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Objectives: The purpose of this study was to design software for localization of cephalometric landmarks and to evaluate its accuracy in finding landmarks. Methods: 40 digital cephalometric radiographs were randomly selected. 16 landmarks which were important in most cephalometric analyses were chosen to be identified. Three expert orthodontists manually identified landmarks twice. The mean of two measurements of each landmark was defined as the baseline landmark. The computer was then able to compare the automatic system's estimate of a landmark with the baseline landmark. The software was designed using Delphi and Matlab programming languages. The techniques were template matching, edge enhancement and some accessory techniques. Results: The total mean error between manually identified and automatically identified landmarks was 2.59 mm. 12.5% of landmarks had mean errors less than 1 mm. 43.75% of landmarks had mean errors less than 2 mm. The mean errors of all landmarks except the anterior nasal spine were less than 4 mm. Conclusions: This software had significant accuracy for localization of cephalometric landmarks and could be used in future applications. It seems that the accuracy obtained with the software which was developed in this study is better than previous automated systems that have used model-based and knowledge-based approaches.

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BackgroundThe ideal built-in tip and torque values of the straight wire appliance reduce the need for wire bending and hence reduce chair time. The vertical position of the bracket on the tooth surface can alter the torque exerted on the tooth. This is a result of the altered surface curvature observed at each vertical position. To further clarify the role of vertical bracket positioning on the applied torque and the resultant stresses in the periodontal ligament (PDL), we designed a mandibular first premolar using finite element modeling.MethodsCone beam computed tomography of 52 patients (83 lower first premolars) was selected to be included in the study. Curvature was measured for points along the labial surface with increasing distances (0.5 mm increments) from the cusp tip by calculating the angle between tangents drawn from these points and the axis joining the cusp tip and the root apex. The mean values for each distance were calculated, and a finite element model was designed incorporating these mean values. The resultant stress and hydrostatic pressure in the PDL were calculated using finite element analysis.ResultsThe labial surface of the mandibular first premolar demonstrated a 26.39° change from 2.5 to 6 mm from the cusp tip. The maximum Von-Mises stress and hydrostatic pressure in the PDL were observed at the root apex for all of the bracket positions, and these values demonstrated, respectively, a change of up to 0.059 and 0.186 MPa between two successive points.ConclusionsIt can be concluded that the variation in the vertical position of the bracket can have an important effect on the torque and subsequently on the stresses and pressures in the PDL.