Intraorifice sealing ability of different materials in endodontically treated teeth: An in vitro study.

BACKGROUND: Microbial contamination of the pulp space is one of the major factors associated with endodontic failure. Thus, in addition to a three dimentional apical filling a coronal seal for root canal fillings has been recommended. AIM: The present study was conducted to evaluate and compare the intra-orifice sealing ability of three experimental materials after obturation of the root canal system.
MATERIALS AND METHODS: Fourty single rooted mandibular premolars were decoronated, cleaned, shaped and obturated. Gutta-percha was removed to the depth of 3.5 mm from the orifice with a heated plugger. Ten specimens each were sealed with Light Cure Glass Ionomer Cement (LCGIC), Flowable Composite (Tetric N-Flow), and Light Cure Glass Ionomer Cement with Flowable Composite in Sandwich Technique along with a positive control respectively and roots submerged in Rhodamine-B dye in vacuum for one week. Specimens were longitudinally sectioned and leakage measured using a 10X stereomicroscope and graded for depth of leakage.
RESULTS: According to the results of the present study LC GIC + Tetric N Flow demonstrated significantly better seal (P < 0.01) than LC GIC. However there was no statistically significant difference in leakage (P > 0.01) between Tetric N-Flow and LCGIC+Tetric N-Flow groups.
CONCLUSION: In the current study LCGIC+Tetric N-Flow was found to be superior over other experimental materials as intra-orifice barriers.

INTRODUCTION

The outcome of endodontic treatment is influenced by several factors like the preoperative status of the root canal, presence of periapical lesion, previous root canal treatment (RCT), the root filling quality, and coronal restoration.[12]

Microbial infection is one of the major factors associated with endodontic failure. Therefore, every effort should be made to prevent microbial contamination of the pulp space.[3] Thus, the addition of a coronal seal for root canal fillings has been recommended.[4] Lack of coronal seal can be a detrimental factor contaminating the obturated root canal, complicating the treatment outcome. From this perspective, it is important that the intracanal barrier should provide adequate coronal seal and prevent the entry of bacterial toxins into the root canal that compromises the success of the RCT.[5]

Without an adequate coronal seal, long-term success remains questionable and failure to maintain the seal may expose obturated root canals to microbes that could retard healing and create infection in the periradicular, periodontal ligament or supporting osseous structures.[6]

Placement of a suitable material over the coronal gutta-percha to act as a barrier to coronal microleakage would be advantageous in reducing leakage and increasing possibilities for success.

The present study was conducted to evaluate and compare the intraorifice sealing ability of three experimental materials after obturation of the root canal system.

MATERIALS AND METHODS

Forty single rooted mandibular premolars with one canal each, stored at 100% humidity were used for the study. All the teeth were shaped, cleaned, and obturated by the same operator. A # 10 k-file (Dentsply, Maillefer, Ballaigues) was inserted and advanced until it was visualized at the apical foramen. The file was retracted 1 mm and working length was established at this level. A ProTaper SX file (Dentsply/Tulsa Dental Products, Tulsa, OK) was used to flare the orifice. ProTaper S1, S2, F1, and F2 files were used sequentially as per manufacturer's instructions in a crown down technique. 5.25% NaOCl (Vishal Dentocare Pvt Ltd, India) and RC Prep (Medical Products Laboratories INC) were used in between each instrument. Once instrumentation was completed, the canal was rinsed with 2 ml of 17% ethylene diamine tetra acetic acid (EDTA) solution (Henry Schien Inc, USA) and a final rinse of chlorhexidine 0.2% w/v (ICPA Health Products Ltd, India). Canals were dried with sterile paper points. After apical gauging, the samples were obturated with size 25, 6% Taper gutta-percha points (Dentsply, Maillefer, Ballaigues) and AH-plus sealer (Dentsply Detrey of MbH Germany) using cold lateral compaction technique. The samples were randomly divided into four experimental groups of 10 each. Group 1 (control) contained 10 teeth obturated to the level of the orifice. Gutta-percha was removed to a depth of 3.5 mm from the orifice using a # 5 Gates Glidden bur (Mani Inc, Japan) in 30 teeth. This facilitated a uniform orifice diameter of 1.3 mm at its widest point.

LightCure Glass Ionomer Cement (LCGIC; GC corporation, Tokyo, Japan), Tetric N-Flow (Ivoclar Vivadent; flowable composite) and a combination of LCGIC + Tetric N-Flow composite were placed into the orifice as per manufacturer's directions in samples of respective three groups. Teeth of control group were obturated with gutta-percha at the level of the orifice and no intraorifice barrier was placed. Each tooth was placed into a coded container and allowed for sealer and all experimental materials to set. All these samples were kept in humidor for 48 h.

