Journal of Pharmacy And Bioallied Sciences

DENTAL SCIENCE - ORIGINAL ARTICLE
Year
: 2012  |  Volume : 4  |  Issue : 6  |  Page : 125--130

The effects of various irrigating solutions on intra-radicular dentinal surface: An SEM analysis


JV Karunakaran, S Senthil Kumar, Mohan Kumar, S Chandrasekhar, D Namitha 
 Department of Conservative Dentistry, JKKN Dental College, Komarapalayam, Tamil Nadu, India

Correspondence Address:
J V Karunakaran
Department of Conservative Dentistry, JKKN Dental College, Komarapalayam, Tamil Nadu
India

Abstract

Aim: The action of irrigant solutions on intra- radicular dentinal surface were evaluated in an in vitro setting using a scanning electron microscope (SEM) and it was observed that sodium hypochlorite and MTAD produced the cleanest surface and that none of the irrigants were able to produce an ideal preparation of the dentinal surface when used individually. The primary objective of endodontic therapy is to achieve a clean, optimal environment in root canals to avoid unsuccessful treatment outcomes. The complexities of the root canal system necessitate the use of irrigating solutions which act on radicular dentin surface, modifying it. The action of irrigants can be beneficial, and yet at the same time, as they modify the surface structure of dentin, they can have an adverse impact on the properties of dentin. The present study was undertaken to assess the effect of various irrigants on the dentinal surface using an SEM. Materials and Methods: Forty-five roots were randomly divided into nine groups (n=5) and prepared by sectioning at the level of cemento-enamel junction (CEJ) and 10 mm from the CEJ and split longitudinally. The dentin surface was prepared and the cemental surfaces were coated with double layer of varnish. The irrigants tested were normal saline, de-ionized water, 17% ethylenediaminetetraacetic acid (EDTA), 5% sodium hypochlorite (NaOCl), 5% NaOCl with ultrasonic agitation, 3% hydrogen peroxide, 2% chlorhexidine (CHX), MTAD, and MTAD with ultrasonic agitation. The prepared samples were placed in the irrigant solution for 3 min, subsequently dehydrated, sputter coated, and observed under SEM. The images were subsequently analyzed for dentinal surface changes. Results: 17% EDTA and MTAD produced the cleanest dentinal surface. Ultrasonic agitation enhanced the effect of irrigants. 5% NaOCl and 3% hydrogen peroxide were efficient at removal of organic debris, but were unable to remove the smear layer. De-ionized water, normal saline, and 2% chlorhexidine were not effective at removing the debris or the smear layer. Conclusion: None of the irrigants individually were able to achieve conditions of an ideal dentinal surface preparation.



How to cite this article:
Karunakaran J V, Kumar S S, Kumar M, Chandrasekhar S, Namitha D. The effects of various irrigating solutions on intra-radicular dentinal surface: An SEM analysis.J Pharm Bioall Sci 2012;4:125-130


How to cite this URL:
Karunakaran J V, Kumar S S, Kumar M, Chandrasekhar S, Namitha D. The effects of various irrigating solutions on intra-radicular dentinal surface: An SEM analysis. J Pharm Bioall Sci [serial online] 2012 [cited 2021 Oct 24 ];4:125-130
Available from: https://www.jpbsonline.org/text.asp?2012/4/6/125/100209


Full Text

The primary objective of endodontic treatment is to achieve a clean environment in the root canal to minimize any risk which leads to unsuccessful treatment outcomes. [1],[2] Because of the anatomical complexity of the root canal system, irrigants are used to supplement mechanical preparation of canals. [2] Mechanical instrumentation usually results in an amorphous irregular smear layer covering the radicular dentinal surfaces and plugging the dentinal tubules. [3],[4] The most frequently used irrigants are sodium hypochlorite (NaOCl) and hydrogen peroxide (H 2 O 2 ), or the combined use of both. [4],[5] Their benefits, good tissue dissolving and disinfecting capability, have been demonstrated in several investigations. [4],[6],[7] Studies of the interaction mechanisms of sodium hypochlorite and hydrogen peroxide have suggested that they can be toxic and irritant to the periapical tissues. [4] An ideal irrigation solution should be capable of penetrating and disinfecting the entire root canal system by dissolving both organic components (necrotic and non-necrotic pulpal tissue, predentin, and microorganisms) and inorganic components (mineral content of the dentinal tubules) of the smear layer. [8],[9] In addition, an ideal irrigant should mechanically flush any loose debris, lubricate canals during biomechanical preparation, and have low tissue toxicity. [10],[11]

