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Biomedical subjects

M R Heath

Publications and source records attributed to M R Heath.

At least 37 records · Page 2Linked to original sources
PubMed1993

Digastric muscle response as a function of knowledge of the task to be performed.

Whether the motor programme executed by the digastric muscles during a forceful bite is modified according to a subject's expectation that the resistance between the teeth will change was investigated. There were two experimental conditions: (1) tracking a ramp (drawn on an oscilloscope screen) by biting (isometrically) on a force transducer and holding it at 120 N, and (2) tracking the same ramp with a sudden unloading at 100 N. There were two groups of experiments: (1) control experiments in which subjects underwent a sudden and unexpected unloading of the jaw, and (2) experiments in which subjects were previously informed whether or not there was to be an unloading. In all experiments the subjects co-contracted their digastric muscles during the bite as compared to the state at rest. The subjects' responses fell into the three different types: (i) those who varied the level of tonic digastric activity only as a function of the experimental condition, (ii) those who co-contracted the digastric muscles at the same time as the masseter muscles, and (iii) those who changed the contraction pattern of the digastric muscles as a function of the experimental condition. If modulation of the digastric muscles occurred this is a 'feedforward' strategy mainly based on immediate past performance.

Bite Force↗
PubMed1993

A comparison between sieving and optical scanning for the determination of particle size distributions obtained by mastication in man.

Mixtures of particles of different sizes, as obtained after chewing, were analysed. Coarse, medium and fine mixtures of particles of an artificial (Optosil) test food were used. Mixtures of Optosil particles of known form and size (half-cubes) were used to validate the analytical methods. The results of both methods were described by particle size distributions based on the volume of the particles. Complete agreement between methods was found for the mixtures of half-cubes. In order to determine the median particle size by volume from the results of optical scanning an assumption on the form of the chewed particles had to be made. Using the assumption that, on average, the particles resemble spheres a slight overestimate of the median particle size was obtained for scanning as compared to sieving. It can be concluded that, although different aspects of the fragmented particles are measured, sieving and optical scanning are both adequate methods for quantifying mixtures of chewed food particles and yield similar results for the degree of particle size reduction.

Calibration↗
PubMed1993

A comparison between data analysis methods concerning particle size distributions obtained by mastication in man.

Three mixtures of chewed food particles (coarse, medium and fine) were quantified by measuring the particle sizes with an optical scanning device. The particle sizes were described by three different particle-size distributions: a cumulative volume, a volume and a number distribution. The median particle size was determined from each of the distribution functions. Suitability for characterizing a mixture of chewed food particles was tested, showing that the median particle size as obtained from a cumulative volume (or weight) distribution should be preferred. It was shown to be the most sensitive measure for characterizing mixtures of chewed food.

Calibration↗
PubMed1993

Contribution of periodontal receptors and food qualities to masseter muscle inhibition in man.

Previous studies of human muscle inhibition during chewing have shown that many factors contribute to the incidence and intensity of this reflex but few studies have been in a physiological context. During the first crushing cycle of brittle foods ipsilateral masseter muscle EMG, mandibular movement and vibration were recorded simultaneously in four healthy dentate subjects. Experiments were repeated before and during anaesthesia of the cheek teeth on the chewing side. The results suggest that vibration seems to be the most important factor in muscle inhibition during food crushing; conversely periodontal sensation, mandibular closing movement and the preload by the muscle at the onset of food fracture play a minor role.

Adult↗
PubMed1993

Anterior digastric muscle responses to sudden unloading of the mandibular elevator muscles in younger and older adults.

The digastric motor responses in the unloading reflex were investigated in a sample of 10 younger and eight older dentate subjects. The occurrence of the pre-collapse digastric activity (PDA) and the reflex events (burst of activity) following the mandibular unloading (DB) were studied separately. PDA was nearly consistent in half of the subjects of both groups. DB was clearly identified in 60% of the younger subjects, but in 54.2% of the older subjects. The mean latency of DB found in the younger subjects was 32.4 +/- 9.5 ms but 34.5 +/- 8.8 ms in the older subjects. For the latencies found we can infer that they are related to polysynaptic pathways. Also a slight tendency for decreased frequency of occurrence and increased latencies of DB is observed in the older age group.

Adult↗
PubMed1993

Assessment of the clinical status of primary root carious lesions using an enzymic assay.

