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Effect of endodontic irrigating solutions on the microhardness and roughness of root canal dentin: An in vitro study

Chetan R Patil, Veerendra Uppin

Department of Conservative & Endodontics, K.L.E's. V. K. Institute of Dental Sciences, Belgaum, Karnataka, India

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Date of Submission 01-Nov-2009

Date of Decision 28-Apr-2010

Date of Acceptance 10-Nov-2010

Date of Web Publication 25-Apr-2011

Abstract

Context: To evaluate the effect of widely used endodontic irrigating solutions on root dentin microhardness and surface roughness.

Materials and Methods: One hundred twenty, non-carious extracted human permanent incisor teeth were selected. The crowns of the teeth were sectioned and the roots were separated longitudinally to get 240 specimens. These specimens were then divided into six groups according to the irrigating solutions used. The solutions used were 5% and 2.5% NaOCl solutions, 3% H2 O2 , 17% EDTA solution, 0.2% chlorhexidine gluconate, and distilled water. Then, the specimens were subjected to microhardness and roughness testing. The data were analyzed using ANOVA and Tukey's multiple comparison tests.

Results: The results of this study indicated that all irrigation solutions, except 0.2% chlorhexidine gluconate, decreased the microhardness of root dentin, and 3% H2 O2 and 0.2% chlorhexidine gluconate had no effect on surface roughness.

Conclusions: Within the limitation of this study, it is concluded that 0.2% chlorhexidine gluconate seems to be an appropriate irrigation solution, because of its harmless effect on the microhardness and surface roughness of root canal dentin.

Keywords: Irrigating solutions, microhardness, root dentin, surface roughness

How to cite this article:

Patil CR, Uppin V. Effect of endodontic irrigating solutions on the microhardness and roughness of root canal dentin: An in vitro study. Indian J Dent Res 2011;22:22-7

How to cite this URL:

Patil CR, Uppin V. Effect of endodontic irrigating solutions on the microhardness and roughness of root canal dentin: An in vitro study. Indian J Dent Res [serial online] 2011 [cited 2011 Nov 15];22:22-7. Available from: http://www.ijdr.in/text.asp?2011/22/1/22/79969

Chemomechanical preparation is one of the important factors for successful endodontic treatment. Chemomechanical debridement of root canal system is achieved by the use of instruments and effective irrigating solutions. The aim of instrumentation and irrigating is to prepare a clean, debris-free canal for subsequent obturation. [1]

An instrument thrust into the canal is likely to force noxious materials like necrotic pulp or shreds of mummified tissue with bacteria into it, through the apical foramen, with resulting periradicular pathology. During each instrumentation procedure, the canals are simultaneously washed out or irrigated with a solution capable of disinfecting them and dissolving organic matter. [2]

In addition to the debriding action, irrigation serves the purpose of facilitating instrumentation by lubricating canals and by floating out dentinal filings. [2]

Thus, the goals of irrigation are [2] :

lavage of debris;

tissue dissolution;

antibacterial action; and

lubrication.

Various irrigating solutions have been used, such as: 5% and 2.5% sodium hypochlorite, 3% hydrogen peroxide, 17% EDTA, and 0.2% chlorhexidine.

Among these, one of the most popular irrigating solutions is sodium hypochlorite. [2] An in vitro study has demonstrated that 2.6% NaOCl has excellent predentin and tissue solvent action. [3]

The 3% hydrogen peroxide alone also effectively "bubbles out" and mildly disinfects the canal by release of nascent oxygen. [2]

Investigators at Lomba Linda University found that 5.25% NaOCl was not effective against anaerobic bacteria as 0.2% chlorhexidine gluconate or 3% hydrogen peroxide. [2]

Mechanically prepared dentin surfaces are always covered with a so-called smear layer, a loosely bonded amorphous layer of organic and inorganic debris. In this respect, several endodontic irrigating solutions have been used to remove such smear layer with varying degrees of success. They have ranged from acids and chelates, to those intended to dissolve organic debris. [4]

Irrigation of root canal with 10 ml of 17% EDTA followed by 10 ml of 5% NaOCl has been recommended as an effective method to remove smear layer. [5]

