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Effect of irrigation solutions on adhesion of Endorez sealer to root canal dentin.

Dr. Chems Belkhir belkhir_chems@yahoo.fr

Dr. Saida Sahtout

Dr. Latifa Berrezouga Dr. Mohammed Semir Belkhir

Abstract

Introduction: The objective of this work is to study the influence of the different irrigation solution combinations: Sodium hypochlorite (NaO- Cl), EDTA and chlorhexidine (CHX) on the sealing of the root canal obturation using EndorezA sealing cement.

Materials and methods

56 incisors were endodontically prepared with the ProtaperA system and were irrigated with Sodium hypochlorite at 2.5%. These teeth were divided into four groups depending on the final irrigation used. Group 1: 17% EDTA and 2.5% NaOCL, Group 2: 17% EDTA and 0.2% CHX, Group 3: 17% EDTA, 2.5%NaOCI and 0.2% CHX and Group 4: Only 2.5% NaOCI. All the canals were obturated with EndorezA and a gutta percha cone. After coronalobturation with composite resin, infiltration with china ink and diaphanisation, each tooth was ob- served using a stereo microscope and the dye ascent was calculated. Statistical analysis was performed using Post Hoc Test. Results: The irrigation associating EDTA and CHX showed less infiltration than that associating EDTA and NaOCI; (P=0.024). The group irrigated using the association EDTA and CHX gave infiltration rates inferior to those observed in the group irrigated with NaOCI (P=O). The group irrigated using the association EDTA, NaOCI and CHX showed in- filtration rates weaker than the group irrigated with only NaOCL (P=0.04). Non significant dif- ferences were observed between groups 1 and 3 (P=0.68), groups 1 and 4 (P=0.1) and groups 2 and 3 (P=0.06).

Conclusions

The sealing of root canal obturation with EndorezA is sensitive to the last irrigation solution used. The best results were observed in the associations EDTA/CHX and EDTA/NaOCI/CHX. Key words: Endorez, Sodium hypochlorite, EDTA, chlorhexidine, adhesion, root canal dentin

Introduction

The success of root canal therapy depends on the quality of several factors, including the instrumentation, irrigation, disinfection, and 3-dimensional obturation of the root canal.

The ability to bond to radicular dentin has been perceived as beneficial for establishing a durable, impervious seal to prevent colonization of microbial biofilms and reinfection of filled canal spaces There has been a continuous quest throughout the history of endodontics for sealing materials that bond to instrumented canal walls. Resin-based sealers have gained popularity with the recent growing interest in adhesive endodontics. However, several factors make adhesion to the root canal system a chalenge, such as chemical substances used during the biomechanical preparation, volumetric changes that occur in resin-based sealers during polymerization, bonding of the sealer because of polymerization shrinkage stresses, and various geometric factors. The irrigation solutions could alter the physicochemical characteristics of dentin and may have an adverse effect on adhesion to root canal dentin EndorezA (Ultradent Products Inc, South Jordan, UT) is a dualcured radiopaque hydrophilic methacrylate sealer that might be used in the wet environment of the root canal system. EndorezA required removal of canal wall smear layers to facilitate resin tag formation by hydrophilic resins. According to the manufacture, EndorezA can be used either with conventional gutta percha or with specific EndorezA point. In this work, we opted for con- ventional gutta percha as it represents the reference material for canal obturation and it is the most used by the majority of practitioners. The objective of this work was to study the influence of the varioust most used irrigation solution combinations (sodium hypochlorite, EDTA and chlorhexidine) on the sealing of canal obturation using EndorezA.

Materials and Methods

Samples preparation Fifty-six extracted mature human incisors with single straight canals and patent apices were selected. These teeth were stored in KCL at 0.9% until the operative procedures. After performing access cavities, Canals preparation were per- formed by the ProTaper Universal Series Rotary System according to the manufacturer's recommendations using a crown-down technique. Irrigation was performed with sodium hypochlorite at 2.5%7 before and after the passage of each instrument. These teeth were randomly divided into 5 groups, each comprising 14 teeth. Each group underwent a final rinsing according to the following protocol.

After rinsing, the canals were dried with paper points. The obturations were performed with EndorezA (methacrylic resin-based sealing cement) and with one gutta-percha cone according to the protocol recommended by the manufacturer (mono cone obturation). The master-cone (non-standardized medium size VENTURA) of each canal was adjusted with visual and tactile tests. (Control of Tug Back).

A coronal obturation with composite resin (SWISS TECA) was performed in order to obtain a maximal airtight and to avoid any infiltration risk of the dye through the coronal cavity. Infiltration (leakage) with china ink:

All the teeth were immersed in china ink. Each tooth was placed, apex downward, in a Pyrex test tube half-filled with china ink. Each test tube was placed in a water bath, all placed in an agitator for 10 minutes. The water bath temperature was maintained at 37AC. After immersion, the teeth were left to dry in the open air for 24h. The dye deposit to the root surface of each tooth was carefully eliminated with the help of a Soflex disc of fine granulometry.