The microflora of root carious lesions (n = 151) and sound root surfaces (n = 30) in 22 institutionalized, older patients was investigated using a standardized method of sampling. Material was removed using a sterile excavator and the numbers of bacteria in each sample were determined using conventional culturing techniques and by rapid (2 h) fluorogenic enzyme assay. Correlation between bacterial counts and enzyme assay result was 0.873 (p < 0.001). The numbers of bacteria and fluorogenic enzyme assay values were significantly (p < 0.001) greater from soft lesions than from leathery lesions while hard lesions and sound root surfaces had significantly (p < 0.001) lower values than the other lesion types and were not different from each other. A similar trend was apparent when these values were correlated with treatment needs. The fluorogenic enzyme assay may provide a rapid, objective measure of root caries severity which might be used in the monitoring and comparison of treatment protocols.

Aged↗
PubMed1993

A microbiological study of primary root-caries lesions with different treatment needs.

Samples of altered or carious dentin for microbiological culture were obtained from 301 primary root-caries lesions in 59 patients by means of a standardized sampling procedure. This involved the cleansing of each root surface of extraneous supragingival plaque by means of a hand-held toothbrush and distilled water and the collection of the sample with a sterile dental excavator passed through the entire vertical dimension of each lesion. The total number of colony-forming units (cfu) in each sample and the numbers of mutans streptococci (primarily Streptococcus mutans), lactobacilli, yeasts, and Gram-positive pleomorphic rods (GPPR) were determined. Individual bacterial counts were expressed as log10 (cfu per sample), as a percentage of the total number of bacteria per sample, and as a frequency of isolation from lesions with different clinical diagnostic criteria. Clinical measurements of each lesion were made for color, texture, position relative to the gingival margin, and treatment need. Lesions classified as soft yielded significantly more bacteria, mutans streptococci, lactobacilli, and GPPR than leathery lesions, which yielded more bacteria than hard lesions. Lesions were classified into 5 treatment categories: soft and restore, leathery and restore, leathery and debride of caries; leathery and treat therapeutically; and hard no treatment. The total numbers of bacteria, mutans streptococci, lactobacilli, GPPR, and yeasts decreased significantly with decreasing treatment need. The frequency of isolation of mutans streptococci, lactobacilli, and yeasts was significantly greater from lesions requiring restoration and from lesions situated within 1 mm of the gingival margin. We suggest that the majority of root caries is initiated adjacent to the gingival margin.

Actinomyces↗
PubMed1992

A multicenter study of overdentures supported by Brånemark implants.

Nine clinical centers participated in a prospective study of overdentures supported by Brånemark implants in the maxilla or mandible. The study initially comprised 133 patients provided with 117 implants placed in the maxilla and 393 implants placed in the mandible. The preliminary results indicate a success rate in the mandible comparable with the reports on fixed prostheses. Conversely, overdenture treatment in the maxilla seems to be less favorable than previous reports of fixed restorations. The differences between the fixed and the present overdentures in the maxilla were mainly based on differences in patient selection and bone quality. A total of 32 implants was mobile and removed and another 29 implants were lost to follow-up because of patient dropout up to the first annual checkup after denture placement. A higher implant failure rate occurred in the maxilla. Mucosal reactions were also more unfavorable around implants placed in the maxilla.

Adult↗
PubMed1991

Swallow thresholds using dentures made on different types of articulator.

The purpose of this study was to determine whether edentate subjects achieved different performance when using dentures constructed on different articulators. A cross-over experimental design was employed to evaluate these swallow thresholds using complete dentures constructed on the hinge and free plane articulators. Seven subjects completed the study. Swallow threshold tests were performed 3 months after the insertion of dentures. The overall particle size distribution achieved with the dentures constructed on free plane articulators was significantly better at the end of the 3-month period (P less than 0.01 to P less than 0.0001), but significantly more strokes were used to achieve this success rate (P less than 0.04). A questionnaire revealed that the subjects had a preference for the denture constructed on the free plane articulator. It is concluded that patients performed better with dentures constructed on the free plane articulator.

Adult↗
PubMed1991

Salivary levels of mutans streptococci, lactobacilli, yeasts, and root caries prevalence in non-institutionalized elderly dental patients.

