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Biomedical subjects

M R Heath

Publications and source records attributed to M R Heath.

At least 19 recordsLinked to original sources
PubMed1996

Natural bites, food consistency and feeding behaviour in man.

Complete feeding sequences (bite to terminal swallow) were recorded in 11 individuals (Class I occlusions) feeding on apple, banana and biscuit (hard cookie) to establish whether jaw movements characteristic of the stage I transport, chewing, stage II transport and swallowing processes found in non-human mammals could be identified in man. All participants took large natural bites (known weight) of each food, but seven were supplied standard 6-g pieces of apple. Jaw movements (three axes) were recorded using a locally calibrated Sirognathograph. Discrete stage I transport movements (bite moved from incisors to postcanines), were found in most records, but least frequently for banana. The number of chewing cycles before the first in-sequence swallow increased in the order: banana, ( = ) apple without peel, apple with peel, biscuit. Chewing cycles showed subtle changes in gape profile but significant variation in mediolateral movement cycle to cycle. Morphologically distinct stage II transport cycles could not be identified. Swallows occurred intermittently during chewing (79% of all sequences, n = 146) with cycle durations in excess of 1 s in contrast to the range for chewing (0.6-0.7 s). Almost all sequences ended with a period, clearance, of highly irregular jaw movements often including swallows. Clearance has not been described in other mammals. Food consistency affected feeding behaviour. The "chew/swallow' ratio (total number of chews/total number of swallows) increased with food hardness. The number of chewing cycles before the first in-sequence swallow also increased. Food type significantly affected sequence duration. The duration of clearance was also affected by bite weight and food hardness. It is concluded that initial food consistency determines the number of chewing cycles before the first swallow and overall sequence duration. The change in the pattern of jaw movement in both the vertical and mediolateral directions cycle to cycle suggests continuous sensory modulation of the motor output to the mandibular musculature.

Adult↗
PubMed1995

Automated optical scanning for rapid sizing of chewed food particles in masticatory tests.

Analysis of the reduction in sizes of particles after chewing has been a standard method for assessing masticatory efficiency for over 40 years, but the sizing of particles with sieves is very time consuming. A rapid simple method of measuring chewed almond particle sizes by an optical scanning method has been developed and is described. The aim of this study is to validate the accuracy, repeatability and speed of the application of an optical scanning system in measuring chewed particles. To determine the accuracy, paper circles were measured and compared with the travelling microscope measurements. The effect of orientation of the images were assessed by measuring three irregular shaped pieces of paper and three different sized pieces of chewed almonds. Measurements were taken singly at 18 degrees increments from 0-180 degrees orientations with each piece of paper. To assess the repeatability of measuring chewed particles, the particles from a single masticated almond washed with water and absolute alcohol were spread, separated and measured by the optical scanning system. The samples were then remeasured 10 times. The reproducibility of the method was investigated using three repeated masticatory tests for each subject in a group of 13 young dentate subjects. The speed of spreading the particles and of measurement was assessed. The absolute error range for a mean area of 31 mm2 was 2.85% to 7.32% with a mean of 3.86%. The relative accuracy of measurement was higher for larger particles but in no case was the standard deviation > 0.4 mm2.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1995

Oral health status of a population of community-dwelling older Canadians.

A sample of 170 responsive residents of seniors housing centres in Winnipeg, Canada, were studied, (>65 years, mean 82 years), with the objectives of relating their dental state to their perception of need and uptake of service. Only 6% rated their oral health as poor, 46% reported a dental visit within the previous year and 68% felt they needed dental treatment. A lack of perceived need (88%) was the primary reason why dental care was not sought more frequently. Hygiene practices revealed that only 7% brushed < 1 time/day, 60% never flossed, 14% cleaned their dentures <1 time/day, and 42% slept with their dentures. Dental histories showed that examination (94%), prosthodontic treatment (76%), and restorative services (65%) were the most commonly sought treatments. Perceived dental needs included prosthodontic treatment (39%), periodontal/prophylactic treatment (10%), restorative treatment (9%) and pain relief (9%). Study subjects had 2.8 decayed teeth, a DMFT of 25.1, and a Root Caries Index of 38%. CPITN scores of 3 or 4 in at least one sextant were found in 80% of subjects. Of the 41% edentulous, all wore complete dentures but 15% of complete upper dentures and 51% of complete lower dentures fitted poorly. Of the partial dentures, 20% fitted poorly. Soft tissue anomalies were seen in 67% of subjects and 47% had TMJ anomalies. Overall, 77% of edentulous subjects and all dentate subjects required some dental treatment even though 46% had seen a dentist within the preceding year. It is concluded that appropriate management of such people needs further attention.

Aged↗
PubMed1994

Assessment of chewing efficiency: a comparison of particle size distribution determined using optical scanning and sieving of almonds.

Particle sizes obtained with progressive chewing cycles were quantified by use of an optical scanning device and compared with the sieving method. The aim of this study was to validate the optical method by comparison with sieving using a natural test food, almond. Masticatory efficiency was assessed in six dentate subjects. The almonds were chewed for 1, 4, 8, 16 and 32 chewing strokes. Each experiment was replicated. The chewed material was sieved through a 1 mm aperture sieve on a Büchner funnel and dried after washing with water and 100% alcohol. The dried particles were weighed and scanned by an optical scanning device for number and size. The same samples were sieved and weighed with a conventional sieve method. The results of both methods were described by particle size distributions based on the volume of particles. The results derived from the optical scanning and sieving showed similarity. It can be concluded that the optical method is simple to use, faster than sieving and needs little skill in the use of equipment. The comparison of the results validates both methods.

Adult↗
PubMed1994

The effect of age on the recognition thresholds of three sweeteners: sucrose, saccharin and aspartame.

It is believed that people's sensitivity to taste declines with age but the evidence is inconclusive. This study was designed to test the hypothesis that taste recognition thresholds (TRTs) for sweetness are higher in older than in younger individuals, using groups of 16 younger subjects (18-30) and 16 older subjects (60-85). Three test substances were used: sucrose, aspartame and saccharin. A questionnaire recorded variables which might have affected TRTs, but data failed to show any trend that might have biased the principle variate-age. There was a significant alteration with age of recognition thresholds, at least for sucrose and saccharin. The differences between the groups for the three sweeteners were due to the fact that all the very sensitive subjects were young. None of the older subjects had particularly poor discrimination: all but one had TRTs within the range of younger subjects. Although there are age-related taste changes, they are much less dramatic than commonly occurs with other senses, such as sight and hearing. The findings of this study have implications for institutional catering and the dietary management of older people using non-sugar sweeteners.

Adolescent↗
PubMed1994

Recording mandibular movement: technical and clinical limitations of the Sirognathograph.

It is essential to know the limitations of any equipment used for research or clinical purposes. Clinical electronic equipment is commonly sold for "black box" use without specification of artifacts. This study tested the technical and clinical limitations of the Sirognathograph, which is a device used for recording mandibular movement. From a technical point of view, the Sirognathograph's slow sampling speed and sample artifacts have been shown to be the system's main limitations; however, it was possible to eliminate sampling artifacts by using a customized pulse generator and software for controlled data acquisition. Clinically, the Sirognathograph appears to have some inherent limitations in its accuracy. The effect of cranial movements during mastication can cause a baseline drift with consequent errors in the recording of mandibular position. This problem was controlled in this study by using a headband to stabilize the cranial movements during mastication. Also, the spatial relationships between the aerial and both the cranial base and the magnet were found to be critical for repeatability of the recordings.

Adolescent↗
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↗