Recording Natural Head Position Using Cone Beam Computerized Tomography.

The purpose of this study was to develop a technique to record the natural head position (NHP) of a subject using the scout images of cone beam computerized tomography (CBCT) scans. The first step was to align a hanging mirror with the vertical (XY) plane of the CBCT field-of-view (FOV) volume. Then, two scout CBCT images, at frontal and at sagittal planes, were taken when the subject exhibited a NHP. A normal CBCT scan on the subject was then taken separately. These scout images were used to correct the orientation of the normal CBCT scan. A phantom head was used for validation and performance analysis of the proposed method. It was found that the orientation detection error was within 0.88°. This enables easy and economic NHP recording for CBCT without additional hardware.

Performance and perception of dental students using three intraoral CAD/CAM scanners for full-arch scanning.

PURPOSE: To assess the average full-arch scanning time, perception and likelihood of future adoption of technology by final-year dental students using three different Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) intraoral scanning systems. METHODS: Final-year undergraduate Dental Students (FDS), with no prior experience of intraoral scanning, full-arch scanned (IOS) a mannequin head-mounted model under supervision. Three scanning systems were used, TRIOS Colour (TRIOS); True Definition (TDef); and CEREC AC OmniCam (CEREC). Thereafter, FDS completed a questionnaire to assess their perception of IOS. Data were analysed by Generalized Estimating Equations, Fisher's exact tests and logistic regression. RESULTS: Forty-nine FDS participated. Average full arch IOS time varied significantly (p<0.001) among the TRIOS, CEREC, and TDef, at 4min (n=48), 4min 42s (n=33), and 7min 32s (n=41) respectively. IOS using the TRIOS was significantly (p<0.001) the quickest, while TDef was the slowest (p<0.001). Seventy-one percent of FDS had positive overall IOS experience. FDS who reported intraoral scanning was timesaving compared with conventional impressions were more likely to adopt the technology after graduation (odds ratio (OR)=11.91, 95% confidence interval (CI)=2.56-55.45, p=0.002). CONCLUSIONS: Intraoral scanning performance of novice users varied significantly and was dependent on the scanning system used. The questionnaire showed that the overall IOS experience was positive amongst FDS. The perception of time-saving, when using IOS versus conventional impression methods, determined the likelihood of future adoption of the technology.

Three-dimensional accuracy of implant placement in a computer-assisted navigation system.

PURPOSE: To evaluate the 3-dimensional accuracy of dental implant drilling in a computer-assisted navigation (CAN) system using simulated mandible models. MATERIALS AND METHODS: Eight acrylic resin models were fabricated to simulate human mandibles containing mandibular canal (MC). Computerized tomography (CT) scans were obtained for each model, and the data were transferred to the system for dental implant planning. The models were mounted on a phantom head to simulate surgical situation. The assessment parameters included entry point localization, drill path angulation, and drilling depth, which were directly measured by sectioning of the models. RESULTS: Eighty drill holes were made on the 8 models. The entry point localization showed a mean deviation of 0.43 mm (range, 0 to 2.23 mm; SD, 0.56 mm) from the plan. The angulation showed a mean deviation of 4.0 degrees (range, 0 to 13.6 degrees; SD, 3.5 degrees). The drill aimed at stopping as close to the upper border of the MC as possible without perforating it, and 65% (52) of the drill holes managed to come within 1 mm. Another 5% of the holes stopped 1 to 2 mm above the MC. None of the drill holes stopped more than 2 mm above the MC. However, 30% (24 of 80) of the drill holes perforated the upper border of MC, and the mean depth of perforation was 0.37 mm (range, 0.01 to 1.04 mm; SD, 0.28 mm). DISCUSSION AND CONCLUSION: The CAN system identified the entry location and angulation with mean deviations of 0.43 mm and 4 degrees, respectively. About two thirds of the drillings achieved accuracy within 1 mm above the MC. Thirty percent perforated into the MC, and the maximal depth was 1.04 mm. In the planning stage, the maximal depth of the implant should be at least 1.1 mm above the superior border of MC as a safety margin.