Comparative Study of Cleaning Efficacy of Different Concentrations of Sodium Hypochlorite on Nickel-Titanium Endodontic Instruments.

 

Kaviena Baskaran¹, Dr. James D. Raj², Dr. Joshua Ng Chor Yang³*

¹CRI, Saveetha Dental College and Hospitals, Chennai, India

²Senior Lecturer, M.D.S, Department of Conservative Dentistry and Endodontics, Saveetha Dental College and Hospitals, Chennai, India

³BDS, Saveetha Dental College and Hospitals, Chennai, India

 

ABSTRACT:

Objective: The objective of this study was to develop an effective cleaning procedure for Nickel-Titanium instruments. Materials and method: Twelve newly sterilized Nickel-Titanium(Ni-Ti) instruments were contaminated by preparing canals of extracted teeth and subjected to both mechanical and chemical cleaning procedures under various concentration of sodium hypochlorite.  Debris on flutes was scored after staining with Van Gieson’s solution at X20 magnification using a stereomicroscope. Results: This study showed that a sequential cleaning procedure including combined mechanical and chemical removal with 12% Sodium Hypochlorite (NaOCl) solution is an effective procedure of removing debris from Nickel Titanium hand instruments. Conclusion: The result of this study has shown that a sequential cleaning procedure including combined mechanical and chemical removal with 12% Sodium Hypochlorite solution is an effective procedure of removing debris from Ni-Ti instruments.

 

 

 

INTRODUCTION:

Dental caries with their bacteria and harmful products, mechanical, thermal and electrical injuries, traumatic injuries, and leakage from restorative fillings are some of the many possible irritants of the pulp.  When these irritants fail to be eradicated, an inflammatory response occurs and exacerbates until the condition of the pulp becomes irreversible. At such a state, there would invariably be necrosis of the pulp. The treatment at this stage requires the pulp space which consists of the pulp chamber and the pulp canal to be shaped, cleaned and disinfected. The primary objective of a root canal therapy is the complete eradication of any substance which may cause or act as nidi for infection.

 

This includes necrotic pulpal tissues, calcifications, dentin chips, biofilms, toxins, and microorganisms including bacteria, yeasts, and viruses. If the pathogens persist and remain at the time of obturation, we can expect a high chance of endodontic treatment failure [1]. The preparations of the root canals are divided into chemical and mechanical preparations. Studies have even shown that dentinal tubules are infected with bacteria approximately half the distance between the root canal walls and the cementum dentinal junction[2]. Hence, the mechanical preparation of the canal and chemical disinfection goes hand in hand. With all the emphasis on cleaning and disinfecting, it is clear that asepsis is an important factor in an endodontic treatment. Apart from cleaning and flushing out microbes from the canal, we should also be careful not to introduce microbes and infections into canals through our instruments. The instrument that is always introduced into the canals are our shaping instruments.  Recent advances have led to the introduction of nickel titanium (Nit-Ti) instruments in the dental practice. The alluring advantage of Ni-Ti alloy is its ability to retain its flexibility with increased taper hence making it easy to negotiate canals with curvature. Ni-Ti endodontic instruments can also be used multiple times without intracanal failure [3]. However, the designs of flutes in Ni-Ti files are such that they tend to accumulate debris between the flutes in areas which are relatively inaccessible or cleaning [4]. Because these files can be reused, a proper disinfection protocol is mandatory to prevent any cross infection. The transfer of any debri through instruments from a patient to another is unwanted as they present as antigens, infecting agents or non-specific irritants. There are several studies that have been done regarding disinfection of Ni-Ti endodontic instruments. Chair side cleaning by wiping with gauze was recommended by Segall et al but was proven to be not effective [5]. Murgel et al used various mechanical cleaning methods including using a alcohol soaked gauze, alcohol soaked sponge and an ultrasonic bath which all proved to be not effective as well [6]. Eggert et al and Marending et al also showed that the ultrasonic bath was ineffective in disinfecting Ni-Ti endodontic files [7,8] The purpose of this study is to develop an effective cleaning procedure for Ni-Ti hand instruments and evaluate the effectiveness of the cleaning efficiency of different concentrations of sodium hypochlorite on Ni-Ti endodontic instruments.