Three layers of nail varnish were placed on all experimental teeth coating their root surface from root apex to the level of the cementoenamel junction. Samples were submerged in a vacuum flask containing rhodamine-B dye, subjected to vacuum pressure of 75 torr for 30 min and allowed to remain in the dye for 7 days.[7]

The experimental samples were then rinsed with running water to remove dye from the external surface. The samples were subsequently longitudinally sectioned with the help of a diamond disc and observed under a stereomicroscope. The leakage was measured using a 10× stereomicroscope (Vardhan, India) by measuring the distance from the coronal extent of the orifice material to the greatest depth of penetration of the dye. Statistical analysis was performed using the Statistical Package for Social Sciences version 11.5 for MS Windows (SPSS Inc, Chicago, IL).

RESULTS

The data obtained was subjected to statistical analysis using analysis of variance (ANOVA) and Tukey's tests. Table 1 shows mean depth of penetration in millimeters for each material.

Table 1

Mean and standard deviation values of experimental groups

Experimental samples of the Group 1 leaked 5.33 ± 0.57 mm into the gutta-percha. Group 2 showed the maximum leakage at 2.86 mm mean penetration while Group 4 showed the least at 1.79 mm mean penetration. There was statistically significant difference between Groups 2 and 4. There was no statistical difference in leakage (P > 0.01) between Group 3 and Group 4. The Mean and Standard Deviation of experimental groups is shown in Figure 1.

Figure 1

Mean and standard deviation of experimental groups

DISCUSSION

The complete removal of necrotic debris, microbes, and their byproducts followed by obturation of the root canal space is the major goal of endodontic therapy. This results in the prevention of microleakage by creating a fluid tight seal and the ingress of oral fluids and microorganisms into the root canal.

A host of the anatomical parameters and clinical considerations influence the outcome of nonsurgical RCT. However, microleakage is the most commonly encountered problem influencing the long-term success of endodontic treatment.

Previously, apical microleakage was considered to be the main cause for failure of RCT. Dow and Ingle stated that failure most commonly occurs due to inadequate apical seal. However, studies have shown that a good coronal seal is equally important.[8]

Teeth obturated with gutta-percha and sealer, in the absence of a temporary restoration, showed leakage ranging from 70 to 85% of the root length within 56 days when exposed to saliva.[9]

Literature reports emphasize the need of an early final restoration.[10] Iowa group stated that “The need for an immediate and proper coronal restoration after RCT is important”.[11] GIC is used commonly as an intraorifice barrier. At University of Tenesse, the Himel group reported that “the teeth without an intraorifice barrier leaked significantly more than the teeth with glass ionomer intraorifice barrier”.[12]

A recent study conducted by Malik et al.,[13] states that “mineral trioxide aggregate (MTA) and GIC as an intracanal barrier and sealer with good sealing ability for obturation may be used to minimize microleakage in endodontically treated teeth”.

Hence the present study was undertaken to evaluate and compare the intraorifice sealing ability of LCGIC, Tetric N-Flow, and LCGIC + Tetric N-Flow used in combination after obturation of the root canal system.

Dye penetration method to check the microleakage is a simple, easy, and cost-effective method. This study used Rhodamine-B dye as it has small particle size, better penetration, water solubility, diffusability, and hard tissue nonreactivity.[14] The dye has been used under vacuum penetration method as it helps to remove entrapped air which can prevent complete dye penetration.[15]

The present study utilizes a material thickness of 3.5 mm to seal the coronal orifice as literature reports state that 3.5 mm of material is the minimum thickness required in coronal restoration to prevent leakage.[16]

The results of the present study indicate that LCGIC + Tetric N-Flow and LCGIC demonstrated a significantly better seal than Tetric N-Flow. Microleakage in samples where LCGIC was used as an intraorifice barrier showed more microleakage than the samples where a double intraorifice barrier of LCGIC + Tetric N-Flow was used. However, there was no statistically significant difference between the two groups.

Better seal in flowable composite (Group III) and LCGIC with flowable composite group (Group IV) may be attributed to the command setting and better adhesion with tooth structure. Resin modified GIC's set by two mechanisms: Acid base and photochemical polymerization of water soluble monomer and methacrylate groups.[17] Polymerization shrinkage still occurs largely due to the resin component; however, immature cement continues to take up fluid from dentin causing the material to expand which compensates for polymerisation shrinkage.[18] Better sealing ability of LCGIC may be attributed to:

Adhesion of LCGIC by development of an ion-exchange layer adjacent to dentin and

Shear bond strength of LCGIC which is higher than conventional GIC.[192021]

Tetric N-Flow has shown more leakage than LCGIC + Tetric N-Flow and LCGIC groups. This observation is in accordance to studies conducted by Diaz-Arnold and Wilcox, Carman and Wallace, Roghanizad and Jones, and Galvan et al., where composite showed substantial leakage.[22232425]

CONCLUSION

Thus, the present study concludes that double seal is required which could be achieved by using an intraorifice barrier to reduce microleakage. In the current study, LCGIC + Tetric N-Flow was found to be superior over other experimental materials as intraorifice barriers. However, further long-term research may confirm better clinical results.