Why are study models still made when 3D scans exist? Plaster (or printed) models let the orthodontist physically measure arch widths, tooth sizes and bite relationships, mark planned tooth movements, and show the patient the problem tangibly. Scans do this digitally too — but the teaching point is the purpose, not the medium: accurate 3D records of the dentition before treatment, for diagnosis, appliance design and later comparison. The record's job outlives its material.