Ethylenediaminetetraacetic acid (EDTA) was introduced to endodontics as a tool for negotiating narrow or sclerosed canals, where demineralization of root dentine on application of 15% EDTA was proportional to the observation time. [12],[13] However, the demineralizing effect of the chelating agent within the canal is self-limiting because it is exhausted during the chelation process. [14],[15]

Endodontic treatment procedures alter the biological, mechanical, and chemical properties of the radicular dentine. The changes in mechanical properties of dentine as a result of root canal irrigants are almost certainly because of the altered chemical composition of radicular dentinal surface. [11],[16],[17] These changes may have a profound effect on the long-term integrity of the tooth. [18] The role of the irrigant is important as it plays a vital role in the ideal preparation of the dentinal surface for bonding. [19],[20]

The use of some disinfectant solutions or medications during root canal preparation may have an adverse effect on the bond strength of posts to root canal dentin. The early bond strengths of resin cements to dentin were adversely influenced by chemical irrigants used during the endodontic treatment procedure. [21]

Chlorhexidine gluconate (CHX) has been suggested as an alternative irrigating solution that could replace NaOCl. CHX is bactericidal because of its ability to precipitate and coagulate bacterial intracellular constituents. [22] Furthermore, its antibacterial action persists in root canal for 12 weeks after its use as an endodontic irrigant. [22],[23],[24] Recently, another endodontic irrigant containing 3% doxycycline hyclate, 4.25% citric acid, and 0.5% polysorbate 80 detergent has been introduced (MTAD). [25],[26]

 Materials and Methods



Seventy extracted human permanent, single-rooted maxillary incisors, maxillary canines, and mandibular first premolars were collected immediately after extraction, debrided, cleaned, and stored in 1% thymol solution. Teeth devoid of caries, restorations, and endodontic treatment were separated. They were then observed for cracks and such teeth were excluded. Teeth with mature and intact root apices were selected for the purpose of the study. The selected teeth were then analyzed using digital radiography to ensure that they had a single patent canal and the root lengths were a minimum of 15 mm [measured from the tip of the root to the cemento-enamel junction (CEJ)]. The selected teeth were then stored in distilled water at 4°C until use. A total of 45 teeth were selected for the purpose of the study.

The selected teeth were then sectioned with a diamond disk under water spray at the level of the CEJ and 10 mm from the CEJ and standardized. They were further split longitudinally in a bucco-lingual plane into two halves with a chisel after grooving, taking sufficient care not to damage the dentin. The surface of the dentin was prepared to remove the surface debris, pulpal remnants, etc. The cemental surface was then coated with a double layer of varnish. The samples were then randomly divided into nine experimental groups (n=5) [Table 1]. The samples of each group were then placed in a bath of the respective irrigant solution for 3 min. After the completion of 3 min, they were rinsed with distilled water to remove the remaining irrigant from the dentinal surface.{Table 1}

The teeth were then placed in a 10% neutral buffered formalin solution at 18°C for 24 h. They were then post-fixed in osmium tetroxide (1% w/v) for 2 h before being dehydrated in graded solutions of isopropyl alcohol (SV Drugs and chemicals, Faridabad, India) and stored in sterile pouches with coding. Each group was processed and stored separately. The coded samples of each group were mounted onto aluminum stubs with carbon tape (Royal tapes Pvt. Ltd., Chennai, India) with the entire root canal visible and facing upward. Each of the specimens was coated with a 20-30 nm thin layer of gold in a gold sputter coating machine (Hitachi, Tokyo Japan). The samples were then examined using a scanning electron microscope (SEM; Hitachi, Japan). The SEM photomicrographs were obtained at ×2000 magnification using digital image analysis software and stored appropriately for subsequent analysis. The most representative micrographs were taken for each millimeter of the specimen.

