This study aimed to evaluate the relevance of a conventional evaluation protocol (CEP) for preclinical endodontic training. Seven dental students performed root canal treatments on an extracted human molar which was then evaluated by CEP (clinical and radiographic observations, including preparing the access cavities, preparing and filling the root canal, and detecting iatrogenic errors). A reference evaluation protocol (REP) based on micro-computed tomographic images analysis was used as a control. The evaluation scores obtained by CEP and REP were compared using a non-parametric Wilcoxon's test. CEP was relevant for access cavity, irrigation, working length and ledge detection training but was no more effective than the REP for evaluating the apical diameter and taper of the root canals, the quality of the fillings, and the presence of perforations and fractured instruments using retro-alveolar radiographs. The conventional evaluation criteria used in preclinical endodontics should be used with care to detect 'unsafe' students.