Facial soft-tissue analysis in undergraduate dental education: comparison of 2D photographs and images derived from 3D facial scans

Two-dimensional (2D) photographs are routinely used for teaching facial soft-tissue analysis, whereas three-dimensional (3D) facial scans are increasingly used in clinical orthodontics. This prospective educational study evaluated diagnostic agreement when dental students assessed standardized orthodontic soft-tissue parameters using 2D photographs and 3D facial scan-derived images. 93 dental students (7th, 9th, and 10th semesters) performed standardized soft-tissue analyses using 2D photographs, 3D color facial scans, and 3D grayscale facial scans. Paired images from 20 orthodontic patients were presented in standardized printed formats. Assessments were conducted sequentially at three time points one week apart (2D, 3D color, 3D grayscale). A consensus reference standard established by orthodontic experts served as the gold standard. Agreement was assessed using Cohen’s kappa. 67 students completed the 2D assessment, and 50 students completed each 3D assessment. Agreement for objective parameters was highest for 2D photographs and lowest for 3D grayscale images. Compared with 2D images, agreement decreased for most objective parameters with 3D color scans and further decreased for 3D grayscale images. Facial thirds showed a stepwise reduction in agreement across modalities. Profile classification according to A.M. Schwarz showed the highest agreement with 3D color scans. Higher-semester students achieved greater agreement for most objective parameters, whereas agreement for subjective variables was highest for 2D images. Standardized 2D orthodontic soft-tissue analysis can be transferred to facial scan-derived images with limitations. Color facial scans provide more reliable diagnostic conditions than grayscale scans, and diagnostic agreement improves with educational experience, supporting integration of 3D imaging into undergraduate orthodontic training.