Changes in chewing patterns after implantation in the edentulous mandible

Almost all edentulous patients with implant-supported prostheses in mandibles describe an improvement in their chewing function and quality of life. This was reason to believe that an implant prosthetic treatment actually influences mandibular border movements, as well as the chewing patterns. The present study compares border movements and chewing patterns in 15 patients recorded with the Sirognathograph. The first measurements were made with existing complete dentures. After implantation and rehabilitation with a Dolder-bar and clip-to-bar overdenture, the movements were recorded again. The measurements revealed an improved guidance of the mandibular movements and larger borderline patterns following stabilization of the complete denture with the bar. This leads to more harmonic shapes in the movements and better chewing efficiency.     

Myosin heavy chain transitions during development. Functional implications for the respiratory musculature

The myosin heavy chain (MHC) exists as multiple isoforms that are encoded for by a family of genes. The respiratory musculature demonstrates muscle-specific and temporally-dependent changes in MHC isoform expression during maturation. Developmental expression of MHC isoforms correlate well with postnatal changes in actomyosin ATPase activity, specific force generation (P0/CSA), maximum unloaded velocity of shortening (V0) and and fatigue resistance. More specifically, as the expression of MHCneonatal declines and MHC2A, MHC2X, and MHC2B increase, actomyosin ATPase activity, P0/CSA, V0, and muscle fatigability increase. The increase in actomyosin ATPase activity with maturation is partially offset by a postnatal increase in oxidative capacity; however, as fatigue resistance declines with development it is apparent that the energy costs of contraction are not fully matched by an increase in energy production. Developmental transitions in smooth muscle MHC phenotype also occur although their functional importance remains unclear.     

On densification and shape change during hot isostatic pressing

When the temperature of a powder compact is raised, heat diffuses inwards from the surface. If the compact is under pressure (as it is during HIPing), the surface layers start to densify, increasing the local thermal conductivity. Under certain conditions a densification front then propagates into the powder, and this leads to changes of shape of the compact, which is no longer identical to the preform shape. The conditions which lead to non-uniform densification are analysed and the consequences are discussed, and compared with experiments.     

Okadaic acid induces marked shape change of human platelets

Okadaic acid (OA) induced marked shape changes of human platelets but neither granule secretion nor increase in [Ca2+]i occurred. Morphological changes induced by OA were unique and different from those observed with thrombin mainly in two respects. One is that the pseudopods formed by OA treatment were longer and straighter than those by thrombin. The other is that no granule centralization was observed with OA-treatment, although central condensation of cytofilaments was observed as was with thrombin. The immunocytochemical analysis employing anti-myosin antibody revealed that myosin was distributed in the elongated pseudopods. Since OA induced phosphorylation of the 20-kDa myosin light chain (MLC20) corresponding to the change in shape of platelets but did not induce phosphorylation of the 47-kDa protein (pleckstrin) (Higashihara M. et al. FEBS Lett. 307:206-210, 1992), these results suggest that phosphorylation of MLC20 plays an important role in OA-induced unique morphological changes of platelets.     

Modifications of platelet shape change and ATP release during cardiopulmonary bypass

Platelet activation is accompanied by characteristic morphological changes: smooth-disc platelets become more spherical in shape and develop psudopods. The purpose of this study is to investigate whether platelets change after extracorporeal bypass. Twenty-two patients undergoing cardiopulmonary bypass (CPB) were studied prior to anesthesia and immediately after the operation. Platelets activated by different agonists were monitored simultaneously for morphological changes, ATP release and aggregation. While shape change measured before surgery was large, it was significantly reduced after bypass surgery (p < 0.01); morphological changes were quicker postoperatively. Several other parameters also changed: the time lapse between administration of the agonist and the start of ATP secretion decrease significantly (p < 0.01). After activation with high concentrations of ADP, ATP release was significantly increased (p < 0.01). On the other hand, less ATP was released after platelet activation with collagen and arachidonic acid, suggesting a change in platelet adhesion or a downregulation of endoperoxide synthesis. In our study, the importance of preactivation change in shape, estimated quantitatively by percent loss in ability of changing shape, can be compared using various agonists, with proportional defects in release and aggregation. These data provide evidence for different intrinsic levels in platelet defects after CPB.     

