The midpalatal suture, as an important connection between the palatine processes of maxilla, is not only a key component of the hard palate, but also closely related to the efficacy of orthodontic expansion. For patients with maxillary transverse deficiency, accurately evaluating the optimal period of midpalatal suture maturity is a decisive factor for the success of maxillary transverse expansion treatment. Currently, the evaluation of midpalatal suture status is mostly qualitative, while measuring the midpalatal suture density ratio has become a new quantitative method to evaluate midpalatal suture maturity. This review synthesizes the current literature on midpalatal suture bone density in oral field, aiming to provide evidence-based guidance for orthodontic clinicians.