Jaw System Research Articles

Thermal Sensitivity of Axolotl Feeding Behaviors.

Musculoskeletal movement results from muscle contractions, recoil of elastic tendons, aponeuroses, and ligaments, or combinations thereof. Muscular and elastic contributions can vary both across behaviors and with changes in temperature. Skeletal muscles reach peak contraction speed at a temperature optimum with performance declining away from that optimum by approximately 50% per 10°C, following the Q10 principle. Elastic recoil action, however, is less temperature sensitive. We subjected Axolotls (Ambystoma mexicanum) to changes from warm (23°C), via medium (14°C), to cold (6°C) temperature across most of their thermal tolerance range, and recorded jaw kinematics during feeding on crickets. We sought to determine if suction feeding strikes and food processing chews involve elastic mechanisms and, specifically, if muscular versus elastic contribution vary with temperature for gape opening and closing. Measurements of peak and mean speed for gape opening and closing during strikes and chews across temperature treatments were compared with Q10-based predictions. We found that strike gape speed decreased significantly from warm and medium to cold treatments, indicating low thermal robustness, and no performance-enhancement due to elastic recoil. For chews, peak, and mean gape closing speeds, as well as peak gape opening speed, also decreased significantly from warm to cold treatments. However, peak gape opening and closing speeds for chews showed performance-enhancement, consistent with a previously demonstrated presence of elastic action in the Axolotl jaw system. Our results add to a relatively small body of evidence suggesting that elastic recoil plays significant roles in aquatic vertebrate feeding systems, and in cyclic food processing mechanisms.

Drivers and patterns of bite force evolution in liolaemid lizards

Abstract Phenotypic variation is the result of selection on traits that are relevant in a given ecological context. Phylogenetic history, genetic drift, and any developmental or structural constraints may, however, limit variation in trait expression. It has been proposed that organismal performance traits take up a pivotal role in driving variation in morphology due to their central role in survival and reproductive success. However, how strong the links are between morphology and performance, and how the strength of this relationship impacts the rate of evolution of form and function need to be studied across a wider variety of systems to better understand the origin and evolution of biodiversity. Here we used data on the jaw system (muscle architecture and head dimensions) of liolaemid lizards to investigate the drivers of in vivo bite force variation and test for differences in evolutionary rates in morphology and performance. Our results show high rates of evolution for performance traits compared to morphological traits such as external head dimensions. Many-to-one mapping of morphology to performance, that is the possibility that different anatomical trait combinations lead to similar levels of performance, appears to be common in the jaw system of these lizards. Finally, traits showing greater mechanical sensitivity (muscle cross-sectional areas) showed higher rates of evolution compared to traits involved in other functions and that are probably subject to trade-offs (e.g. head width).

Masticatory system integration in a commensal canid: interrelationships between bones, muscles and bite force in the red fox.

The jaw system in canids is essential for defence and prey acquisition. However, how it varies in wild species in comparison with domestic species remains poorly understood, yet is of interest in terms of understanding the impact of artificial selection. Here, we explored the variability and interrelationships between the upper and lower jaws, muscle architecture and bite force in the red fox (Vulpes vulpes). We performed dissections and used 3D geometric morphometric approaches to quantify jaw shape in 68 foxes. We used a static lever model and bite force estimates were compared with in vivo measurements of 10 silver foxes. Our results show strong relationships exist between cranial and mandible shape, and between cranial or mandible shape on the one hand and muscles or estimated bite force on the other hand, confirming the strong integration of the bony and muscular components of the jaw system. These strong relationships are strongly driven by size. The functional links between shape and estimated bite force are stronger for the mandible, which probably reflects its greater specialisation towards biting. We then compared our results with data previously obtained for dogs (Canis lupus familiaris) to investigate the effect of domestication. Foxes and dogs differ in skull shape and muscle physiological cross-sectional area (PCSA). They show a similar amount of morphological variation in muscle PCSA, but foxes show lower variation in cranial and mandible shape. Interestingly, the patterns of covariation are not stronger in foxes than in dogs, suggesting that domestication did not lead to a disruption of the functional links of the jaw system.

