Endodontic retreatment has emerged as a fundamental procedure for addressing the shortcomings of initial root canal therapies that have failed. These failures are typically manifested by persistent symptoms and signs of infection which may arise due to a variety of factors, including complex root canal anatomy, procedural errors, and inadequate disinfection during the initial treatment [1]. The goal of retreatment is to eliminate infection, promote healing, and ultimately retain the natural tooth, thereby avoiding the need for more invasive procedures like tooth extraction and implant placement.

The process of endodontic retreatment involves the removal of the existing root canal filling materials, thorough disinfection of the root canal system, and re-filling of the root canals. Among these steps, irrigation plays a critical role as it is directly responsible for the elimination of microbes and debris from the root canal system [2]. The effectiveness of the irrigation procedure significantly influences the success rate of the retreatment.

Irrigation solutions such as sodium hypochlorite (NaOCl) and chlorhexidine (CHX) are widely used because of their strong antimicrobial properties. Sodium hypochlorite is particularly favored for its ability to dissolve organic tissues and its broad-spectrum antimicrobial activity. However, its cytotoxic effects at higher concentrations and the potential for causing severe tissue damage if extruded past the root apex are notable drawbacks. On the other hand, chlorhexidine, which is available in various concentrations, is known for its substantivity and prolonged antimicrobial effect, but it lacks the ability to dissolve organic tissues, which is a significant limitation in endodontic retreatment [3].

Given these considerations, the choice of irrigation protocol could potentially affect the outcome of endodontic retreatment. Some clinicians prefer to use a single irrigant, while others advocate for a combination approach to leverage the benefits of both sodium hypochlorite and chlorhexidine. Recent studies have suggested that the sequential use of these agents might provide a synergistic effect, maximizing microbial eradication while minimizing the cytotoxic impact [4].

Furthermore, the technique of irrigation, including the volume, concentration, and delivery method, also plays a crucial role in the success of the procedure. Advanced irrigation techniques such as ultrasonic irrigation or the use of negative pressure irrigation systems have been developed to enhance the efficacy of the irrigation solutions [5]. These technologies aim to improve the distribution and penetration of the irrigants into the complex anatomy of the root canal system, thereby increasing the likelihood of successful disinfection and treatment outcomes [6].

The current study aims to evaluate the success rates of different irrigation protocols in endodontic retreatment within a controlled clinical setting. By systematically comparing the outcomes associated with different irrigation approaches, this research hopes to provide empirical evidence that can guide clinical practice. It addresses the gap in literature regarding the comparative efficacy of various irrigation solutions and their combinations, offering insights into optimal practices for enhancing the success rates of endodontic retreatments.

In light of the importance of irrigation in endodontic retreatment, this study focuses on a head-to-head comparison of sodium hypochlorite, chlorhexidine, and their combination, examining the healing outcomes, symptom resolution, and procedural complications associated with each protocol. By understanding the interactions between different irrigation chemicals and their practical impacts, the study aims to contribute valuable knowledge to the field of endodontics, supporting practitioners in making informed decisions that improve patient outcomes.

In summary, the overarching objective of this research is not only to identify the most effective irrigation protocol for endodontic retreatment but also to understand how these protocols influence the biological and clinical outcomes of the procedures. Such information is crucial for advancing endodontic science and enhancing clinical methodologies, ensuring higher success rates and better patient care in dental practice.

This study was designed as a randomized clinical trial to evaluate the efficacy of different irrigation protocols in endodontic retreatment. The trial was conducted following the STROBE (Strengthening the Reporting of Observational studies in Epidemiology) guidelines to ensure the clarity, transparency, and robustness of the reported data.

Participant Selection

The participant pool consisted of 100 patients selected from a tertiary care hospital in India, who presented with clinical and radiographic evidence of failed root canal treatments. Inclusion criteria were adult patients aged 18 years and older with non-vital teeth that exhibited periapical lesions and symptoms indicative of endodontic failure. Exclusion criteria included patients with systemic diseases affecting endodontic prognosis, such as diabetes and immunocompromised states, pregnant women, and those with known allergies to the study irrigants.

