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Biomedical subjects

J T White

Publications and source records attributed to J T White.

33 records · Page 2Linked to original sources
PubMed1981

Modification of stresses surrounding abutment teeth for fixed partial dentures induced by various levels of periodontal support: a photoelastic study.

A photoelastic replica system was used to study stresses produced within the periodontium of abutment teeth for a fixed partial denture. Three replicas, each representing a different level of periodontal support, were constructed. Abutment teeth were subjected to occlusal forces and examined in a polariscope before and after prosthesis construction. Stress distributions and concentrations produced in the periodontium of abutment teeth by an occlusal force were favorably altered by the placement of a fixed partial denture. Stress concentrations produced in the periodontium of abutment teeth were notably altered by a moderate (20%) loss of support. Further (40%) loss of periodontium did not result in appreciably additional change. The stress patterns produced in the periodontium of both replicas which simulated loss of periodontium were also favorably altered by the placement of a fixed partial denture.

Dental Abutments↗
PubMed1981

Coronary circulation in hearts from hibernating, normothermic, and cold-acclimated hamsters.

We have investigated the influence of temperature, acute global ischemia, adenosine administration, and alterations in perfusion pressure on the coronary circulation of isolated, perfused spontaneously beating hearts from hibernating, normothermic, and cold-acclimated (nonhibernating) hamsters. No differences in heart rates were observed among groups at either 9 or 38 degrees C. Hearts from hibernating hamsters showed some differences in autoregulatory capacity at both the low and normal temperatures. All hearts exhibited similar responses to 30 s of global ischemia at both temperatures, with a marked reduction in the response at 9 degrees C. Similarly, the magnitude of the vasculature response to adenosine (250 micrograms) at 38 and 9 degrees C was equal in both normothermic and hibernating hearts perfused at 38 degrees C. Responses were abolished in all groups at 9 degrees C. We conclude that the altered ability of hibernating hearts to autoregulate is possibly due to intrinsic differences initiated by hibernation, while the responses to adenosine, and global ischemia are largely temperature-dependent effects.

Acclimatization↗
PubMed1980

A photoelastic analysis of the stress distribution in bone supporting fixed partial dentures of rigid and nonrigid design.

Within the limitations of the experiment, the following conclusions can be made from this investigation: 1. Under conditions of vertical loading, the rigid fixed partial denture design does not permit independent response by either abutment. The nonrigid fixed partial denture design allows the abutments some independence in response to vertical loading 2. The stress distributions and concentrations produced in the supporting bone are favorably altered by the placement of a fixed partial denture of rigid or nonrigid design. 3. The distribution of stresses in the supporting bone varies with the number and location of the loading sites. 4. Under conditions of vertical loading, the Ney and Stern nonrigid fixed partial denture designs exhibit no significant differences in stress distribution or concentration.

Alveolar Process↗
PubMed1979

Multisectional mold for fabrication of prosthetic ears.

The use of a multisectional stone mold is advocated for the fabrication of prosthetic ears. Less force is required in the deflasking procedure with this technique, reducing the risk of fracturing the mold or tearing the prosthesis. This technique requires more time and care in the flasking procedure. Convergence of the sections is of particular importance. The potential for multiple section lines may result in a need for more surface finishing of the prosthesis.

Ear, External↗
PubMed1979

Myospherulosis.

A young Thai immigrant presented with a mass in the left hip, pain, and difficulty in ambulation. At operation, the mass was found to be a group of cysts containing bizarre, fungus-like structures like those first described in Africa and recently in St. Louis. The cause of this condition may be iatrogenic, resulting from a peculiar reaction to intramuscular injection.

Adult↗
PubMed1978

Visualization of stress and strain related to removable partial denture abutments.

The following conclusions are based on the conditions set forth in this investigation and apply to forces acting through a vertical direction of application only: 1. The unilateral removable partial denture produced no more stress than the bilateral removable partial denture. 2. The fully active Dalbo removable partial denture resulted in the greatest stressbreaking action. 3. The rigid Dalbo removable partial denture resulted in the least ridge displacement. 4. The rigid Dalbo removable partial denture resulted in the greatest stress concentrations in the distal abutment. 5. None of the attachments tested resulted in a distribution of the stresses along the edentulous ridge. 6. The use of two abutments (double abutments) resulted in greater stress concentrations in the distal abutment than the use of single abutments. 7. Forces in the single abutment were resisted along the long axis of the root. 8. Forces in the double abutments were resisted along the long axis of the distal abutment.

Alveolar Process↗
PubMed1978

Technique for cranioplasty prosthesis fabrication.

A technique has been described for fabrication of a cranioplasty prosthesis. The primary advantage of this technique is the duplication of the altered working cast. The technique also permits excellent reproduction of cranial contours and a positive seat of the prosthesis on the outer table of the skull. The disadvantage is the time involved in the duplicating procedure.

Acrylic Resins↗
PubMed1978

Presence of satellite cells in a cardiac rhabdomyoma.

Cardiac rhabdomyoma is the most common tumour of the heart in infancy and childhood. The clinical presentation, diagnosis and histopathological characteristics have been extensively studied; however, reports on the ultrastructure and histogenesis of this lesion are scanty and inconclusive. The case to be discussed is that of a 10-year-old male who presented with a cardiac rhabdomyoma occupying almost the entire ventricular apex. Ultrastructurally, the rhabdomyoma cells have a central, deeply-indented nucleus surrounded by an admixture of mitochondria and sarcomeres. The remainder of the cytoplasm is occupied by pools of glycogen granules, randomly-orientated myofibrils and small mitochondria. Intercellular junctions are numerous and consist of alternating zonula occludens and macula adherens. Typical satellite cells, sharing a common basement lamina are seen apposed to the rhabdomyoma cells. It is tempting to postulate that the proliferation of the rhabdomyoma cells is accomplished by differentiation of satellite cells, a process known to occur in skeletal muscle. Ultrastructurally, the rhabdomyoma cells are indistinguishable from Purkinje cells. The presence of Purkinje-like cells in ectopic locations within the heart and their association with satellite cells is likely a form of embryological atavism.

Child↗