As a layer of dense connective tissues attached to the root surface, periodontal ligament performs numerous biological functions, such as supporting dentition and adjusting biting force. The accurate measurement of periodontal ligament area can help dentists perform the prognosis of teeth suffering from periodontitis and establish effective treatment plans for missing teeth. The measurement of root surface area is an alternative method to determine the periodontal ligament area. The root surface area can be measured by using various techniques, such as membrane technique, image segmentation, weight conversion, 3D laser scanning, and CT reconstruction and precision. This article aims to review the development of various methods used to measure root surface area and their advantages, disadvantages, and potential clinical applications.