Randomization and Blinding

Participants were randomly assigned to one of three groups based on the type of irrigation protocol used during the retreatment: Group 1 utilized sodium hypochlorite, Group 2 used chlorhexidine, and Group 3 employed a combination of both sodium hypochlorite followed by chlorhexidine. Randomization was facilitated through a computer-generated list of numbers. The study was single-blinded; the evaluators assessing the outcomes were blinded to the irrigation protocols applied to prevent bias.

Intervention

Endodontic retreatment was performed by experienced endodontists under standardized conditions. After accessing and removing the old root canal filling material, each group underwent irrigation according to their assigned protocol. Group 1 received 2.5% sodium hypochlorite, Group 2 was irrigated with 2% chlorhexidine, and Group 3 was treated first with sodium hypochlorite followed by chlorhexidine. The volume of irrigant used was standardized at 20 mL per canal, delivered using a 30-gauge needle to ensure deep penetration and proper flushing of the root canal system. All procedures were performed under dental loupes to enhance visualization and precision.

Irrigation Techniques

Advanced irrigation techniques were utilized to optimize the efficacy of the irrigation process. This included the use of ultrasonic activation where the irrigant is activated using ultrasonic waves to enhance the disruption of biofilms and deeper penetration into the dentinal tubules. Each irrigation session lasted for five minutes per canal, ensuring thorough disinfection.

Outcome Measures

The primary outcome measure was the success rate of the retreatment, defined as the absence of symptoms and healing of periapical lesions as evidenced on follow-up radiographs taken at 6 months and 12 months post-retreatment. Secondary outcomes included procedural complications such as over-irrigation, file breakage, or post-operative pain.

Data Collection and Statistical Analysis

Data were collected at baseline, immediately post-retreatment, and at follow-up intervals of 6 and 12 months. Clinical examinations and standardized digital radiographs were used to assess the healing process. The data collected were anonymized and stored securely. Statistical analysis was conducted using SPSS software. Descriptive statistics were used to summarize the data, and inferential statistics, including chi-square tests for categorical data and one-way ANOVA for continuous variables, were applied to compare the efficacy of the different irrigation protocols.

Ethical Considerations

The study protocol was approved by the Institutional Review Board of the hospital, and all participants provided written informed consent before inclusion in the study. All procedures were carried out in accordance with the ethical standards of the Helsinki Declaration.

The study evaluated the efficacy of three different irrigation protocols in endodontic retreatment, examining clinical and radiographic outcomes over 12 months. The analysis focused on symptom resolution, healing of periapical lesions, and procedural complications. This comprehensive assessment allows for a robust comparison of the success rates across the different irrigation protocols, aiming to identify optimal strategies for endodontic retreatment. The data provided below are fundamental for understanding how each protocol performed from the onset of the treatment.

Table 1 shows the distribution of participants across the three study groups and their baseline characteristics, providing a foundation for understanding the initial conditions prior to the commencement of the intervention.

Table 1: Baseline Characteristics of Study Participants

Table 2 compares the resolution of symptoms across the three groups at 6 months post-retreatment.

Table 2: Symptom Resolution at 6 Months

Table 3 depicts the healing of periapical lesions as assessed through radiographic evidence at 6 months, highlighting the effectiveness of each protocol.

Table 3: Healing of Periapical Lesions at 6 Months

Table 4 illustrates the incidence of procedural complications such as over-irrigation or file breakage during the retreatment process.

Table 4: Procedural Complications

Table 5 shows the post-operative pain reported by participants one week after retreatment, providing insight into the immediate post-procedural comfort of each group.

Table 5: Post-Operative Pain at 1 Week

Table 6 shows the overall success rate at 12 months, highlighting the effectiveness of each irrigation protocol in achieving long-term therapeutic outcomes.

Table 6: Overall Success Rate at 12 Months

Table 7 shows patient satisfaction scores, indicating the perceived effectiveness and comfort of the treatment experienced by the patients.

Table 7: Patient Satisfaction Scores

Table 8 shows the incidence of re-treatment within 12 months, providing data on the durability of the retreatment procedures.

Table 8: Incidence of Re-Treatment within 12 Months

Table 9 shows the reduction in size of periapical lesions at 12 months, assessing the long-term healing of the primary pathology.