Dental Implant Monitoring Using Resonance Frequency Analysis (RFA) and Cone Beam Computed Tomography (CBCT) Measurement

Dental implants commonly practiced replacing edentulous teeth. However, it is still challenging to evaluate the progress of osseointegration during the healing process after implant placement. This study aims to measure the implant stability of pre- and post-crown placement to monitor osseointegration during the healing process and correlate it with the bone quality and quantity and other parameters. Resonance Frequency Analysis (RFA) method as a standard method has been used to monitor implant stability. Ten patients from Hospital Universiti Sains Malaysia have been involved with and treated by immediate implant placement procedures on their mandibular jaw system. Monitoring was also conducted by measuring the density of bone estimated based on Cone Beam Computed Tomography data. On the basis of the study, RFA and density monitoring show that there are at least three classes of patients: Class 1 are the patients who have a significant increment of implant stability; Class 2 are the patients with constant implant stability; and Class 3 are the patients who have negative implant stability progress, or their implant stability was decreasing. On the basis of the result, monitoring of implant stability by measuring the density is still challenging, the correlation between secondary implant stability and density is not significant statistically. It is recommended in future research to evaluate the implant stability by involving more patients from different races and also correlating the implant stability with the dynamic properties such as stress distribution.

Interrelations Between the Cranium, the Mandible and Muscle Architecture in Modern Domestic Dogs

Many studies have attested to the consequences of the recent and intense artificial selection on the morphological variability of the cranium and mandible in domestic animals. However, the functional relations of the cranium with other constituents of the masticatory apparatus (the mandibles and the adductor muscles) have rarely been explored. Previous work has demonstrated strong relationships between the overall shape of the mandible and muscle data, however, drastic artificial selection in dogs has led to frequent malocclusions, suggesting a possible decoupling between the cranium and the mandible. Moreover, the more complex role of the cranium suggests that it is likely less impacted by, and correlated with, the architecture of the jaw muscles than the mandible. We explored the covariations between cranial and mandibular shape and between cranial shape and the masticatory muscle architecture. Shape analyses were conducted on 58 dogs from various breeds and we used muscle data previously obtained from the dissection of 48 of these dogs. The shape of the cranium was quantified using 3D geometric morphometric approaches. Principal component analyses (PCA) and two-block partial least square analyses (2B-PLS) were used to quantify the variations in cranial shape and the covariations with mandible shape and muscle architecture, respectively. Interestingly, our results reveal strong covariations between cranial shape and mandibular shape and between cranial shape and masticatory muscles mass or physiological cross-sectional area, irrespective of whether size is taken into account or not. We conclude that the drastic artificial selection in domestic dogs has not tainted the integrity of the jaw system, which reinforces previous assumptions hypothesising that phenotypic variability in dogs may be limited by developmental factors.

Systematic revision of the Indo-West Pacific mangrove-associated snails of the genus Bakawan (Cephalaspidea: Haminoeidae)

ABSTRACTThe genus Bakawan includes species of haminoeid snails associated with mangrove habitats and mud flats in the Indo-West Pacific. Here, we revise the diversity and systematics of the genus Bakawan based on our recent molecular phylogeny (Oskars & Malaquias, 2019) and detailed analysis of morphological characters. We examined a range of morphological characters (the shells, external morphology of the animal, jaw, radula, gizzard plate and male reproductive system) using light and scanning electron microscopy. We also carried out a species delimitation analysis (we used the automatic barcode gap discovery method) based on cytochrome c oxidase subunit I DNA sequence data. Four distinct species were recognized: Bakawan rotundata (A. Adams, 1850), which is the type species of the genus and ranges from the eastern Indian Ocean to the western Pacific; B. fusca (A. Adams, 1850), currently known only from the Philippines; and two species new to science, B. puti n. sp., known only from the Philippines, and B. hedleyi n. sp., restricted to tropical eastern Australia.

Decoupled jaws promote trophic diversity in cichlid fishes.

