Biomedical subjects

J F Prinz

Publications and source records attributed to J F Prinz.

7 recordsLinked to original sources

PubMed1997

Mechanical properties of foods responsible for resisting food breakdown in the human mouth.

The fragmentation of foods (breakage function) was measured in five humans on "bagged' single particles of 28 foods from three food groups. The change in the square root of the specific surface of the particles (the specific surface being the area of particle silhouettes, measured by image analysis, divided by original particle volume) produced by one bite, averaged for all participants, was inversely linearly related to the square root of the toughness of the foods divided by the square root of their Young's moduli(r = -0.86; p < 0.00001). This relation is predicted by an analysis based on food fragmentation within a limited jaw displacement. Thus, resistance to jaw movement appears to provide sensory information on the deformation fracture and fragmentation of foods. It is believed that this is the first time that a relation between the breakage of food particles by the teeth and their material properties has been found, and the finding has considerable implications for human masticatory studies, for the analysis of dentition and diet in mammals and for texture studies in food science.

Adult↗

PubMed1997

The Cybermouse: a simple method of describing the trajectory of the human mandible in three dimensions.

A simple method of recording the three-dimensional movements of the mandible together with up to 10 channels of other physiological data is described. The system is based on a commercially available device, the Cybermouse (IPC, Freemont, CA, U.S.A.), consisting of a lightweight ultrasonic emitter which can be attached to the chin by means of an elasticated band, and a base unit which contains three ultrasonic detectors. A microprocessor in the base unit calculates the position of the emitter by analysing the differences in the times of arrival of signals from the emitter. Physiological data is acquired using the PICO-ADC11 (Pico Technology, Cambridge, U.K.) a 10-channel analogue-to-digital converter. As an example, an application where temporomandibular joint sounds and mandibular movement data were collected simultaneously is described. The Cybermouse is of sufficient accuracy for use in most situations, and its ease of use and relatively low cost outweights its few disadvantages when compared to more complex systems.

Humans↗

PubMed1997

Vibration transmission across the temporomandibular joint.

A non-invasive method of assessing the status of the temporomandibular joint is presented. The method involves placing a computer-controlled vibrator against a lower incisor, and microphones over the temporal bones. The amplitude of the signal transmitted is shown to be a function of the input frequency, the position of the mandible and the loading on the joint.

Acoustics↗

PubMed1996

Characterization of sounds emanating from the human temporomandibular joints.

Sounds from the temporomandibular joint were recorded on audiotape from 238 individuals by placing microphones in both ears. The recordings were later digitized at a sample rate of 1.7 kHz with 10-bit resolution and stored on computer disk. At least two open-close cycles were assessed from each individual; 2707 different individual sounds were analysed in the time and frequency domains. The sounds were classified as: (a) single, short duration (clicks), (b) multiple, short-duration (creaks) and (c) long duration (crepitus). The sounds were further subclassified into either high or low amplitude by (i) the attack, which produced hard and soft categories and (ii) comparing the amplitude between sides-bilateral sounds were those with amplitudes differing by < 40 mV; the rest were unilateral. To establish the robustness of the classification 42 acoustic events were selected to be classified visually by three observers on two separate occasions. Intraobserver agreement was 82% (kappa = 0.75) while interobserver agreement was 60% (kappa = 0.71). Statistically significant differences were noted between all classifications of sound. These were most marked in the time domain. A simple, automated classification scheme was devised that was capable of categorizing the sounds with 82% agreement (kappa = 0.71) compared to a human observer.

Adolescent↗

PubMed1995

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↗

PubMed1994

A modified stethoscope to assist in the identification of tooth coloured restorations.

Forensic odontologists are often called upon to assist in the identification of bodies. Since identification of the body relies on comparison of the post-mortem chart with the ante-mortem record it is important that all restorations present in the deceased's teeth are identified and correctly charted. If a restoration is present in an ante-mortem record then its absence in the post-mortem chart means that the two records cannot belong to the same person. However, tooth-coloured restorations can be difficult to identify, especially in the less than ideal conditions under which the odontologist may have to work. This study was designed to evaluate a simple technique for identifying tooth-coloured restorations, exploiting the difference between the surface roughness of restorative materials and that of the surrounding tooth substance. A conventional dental probe was substituted for the bell of a stethoscope. Differences in the surface texture of the tooth are reflected in changes in the sound heard by the examiner. The modified stethoscope is a useful and easily fabricated device, which may reduce the likelihood of small tooth-coloured restorations going unnoticed in post-mortem examinations. The ability to detect fissure sealants using the device may also prove useful in epidemiological studies.

Adult↗

PubMed1993

A forensic dental identification system with error tolerant algorithms and a review of the prevalence of errors occurring in dental records.

After a major disaster, identification of the victims may have to be performed by comparison of the antemortem and post-mortem dental records. Ante-mortem records often contain errors and these must be identified, and compensated for in some way. A computer system for the comparison of large numbers of ante-mortem and post-mortem dental records has been developed, using algorithms which are able to compensate for errors in the records. Data has been collected on the prevalence of errors in dental charts. These were found in 45% of a sample of 50 records. Since matches found by the system may be due to coincidence, a score is computed for each record based on its 'uniqueness'. This allows a confidence limit to be placed on any matches found between the antemortem and post-mortem records.

Algorithms↗