## 4 Discussion  
This systematic review aimed to assess evidence-based findings and evaluate the advantages and disadvantages of commonly used filling materials in endodontic retrograde surgery. Clinical studies demonstrated that various materials--including Super EBA, MTA, IRM(r), Retroplast, Endosequence(r), and gutta-percha--have been effectively employed. The follow-up periods ranged from 6 months to 17.5 years, and the included studies encompassed randomized clinical trials, non-randomized clinical trials, and descriptive designs. The primary purpose of retrograde root-end filling materials is to create a durable and tight apical seal that prevents bacterial leakage and reinfection of the root canal system. Ideally, these materials should not only provide a hermetic seal but also possess antimicrobial properties and promote periapical tissue regeneration. While the selection of these materials should be based on solid scientific and clinical evidence, current endodontic practices are often influenced by a combination of historical precedents, expert opinions, and manufacturers' claims, which may not always reflect the highest levels of evidence [59, 60, 61, 62, 63, 64]. To enhance the clinical relevance of the findings, this review included only clinical studies. Although randomized controlled trials with extended follow-up are the gold standard, they are not always available for every new material or clinical situation. Thus, non-randomized trials and observational studies provide valuable real-world insights that bridge the gap between laboratory findings and practical clinical application [24, 31]. These studies are particularly important when evaluating newer materials, as they may exhibit beneficial properties not found in conventional options. Super EBA is a reinforced zinc oxide-eugenol (ZOE) cement recognized for its excellent sealing capacity, biocompatibility, and handling characteristics. Its formulation consists of 60% zinc oxide, 34% alumina, and 6% natural resin, along with a liquid phase containing 62.5% ortho-ethoxybenzoic acid (EBA) and 37.5% eugenol [65]. The original formulation--Stialine Super EBA--was later modified by the Harry J. Bosworth Company by replacing silica with alumina in the powder while maintaining the same liquid component [66]. Introduced in the 1970s, Super EBA was rapidly adopted due to its plasticity, which facilitated manipulation and placement. It adheres well to dental walls even under moist conditions, exhibits short setting times, and can bond to itself for incremental placement. Scanning electron microscopy studies have shown good marginal adaptation, with evidence of collagen fibers integrating into the material [67, 68]. Mechanically, it offers high compressive and tensile strength, neutral pH, and low solubility [69]. Despite the presence of eugenol--a known cytotoxic agent--its release is minimized due to the reinforced nature of the cement. Cytotoxicity is mainly observed during the \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Study** & **Q1** & **Q2** & **Q3** & **Q4** & **Q5** & **Q6** & **Q7** & **Q8** & **Score** \\ \hline [PERSON], 2008 [51] & Y & Y & Y & Y & N & N & Y & Y & 6 \\ [PERSON], 2009 [52] & Y & Y & Y & Y & N & N & Y & Y & 6 \\ [PERSON], 2015 [53] & N & Y & Y & Y & N & N & Y & N & 4 \\ [PERSON], 2016 [54] & Y & Y & Y & Y & N & N & Y & Y & 6 \\ [PERSON], 2019 [55] & Y & Y & Y & Y & N & N & Y & Y & 6 \\ [PERSON], 2019 [56] & U & U & Y & Y & N & N & Y & Y & 4 \\ [PERSON], 2020 [57] & Y & Y & Y & Y & N & N & Y & N & 5 \\ [PERSON], 2022 [58] & Y & Y & Y & Y & N & N & Y & N & 5 \\ [PERSON], 2024 [59] & N & Y & Y & Y & N & N & Y & N & 4 \\ [PERSON], 2024 [60] & Y & Y & Y & Y & N & N & Y & Y & 6 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Quality assessment of the included cross-sectional studies using the Joanna Briggs Institute (JBI) critical appraisal checklist. initial setting phase but decreases significantly once the material has hardened [70; 71].