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BackgroundTwo-dimensional projection radiographs have been traditionally considered the modality of choice for cephalometric analysis. To overcome the shortcomings of two-dimensional images, three-dimensional computed tomography (CT) has been used to evaluate craniofacial structures. However, manual landmark detection depends on medical expertise, and the process is time-consuming. The present study was designed to produce software capable of automated localization of craniofacial landmarks on cone beam (CB) CT images based on image registration and to evaluate its accuracy.MethodsThe software was designed using MATLAB programming language. The technique was a combination of feature-based (principal axes registration) and voxel similarity-based methods for image registration. A total of 8 CBCT images were selected as our reference images for creating a head atlas. Then, 20 CBCT images were randomly selected as the test images for evaluating the method. Three experts twice located 14 landmarks in all 28 CBCT images during two examinations set 6 weeks apart. The differences in the distances of coordinates of each landmark on each image between manual and automated detection methods were calculated and reported as mean errors.ResultsThe combined intraclass correlation coefficient for intraobserver reliability was 0.89 and for interobserver reliability 0.87 (95% confidence interval, 0.82 to 0.93). The mean errors of all 14 landmarks were <4 mm. Additionally, 63.57% of landmarks had a mean error of <3 mm compared with manual detection (gold standard method).ConclusionThe accuracy of our approach for automated localization of craniofacial landmarks, which was based on combining feature-based and voxel similarity-based methods for image registration, was acceptable. Nevertheless we recommend repetition of this study using other techniques, such as intensity-based methods.

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BackgroundMost orthodontists believe that fixed retainers are necessary to maintain ideal dental relationships. However, untoward side effects might result from their long-term placement. The aim of this study was to evaluate the clinical and radiographic effect of two commonly used fixed retainers on the health of the periodontium.MethodsThirty patients were randomly divided into two groups to receive either a fiber-reinforced composite retainer or a spiral wire retainer extended on the lingual surfaces of both maxillary and mandibular arches from canine to canine. Periapical radiographs were obtained from the patients at the time of placement of the retainers and after the 6-month period to assess the radiographic conditions of the periodontium. Clinical examination was carried out at the same two time intervals.ResultsEven though there were no significant differences between the two groups of study at the beginning of the trial, there were statistically significant differences after the 6-month follow-up regarding the main outcomes of the study. Nearly all indices showed to deteriorate after 6 months in the fiber-reinforced group, while in the spiral wire group, this was not the case. As for the secondary outcomes, radiographic examination did not reveal any statistically significant differences after 6 months or between the two groups.ConclusionsIt can be concluded that spiral wire retainers elicit less detrimental periodontal response in the short-term follow-up compared to fiber-reinforced composite retainers as revealed by the primary outcomes of the study.Trial registrationClinicalTrials.gov: NCT01314729Electronic supplementary materialThe online version of this article (doi:10.1186/s40510-014-0047-8) contains supplementary material, which is available to authorized users.

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.