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PubMed1996

Effect of specimen fixation method on pullout tests of pedicle screws.

STUDY DESIGN: Experimental axial pullout tests of a new type of pedicle screw were done on cadaveric lumbar vertebrae. The manner in which specimens were secured in the testing apparatus was varied to determined influence of specimen fixation method on the maximum pedicle screw pullout force. OBJECTIVES: To determine the appropriateness of embedding (i.e., potting) spinal specimens in polymer resin (e.g., bone cement or Plastic Padding [Plastic Padding Ltd., High Wycombe, Buckinghamshire, England]) for axial pullout tests of pedicle screws. Several different specimen fixation methods were examined to make recommendations for the standardization of future experimental testing protocols. SUMMARY OF BACKGROUND DATA: Axial pullout of transpedicular screws, although not a likely clinical mode of failure, is a popular experimental testing mode for evaluating screw-bone biomechanics. A wide variety of techniques for securing a vertebral specimen to counter the axial pullout force has been reported (including the use of polymer resin) with a correspondingly wide range in the resulting axial pullout strengths. The possible influence of the specimen fixation method on pedicle screw axial pullout strength has not been addressed previously. METHODS: Axial pullout tests of pedicle screws (DDS, Plus Endoprothetik, Rotkreuz, Switzerland) from the pedicles of 21 isolated lumber vertebral bodies were done using a Model 810 MTS Universal Testing Machine (MTS Systems, Inc., Minneapolis, Minnesota). The specimens were secured in a custom-made vise fixture either as is or after the vertebral bodies were potted in Plastic Padding up to the pedicle origin. Some of the potted specimens were wrapped first in latex to prevent polymer resin intrusion, and the others were unprotected. Pullout tests were attempted on both the left and right pedicles of each specimen, and the maximum pedicle screw pullout force was recorded. Measurement of bone mineral density by means of dual energy x-ray absorptiometry, in addition to macroscopic and scanning electron microscopy histologic analyses, microradiography, and energy dispersive X-ray spectroscopy, was done post-test to assist in the interpretation of the data. RESULTS: The maximum pedicle screw pullout force was found to be dependent on both the bone mineral density and the mode of fixation of the vertebrae. Embedding in polymer resin without protection of the specimen (i.e., latex wrapping) led to several instances of well-documented polymer resin intrusion; in these specimens, mean maximum pedicle screw pullout force was significantly greater than that of specimens secured without polymer resin and that of embedded specimens for which intrusion did not occur. CONCLUSIONS: Polymer resin intrusion can have a significant effect on the biomechanical characteristics of the bone-pedicle screw interface. When polymer resins are used to secure vertebral specimens for in vitro biomechanical tests of the bone-pedicle screw interface, it is important to either prevent intrusion (e.g., with a latex wrapping) or document post-test (e.g., through the methods described in this article) that intrusion did not occur for the specimens included in the analysis.

Aged↗

PubMed2002

How does recombinant human bone morphogenetic protein-4 enhance posterior spinal fusion?

STUDY DESIGN: A rabbit posterolateral intertransverse process fusion model was used to evaluate the effect that different doses of recombinant human bone morphogenetic protein-4 delivered in a porous hydroxyapatite-tricalcium phosphate ceramic had on osteogenesis and spinal fusion. OBJECTIVE: To study the biologic effect and threshold dose of recombinant human bone morphogenetic protein-4 in enhancing spinal fusion. SUMMARY OF BACKGROUND DATA: Biologic manipulation for spinal fusion is an area undergoing active research. The enhancing effects of recombinant human bone morphogenetic proteins 2 and 7 on spinal fusion have been proved, and clinical trials of their application are in progress. Recombinant human bone morphogenetic protein-4 is another osteoinductive protein that has the ability to induce heterotopic bone formation, and its potential for enhancing spinal fusion has not yet been studied. METHODS: For this study, 24 adult New Zealand white rabbits underwent single-level unilateral posterior intertransverse process spinal fusion at L5-L6. The animals were divided into four groups using different graft materials: allograft as well as hydroxyapatite-tricalcium phosphate augmented with 0, 1.25, and 5 microgram of recombinant human bone morphogenetic protein-4, respectively. The local changes were evaluated by sequential radiograph, manual palpation, histomorphology, and microradiography. RESULTS: At week 7, ossification in the intertransverse process area ceased in groups without recombinant human bone morphogenetic protein-4, whereas active multicentric endochondral bone formation was demonstrated in groups with this growth factor. The success rate of contiguous bony bridging was found to correlate positively with the dose of recombinant human bone morphogenetic protein-4. CONCLUSIONS: Recombinant human bone morphogenetic protein-4 effectively enhances new bone formation and accelerates fusion in the rabbit posterolateral posterior spinal fusion model. The effective dose of recombinant human bone morphogenetic protein-4 is 10 times lower than the reported dosage of recombinant human bone morphogenetic proteins 2 and 7.

