Application of HoloLens-based augmented reality and three-dimensional printed anatomical tooth reference models in dental education.

Tooth anatomy is fundamental knowledge used in everyday dental practice to reconstruct the occlusal surface during cavity fillings. The main objective of this project was to evaluate the suitability of two types of anatomical tooth reference models used to support reconstruction of the occlusal anatomy of the teeth: (1) a three-dimensional (3D)-printed model and (2) a model displayed in augmented reality (AR) using Microsoft HoloLens. The secondary objective was to evaluate three aspects impacting the outcome: clinical experience, comfort of work, and other variables. The tertiary objective was to evaluate the usefulness of AR in dental education. Anatomical models of crowns of three different molars were made using cone beam computed tomography image segmentation, printed with a stereolithographic 3D-printer, and then displayed in the HoloLens. Each participant reconstructed the occlusal anatomy of three teeth. One without any reference materials and two with an anatomical reference model, either 3D-printed or holographic. The reconstruction work was followed by the completion of an evaluation questionnaire. The maximum Hausdorff distances (Hmax) between the superimposed images of the specimens after the procedures and the anatomical models were then calculated. The results showed that the most accurate but slowest reconstruction was achieved with the use of 3D-printed reference models and that the results were not affected by other aspects considered. For this method, the Hmax was observed to be 630 µm (p = 0.004). It was concluded that while AR models can be helpful in dental anatomy education, they are not suitable replacements for physical models.

A survey on electromagnetic hypersensitivity: the example from Poland.

Idiopathic environmental intolerance attributed to electromagnetic field (IEI-EMF) called electromagnetic hypersensitivity or electrosensitivity appeared in Polish society awareness due to a considerable change made at the end of 2019 in Polish telecommunication laws. The aims of the project were to access the prevalence of IEI-EMF in Poland and to define a reliable methodology to study this phenomenon. The first step was the internet survey performed at the end of 2018. The IEI-EMF prevalence estimated at the level of 39.7% suggested considerable bias affecting the results. The faults of the first approach were analysed and then a second study stage was performed as a telephone survey at the end of 2020. The latter survey allowed estimating the prevalence of IEI-EMF as less than 1.8%. These discrepancies in the results of both surveys were connected to the medium used in the first survey (Internet) indirectly causing that the group pooled was not representative. The second pitfall was the definition of the criteria used for an electrosensitive person classification. This is why the IEI-EMF prevalence was investigated in the second stage with the use of numerous criteria. The application of different criteria allowed for essential conclusions concerning the appropriate methodology for such kinds of studies. Corrections of the methodology before the second survey allowed reliable results consistent with the results obtained in similar studies performed in other countries. Our findings also show that the IEI-EMF frequency reports presented in the literature have to be treated carefully and with some dose of scepticism.

The popliteofibular ligament: a cadaveric ultrasound study.

OBJECTIVE: The popliteofibular ligament (PFL) is an important stabilizer of the knee found within the posterolateral corner (PLC) of the joint. Injuries to the PLC can cause substantial patient morbidity. Accurate PFL visualization has been historically challenging, impeding injury diagnosis and treatment. The gold standard for in vivo PFL visualization is magnetic resonance imaging (MRI), but this procedure has slice thickness limitations, is costly, and is subject to longer wait times. Ultrasonographic (US) PFL assessment is a potentially viable alternative to MRI. This study aimed to determine the viability of US PFL assessment. MATERIALS AND METHODS: Ten fresh-frozen lower limb specimens were evaluated for the presence and morphometric characteristics of the PFL via US using an 18.0-MHz linear transducer. The cadavers were then dissected and reassessed for the presence and morphometric characteristics of the PFLs for comparison with US findings. Moreover, the fracture of the fibular styloid process near the site of the insertion of the PFL (the arcuate sign) was simulated and assessed via US. RESULTS: The PFL was visualized and measured in all ten knees via both US and cadaveric assessments. There were no statistically significant differences in PFL morphometric characteristics determined via US examination and dissection. The fibular styloid fracture was easily identified in US examination. CONCLUSION: US imaging is a viable alternative for accurate and effective assessment of the normal PFL. Moreover, the arcuate sign can be evaluated via US.

Physics Doesn't Bite-A Simple Experiment for Introducing Biomechanical Operational Principles of the Temporomandibular Joint.