Functional decoupling of oral and pharyngeal jaws is widely considered to have expanded the ecological repertoire of cichlid fishes. But, the degree to which the evolution of these jaw systems is decoupled and whether decoupling has impacted trophic diversification remains unknown. Focusing on the large Neotropical radiation of cichlids, we ask whether oral and pharyngeal jaw evolution is correlated and how their evolutionary rates respond to feeding ecology. In support of decoupling, we find relaxed evolutionary integration between the two jaw systems, resulting in novel trait combinations that potentially facilitate feeding mode diversification. These outcomes are made possible by escaping the mechanical trade-off between force transmission and mobility, which characterizes a single jaw system that functions in isolation. In spite of the structural independence of the two jaw systems, results using a Bayesian, state-dependent, relaxed-clock model of multivariate Brownian motion indicate strongly aligned evolutionary responses to feeding ecology. So, although decoupling of prey capture and processing functions released constraints on jaw evolution and promoted trophic diversity in cichlids, the natural diversity of consumed prey has also induced a moderate degree of evolutionary integration between the jaw systems, reminiscent of the original mechanical trade-off between force and mobility.

Bite force and its relationship to jaw shape in domestic dogs.

Previous studies based on two-dimensional methods have suggested that the great morphological variability of cranial shape in domestic dogs has impacted bite performance. Here, we used a three-dimensional biomechanical model based on dissection data to estimate the bite force of 47 dogs of various breeds at several bite points and gape angles. In vivo bite force for three Belgian shepherd dogs was used to validate our model. We then used three-dimensional geometric morphometrics to investigate the drivers of bite force variation and to describe the relationships between the overall shape of the jaws and bite force. The model output shows that bite force is rather variable in dogs and that dogs bite harder on the molar teeth and at lower gape angles. Half of the bite force is determined by the temporal muscle. Bite force also increased with size, and brachycephalic dogs showed higher bite forces for their size than mesocephalic dogs. We obtained significant covariation between the shape of the upper or lower jaw and absolute or residual bite force. Our results demonstrate that domestication has not resulted in a disruption of the functional links in the jaw system in dogs and that mandible shape is a good predictor of bite force.

Finite element modeling of the periodontal ligament under a realistic kinetic loading of the jaw system

PurposeThe stresses and deformations in the periodontal ligament (PDL) under the realistic kinetic loading of the jaw system, i.e., chewing, are difficult to be determined numerically as the mechanical properties of the PDL is variably present in different finite element (FE) models. This study was aimed to conduct a dynamic finite element (FE) simulation to investigate the role of the PDL (PDL) material models in the induced stresses and deformations using a simplified patient-specific FE model of a human jaw system. MethodsTo do that, a realistic kinetic loading of chewing was applied to the incisor point, contralateral, and ipsilateral condyles, through the experimentally proven trajectory approach. Three different material models, including the elasto-plastic, hyperelastic, and viscoelastic, were assigned to the PDL, and the resulted stresses of the tooth FE model were computed and compared. ResultsThe results revealed the highest von Mises stress of 620.14 kPa and the lowest deformation of 0.16 mm in the PDL when using the hyperelastic model. The concentration of the stress in the elastoplastic and viscoelastic models was in the mid-root and apex of the PDL, while for the hyperelastic model, it was concentrated in the cervical margin. The highest deformation in the PDL regardless of the employed material model was located in the caudal direction of the tooth. The viscoelastic PDL absorbed the transmitted energy from the dentine and led to lower stress in the cancellous bone compared to the elastoplastic and hyperelastic material models. ConclusionThese results have implications not only for understanding the stresses and deformations in the PDL under chewing but also for providing comprehensive information for the medical and biomechanical experts in regard of the role of the material models being used to address the mechanical behavior of the PDL in other components of the tooth.

