Endodontic surgery may become the last resort for salvaging the affected tooth, if conventional endodontic treatment fails and retreatment is neither indicated nor feasible. Removal of the infected root-end and sealing any remaining bacteria in the root canal system from the periradicular tissues is the goal of surgical intervention.11 The surgical procedure includes three critical steps to eliminate persistent endodontic pathogens: 1) surgical debridement of pathological periradicular tissue, 2) root-end resection (apicoectomy), and 3) retrograde root canal obturation (root-end filling).
Kim S and Kratchman S suggested removing at least 3 mm of the root-end which reduces 98% of the apical ramifications and 93% of the lateral canals. They also proposed that root-end amputation of less than 3mm does not remove all of the lateral canals and apical ramifications which poses a risk of reinfection and eventual failure.12 Apart from amount, the plane of sectioning is to be considered equally during root resection. Ideally, the short bevel (0°) that is as perpendicular to the long axis of the tooth as possible conserves the root length and exposes less dentinal tubules thereby opening less tubules to be exposed to the environment, which allows less microleakage over a period of time.13
Taschieri S et al. investigated the quality of root-end filling in cases of periapical lesions persisting after endodontic surgery. Failure of apicoectomy was because of an imperfect seal at the interface between the root-end filling and the cavity margin. The presence of such a gap would favour a continuous bacterial leakage from the infected root canal system to the periapical tissue thereby sustaining inflammation.14 According to Cohen, the ideal root-end filling material should seal the contents of the root canal system within the canal, prevent egress of any bacteria, bacterial by-products, or toxic material into the surrounding periradicular tissues.15 Various studies have emphasized the importance of root-end fillings in outcomes of apicoectomies by reporting that teeth with root-end fillings showed favorable results compared with those without root-end fillings.16,17,18 Therefore, sealing the root apex with a proper root-end filling material is crucial.
Various experiments can be carried out to evaluate the microleakage like dye extraction, dye penetration, radioisotope, bacterial penetration, fluid filtration etc. The dye penetration method used for measuring sealing ability is the popular and most widely used but this technique suffers from severe limitations. This technique relies on randomly cutting the root into two pieces, without knowing if the section goes through the deepest dye penetration so it under evaluates the dye penetration and gives randomly chosen results.10 Apart from that, the measurement of leakage is qualitative too. Whereas, in dye extraction method, all the dye that leaked through the apex is recovered by dissolving in acid which avoids the limitations of sectioning the root and it also quantitatively measures the optical density of the solution by the use of a spectrophotometer thus provides reliable results in microleakage studies. However, sample storage in 10% formalin may introduce a significant source of experimental variability influencing leakage results as compared to freshly extracted teeth.
In the present study, the mean±S.D OD for GIC-Carbide as compared to MTA-Carbide and Biodentine-Carbide was found to be statistically significant difference (p = 0.0001). Similarly, the mean±S.D OD for GIC-Diamond as compared to MTA-Diamond and Biodentine-Diamond was also statistically significant difference (p = 0.0001). This result shows that the microleakage occurs more in one material as compared to others. However, while comparing GIC with negative control, it shows the significant difference in the microleakage but
comparing MTA and Biodentine with negative control it shows statistically non-significant difference representing that MTA and Biodentine have better apical seal as compared to GIC.
Moreover, in the present study the mean±S.D OD for MTA-Carbide (0.278±0.042) and Biodentine-Carbide (0.139±0.033) was statistically non-significant difference (p = 0.127). Similarly, the mean±S.D OD for MTA-Diamond (0.254±0.055) and Biodentine-Diamond (0.153±0.038) was also statistically non-significant difference (p = 0.496) showing the comparability of both materials in providing apical seal. In the same way, mean±S.D OD of MTA-Carbide and MTA-Diamond with were statistically non-significant difference as compared to negative control (p = 0.084 and p = 0.234) respectively. Likewise, mean±S.D OD of Biodentine-Carbide and Biodentine-Diamond were also statistically non-significant difference as compared to negative control (p = 1.000). Hence, MTA and Biodentine had similar apical sealing ability as observed by its optical density near to negative control which was statistically non-significant. Apart from that, the mean±S.D OD of Biodentine was lower
than that of MTA representing Biodentine is the best material for preventing apical microleakage.
Mineral Trioxide Aggregate has been proven to show less microleakage compared to other materials. However, in this study the least microleakage was exhibited by Biodentine although the difference was not statistically significant. The result of our study is in concurrence with the study conducted by Khandelwal A et al., Radeva E et al., Naik MM et al., Kokate SR et al. Comparing the sealing ability of MTA and Biodentine as root-end filling material Khandelwal A et al.19 concluded that Biodentine can be used as a replacement for MTA. The study by Radeva E et al.20 concluded that Biodentine can be more effective as apical sealing material compared to MTA. Naik MM21 concluded that the apical seal obtained with Biodentine was superior to that obtained with MTA.
Similarly, Kokate SR et al.22 compared the microleakage of MTA, GIC & Biodentine using dye penetration method under stereomicroscope. The results of their study showed that there was significantly less leakage in Biodentine when compared to MTA & GIC. This result is in agreement with the present study. However, the study conducted by Mandava P23 et al. evaluated the apical microleakage of root-end cavities filled with MTA, Biodentine and LC GIC using two different cavity preparation techniques that is conventional bur preparation and ultrasonic tip preparation. The result of their study showed significantly less microleakage of MTA compared to Biodentine and LC GIC, which is in contrast to our study.
In the current study, two different burs were used for preparing retrograde cavity. The rationale behind using two different burs is to determine the effect of smear layer on microleakage. Surgical smear layer in endodontics is defined as a smear layer, which contains microorganisms and necrotic pulpal tissues which is formed on the dentinal surfaces, cut by the instruments during apicoectomy and retrograde cavity preparation.21 Citric acid, EDTA, 35% orthophosphoric acid and BioPure MTAD™ (mixture of tetracycline isomer, acid and detergent) have been recommended for the removal of surgical smear layer but in our study no attempt was done to remove it as the retrograde cavity was just irrigated with normal saline. The thickness of the smear layer is also affected by type of the bur used. Several studies have demonstrated that carbide bur produces thinner smear layer compared to that of diamond bur.24,25,26 However, the current study showed the mean±S.D OD of GIC-Carbide and GIC-Diamond, MTA-Carbide and MTA-Diamond and Biodentine-Carbide and Biodentine-Diamond respectively with statistically non-significant difference (p = 1.000). Hence, in this study, the comparable nature of two different retrograde preparations were
observed and can be used according to ease.
As in vitro evaluation does not always reveal their in vivo performance, hence clinical testing are still required for higher impact of result.