[ comparison of tomography's accuracy between spiral cranex tome and linear promax for evaluating the quantity of bone in posterior of maxilla]

An accurate imaging technique has an important role in implantology. Presence of sinus in the posterior maxilla is a limiting factor for implant insertion in this area. Therefore it is necessary to evaluate the relationship between alveolar ridge and sinus. The aim of the present in vitro study was to compare the accuracy of Cranex Tome Spiral and ProMax linear tomography to assess bone quality for the preoperative planning of implants in the posterior maxilla. Tomographs were taken from 3 dry human skulls using both units. Three sites were selected in each side of posterior maxilla and marked with orthodontic wires meaning a total of 24 sites [12 sites for each unit]. Bone height and width were measured first on the tomography and then on the skulls after sectioning. In order to compare the measurement values between both units and to compare them with the values obtained from gold the Intraclass Correlation of reliability [ICC] was used. The minimum Intraclass correlation coefficient of reliability was 0.569 in two times measurements of width for ProMax, and the maximum of this coefficient was 0.950 in two times measurements of height for Spiral. The mean difference between the real measurements and the height measurements of both units were less than 0.3 mm and for the width measurements were less than 0.5 mm of the real measurements. This study showed in both units, the height measurements were more accurate than the width measurements and all the measurements by Spiral were more valid then those of ProMax. Generally quantitative accuracy of Spiral unit was found to be higher than ProMax unit. Both units proved to be sufficient for quantity measurements. Adjustment an individual imaging plane for each site of tomography increases the accuracy. The most distal sites of Spiral unit may need separate adjustment other than manufacturer demands

Development and evaluation of a software for automatic locating of cephalometric landmarks

The cephalometric analysis should be done for patients seeking orthognathic surgical treatments to diagnose dentoalveolar relationships properly. Finding a landmark for the analysis must be time consuming and depends on individual experience or errors and further needs more training. The aim of this study was to develop and evaluate a software for automatically locating of the cephalometric landmarks. A software was designed and developed by programmers group using 140 cephalometric radiographs as databases. Further to cephalograms were grabbed by a digital camera [Sony cybershot 1000X1200] in JPEG format and displayed on LCD monitor [Toshiba, 1600X1200 UXGA] for three expert orthodontists and asked them to locate 10 landmarks. The statistic analysis was based on Paired t test. The results showed 51% of the assigned points by software locating were within 1mm accuracy, 63% within 2 mm and 92% within 4mm accuracy. The mean distance from reference [the mean distance of three observers'points] of seven out often points was less than maximum difference between observers. For B point the mean distance difference in computer locating [0.4mm] was less than mean distance observers' points [3.1mm]. For S point the mean distance difference from reference point was 3.4mm in computer locating which was greater than the mean distance difference between observers [0.6mm]. The study showed that landmark locating errors by computer were not greater than errors of individuals so, perhaps, computer could be a proper substitute for individuals for locating and analysis of cephalometric landmarks