Tooth loss and associated factors in long-term institutionalised elderly patients

Objective: To compare partial and total tooth loss in dependent institutionalised elderly patients and identify any associated factors. Background: A poor oral health status, together with a reduction of autonomy can seriously affect the general health and increase the risk of death in elderly people. Those with total tooth loss and in need of assistance are the most at risk. Materials and methods: In 2004, a cross‐sectional study of 321 elderly patients was conducted in long‐term hospital services provided in Montpellier, France. Socio‐demographic, behavioural, medical and oral health information was recorded for each patient. Multivariate logistic regression models were performed to test the relationship between those covariates and partial or total tooth loss. Pearson chi‐squared tests were used for bivariate analyses. Results: The proportion of edentulousness was 26.9%; among these12.6% had no dentures. The factors significantly associated with edentulism were: an age ‘older than 87 years’ [odds ratio (OR) = 9.4], the presence of a nephropathy (OR = 6.8), and inadequate oral hygiene (OR = 0.1). The factors most significantly associated with partial tooth loss (at least 21 missing teeth) were ‘cancerous disease’ (OR = 9.9), the presence of a nephropathy (OR = 5.6) and the presence of a neurological disease (OR = 4.1). The factors significantly related to dentate status (20 or more natural teeth retained) were ‘hypertension treatment’ (OR = 2.4), and ‘cortisone treatment’ (OR = 0.2). Conclusion: General health problems as well as a poor oral condition were significant risk indicators for tooth loss among the long‐term institutionalised elderly. This suggests that the number of remaining teeth has a strong effect on oral health‐related quality of life.     

Quantitative measurement of speech sound distortions with the aid of minimum variance spectral estimation method for dentistry use

In this paper, we search an adequate quantitative method based on minimum variance spectral analysis in order to reflect the dependence of the speech quality on the correct positioning of the dental prostheses. We also search some quantitative parameters, which reflect the correct position of dental prostheses in a sensitive manner.     

Can a reduction approach predict reliable joint contact and musculo-tendon forces?

Musculoskeletal models generally solve the muscular redundancy by numerical optimisation. They have been extensively validated using instrumented implants. Conversely, a reduction approach considers only one flexor or extensor muscle group at the time to equilibrate the inter-segmental joint moment. It is not clear if such models can still predict reliable joint contact and musculo-tendon forces during gait.Tibiofemoral contact force and gastrocnemii, quadriceps, and hamstrings musculo-tendon forces were estimated using a reduction approach for five subjects walking with an instrumented prosthesis. The errors in the proximal-distal tibiofemoral contact force fell in the range (0.3–0.9 body weight) reported in the literature for musculoskeletal models using numerical optimisation. The musculo-tendon forces were in agreement with the EMG envelops and appeared comparable to the ones reported in the literature with generic musculoskeletal models.Although evident simplifications and limitations, it seems that the reduction approach can provided quite reliable results. It can be a useful pedagogical tool in biomechanics, e.g. to illustrate the theoretical differences between inter-segmental and contact forces, and can provide a first estimate of the joint loadings in subjects with limited musculoskeletal deformities and neurological disorders.     

Towards reducing the impacts of unwanted movements on identification of motion intentions

Surface electromyogram (sEMG) has been extensively used as a control signal in prosthesis devices. However, it is still a great challenge to make multifunctional myoelectric prostheses clinically available due to a number of critical issues associated with existing EMG based control strategy. One such issue would be the effect of unwanted movements (UMs) that are inadvertently done by users on the performance of movement classification in EMG pattern recognition based algorithms. Since UMs are not considered in training a classifier, they would decay the performance of a trained classifier in identifying the target movements (TMs), which would cause some undesired actions in control of multifunctional prostheses. In this study, the impact of UMs was systemically investigated in both able-bodied subjects and transradial amputees. Our results showed that the UMs would be unevenly classified into all classes of the TMs. To reduce the impact of the UMs on the performance of a classifier, a new training strategy that would categorize all possible UMs into a new movement class was proposed and a metric called Reject Ratio that is a measure of how many UMs is rejected by a trained classifier was adopted. The results showed that the average Reject Ratio across all the participants was greater than 91%, meanwhile the average classification accuracy of TMs was above 99% when UMs occurred. This suggests that the proposed training strategy could greatly reduce the impact of UMs on the performance of the trained classifier in identifying the TMs and may enhance the robustness of myoelectric control in clinical applications.     