Root caries prevalence was recorded for a consecutive sample of dental patients (n = 146), aged over 55 yr and with at least 12 natural teeth. The mean root DFS score of the males (n = 49) was 6.34 +/- 4.55 and for the females (n = 97) 3.76 +/- 3.31 (P less than 0.001). The salivary levels of mutans streptococci, lactobacilli, and yeasts were determined in addition to salivary flow rate and buffering capacity. Subjects with greater than 1 root DFS had significantly higher salivary levels of mutans streptococci, lactobacilli, and yeasts. They also had fewer teeth and more exposed root surfaces. In step-wise multivariate analyses the factors significantly related to the root DFS score were the number of exposed root surfaces, number of teeth, sex and salivary yeast levels (R2 = 0.41). In the multivariate analyses salivary levels of mutans streptococci were not significantly related to any clinical measurement of root caries experience due to the greater strength of association between the root DFS score and salivary levels of yeasts. Subjects prescribed medicines with a reported xerostomic effect had significantly fewer active root lesions than those not prescribed such medicines and salivary levels of all microorganisms studied were significantly elevated in subjects prescribed medications containing sucrose.

Aged↗
PubMed1991

Case report: the management of severe tooth wear with palatal resin bonded cast restorations combined with removable partial dentures.

The restoration of advanced tooth wear can present considerable problems. Conventional fixed prosthodontic treatment can be destructive to the already compromised dental tissues, time consuming and therefore costly. With recent advances in resin bonded technology, this may now be considered an option for definitive treatment in such cases. This case illustrates the use of palatal resin retained cast metal veneers. These veneers restored the worn palatal surfaces of the anterior maxillary teeth, protected them from further wear and controlled thermal sensitivity. They also provided support for a conventional maxillary partial denture.

Aged↗
PubMed1990

Root caries in older people attending a general dental practice in East Sussex.

With increasing numbers of older people retaining their natural dentitions, dentists are becoming increasingly aware of the problem of dental caries occurring on exposed root surfaces--root caries. This study reports the prevalence of root caries in a selected older population, living in the community and attending a general dental practice in Bexhill, East Sussex. A total of 146 non-institutionalised people, aged at least 55 years with at least 12 teeth, were examined. Most of the subjects (88.4%) had evidence of root caries, males and denture wearers having more lesions than females and non-denture wearers, respectively. Active coronal caries was present in only 11.6% of the subjects, whereas active (soft or leathery) root caries lesions were present in 31.5% of the subjects. The teeth and surfaces most commonly affected by root caries were found to be similar to those seen in previous epidemiological surveys. The majority of active root caries lesions were within 1 mm of the gingival margin, while inactive lesions tended to be greater than or equal to 1 mm from the gingival margin. Colour of root caries lesions was not diagnostic of caries activity. A more detailed method of recording root caries lesions is also described.

Aged↗
PubMed1990

Associations between salivary levels of mutans streptococci, lactobacilli, yeasts and black-pigmented Bacteroides spp. and dental variables in elderly dental patients.

Multivariate step-wise regression analyses demonstrated that in a population of 146 elderly dental patients (mean age 69.8 yr) the salivary level of mutans streptococci was unrelated to the root DFS score, unlike the levels of lactobacilli and yeasts. Mutans streptococci were related to the wearing of partial dentures and the number of snacks eaten per day, while salivary lactobacillus levels were also related to the number of snacks eaten per day and to denture wearing, and negatively related to saliva buffering. Salivary yeast levels were also related to the wearing of partial dentures and the number of snacks eaten per day, and negatively related to salivary neuraminidase activity. The R2 values ranged from 0.21 to 0.28. Salivary level of black-pigmented Bacteroides spp. were related to maximum CPITN score, mean bleeding index and salivary trypsin-like activity (R2 was 0.08).

Aged↗
PubMed1982

The effect of maximum biting force and bone loss upon masticatory function and dietary selection of the elderly.

Simple methods are described for measuring masticatory effectiveness--the percentage of sugar chewed out of chewing gum in 20 strokes--and the height of residual mandibular bone using callipers. Both are objective methods, they are acceptable to the elderly, appropriate for denture wearers and practicable for use in domiciliary surveys. Using these and other methods, the masticatory effectiveness of housebound pensioners is shown to relate to maximum biting force, denture quality, remaining mandibular bone and dietary selection. However, opinions on the difficulty of mastication are completely unrelated to any of these measures. The level of compensation for inadequate mastication is indicated by the percentage of difficult foods eaten by geriatric hospital inpatients: there was complete overlap of percentages in those endentulous patients using dentures and those without dentures. Presumably many of these patients had adapted to swallowing very poorly chewed food. The contrasts shown between hospital inpatients and old people still at home indicate the progressive consequences of physical and neurological deterioration.

Adult↗