Functional morphology of the masticatory musculature of the rodent subfamily microtinae

Voles and lemmings are the most successful group of graminivorous rodents, but the adaptations allowing them to enter this niche are not fully known. Dissections of the masticatory musculature of the 12 genera and subgenera of North American microtines show an increase in the potential anterior vector component and in the potential vertical vector component of these muscles relative to the molar tooth row. The result is a separation of the compressive and propulsive functions of the masticatory muscles during the power stroke of mastication. This has led to the formulation of a propalinal "swing" hypothesis which is supported by vector analyses of the musculature.     

Biomechanics of torsion in the human mandible

Staff competence in the application of behavioral techniques is critical to improve quality of life for persons with a developmental disability. Development of efficient staff training programs is therefore of great importance. This paper describes some of the procedures most frequently used in staff training research. Research in this area is reviewed in relation to client outcomes as a function of staff training, maintenance of staff skills, and transfer of staff skills across settings, clients, and programs. Current concerns and further improvements in behavioural techniques, acquisitional strategies, and assessment are discussed.     

Densification and change in the shape of a hollow porous cylinder during hot compression in a container

Conclusions The compression of a porous ring in a container can be arbitrarily divided into two stages: Initially, densification predominates over shape change, but, when the porosity decreases to 3–6%, the rate of radial deformation sharply rises, and at 1% the cavity closes up. With increasing value of R_e/R_i at any given porosity the intensity of densification grows and the rate of radial deformation falls. There is a discrepancy of not more than 15% between experimental and theoretical data, which means that the theoretical model adopted is sufficiently accurate and can be employed for calculating the process of hot compression of a porous ring in a container.Translated from Poroshkovaya Metallurgiya, No. 3(279), pp. 14–16, March, 1986.     

Time dependence of internal friction and shape change in Cu-Zn-Al shape memory alloys

The time evolution of internal friction and shape change in different microstructural states of two Cu-Zn-AI shape memory alloys has been investigated. In the single-martensite phase state, the monotonic decrease of internal friction with time is attributed to the pinning of martensite/ martensite interfaces. When the parent phase is present, the change in the internal friction is associated with the formation of stress-induced martensite and the subsequent pinning of the martensite/parent and martensite/martensite interfaces.     

A study of preferred orientation of martensite and shape change during phase transformation in Cu-Al-Ni-Mn alloy

The metallography, stress, electric resistance and temperature in Cu-12Al-5Ni-3Mn mass % alloy have been measured simultaneously during the direct and inverse martensitic transformation. The preferred orientation of martensite in a hot-rolled sample is along the rolling direction. When the sample is cooled under a tensile stress from a high temperature (>A_f) to room temperature (< M_f), the preferred orientation of martensite is along the direction which has an angle of 45° to the direction of tensile stress. On cooling, the orientation of some secondary martensite has an angle of 45° with the primary martensite. The shift of zero point of the internal friction torsion pendulum i.3. the shape change during martensitic transformation is discussed in terms of the preferred orientation of martensite.     

Functional units, chewing, swallowing, and food avoidance among the elderly

Chagas' disease is caused by the hemoflagellate protozoan Trypanosoma cruzi, which is predominantly found in South and Central America and Mexico. Although the parasite is present in the United States, confirmed cases of human disease are rare. The most serious manifestation of chronic Chagas' disease is a progressive inflammatory cardiomyopathy. However, T. cruzi has not been consistently demonstrated with histologic techniques in inflammatory cardiac lesions. In this study, we used both polymerase chain reaction (PCR) amplification of extracted DNA from hematoxylin and eosin-stained tissue scrapings, and in situ hybridization to detect the presence of T. cruzi in infected murine cardiac tissue sections. Three T. cruzi-specific DNA sequences were used: a 122-basepair (bp) sequence localized within the minicircle network (MCS), a 188-bp nuclear repetitive sequence (RS), and a 177-bp sequence within the open reading frame of a gene coding for a flagellar protein (FPS). We found that all three sequences are amplifiable from scrapings of murine cardiac tissue. The MCS and RS are detected at 0.167 and 0.24 amastigote DNA equivalents, while FPS is barely detected at 0.24 amastigote DNA equivalents. On the other hand, in situ hybridization with all three sequences allowed for the detection of T. cruzi amastigotes within the tissue. The MCS and FPS, however, consistently yielded a more intense signal. These results indicate that PCR and in situ hybridization may prove useful in establishing the prevalence of T. cruzi in human chagasic cardiomyopathy.     