Functional diversity in biters: the evolutionary morphology of the oral jaw system in pacus, piranhas and relatives (Teleostei: Serrasalmidae)

AbstractSerrasalmid fishes form a highly specialized group of biters that show a large trophic diversity, ranging from pacus able to crush seeds to piranhas capable of cutting flesh. Their oral jaw system has been hypothesized to be forceful, but variation in bite performance and morphology with respect to diet has not previously been investigated. We tested whether herbivorous species have higher bite forces, larger jaw muscles and more robust jaws than carnivorous species. We measured in vivo and theoretical bite forces in 27 serrasalmid species. We compared the size of the adductor mandibulae muscle, the jaw mechanical advantages, the type of jaw occlusion, and the size and shape of the lower jaw. We also examined the association between bite performance and functional morphological traits of the oral jaw system. Contrary to our predictions, carnivorous piranhas deliver stronger bites than their herbivorous counterparts. The size of the adductor mandibulae muscle varies with bite force and muscles are larger in carnivorous species. Our study highlights an underestimated level of functional morphological diversity in a fish group of exclusive biters. We provide evidence that the trophic specialization towards carnivory in piranhas results from changes in the configuration of the adductor mandibulae muscle and the lower jaw shape, which have major effects on bite performance and bite strategy.

Neuromechanical Modelling of Articulatory Movements from Surface Electromyography and Speech Formants.

Speech articulation is produced by the movements of muscles in the larynx, pharynx, mouth and face. Therefore speech shows acoustic features as formants which are directly related with neuromotor actions of these muscles. The first two formants are strongly related with jaw and tongue muscular activity. Speech can be used as a simple and ubiquitous signal, easy to record and process, either locally or on e-Health platforms. This fact may open a wide set of applications in the study of functional grading and monitoring neurodegenerative diseases. A relevant question, in this sense, is how far speech correlates and neuromotor actions are related. This preliminary study is intended to find answers to this question by using surface electromyographic recordings on the masseter and the acoustic kinematics related with the first formant. It is shown in the study that relevant correlations can be found among the surface electromyographic activity (dynamic muscle behavior) and the positions and first derivatives of the first formant (kinematic variables related to vertical velocity and acceleration of the joint jaw and tongue biomechanical system). As an application example, it is shown that the probability density function associated to these kinematic variables is more sensitive than classical features as Vowel Space Area (VSA) or Formant Centralization Ratio (FCR) in characterizing neuromotor degeneration in Parkinson's Disease.

Appropriate treatment planning method for field joint dose in total body irradiation using helical tomotherapy

Total body irradiation (TBI) using helical tomotherapy (HT) has advantages over the standard linear accelerator-based approach to the conditioning regimen for hematopoietic cell transplantation. However, the radiation field has to be divided into two independent irradiation plans to deliver a homogeneous dose to the whole body. A clinical target volume near the skin increases the skin surface dose; therefore, high- or low-dose regions arise depending on the set-up position accuracy because the two radiation fields are somewhat overlapped or separated. We aimed to determine an adequate treatment planning method robust to the set-up accuracy for the field joint dose distribution using HT-TBI. We calculated treatment plans reducing target volumes at the interface between the upper and lower body irradiations and evaluated these joint dose distributions via simulation and experimental studies. Target volumes used for the optimization calculation were reduced by 0, 0.5, 1.0, 2.0, 2.5, and 3.0 cm from the boundary surface on the upper and lower sides. Combined dose distributions with set-up error simulated by modifying coordinate positions were investigated to find the optimal planning method. In the ideal set-up position, the target volume without a gap area caused field junctional doses of up to approximately 200%; therefore, target volumes reduced by 2.0–3.0 cm could suppress the maximum dose to within 150%. However, with set-up error, high-dose areas exceeding 150% and low-dose areas below 100% were found with 2.0 and 3.0 cm target volume reduction. Using the dynamic jaw (DJ) system, dose deviations caused by set-up error reached approximately 20%, which is not suitable for HT-TBI. Moreover, these dose distributions can be easily adjusted when combined with the intensity modulation technique for field boundary regions. The results of a simulation and experimental study using a film dosimetry were almost identical, which indicated that reducing the target volume at the field boundary surface by 2.5 cm produces the most appropriate target definition.

Relative trajectory-driven virtual dynamic occlusal adjustment for dental restorations.

