© 2021 The Authors. Journal of Oral Rehabilitation published by John Wiley & Sons Ltd.Background: The Tooth Wear Evaluation System (TWES) is a type of tooth wear index. To date, there is the lack of data comparing the reliability of the application of this index on gypsum cast records and digital greyscale intra-oral scan records. Objectives: A comparative evaluation between the use of gypsum cast records and digital greyscale intra-oral scan records with the reliability of tooth wear scoring using the TWES amongst a group of patients with tooth wear. Methods: Records for 10 patients with moderate to severe tooth wear (TWES ≥ 2) were randomly selected from a larger clinical trial. TWES grading of the occlusal/incisal, buccal and palatal/lingual surfaces was performed to determine the levels of intra- and interobserver agreement. Intra-observer reproducibility was based on the findings of one examiner only. For the interobserver reproducibility, the findings of two examiners were considered. One set of models/ records were used per patient. Cohen's weighted kappa (κW) was used to ascertain agreement between and within the observers. Comparison of agreement was performed using t tests (P <.05). Results: For the scoring of the of the total occlusal/incisal surfaces, the overall levels of intra- and interobserver agreement were significantly higher using the gypsum cast records than with the digital greyscale intra-oral scan records, (P <.001) and (P <.001), respectively. For the overall buccal surfaces, only a significant difference was found in the intra-observer agreement using gypsum casts, (P =.013). For the palatal/lingual surfaces, a significant difference was only reported in the interobserver agreement using gypsum casts, (P =.043). At the occlusal/incisal surfaces, grading performed using gypsum casts, culminated in significantly higher TWES scores than with the use of the digital greyscale intra-oral scans (P <.001). At the buccal and palatal/lingual surfaces, significantly higher wear scores were obtained using digital greyscale intra-oral scan records (P <.009). Conclusions: The TWES can offer a reliable means for the scoring of wearing occlusal/incisal surfaces using gypsum casts. The reliability offered by digital greyscale intra-oral scans for consecutive scoring was in general, inferior.