The successful long-term retention of teeth following primary endodontic therapy or replacement with endosseous dental implants represents a cornerstone of modern dentistry. Both modalities have demonstrated high initial success and survival rates, enabling the restoration of function and aesthetics for millions of patients [1,2]. Primary root canal treatment (RCT) has reported survival rates ranging from 86 % to 97 % over eight to ten years, making tooth preservation a highly predictable outcome [3,4]. Similarly, single-tooth implants have shown survival rates often exceeding 95 % over comparable periods, establishing them as a reliable alternative for replacing non-salvageable teeth [5,6]. However, a subset of these initial treatments inevitably fails over time due to a confluence of biological, technical, or patient-related factors [7,8].

The clinical management of a failing root canal-treated tooth or a failing dental implant presents a significant and complex decision-making challenge for both clinicians and patients [9]. This moment represents a critical juncture where the subsequent treatment path can profoundly influence long-term oral health, patient morbidity, and healthcare costs [10]. For a failing endodontically treated tooth, the primary tooth-preserving strategy is nonsurgical root canal retreatment (NSRT). This procedure aims to address the etiological factors of the initial failure, which often involve persistent intraradicular infection, complex or missed anatomy, or coronal leakage, with reported success rates for retreatment varying widely but often falling within the 70–90 % range under optimal conditions [[11], [12], [13]].

Conversely, when a dental implant fails, the treatment philosophy shifts from tooth preservation to a site-salvaging strategy. This pathway involves the surgical removal of the failed implant, which can often result in significant osseous defects requiring subsequent bone grafting procedures to regenerate sufficient architecture for a new implant [14]. The placement of a new implant, or re-implantation, aims to re-establish a stable, osseointegrated foundation for a new prosthesis. While survival rates for initial implants are high, the prognosis for re-implanted fixtures is less certain, with systematic reviews suggesting lower survival rates compared to the first attempt, highlighting the increased clinical challenge and biological compromise of the site [14,15].

A substantial body of literature, including numerous systematic reviews, has directly compared the outcomes of primary endodontic therapy versus initial implant placement [1,9,16]. The consensus from this evidence is that both treatments are highly effective and predictable, with comparable long-term survival rates [17,18]. The decision is therefore considered multifactorial, guided by clinical parameters, patient preferences, potential complications, and economic considerations [10,19]. Both approaches are associated with favorable patient-reported outcomes, including high satisfaction and improved quality of life, further complicating a simple declaration of superiority for either modality [20,21].

Despite the wealth of data on primary treatments, a notable deficit of large-scale, direct comparative effectiveness research on the respective re-treatment modalities exists. Clinical decision-making for these secondary interventions is often guided by extrapolation from primary treatment data, expert opinion, or small, single-center studies, which may be subject to selection bias [22,23]. This evidence gap leaves clinicians and patients without robust, data-driven guidance on the long-term prognosis, survival rates, and risk factors associated with choosing one secondary treatment pathway over the other. This is particularly critical as the populations undergoing these procedures may differ significantly in their baseline health profiles [5].

Furthermore, the outcomes of both endodontic and implant therapies are significantly modulated by patient-specific factors. Systemic comorbidities such as diabetes, behavioral factors like tobacco use, and demographic variables such as advanced age have been consistently identified as negative prognostic indicators that increase the risk of failure for both natural teeth and implants [7,24,25]. A comprehensive understanding of treatment outcomes must therefore account for these potential confounding variables to isolate the true effect of the intervention itself. Any meaningful comparison between endodontic re-treatment and implant re-implantation must adjust for these patient-level characteristics to avoid biased conclusions.

Therefore, the primary objective of this study was to conduct a robust, comparative survival analysis of endodontic re-treatment versus implant re-implantation. Using a large, multi-year, real-world patient cohort derived from electronic dental records, this investigation aims to compare the long-term survival of these two distinct treatment modalities. A secondary objective is to identify patient-specific demographic and systemic health factors that may act as independent predictors of treatment failure, thereby providing a more nuanced understanding of the risk profiles associated with each procedure. By adjusting for a comprehensive set of potential confounding variables, this study seeks to provide evidence-based insights to better inform clinical practice and facilitate shared decision-making for this common and challenging clinical dilemma.