人工视觉辅助系统：现状与展望

通过视觉获取图像信息是人类学习和生活的重要功能,失明则会显著降低其生活质量.因视网膜色素变性、青光眼和黄斑变性等疾病而造成后天失明者,以及由意外事故、战争等造成眼部创伤者,有可能通过人工视觉辅助系统的帮助恢复部分视觉,或者完成复杂的生活任务.一些盲症患者视觉通路的神经传导剩余部分依然有功能,因此可以借助电极阵列刺激视神经向大脑传递视觉信息,也可在大脑视觉皮层贴敷电极阵列的方法输入视觉信息.此外,还能借助体外装置,如通过人工智能将视觉转换成语音指令、触觉阵列编码等,帮助盲症患者获得环境信息.本文综述各类人工视觉辅助系统的现状,展望其发展趋势,并提出了新的植入器件与随身体外装置的新设想.     

Computer-aided dental prostheses construction using reverse engineering

The implementation of computer-aided design/computer-aided manufacturing (CAD/CAM) systems with virtual articulators, which take into account the kinematics, constitutes a breakthrough in the construction of customised dental prostheses. This paper presents a multidisciplinary protocol involving CAM techniques to produce dental prostheses. This protocol includes a step-by-step procedure using innovative reverse engineering technologies to transform completely virtual design processes into customised prostheses. A special emphasis is placed on a novel method that permits a virtual location of the models. The complete workflow includes the optical scanning of the patient, the use of reverse engineering software and, if necessary, the use of rapid prototyping to produce CAD temporary prostheses.     

A novel adaptive algorithm for 3D finite element analysis to model extracortical bone growth

Extracortical bone growth with osseointegration of bone onto the shaft of massive bone tumour implants is an important clinical outcome for long-term implant survival. A new computational algorithm combining geometrical shape changes and bone adaptation in 3D Finite Element simulations has been developed, using a soft tissue envelope mesh, a novel concept of osteoconnectivity, and bone remodelling theory. The effects of varying the initial tissue density, spatial influence function and time step were investigated. The methodology demonstrated good correspondence to radiological results for a segmental prosthesis.     

Fast Soft Tissue Deformation and Stump-Socket Interaction Toward a Computer-Aided Design System for Lower Limb Prostheses

Prosthetic technology is rapidly advancing but there's a catch. Regardless the technology or the material used, a minimum cost is still high. One of the problems relates to the fact that the conventional socket fabrication process is still used. This method is based on subjective estimations of the involved specialists and feedbacks of the patients. This process consumes remarkable amount of time, manpower and materials. Research works are needed to design new efficient and low-cost alternative techniques for the socket design. This technique should definitely be based on CAD-CAM methods. Therefore, the first step toward this objective is to establish an accurate numeric model for evaluating and optimizing the design process. In this present work, we developed a new approach to simulate the stump soft tissue deformation and stump-socket interaction using Mass-Spring System (MSS) approach and a point-to-surface contact formulation.A novel Mass-Spring System with corrective spring (MSS-CS) model was developed and evaluated. A node-to-surface contact formulation was also integrated and evaluated. The MSS-CS model and contact formulation were evaluated with primitive geometrical object and a stump-socket model. Moreover, a finite element model of the stump-socket interaction was also developed using Abaqus to evaluate the proposed approach.Obtained results show that the proposed contact formulation has a very good precision level and the contact pressures on the interface between the elastic and rigid bodies are very close to the analytical solutions. The comparison with Abaqus showed a qualitative concordance for the contact pressure. However, quantitative deviation remains high [25-50]% at the peak contact pressure due to different contact formulations. In particular, our MSS-CS approach is more efficient than Abaqus simulation in term of computational time and cost.A novel approach was proposed to model soft tissue deformation and stump-socket interaction in an efficient and accurate manner. As perspectives, this present approach for a real-time simulation of the stump-socket interaction could be used in a real-time CAD-CAM platform to provide a cost-effective socket manufacturing process.     

A finite element analysis of the vibration behaviour of a cementless hip system

An early diagnosis of aseptic loosening of a total hip replacement (THR) by plain radiography, scintigraphy or arthography has been shown to be less reliable than using a vibration technique. However, it has been suggested that it may be possible to distinguish between a secure and a loose prosthesis using a vibration technique. In fact, vibration analysis methods have been successfully used to assess dental implant stability, to monitor fracture healing and to measure bone mechanical properties. Several studies have combined the vibration technique with the finite element (FE) method in order to better understand the events involved in the experimental technique. In the present study, the main goal is to simulate the change in the resonance frequency during the osseointegration process of a cementless THR (Zweymüller). The FE method was used and a numerical modal analysis was conducted to obtain the natural frequencies and mode shapes under vibration. The effects were studied of different bone and stem material properties, and different contact conditions at the bone–implant interface. The results were in agreement with previous experimental and computational observations, and differences among the different cases studied were detected. As the osseointegration process at the bone–implant interface evolved, the resonance frequency values of the femur–prosthesis system also increased. In summary, vibration analysis combined with the FE method was able to detect different boundary conditions at the bone–implant interface in cases of both osseointegration and loosening.