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Biomedical subjects

F Bosman

Publications and source records attributed to F Bosman.

At least 109 records · Page 6Linked to original sources
PubMed1992

Force-deformation properties of artificial and natural foods for testing chewing efficiency.

The force-deformation characteristics of two artificial test foods (Optosil and Optocal) for measurements of food comminution during mastication were investigated in a bite simulator and compared with those of carrots and peanuts. The influence of cusp geometry was evaluated by use of a flat plate and three cusp forms. The forces at the yield point were lower for Optocal than for Optosil artificial test food. The forces needed for Optocal overlapped those needed for carrots and peanuts. The natural foods showed more variation in the force and percentage of deformation at the yield point than the artificial foods. The artificial foods reflected the differences in cusp form better than did the natural foods. The use of artificial foods fulfills a need for standardization and warrants consideration in studies of mastication.

Analysis of Variance↗
PubMed1992

Stress distribution around dental implants: influence of superstructure, length of implants, and height of mandible.

The stress distribution around dental implants was investigated by use of a two-dimensional model of the mandible with two implants. A vertical load of 100 N was imposed on abutments or the bar connection. The stress was calculated for a number of superstructures under different loading conditions with the help of the finite element method. The length of the implants and the height of the mandible were also varied. A model with solitary abutments showed a more uniform distribution of the stress when compared with a model with connected abutments. The largest compressive stress was also less in the model without the bar. Using shorter implants did not have a large influence on the stress around the implants. When the height of the mandible was reduced, a substantially larger stress was found in the bone around the implants because of a larger overall deformation of the lower jaw.

Bite Force↗
PubMed1992

Masticatory ability, denture quality, and oral conditions in edentulous subjects.

This study investigated the relationships between the ability of 38 patients with complete dentures to comminute a tough artificial test food and their answers to questions about the chewing experience. Also, clinical assessments were made of denture quality and oral conditions. Significant but weak relationships were found between the ability to comminute the test food and the subjective chewing experience as well as the degree of resorption of the mandibular residual ridge. Masticatory ability is conceivably determined by many other factors as well. Results indicate that dentists cannot rely on asking denture wearers about chewing problems and clinical responses with respect to oral conditions and denture quality for predicting those patients' masticatory abilities. The ability of wearers of complete dentures to comminute tough foods should be determined individually by a series of chewing tests.

Adult↗
PubMed1992

Standardized radiographs of the alveolar crest around implants in the mandible.

The techniques currently used for standardized longitudinal radiographic evaluation of the supporting bone around dental implants are not suitable for general application. An aiming device is described for intraoral radiography used to evaluate the crestal bone height around dental implants used as retention for overdentures. This aiming device has been tested on four different implant systems by four dentists. Error analysis of serial radiographs indicates small deviations in reproducibility. It is concluded that this method is suitable for routine evaluation of dental implants.

Alveolar Process↗
PubMed1992

Electromyographic parameters related to clenching level and jaw-jerk reflex in patients with a simple type of myogenous cranio-mandibular disorder.

A discriminant analysis has been applied on several electromyographic (EMG) parameters of the masseter and the anterior temporal muscles, related to clenching and the jaw-jerk reflex, to characterize jaw muscle function of patients with craniomandibular disorder (CMD) with respect to controls. The subject samples, matched for age, consisted of 20 females with myogenous CMD, and 20 symptom-free females. The jaw-jerk reflex was elicited by a downward-directed mandibular load, transmitted by a bite-fork causing a similar occlusion and bite-rise as a splint. The patients differed mainly from the controls by smaller maximum EMG activity in both muscle groups (P less than 0.05 with the bite-fork inserted). This finding was related to a smaller muscle strength as the EMG level did not improve with pain-free jaw muscles after therapy using a relaxation splint. Discriminating factors of secondary importance were an enhanced bilateral asymmetry in the muscle activity of the patients, and in the reflex amplitude normalized for background EMG activity. In all subject samples, the activity of the anterior temporal muscles decreased with respect to the masseter muscles when the bite-fork was inserted (P less than 0.05-0.001). The therapeutic effect of a relaxation splint may, in part, be related to a relief of the temporal muscles.