The most common chelating agent used for irrigating includes 17% EDTA solution (pH of 5-9). The authors have shown that optimal time of EDTA is 15 min, after which time no chelating action can expected. [2]

It is important to test the effect of the irrigating solutions on all dentin tissues, as they may come in contact during irrigating procedures. These irrigating solutions cause alterations on dentin and enamel surfaces and affect their interactions with materials used for obturation and coronal restorations. [4]

Studies on modes of action and efficiency of various chemical irrigating solutions have shown their direct effect on both organic and inorganic components of root canal dentin. In turn, the mechanical, chemical, and physical properties of dentin structure changes.

It has been noted that microhardness and roughness are sensitive to composition and surface changes of tooth structures. [6]

A similar correlation can be made between microhardness and roughness of root dentin and irrigating solutions. [4] Thus, it is of interest to investigate to what extent the dentin of the root canal is affected by the use of various irrigating solutions.

Therefore, this study was designed to evaluate the effect of widely used irrigating solutions on the microhardness and roughness of root canal dentin.

Materials and Methods

Sample selection

One hundred and twenty non-carious, non-hypoplastic, extracted human intact permanent maxillary and mandibular incisor teeth from patient with age groups of 35-45 years were selected. The teeth were stored at 37°C in buffered saline.

Specimen preparation

The crowns of the teeth were sectioned at cemento enamel junction (CEJ)using a high-speed diamond point under water-cooling. Then, the roots were separated longitudinally using a diamond disc under water-cooling. Thus, 240 specimens were obtained. These specimens were then examined under stereomicroscope to eliminate the teeth with cracks and other specimens were added to compensate for them.

The specimens were then ground-polished with water-cooled carborandum disc. Final polishing was carried out in felt cloth and buff by using 0.05 μm size aluminium oxide powder mixed with distilled water.

A plastic ring was then taken, and it was poured with a mixture of cold cure resin. And the specimens were embedded on the resin with polished surface facing outside. After curing of the resin, the ring was removed and repolishing of specimens was done to remove the excess material present on the tooth surface [Figure 1]a.

Figure 1: (a) Specimens (b) Specimens immersed in solutions (c) Microhardness tester (d) Microhardness testing of specimens (e) Surface roughness-testing machine (f) Surface roughness testing of specimens

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Grouping

A total of 240 specimens were then divided into six groups, with 40 specimens in each group according to the irrigating solutions used.

Exposed dentin surfaces were immersed in plastic jar containing irrigating solutions [Figure 1]b as follows:

Group 1: 5 ml, 5.0% NaOCl for 15 min

Group 2: 5 ml, 2.5% NaOCl for 15 min

Group 3: 5 ml, 3% Hydrogen peroxide for 15 min

Group 4: 5 ml, 17% EDTA solution for 15 min

Group 5: 5 ml, 0.2% Chlorhexidine gluconate for 15 min

Group 6: 5 ml, Distilled water for 15 min (control).

At the end of active treatment period (15 min), the samples were rinsed with distilled water and dried. Every group was then divided into two subgroups of 20 each.

Group 1a, 2a, 3a, 4a, 5a, 6a were used to determine the microhardness of root dentin. And Group 1b, 2b, 3b, 4b, 5b, and 6b were used to determine the surface roughness of root dentin.

Microhardness testing

The specimens were mounted on stage of Vickers microhardness tester [Figure 1]c. The midroot portion is halfway from the outer surfaces was focused for testing. Indentations were made with Vickers diamond indenter using 300 gm load with a dwell time of 20 s [Figure 1]d. These indentations were measured and converted into Vickers hardness number (VHN) values by the monitor.

Surface roughness testing

The specimens were placed on the flat table surface and the needle of roughness tester was on the mid root region of the tooth surface. The machine was then made to record the surface roughness values of root dentin [Figure 1]d-f. The values were displayed digitally on the screen of the roughness tester. These values were expressed as Ra (μm). The Ra parameter describes the overall roughness of the surface and can be defined as the arithmetical average value of all absolute distances of the roughness profile from the centre line within the

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