Abstract This narrative review explores current methodologies used to assess midpalatal suture maturation in adolescents and young adults, which is essential for determining appropriate maxillary expansion techniques. Despite the historical use of indices such as cervical vertebral maturation and hand–wrist radiographs, no universally accepted, standardized method exists. A literature search revealed studies utilizing various diagnostic tools, including computed tomography and ultrasonography. However, none were validated against histological standards, and methodologies varied widely. The review concludes that while modern imaging shows promise, evidence remains limited. Clinicians should rely on a combination of diagnostic approaches to guide treatment decisions.