 

MATERIALS AND METHODS:

1.   Hand ProTaper (Dentsply Maillefer)

2.   0.2% Chlorhexidine Gluconate solution

3.   3% Sodium Hypochlorite (Prime Dental Products Pvt Ltd)

4.   5% Sodium Hypochlorite (Prime Dental Products Pvt Ltd)

5.   12% Sodium Hypochlorite (Jentex Alkalis, Chennai)

6.   Nylon bristle brush

7.   Van- Giesons stain

8.   Distilled water

9.   Stereomicroscope (Leica microsystems, Switzerland)

 

12 new Ni-Ti instruments were used to instrument the canals of freshly extracted premolar teeth. Visual debris was noted and the instruments were inserted into a sponge soaked in 0.2% chlorhexidine gluconate solution for 30 minutes. The instruments were then randomly divided into three groups of 4 instruments (4 ProTaper) each and subjected to different cleaning procedures as follows:

 

Group 1:

Instruments were placed in an instrument stand and the flutes were brushed with a nylon bristle brush for 20 strokes per row under running distilled water for 5 minutes. They were then were placed in a graduated beaker containing 3% Sodium Hypochlorite solution for 10 minutes and rinsed under running distilled water for 5 minutes.

 

Group 2:

Instruments were placed in an instrument stand and the flutes were brushed with a nylon bristle brush for 20 strokes per row under running distilled water for 5 minutes. They were then placed in a graduated beaker containing 5% Sodium Hypochlorite solution for 10 minutes and rinsed under running distilled water for 5 minutes.

 

Group 3:

Instruments were placed in an instrument stand and the flutes were brushed with a nylon bristle brush for 20 strokes per row under running distilled water for 5 minutes. They were then placed in a graduated beaker containing 12% Sodium Hypochlorite solution for 10 minutes and rinsed under running distilled water for 5 minutes. After the cleaning procedure was done, the instruments were air-dried by placing in the instrument stand, followed by immersion in Van-¬Gieson's stain for 3 minutes. Then the Ni-Ti instruments were rinsed under running distilled water and air dried by placing it in the instrument stand. A Stereomicroscope at 20 X was used to examine the instruments for debris at 3 levels

•     Apical

•     Middle

•     Coronal

 

Instruments were examined by mounting on an acrylic block. The debris on the flutes of the instruments were classified its

•     Stained debris

•     Unstained debris

•     Thin film

 

The Scoring Criteria for debris depending on the extent of stained debris was followed as described by Linsuwanont et al, (2004)[9]:

0 – none

1 – film only

2 – scattered particles spaced widely apart on the flute surfaces (slight)

3 – numerous  particles with areas of continuous coverage on the flute surfaces (moderate)

4 - areas where the flutes are packed with debris to their entire depth (heavy)

 

Only one category of debris was assigned to each site examined. Stained debris ranked ahead of the organic film. The organic film ranked ahead of the unstained debris.

 

 

RESULTS:

Table 1: Kruskal Wallis test

	Median score	Mean score	Standard Error	H value
Group 1 (3% NaOCl)	3	2.8	0.430	58.53
Group 2 (5% NaOCl)	2	2.5	0.121	71.95
Group 3 (12% NaOCl)	1	1.3	0.105	167.65

 

Figure 1: Bar diagram showing percentage of effectiveness of various concentration of sodium hypochlorite on the cleanliness of instruments.

 

The Kruskal-Wallis test was conducted to evaluate the cleaning effectiveness among the 3 groups. According to the results Group 3 (Brushing, 12% Sodium Hypochlorite, Rinsing) showed a statistically significant difference compared to the other test groups (table 1). The effectiveness of the various concentration of sodium hypochlorite on the cleanliness of instruments are 19.6%, 24.1% and 56.2% respectively (figure 1).