Adult↗
PubMed1992

Peripherally induced and anticipating elevator muscle activity during simulated chewing in humans.

1. During chewing, little muscle activity is required to make open-close movements with the mandible, and much additional muscle activity (AMA) of the closing muscles is needed to overcome the resistance of food. The neuromuscular control of the AMA was investigated. 2. Subjects made rhythmic open-close movements at their natural chewing frequency controlled by a metronome. Food resistance was simulated by an external force, acting on the jaw in a downward direction during part of the closing movement. Sequences of cycles with a force were unexpectedly alternated with sequences of cycles without a force. Jaw movement, and surface electromyograph (EMG) of the masseter, temporalis, and digastric muscles on both sides were recorded during cycles before and after the transition from force to no force (Disappear experiment) and vice versa (Appear experiment). 3. The movement trajectory of the second and following cycles after the transition from force to no force or vice versa were similar. Thus adaptation to the changed circumstances occurred in both types of experiments within two open-close cycles. 4. In the first cycle with force in the Appear experiments, the AMA started, on average, 129 ms after the onset of the force. In all other cycles with force, the AMA started, on average, 70 ms before the onset of the force at a low level and steeply increased 23 ms after the onset of the force. 5. In the first cycle without force in the Disappear experiments, the AMA started, on average, 69 ms before the moment at which the force would have started. However, the large contribution to the AMA had disappeared.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Control of elevator muscle activity during simulated chewing with varying food resistance in humans.

1. During chewing, a small part of the observed muscle activity is needed for the basic open-close movements of the mandible, and much additional muscle activity (AMA) is needed to overcome the resistance of the food. In chewing cycles in which a counteracting force is expected, the AMA is mainly generated by peripheral induction with a latency of approximately 23 ms. It was investigated whether an open-loop or closed-loop mechanism is involved in the control of the AMA in these cycles. 2. Subjects made rhythmic open-close movements at their natural chewing frequency controlled by a metronome. Food resistance was simulated by an external force, acting on the jaw in a downward direction during part of the closing movement. Sequences of cycles with a force were unexpectedly alternated with sequences of cycles with a different force. The force changed from 19 to 0 N and vice versa, and from 25 to 6 N and vice versa. Jaw movement and surface electromyogram of the masseter, temporalis, and suprahyoid muscles on both sides were recorded during cycles before and after the transition from one force condition to another. 3. The movement trajectory and AMA of the second and following cycles with a new force appeared to be similar. Thus adaptation to the changed circumstances occurred within two open-close cycles. 4. In the first cycle with 0 or 6 N in the 19----0 N and 25----6 N experiments respectively, a large part of the AMA had disappeared. The AMA in this cycle started to differ from the AMA in the previous cycle approximately 23 ms after the moment the force in this cycle started to differ from the previous cycle. 5. In the first cycle with 19 or 25 N in the reverse experiments, the AMA increased 120-136 ms after the moment the force in this cycle started to differ from the previous cycle. 6. During the closing phase of each open-close cycle, no muscle activity of the suprahyoid muscles was observed; thus co-contraction with the elevator muscles did not occur. 7. It was concluded that the AMA is under control of a closed-loop mechanism with a latency of approximately 23 ms. However, the reflex output has a maximum, depending on information about the food resistance gained in previous cycles.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Comminution of food by complete-denture wearers.

A method for quantifying the comminution of an artificial test food (Optosil) was evaluated with respect to its suitability for measurements of masticatory performance in complete-denture wearers. Reference was made to subjects with natural dentitions. The description of particle size distributions generated by complete-denture wearers by a Rosin-Rammler equation was subject to limitations, due to the presence of large proportions of almost-intact particles, which had hardly been damaged or broken during chewing. This finding might be explained by: (i) the relatively high fracture strength of Optosil as compared with natural foods; and (ii) the limitations of complete-denture wearers in exerting bite forces. The particle size distributions obtained after repeated measurements and described by linear interpolation of data points were reproducible. In comparison with young adults with natural dentitions, the denture-wearers needed approximately seven times more chewing strokes to achieve an equivalent reduction in particle size.

