Are We Measuring What Matters? The Surrogate Trap in Endodontics.

Surrogate endpoints have been important to the advancement of endodontic research, enabling the evaluation of treatments, materials and techniques within practical timeframes. However, these measures assess indirect biological or technical processes rather than the outcomes that matter most to patients, including long-term tooth survival, function, freedom from symptoms and oral health-related quality of life. This editorial examines the benefits and limitations of surrogate endpoints in endodontics, arguing that their widespread use reflects not only methodological convenience but also a fundamental inability to directly assess root canal infection and its relationship with healing. Drawing on examples from medicine and contemporary endodontic research, we discuss the distinction between biological plausibility and clinical validation, emphasizing that improvements in technical or laboratory measures do not necessarily translate into better patient outcomes. A conceptual framework is proposed to classify commonly used surrogate measures according to their biological relevance and the strength of their association with clinically meaningful outcomes. We further consider the impact of emerging technologies, including cone beam computed tomography, molecular diagnostics, biomarkers and artificial intelligence, highlighting that these innovations primarily improve the precision of surrogate measurements rather than overcome their inherent limitations. Finally, we advocate for a more patient-centred approach to outcome assessment through the routine integration of patient-reported outcome measures and standardized core outcome sets alongside conventional clinical and radiographic evaluations. Surrogate endpoints should continue to support scientific progress, but their interpretation must remain anchored to outcomes that genuinely reflect treatment success from the patient's perspective.