An investigation of two opaque modifiers relative to their color stability and bond strength after repeated firings with two ceramometal systems
Sun, Arthur Fang-Shuo
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A relatively sensitive economic and simple bioassay system with reliable results for studying bone resorption was developed based on the ability of parathyroid hormone (PTH) to mobilize measurable amounts of C superscript 40 from 4 day old mouse calvaria maintained in organ culture. The system utilized paired half-calvaria for treatment and control comparison. From the results it was concluded that in the bioassay system PTH induced bone resorption was best accomplished with 20% heat-inactivated horse serum in BGJ subscript b medium and incubated for 6 days in 5% CO subscript air. The major improvements of this bioassay system are: (1) increased sensitivity, (2) increased efficiency, and (3) reduced cost. By using the Corning M940 analyzer for measuring Ca superscript 40 most of the restrictions of a conventional calcium bioassay system were eliminated. The study of the thiophene compound 5-Bromo-2-Thiophene-carboxaldehyde (5-BrTc) showed that both parathyroid hormone and prostaglandin E subscript 2 can be antagonized by BrTC in vitro. The findings have two important implications. First, it is well known that PTH is a potent systemic mediator of bone resorption and prostaglandin E subscript 2 is a potent local stimulator of bone resorption. The thiophene compound BrTc has the unique ability to inhibit bone resorption stimulated by two different mediators. Thus it has the potential for use systemically to treat osteoporosis and Paget's disease. At the local level it could be of use in controlling bone loss and hypercalcemia commonly seen in cancer patients with overt metastatic tumors and in the treatment of other local bone disease in which humoral mediators are diagnosed. Second, the cyclic AMP hypothesis for PTH and PGE subscript 2 has been further supported by these results. The fact that both PGE  and PTE can stimulate cyclic 3',5' - adenosine monophosphate (cAMP) concentration. Thus on the basis of this limited investigation it is possible that the action of the thiophene compounds may be the degradation of cAMP.
PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact firstname.lastname@example.org.Includes photographs.Thesis (D.Sc.D.)--Boston University, Henry M. Goldman School of Graduate Dentistry, 1985 (Prosthodontics)Bibliography : leaves 163-177.
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