Effect of Methods of Irrigation and Different Irrigant Combination on Root Canal Debris Removal in Curved and Straight Canal – An in Vitro Study.

INTRODUCTION

Successful endodontic therapy involves a series of procedures that begins with adequate knowledge of the biology of the pulp and periapical tissues, and ends with the subsequent evaluation of the treatment rendered. Cleaning and shaping of the root canal is one of the most important and demanding aspect of this treatment. Debridement of the root canal system is essential for endodontic success, with irrigation being a vital part of root canal debridement. According to Cohen “what is taken out of the root canal may be more important than what is put into the canal”. Ideally, root canal irrigants should flush out debris, dissolve organic tissue, kill microbes, destroy microbial byproducts An Excerpt from the Dissertation submitted to Pt. B.D. Sharma University of Health Sciences, Rohtak, Year- 2009

and remove smear layer. The purpose of irrigation is twofold: to remove gross debris originating from pulp tissue; possible bacteria; the organic component and to remove smear layer; consisting mainly of the inorganic component.Heredia et al stated that the most widely used irrigant for root canal treatment is sodium hypochlorite (NaOCl) at concentration of 0.5% to 5.25%. The tissue dissolving capacity and microbial activity of NaOCl makes it an excellent irrigating solution, but it has only limited effect on the dissolution of smear layer. Acid solutions have been recommended for removing the smear layer including sodium salt of ethylenediaminetetracetic acid (EDTA) which is most active at a concentration of 15 to 17% and pH of 7 to 8.Furthermore, after instrumentation, a smear layer is formed that is a surface film of 1-2μm thickness that remains adherent to the root canal wall. This smear layer consists of dentin particles, pulp tissue, bacterial components, as well as retained irrigants and it occludes the dentinal tubular openings. Al Hadlaq M et al reported that the chemo mechanical action of sodium hypochlorite removes loosely attached debris or organic material; whereas chelating agents are required to remove the smear layer. Barkhordar et al reported that the usefulness of tetracycline is attributed to its antibacterial activity and its recently discovered ability to inhibit mammalian collagenases. Haznedaroglu F et al showed that tetracycline hydrochloride (HCl), an acidic solution with bacteriostatic properties, has been considered to be suitable for endodontic irrigation’. According to Ingle irrigation delivery system is also one of the important part for action of root canal irrigants. Irrigation is commonly applied by a syringe and a needle’. A Recently introduced irrigation needle (Navi Tip Fx Ultradent) which is covered with brush is used in this study. Gunday et al stated that in addition to the canal instruments and preparation techniques used, root canal morphology and degree of curvature are also the determining factors during the root canal preparation’. In curved canal the deformation of canal instruments places stress on the instrument, with tensile stresses exerted on the noncurved parts and compressive stresses from the curved parts of the canal instruments. When the curvature of canal increases distorted part of the file becomes greater and the risk of breakage increases. The aim of this in vitro study is to evaluate the debris removal efficacy of combination 5% NaOCI + 17% EDTA and 5% NaOCl + 1% tetracycline hydrochloride irrigants when they were used in conjunction with plain and Navi Tip Ex Needle in straight and curved canals. As the type of irrigants, the irrigation delivery system and canal curvature are the determining factors for the root canal cleanliness, this study has been undertaken to assess which of these factors are crucial for success of the root canal treatment.

Methodology

In this in vitro study total hundred single rooted (50 straight and 50 curved) noncarious, extracted, human teeth were collected. Exterior surface of all teeth were thoroughly cleaned of organic debris and calculus with ultrasonic scaler. Among the curved root the canal curvature was selected between 10-20 degree. Canal curvature was measured as described by Schneider (1971) from preoperative radiograph with the help of RVG (GENDEX, DENTSPLY). The teeth were stored in saline till use.

All the teeth were sectioned at cementoenamel junction with diamond disc in presence of water. Patency of the canal was checked by inserting a size 10 K-file (Mani) into the canal so that the tip of the file was just visible through the apical foramen. Individual working length was calculated 0.5mm short from this position. Samples were randomly divided into 10 groups, (8 experimental and 2 control groups) in this study. Number of samples were kept 10 in each experimental and control groups. All the Samples in experimental group were prepared with K file (up to #40) by step back technique as described by Grossman using different irrigants.