Biophysics is rarely mentioned as one of the most useful parts of dental and medical students' curricula. However, with the growing complexity of tools and methods used in diagnostics and therapy, the knowledge of their physical foundations becomes important and helps with choosing the optimal solutions for both, a patient and a doctor. The aim of the proposed activity is to develop students' intuition about simple physical models that help with understanding fundamental properties of temporomandibular joint (TMJ). A simple device, which allows for bite force measurement, is proposed. It is based on beam bending and a strain gauge Wheatstone bridge circuit mounted on two connected arms: the stiff one and the more elastic one. Linear regression is the only mathematical concept needed for understanding the physical background of the proposed activity. During the proposed activity-measuring of bite force for incisors, premolars, and molars-students are confronted with basic concepts, such as lever, torque, electrical circuit, calibration curve. By utilizing a simple idea, instead of a commercially available device, students can understand where the data come from. Proposed system delivers physiologically reasonable results.

The Impact of Mobile Phone Use on Tinnitus: A Systematic Review and Meta-Analysis.

Tinnitus is a perception of sound in the absence of an external source. The aim of our study was to investigate with a meta-analytical approach, whether mobile phone (MP) use increases the risk of tinnitus. Eight studies reporting the risk of tinnitus in relation to MP use were identified, and six high-quality studies (two cohort studies, one case-control study, and three cross-sectional ones) were included in the meta-analysis. The quality assessment was performed using the Newcastle-Ottawa scale. The risk of tinnitus was analyzed depending on the exposure to MPs in subgroups according to the study design and method of exposure assessment. Two cohort studies, which assessed the exposure to MPs using network operator data, indicated no significantly increased risk of tinnitus among highly exposed MP users in comparison to lightly exposed individuals (odds ratio [OR]: 1.03 [95% confidence interval [CI]: 0.93-1.15]). Likewise, the self-reported exposure data from two cohorts/case-control and four cross-sectional studies did not find an association between exposure to MPs and tinnitus (OR: 1.20 [95% CI: 0.40-3.61] and OR: 1.73 [95% CI: 0.67-4.49], respectively). Current scientific knowledge, including high-quality studies with a reliable exposure assessment based on network operator data, does not support the hypothesis that MP use is associated with tinnitus. © 2020 Bioelectromagnetics Society.

Which sources of electromagnetic field are of the highest concern for electrosensitive individuals? - Questionnaire study with a literature review.

The primary goal of the study was to identify sources of electromagnetic field (EMF) which are attributed to negative health outcomes by a general population of electrohypersensitive (EHS) individuals. Secondary goal was to investigate the differences in indicated sources in subgroups distinguished based on gender, sex, place of living, place of work and the distance between place of living and the nearest mobile phone base station (MPBS). The cross-sectional study aiming to describe and analyze the population of EHS subjects was performed using a web-based questionnaire. The full survey consisted of 32 questions and concerned participants' baseline characteristics and details on sensitivity to electronic devices. Participants were regarded as EHS if they answered "yes" to the question "Do the electric/electronic/telecommunication devices negatively affect your well-being?" and indicated at least one device which in their opinion had such an impact. We identified 408 EHS subjects, out of which 288 (70.73%) were females and 120 (29.27%) were males. Phones, especially mobile devices, were attributed to negative health outcomes by the highest number of subjects (309, 75.74% and 267, 65.44% for phones and mobile phones, respectively). Additional subgroup analysis indicated that older participants and participants who live closer to MPBS more often complained of physical symptoms attributed to MPBS impact (p = .02 and p < .01, respectively). Phones, especially mobile devices, are the most important source of EMF influencing EHS subjects. People who self-reported living closer to MPBS and older individuals seem to be remarkably more concerned about MPBS health impact.

Does the short-term exposure to radiofrequency electromagnetic field originating from mobile phone affect auditory functions as measured by Acoustic Admittance and Evoked Otoacoustic Emission tests?

