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Biomedical subjects

F A Young

Publications and source records attributed to F A Young.

8 recordsLinked to original sources
PubMed1979

Porous titanium endosseous dental implants in Rhesus monkeys: microradiography and histological evaluation.

Artificial tooth roots with porous surface coatings were fabricated by sintering spherical powder of titanium alloy to solid cylindrical cores. The tooth roots were implanted subgingivally in healed mandibular premolar extraction sites of fifteen Rhesus monkeys. Supracrestal abutments were screwed into pretapped holes in the superior aspect of the primary subgingival stage four to eight weeks after implantation of the root. Clinical evaluations were performed monthly. Ten animals were sacrificed for histological evaluation of the functioning free standing implants. Of twenty-nine implants placed, three were lost and four were rated failures on the basis of histological evaluation. Postmortem evaluations revealed bone growth into the porous surface coating of the primary stage of all the implants. The most characteristic features which could be used to describe differences in the implant histology were the buccal and lingual crestal bone heights measured in relation to the root porosity. Twelve of sixteen implants had crestal bone heights within one millimeter of the superior aspect of the root. Four other implants displayed excessive bone recession, revealing as much as one half of the root porosity supracrestally. The four implant failures could be related to unfavorable features of recipient bone sites. The results demonstrate that the bone growth into the porous surface coatings of artificial tooth roots is an efficacious method of dental implant fixation.

Alloys↗
PubMed1979

Porous titanium tooth roots: clinical evaluation.

1. An inert porous vehicle can be successfully used to attach endosseous dental implants to surrounding alveolar bone. 2. Implant size and the width of keratinized gingiva surrounding the implant are critical to the success of the implant. 3. Radiography and pocket depth are useful indicators of the status of porous endosseous roots, while mobility is not.

Alveolar Process↗
PubMed1977

An electronic apparatus to measure the retinal-neural fading phenomena.

Fading and regeneration of visual stimuli is a phenomenon which occurs under the condition of redundant visual stimulation in the human eye. By totally encompassing a subject's visual field with large sheets of colored cardboard, which provided an undifferentiated ground, it was found that the color spontaneously disappeared and reappeared. This evidence suggested that the cycle is a fundamental aspect of the visual process. The Retinal-Neural Fading Phenomena Device was developed using light-emitting diodes (LED) as the stimulus source. This allowed the quantitative measurement of the rate of fade and degree of satiation the eye undergoes under a redundant presentation equivalent to stabilized images. The rate and degree of satiation to redundant stimulation appears to correlate highly with a subject's reading efficiency. The data suggested that rapid and deep satiation was the favored outcome if one is to be free from reading or perceptual disorders. This leads to the speculation that rapid fade of afterimages of previously read symbols is required to prepare the visual system for new material. Conversely, the inability to suppress afterimages may be a physiological factor in the "dyslexic syndrome."

Afterimage↗
PubMed1977

The nature and control of myopia.

There is a growing body of evidence to support the belief that most myopia develops as a result of prolonged exposure to nearpoint activities. This paper summarizes the most important studies that have been done and postulates a mechanism by which prolonged accommodation can result in myopia. Possible means of arresting or preventing the development of myopia are discussed.

Accommodation, Ocular↗
PubMed1976

Values, personality, physical characteristics, and refractive error.

A questionnaire containing: (a) a questionnaire of physical characteristics associated with psychosomatic symptoms, (b) questions to determine the presence of myopia or hypermetropia but not the amount of error, (c) a shortened version of the Gough Adjective Check List, and (d) the Heist and Yonge Omnibus Personality Inventory were administered to 782 introductory psychology students attending Washington State University. This group consisted of 297 self-identified myopes (117 males, 180 females), 439 emmetropes (207 males, 232 females), and 46 hypermetropes (15 males, 31 females). Results indicated that myopes and nonmyopes differed from one another with respect to their value systems, personality, and physical characteristics as assessed by the components of the questionnaire. Differences in these characteristics were consistently found by all assessment techniques to exist most often between myopes and hypermetropes and between emmetropes and hypermetropes rather than between myopes and emmetropes. In general myopes exhibited a personality pattern of introversion, whereas hypermetropes maintained a pattern described as extroverted.

Adult↗
PubMed1975

The psychological differentiation of male myopes and nonmyopes.

A comparison of 140 male myopes and 118 male nonmyopes of the entering class of Virginia Military Institute cadets in 1968 demonstrated that there are a number of Strong Vocational Interest Inventory test items which will clearly differentiate myopes from nonmyopes so that it is possible to identify 76% of the individuals falling into either class on the basis of a stepwise discriminant analysis based almost entirely on the Strong Vocational Interest Blank. The items which discriminate in favor of the myopes are essentially those which require academic achievement and individual creative performance, whereas the items which are in favor of the nonmyopes are those which require business and selling skills as well as outdoor types of activities. Further, the myopes are significantly more likely to achieve officer status and win more academic awards than the nonmyopes.

Factor Analysis, Statistical↗
PubMed1975

Bifocal control of myopia.

Forty-three native American bifocal wearers grouped by yearly age levels from 9 to 15 with a mixed group of 6 to 8 year olds are matched on beginning age, sex, beginning refractive error and ending age with 83 Native American control subjects. Similarly 226 Caucasian bifocal wearers are matched on the same criteria against 192 control subjects. Although the comparisons are made on each age group, the average annual rate of progression for the bifocal Native American subjects is -0.12 and -0.10 diopters in the right and left eyes respectively against a comparable rate of progression of -0.38 and -0.36 diopters for the control subjects. These differences are significant but not as significant as those found on the Causcasian subjects of -0.02 and -0.03 diopters right and left eyes against -0.53 and -0.52 diopters for the controls.

Adolescent↗