Diaphanisation

The crowns were sectioned and eliminated, maintaining only the roots in order not to rap- idly exhaust the acid solution. Only the roots underwent the diaphanisation stage. The teeth were placed for 12 days in nitric acid at 5% under continuous agitation and room temperature. The acid solution was daily renewed. To carry out progressive and complete dehydration, the roots were placed in growing concentrations of ethanol solutions (75%, 85%, and 95%, pure) for 24 hours each. The teeth were made trans- parent through immersion in methyl salicylate for 24 hours.

Observation with stereo-microscope

The stereo microscope was used to directly evaluate the dye recovery. The different samples of the five groups were photographed with the stereo microscope in two views (sections): ves- tibular and proximal. The measurements of the dye recovery were taken under an enlargement of 0,75, through unity of microscopic scale. The Post Hoc Test was used to conduct a multiple comparison between groups 1, 2, 3 and 4. The value p is considered as significant when it is inferior to 0.05.

Results

Infiltration scores are shown in figure 5. The significant differences were observed between:

- Groups 1 (17% EDTA and 2.5% NaOCL) and 2 (17% EDTA and 0.2% CHX) (P=0.024). The irrigation associating 17% EDTA and 0.2% CHX shows less infiltration than that associating 17% EDTA and 2.5% NaOCL.

- Groups 2 (17% EDTA and 0.2% CHX) and 4 (2.5% NaOCL) (p=0). The group irrigated us- ing the association 17% EDTA and 0.2% CHX shows infiltration values of china ink clearly inferior to those observed at the level of the group irrigated with 2.5% NaOCL.

- Groups 3 (17% EDTA, 2.5% NaOCL and 0.2% CHX) and 4 (2.5% NaOCL) (p=0.04). The group irrigated with the association 17% EDTA, 2.5% NaOCL and 0.2% CHX gives infiltration values weaker than the group irrigated with only 2.5% NaOCL. No significant differences were observed between groups 1 and 3 (P=0.68), groups 1 and 4 (P=0.1) and groups 2 and 3 (P=0.06).

Discussion

The methods used to evaluate the root canal leakage are numerous and the results are often contradictory. Dye penetration study is frequently used as it presents a good correlation with the other techniques.

Many researches on EndorezA cement have been interested in its adhesion to the dentine when comparing it to other sealing cements but few works have studied the effects of the irrigation solutions on the cement bonding. Endodontic irrigation can result in an alteration of the chemical and structural composition of the human dentin modifying its permeability and its solubility, and affecting adhesion of materials to dentin surfaces. According to Xiaoli study, the irrigation solutions act on the physicochemical properties of the dentin surface, mainly on its wetness and durability.

Optimum adhesion requires intimate contact be- tween the adhesive material and the substrate to facilitate molecular attraction and allow either chemical adhesion or penetration for micromechanical surface interlocking. Therefore, adhesion processes are mainly influenced by the relative surface energy (wetting ability) of the solid surface which, in turn, is affected by the internal dentin wetness resulting from dentin permeability provided by water in the dentinal tubules. This wetness is a consequence of dentin permeability provided by water in the dentinal tubules.

In this study, we tested the effect of the various most currently used irrigation solution combinations (NaOCl, EDTA, CHX) on the leakage of EndorezA canal filling. We noticed that the final irrigation with only sodium hypochlorite gave the most significant infiltration values. Sodium hypochlorite is the base irrigation solution that allows canal disinfection and the elimination of the organic fraction from the smear layer. Sodium hypochlorite is a powerful oxidizing agent that allows the formation of an oxygen-enriched layer to the dentinal surface. According to Morris et al. NaOCL leads to the oxidation of certain components of the dentinal matrix.It also leads to the formation of protein free radicals that gets into competition with the vinyl free radicals generated by the photo activation of resin sealer. This leads to an incomplete polymerization that affects the obturation quality.Oxygen is considered among the substances that inhibit the polymerization of resin-based sealers. According to Ari et al. the formation of oxygen bubbles in the resin dentin interface will interfere with resin infiltration at the level of the tubules. Irrigation with sodium hypochlorite also causes a reduction in the calcium and phosphorus rates of dentin surface, thus modifying certain mechanical properties of this tissue, such as elasticity, flexion and micro hardness. This contributes to the decrease of the micro mechanical interaction between the resin sealing cements and the dentin. All these points explain the bad results obtained in this study. The final irrigation associating EDTA and NaOCI did not give better results than the final irrigation with only hypo- chlorite. EDTA removes the mineral fraction from the smear layer exposing the dentinal tubules It is generally used in the final rinsing following the end of shaping.This irrigation sequence allows the total elimination of the smear layer (organic and mineral fractions) but it can be at the origin of certain problems for the exposed root dentin. EDTA can cause severe erosion to the dentin if it exposed for a long time or if EDTA is not neutralized. Calt and Serper suggest that EDTA should be used for less than a minute in the canal to avoid any risk of erosion. Dogan and Semra showed that the irrigation associating NaOCI and EDTA alter the mineral of the root dentin. Several other studies showed that the use of sodium hypochlorite in the final flush after EDTA increases dentinal erosion.NaOCI attack the collegen exposed.Although we had aspired NaOCI before using EDTA and we neutralized the latter with distilled water, the results were not better. This is explained by the oxidizing action of hypochlorite which was lastly used. Eldeniz study which used the final irrigation protocol (EDTA, NaOCl) showed a bad adhesion of EndorezA to the dentin compared to the other sealing cements.According to Doyle study, when EDTA is used in final rinsing following NaOCI, the adhesion of EndorezA to the dentin is not altered by the latter. The final irrigation associating EDTA and CHX showed better results with the weakest infiltration values. The absence of NaOCI ameliorates the quality of the canal fill- ing (or of adhesion).

