Crown-to-root ratio serves as an important reference indicator for clinical decision-making and diagnosis in dentistry. A favorable crown-to-root ratio can reasonably distribute occlusal stress, reduce the risk of tooth damage and maintain tooth stability. In contrast, an adverse crown-to-root ratio may lead to long-term bone resorption, tooth mobility, root fracture and root resorption. Therefore, crown-root ratio has important reference value in multidisciplinary clinical diagnosis and treatment such as prosthodontics, implantology, orthodontics, periodontics and endodontics. With the emergence and advancement of digital imaging and analytical techniques, the measurement of crown-to-root ratio has shifted from rough two-dimensional estimation to precise three-dimensional quantification, improving the accuracy of diagnosis and treatment. Nevertheless, there is a lack of standardized reference points for crown-to-root ratio measurement, and the applicable scope of two-dimensional and three-dimensional imaging remains ambiguous. It is necessary to clarify the measurement criteria and application scope of crown-to-root ratio. On this basis, this paper summarizes two-dimensional and three-dimensional imaging techniques for crown-to-root ratio measurement, analyzes the application progress and considerations of crown-to-root ratio in different dental disciplines, and puts forward prospects and future research directions, so as to provide evidence-based references for clinical practice.