Introduction

Root canal filling represents a critical phase in endodontic treatment, aimed at sealing the canal system, preventing reinfection, and supporting long-term success. The quality of root canal filling, including its apical sealing, homogeneity, and adaptation, has been identified as an important factor influencing the prognosis of treated teeth1,2,3. An optimal apical seal is critical to prevent microbial leakage and minimize post-treatment disease.

Historically, root canal fillings have been completed using a combination of core materials and sealers. The cold lateral condensation (CLC) technique, recognized as the classical technique, remains the most widely used due to its predictable control of filling length and cost-effectiveness4. However, its limited ability to achieve three-dimensional sealing, particularly in irregular canal spaces, led to the introduction of warm vertical compaction (WVC) technique by Schilder in 1967, which improved material adaptation to the canal system, particularly its apical and lateral irregularities5. Since then, more advanced thermoplastic techniques have evolved, such as continuous wave condensation, injection-molded gutta-percha, and carrier-based (CB) techniques, each presenting distinct advantages and limitations based on specific clinical scenario6,7.

Despite these advancements, the impact of obturation technique on treatment outcomes remains unclear. While early studies focused primarily on radiographic parameters such as the extent of the root filling relative to the apical foramen8,9,10, recent evidence has reinforced the critical role of achieving a well-sealed apical third to ensure treatment success11,12. However, most of the existing literature focused on the radiographic quality of root canal fillings, with little emphasis on direct comparisons of success rates between different techniques and materials. In recent years, bioceramic sealers have gained popularity due to their bioactivity and superior sealing potential. However, high-quality comparative studies directly evaluating their performance against traditional sealers in both primary root canal treatments (RCTs) and retreatment cases (re-RCTs) remain limited. This gap in evidence is significant, as prior filling materials can complicate retreatment procedures and influence outcomes.

With the increasing use of single-cone (SC) techniques with bioceramic sealers, alongside established methods such as CLC, WVC, and CB, there is a need for rigorous clinical comparisons. Evaluating success rates across these methods, particularly in retreatment cases, could offer clinicians evidence-based guidance for optimizing treatment protocols. Therefore, this systematic review and meta-analysis compared the clinical and radiographic success rates of root canal filling techniques and materials, aiming to support standardized and effective endodontic care.

Materials and methods

Protocol and registration

This systematic review and meta-analysis adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines13 to promote comprehensive and transparent reporting, and follows the methodological approach of a recent publication14. The protocol was registered in the PROSPERO international prospective database (Registration ID: CRD42024524608), which provides a publicly accessible record of the study plan and methodology.

Focused research question

Using the PICOTSS framework, this systematic review addressed the following question: In human permanent teeth undergoing RCT or re-RCT (P), do different obturation techniques and/or materials (I), compared with alternative ones (C), influence endodontic treatment outcomes (O) at a minimum follow-up of six months (T), based on evidence from clinical studies conducted in dental or academic settings (S, S)?

Endodontic treatment outcomes were defined a priori as clinical and radiographic success. Prespecified subgroup analyses included treatment type (RCT and re-RCT), obturation technique (CLC, WVC, WLC, SC, CB), follow-up duration, and study design.

Eligibility criteria

This systematic review included randomized controlled trials and cohort studies published in any language up to November 30th, 2025. Studies were included if they involved permanent teeth, described the root canal filling technique and material, had a minimum follow-up of six months, and reported a dropout rate ≤ 25%, aligning with previous meta-analysis in Endodontology107. Outcomes had to be assessed using defined clinical and radiographic criteria.

Studies were excluded if they were case reports, case series, review articles, or animal and in vitro studies. Research involving primary teeth, studies with incomplete information on techniques or materials, or those without clear radiographic and clinical outcomes were also excluded.

Search strategy

A comprehensive electronic search was performed independently by two authors across three major databases: PubMed (National Center for Biotechnology Information), Cochrane Library (John Wiley & Sons, Ltd), and ScienceDirect (Elsevier). The search was conducted without language or publication date restrictions to ensure the inclusion of all relevant studies.

To improve the completeness of the search, grey literature was explored using the following sources: CADTH’s Grey Matters (https://greymatters.cadth.ca/), The European database on medical devices (EUDAMED) (https://ec.europa.eu/tools/eudamed/#/screen/home), and The New York Academy of Medicine Library (https://catalog.nyam.org/cgi-bin/koha/opac-search.pl). A manual search was also conducted to review relevant journals, including the International Endodontic Journal, Journal of Endodontics, Clinical Oral Investigations, European Endodontic Journal, Scientific Reports, and the Australian Endodontic Journal, bibliographies of included studies, and conference proceedings to capture any missed publications or unpublished data.