Experimental samples were divided into following 8 groups on the basis of irrigating solutions, canal curvature and method of irrigation procedure.

> Group IA: Samples with straight canals were irrigated with plain needle using 1 ml of 5% NaOCI followed by 1 ml of 17% EDTA solution alternatively throughout the preparation.

> Group IIA: Samples with straight canals were irrigated with Navi Tip FX using 1 ml of 5% NaOCl fellowed by 1 ml of 17% EDTA solution alternatively throughout the preparation.

> Group IIIA: Samples with straight canals were irrigated with plain needle using 1 ml of 5% NaOCl followed by 1 ml of 1%. tetracycline hydrochloride solution alternatively throughout the preparation.

> Group IVA: Samples with straight canals were irrigated with Navi Tip FX using 1 ml of 5% NaOCl followed by 1 ml of 1% tetracycline hydrochloride solution alternatively throughout the preparation.

> Group IB: Samples with curved canals were irrigated with plain needle using 1 ml of 5% NaOCl followed by 1 ml of 17% EDTA solution alternatively throughout the preparation.

> Group IIB-Samples with curved canals were irrigated with Navi Tip FX using 1 ml of 5% NaOCI followed by 1 ml of 17% EDTA solution alternatively throughout the preparation.

> Group IIIB-Samples with curved canals were irrigated with plain needle using 1 ml of 5% NaOCI followed by 1 ml of 1% tetracycline hydrochloride solution alternatively throughout the preparation.

> Group IVB: Samples with curved canals were irrigated with Navi Tip FX using 1 ml of 5% NaOCl followed by 1 ml of 1% tetracycline hydrochloride solution alternatively throughout the preparation.

In control groups no irrigation and instrumentation was performed.

> Group VA Samples with straight canals which were not instrumented.

> Group VB Samples with curved canals which were not instrumented.

During the cleaning and shaping each sample was irrigated with 1 ml of irrigant after each change of instrument. Distilled water was used in between two irrigation as well for final rinse to neutralize the effect of these irrigants. Vertical grooves along the long axis of Samples were made on all the samples with the help of diamond disc in presence of moisture. Then all the samples were split into two halves using chisel and mallet. The split samples were prepared for SEM analysis.

Canal cleanliness evaluation

Root canal debris is defined as dentine chips, pulpal remnants and particles loosely attached to the canal wall. Scoring, of debris was performed at 500x magnification

Scoring system for debris as given by Peters OA et al

> Score 1: Clean root canal wall, only few small debris particles.

> Score2: Few small agglomerations of debris covering less than 25% of canal wall area.

> Score 3: Many agglomerations of debris covering 25% to 50% of root canal wall area.

> Score 4: 50% to 75% of the root canal wall area covered by debris.

> Score 5: More than 75% of root canal wall area covered by debris.

Statistical analysis used- Mean, Mann- Whitney U test, Chi-square test. Statistical software used statistical package for social sciences (SPSS). version 12.0.

Significance at different levels among all groups for debris removal analyzed by chi-square

test.

Mann-Whitney U test-it is a nonparametric test for assessing whether two independent samples of observations come from the same distribution.

Statistical comparison for straight vs curved canals, plain vs Navi Tip FX and irrigating solutions (5% NaOCl + 17% EDTA vs 5% NaOCl +1% tetracycline hydrochloride) by Mann-Whitney test.

Results and observations

After preparation all samples were viewed under SEM and photomicrographs were taken at 500X. Scoring was done for all samples according to scoring system given by Peters OA et al. All samples were evaluated and scored at cervical, middle and apical level.

