Biomedical subjects
Publications and source records attributed to M Spector.
1. An inert porous vehicle can be successfully used to attach endosseous dental implants to surrounding alveolar bone. 2. Implant size and the width of keratinized gingiva surrounding the implant are critical to the success of the implant. 3. Radiography and pocket depth are useful indicators of the status of porous endosseous roots, while mobility is not.
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The mechanical properties of porous polysulfone (PSF) were determined and its performance as a surface coating on orthopedic and dental implants evaluated. Ten coated femoral prostheses were implanted in nine dogs. A second series of four uncoated "control" prostheses and all of the acetabular cups were implanted using conventional bone cement techniques. Six porous PSF coated tooth roots were implanted in healed mandibular premolar extraction sites in three Rhesus monkeys. The shear strength of porous PSF (6 MPa) was comparable to that of trabecular bone. Pushout tests of 1cm. thick sections of the prostheses yielded interfacial shear strength values over 1.4 MPa for the PSF coated hips after 14 weeks and mean values under 0.7 MPa for the bone cemented specimens after 3 and 36 weeks. Bone and fibrous tissue was identified in the pores of coated specimens. Preliminary clinical evaluation of the functioning dental implants revealed zero mobility and other favorable clinical and radiographic indications after 2 months.
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Ultrastructural studies of human prostatic corpora amylacea and corpora calculi, and prostatic calculi were conducted in order to delineate their etiology and pathogenesis. Scanning electron microscopy was employed in conjunction with histology and transmission electron microscopy in the study of prostatic tissues and concretions obtained from 21 individuals. Results confirmed that desquamated acinar cells contribute to the formation and growth of corpora amylacea. A variation in density of the matrix of the matrix of the corpora produces a laminated structure. The deposition of hydroxyapatite crystallites in corpora amylacea leads to the formation of corpora calculi. Further growth and mineralization of corpora calculi lead to the development of the more clinically significant prostatic calculi. Small spherical aggregates (from 0.5 to 5 micron in diameter) of hydroxyapatite crystallites are a prevalent constituent of the corpora and prostatic calculi. Similar spherical aggregates of hydroxyapatite crystallites have also been identified in urinary calculi and other pathologic tissues suggesting similar mechanisms of mineral precipitation.
A high-modulus polymer, polysulfone, was evaluated as a porous bone implant material. The bone ingrowth into canine cortical pellets of sintered polysulfone particles was assessed by microradiography and histology. The shear strength of the porous polysulfone-bone interface was determined by push-out and pull-out tests of cortical and trochanteric implants, respectively. Results indicated that the bone ingrowth into porous polysulfone specimens proceeded in such a fashion as to mimic the normal repair at the site. Mechanical testing of cortical and cancellous implants revealed that the interfacial shear strength of the porous polysulfone-bone composite was similar to that achieved using porous metals.
The ultrastructure of human urinary calculi was studied using scanning and transmission electron microscopy. The hydroxyapatite constituent of the stones was often present in the form of sperical aggregates of the minute apatite crystallites (1 to 10 mu in diameter). In most cases, the sperical apatite deposits consisted of concentric lamellae of crystallites. The spherical apatite deposits, described in detail for the first time in urolithiasis, were similar to those found in a variety of calcified tissues including nephrocalcinosis and malakoplakia.
Selective discrete intraaxoplasmic deposits of hydroxyapatite crystallites were observed in adult male rats subjected to experimental trauma to the lumbosacral spinal cord. Although previously unreported in spinal cord trauma, the presence of these deposits in minimally altered axons and during the early posttrauma period suggests that such selective calcification may be of more than secondary significance. In view of the current emphasis on cytotoxicity of calcium, especially in relation to axonal degeneration, an evaluation of the role of calcium in augmenting traumatic spinal cord necrosis is warranted.
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In this series of gonadoblastomas it appeared that the germ cells were the motivating force underlying either tumor proliferation or regression. The ultrastructural morphology confirmed the presence of undifferentiated gonadal cells with active steroid synthesis by the interstitial cells. The Call-Exner-like bodies which showed extensive calcification were composed of basement membrane material containing a sulfated mucosubstance. A histochemical comparison with the noncalcifying Call-Exner bodies of a granulosa-cell tumor differed only in their glycoprotein content. The calcium deposits were identified as oriented hydroxyapatite crystals by electron diffraction, and it is proposed that the basement membrane material serves as a nucleation site for calcification. High serum testosterone levels were correlated with the presence solely of interstitial cells in one case. The finding of a gonadoblastoma without the presence of a Y chromosome contradicts earlier proposals concerning the requirement of a Y chromosome for germ cell proliferation.
The purpose of this study was to delineate the process by which bone comes to fill the pores of porous high-density polyethylene (PHDPE) implants. PHDPE (450 mu pore size) pellets 4 mm in diameter and 1 cm long were implanted into the femurs of dogs. A bone biopsy procedure was utilized to obtain PHDPE pellets implanted for periods of 3 days through 8 weeks. A one-year biopsy specimen taken from the PHDPE coating on the stem of a canine total-hip prosthesis was also studied. The results demonstrated that significant amounts of bone formed within the PHDPE pellets as early as 14 days after implantation. Bone was identified throughout the specimens after 4 weeks. After 6 weeks, the tissue in hematopoietic marrow. Scanning electron microscopy was utilized in conjunction with light microscopy and microradiography to study the ultrastructural features of the bone ingrowth process.
The results of the present study demonstrate the utility of the scanning electron microscope for characterizing the ultrastructure of the initial tissue infiltrate in porous polyethylene implants. Shortly after implantation a thin noncellular fibrous-like coating was observed to form on the pore surface. The cells observed in the polyethylene pellets 3 days after implantation were generally consistent with what one would expect to see in a hematoma. As early as 14 days after implantation much of the blood clot was replaced by newly formed bone spicules. Tissue shrinkage accompanying dehydration of the specimen for scanning electron microscope study although a disadvantage occasionally proved useful in that it provided the opportunity to study the internal surface of the fibrous coating when separated from the surface of the implant. Less shrinkage was observed in implants whose pores were filled with bone spicules.
Lattice (Fourier) images of crystallites in human bone and teeth, and calcified atherosclerotic plaque were studied using high resolution transmission electron microscope techniques. The lattice images observed in the normal and diseased calcified tissue were compared with the images of synthetic hydroxyapatite crystallites.
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