Accuracy of virtually planned and CAD/CAM-guided dental implant surgery

The treatment with dental implants was introduced in the 1960s as an aid for patients who were missing teeth. Recently CAD/CAM guided surgical concepts have been launched on the market as a solution for treating single, partial or completely edentulous patients with dental implants. The mucosa based surgical templates is one of the fairly new dental implant systems on the market for treating patients. With this new technique it is crucial to thoroughly evaluate the accuracy, in order to avoid damaging sensitive anatomical structures of patients. Another factor of importance to consider, is the possibility to connect the bridge immediately onto the CAD/CAM guided placed implants. Companies could also benefit from more knowledge about accuracy in order to, i.e., further improve the instructions and the hardware to further enhance the security and usability of the systems. The general aim of this project was to evaluate the accuracy between virtually planned and actually placed dental implants using a surgical guide. Study I and III aimed to compare the deviation between the position of virtually planned implants and the position of implants placed with a CAD/CAM-guided surgical template in the mandible and maxilla. The aim of Study II was to perform virtual variation simulations on virtually planned implant placements and to compare them with corresponding results from actual surgeries, performed on human cadavers in Study I. In Study IV the aim was to evaluate the deviation between the results obtained from five different surgeons, from CAD/CAM guided implant surgery on plastic jaw models. Completely edentulous human cadavers, patients and plastic maxilla jaw models were included in Study I, III and IV. Study II utilized 3D STL files obtained from Study I. Study I and III, demonstrated a statistical significant difference between the virtually planned implant positions and the clinically placed implant positions after surgery. Study I demonstrated a statistically significant difference between mandibles and maxillae for the outcome variables, hex, apex and depth measurements, with smaller deviations for the maxilla. In Study III it was found that the patients moved during the preoperative and postoperative CBCT scans. When combining the movement factor between the virtually planned implants and actually placed implants positions, a statistical significant difference was observed for the hex and apex. If the movement factor was included, a statistical significant difference was found between the maxilla and mandible for the outcome variable angle. In Study II, the implant distributions were neither static nor normally distributed. Thus, within the limitations of this study, the definitive geometrical variations of the implants were not static, as they depend on the individual anatomy of the jaws and the ability to place the CAD/CAM-guided surgical template in the proper position. The Mann-Whitney U test showed that the definitive implant distributions in this study could not be assumed to be normally distributed. In Study IV a statistically significant difference was observed between all five surgeons for the outcome variables, apex, depth and angle. A statistically significant difference was also found between the virtually planned implant positions and the actually placed implant positions for the outcome variables, apex, hex and depth. The mean value was smallest for the plastic jaw model study and largest for the human cadaver study, for the outcome variables, apex, hex and angle. For the depth, the smallest mean value was present in the patient study and largest in the plastic model study. However, the human cadaver study and patient study presented a larger range in deviation. Further studies have to be performed to evaluate the contributing factors of all steps involved in CAD/CAM guided surgery. In order to further improve knowledge about guided surgery accuracy, it is important to perform accuracy studies on conventional surgery in order to compare the results and, thus, provide a more secure treatment to the patients. In other words, the most important goal is to provide the most secure treatment available for the patients

Towards WCET Analysis of Multicore Architectures Using UPPAAL

To take full advantage of the increasingly used shared-memory multicore architectures, software algorithms will need to be parallelized over multiple threads. This means that threads will have to share resources (e.g. some level of cache) and communicate and synchronize with each other. There already exist software libraries (e.g. OpenMP) used to explicitly parallelize available sequential C/C++ and Fortran code, which means that parallel code could be easily obtained. To be able to use parallel software running on multicore architectures in embedded systems with hard real-time constraints, new WCET (Worst-Case Execution Time) analysis methods and tools must be developed. This paper investigates a method based on model-checking a system of timed automata using the UPPAAL tool box. It is found that it is possible to perform WCET analysis on (small) parallel systems using UPPAAL. We also show how to model thread synchronization using spinlock-like primitives

Computational analysis of shock-induced flow through stationary particle clouds

We investigate the shock-induced flow through random particle arrays using particle-resolved Large Eddy Simulations for different incident shock wave Mach numbers, particle volume fractions and particle sizes. We analyze trends in mean flow quantities and the unresolved terms in the volume averaged momentum equation, as we vary the three parameters. We find that the shock wave attenuation and certain mean flow trends can be predicted by the opacity of the particle cloud, which is a function of particle size and particle volume fraction. We show that the Reynolds stress field plays an important role in the momentum balance at the particle cloud edges, and therefore strongly affects the reflected shock wave strength. The Reynolds stress was found to be insensitive to particle size, but strongly dependent on particle volume fraction. It is in better agreement with results from simulations of flow through particle clouds at fixed mean slip Reynolds numbers in the incompressible regime, than with results from other shock wave particle cloud studies, which have utilized either inviscid or two-dimensional approaches. We propose an algebraic model for the streamwise Reynolds stress based on the observation that the separated flow regions are the primary contributions to the Reynolds stress.Comment: 33 pages, 23 figures, 3 table