The search strategy utilized a combination of MeSH terms and relevant keywords, including “root canal treatment,” “endodontic therapy,” “prognosis,” “outcome,” “root canal obturation,” and “root canal retreatment,” combined using Boolean operators such as ‘AND’ to narrow the search and ‘OR’ to include synonymous terms. The full applied search strategy for PubMed/Medline is presented in Table 1.

Table 1 Applied search strategy in PubMed/Medline electronic database.
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Screening and study selection

Initial screening was performed from June 1 to August 14, 2023. The search was subsequently updated, and the final screening was completed on November 30, 2025, to include the most recent eligible studies. Duplicate records were removed prior to title and abstract screening. Study selection was independently performed by two reviewers (A.M. and S.A.). Any disagreements were resolved by consensus, and when necessary, a third reviewer (F.E. or K.I.A.) acted as an arbitrator.

Data extraction

After reviewing the titles and abstracts of the search results, studies that potentially met the inclusion criteria were subjected to full-text evaluation. Data extraction followed a predefined standardized collection form to ensure consistency and accuracy. Extracted information included study details such as authors, year of publication, and study design (randomized or cohort), along with sample characteristics including sample size, patient age, gender, and pulp/periapical status. Treatment-specific details were recorded, including the type of treatment (primary root canal treatment or retreatment), root canal filling techniques, materials, cement type, instrumentation technique, and irrigants used. Additional clinical variables extracted comprised tooth type, rubber dam utilization, operator skill, number of treatment sessions, and microscope use. Follow-up periods were classified into four distinct time points: 6 months, 12 months, 24 months, and more than 3 years.

Outcomes were assessed based on radiographic evaluations and resolution of clinical signs and symptoms, with data extracted for all reported follow-up periods to ensure a comprehensive analysis. Any disagreements between the two independent reviewers during the data extraction process were resolved through discussion. If consensus could not be reached, a third reviewer (F.E. or K.I.A.) served as an impartial arbitrator to finalize decisions.

Quality assessment

To evaluate the risk of bias, two independent reviewers (A.M. and S.A.) conducted quality assessments for all included studies. For randomized studies, the revised Cochrane RoB2 tool15 was employed, addressing five key domains: randomization process, deviations from intended interventions, missing outcome data, outcome measurement, and reporting bias. For non-randomized studies, the ROBINS-I tool16 was utilized, assessing bias across seven domains including selection bias, performance bias, attrition bias, and reporting bias. Disagreements were resolved by discussion; if unresolved, a third reviewer (F.E. or K.I.A.) acted as an impartial arbitrator. The assessments were performed using RevMan 5.4 software (Cochrane Collaboration) to ensure systematic organization and visualization of results.

The overall certainty of evidence was evaluated using the GRADE system, which accounts for risk of bias, inconsistency, imprecision, and overall confidence in the evidence. This systematic approach allowed for a comprehensive evaluation of study quality and evidence strength.

Statistical analysis

A comprehensive meta-analysis was conducted using a mixed-effects model, with root canal filling techniques serving as the moderator variable. To account for heterogeneity among studies, a restricted maximum likelihood estimator was applied. The overall effect size was presented using forest plots with 95% confidence intervals to illustrate the raw rate of successful outcomes across the included studies. Heterogeneity between studies was evaluated using Cochran’s Q test and quantified through the I² index, which represents the proportion of variability attributable to between-study differences. A funnel plot analysis was performed to visually inspect the potential presence of publication bias, while Egger’s test was used to statistically assess its significance. A significance level of α = 0.05 was applied to all statistical tests.

Subgroup analyses were performed to explore factors contributing to heterogeneity, including root canal filling techniques, material types, and moderating factors such as patient age, gender, tooth type, anesthetic solution, and treatment type (primary or retreatment). A meta-regression analysis was performed using a mixed-effects model to quantify the influence of these covariates on treatment outcomes. Results were reported as beta coefficients (β) with 95% confidence intervals and Z statistics, facilitating a clearer understanding of variable relationships. All statistical analyses were conducted using R software (version 4.3.1) (R Core Team, 2023), a robust statistical computing platform widely used in meta-analyses.

Results

Study selection

The study selection followed PRISMA guidelines (Fig. 1). From 44,602 initial records, 484 full texts were assessed after duplicate removal and title/abstract screening. Of these, 341 were excluded due to ineligible design, insufficient follow-up, or incomplete outcomes (Suppl. Table 1). A total of 84 studies met inclusion criteria and were included in qualitative and quantitative analyses (Table 2).