The abnormal occlusal contact can disrupt the coordination and health of the oral jaw system. Therefore, the dynamic adjustment of the occlusal surface is of great significance for assessing the status of occlusal contact and clarifying jaw factors of stomatognathic system diseases. To solve this problem, a trajectory subtraction algorithm based on screw theory to improve the accuracy of the occlusal movement trajectory is proposed in our paper. Driving by the relative trajectory, a virtual dynamic occlusal adjustment system is developed to realize 3D occlusal movement simulating, automatic occluding relation detection, and automatic occlusal adjustment. Furthermore, we adapt an active occlusal adjustment method based on Laplacian deformation to increase the contact areas of the occlusal surface, which can aid dentists to realize the automatic adjustment of the non-interference regions. As a consequence, the proposed subtraction algorithm is feasible and the root-mean-square is 0.097mm, and the adjusted occlusal surface is more consistent with the natural occlusal morphology. Graphical abstract ᅟ.

THE PREVALENCE OF PERIODONTAL TISSUE DISEASES IN YOUNG INDIVIDUALS ON THE BACKGROUND OF CROWDED TEETH

The abnormalities of maxillodental system take one of the leading places among diseases of the maxillofacial area. Thus, they are diagnosed more than in 50% cases among the younger population and in 30% cases among the adult population. 
 Most often, there are prerequisites for the incorrect position of individual teeth: anomalies are formed at the genetic level because of heredity of pathologies of size, amount, shape of teeth and size of the jaw bones of the facial skeleton. If the position of the teeth is incorrect, the periodontium retains the occlusal load of the functional injury.
 Therefore, the aim of our research was to study the prevalence of periodontal tissue diseases in young individuals on the background of crowded teeth.
 The material and research methods. The study was conducted on the base of Dental Center of Danylo Galytsky Lviv National Medical University during 2015−2017 years. 1146 people at the age from 18 to 44 years were examined. Every participant of research underwent general dental examination, as well as a special examination aimed at clarification of orthodontic treatment. The diagnosis of periodontal tissue diseases was made according to the classification of N. F. Danilevskyi and was determined using paraclinical indicators. The obtained results were worked out statistically using functions of MS Excel and Statistica 6.
 Results of the research and their discussion. The total number of the examined with orthodontic pathology was found on average in 77.24% of patients (885 people). At the same time, abnormalities of dental jaw system were not detected in about 261 (22.76%) of the examined.
 As a result of the conducted studies we found that among the examined without dental jaw abnormalities 38.89±.,32% of patients had intact periodontium, that was 1.6 times more for data in individuals with crowding − 23.73±2.00, p<0.01. At the same time, in patients of the main group the prevalence of periodontal tissue diseases was 1.2 times higher than in the examined of the comparative group (76.27±2.00% against 61.11±3.32%, respectively, p<0.01).
 It should be noted, that with the increase of the age of patients the prevalence of periodontal tissue diseases increased in both study groups, but in patients with crowded teeth this tendency was more pronounced. So, in the younger age group in patients with crowding the prevalence of periodontal diseases was 1.5 times higher in relation to the data of their peers from the comparison group (71.37±3.00% vs. 46.99±5.48%, p<0.01). In 27−35-year-old patients the prevalence of periodontal tissue diseases amounted to 72.38±4.03% of the examined of the main group and 65.62±5.94% of the examined of the comparison group, but the obtained data were not statistically significant, p>0.05. At the same time, in the patients of the main group aged 36−44 years the prevalence of periodontal tissue diseases was maximal and exceeded the value of their peers in the comparison group by 1.2 times (92.08±2.69% vs. 73.91±5.29%, respectively, p<0.01).
 The analysis of the obtained data allowed to assert that on average crowding of teeth on the upper jaw was found in 237 patients (52.55%) and on the lower jaw in 214 patients (47.45%).
 Thus, the maximum frequency of crowded teeth on the upper jaw was observed in the examined in the age range of 27−35 years, 60.16±4.41% of patients, with the minimum prevalence of this pathology in the youngest group (18−26 years), 49.34±4, 72%.
 The analysis of diagnostic structure of periodontal tissue diseases showed that inflammatory diseases of periodontal tissues (gingivitis, localized periodontitis) were found in patients with crowded teeth, on average 1.2 times more often than in patients without orthodontic pathology (42.42±1.88% vs. 36.33±3.54%, respectively, p<0.05).
 Conclusions. Thus, as a result of the conducted studies, higher prevalence of periodontal tissue diseases was proved in patients with crowding of teeth, which made progress in increasing the age of the examined than in patients without orthodontic pathology.

