Biomedical subjects
Publications and source records attributed to D Millett.
A case is described where a permanent mandibular incisor was found to be dilacerated. Histological examination of the extracted tooth was consistent with trauma, although there was no supporting history. These findings are discussed and the orthodontic implications are considered.
Explore the source record for details and available documents.
A laboratory investigation of the shear bond strength of stainless steel brackets applied with glass ionomer cement (Ketac-Cem) and a conventional adhesive (Right-on) is described. Sandblasting of the bracket base was undertaken in half of the sample bonded with Ketac-Cem and produced a significant reduction in the probability of failure relative to the unsandblasted sample. Brackets with sandblasted and unsandblasted bases, bonded with Ketac-Cem were subjected to mechanical fatigue in a ball mill for a total of 20 hours. Mean survival time (MST) was then calculated for each group and was found to be significantly improved by sandblasting of the bracket base (P < 0.01).
Destruction of periarticular and periprosthetic bone by activated macrophages, a process often termed "macrophage mediated osteolysis," is recognized as a leading mechanism of aseptic arthroplasty failure. To develop effective interventional approaches and increase the longevity of implanted joint prostheses, the pathobiology of activated human-synovium-derived macrophages needs to be better characterized. The first step toward achieving this research objective is the acquisition of pure populations of macrophages from human synovial tissue. A simple, fast, and highly efficient method for isolating a relatively pure population of macrophages from periprosthetic tissue received from either primary or secondary arthroplasty is presented. This technique uses murine monoclonal antibodies (IgG) that recognize a phagocyte-specific marker, CD68, for primary binding, and sheep anti-murine IgG antibodies bound to polystyrene-coated magnetic microspheres for secondary binding. While the primary antibody specifically labels CD68-positive phagocytes in the digestion of synovial and periprosthetic tissue, the secondary antibody bound to polystyrene-coated iron oxide beads facilitates the removal of CD68-positive cells from CD68-negative cells by anchoring the former with a magnet. This protocol requires centrifugation only in the washing steps, which reduces the frequency of cell death and altered cell morphology. The patient population includes three primary and eight revision arthroplasties. The tissue macrophage isolation protocol yielded on average 4 x 10(5) cells/g tissue, of which 91% were viable nonspecific esterase positive macrophages. The experimental results suggest that immunomagnetic beads coupled to anti-CD68 enable the isolation of a purified population of resident tissue macrophages suitable for further biologic characterization.
Suburothelial injections of particulate poly(tetrafluoroethylene) (PTFE) is becoming a widely accepted treatment for a number of urological disorders. Because little is known about the long-term histologic morphology of the injection site, this animal study was performed. Three populations, each consisting of two mongrel dogs, five New Zealand White rabbits, and 10 BALB/c mice, were injected with poly(tetrafluoroethylene) particulate in a glycerine carrier (Polytef Paste) and were followed for a period of 1 week, 3 months, 6 months, and 1 year. Mice received one subcutaneous dorsal injection each, rabbits received two subareolar injections each, and dogs received three subareolar injections each in addition to two periurethral injections. Histologic examination of the biopsy sites revealed a persistent chronic inflammatory reaction with progressive growth of the involved tissue volume. In addition to giant cells and macrophages, lymphocytes became apparent at 3 months and constituted up to 40% of the cellular infiltrate by 1 year. Plasma cells were also noted at the 1-year period in the rabbit model. The progressive growth of the inflammatory pseudo-tumors evoked by injected PTFE may compromise the long-term safety of certain urological procedures involving particulate PTFE.
The reliability and validity of four methods of assessing skeletal pattern (Reidel's method, Eastman correction, Ballard's method, and 'Wits' analysis) from cephalometric tracings have been examined, and the levels of agreement between them investigated. The possibility of the Y-axis length and SN-Y-axis angle having a bearing on the skeletal pattern was also examined. Strong correlation was found between the four methods considered. Ballard's method correlated very closely with Reidel's method, and like 'Wits' method, is not as unreliable as previously reported. Measurement of the SN-Y-axis angle was not found to be of benefit to the assessment of the anteroposterior dental base relationship. Reidel's method, which is the easiest to apply, is recommended as the method of choice, and routine application of the Eastman correction is not recommended.
Periprosthetic macrophages were isolated from the synovium of primary and revision arthroplasty patients. Inflammatory activity was determined by the level of superoxide (O2-) production de novo and in response to phorbol myristate acetate (PMA) stimulation. Nonstimulated primary arthroplasty-derived macrophages produced 2.54 +/- 2.04 pmoles of O2-/minute/10(5) cells. When identical reaction tubes were stimulated with PMA, O2- levels increased to 5.76 +/- 3.77 pmol of O2-/minute/10(5) cells. Nonstimulated revision arthroplasty-derived macrophages produced 3.26 +/- 2.02 pmol of O2-/minute/10(5) cells during this ten-minute time period. When identical reaction tubes were stimulated with PMA, O2- levels increased to 3.98 +/- 2.52 pmol of O2-/minute/10(5) cells. The difference in the ratio of O2- production in response to stimulation between primary and revision groups was statistically significant. The observation of a chronic moderate level of activation and the lack of responsiveness to a potent stimulator suggests that macrophage inflammatory activity is down-regulated in periprosthetic synovium.