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Biomedical subjects

P G Howell

Publications and source records attributed to P G Howell.

At least 37 records · Page 2Linked to original sources
PubMed1987

The variation in the size and shape of the human speech pattern with incisor-tooth relation.

A mandibular kinesiograph was used to monitor the movement of the lower incisors of young dentate adults reading a standard text. An interface to a microcomputer which recorded and analysed these movements. As the tracings accumulated on the computer monitor, a characteristic pattern was produced. The dimensions of this speech pattern, or envelope of movement, were measured and correlated with the subject's sex and incisor classification. Four distinct patterns were found and these correlated well with incisor classification. Small differences were noted in the dimensions of the speech envelope between men and women, but these were not significant.

Adolescent↗
PubMed1986

Incisal relationships during speech.

The dimensions of movement of the mandible during the reading of a standard passage of text have been measured and enable a speech envelope to be described. The relationship between closest speaking space and the vertical overlap of the incisor teeth shows that there is a trend in this direction, but it is not as definitive a correlation as has been previously assumed. The relationship between the anterior speaking space and the horizontal overlap of the incisor teeth shows a similar trend but with a much reduced correlation. There was often a small space of approximately 0.2 mm between the mandibular incisor teeth and the palatal aspects of the maxillary incisor teeth that, although a common finding in this study, was by no means a constant feature for all subjects.

Adolescent↗
PubMed1986

Simple SEM stereophotogrammetric method for three-dimensional evaluation of features on flat substrates.

A semi-automated method was developed for the measurement of the volume of a calcified tissue substrate which can be resorbed by single, isolated resorptive cells (osteoclasts). The procedure would, however, be applicable to the study of any pit in, or projection from, a flat surfaced specimen. Stereo-pair images are recorded with an SEM. 3-D co-ordinates of relevant surface features are derived using a stereo-comparator which outputs data directly to a microcomputer. Algorithms adopted have been chosen to give the best compromise between accuracy and speed of data acquisition.

Animals↗
PubMedDate not supplied

Surface roughness of preparations for backscattered electron-scanning electron microscopy: the image differences and their Monte Carlo simulation.

Patterns and levels of mineralisation in the biological hard tissues have been studied using the backscattered electron (BSE) mode in the scanning electron microscope (SEM). To prevent gross topographic detail overwhelming changes in signal from composition, samples are embedded in polymethylmethacrylate (PMMA) and a flat block surface produced by polishing or micromilling. This study was undertaken to establish the degree of residual topography achieved in these finishing processes. A sample of human rib was embedded in PMMA and prepared, as for examination in the SEM, by polishing on graded abrasives and pre- and, finally, ultramilling. After each preparation step, the block face was imaged using a confocal reflection microscope surface mapping facility. The recorded topographies were used in a Monte Carlo simulation to model the surface interface and thus, for each of the sample preparation techniques, to calculate predicted variations in BSE signal. The latter were compared with experimental data derived under standard operating conditions in the SEM. Micromilling produced block faces with typical peak-trough relief of 80 nm, while hand polishing left occasional scratches 1.5 microns deep with a general undulation of 150-250 nm. Monte Carlo simulations of a rough surface of bone using these data predicted that additional contrast levels of 5% could be expected from micromilled surfaces and > 10% for hand polished samples of bone. Thus, micromilling is the best preparation method for bone, since this tissue develops a collagen orientation-related relief on polishing, which may be largely responsible for the (incorrect) supposition that lamellation in bone is related to changes in net degree of mineralisation.

Humans↗