Pathomorphology of the skeletal musculature of swine dying during transportation

Pathomorphological studies were conducted into seven different muscles of 50 pigs that had died on transport to slaughterhouses. Established was the following percentual presence of acute disseminated hyaline-plaque degeneration and necrosis of muscle fibres: Group 1 with high frequency of pathological findings: M. biceps femoris, bright portion positively affected in 72 per cent of all cases, dark portion in 68 per cent; M. semimembranosus affected in 64 per cent; M. longissimus dorsi affected in 56 per cent. Group 2 with low to medium frequency of pathological findings: M. Quadriceps femoris affected in 26 per cent; M. semitendinosus, bright portion affected in 26 per cent, dark portion in 16 per cent; M. psoas major affected in 18 per cent. Group 3 without myopathy frequency: M. masseter. The rare occurrence of resorptive myositis (between zero and six per cent of all cases, depending on affected muscles) seems to confirm the young age of that myopathy which usually develops only under transport stress. Hyaline transverse ligaments (supercontractures) were not observed at all in the context of transport deaths (M. longissimus dorsi, M. biceps femoris--bright portion, M. semitendinosus--bright portion, M. masseter) or only in rare cases (M. quadriceps femoris in two per cent of all cases, M. semimembranosus in six per cent, M. semitendinosus--dark portion in six per cent, M. biceps femoris in 18 per cent, M. psoas major in 24 per cent). A comparison with earlier results on the frequency of muscle damage showed that hyaline-plaque degeneration and necrosis of muscle fibres occurred much more often in the context of normal slaughter without any transport and with much graver severity following different modes of transport. These conclusions and results are all relating to pigs which died on transport. The results are discussed, with reference to aetiology and pathogenesis of myopathies in swine caused by stress.     

Control of human jaw elevator muscle activity during simulated chewing with varying bolus size

During chewing, a small part of the observed muscle activity is needed for the basic open-close movements of the mandible, and additional muscle activity (AMA) is needed to overcome the resistance of the food. The AMA consists of two contributions: a large peripherally induced contribution, starting after food contact and a small anticipating contribution, starting before food contact. We investigated whether the latencies of these contributions depend on the expected or actual bolus size. Subjects made rhythmic open-close movements near their natural chewing frequency controlled by a metronome. This frequency was determined while the subjects were chewing gum. Food resistance was simulated by an external force, acting on the jaw in a downward direction during part of the closing movement. Bolus size was simulated by the jaw gape at which the force started. Jaw movement and surface EMG of the masseter and anterior temporal muscles on both sides and the suprahyoid muscles were recorded during experiments in which the jaw gape at which the force started was varied. The peripherally induced contribution to the AMA started about 20 ms after the onset of the force, irrespective of the jaw gape at which the force started. It is concluded that the onset of this contribution depends solely on food contact in the actual cycle. The function of the observed mechanism for jaw elevator muscle control may be to enable a highly automatic control of the muscle activity required to overcome the resistance of food of different hardness and different size. The onset of the anticipating contribution to the AMA showed neither a relationship with the actual jaw gape at which force onset occurred nor with the expected jaw gape of force onset. It is suggested that the onset of the anticipating AMA is related to the jaw gape at the onset of closing. The function of this contribution may be the regulation of the mechanical response of the jaw after an expected disturbance of the closing movement by food contact, by tuning the muscle stiffness to the expected hardness of the food.     

Histopathology and ultrastructural changes of the musculature and nerves during methamidophos toxication in chicken

Primary mediastinal leiomyosarcomas are malignant sarcomas with unknown etiology not deriving from the smooth muscle fiber of the esophagus, trachea or main vessels. Very few cases have been reported in the literature and, although they are clinically unspecific, their histology is unique. The case described here is a 66-year-old woman with a leiomyosarcoma localized at the medium and posterior mediastinum, clinically presented as a mediastinal emergency.     

Electromyographic activity of the cervical musculature during dynamic lateral bending

STUDY DESIGN: Electromyographic profiles from the neck muscles of five young, healthy men were obtained to study the muscular, activation patterns during dynamic external loading. OBJECTIVES: To examine the myoelectric activity of selected cervical muscles during dynamic loading, and to explore the reaction of the cervical muscles to different loading conditions. SUMMARY OF BACKGROUND DATA: The response of cervical muscles throughout dynamic external loading is not well understood. Electromyography provides information, within certain limitations, about the neural drive to various components of the musculature. Such information on activation, combined with geometric parameters of the musculoskeletal tissues, constitutes a tool for helping to understand the mechanism of head and neck impact-related injury. METHODS: Subjects were tested with the head and neck in the neutral and prebent positions. Dynamic loads were applied laterally to each subject by free-falling masses to create peak dynamic loads ranging from about 40 to 100 N. Force and electromyographic data were recorded, and cross-correlations from linear envelope electromyography were calculated. RESULTS: The peak electromyogram showed large differences between the two applied loads and between subjects. There were time delays (75-165 msec) between the peak applied force and the peak electromyogram. The muscles on the contralateral side demonstrated different electromyographic profiles between subjects. Within subjects, the electromyographic profiles from each muscle were consistent for the same trial conditions. CONCLUSIONS: Electromyographic profiles and the cross-correlator coefficients for cervical muscles have shown reproducible intrasubject muscle synergies, which were not sensitive to the magnitude of applied load and the posture of the head. Intersubject muscle activity patterns varied.     

