Diagnostic accuracy of cone-beam computed tomography scans with high- and low-resolution modes for the detection of root perforations
Purpose This study compared the diagnostic accuracy of cone-beam computed tomography (CBCT) scans obtained with 2 CBCT systems with high- and low-resolution modes for the detection of root perforations in endodontically treated mandibular molars. Materials and Methods The root canals of 72 mandibular molars were cleaned and shaped. Perforations measuring 0.2, 0.3, and 0.4 mm in diameter were created at the furcation area of 48 roots, simulating strip perforations, or on the external surfaces of 48 roots, simulating root perforations. Forty-eight roots remained intact (control group). The roots were filled using gutta-percha (Gapadent, Tianjin, China) and AH26 sealer (Dentsply Maillefer, Ballaigues, Switzerland). The CBCT scans were obtained using the NewTom 3G (QR srl, Verona, Italy) and Cranex 3D (Soredex, Helsinki, Finland) CBCT systems in high- and low-resolution modes, and were evaluated by 2 observers. The chi-square test was used to assess the nominal variables. Results In strip perforations, the accuracies of low- and high-resolution modes were 75% and 83% for NewTom 3G and 67% and 69% for Cranex 3D. In root perforations, the accuracies of low- and high-resolution modes were 79% and 83% for NewTom 3G and was 56% and 73% for Cranex 3D. Conclusion The accuracy of the 2 CBCT systems was different for the detection of strip and root perforations. The Cranex 3D had non-significantly higher accuracy than the NewTom 3G. In both scanners, the high-resolution mode yielded significantly higher accuracy than the low-resolution mode. The diagnostic accuracy of CBCT scans was not affected by the perforation diameter.
Comparing the Diagnostic Accuracy of CBCT Grayscale Values with DXA Values for the Detection of Osteoporosis
Cone beam computed tomography (CBCT) allows for the dimensional evaluation of jaw anatomic structures and the measurement of jawbone mineral density (BMD), to evaluate the relationship between the measured CBCT grayscale (GS) values and (dual X-ray absorptiometry) DXA scores among osteoporotic and normal dental implant participants. In addition, it can help to establish the CBCT GS values in different jaw regions that might indicate or associate osteoporosis. Eighty-one (81) participants (59 females and 22 males) were recruited into this clinical inquiry. Participants’ ages ranged between 36 and 75 years (mean age ± SD: 57.9 ± 9.3 years). The inclusion criteria included patients diagnosed with osteoporosis and were indicated for the dental implant-supported prosthesis.GS values were calculated for each participant using the CBCT radiograph and associated computer software. The average T values obtained from L1, L2, L3 and L4 were recorded and evaluated for one time only, and correlated with CBCT GS values at different jaw positions. Associations between age, gender, GS values, and T values were evaluated by Pearson correlation tests. The GS values at posterior maxilla were able to predict the presence of osteoporosis (P < 0.001, R square = 0.849). On the other hand, attempts to predict T value using GS at different jaw sites showed that GS values at posterior maxilla and anterior mandible were able to predict T value (P < 0.001, R square = 0.924). The CBCT GS values of BMD at different jaw bone regions are significantly related to the DXA T values in the presence of osteoporosis.
Convective Heat Transfers in the Combustion Chamber of an Internal Combustion Engine Influence of In-Cylinder Aerodynamics
Previous studies of in-cylinder heat transfers give numerous approaches of heat losses modelling principally compression and expansion strokes. These simulation methods are discussed showing that their accuracy during the intake stroke is neglected. Since most of the modern engines use strong structured air motion during the intake and compression strokes to both reduce consumption and reach different emissions levels targets, one may focus on in-cylinder aerodynamics and convective heat transfer coupling. The experimental velocity data acquired allow us to get an in-depth understanding of the spatial and temporal gradients of measured heat transfers in the cylinder of an internal combustion engine. Two different experimental methods have been used to investigate the in-cylinder air motion. First, near wall flow has been studied using two component local time-resolved Laser Doppler Anemometry (LDA). Heat transfers are measured by thin-film fast-response heat flux probe constituted of two thermocouples. Velocity and turbulence intensity are analysed by the cycle resolved method. For a global time-resolved analysis of in-cylinder aerodynamics Time Resolved Planar Image Velocimetry (TR-PIV ) fields are analysed. The comparison of the TR-PIV and LDA measurements gives a detailed description of the effect of in cylinder aerodynamics on the near wall flow characteristics. Parametric analysis of the motored optical test-engine conditions effects on heat transfers and flow fields is presented. In parallel to physics understanding, experimental databases built here are then of a great interest to check quality of the different models implemented in CFD software. A first evaluation of a local convection coefficient formula during the intake stroke is then carried out. Thermal experimental data compared to this correlation demonstrate a great underestimation of the simulated coefficient during the intake stroke leading to an underestimation of the heat transfer from the wall to the gas.