Animals↗

PubMed1997

Functional and morphological outcome of knee joint transplantation in dogs depends on control of rejection.

BACKGROUND: The reconstruction of massive osteochondral defects extending to weight-bearing joints remains a surgical challenge. Total knee joint transplantation has been performed experimentally, but these studies lacked prospective evaluation of functional outcome, graft vascularization, and graft viability. METHODS: Replantation and transplantation of vascularized knee joints was performed in dogs (n=4 per group), comparing functional and morphological results during a 6-month follow-up. RESULTS: All replant recipients and three transplant recipients survived the 6-month follow-up period. At this time, duplex sonography and angiography revealed patent anastomoses in all animals. Increases in volumetric flow rates and vascular collateralization were observed in allografts, as compared with replanted joints (100+/-16 ml/min vs. 31+/-15 ml/min at 6 months after transplantation). Bone fusion at the graft-host interface was verified by fluorography in all animals at 3 months after transplantation. Six months after transplantation, microradiographies and computerized tomographies revealed spongialization of the cortical bone and filling of the medullary space by trabecular bone in transplanted joints. Such alterations were not detectable in replanted joints. Chondrocyte viability exceeded 80% in all but one transplanted joint. Lymphocyte infiltration of synovia and arterial walls was detected in all transplanted joints, suggesting the presence of chronic rejection. Weight-bearing capacity recovered in all replanted animals (weight-bearing index before transplantation: 0.499+/-0.080; 6 months after transplantation: 0.38+/-0.16) but only in two of four transplanted animals (weight-bearing index 6 months after transplantation: 0.37, 0.28, and 0.00). CONCLUSIONS: These data demonstrate the potential of joint grafting and the critical dependence of allotransplantation on the control of rejection.

Angiography↗

PubMed2001

Prevalence of otosclerosis in an unselected series of temporal bones.

BACKGROUND: Histologic otosclerosis is a disease process without clinical symptoms or manifestations that can be discovered only by sectioning of the temporal bone at autopsy. Clinical otosclerosis is otosclerosis at a site where it causes conductive hearing loss by interfering with the motion of the stapes or of the round window membrane. Various authors have studied the prevalence of histologic otosclerosis on laboratory collections of temporal bones. Some 12% to 15% of temporal bones with histologic otosclerosis have demonstrated stapedial fixation. Using these figures for calculating the prevalence of clinical otosclerosis gives an extrapolated clinical prevalence of 0.99% to 1.2%. This does not correlate well with the clinical data on otosclerotic families, from which a clinical prevalence of 0.3% has been estimated. OBJECTIVE: To study the prevalence of histologic otosclerosis in an unselected series of temporal bones. STUDY DESIGN: During a 1-year period, 118 consecutive pairs of temporal bones of deceased patients at a tertiary care center were collected to determine the prevalence of otosclerosis. Although histology remains the gold standard for evaluation of otosclerosis, the gross observation of temporal bone slices combined with microradiography was used to screen for otosclerotic lesions more rapidly and with a lower cost/benefit ratio. The temporal bones, which were suspected of having otosclerosis with these techniques, were further analyzed by conventional histology. RESULTS: 2.5% of the 236 temporal bones (or 3.4% of patients) studied demonstrated histologic otosclerosis. CONCLUSIONS: Although the prevalence of 2.5% is much lower than previously published figures on histologic otosclerosis, the extrapolated data (extrapolated clinical prevalence = 0.30% to 0.38%) correlate well with clinical studies of otosclerotic families. The previous studies based on laboratory collections were likely biased by hearing loss or other otologic diseases.