Fig. 1
Fig. 1
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PRISMA flow diagram: visual representation of the study selection process.

Table 2 Characteristics of the included studies.
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Characteristics of included studies

The analysis incorporated 11,965 samples from 84 studies, consisting of 42 randomized controlled trials and 42 cohort studies (prospective and retrospective). These studies focused on RCT, re-RT, and apexification, categorized by different follow-up periods.

For primary root canal treatment, studies were grouped by follow-up intervals. Nine studies evaluated treatments over a 6-month period, analyzing four techniques: WVC, SC, CLC, and CB. For the 12-month period, 32 studies investigated six techniques, including WVC, SC, CLC, TH, and CB. Eighteen studies reported results for the 24-month period, covering WVC, SC, CLC, and CB techniques. Ten studies assessed outcomes at three or more years, with comparisons between WVC, WLC, CLC, SC, and CB techniques.

For retreatment procedures, two studies reported results at 6 months, evaluating SC and CLC techniques. At 12 months, ten studies examined WVC, SC, and CLC, while eight studies analyzed WVC, CLC, SC, and CB at 24 months. Results for follow-up beyond three years were reported in five studies, focusing on CLC, WVC, SC, and CB techniques. Additionally, nine articles explored the apexification technique across various follow-up durations.

Meta-analysis

The success rate for root canal filling techniques was estimated using meta-analysis, with follow-up durations serving as the moderator variable is illustrated in Fig. 2. For primary root canal treatment, the overall success rate at six months was 87.1% (95% CI: 80.2–94.0). No statistically significant differences were observed between techniques; for instance, SC showed a non-significant 3.2% lower success rate compared to CLC (p = 0.766). At 12 months, the success rate remained 87.2% (95%CI: 84.3–90.1), with no significant differences across techniques (p = 0.677). By 24 months, the success rate improved to 92.0% (95%CI: 89.9–94.1), with CLC and CB techniques demonstrating significantly better results compared to WVC (p = 0.021 and p = 0.011, respectively), Furthermore, SC exhibited significantly worse results compared to both CLC and CB (p = 0.001). The success rate beyond three years was 84.9% (95%CI: 80.8–89.0), and no significant differences between techniques were observed.

For retreatment procedures, the overall success rate at six months was 92.9% (95% CI: 88.6–97.2); however, limited data restricted further comparisons. At 12 months, the success rate was 77.0% (95%CI: 69.2–84.9), with SC demonstrating a marginally significant improvement of 16.7% over CLC (p = 0.045). The success rate at 24 months was 83.5% (95%CI: 74.7–92.2), with CB performing significantly better than WVC (p = 0.004). Beyond three years, the overall success rate dropped to 73.7% (95%CI: 67.4–80.0); although CB showed a 7.9% improvement over CLC, the difference was not statistically significant (p = 0.179). A separate analysis revealed that the apexification technique demonstrated significantly higher success rates compared to CLC at the 12-month follow-up (p = 0.019) (Suppl. Figure 1).

Meta-regression analysis

The meta-regression analysis examined the impact of various independent factors, including mean age, gender distribution, tooth position, operator expertise, and materials used (Suppl. Table 2). Tooth position significantly influenced outcomes, with maxillary teeth showing superior success rates (p = 0.006). Operator expertise also played a critical role, with specialists achieving significantly higher success rates compared to general dentists and students (p < 0.001). Material comparisons revealed marginal significance for zinc oxide eugenol compared to AH-Plus or glass ionomer cements (p = 0.091 and p = 0.080, respectively).

Qualitative assessment

Risk of bias was assessed using RoB 2.0 (randomized) and ROBINS-I (cohorts). Among RCTs, 27 had “some concerns,” others were low risk. Cohort studies mostly had serious bias, especially in outcome reporting; one study had critical participant selection bias (Fig. 3). GRADE assessment rated five outcomes as very low and three as low certainty, including 12- and 24-month RCT outcomes and 12-month re-RCT results (Table 3).

Fig. 2
Fig. 2
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Forest plots for primary root canal treatments at different follow-up periods: (a) 6 months, (b) 12 months, (c) 24 months, and (d) 3 + years. For root canal retreatments, the outcomes are presented for (e) 6 months, (f) 12 months, (g) 24 months, and (h) 3 + years.