Limiting factors in capercaillie (Tetrao urogallus) conservation

With current extinction rates comparable with the rates of previous mass extinctions and humanities necessity of biodiversity, conservation of habitat and species should be regarded as paramount whenever planning land use. In this paper we have focused on the Western capercaillie (Tetrao urogallus) an umbrella species in Eurasian boreal and temperate forests. Capercaillie numbers have been reduced in mainland Europe and British Isles during the last century mainly due to increased predator populations, habitat loss, fragmentation and degradation as a result of human development of agriculture and land use change. Human recreation in sites with capercaillie show increased levels of stress in the capercaillies which might contribute to their decline. Programs in Scotland, Germany, Spain and Poland have the aim to aid or reintroduce populations in the capercaillies historic range. Practices with the aims to reintroduce or re-stock populations often consist of releasing individuals reared in facilities or breeding centers into suitable habitat. High mortality shortly after releasing due to high predation as a result of mal adapted physical and behavior traits leads to failure in most programs. Predator management and new techniques that improve the physical and behavioral quality in reared capercaillies such as choice of rearing method, large flight pens, elevated roost and anti-predatory training have shown increased fitness and increased survival. The use of PVA tools is effective when comparing different procedures or scenarios and should be used as a decision basis.Nutidens utrotningstakt som kan jämföras med takterna under de tidigare massutdöendena och mänsklighetens behov av ekosystemtjänster som upprätthålls tack vare biodiversitet bör bevarande av habitat och arter ha en tydlig roll vid planering av markanvändning. I detta arbete har vi fokuserat på Tjäder (Tetrao urogallus) som anses vara en paraplyart i eurasiska boreala och tempererade skogar. På den europeiska kontinenten har tjäderpopulationer minskat det senaste århundradet främst på grund av ökat predationstryck samt degradering, fragmentering och förlust av habitat. Även mänsklig störning knuten till rekreation ger ökade stressnivåer hos tjädrar vilket kan vara en bidragande faktor till minskande populationer. I Skottland, Tyskland, Spanien och Polen finns program med mål att återintroducera eller bevara tjäderpopulationer. Liknande program präglas av låga framgångssiffror. Hög predation bland tjädrar kort efter utsläpp till viss del som effekt av underutvecklade fysiska- och psykiska egenskaper. Predatorkontroll samt nya metoder att föda upp tjädrar bidrar till ökad framgång i försök. PVA är ett verktyg som effektivt kan användas för att bedöma vilket scenario i människans försök att bevara tjäder som är mest slagkraftigt

Uncertainty modelling in multi-criteria analysis of water safety measures

Water utilities must assess risks and make decisions on safety measures in order to obtain a safe and sustainable drinking water supply. The World Health Organization emphasises preparation of Water Safety Plans, in which risk ranking by means of risk matrices with discretised probability and consequence scales is commonly used. Risk ranking enables prioritisation of risks but there is currently no common and structured way of performing uncertainty analysis and using risk ranking for evaluating and comparing water safety measures. To enable a proper prioritisation of safety measures and an efficient use of available resources for risk reduction, two alternative models linking risk ranking and multi-criteria decision analysis (MCDA) are presented and evaluated. The two models specifically enable uncertainty modelling in MCDA and they differ in terms of how uncertainties in risk levels are considered. The need of formal handling of risk and uncertainty in MCDA is emphasised in the literature and the suggested models provide innovations that are not dependent on the application domain. In the case study application presented here, possible safety measures are evaluated based on the benefit of estimated risk reduction, the cost of implementation and the probability of not achieving an acceptable risk level. Additional criteria such as environmental impact and consumer trust may also be included when applying the models. The case study shows how safety measures can be ranked based on preference scores or cost-effectiveness and how measures not reducing the risk enough can be identified and disqualified. Furthermore, the probability of each safety measure being ranked highest can be calculated. The two models provide a stepwise procedure for prioritising safety measures and enable a formalised handling of uncertainties in input data and results

Particle-resolved simulations of shock-induced flow through particle clouds at different Reynolds numbers

This study investigates the Reynolds-number dependence of shock-induced flow through particle layers at 10\% volume fraction, using ensemble-averaged results from particle-resolved large eddy simulations. The advantage of using large eddy simulations to study this problem is that they capture the strong velocity shears and flow separation caused by the no-slip condition at the particle surfaces. The shock particle cloud interaction produces a reflected shock wave, whose strength increases with decreasing particle Reynolds number. This results in important changes to the flow field that enters the particle cloud. The results show an approximate proportionality between the mean flow velocity and the flow fluctuation magnitudes. Maximum particle drag forces are in excellent agreement with previous inviscid studies, and we complement these results with statistics of time-averaged particle forces as well as the variation of temporal oscillations. The results of this work provides a basis for development of improved simplified dispersed flow models.Comment: 30 pages, 15 figure

An Architecture-Based Verification Technique for AADL Specifications

Abstract. Quality assurance processes of software-intensive systems are an increasing challenge as the complexity of these systems dramatically increases. The use of Architecture Description Languages (ADLs) provide an important basis for evaluation. The Architecture Analysis and Design Language (AADL) is an ADL developed for designing softwareintensive systems. In this paper, we propose an architecture-based verification technique covering the entire development process by adapting a combination of model-checking and model-based testing approaches to AADL specifications. The technique reveals inconsistencies of early design decisions and ensures a system's conformity with its AADL specification. The objective and criteria (test-selection) of the verification technique is derived from traditional integration testing