Table – 1

Comparative evaluation of mean debris score of different goups at different levels

Table -2

Showing mean, SD and p Values at different levels of tooth

DISCUSSION

The primary function of an endodontic irrigant is to remove debris loosened but not removed by instrumentation. Moreover, some irrigants have property to remove the smear layer. Hulsmann et al found that the smear layer consist of inorganic and organic substances including fragments of odontoblastic processes, micro-organisms and necrotic material”. It is made up of a superficial layer on the canal walls approximately 1-2pm thick and a deeper layer packed into the dentinal tubules up to 40μm. Degree of smear layer removal depends upon the type of irrigants used. In this study the mean debris score for control and experimental group were 15.0 and 8.65 respectively. The uninstrumented canals showed walls completely covered with tissue confirming the finding of Heard F et al that specimen preparation alone did not remove tissue from canal walls”. The mean debris score for straight and curved canals were 2.82 and 2.95 respectively. While at cervical, middle and apical level the mean debris scores were 2.2, 2.25, 3.9 for straight canals and 2.0, 2.75, 4.10 for curved canals. These results are similar as obtained by Ciucchi et al, Garberoglio et al, and Teixeira et al 121314. This may be attributed to the fact that as reported by Ciucchi et al, limited distribution of the irrigants is because of limited size and pronounced curvature of the canal which are obstacles to the optimal apical flooding of irrigants”. Moreover Garberoglio et al stated that a major challenge in

clinical endodontics is the preparation of apical region of the root canal”. The access is often difficult because of its anatomy resulting in reducing effects of the irrigants at the level of 1 to 3mm from the apex. In these areas irrigants are not effective in cleaning the root canal system and use of powerful irrigating agent is contraindicated because of the risk of injury to periradicular tissues In this study the mean debris score for samples irrigated with 5% NaOCl + 17% EDTA group was 2.63 while for samples irrigated with 5% NaOCl + 1% tetracycline hydrochloride it was 3.13. Mann Whitney test showed that there was significant difference for debris removal in between the two irrigating solution group (p = .001). Barkhordar et al reported that irrigation of teeth with aqueous solutions of doxycycline HCl eliminated smear layer in concentration dependent manner. Sen et al reported that the removal of smear layer as well as soft tissue and debris can be expedited by the alternate use of EDTA and NaOC15. According to them 5.25% NaOCl and 17% EDTA concentration is most effective concentration in removing debris from root canal walls. In this study mean debris score for the samples in which plain needle used was 3.02 and for Navi Tip Fx, it was 2.75. It showed that Navi Tip FX is more efficient in debris removal .Mann Whitney analysis showed that difference of debris removal was statistically significant between both Needle groups (p=0.04). As suggested by Al Hadlaq et al that Navi Tip Fx (ultradent) which is a brush covered needle would produce cleaner coronal one third of instrumented root canal walls of single rooted teeth compared to brushless (Plain needle)”. However, the efficacy of the Navi Tip Fx in teeth with more complex root system such as mesial roots of upper and lower first molar has to be evaluated. More research is needed for the quest of irrigating solution and the irrigation delivery system that can fulfill the requirements of ideal irrigation system for increased success of root canal treatment.

CONCLUSION

Results of the study showed that:

> Total debris removal was better in straight canals compared with curved canals.

> Debris removal was less from apical one third in both straight and curved canals due to limited distribution of irrigants.

> Navi Tip Fx is better in debris removal compared with plain needle but efficacy of Navi Tip Fx is reduced in apical one third of canals in both straight and curved canals,

> 5% Sodium hypochlorite + 17% EDTA irrigants combination is more efficient in total debris removal compared with 5% sodium hypochlorite+1% tetracycline hydrochloride.

Within limitation of this in vitro study, it can be concluded that 5% Sodium hypochlorite + 17% EDTA irrigant combination was more efficient in total debris removal compared to 5% sodium hypochlorite +1% tetracycline hydrochloride. Moreover Navi Tip Fx was more efficient in debris removal from root canal than plain needle, however further research is needed on the use of Navi Tip Fx before its routine use in Endodontic practice.

BIBLIOGRAPHY

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Address for Correspondence

Dr. Medhavi Sharma House No. 494, Surya Nagar,

Gopalpura Bypass, Jaipur – 302015

E-mail: drmedhavisharma@gmail.com