PubMed Health⌕ Search

Biomedical subjects

K W Chapman

Publications and source records attributed to K W Chapman.

At least 19 recordsLinked to original sources
PubMed1994

Reducing microleakage in Class II restorations: an in vitro study.

The aim of this in vitro study was to evaluate four methods of reducing the marginal microleakage of directly placed Class II composite resin restorations. Mesio-occlusal and disto-occlusal preparations with all margins confined to enamel were placed in extracted human molars. The teeth were restored with one of four techniques using multi-incremental placement, stored for 24 hours in 37 degrees C water, thermocycled, and placed in a dye solution. The teeth were sectioned in a mesiodistal direction through the restoration and evaluated for microleakage at the gingival margins. Restorations placed in conjunction with an enamel bonding agent demonstrated severe microleakage. Marginal microleakage was reduced by the use of an extended base of visible light-cured glass-ionomer cement, a BondAband, or a dentinal bonding agent.

Analysis of Variance↗
PubMed1992

Pilot scale production of pyrogen-free human hemoglobin for research.

A pilot scale production facility for the preparation of 20 to 30 liters of stroma-free hemoglobin is described. The system is capable of producing pyrogen-free solutions for research purposes. It is not certified for production of parenteral solutions for human use, but the plan could be implemented to meet standards for such materials. Products of the facility should be of adequate quality to address most of the toxicity and efficacy issues facing further development of hemoglobin-based red cell substitutes.

Biotechnology↗
PubMed1992

Pneumatic versus hand condensation of amalgam: effect on microleakage.

This study compared two techniques of amalgam condensation for effect on early microleakage. Class V preparations were restored with a high-copper amalgam using pneumatic condensation or conventional hand condensation. Significantly less microleakage was observed when pneumatic condensation was used. Further, pneumatic condensation proved equally effective in reducing early microleakage whether or not a dentinal sealant was used as an intermediary.

Air Pressure↗
PubMed1989

Different hematologic responses to hypoxia in Sherpas and Quechua Indians.

Previous studies of the erythropoietic response to hypoxia in high-altitude natives suggest that the hematocrit and hemoglobin values in Himalayan natives (Sherpas) are lower than expected for the altitude, perhaps because of a genetic adaptation. However, differences in sampling techniques and experimental methods make comparisons difficult. Our studies were carried out to compare the erythropoietic response with the same altitude in age-matched natives of the Himalayas and Andes by the same experimental techniques. Healthy male subjects were selected in Ollagüe, Chile (n = 29, 27.3 +/- 5.9 yr) and in Khunde, Nepal (n = 30, 24.7 +/- 3.8 yr). Both of these villages are located at 3,700 m above sea level. Hematologic measurements confirmed lower hematocrit values in Nepal (48.4 +/- 4.5%) than in Chile (52.2 +/- 4.6%) (P less than 0.003). When subjects were matched for hematocrit, erythropoietin concentrations in Chile were higher than in Nepal (P less than 0.01). Detailed measurements of blood O2 affinity in Nepal showed no differences in shape or position of the O2 equilibrium curve between Sherpas and Western sojourners. Our results indicate that although Quechua Indians have higher hematocrits than Sherpas living at the same altitude, nevertheless they may be functionally anemic.

Adult↗
PubMed1984

Characteristics of lympho-myelopoietic stem cells isolated from canine peripheral blood.

If hematopoietic stem cells (HSC) could be separated from peripheral blood, it might be possible to harvest these stem cells for potential clinical use. By leukapheresis techniques, we harvested mononuclear cells (MNC) from peripheral blood and then placed these cells over discontinuous stractan gradients of three densities (1.077 gm/ml, 1.071 gm/ml and 1.066 gm/ml). These separated cells were submitted to colony culture to identify colony-forming-unit activity for granulocyte-macrophage (CFU-C) and T-cell lymphocyte (CFU-L) cell lines. The lightest cells (1.066) contained most of the CFU-C and no CFU-L activity. Heavier cells (greater than 1.071) contained CFU-L and very little CFU-C activity. CFU-L colonies could be distinguished from CFU-C by their density and distinct morphological appearance. In addition, the amount of CFU-C could be increased in the animal by increasing the amount of blood processed (from 3.9 +/- .76 CFU-C/10(6) MNC to 6.7 +/- .35 CFU-C/10(6) MNC). This resulted in an increase of CFU-C collected from 7.6 +/- 2.1 CFU-C/10(6) MNC after the first equivalent blood volume to 22.5 +/- 3.4 CFU-C/10(6) MNC after the third equivalent blood volume processed. These results suggest that leukapheresis and gradient density separation may be useful procedures to obtain HSC.

Animals↗
PubMed1983

Granulocyte progenitor cell (CFUC) harvest by continuous apheresis in dogs. Effects of blood volume and lithium on yields.

The ability to harvest large amounts of hematopoietic stem cells from blood would eliminate the more difficult approach of bone marrow harvest. Unfortunately, concentration of stem cells in the blood compartment is less than 1% of their concentration in bone marrow. Attempts to increase harvest of blood stem cells, as assayed by granulocyte progenitor cells (CFUC), have been only partially successful. Our study confirms previous reports that CFUC can be mobilized into the blood compartment in dogs, but this mobilization is rate-limited. Unlike platelets and granulocytes that are effectively harvested during the first blood volume processed by continuous apheresis, effective CFUC harvest begins during the second blood volume (606 +/- 97.9 CFUC/ml), peaks by the third (740 +/- 30 CFUC/ml), and remains constant through five blood volumes processed (700 +/- 272 CFUC/ml). Since blood CFUC concentration falls at the end of five blood volumes processed (40% of initial values), further continuous apheresis would not be effective. Treatment of animals with lithium did not improve CFUC harvest. These results show that apheresis procedures can be developed to a limited extent to increase the harvest of hematopoietic progenitor and stem cells.

Animals↗
PubMed1981

A matrix band technique for large amalgam cores.

The inability to adapt matrix bands successfully to badly broken down teeth has been a source of frustration to clinicians. Unfortunately, this has often led to therapy involving extractions of strategic posterior teeth because the dentist thinks that the time and effort entailed in restoring the tooth is not practical, or that an attempt to band a difficult tooth would prove futile. The banding technique described here was effective after proper enclosure, length, and gingival adaptation were accomplished, and the occlusal surface of the crown was removed; the technique can make a difficult procedure easier to accomplish.

Crowns↗
PubMed1975

Surgical treatment of chronic dislocation of the sterno-clavicular joint.

The costo-clavicular ligament is always ruptured in dislocation at the sterno-clavicular joint. Anterior, superior or posterior displacement of the medial end of the clavicle may occur. Acute dislocation usually responds to conservative treatment and operation is seldom required. Chronic, or recurrent, dislocation may cause pain and disability on strenuous activity and necessitate surgical treatment. The operation of tenodesis of the subclavius tendon with capsulorrhaphy described by Burrows (1951) has been adopted. The intraarticular meniscus is often damaged and displaced, and may block reduction; its removal is then necessary. In addition, a threaded Stinmann pin transfixing the joint has been found useful to maintain the stability of reduction. The operation has been performed on five patients, four of whom had excellent results. The fifth patient disrupted the repair in a drinking bout shortly after the operation.

Adult↗