Doctor of Philosophy

dissertationCarpal tunnel syndrome (CTS) is the number one cause of disability at work in the United States. Loss of time at work and worker's compensation expenditure caused by CTS is more than that caused by any other condition. However, workplace surveillance is likely to help in detecting CTS at a stage that is treatable at a significantly lower cost. Vibrotactile threshold (VT) testing can be used for this purpose. The VT is the smallest displacement applied (as a sinusoid) to a finger innervated by the median nerve that can be detected by the patient. Vibrotactile threshold evaluation can be a versatile tool for applications involving haptics interfaces, for evaluating peripheral neuropathies, and for studying the effects of chemotherapy induced neuropathies. This dissertation presents the prototype design of a vibrotactile threshold evaluator for the workplace (VTEW), which is portable, and configurable in terms of the probe diameter (1-6 mm), surround diameter (8-10 mm), applied frequency (1-250 Hz), angle of probe (0-1200), and displacement of probe (1-1500 ?m) and is operated with a customizable LabView interface. The VTEW also incorporates a special mount for the probe stimulus to test the subjects in at least two distinctive postures of the hand. Subjects were tested using an existing validated device, Vibrotactile Threshold Tester (VTT) and VTEW. Subjects were tested at 50 Hz with VTT and VTEW for validation. The effect of flexion on VT was observed by testing the subjects on VTEW at 50 Hz with their dominant hand in neutral posture and again with their dominant hand in provocative flexion. Use of low frequency for testing in VT studies is uncommon due to hardware constraints. However, low frequency studies could be potentially useful for investigating the effects of chemotherapy on the perception of pain. Thus, subjects were also tested at 4 Hz using VTEW to obtain preliminary data. Finally, an age regression model was developed to correct for the changes occurring in VT with age

Oral Somatosensory Awareness

Oral somatosensory awareness refers to the somatic sensations arising within the mouth, and to the information these sensations provide about the state and structure of the mouth itself, and objects in the mouth. Because the oral tissues have a strong somatosensory innervation, they are the locus of some of our most intense and vivid bodily experiences. The salient pain of toothache, or the habit of running one's tongue over one's teeth when someone mentions "dentist", provide two very different indications of the power of oral somatosensory awareness in human experience and behaviour. This paper aims to review the origins and structure of oral somatosensory awareness, focussing on quantitative, mechanistic studies in humans. We first extend a model of levels of bodily awareness to the specific case of the mouth. We then briefly summarise the sensory innervation of oral tissues, and their projections in the brain. We next describe how these peripheral inputs give rise to perceptions of objects in the mouth, such as foods, liquids and oral devices, and also of the mouth tissues themselves. Finally, we consider the concept of a conscious mouth image, and the somatosensory basis of "mouth feel". The theoretical framework outlined in this paper is intended to facilitate scientific studies of this important site of human experience

Investigating interocclusal perception in tactile teeth sensibility using symmetric and asymmetric analysis

The purpose of this clinical trial was to determine the active tactile sensibility of natural teeth and to obtain a statistical analysis method fitting a psychometric function through the observed data points. On 68 complete dentulous test persons (34 males, 34 females, mean age 45.9 ± 16.1years), one pair of healthy natural teeth each was tested: n = 24 anterior teeth and n = 44 posterior teeth. The computer-assisted, randomized measurement was done by having the subjects bite on thin copper foils of different thickness (5-200µm) inserted between the teeth. The threshold of active tactile sensibility was defined by the 50% value of correct answers. Additionally, the gradient of the sensibility curve and the support area (90-10% value) as a description of the shape of the sensibility curve were calculated. For modeling the sensibility curve, symmetric and asymmetric functions were used. The mean sensibility threshold was 14.2 ± 12.1µm. The older the subject, the higher the tactile threshold (r = 0.42, p = 0.0006). The support area was 41.8 ± 43.3µm. The higher the 50% threshold, the smaller the gradient of the curve and the larger the support area. The curves showing the active tactile sensibility of natural teeth demonstrate a tendency towards asymmetry, so that the active tactile sensibility of natural teeth can mathematically best be described by using the asymmetric Weibull functio