Effect of Endodontic Treatments on Periodontal Ligament: A Systematic Review

Background: The biological response of the periodontal ligament (PDL) following endodontic treatment remains insufficiently investigated. This systematic review aimed to evaluate the influence of endodontic treatment modalities on PDL-related healing outcomes and periapical tissue repair. Methods: A systematic review was conducted according to PRISMA 2020 guidelines. PubMed, Scopus, Web of Science, and the Cochrane Library were searched for randomized clinical trials published between 2015 and 2025. Studies evaluating the effects of endodontic interventions on clinical, radiographic, or biological outcomes associated with PDL healing. Risk of bias was assessed using the Cochrane RoB 2 tool. Results: Ten randomized clinical trials involving approximately 710 participants were included. Endodontic treatment was generally associated with favorable healing outcomes, reflected by reductions in periapical lesion size, improvement of radiographic parameters, and resolution of clinical symptoms. Single-visit and multiple-visit treatments demonstrated comparable long-term healing outcomes, although single-visit protocols were associated with increased short-term postoperative discomfort. Activated irrigation techniques appeared to enhance healing compared with conventional irrigation methods. Most studies were judged as having some concerns regarding risk of bias. Conclusions: Current evidence suggests that endodontic treatment can promote favorable healing of the periodontal ligament–periapical complex through effective infection control and resolution of inflammation. However, the certainty of evidence remains moderate because of methodological heterogeneity and the limited availability of studies directly assessing biological PDL outcomes. Further well-designed randomized clinical trials with standardized outcome measures and longer follow-up periods are required.