Distraction osteogenesis of the mandible using a submerged intraoral device: a report of three cases

OBJECTIVE: To compare the value of current transthoracic echocardiographic systems and transoesophageal echocardiography for assessing left atrial appendage function and imaging thrombi. DESIGN: Single blind prospective study. Patients were first investigated by transthoracic echocardiography and thereafter by a second investigator using transoesophageal echocardiography. The feasibility of imaging the left atrial appendage, recording its velocities, and identifying thrombi within the appendage were determined by both methods. PATIENTS: 117 consecutive patients with a stroke or transient neurological deficit. SETTING: Tertiary cardiac and neurological care centre. RESULTS: Imaging of the complete appendage was feasible in 75% of the patients by transthoracic echocardiography and in 95% by transoesophageal echocardiography. Both methods were concordant for the detection of thrombi in 10 cases. Transoesophageal echocardiography revealed two additional thrombi. In one of these patients, transthoracic echocardiography was not feasible and in the other the thrombus had been missed by transthoracic examination. In patients with adequate transthoracic echogenicity, the specificity and sensitivity of detecting left atrial appendage thrombi were 100% and 91%, respectively. Recording of left atrial appendage velocities by transthoracic echocardiography was feasible in 69% of cases. None of the patients with a velocity > 0.3 m/s had left atrial appendage thrombi. In the one patient in whom transthoracic echocardiographic evaluation missed a left atrial appendage thrombus, the peak emptying velocity of the left atrial appendage was 0.25 m/s. CONCLUSIONS: A new generation echocardiographic system allows for the transthoracic detection of left atrial appendage thrombi and accurate determination of left atrial appendage function in most patients with a neurological deficit.     

Evaluation of the mechanical environment during distraction osteogenesis

Physical forces have been hypothesized to direct the process of bone regeneration during distraction osteogenesis. However, despite significant clinical experience, relatively little is known about how the mechanics of distraction influence bone formation. This study investigated net fixator forces and strains in the distraction callus during bilateral lengthening of tibiae in New Zealand White rabbits. Distractions yielded a classic viscoelastic response with a sharp increase in fixator force, followed immediately by significant relaxation. Tension acting on mesenchymal gap tissue caused by distraction was estimated to reach more than 30 N by the time full lengthening was achieved. Average maximum cyclic strains within the distraction zone during ambulation were estimated to be 14% to 15% and supported by the results of fluoroscopic imaging. Paradigms for fracture healing have hypothesized that such strains are incompatible with new bone formation. The documented clinical success of distraction osteogenesis at stimulating large volumes of new bone suggests that other mechanisms that warrant additional investigation may be at work during distraction.     

Radiographic patterns of osteomyelitis in the mandible. Plain film/CT correlation

Mandibular osteomyelitis often is associated with involvement of the masticator space. Assessment of mandibular osteomyelitis should therefore involve assessment of soft tissue involvement of the lesion. The purpose of this study was to clarify the relationship between computed tomography patterns and the presence of inflammation in soft tissues. Thirty-three cases diagnosed with osteomyelitis of the mandible were analyzed radiologically with conventional radiographs and with computed tomography scans. Computed tomography patterns of osteomyelitis were classified into four types, lytic, mixed, sclerotic, and sequestrum patterns. Location, extent of the lesion, and change of the cortical plate were evaluated and compared with conventional radiographic findings. Mixed pattern cases displayed diffuse bone abnormalities, which sometimes were accompanied by cortical plate disruption and periosteal reaction. In addition, most mixed pattern cases showed soft tissue involvement, especially of the masseter muscle. Inflammation of the masseter muscle was found to be related to periosteal reaction and disruption of the buccal cortical plate. The data demonstrate a close interaction between cortical plate disruption and muscle inflammation. The extent of inflammation including soft tissue involvement was better appreciated with computed tomography in osteomyelitis, especially in mixed pattern cases.