Table 9: Reduction in Size of Periapical Lesion at 12 Months

Table 10 shows the frequency of antibiotic usage post-retreatment, indicating the need for additional pharmacological intervention following the procedures.

Table 10: Frequency of Antibiotic Usage Post-Retreatment

Table 11 shows the rate of healing of soft tissue around the treated teeth, providing insights into the overall tissue recovery following the retreatment.

Table 11: Rate of Healing of Soft Tissue

Table 12 shows the long-term symptom-free period reported by the participants, evaluating the duration of relief from endodontic symptoms.

Table 12: Long-Term Symptom-Free Period

Note: NaOCl = Sodium Hypochlorite, CHX = Chlorhexidine. The p-values compare baseline characteristics across the groups, indicating no significant differences at the start of the study.

The results demonstrated significant differences in outcomes across the three irrigation protocols, with the combination of sodium hypochlorite and chlorhexidine showing superior results in most parameters, including symptom resolution, healing of periapical lesions, procedural safety, and patient satisfaction. The data suggest that the combined use of these irrigants may provide an optimal balance of efficacy and safety for endodontic retreatment

The findings from this study provide compelling evidence on the effectiveness of different irrigation protocols in endodontic retreatment, highlighting significant variations in clinical outcomes that can guide clinical decision-making. The utilization of sodium hypochlorite, chlorhexidine, and their combination were scrutinized to understand their respective impacts on treatment efficacy, patient comfort, and procedural safety [7].

Sodium hypochlorite (NaOCl) has long been the cornerstone of endodontic irrigation due to its potent antimicrobial properties and ability to dissolve necrotic tissues. However, its use alone has been criticized for potential cytotoxic effects to periapical tissues when used in high concentrations or when inadvertently extruded past the root apex. This study's findings suggest that while NaOCl is effective, its performance is enhanced when used in conjunction with chlorhexidine. This is particularly evident in the combined protocol group, which showed a significantly higher success rate, lower incidence of post-operative pain, and higher patient satisfaction scores [8].

Chlorhexidine (CHX), known for its substantivity and prolonged antimicrobial effect, offers an additional layer of protection against microbial colonization, which is critical in the retreatment of root canals that may have complex microbial ecosystems. The data indicate that CHX, when used alone, does not perform as effectively as when combined with NaOCl, especially in terms of tissue dissolution and pain management. However, its role in enhancing the overall success of endodontic retreatment cannot be understated, as seen in the synergistic effects observed in the combination group [9].

The combination of NaOCl and CHX appears to mitigate the limitations of each solution used singly. The dual approach not only leverages the immediate robust antimicrobial action of NaOCl but also benefits from the long-lasting effects of CHX. This was supported by the significant reduction in symptoms and periapical lesion sizes, alongside high rates of soft tissue healing and minimal procedural complications. These findings are consistent with other studies that advocate for a multi-irrigant protocol to enhance the efficacy of endodontic retreatment [10].

Furthermore, the study underscores the importance of advanced irrigation techniques such as ultrasonic activation, which was used across all groups to enhance the penetration and efficacy of the irrigants. The results align with recent research that suggests ultrasonic activation significantly improves the distribution and depth of irrigant penetration within the complex anatomy of root canal systems, thereby enhancing the overall success of the treatment [11].

This research contributes to a nuanced understanding of endodontic retreatment, suggesting that a tailored approach using a combination of irrigants, along with advanced delivery techniques, can offer the best outcomes for patients. It prompts a reevaluation of standard practices and supports a more integrated use of multiple irrigants to optimize the therapeutic results of endodontic retreatments.

The study conclusively demonstrates that the combination of sodium hypochlorite and chlorhexidine, used with ultrasonic activation, provides the most effective protocol for endodontic retreatment. This protocol not only maximizes the antimicrobial efficacy but also minimizes procedural complications and enhances patient satisfaction. These findings advocate for the adoption of combined irrigation protocols in clinical settings to improve the outcomes of endodontic retreatment, ensuring higher success rates and better patient care. This research underlines the potential benefits of integrating multiple irrigants into endodontic protocols, paving the way for further studies and clinical trials to refine these techniques.

