A Study on the Calculation of Root Surface Area and the Evaluation of Anchorage Value Employing CT Images

Abstract

To investigate the value of anchorage in orthodontic tooth movement, we proposed the calculation method of the root surface area based on a CT image. The accuracy of this method was examined with extracted material. The root surface areas in 21 subjects were also determined from stored CT data. The ratio of area among posterior anchorage teeth and anterior teeth (incisors and canine) were calculated as a simulation of clinical tooth movement with a conventional edgewise technique. From the results, the differences between the measurements of extracted material with a high-speed three-dimensional surface detector and calculation from a 2 mm thick scanning image were demonstrated within 3%. Significant differences were found in each root surface area of all subjects. Both ratios of incisors/molars and canine/molars indicated large variations. These results suggested that the information about root surface area in individual patients gave valuable anchorage control and led to the achievement of proper tooth movement.