BACKGROUND: Mobile phones constitute an important source of radiofrequency electromagnetic field (RF-EMF) for humans. Taking into account high sensitivity of sensory hair cells of the inner ear to endogenous and exogenous agents, the potential impact of mobile phone usage on auditory organs is of particular interest. AIM: The aim of the study was to evaluate the impact of short-term exposure to RF-EMF generated by a mobile phone during 15-minute simulated phone call on human hearing as measured by Transient Evoked Otoacoustic Emission (TEOAE) and Acoustic Admittance Testing (AAT). MATERIAL AND METHODS: Within-subject study was performed on 23 healthy volunteers. All of the participants underwent TEOAE and AAT before and immediately after 15-minute simulated phone call with the use of a standard, modern smartphone. Analyzed parameters included: static compliance of tympanic membrane, middle ear pressure, ipsi- and contralateral acoustic reflex thresholds and percentage of signal reproducibility in TEOAE for exposed and non-exposed ear. Additionally, the results were compared in subgroups distinguished basing on self-reported sensitivity to RF-EMF originating from mobile phones. RESULTS: No statistically significant differences were identified between results of TEOAE and AAT before and after exposure, both in exposed and non-exposed ear. The results of EMF sensitive and non-sensitive subjects were comparable in all performed tests. CONCLUSIONS: Short-term exposure to mobile phone electromagnetic field did not influence auditory functions as measured by Evoked Otoacoustic Emission test and Acoustic Admittance Testing.

Thermographic assessment of skin prick tests in comparison with the routine evaluation methods.

INTRODUCTION: The skin prick test is still the first and basic procedure in the diagnosis of allergic diseases. The possibility of using a sensitive thermographic method supported by the mathematical model for the assessment of skin test results will be highlighted in the studies. AIM: To compare the proposed approach with routine planimetric and thermographic methods. MATERIAL AND METHODS: A mathematical model of allergic reaction was developed. Simplifying assumptions of the IgE-mediated skin reaction is the essence of the model. Investigations were performed in a group of 40 patients. RESULTS: Using the spatio-temporal evolution of temperature distributions, the ratios of the histamine released from mast cells to the control histamine were determined. The obtained values very well correlate with the standard evaluation of skin prick tests (correlation coefficient = 0.98). CONCLUSIONS: The proposed method of skin test evaluation presents several advantages. The continuous acquisition of data provides the monitoring of time course of the allergic response. The transport of mediator and its concentration were distinctly discriminated, which may be diagnostically useful, especially for abnormal cases. The high sensitivity of the method enables studying patients regardless of age and skin sensitivity.

Improved reliability for fractal dimension calculation of the vascular imprints on the cranial vault mapped with topographical correction.

We presented a novel approach to studies of the vascular grooves located on the inner surface of the cranial vault. A three-dimensional vision system that acquired the endocranial surface topography was used for this purpose. The acquired data were used to generate images showing the branching pattern of the middle meningeal artery. Fractal dimension was used to characterize and analyze branching pattern complexity. We discussed the usefulness of the latter method and indicated difficulties and potential errors connected to the fractal dimension application. The technique introduced for recording traits of the object surface appears to be helpful in anatomical study of morphological variation of dural vascularization. It may also be applicable in paleoneurological research based on analysis of the cranial remnants. Fractal dimension should be used carefully as a method sensitive to many aspects of data acquisition and processing.

The ratio of anterior and posterior vertebral heights reinforces the utility of DXA in assessment of vertebrae strength.

The objective of the study was to introduce a new parameter describing bone strength with greater precision than the widely used antero-posterior DXA (dual-energy X-ray absorptiometry), which measures areal bone mineral density (aBMD). The adjusted areal bone mineral density (AaBMD) defined as the ratio between aBMD and h a/h p (h a and h p: anterior and posterior vertebral body heights measured on the lateral view, respectively) is proposed: AaBMD = aBMD/(h a/h p). The utility of AaBMD in prediction of bone strength was assessed by in vitro measurements of cadaver L3 vertebrae. The AaBMD of 31 vertebrae was correlated with the ultimate stress (P max) and load (F max) values obtained in mechanical tests. The correlations were compared to those obtained for aBMD and for volumetric bone mineral density (vBMD) measured by computed tomography. The correlation of AaBMD to F max adjusted for donor's age was significantly higher than for aBMD and vBMD (r = 0.740, 0.658, and 0.609, respectively, p < 0.05). The differences between partial correlation coefficients for P max to AaBMD, aBMD and vBMD relationships were smaller (r = 0.764, 0.720, and 0.732, respectively, p < 0.05), but also showed the superiority of AaBMD. Combining antero-posterior DXA aBMD and the lateral h a/h p ratio, measured, for example, by the Vertebral Fracture Assessment software of the new generation of DXA devices, seems to accurately predict the mechanical vertebral parameters related to bone strength. It is assumed that the proposed AaBMD parameter may be more predictive for fracture risk assessment, which requires further studies.

Combining areal DXA bone mineral density and vertebrae postero-anterior width improves the prediction of vertebral strength.

