Micro-CT evaluation of several glide path techniques and ProTaper Next shaping outcomes in maxillary first molar curved canals.

AIM: To evaluate the ability of ProGlider instruments, PathFiles and K-files to maintain canal anatomy during glide path preparation using X-ray computed micro-tomography (micro-CT). METHODOLOGY: Forty-five extracted maxillary first permanent molars were selected. Mesio-buccal canals were randomly assigned (n = 15) to manual K-file, PathFile or ProGlider groups for glide path preparation. Irrigation was achieved with 5% NaOCl and 10% EDTA. After glide path preparation, each canal was shaped with ProTaper Next X1 and X2 to working length. Specimens were scanned (isotropic voxel size 9.1 µm) for matching volumes and surface areas and post-treatment analyses. Canal volume, surface area, centroid shift, canal geometry variation through ratio of diameter ratios and ratio of cross-sectional areas were assessed in the apical and coronal levels and at the point of maximum canal curvature. One-way factorial anovas were used to evaluate the significance of instrument in the various canal regions. RESULTS: Post-glide path analysis revealed that instrument factor was significant at the apical level for both the ratio of diameter ratios and the ratio of cross-sectional areas (P < 0.001), with an improved maintenance of root canal geometry by ProGlider and PathFile. At the coronal level and point of maximum canal curvature, ProGlider demonstrated a tendency to pre-flare the root canal compared with K-file and PathFile. PathFile and ProGlider demonstrated a significantly lower centroid shift compared with K-file at the apical level (P = 0.023). Post-shaping analysis demonstrated a more centred preparation of ProGlider, compared with PathFile and K-files, with no significant differences for other parameters. CONCLUSIONS: Use of ProGlider instruments led to less canal transportation than PathFiles and K-files.

Effective dose and image quality evaluations of an automatic CT tube current modulation system with an anthropomorphic phantom.

The purpose of this study was to evaluate the consequences of different choices of acquisition parameters on the actual image noise and on the patient dose with an automatic tube current modulation system. The CT investigated was a GE Lightspeed 16-slice and an anthropomorphic phantom was used to simulate the patient. Several acquisitions were made varying noise index (NI), kilovoltage and pitch values. Tube current values were compared for the different acquisitions. Patient dose was evaluated in terms of volumetric computed tomography dose index (CTDI(vol)) and also as effective dose. The noise actually present in the images was analyzed by a region of interest analysis considering representatively phantom sections in the regions of the shoulders, of the lungs and of the abdomen. The obtained results generally evidenced a good agreement between the noise index and the measured noise for the abdomen sections, whereas for the shoulders and the lungs sections the measured noise was respectively greater and lower of the NI. Varying the kV the automatic current modulation system provided images with a substantially constancy of the actual noise and of the patient dose. An increase of the pitch generally decreased the patient dose, whereas the noise was slightly greater for the lowest pitch and almost constant for the other pitch values. This study outlines some important relationships between an automatic tube current modulation system and other CT acquisition parameters, providing useful informations for the choice requested by radiologists in the task of optimization of the CT acquisition protocols. Unless there are other considerations in place, pixel pitches below 1.375 should be avoided, and kVp settings can be changed with no real impact on dose or image noise.

The WEBD project: a research of new methodologies for a distant-learning 3D system prototype.

OBJECTIVES: To create and to spread a new interactive multimedia instrument, based upon virtual reality technologies, that allows both the running simulation of machines and equipment and the reproduction via Web of complex three-dimensional (3D) anatomical models such as the skull. METHODS: There were two main aspects of the project, one of design engineering and the other biomedical engineering, for the creation of "artificial" and anatomical objects. The former were made with 3D Studio Max R4 by Autodesk, San Rafael, CA, while the latter were created starting from real bones scanned with a CT system or a surface scanner and elaborated with different programs (3D Studio Max R4, Scenebuilder by Viewpoint, New York, NY and Spinfire by Actify, San Francisco, CA). The 3D models were to be integrated into web modules and had to respect file limits while preserving a sufficient definition. Two systems of evaluation were used, a questionnaire on a selected sample and an external evaluation by a different university. RESULTS: The Viewpoint format offers the best interactivity and size reduction (up to 96% from the original 3D model). The created modules included production of radiological images, rapid prototyping, and anatomy. The complete "3D Distant Learning Prototype" is available at www.webd.etsii.upm.es. CONCLUSIONS: The software currently available permits the construction of interactive modules. The verification on the selected sample and the evaluation by the University of Naples show that the structure is well organized and that the integration of the 3D models meets the requirements.