Fig. 3
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Summary of risk of bias assessment using (a) ROB 2.0 for randomized clinical trials and (b) ROBINS-I for non-randomized studies.

Table 3 Summary of findings using the GRADE approach for evaluating clinical and radiographic outcomes.
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Discussion

This systematic review and meta-analysis evaluated the clinical and radiographic success rates of root canal filling techniques and materials in both primary RCTs and re-RCT across different follow-up periods. The study incorporated an extensive search strategy and included both randomized controlled trials and cohort studies to ensure robust and reliable findings.

Primary root canal treatments.

The results of the meta-analyses for primary RCTs showed consistently high overall success rates at the 6- and 12-month follow-up periods, with no statistically significant differences observed between techniques such as SC, CLC, WVC, and CB. These findings align with previous systematic reviews101,102, which similarly reported comparable outcomes among various techniques in short-term follow-ups. The SC technique, in particular, has gained clinical popularity due to its simplicity and the growing use of bioceramic sealers, which are desirable for their bioactivity and sealing properties103,104.

Within the limitations of current evidence, significant differences emerged at the 24-month follow-up period, where SC exhibited lower success rates compared to CLC and CB techniques, which showed 8.8% and 11.3% higher success, respectively. These results may reflect the better adaptation of filling materials achieved with CLC and CB, particularly in more challenging long-term scenarios. However, these differences could also be attributed to factors beyond the inherent sealing ability of the techniques. Variations in sample size and study design can significantly influence statistical outcomes, potentially exaggerating the effectiveness of one technique over another. For instance, variations in sample size and study design can introduce statistical bias, potentially exaggerating the effectiveness of one technique over another. Therefore, further high-quality randomized controlled trials are needed to confirm clinical significance.

A systematic review reported an overall success rate of 83% for core-carrier obturation but noted considerable variability among included studies, demonstrating the impact of sample size and methodology on outcomes105. Additionally, differences in case selection, such as tooth type, canal anatomy, and preoperative conditions, may have contributed to the observed success rates. Studies have shown that teeth with simpler anatomies or fewer complications are more likely to yield favorable outcomes, irrespective of the obturation technique used11.

Operator expertise includes not only technical proficiency but also case selection, complication management, and adherence to aseptic protocols. Moreover, clinicians’ familiarity with specific obturation methods can directly affect the quality of the root canal filling and treatment outcomes. These facets together are fundamental in achieving successful endodontic therapy. For instance, a study comparing CB and lateral compaction techniques concluded that both methods could achieve comparable success rates, with outcomes heavily influenced by operator skill rather than the technique itself106. These findings suggest that the apparent success observed with CLC and CB techniques at 24 months is likely multifactorial, involving variables such as case complexity, operator expertise, and study design rather than solely reflecting the sealing capabilities of the obturation materials. Despite these findings, success rates for all techniques converged beyond the 3-year follow-up period, with no statistically significant differences reported among WVC, WLC, CLC, and CB, suggesting that long-term clinical outcomes may be determined by factors unrelated to the technique itself. However, these differences were not sustained beyond 3 years, where outcomes converged across techniques. Given the low/very-low certainty of evidence and the influence of operator expertise and case selection, these intermediate differences should not be interpreted as technique-dependent superiority.

Root Canal retreatment outcomes

Retreatment analyses were limited by the scarcity of available studies, particularly for the 6-month follow-up period, where only two studies were included17,25. At the 12-month interval, analyses incorporating WVC, CLC, and SC techniques revealed no significant differences in success rates. Similarly, the 24-month follow-up data demonstrated comparable outcomes between WVC, CLC, SC, and CB techniques. Interestingly, CB showed a numerical advantage over CLC beyond the 3-year follow-up, though statistical significance was not achieved. These findings accentuate the need for additional high-quality studies investigating retreatment procedures to draw more reliable conclusions.

Influence of bioceramic sealers

The SC technique has been closely associated with bioceramic sealers, which have emerged as a promising alternative to traditional epoxy resin-based cements (e.g., AH-Plus). While bioceramic sealers have shown excellent biocompatibility, biomineralization potential, and enhanced sealing properties96,97,98,99, their long-term clinical outcomes remain inconclusive. Consistent with our findings, no long-term clinical advantage of bioceramic sealers over AH Plus has been demonstrated to date102. Most supportive evidence derives from in vitro or short-term studies, and the difficulties in retreatment removal remain unresolved. These findings are consistent with prior reviews107, which highlight the need for long-term, well-designed clinical trials to validate the clinical benefits of bioceramic materials.

