Percorrer por autor "Lopes, Carla"
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- Assessment of fat mass and fat-free mass in Portuguese adults: calibration of single-frequency leg-to-leg bioelectrical impedance with dual-energy x-ray absorptiometryPublication . Farias, Fernanda; Severo, Milton; Ramos, Elisabete; Lopes, Carla; Nogueira, Luísa; Araújo, Joana; Nogueira, LuisaBioelectrical impedance analysis (BIA) is more commonly employed in outpatient evaluations and epidemiological studies as it is cheaper and less time-consuming. Therefore, we aimed to compare fat mass (FM) and fat-free mass (FFM) estimated by BIA and dual-energy x-ray absorptiometry (DXA) in Portuguese adults, and to calibrate BIA estimates. We analyzed data from two population-based cohorts: EPIPorto (n = 391; <65 y) and EPITeen (n = 973; 27 y). Both completed single-frequency leg-to-leg BIA (Tanita TBF-300) and DXA (QDR 4500A Hologic). Agreement between BIA and DXA (FM/FFM) was evaluated by Bland and Altman. To calibrate the BIA estimates, the coefficients were estimated by linear regression using univariate (FM or FFM, separately) and multivariate models (FM and FFM in the same model). The correlation between BIA and DXA was high for FFM and for FM (FFM: r = 0.946/r = 0.954; FM: r = 0.926/r = 0.921, for EPIPorto and EPITeen, respectively). However, BIA underestimated FM (19.4% EPIPorto; 24.3% EPITeen) and overestimated FFM (11.3% EPIPorto; 14.4% EPITeen). Using the multivariate constrained model to have an absolute equal intercept for FFM and FM, the following calibration equations for BIA measurements were obtained for EPIPorto: FFMcalibrated =-5.119 + 0.995 £ FFMBIA;FMcalibrated = +5.119 + 0.980 £ FMBIA; and for EPITeen: FFMcalibrated =-5.707 + 0.984 £ FFMBIA;FMcalibrated = +5.707 + 0.975 £ FMBIA. FM assessed by single-frequency leg-to-leg BIA was largely underestimated and FFM overestimated in comparison to DXA, suggesting the use of BIA model-specific calibration equations to calibrate FM and FFMestimates in clinical settings and research studies.
- Influence of an innovative dental post approach in dentin mechanical behaviorPublication . Lopes, Carla; Machado, Joana; Almeida, Paulo; Fernandes, Sampaio; Marques, Maria Arcelina; Vaz, MárioThe restoration of seriously damaged teeth often requires an endodontic post. A number of different materials and shapes of dental posts have been manufactured, which leads to different mechanical behaviors. The currently used post systems frequently result in failure or fracture of the tooth, due to the difference between tooth and dentin mechanical properties. Recently, a bundle of fine individual posts made of reinforced fiberglass has been developed. This new approach is not a single-post and it can be spread apart, being individually distributed in the tooth canal. With this configuration, the fine posts can adapt to suit into any root canal anatomy. Biomechanical properties similar to the dentin are being reported as an advantage for the use of this new dental post. The purpose of this study is to understand if the bundle post introduces an improvement in the results of endodontic treatment, compared with the currently used post systems. This study was carried out using the finite element method to determine the influence of stress distribution on dentin, when these two different approaches are used. The results show that stresses at the dentin changed with the dental post used. The use of bundle post appears to better accommodate the developed stress, reducing the stresses in the tooth.
- Mechanical behavior of external fixator on fracture healing processPublication . Lopes, Carla; Flores, Andreia; Marques, Maria Arcelina; Machado, Joana; Marta, Miguel; Vaz, MárioSucceeding a fracture of a long bone, there are multiple approaches to perform the bone fracture immobilization.The external fixation has traditionally been used under clinical indications, and can be a definitive optionin cases where risks of infection are high. The currently used system scannot predict or measure the complete bone consolidation[1, 2]. The purpose of the present study is to understand the phases of healing and to predict functional bone consolidation.This study was carrying out using the finite element analysis (FEA)to determine the influence of stress distribution along the tibia and the rods of the fixator.This information gathered by the present study is relevant to help medical and scientific communities to know the real fracture healing process.