Adult↗
PubMed1992

A computer simulation of the influence of selection and breakage of food on the chewing efficiency of human mastication.

The reduction of food particle sizes during mastication is considered to be the composite result of a selection and breakage process. The chance of a food particle being selected between the teeth was assumed to increase as a power function of the particle's size, whereas the breakage of food particles was described by a cumulative distribution function. The selection and breakage functions were combined with matrix algebra, resulting in a matrix model. By use of this model, particle-size distributions could be calculated after various numbers of chewing cycles. From these distributions, the decrease of the median particle size was determined as a function of the number of chewing cycles. The calculations were performed for various sets of physiologically relevant selection and breakage variables. The number of chewing cycles, N1/2, needed for the initial particle size to be halved was taken as an indication of chewing efficiency. This number varied approximately inversely with both the selection coefficient and the breakage variable. The initial particle size appeared to have the largest influence on N1/2. The theoretical results from the simulation study were also compared with data obtained from experiments on human chewing efficiency.

Computer Simulation↗
PubMed1991

A 46,XY female with mixed gonadal dysgenesis and a 48,XY, +7, +i(12p) chromosome pattern in a primary gonadal tumor.

Cytogenetic analysis of a primary germ-cell tumor originating from the streak gonad of a 20-year-old phenotypic female with a 46,XY karyotype and mixed gonadal dysgenesis revealed a 48,XY, +7, +i(12p) chromosomal pattern. Germ-cell tumors originating from gonads of normal males are usually highly aneuploid. An isochromosome 12p as well as an overrepresentation of chromosome 7 material are among the specific changes most consistently observed. The present case shows that tumors of dysgenetic gonads, albeit being near-diploid, may exhibit similar chromosomal changes. This observation lends additional support to the hypothesis that these specific cytogenetic anomalies may play an important role in the pathogenesis of human germ-cell tumors.

Adult↗
PubMed1991

The effect of particle size reduction on the jaw gape in human mastication.

Eight subjects participated in chewing experiments to examine how the jaw gape in consecutive chewing cycles depends on the dimensions and the volume of the food bolus. Different volumes of chewing-gum and a silicone rubber (Optosil) were used. The initial particle size of Optosil was also varied. With the aid of a sieving procedure, the size distribution of Optosil particles was determined after different numbers of chewing cycles. The maximum size of a chewing-gum bolus along three orthogonal axes was determined after a random number of chewing cycles for all the volumes of chewing-gum offered. The jaw gape was measured by means of an optical motion analysis system and calibrated at the level of the first molars. The maximum jaw gape and the gape at the first fall in mandibular velocity after the onset of jaw-closing were determined for different chewing cycles from the position signal and its time derivative. For each volume of chewing gum offered to the subject, the average of the maximum gapes attained in the subsequent cycles of jaw movement was related to the characteristic height of a bolus of that volume; maximum velocity of closing appeared to occur while the antagonistic teeth were already penetrating the gum bolus. The increase in the maximum jaw gape, the gape at the velocity maximum, and the height of the gum bolus, as a function of the volume of chewing-gum, could be well-described by a power function of the volume. The exponent of the power function for both jaw gapes was only slightly smaller than the exponent obtained for the bolus height.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

An animal model for therapeutic intervention studies of CMV infection in the immunocompromised host.

An experimental rat model to study acute cytomegalovirus infections is described. Eight-week old male Brown Norway rats, immunosuppressed by total body irradiation, were infected with rat cytomegalovirus (RCMV). The effects of infection were determined by survival rates and the presence of virus or viral components in different organs was assayed by plaque test, immunoperoxidase staining, dot-blot DNA hybridization and in situ DNA hybridization. At days 10-post infection nearly 90% of the animals had died. Spleen, liver and bone marrow were heavily infected. Interstitial pneumonia was observed. Pathological findings strongly resembled the full scale of lesions in human CMV infections. Anti-RCMV hyperimmune serum was effective against mortality from RCMV infection and viral spread to lungs and liver was prevented. This model is appropriate for studies on the pathogenesis and antiviral therapy of CMV infections in the immunocompromised host.