Adolescent↗

PubMed1998

Characterization of windows and filters for coherent X-ray beamlines.

Beryllium windows and graphite heat absorbers used in coherent X-ray beamlines must be optically flat. If the optical path through the window varies by more than lambda/4, the X-ray wave front will be distorted after passing through the window, and the divergence of the X-ray beam may be increased. This reduces the beam coherence. Beryllium, graphite and Kapton films have been tested using ultra-small-angle X-ray scattering. Wave-front distortion was also directly observed by means of phase-contrast X-ray microradiography. The measured increase of angular divergence is about 4 micro rad. The wave-front distortion is larger than 2pi (optical path difference of lambda). These are serious problems for utilizing coherent X-ray beams.

Journal Article↗

PubMed1978

In vitro caries related to marginal leakage around composite resin restorations.

The histology of caries-like lesions around composite resin restorations with and without marginal leakage has been studied. The lesions were generated from bacterial plaque growing in an in vitro system. Marginal leakage was prevented by an acid etch technique. Ground sections of the experimental teeth were studied by polarized light and microradiography. The caries lesions penetrated along conventional class V restorations with marginal leakage while restorations bonded to an acid etched enamel surface totally prevented this ingrowth.

Acid Etching, Dental↗

PubMed1980

The structure of experimental in vitro lesions around glass ionomer cement restorations in human teeth.

Class V cavities were prepared at the amelo-cementum junction in sixty-eight extracted human teeth. Fifty-one were filled with glass ionomer cement (ASPA). 'Secondary carious' lesions were produced around thirty-five of the restorations by exposure to acidified gelatin. Thirty-three teeth served as controls of the effect of the preparation procedure, the conditioner, the ASPA liquid and the filling material proper on the cavity walls. Sixty 120 micrometers-thick longitudinal sections from the teeth with the restorations in situ were studied by polarized light microscopy and microradiography. The glass ionomer cement caused by itself a narrow zone of increased radiopacity in the dentine cavity wall. The 'secondary caries' pattern consisted of a subsurface outer lesion and a subsurface wall lesion as observed previously in corresponding experiments with silicate fillings. Outer lesions in enamel were more frequent than with silicate cement. In the cementum all the experimental teeth showed outer lesions. The wall lesions extended only slightly beyond the level of erosion of the restorations. Between the wall lesions (in dentine) or outer lesions (in cementum/dentine) and the surface of the cavity wall, a zone of increased radiopacity was found, assumed to be due to reprecipitation of Ca and P promoted by release of fluoride from the filling material.

Acid Etching, Dental↗

PubMed1983

Inhibition of experimental nephrocalcinosis with a prostaglandin synthetase inhibitor.

Nephrocalcinosis was induced in a group of experimental rats by means of intraperitoneal injections of 10% calcium gluconate. Two further groups of rats were treated with indomethacin and flurbiprofen (Froben) before receiving the i.p. calcium gluconate, to study the effects of prostaglandin inhibition on the process of renal parenchymal calcification. Tissue calcification was studied by means of contact microradiography and histology. Quantitative calcium analysis was by means of energy dispersive analysis of X-rays (EDAX). There was a marked inhibition of cortical nephrocalcinosis and a significantly reduced calcium concentration (P less than 0.005) in the animals treated with a prostaglandin inhibitor compared with the animals given i.p. calcium gluconate alone. This study suggests that prostaglandins are involved in the process of renal parenchymal calcification and may be aetiologically significant in the pathogenesis of stone formation.

Animals↗

PubMedDate not supplied

Healing of mandibular body osteotomies after plate and intramedullary pin fixation.

