In-vitro study on the accuracy of a simple-design CT-guided stent for dental implants

PURPOSE: An individual surgical stent fabricated from computed tomography (CT) data, called a CT-guided stent, would be useful for accurate installation of implants. The purpose of the present study was to introduce a newly developed CT-guided stent with a simple design and evaluate the accuracy of the stent placement. MATERIALS AND METHODS: A resin template was fabricated from a hog mandible and a specially designed plastic plate, with 4 metal balls inserted in it for radiographic recognition, was attached to the occlusal surface of the template. With the surgical stent applied, CT images were taken, and virtual implants were placed using software. The spatial positions of the virtually positioned implants were acquired and implant guiding holes were drilled into the surgical stent using a specially designed 5-axis drilling machine. The surgical stent was placed on the mandible and CT images were taken again. The discrepancy between the central axis of the drilled holes on the second CT images and the virtually installed implants on the first CT images was evaluated. RESULTS: The deviation of the entry point and angulation of the central axis in the reference plane were 0.47+/-0.27 mm, 0.57+/-0.23 mm, and 0.64+/-0.16degrees, 0.57+/-0.15degrees, respectively. However, for the two different angulations in each group, the 20degrees angulation showed a greater error in the deviation of the entry point than did the 10degrees angulation. CONCLUSION: The CT-guided template proposed in this study was highly accurate. It could replace existing implant guide systems to reduce costs and effort.

A comparative study on the accuracy of digital subtraction radiography according to the aquisition methods of reconstructed images / 대한구강악안면방사선학회지

PURPOSE: To compare the accuracy of digital subtraction images acquired by two different methods different in positioning four reference points for geometrical standardization. MATERIALS AND METHODS: A total of 36 digital radiographic images of 6 volunteers were taken at the areas of the incisor, premolar, and molar of both the maxilla and mandible using the Digora system. Each image was moved 4 mm vertically and horizontally. Four oral and maxillofacial radiologists performed digital subtraction radiography between the paired images before and after movement using Emago (Oral Diagnostic Systems, Amsterdam, The Netherlands) and Sunny (Biomedisys Co., Seoul, Korea). The standard deviation of the internal gray value in Region of Interest (ROI) was statistically analyzed between the two programs using the paired t-test. RESULTS: The standard deviation of pixel gray values from the digital subtraction images using the Sunny program were lower than that of the Emago program (p<0.05). All observers showed significant differences between each other when the Sunny program was used (p<0.05), but one observer showed a significantly higher score than other observers when they used Emago (p<0.05). The standard deviations of premolar area from both Sunny and Emago programs were significantly higher than those of anterior and molar regions (p<0.05). CONCLUSION: The subtracted images using the Sunny program were more accurate and sensitive than those taken using the Emago program.