Post-treatment apical periodontitis is commonly associated with persistent intracanal infection following root canal treatment. Effective disinfection of the complex root canal system during nonsurgical retreatment remains challenging due to anatomical complexities that may harbor microbial biofilms. Conventional retreatment protocols typically involve nickel-titanium rotary instrumentation combined with irrigation using sodium hypochlorite and activation techniques such as Passive Ultrasonic Irrigation (PUI).
The GentleWave System (GWS) is a minimally invasive irrigation technology designed to enhance tissue dissolution and microbial removal through multisonic energy, advanced fluid dynamics, and negative pressure. Although preliminary studies suggest promising results in root canal disinfection and patient outcomes, high-level clinical evidence comparing GWS with conventional retreatment techniques remains limited, particularly in molar teeth with post-treatment apical periodontitis.
This randomized clinical study aims to compare the disinfection efficacy of GWS with a conventional nickel-titanium rotary instrumentation protocol combined with PUI in nonsurgical retreatment of molars with post-treatment apical periodontitis. Intracanal bacterial load will be quantified using quantitative polymerase chain reaction (qPCR), and microbial composition will be analyzed using next-generation sequencing (NGS). Residual organic debris will be evaluated using the chairside diagnostic device Endocator and facultative bacterial culturing. Postoperative pain levels will also be recorded to assess short-term clinical outcomes.
The results of this study will provide clinical evidence regarding the comparative effectiveness, safety, and potential advantages of advanced irrigation technology for root canal disinfection in complex retreatment cases.
Molars showing radiographic evidence of post-treatment apical periodontitis: a lesion that exceeds 3 mm in diameter on one or more roots.
Evidence from periapical and CBCT examination suggests that retreatment is a viable option, i.e., there are low risks of vertical root fracture, no major root canal obstruction, evidence of coronal leakage, and potential improvement on the previous treatment.
The initial root canal therapy was performed at least 2 years previously, or more than 1 year if the patient has signs and symptoms or symptomatic disease (pain, swelling, or sinus tracts).
Patients show no chronic systemic disease that may influence the outcome of care, such as uncontrolled diabetes, autoimmune disease, malignancy treated with chemotherapy or patients who are on immunosuppressive medications or require antibiotic prophylaxis before dental treatment.
Patients with a tooth requiring RCT retreatment that also presents with periodontal pocket(s) deeper than 5mm
Patients with a tooth requiring RCT retreatment that also presents with severe crown destruction that would prevent proper rubber dam isolation or an adequate restoration
Patients with a tooth requiring RCT retreatment that also presents with evidence of vertical root fracture, or cracks with probing defects > 5 mm
Patients with a tooth requiring RCT retreatment that is deemed unrestorable
Parallel
GentleWave System
Procedure/SurgeryMinimally invasive root canal disinfection using the GentleWave multisonic irrigation system following minimal instrumentation. The system delivers multisonically activated sodium hypochlorite and EDTA solutions under negative pressure to enhance irrigation dynamics and debris removal within the root canal system during nonsurgical endodontic retreatment.
Conventional rotary instrumentation with passive ultrasonic irrigation
Procedure/SurgeryConventional nonsurgical endodontic retreatment using nickel-titanium rotary instrumentation followed by passive ultrasonic irrigation (PUI). Irrigation is performed using sodium hypochlorite delivered via a side-vented needle and ultrasonically activated irrigation to enhance canal disinfection after mechanical preparation.
change of the intracanal Bacterial Load
Change in total bacterial load in the root canal system following disinfection, measured by quantitative real-time polymerase chain reaction (qPCR) targeting the universal 16S rRNA gene. Bacterial load will be quantified from microbiological samples collected before instrumentation (S1) and after completion of the disinfection protocol (S2) to determine the reduction in bacterial load between the two time points.
Root Canal Microbiome Composition
Differences in the prevalence and relative abundance of bacterial taxa in root canal samples before and after disinfection, assessed using next-generation sequencing (NGS) of bacterial 16S rRNA gene amplicons. Alpha diversity and beta diversity metrics will be analyzed to compare microbial community structure between treatment groups.
change of the Residual Intracanal Organic Debris Score
Residual organic debris within the root canal system will be measured using the chairside device Endocator. The device provides a quantitative Endoscore representing the level of intracanal bioburden. Scores will be recorded before instrumentation and after completion of the disinfection protocol to assess debris reduction. Endoscore values will be categorized as follows: (1) 1-25: Low Bioburden; (2) 26-50: Medium Bioburden; (3) 51-100: High Bioburden, as instructed by the device protocol.
Post-operative Pain
Patient-reported post-operative pain intensity measured using a numerical rating scale from 0 (no pain) to 10 (worst imaginable pain). Participants will record their pain levels following the treatment procedure using a post-treatment pain diary.
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