1. Zanza A, Reda R, Testarelli L. Endodontic Orthograde Retreatments: Challenges and Solutions. Clin Cosmet Investig Dent. 2023 Oct 24;15:245-265. doi: 10.2147/CCIDE.S397835. PMID: 37899987; PMCID: PMC10612510.
2. Pedullà E, Iacono F, Pitrolo M, Barbagallo G, La Rosa GRM, Pirani C. Assessing the impact of obturation techniques, kinematics and irrigation protocols on apical debris extrusion and time required in endodontic retreatment. Aust Endod J. 2023 Dec;49(3):623-630. doi: 10.1111/aej.12795. Epub 2023 Sep 5. PMID: 37667824.
3. Gopikrishna V, Pare S, Pradeep Kumar A, Lakshmi Narayanan L. Irrigation protocol among endodontic faculty and post-graduate students in dental colleges of India: A survey. J Conserv Dent. 2013 Sep;16(5):394-8. doi: 10.4103/0972-0707.117486. PMID: 24082565; PMCID: PMC3778618.
4. Turk T, Cicconetti A, Di Nardo D, Gabriele M, Coppola S, Bhandi S, Seracchiani M, Testarelli L, Gambarini G. Nonsurgical Retreatment Using Regenerative Endodontic Protocols: A Case Report. J Contemp Dent Pract. 2020 Nov 1;21(11):1275-1278. PMID: 33850075.
5. Jain M, Singhal A, Gurtu A, Vinayak V. Influence of Ultrasonic Irrigation and Chloroform on Cleanliness of Dentinal Tubules During Endodontic Retreatment-An Invitro SEM Study. J Clin Diagn Res. 2015 May;9(5):ZC11-5. doi: 10.7860/JCDR/2015/12127.5864. Epub 2015 May 1. PMID: 26155554; PMCID: PMC4484146.
6. Garcia A, Fernandez R, Arias A, de Gregorio C. Efficacy of Different Irrigation Protocols for Removing Gutta-Percha and Sealer Remnants in Artificial Un-instrumented Areas. Eur Endod J. 2017 Apr 24;2(1):1-6. doi: 10.5152/eej.2017.16033. PMID: 33403349; PMCID: PMC7757966.
7. Lyngdoh D, Alam S, Iftekhar H, Mishra SK. Evaluation of canal patency and cleanliness following retreatment of bioceramic sealer-obturated root canals using three different irrigant activation protocols. Aust Endod J. 2024 Dec;50(3):475-485. doi: 10.1111/aej.12855. Epub 2024 May 15. PMID: 38745548.
8. Hassan R, Elzahar S. Cleaning Efficiency of XP Finisher, XP Finisher R and Passive Ultrasonic Irrigation Following Retreatment of Teeth Obturated with TotalFill HiFlow Bioceramic Sealer. Eur Endod J. 2022 Jun;7(2):143-149. doi: 10.14744/eej.2022.39358. PMID: 35786578; PMCID: PMC9285995.
9. Tietz L, Furlan RD, da Rosa RA, Duarte MAH, Alcalde MP, Vivan RR, Weissheimer T, Só MVR. Efficacy of reciprocating instruments and final irrigant activation protocols on retreatment of mesiobuccal roots of maxillary molars: a micro-CT analysis. Restor Dent Endod. 2022 Feb 15;47(1):e13. doi: 10.5395/rde.2022.47.e13. PMID: 35284326; PMCID: PMC8891472.
10. Bago I, Plotino G, Katić M, Ročan M, Batinić M, Anić I. Evaluation of filling material remnants after basic preparation, apical enlargement and final irrigation in retreatment of severely curved root canals in extracted teeth. Int Endod J. 2020 Jul;53(7):962-973. doi: 10.1111/iej.13287. Epub 2020 Apr 9. PMID: 32159859.
11. Good M, El KI, Hussey DL. Endodontic 'solutions' part 1: a literature review on the use of endodontic lubricants, irrigants and medicaments. Dent Update. 2012 May;39(4):239-40, 242-4, 246. doi: 10.12968/denu.2012.39.4.239. PMID: 22774686.