The photomicrographs were analyzed after coding based on the representative groups in a blind manner by two independent investigators for the effect of the irrigant on the dentinal surface and observations recorded.

 Results



On the analysis of the SEM photomicrographs, the following results for the various groups were observed.

In groups I and II, where the samples were exposed to normal saline and de-ionized water, respectively, the dentin surface was covered by heavy coherent deposits of smear layer and debris with irregular shapes and sizes and the dentinal tubules were not visible [Figure 1], [Figure 2] and [Figure 3].{Figure 1}{Figure 2}{Figure 3}

In group III, where the samples were exposed to 17% EDTA, it produced a fairly clean dentin surface with the dentinal tubules open [Figure 4] and erosion was observed in some areas [Figure 5].{Figure 4}{Figure 5}

In group IV, where the samples were exposed to 3% H 2 O 2 , it resulted in effective removal of surface debris, but the smear layer remained and the dentinal tubules were not visible [Figure 6].{Figure 6}

In group V, where the samples were exposed to 5% NaOCl, the dentin surface was totally free of debris, and dentinal tubules were not visible and were covered by smear layer [Figure 7].{Figure 7}

In group VI, where the samples were exposed to 5% NaOCl with ultrasonic agitation, the effect of 5% NaOCl on dentinal surface was enhanced by the use of the agitation technique and some of the dentinal tubules partially opened with some removal of the smear layer and the dentinal plugs remained [Figure 8].{Figure 8}

In group VII, where the samples were exposed to 2% CHX, the dentin surface was covered by smear layer and debris with irregular shapes and sizes and the dentinal tubules were not visible [Figure 9].{Figure 8}

In group VIII, the samples when exposed to MTAD, the smear layer was partially removed and the dentinal tubules were visible and dentinal plugs were seen [Figure 10].{Figure 10}

In group IX, where the samples were exposed to MTAD with ultrasonic agitation, the effect of MTAD on dentinal surface was enhanced by the use of the agitation technique and all the dentinal tubules were seen with removal of most of the smear layer and some dentinal plugs were seen [Figure 11].{Figure 11}

Overall, groups III (17% EDTA) and IX (MTAD) presented the cleanest dentinal surface and most of the tubules were open though dentinal plugs were seen. Use of ultrasonic agitation seemed to increase the efficacy of 5% NaOCl and MTAD. Groups I (normal saline) and II (de-ionized water) had the least effect on the dentinal surface with lots of debris and smear layer seen [Table 2].{Table 2}

 Discussion



The complexity of the root canal system and the patterns of prevalence of types of systems in different teeth and roots have been well documented. Before the effects of irrigant protocols on root canal surfaces can be evaluated, the condition of the presenting dentinal surfaces must be appreciated. [20],[27] As root canal therapy may be done in young or old, teeth which are vital or non-vital, with or without apical periodontitis, a diverse range of conditions may present in the canal, which affect the surface dentinal structure. A regular dentine surface with patent dentinal tubules is therefore often taken to mean a clean dentine surface. Teeth subjected to various microbial insults (through caries, tooth surface loss, periodontal disease) or restorative stimuli may demonstrate various degrees of dystrophic calcification. [18],[28]

The root canal dentine surface presents with an unmineralized front with a hardness value that is lowest for dentine (30 kg/ mm 2 ). In some areas of the root canal dentin, particularly in older teeth, the higher levels of mineralization may raise hardness to 60-70 kg/mm 2 . [17] The dentinal surface is porous owing to the patency of dentinal tubules, although they may sometimes be sclerosed. The presence, density, and diameter of the dentinal tubules vary with the corono-apical site in the tooth as well as with age and insult. [20],[27] Where present, the dentinal tubules are irregular in density and direction in the apical region of roots.