A method for preventive intervention regarding temporomandibular pain and dysfunction

Objective: Adolescent girls frequently suffer from temporomandibular disorder (TMD) symptoms and associated headache. A program aimed at informing about risk behavior for TMD symptoms, how to influence harmful habits and about general relaxation was tested.Material and methods: Eighty girls at two high schools, 16 years of age, with or without symptoms, were invited to the health information on two occasions and 60 girls participated. Firstly, a questionnaire regarding symptoms and oral parafunctional habits was administrated. Structured information was given about the normal anatomy and function of muscles and joints, about the occlusion, oral habits and symptoms of orofacial pain/dysfunction and headache. General relaxation was instructed and trained. At a three-month follow-up, the same questionnaire regarding symptoms as at baseline was completed.Result: The information provided was perceived as useful and instructive. At the follow-up, 77% reported that they used what they had learned. Headache once a week or more decreased from 49% at baseline to 35% and headache ‘never/rarely’ changed from 11% to 25% (p = .002). Reported joint sounds had decreased by the follow-up (p = .053), as had the use of chewing gum (p = .002). A majority of the girls suggested that the information should be scheduled during school hours.Conclusion: Health information about the jaw system can influence risk factors for TMD symptoms and the frequency of symptoms among adolescent girls.

Dynamic modeling and CPG-based trajectory generation for a masticatory rehab robot

Human mastication is a complex and rhythmic biomechanical process which is regulated by a brain stem central pattern generator (CPG). Masticatory patterns, frequency and amplitude of mastication are different from person to person and significantly depend on food properties. The central nervous system controls the activity of muscles to produce smooth transitions between different movements. Therefore, to rehab human mandibular system, there is a real need to use the concept of CPG for development of a new methodology in jaw exercises and to help jaw movements recovery. This paper proposes a novel method for real-time trajectory generation of a mastication rehab robot. The proposed method combines several methods and concepts including kinematics, dynamics, trajectory generation and CPG. The purpose of this article is to provide a methodology to enable physiotherapists to perform the human jaw rehabilitation. In this paper, the robotic setup includes two Gough–Stewart platforms. The first platform is used as the rehab robot, while the second one is used to model the human jaw system. Once the modeling is completed, the second robot will be replaced by an actual patient for the selected physiotherapy. Gibbs–Appell’s formulation is used to obtain the dynamics equations of the rehab robot. Then, a method based on the Fourier series is employed to tune parameters of the CPG. It is shown that changes in leg lengths, due to the online changes of the mastication parameters, occur in a smooth and continuous manner. The key feature of the proposed method, when applied to human mastication, is its ability to adapt to the environment and change the chewing pattern in real-time parameters, such as amplitudes as well as jaw movements velocity during mastication.

Realistic kinetic loading of the jaw system during single chewing cycles: a finite element study.

Although knowledge of short-range kinetic interactions between antagonistic teeth during mastication is of essential importance for ensuring interference-free fixed dental reconstructions, little information is available. In this study, the forces on and displacements of the teeth during kinetic molar biting simulating the power stroke of a chewing cycle were investigated by use of a finite-element model that included all the essential components of the human masticatory system, including an elastic food bolus. We hypothesised that the model can approximate the loading characteristics of the dentition found in previous experimental studies. The simulation was a transient analysis, that is, it considered the dynamic behaviour of the jaw. In particular, the reaction forces on the teeth and joints arose from contact, rather than nodal forces or constraints. To compute displacements of the teeth, the periodontal ligament (PDL) was modelled by use of an Ogden material model calibrated on the basis of results obtained in previous experiments. During the initial holding phase of the power stroke, bite forces were aligned with the roots of the molars until substantial deformation of the bolus occurred. The forces tilted the molars in the bucco-lingual and mesio-distal directions, but as the intrusive force increased the teeth returned to their initial configuration. The Ogden material model used for the PDL enabled accurate prediction of the displacements observed in experimental tests. In conclusion, the comprehensive kinetic finite element model reproduced the kinematic and loading characteristics of previous experimental investigations.