 

DISCUSSION:

The design of Ni-Ti files is such that debris accumulates between the flutes which are relatively inaccessible for cleaning. Van Gieson's stain was used in our study; since it is an effective single step staining procedure as it stains the collagen of the organic material. Sodium hypochlorite which has been previously tested for its cleaning effectiveness was included in this study [9]. The different concentrations of sodium hypochlorite used in this study are 3% sodium hypochlorite, 5% sodium hypochlorite and 12% sodium hypochlorite. It has the ability to dissolve organic materials, but its tissue dissolving ability is subjected to its concentration, mechanical agitation and firmly on the ratio of hypochlorite to organic matter [10]. It has also been shown that with I'% Sodium hypochlorite no significant corrosion of Ni-Ti instruments was found even after an immersion time of 60 minutes [11]. Endodontic files are generally cleaned at the end of each appointment or even at the end of the day. The delay in time might decrease the efficacy of debris removal once it has dried. Due to the limitations of our study, the delay factor has not been tested. Following cleaning, endodontic instruments can be sterilized by steam autoclave or dry heat before use and by glass bead or salt sterilizers at the chair side [11]. The result of the study has also shown that the mechanical removal of large quantities of debris by brushing is necessary prior to the use of chemical solutions for better cleaning and disinfection.

 

CONCLUSION:

The result of this study has shown that a sequential cleaning procedure including combined mechanical and chemical removal with 12% Sodium Hypochlorite solution is an effective procedure of removing debris from Ni-Ti instruments. Even this consecutive procedure could not totally remove the organic debris from all the Ni-Ti instruments studied, but it significantly minimizes the biological risk prior to sterilization.

 

REFERENCE:

1.     U. Sjogren, D. Figdor, S. Persson, and G. Sundqvist, “Influence of infection at the time of root filling on the outcome of endodontic treatment of teeth with apical periodontitis,” International Endodontic Journal, 1997;30(5):297–306.

2.     Torabinejad M, Handysides R, Khademi A, Bakland LK. Clinical implications of the smear layer in endodontics: A review. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;94:658-66.

3.     Yared GM, Bou Dagher FE, Machtou p. Cyclic Fatigue of ProFile rotary instruments after clinical use. International Endodontic Journal 2000;33:204-7

4.     Carlos Alberto Ferreira Murgel, Richard. E. Walton, Barry Rittman, Jesus Djalma Pecora. A Comparison of Techniques for cleaning Endodontic Files after usage: A quantitative scanning electron microscopic study. J Endod 1990; 16:214 -7

5.     Segall RO del Rio CE, Brady JM, Ayer WA. Evaluation of debridement techniques for endodontic instruments. Oral Surgery, Oral Medicine and Oral Pathology. 1977;44:786-91

6.     Murgel CAF, Walton RE, Rittmann B, Pecora JD. A comparison of techniques for cleaning endodontic instruments after usage: a quantitative scanning electron microscopic study. Journal of Endodntics. 1990;16:214-7.

7.     Eggert C, Peters O, Barbakow F. Wear of nickel-titanium lightspeed instruments evaluated by scanning electron microscopy. Journal of Endodontics. 1999;25:494-7.

8.     Marending M, Lutz F, Barbakow F. Scanning electron microscope appearences of Light speed instruments used clinically:a pilot study. International Endodontic Journal. 1998;31:57-62

9.     Linsuwanont, P. Parashos, H. H. Messer. Cleaning of Rotary Nickel Titanium Endodontic Instruments.lnt Endod J.2004;37:19-28.

10.  Moorer. W. R, Wesselink. P. R. Factors promoting the tissue dissolving Capability of Sodium Hypochloritc. lnt Endod J.1982; 15:187-196

11.  Svec. A, John. M. Powers. The deterioration of rotary nickel-titanium files under controlled conditions. J Endod 2002; 28:105-107

 

 

 

Received on 18.09.2016          Modified on 19.10.2016

Accepted on 12.11.2016        © RJPT All right reserved