A Vitro Study Of The Apical Sealability Of Different Root Canal Sealers

Background and Objective:The primary goals of root canal treatment are to debride and disinfect the root canal space to the greatest possible extent, and to seal the canals as effectively as possible, aiming to establish or maintain healthy periapical tissues. Three-dimensional obturation of the canal space to the working length has been depicted as the most critical component of root canal treatment. Currently, the best filling material universally considered is gutta-percha associated with a thin layer of cement used in many techniques and procedures. As the complication and irregularities of the root canal system, appropriate sealer selection play an important role in the outcome of endodontic treatment. In the last years, a variety of sealers became commercially available, but there is still no root canal sealers which can completely meet the requirements of ideal sealer. A new obturation sealer, iRoot SP has recently been introduced to the endodontic treatment which has both excellent physical properties and biocompatibility. For now most of the studies of the apical sealing ability of iRoot SP were performed with methods based on microleakage. And only scant knowledge is available with using Micro-CT. In this study, the evaluation of the apical sealing ability of iRoot SP, AH Plus and Apexit Plus sealer was performed with the dye extraction method and micro-CT, in order to providing sufficient experimental evidence in selection of an appropriate root canal sealer in root canal treatment.Methods:75 human single-root teeth were selected for study. Conventional opened the pulp, removed the pulp and prepared the canals toF3 by using a crown-down technique with rotary ProTaper nickel-titanium files. The specimens were randomly divided into 6 experimental groups(group A1, group B1, group C1, group A2, group B2, group C2) with 10 samples each and 3 control groups (group D, group E, group F) with 5 samples each.Group A1 and A2:The root canals were obturated with iRoot SP with Continuous wave condensation technique(n=10).Group B1 and B2:The root canals were obturated with AH plus with Continuous wave condensation technique(n=10).Group C1 and C2:The root canals were obturated with Apexit Plus with Continuous wave condensation technique(n=10).Group D:The root canals were obturated without root canal sealers with Continuous wave condensation technique(n=5). Group E(n=5) and group F(n=5):the teeth were not obturated. Ensure that all specimens were in the same length, they were resected 10 mm from the apex. Access cavities of all root canal were obturated with glass ionomer cement.Each tooth of Group A1, B1, Cl and D which was positioned to the specimen stage was scanned with a high-resolution micro-CT to gain images. The images would be reconstructed by software to show two-dimensional (2D) slices of the inner structure of the roots. Then, the Mimics was used for the three-dimensional (3D) volumetric visualization analysis to measure the volume of interface voids and gaps formation in the obturated root canals. The volume fraction of voids and gaps of the coronal, middle and apical of the root canal filling was analyzed separately.All the teeth of groups A2, B2, C2 and E were coated with two layers of nail varnish, except for the area of 2 mm away from the apical foramen. Group F were completely coated with two layers of nail varnish, including the apex of the root. The apical microleakage was evaluated by dye peneration method. After immersed in 65% nitric acid for extracting dye, absorbance of concentrated nitric acid and extracted dye were evaluated with a Biophotometer at 600 nm.Results:1. Micro-CT scans of specimens provided a good visualization of tooth dentin, sealant material, and gutta-percha. Therefore, the 3D reconstruction of all specimens revealed the presence of voids and gaps at the interface between the root canal dentin and the gutta-percha sealer filling in all investigated groups.2. Images obtained from the scan were reconstructed for the three-dimensional (3D) volumetric visualization analysis to measure the volume of interface voids and gaps formation in the obturated root canals inner structure of the roots. Statistical analysis demonstrated that only gutta-percha obturation induced significantly more voids and gaps than other tested materials, and Apexit Plus sealer induced significantly more voids and gaps than iRoot SP sealer and AH plus sealer. No significant difference was found between iRoot SP sealer and AH plus sealer (P>0.05). The amount of voids and gaps significantly was higher in the apical region.3. By using the dye penetration method to evaluate three root canal sealers’s ability, there was more microleakage in Apexit Plus compared with the leakage in the iRoot SP and AH plus (P<0.05). But the extent of leakage was not statistical difference between the two groups (P>0.05).Conclusion:1. These data indicate that none of the root canalfilled teeth were free of gaps. Compared with obturation with only gutta-percha, the voids and gaps significantly reduced with root canal sealer, increasing the adaptability of dental gutta-percha for the root canal wall.2. iRoot SP displayed similar apical sealing ability to AH plus in vitro. Both iRoot SP and AH plus are significantly better than Apexit Plus.