Effectiveness of Trial Root Canal Model and Dedicated Jaw System for Objective Evaluation of the Root Canal Filling Method

Effectiveness of Trial Root Canal Model and Dedicated Jaw System for Objective Evaluation of the Root Canal Filling Method

Towards an SEMG-based tele-operated robot for masticatory rehabilitation

This paper proposes a real-time trajectory generation for a masticatory rehabilitation robot based on surface electromyography (SEMG) signals. We used two Gough-Stewart robots. The first robot was used as a rehabilitation robot while the second robot was developed to model the human jaw system. The legs of the rehabilitation robot were controlled by the SEMG signals of a tele-operator to reproduce the masticatory motion in the human jaw, supposedly mounted on the moving platform, through predicting the location of a reference point. Actual jaw motions and the SEMG signals from the masticatory muscles were recorded and used as output and input, respectively. Three different methods, namely time-delayed neural networks, time delayed fast orthogonal search, and time-delayed Laguerre expansion technique, were employed and compared to predict the kinematic parameters. The optimal model structures as well as the input delays were obtained for each model and each subject through a genetic algorithm. Equations of motion were obtained by the virtual work method. Fuzzy method was employed to develop a fuzzy impedance controller. Moreover, a jaw model was developed to demonstrate the time-varying behavior of the muscle lengths during the rehabilitation process. The three modeling methods were capable of providing reasonably accurate estimations of the kinematic parameters, although the accuracy and training/validation speed of time-delayed fast orthogonal search were higher than those of the other two aforementioned methods. Also, during a simulation study, the fuzzy impedance scheme proved successful in controlling the moving platform for the accurate navigation of the reference point in the desired trajectory. SEMG has been widely used as a control command for prostheses and exoskeleton robots. However, in the current study by employing the proposed rehabilitation robot the complete continuous profile of the clenching motion was reproduced in the sagittal plane.

고 에너지 X선 방사선치료 시 Flattening Filter와 Tracking Jaw 사용에 따른 광중성자 발생 평가

방사선치료는 의료용 선형가속기를 이용하는 방식이 가장 많이 적용되고 있으며 사용되는 광자선도 고 에너지화 되고 있다. 최근에 도입되는 선형가속기에는 선속평탄 여과판을 사용하지 않는 3F 방식과 조사중에 조사야에 맞춰 jaw가 움직이는 tracking jaw 기술이 적용되어 임상에 보급되고 있다. 이에 본 연구는 선형가속기를 이용한 고에너지 X선 조사 시 선속평탄 여과판 사용 유무에 따른 광중성자 발생과, tracking ja w 사용에 따른 광중성자 발생을 측정하여 비교분석하였다. 그 결과 3F 방식이 선속평탄 여과판의 적용에 비하여 광중성자의 검출이 약 70% 낮게 나타났으며, tracking jaw 방식은 static jaw에 비하여 약 83% 높게 광중성자가 발생하는 것으로 나타났다. Radiation therapy is usually using linear accelerator and used X-ray energy is also getting higher. Recently linear accelerators has been developed 3F mode and tracking jaw technology and that was applied for patient therapy. This study aims at measuring photoneutrons depending on the use of 3F and tracking jaw system when radiation is irradiated using a linear accelerator. The generation of photoneutrons of 3F system was 70% smaller than 2F system and that of tracking jaw system was 83% higher than static jaw system. Photoneutron value is relatively low. However, it must be minimized for Photoneutron exposure during radiation therapy.