OBJECTIVE: Areal bone mineral density (aBMD) measured by dual-energy X-ray absorptiometry (DXA) is an important determinant of bone strength (BS), despite the fact that the correlation between aBMD and BS is relatively weak. Parameters that describe BS more accurately are desired. The aim of this study was to determine whether the geometrical corrections applied to aBMD would improve its ability for BS prediction. We considered new parameters, estimated from a single DXA measurement, as well as BMAD (bone mineral apparent density) reported in the literature. MATERIALS AND METHODS: In vitro studies were performed with the L3 vertebrae from 20 cadavers, which were studied with DXA and quantitative computed tomography (QCT). A mechanical strength assessment was carried out. Two new parameters were introduced: vBMD(min) = aBMD/W(PA)(min) and vBMD(av) = aBMD/W(PA)(av) (W PA(min) -minimal vertebral body width in postero-anterior (PA) view, W(PA)(av) - average PA vertebral body width). Volumetric BMD measured by QCT (vBMD), aBMD, BMAD, vBMD(min), and vBMD(av) were correlated to ultimate load and ultimate stress (P(max)) to find the best predictor of vertebrae BS. RESULTS: The coefficients of correlation between P(max) and vBMD(min), vBMD(av), as well as BMAD, were r = 0.626 (p = 0.005), r = 0.610 (p = 0.006) and r = 0.567 (p = 0.012), respectively. Coefficients for vBMD and aBMD are r = 0.648 (p = 0.003) and r = 0.511 (p = 0.03), respectively. CONCLUSIONS: Our results showed that aBMD normalized by vertebrae dimensions describes vertebrae BS better than aBMD alone. The considered indices vBMD(av), vBMD(min), and BMAD can be measured in routine PA DXA and considerably improve BS variability prediction. vBMD(min) is superior compared to vBMD(av) and BMAD.

Application of geometrical measurements in the assessment of vertebral strength.

BACKGROUND: The study was aimed at the development of parameters that could be used as predictors of vertebral strength. Proposed parameters describing vertebral geometry and/or shape can be established on the basis of routine spine roentgenograms, making roentgenography a novel tool for vertebral fracture risk assessment in the future. MATERIAL/METHODS: 20 human cadaveric L3 vertebrae were included in the study. Dual-energy X-ray absorptiometry (DXA) was used for an assessment of bone mineral density (BMD). Quantitative computed tomography (QCT) was performed to measure the volumetric bone density as the most reliable parameter in vertebral fracture risk assessment. Geometrical measurements were performed on the basis of high quality and high resolution computer tomography 3-dimensional images. Biomechanical tests were performed to measure vertebral strength. Two parameters were defined on the basis of extensive research: the ratio between vertebral base area and its height (A/H), and the ratio of vertebral coronal width to coronal height (W/H). Correlations between vertebral mechanical strength - its BMD, QCT density, A/H and W/H were calculated. RESULTS: The best correlation to bone durability was achieved for QCT density (r=0.882), while correlation strength for BMD (r=0.779) and A/H (r=-0.773) were comparable. W/H correlated better than BMD to mechanical strength (-0.788). CONCLUSIONS: Geometrical parameters of vertebrae potentially measured on spine radiograms could be used as predictors of vertebral durability. The calculated correlation coefficients suggest that one of the proposed parameters works better than the commonly used BMD.

Chemical composition and morphology of renal stones.

Two issues related to nephrolithiasis are explored: (1) does the chemical composition and morphology of renal calculi in South Poland overlap with the studies from other countries? and (2) are there possibilities to evaluate in vivo chemical composition of stones using computed tomography? The study was conducted on 108 renal stones. X-ray fluorescence, X-ray diffraction and Fourier transformed infrared spectroscopy were used to determine the chemical composition. The morphology of the stones was examined using micro computed tomography. The stone chemical composition in South Poland indicate that calcium oxalate monohydrate was overwhelmingly dominant (84%) followed by hydroxyapatite (8%) and struvite (6%). The occurrence of uric acid stones was very low (2%). The relative frequency of various stone types is similar in South Poland to other industrialized countries. The studied renal stones were characterized by a large variability in the concentrations of both major and trace elements. The maximum/minimum concentration ratio exceeds two orders of magnitude. Significant morphological differences have been observed between different types of stones. The stones were composed of oxalate polyhedrons stuck together or had the phosphate core overlaid with layers oxalate and organic mater. The use of CT to identify stone type seems to be limited.

