Biomedical subjects
Publications and source records attributed to W H Davis.
Osseointegrated implants placed prior to maxillary downgrafting were utilized to stabilize the repositioned maxilla and interpositional bone graft. Eleven-month follow-up revealed complete healing of the 1.5-cm osteotomy gap and no maxillary relapse. Implant stabilization may be one solution to the relapse associated with inferior repositioning of the maxilla.
Patients with terminal cancer may have a series of severe and dehumanizing physical and psychologic symptoms. To improve symptom control in the final days and hours of life, we administer intravenous barbiturates continuously to provide heavy sedation or continuous somnolence. Titrated dosage is then reduced to a minimum, after a desired steady-state has been achieved. Improved symptom control is provided, and the patient's dignity is maintained until death.
Reconstruction of the severely resorbed mandible has long been a problem. Restoration of function and strength has been impaired by the lack of long-term retention of various bone grafting modalities. The use of hydroxyapatite as a scaffolding material to prolong the retention of grafted bone may hold promise of longer term strengthening by bone grafts. To allow the use of osseointegrated implants with this HA-bone grafting, porous HA (Interpore 200) was used in two patients. Although the 1- and 2-year follow-up of these patients is encouraging, further investigation is needed.
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Autologous onlay rib grafts in 22 patients were evaluated for bone remodeling patterns. The patients had been followed up for four to ten years; the mean was 6.2 years. The unquantitated increase in bony mass of the mandible, with altered ridge form and subsequent soft tissue surgery, provided consistent, predictable results and return to excellent denture function with long-term stability.
The effect of magnesium, given orally as enteric-coated magnesium chloride tablets, on the ECG of 25 randomly selected patients was investigated. Each patient, who served as his own control, was given 4--6 tablets, each containing 0,5 g MgCl26H2O, at night for periods varying from 6 weeks to 2 years. Findings included (i) a statistically significant decrease in OTc and QUc intervals; (ii) a progressive shortening of QTc and QUc intervals with continuing therapy; (iii) reversion to normal of ECG abnormalities, especially of ST segments and T waves.
McCutchen's miniviscometer is a Couette-type instrument that requires only 0.2 ml of synovial or other test fluid. The modification described here adds to the capabilities of the original: control of temperature good to +/- 0.2 degrees C; increase of the maximum measureable viscosity at low shear rates (20 sec-1) to 3000 centipoise; and expansion of the usable range of shear rates to (20--1500 sec-1. The device is rugged and data are reproducible to +/- 1.2% (S.D.) of the mean over the full range of shear rates.
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The two cases presented here illustrate advantageous uses of orthopedic-type craniomandibular headgear. Both cases demonstrate the use of headgear for postoperative cephalad movement of the maxilla. In Case 1 the use of headgear accomplished 6 mm. of anterior maxillary cephalad movement and 3.5 mm. of posterior maxillary cephalad movement. In Case 2 the use of postoperative headgear accomplished 8 mm. of anterior maxillary cephaled movement and 6.25 mm. of posterior maxillary cephalad movement. Table I indicates the duration of intermaxillary immobilization and the ensuing time that the cranial traction appliance was used. Fig. 10 illustrates the profile changes for Cases 1 and 2.
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A two-year follow-up was made of twenty-one impacted, mesially inclined mandibular molars which were surgically uprighted and splinted with autogenous bone grafts. There were two instances of follicular cysts in the adjacent impacted third molars and two instances of supereruption of uprighted teeth. With these exceptions, all uprightings were successful according to the criteria of continued root growth, normality of pulp chambers, normal periodontium, and normal contiguous structures.
The technique of spin trapping has been applied to the gas phase of cigarette smoke to identify and quantify the radicals present. It was found that radicals could be trapped only if the smoke was filtered. Three spin traps were used: N-tert-butyl-alpha-phenyl nitrone (PBN). 5,5-dimethyl-delta1-pyrroline-1-oxide (DMPO) and alpha-[3,5-di-tert-butyl-4-hydroxyphenyl)-N-tert-butyl nitrone (OHPBN). From the electron spin resonance (ESR) splitting constants of the radicals produced by the reaction of smoke radicals with the spin traps and also from the effec of varying the path length between the cigarette and the spin trap solution, it is concluded that three types of signals are observed. Type I signals indicate the presence of oxygenated radicals which appear to be a mixture of alkoxy radicals (RO) and aroyloxy (ArCO2-) radicals. Our data do not allow conclusions about the nature of the R or Ar groups in these two oxy radicals; however, considerations based on lifetimes suggest that the R group probably is tertiary. Type II and III signals are not typical spectra of spin adducts. Instead, we believe they result from reaction of smoke (and probably radicals in smoke) with the PBN spin trap and indicate that smoke has the ability to effect one-electron oxidations. Only type I signals are observed with DMPO and OHPBN. A quantitative study shows that 4 x 10(14) spins/puff are present in the smoke, in contrast with the result of a recent study which used a very different method for determining the radical content of smoke. A discussion of the nature of the radicals in smoke and some tentative conclusions are presented.
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Results of ten cases are reported to indicate the bone augmentation that may be expected in three to six years using transoral rib grafting. Some augmentation was present in all cases. This is an improvement over the continued resorption that would have taken place in these already thin mandibles. Function was improved in all cases. This modality falls short of the ideal aid to these patients, but is an available holding procedure.
The boundary lubricating ability of eleven synovial fluids was measured in a miniaturized latex--glass test system. The specimens were obtained at necropsy from knees in which the degree of degenerative joint disease varied from none to very severe. The lubricating ability of the fluid was independent of the viscosity over a wide range of shear rates. It was not diminished even in advanced lesions. In two additional fluids, the mucin clot was poor; the lubricating ability of one of these was compromised. Thus, although degenerative joint disease, during its quiescent stages, is not associated with defective synovial lubrication, the possibility that transient defects might lead to cartilage wear during life has not been excluded. The measurements are believed to be valid indicators of boundary lubricating ability under physiological conditions despite the fact that the test surfaces were not cartilaginous and the loading was relatively low (up to 47 pounds per square inch).
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