimen after treatment with respective irigants for 10 min, adjacent to the initial indentations using the same method. The length of the two diagonals was used to calculate the microhardness value. For each reagent, the decreased microhardness was calculated in (%) percentage.
Evaluation of flexural strength
The lingual halves of the longitudinally sectioned teeth of measurements 13 mm length × 3 mm wide × 0.3 mm thick collected in the assessment of flexural strength. The test carried out using a miniature three-point flexure device with a 5 mm support span. Each beam was placed on the support span and loaded to fracture in water using a universal testing machine (Instron 4444; Instron Corporation, Canton, USA) at a crosshead speed of 1 mm/min. Flexural strength (MPa) calculated with the formula: 3PL/2bd2,
Where: P = load of fracture (N)
L = length of support span (mm)
b = beam width (mm)
d = beam thickness (mm).
The microhardness and flexural strength data were tabulated and mean, standard deviation calculated for each group. Statistical analysis (intragroup comparison) was done using one-way ANOVA and the intergroup comparison by Student's t-test. Data were analyzed using the IBM SPSS Statistics for Windows version 15 (IBM Corp., Armonk, NY, USA). Significance was established at P < 0.05 level.
| Results|| |
The differences in the M1 and M2 values at the cervical, middle, and apical thirds of root dentine were analyzed [Table 1]. When compared with the control group, a statistically significant reduction in microhardness was observed among the experimental groups (P < 0.05) and no significant difference between herbal irrigant groups (cashew, mango, and miswak) (P > 0.05).
|Table 1: Means and standard deviations of the microhardness and flexural strength of root|
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Intragroup comparison of regional microhardness values of root dentin at the cervical, middle, and apical thirds irrigated with herbal extracts showed no statistically significant difference (P > 0.05). However, a significant difference observed between NaOCl and herbal extract groups (P < 0.05).
A significant reduction in the flexural strength observed between the experimental groups and the control group (P < 0.05). However, no statistically significant difference found in flexural strength values among specimens treated with herbal irrigant and NaOCl (P > 0.05) [Table 1].
| Discussion|| |
The present study designed to compare and evaluate the effects of irrigants on the dentin flexural strength and microhardness. The flexural strength and microhardness properties are clinically relevant as they act as indicators of the amount of force required for the failure of cohesive bonds within dentin and mineral loss or gain in dental hard tissues, respectively. The alteration in these properties after root canal treatment may predispose the tooth to fracture. Dentin microhardness was tested by the Knoop indenter microhardness test, or the Vickers indenter method. However, the Vickers microhardness test was used in this study. The flexural strength was measured using a three-point bend test. Since the tested dentine bars behaved as brittle materials, the cross-head speed of the load testing machine was set as low as 0.1 mm to 1.0 mm/min to record the load-displacement curves.
Currently, herbal products as endodontic irrigants are becoming the choice since present formulations contain mostly antibiotics, antimicrobial agents, surfactants, and alcohol, which are not entirely efficient in eradicating oral pathogens and also they found to be cytotoxic.
The leaf part of plants chosen because they contain more secondary metabolites that are responsible for the antimicrobial property.
In vitro tests done with tannin-containing extract have demonstrated that such compounds have diverse antibacterial and antifungal activities. The presence of tannins in miswak, mango, and cashew extract believed to be the reason for their antimicrobial activity. Tannins possess free-radical scavenging property by complexing with metal ions, thereby preventing cellular oxidative damage, including lipid peroxidation. It is also capable of combining with other types of molecules such as proteins and polysaccharides.
Miswak extract at 50% concentration showed better antimicrobial activity against Lactobacillus acidophilus when compared to neem and mango extracts. It might be due to benzyl isothiocyanate, a natural component of miswak, which acts as an inhibitor of bacterial multiplication. 50% aqueous mango extract was effective against both Streptococcus mutans and L. acidophilus. It could be due to the antioxidant and antilipid peroxidation activities of bitter gum, resins, and mangiferin (polyphenol).
Cashew and mango leaf extract significantly produced a larger zone of inhibition when tested against E. faecalis, Staphylococcus aureus, S. mutans, Escherichia coli, and Candida albicans. The presence of bioactive components in plant extracts could have attributed to the inhibitory effect further disrupting microbial biofilm.
Dentin contains 22% organic material, mainly collagen type I. Depletion of which causes morphologic disorganization and change in mechanical properties., Alteration in morphology, physical, and chemical properties of the dentin observed when different root canal irrigants and irrigation protocols were used. A robust significant reduction in microhardness values was observed with experimental groups when compared with the control group. In the present study, 2.5% NaOCl significantly reduced dentin microhardness when compared with herbal irrigants and normal saline. The reason is NaOCl breaking down long peptide chains and chlorinating the protein terminal groups. The resulting N-chloramines further be broken down into other species. Herbal irrigants had no significant effect on the microhardness. The results are following the study done by Prabhakar et al., which concluded that irrigation with herbal extract (6% Morinda citrifolia juice) did not affect the microhardness of root dentin. Anacardic acid in cashew significantly reduces dentin erosion in vitro, possibly by acting as an MMP-2 inhibitor. Siwak extracts were found to increase the microhardness values of demineralized enamel surfaces. The Vickers hardness results exhibited the enhanced hardness of GIC-reinforced AgNps (silver nanoparticles were prepared by a novel green synthesis technique using M. indica (Mango leaves) compared to GIC and GIC-reinforced silver microparticles.
Intragroup comparison of microhardness between experimental groups at the cervical, middle, and apical thirds posttreatment showed that herbal irrigants had no significant alterations at any part of the root canal dentin. Lewinstein et al and Pashley et al, reported an inverse correlation between dentin microhardness and tubular density., Microhardness of dentin reduced from superficial to deep regions because more number of widely opened dentinal tubules found near the pulp, which offers the least resistance to the microhardness testing indenter. NaOCl, because of its low surface tension, can penetrate narrow and long dentinal tubules by capillary forces or by diffusion/flow into the dentin. It could be the reason why the samples irrigated with 2.5% NaOCl showed a statistically significant reduction in the apical region compared to the cervical and middle areas. No changes with microhardness were observed with an apical third when herbal irrigants used.
NaOCl caused a maximum reduction in flexural strength, followed by the herbal irrigants. Despite its alkaline nature, the acidification process promoted by the OCl- anion of NaOCl contributes to the loss of minerals in dentin. It leads to the formation of a “ghost mineral layer” of sparse collagens generating a friable mineral matrix, resulting in a reduction of flexural strength as a deleterious effect. However, an intergroup analysis showed no significant statistical difference among all the experimental groups, for which the reason is yet unclear.
It is the first kind of study testing the effectiveness of extracts of cashew and mango leaves, miswak sticks on the microhardness and flexural strength of root dentin. While the current data look promising, further studies recommended providing results that could justify the clinical applications of the abovementioned herbal irrigants in endodontics.
| Conclusion|| |
Within the limitations of this in vitro study, herbal irrigants showed the least changes in microhardness and flexural strength of root dentin. There was no significant intragroup difference among the herbal irrigants tested at different levels of the root dentin. Further studies evaluating the effect of different concentrations of herbal irrigants in clinical situations are required.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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Dr, J Sindhu
Department of Conservative Dentistry and Endodontics, Vydehi Institute of Dental Sciences and Research Centre, #82, EPIP Area, Whitefield, Bengaluru - 560 066, Karnataka
Source of Support: None, Conflict of Interest: None