Oversampling in the computed tomography measurements applied for bone structure studies as a method of spatial resolution improvement.

BACKGROUND: Our purpose was to check the potential ability of oversampling as a method for computed tomography axial resolution improvement. The method of achieving isotropic and fine resolution, when the scanning system is characterized by anisotropic resolutions is proposed. In case of typical clinical system the axial resolution is much lower than the planar one. The idea relies on the scanning with a wide overlapping layers and subsequent resolution recovery on the level of scanning step. MATERIAL/METHODS: Simulated three-dimensional images, as well as the real microtomographic images of rat femoral bone were used in proposed solution tests. Original high resolution images were virtually scanned with a wide beam and a small step in order to simulate the real measurements. The low resolution image series were subsequently processed in order to back to the original fine one. Original, virtually scanned and recovered images resolutions were compared with the use of modulation transfer function (MTF). RESULTS/CONCLUSIONS: A good ability of oversampling as a method for the resolution recovery was showed. It was confirmed by comparing the resolving powers after and before resolution recovery. The MTF analysis showed resolution improvement. The resolution improvement was achieved but the image noise raised considerably, which is clearly visible on image histograms. Despite this disadvantage the proposed method can be successfully used in practice, especially in the trabecular bone studies because of high contrast between trabeculae and intertrabecular spaces.

Application of thermography for the assessment of allergen-induced skin reactions.

PURPOSE: The allergic response is commonly identified and assessed by skin testing. The usual method to quantify skin reactions is to mark wheal and erythema regions and assess the surfaces affected by the reactions; however, subjective interpretation of the outcome may cause errors. Skin thermography supplemented by a mathematical model based on the pathophysiology of heat generation was evaluated as a novel, objective, and sensitive indicator of the skin prick test result. METHODS: TH measurements were performed simultaneously with routine skin prick tests for 24 patients. Eight allergens and control (histamine) were examined. Thermographic images of both forearms were acquired every 70 s from 0 to 910 s after skin prick and analyzed with the use of dedicated software. The introduction of potential allergens and histamine at sites on the skin induces a complex sequence of events known as the local inflammatory response. The crucial steps of the process have been considered in the model. In the model, the authors assumed that the reaction takes place in the thin skin layer and that histamine is the principal mediator of the allergic reaction. Histamine penetrates the skin and binds to receptors of nearby capillaries and venules. The engorged vessels are, in turn, responsible for skin redness and an increase in skin temperature. RESULTS: The model parameters were determined by fitting the analytical solutions to the spatiotemporal distributions of the differences between measured and baseline temperatures. The model reproduces experimental data very well. The coefficient of determination ranged from 0.805 to 0.995. Seven model parameters were tested to find the optimal marker of the intensity and kinetics of the allergic reaction. The parameter which quantifies a release of histamine after allergen injection has appeared to be the best indicator of the allergen-induced response. The parameter correlates with the routine assessment based on wheal and erythema areas (correlation coefficient = 0.98). CONCLUSIONS: It was demonstrated that the thermographic measurements supplemented by the mathematical model offer a new approach to the quantification of allergen-induced skin reactions. Despite the applied simplifications, the proposed model reflected properly the mechanism of heat generation during skin prick test. Moreover, the continuous recording of the skin temperature represents an additional possibility to investigate the mechanism of the allergic reaction.

Geometry corrections in a rotating 3-dimensional sonographic system.

OBJECTIVE: To devise a system for geometry corrections in a rotating 3-dimensional sonographic system. METHODS: A 3-dimensional sonographic imaging system based on a standard sonography machine was developed. The transducer mounted in a specially designed holder was rotated about its axis to acquire the spatial information. The most important postulate in rotating 3-dimensional systems is the assumption of parallelity between the rotation axis and the transducer axis. It allows the use of simple geometric relationships between 2-dimensional slices in a 3-dimensional reconstruction. The errors appearing in the 3-dimensional reconstruction when the axes are not parallel were investigated. RESULTS: A simple correction method based on phantom measurements is proposed. The phantom contains a plane, which is inclined to the rotation axis. The analysis of 2-dimensional plane images allows the geometric corrections. The construction of the phantom is described, and the formulas used in the calculations are presented. The method was tested in computer simulations and in patient investigations. CONCLUSIONS: A complete method of the geometric investigations and corrections useful in 3-dimensional sonographic systems based on rotational geometry is proposed. Both the computer simulations and the phantom measurements confirmed the usefulness, precision, and simplicity of the proposed method.