Animals↗
PubMed1990

[Oligodontia].

In every dental practice patients with oligodontia can be met. Oligodontia can occur solitary or as part of a syndrome. It is important for the dentist to be familiar with the various symptoms, including those of oligodontia as part of a syndrome.

Anodontia↗
PubMed1990

[Craniomandibular disorders. A retrospective study of patients referred to the department of Special Dental Care Utrecht].

The data of 230 randomly selected patients were collected, constituting a representative sample out of the population visiting the department of Craniomandibular Disorders in Utrecht in 1987. By means of a flowchart an overview has been given concerning the intake of these patients and their course in diagnosis and treatment. Within the group of CMD-patients, four subgroups have been composed on basis of clinical and radiological findings. Differences have been found between these groups, concerning e.g. mean age and the prevalence of headache. Treatment results expressed as the clinical dysfunction index (objective) and the judgement of the patient (subjective) were found to be correlated. Most patients expressed mild symptoms of dysfunction after treatment. From the self-report questionnaire it can be concluded that the majority of the patients reported a satisfying treatment result.

Consumer Behavior↗
PubMed1989

Structural and ultrastructural changes in skeletal muscle associated with long-distance training and running.

The histological and ultrastructural features of 21 males and 8 females were monitored during an 18- to 20-month training period, during which the training distance was gradually increased. The training period was divided into three periods of 6, 5, and 7 months, respectively. The first, second, and third periods were concluded with a 15-, 25-, 42-km road race, respectively. The competitive distance always exceeded the maximal distance covered in any previous training session. Percutaneous biopsies were taken from the vastus lateralis muscle 5 days before each contest as well as 0.5-6 h post-contest and 8-9 days post-contest. No shift in fiber type was observed during the training period from the 15-km contest until the 42-km contest nor were any changes in fiber diameter observed. Histological examination demonstrated a gradual increase in degenerative changes during the training period, which occurred in type I as well as in type II fibers. Ultrastructural examination revealed irregular Z-lines and hypercontraction immediately after exercise. No damage to the sarcolemma was detected. The number of degenerative changes after each contest was not higher than before each race. It is concluded that long-distance running is associated with transient minor pathological changes in skeletal muscle, which are related to the total distance covered per week rather than the intensity of the exercise.

Adaptation, Physiological↗
PubMed1989

The presence of cytomegalovirus nucleic acids in arterial walls of atherosclerotic and nonatherosclerotic patients.

The presence of cytomegalovirus (CMV) nucleic acids was demonstrated in abdominal aortas and femoral arteries of patients with and without atherosclerosis by dot blot and in situ DNA hybridization using a DNA probe derived from immediate early genomic regions. Viral antigens could not be detected by immunohistochemistry and infectious virus could not be recovered from the arterial wall by virus isolation techniques. The high percentage (55%) of vascular wall specimens containing CMV nucleic acids, in atherosclerotic as well as in control material and the location of CMV-containing cells in arteries without gross changes indicative of atherosclerosis suggest that the human arterial wall may be a site of latency for this virus.

Adult↗
PubMed1988

Heterogeneity of human tissue-type plasminogen activator.

Tissue-type plasminogen activator (t-PA) from human melanoma cells (Bowes) was purified by immunosorbent chromatography on affinospecific polyclonal antibodies and gel filtration in the presence of KSCN. The immunosorbent eluate contained three major components of greater than 200, 85 and 65 kDa, respectively. The 65 kDa t-PA component could be separated by gel filtration on Ultrogel AcA44 in the presence of KSCN to a pure preparation yielding a unique N-terminal amino acid sequence. Immunoblot analysis, using affinospecific antibodies against t-PA, was a specific and sensitive method to identify different types of t-PA (I-IV), as well as t-PA-inhibitor complexes and degradation products in unstimulated melanoma cell culture fluids. Furthermore, the t-PA preparations, produced by phorbol ester-treated melanoma cells, were free of type IV and thus differed physiochemically from the constitutively produced t-PA preparations. The composition of t-PA from mammalian cell cultures is thus more complex than hitherto described.

Animals↗