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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↗

Swallow thresholds in human mastication.

Brazil-nut particles were broken down and classified by sieves into four classes of particle size. Samples of these classes were suspended in plain yoghurt in varying concentrations and presented to nine humans for chewing. Both the number of chews made before swallowing and the time needed to swallow increased significantly with particle size and concentration but the chewing frequency (number of chews/time) decreased. The rate of change of the chewing frequency, averaged over the chewing sequence (chewing frequency/time), was calculated for each food input and termed the swallowing index. This index did not differ significantly for concentrations above 20%, but increased sharply at lower concentrations. These results were interpreted in terms of a model in which food is swallowed only when particles are both small enough and sufficiently lubricated. For our food mixture, the lubrication threshold was satisfied by a 20% concentration and the particle-size threshold was 1.4 mm. Chews made with concentrations lower than this and containing smaller particle sizes were few in number and slow, reflecting the need to detect particle size with the oral mucosa.

Adult↗

Effect of a denture adhesive on complete denture dislodgement during mastication.

A method of evaluating the denture stabilizing effects of a denture adhesive by means of counting denture dislodgements during the eating of a standardized portion of a test food is described. A reduction in the number of such dislodgements after application of a denture adhesive, as compared to eating the same food without adhesive applied to the denture, was used as a measure of adhesive effectiveness. Subject responses to a number of denture-performance satisfaction parameters were also obtained. With a test adhesive, significant reductions in dislodgement were found using steak, taffy-apple, a hard-roll sandwich, and celery as test foods among 16 subjects with dentures that fit well. Analysis of subjective evaluations indicated that the test adhesive was perceived as having effected: (1) improved chewing ability, (2) reduced denture wobble, (3) improved confidence, (4) increased comfort, and (5) reduced amount of food particles collecting under the denture, all to a significant degree (p < .01). It is suggested that additional data from controlled clinical studies are needed to allow proper assessment of the usefulness and possible abuse effects of denture adhesive products. This method, and the resulting data, are offered as a stimulus to the end.

Adhesives↗

Computer-based analysis of the single chewing cycle during mastication in repeated registrations.

A new computer-based analysis of the single chewing cycle was described as a complement to the Selspot system used for recording mandibular movements. Fifteen adults took part in a clinical investigation of masticatory movements recorded in two sessions with an interval of about 4 weeks. The analysis of the single cycle was performed in regard to chewing rhythm, mandibular displacement, and velocity; the results showed agreement with earlier published results. Most parameters showed agreement between the two registrations, but there was an indication of a weak adaptation to the test situation that should not be disregarded in repeated test situations.

Adult↗

Occlusal force pattern during mastication in dentitions with mandibular fixed partial dentures supported on osseointegrated implants.

The occlusal force pattern during chewing and biting was studied in eight edentulous patients whose dentitions had been restored with mandibular bilateral posterior two-unit cantilever fixed prostheses supported on osseointegrated titanium fixtures and occluding with complete maxillary dentures. The chewing pattern was comparable to that reported for subjects with complete healthy dentitions or with tooth-supported cross-arch fixed partial dentures. However, during chewing and swallowing the voluntary capacity of the jaw-closing muscles was used to a much greater extent. Contrary to reports for cantilevers in tooth-supported cross-arch unilateral posterior two-unit cantilever fixed partial dentures occluding with natural teeth, the posterior cantilever segments in the present fixture-supported cantilever prostheses occluding with complete dentures regularly exhibited the largest local forces. Despite this, material failures of this type of fixed prostheses are rare, as demonstrated in long-term follow-up studies.

Adult↗

Functional loading of the dentition during mastication.

A method is described whereby the electrical activity in the masseter muscles is used as an index of chewing force. By using the kinesiograph, it was possible to determine the interrelationship of the phases of the chewing cycle and to measure the duration of each phase. On the basis of a pilot study of 10 dentate subjects and two complete denture wearers, it appears that, although the magnitude of the applied load is reduced in denture wearers, this is to some extent compensated for by an increase in the time it is applied. The results also suggest that a greater force is applied to the supporting mucoperiosteum when inverted cusp teeth are used in the construction of the dentures.

Bite Force↗

The need of eccentric balance during mastication.

A study of the masticatory performance of 30 patients with balancing contacts in centric relation was compared with an equal number of patients with balancing contacts in both centric and eccentric relations. The study failed to show any significant difference between masticatory performance of the two groups.

Centric Relation↗