In our study, we noticed that the neutralization of EDTA with CHX had ameliorated the obturation leakage. Erdemir et al. noticed that CHX significantly increases the adhesion force of the resin sealers to the radicular dentin. This phenomenon could be explained by the adsorption of CHX to the dentin surface which is in favor of resin infiltration at the dentinal tubules.

We noted that there are no significant differences between the irrigation associating EDTA and NaOCI and that associating EDTA, NaOCI and CHX. CHX managed to neutralize the effect of NaOCI. According to Santos et al, CHX used alone does not affect adhesion of the selfetching adhesives to the dentin as it is an anti- oxidizing agent. It is the same when CHX is associated with EDTA.

It is worth noting that a white precipitate is formed when these two products are associated. When CHX is associated with sodium hypochlorite, a brown orange (parachloramine) is formed at the canal surface and it affects the canal obturation with the resin cements. It is for these reasons that we performed rinsing with distilled water before the use of CHX. According to Wachlarowicz, the different irrigation solutions have little effect on the dentinal adhesion of epiphany-based sealers. The adhesion of epiphany to the dentin is comparable to other sealing cements. The negative effect of NaOCl on adhesion was not confirmed by Wachlarowichz study.

Based on this study, the best leakage results were obtained with the following combinations "EDTA and CHX" and "EDTA, NaOCl and CHX". The association EDTA, NaOCI and CHX allows a rigorous final disinfection thanks to the combined action of sodium hypochlorite and CHX without an alteration of Endorez sealer adhesion. This irrigation protocol could be indicated in case of infected canals.

Group 1

- Suction of sodium hypochlorite from the canal.

- Irrigation with 17% EDTA7 for one minute and neutralization with 3cc sodium hypochlo- rite at 2.5% for one minute.

Group 2

- Suction of sodium hypochlorite from the canal.

- Irrigation with 17% EDTA for one minute. - Neutralization with 3cc of distilled water for one minute.

- Final rinsing with 3cc of chlorhexidine at 0.2% for one minute.

Group 3

- Suction of sodium hypochlorite from the canal.

- Irrigation with 17% EDTA for one minute. - Neutralization with 3cc of sodium hypochlorite at 2.5% for one minute.

- Rinsing with distilled water for one minute (in order to avoid the formation of precipitate rust)

- Final rinsing with 3cc of chlorexidine at 0.2% for one minute.

Group 4

- Irrigation with sodium hypochlorite at 2.5% for one minute.

References:

1. HU X, LING J, GAO Y. EFFECTS OF IRRIGATION SOLUTIONS ON DENTIN WETTABILITY AND ROUGHNESS. J ENDOD 2010; 36:1064-67.

2. MAI S, KIM YK, HIRAISHI N , LING J, PASHLEY DH, TAY FR. EVALUATION OF THE TRUE SELF-ETCHING POTENTIAL OF A FOURTH GENERATION SELF-ADHESIVE METHACRYLATE RESIN--BASED SEALER. J ENDOD 2009; 35:870-74.

3. SCHWARTZ RS. ADHESIVE DENTISTRY AND ENDODONTICS. PART 2: BONDING IN THE ROOT CANAL SYSTEM. THE PROMISE AND THE PROBLEMS: A REVIEW. J ENDOD 2006; 32:1125-34.

4. BELLI S, COBANKARA FK, OZCOPUR B, ELIGUZELOGLU E, ESKITASCIOGLU G . AN ALTERNATIVE ADHESIVE STRATEGY TO OPTIMIZE BONDING TO ROOT DENTIN. J ENDOD 2011; 37: 1427-32.

5. ERDEMIR A, ARI H, GE[pounds sterling]NGE[pounds sterling]NES H, BELLI S. EFFECT OF MEDICATIONS FOR ROOT CA- NAL TREATMENT ON BONDING TO ROOT CANAL DENTIN. J ENDOD 2004; 30: 113-16. 6. KIM YK, GRANDINI S, AMES JM, GU LS, KIM SK, PASHLEY DH, GUTMANN JL, TAY FR. CRITICAL REVIEW ON METHACRYLATE RESIN--BASED ROOT CANAL SEALERS.

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