Biomechanical preparation of the root canal produces a layer of organic and inorganic material that also contains microorganisms and their byproducts. Much of the material is made up of small particles of mineralized collagen matrix and is spread over the entire surface of the cut dentinal surface to form what is called as the smear layer. At an ultrastructural level, debris is evident as irregular, disorganized sludge-like material covering and masking the openings of dentinal tubules and any depressions in the canal wall. [21],[29]

The presence of the smear layer has been postulated to be an avenue for leakage and a source of substrate for bacterial growth and ingress. When canals were obturated, the frequency of bacterial penetration in the presence of the smear layer was shown to be significantly higher than with smear layer removal. [20],[27],[30] Also, the smear layer may interfere with the penetration of gutta-percha into the tubules and the adhesion and penetration of root canal sealers into dentinal tubules, leading to microleakage. [28],[31] Irrigating solutions were used for the removal of tissue debris and microorganisms and prevent formation of dentine mud that can block the root canal, produced during instrumentation. They also remove smear layer and increase cutting efficiency by decreasing the chance for fracture of the instruments. An ideal root canal irrigant should be biologically compatible, chemically able to remove both organic and inorganic substrates, be antibacterial, demonstrate good surface wetting, have no adverse effects on remaining tooth structure, and be easy to use and effective within clinical parameters. No single agent appears to meet all of these criteria. [18]

A number of irrigants have been introduced over the years with specific actions of chelation, dissolution capacity, antibacterial action, and substantivity, and more recent formulations include combinations of detergent, acid, and antibiotic, and also focus on reducing the surface tension to achieve better penetration into the tubules. [16],[32],[33]

In the present study, normal saline and de-ionized water (groups I and II) did not significantly alter the dentinal surface and could be used for their flushing and lubricant action. 17% EDTA (group III) was most efficient at cleaning the dentinal surface, and in some areas, erosion was observed with loss of intertubular and peritubular dentin. MTAD, when used alone, did not remove the entire smear layer, but with ultrasonic agitation produced a clean dentinal surface free of smear layer though dentinal plugs could be observed in some areas. 5% NaOCl (group V) and 3% H 2 O 2 (group IV) were efficient at removal of debris, but did not remove the smear layer. 2% CHX was not efficient at smear and debris removal and can be used for its antimicrobial action and substantivity. In order to achieve an ideal dentinal surface preparation, irrigants can be used in sequence with importance given to the irrigation volume, exposure time, and mode of delivery.

During biomechanical preparation, the proportion of root canal dentine surface planed by instruments has been quantified recently using high-resolution computed tomography and it was found that 35-53% of the root canal surface remained uninstrumented. [7],[34] In addition to its flushing action, the principal role of the irrigant solution is debridement of the uninstrumented canal walls. This can be achieved by an irrigant capable of dissolving organic tissue and using a method suitable for its delivery to the uninstrumented surfaces.

Evaluating the effect of irrigants on the mechanical properties of dentine is of utmost importance as the understanding of the mechanical properties of dentine is the first step toward predicting the behavior of the dentine-restoration interface. The changes in mechanical properties of dentine as a result of root canal irrigants and dressings are almost certainly because of the alteration of chemical and structural composition of radicular dentinal surface, thereby changing its permeability and solubility characteristics, and hence affecting the adhesion of materials to dentin surfaces. [24],[35] Optimum adhesion requires intimate contact between the adhesive material and the substrate to facilitate molecular attraction and allow either chemical adhesion or penetration for micromechanical surface interlocking. Adhesion is an important property which helps the root canal sealers effectively seal the canal and prevent microleakage at the dentin-sealer interface and the interface with the obturating material. Recently, adhesive technology has been introduced to the field of endodontics, with a specific focus on achieving a monobloc in which the core material, sealer, and the root canal dentin form a single cohesive unit. The role of the irrigant is important as it plays a vital role in the ideal preparation of the dentinal surface for bonding. [33] The use of some disinfectant solutions or medications during root canal preparation may have an adverse effect on the bond strength of posts to root canal dentin. The search is on for the one ideal irrigant solution which can satisfy all the criteria for an ideal irrigant solution and further studies in a clinical setting are recommended.

 Conclusion



Within the limitations of this study, it could be concluded that root canal irrigants definitely alter the surface characteristics of dentin and none of the irrigants were able to achieve a totally clean dentinal surface. Ultrasonic activation of the irrigant improved the irrigant action on the dentinal surface. The pattern of alteration of the dentinal surface is different for each irrigant solution and these surface alterations may have a negative or positive impact on bonding characteristics of radicular dentinal surface.

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