Despite their advantages, bioceramic sealers pose challenges in retreatment scenarios due to the difficulty in removing them efficiently from the root canal system108. This limitation denotes the importance of careful case selection and the development of standardized protocols for their removal, particularly in cases requiring further intervention.

Clinical implications

While newer obturation techniques and materials may offer certain practical advantages, no single approach consistently outperforms others across follow-up periods. Modest 24-month (mid-term) differences observed for some techniques (slightly higher success of CLB and CB) should be interpreted with caution109, as operator expertise and case selection are likely more decisive factors. Long-term success remains multifactorial and is less dependent on technique, suggesting that operator expertise, case complexity, and patient-specific factors play a central role in treatment success. Nonetheless, given that many outcomes were rated as having low or very low certainty of evidence, these findings should be interpreted with caution, and strong clinical recommendations cannot be made at this stage.

Operator experience emerged as a critical factor influencing success rates, with specialists achieving significantly better outcomes compared to general practitioners and students. This finding supports advanced training and skill development in endodontics to optimize clinical outcomes. Additionally, anatomical factors, such as differences between maxillary and mandibular teeth, were associated with varying success rates, with maxillary teeth exhibiting higher success, possibly due to their more accessible anatomy.

Methodological amendments

This study incorporated key deviations from the initial protocol to improve clinical relevance. For instance, the inclusion criteria were adjusted to allow a dropout rate of up to 25%, as attrition rates above 20–30% are known to increase the risk of bias and compromise the validity of study outcomes. This threshold was selected to maintain methodological rigor while enabling the inclusion of a broader range of relevant endodontic clinical studies, consistent with approaches used in previous systematic reviews. Data extraction and subgroup analyses included additional factors such as tooth position, operator expertise, and material adaptation, enabling a more comprehensive assessment of treatment outcomes. To address heterogeneity, a mixed-effects meta-regression model replaced separate network meta-analyses, providing a standardized approach to outcome assessment across diverse time intervals. Quality assessment integrated ROBINS-I and the GRADE system alongside RoB 2, permitting a robust evaluation of bias and evidence certainty. Additionally, special attention was given to the impact of bioceramic sealers, particularly their influence on retreatment challenges and long-term clinical success.

Strengths and limitations

The strengths of this review include a comprehensive search strategy, adherence to PRISMA guidelines, and rigorous quality assessment using the ROB 2.0, ROBINS-I, and GRADE tools. This systematic review and meta-analysis included a wide range of studies, offering valuable insights into the performance of various obturation techniques and sealers. However, the inclusion of both RCTs and cohort studies, variation in operator expertise and case selection, and differences in follow-up durations (ranging from 6 months to over 3 years) limit direct comparability of results and contribute to heterogeneity. These factors underscore the need for cautious interpretation of pooled estimates. Nevertheless, certain limitations must be acknowledged. Given the considerable methodological heterogeneity among included studies, including the limited number of studies assessing retreatment procedures, particularly with shorter follow-up periods, differences in operator training, case selection, and follow-up intervals, our conclusions must be interpreted with caution. Although trends were identified, the low certainty of evidence as per GRADE and the limited number of studies available (particularly in re-RCTs cases), limit the formulation of strong clinical recommendations based solely on the study findings. Publication bias, though assessed, cannot be entirely ruled out. Consequently, no conclusive clinical practice guidelines can be proposed at this stage.

Further research

Future studies should prioritize well-designed, randomized controlled trials with standardized protocols for evaluating root canal filling techniques and materials to confirm clinical significance. Long-term follow-up data are essential to better understand the success and clinical impact of bioceramic sealers and other emerging materials. Additionally, further research is needed to develop efficient retreatment protocols for bioceramic-based fillings to address their limitations in re-intervention scenarios. Incorporating patient-reported outcomes (PROs) and tooth survival rates could provide a more comprehensive understanding of the effectiveness of RCTs and re-RCTs.

Conclusion

Within the limits of this secondary study, root canal filling techniques and materials demonstrated comparable clinical and radiographic success in short-term follow-ups. Some intermediate-term differences were observed, but outcomes converged beyond 3 years. Operator expertise, case selection, and patient-specific factors appear more influential than the obturation technique itself. Bioceramic sealers have not consistently demonstrated long-term clinical advantage over AH Plus, with most evidence limited to in vitro or short-term studies, and challenges in retreatment remain. Given the low to very low certainty of evidence, these findings should be interpreted with caution, understanding the need for well-designed long-term randomized controlled trials with standardized protocols to strengthen evidence-based guidance in endodontic therapy.