Osteotomies were created in the left body of the mandible of nine dogs and immediately stabilized with either a six hole dynamic compression bone plate or an intramedullary pin. Cortical bone healing and vascular supply were evaluated at weeks 2, 5, and 10 by microradiography, microangiography, and correlated histology of selected mandibular slices. Perforating arterioles from the buccal mucosa maintained vascular supply to rostral mandibular segments. The mandibular body rostral to the osteotomy site and caudal to the canine tooth suffered an interruption of vascular supply that was replaced by a temporary extraosseous supply during healing of the osteotomy. Intramedullary pin placement resulted in destruction of rostral teeth. There was an inflammatory response around the rostral portion of all intramedullary pins. Osteotomy sites involving tooth roots resulted in no disruption of the normal vascular or neural structures of the tooth pulp.

Animals↗

PubMedDate not supplied

Effects of plate luting on cortical vascularity and development of cortical porosity in canine femurs.

A 4.5 mm, six hole dynamic compression plate was applied to the lateral aspect of one femur in 16 dogs. The plate was luted with polymethylmethacrylate (PMMA) in eight dogs. Four dogs each from the luted and nonluted groups were euthanatized at weeks 5 and 10. Plated femurs were sectioned and processed for microradiography, microangiography, and correlated histology. At week 5, there was decreased vascularity in the outer one third of the cortex beneath luted plates and normal to increased vascularity in the inner two thirds of the cortex. Increased cortical porosity and a decreased percentage of osteocyte-filled lacunae were found in the cortex beneath luted plates at week 5. At week 10, vascularity was increased throughout the cortex under luted plates. Under nonluted plates, there was normal to increased vascularity at both time periods. Luting a bone plate with PMMA decreased vascularity to the outer one third of the cortex beneath the plate at week 5, and resulted in accelerated resorption of bone.

Animals↗

PubMed2004

Sinus floor augmentation with simultaneous placement of dental implants in the presence of platelet-rich plasma or recombinant human bone morphogenetic protein-7.

The aim of the present study was to evaluate the possible benefit of platelet-rich plasma (PRP) in sinus grafting as compared with recombinant human bone morphogenetic protein-7 (rhBMP-7). For this purpose, we performed a bilateral sinus augmentation with anorganic bovine bone and simultaneous insertion of a titanium screw implant in five miniature pigs. Six hundred microliters of PRP and 15%-vol. autologous bone, which was collected with a trap during preparation of the implant recipient site, were added to the right sinus and 420 microl rhBMP-7 to the left sinus. A polychrome sequential labeling was performed. The animals were sacrificed 6 weeks after surgery. Undecalcified ground sections were evaluated by microradiography, digitized histomorphometry and under fluorescent light. The mean bone-implant contact using rhBMP-7 was 45.8% and 5.7% under PRP (P=0.002). The mean height of newly mineralized bone in the augmented area using rhBMP-7 amounted to 8.3 mm as opposed to 3.6 mm under PRP (P=0.013). Using PRP, the mean area of the newly formed bone was enhanced (51.3%) as compared with rhBMP-7 (33.1%); however, this difference was not statistically significant (P=0.081). In conclusion, under the selected experimental conditions the use of rhBMP-7 led to superior outcomes with regard to the osseointegration of dental implants and the height of new bone as compared with the use of PRP.

Animals↗

PubMed2006

Changes of mineralization of free autogenous bone grafts used for sinus floor elevation.

For augmentations before implant placement in areas of minor bone quantity, autogenous bone is considered the reference to all bone substitutes used alternatively. Autogenous bone transplants originate from various donor areas and can be prepared in different ways before augmentation. They may either be used as block grafts or may be milled to granules that can be used solitarily or in combination with a bone substitute. In a prospective study, 61 patients of the Maxillofacial Surgery Department of our University receiving two-stage sinus floor elevation because of insufficient bone supply were randomly selected. At first-stage surgery, the local augmentation procedure, monocortical probes were obtained on the site of bone harvesting. At second-stage surgery, the implant insertion 6 months after the elevation procedure, bone cores were harvested in the areas of implant placement. Donor regions were the following three areas: the posterior (N=28) and anterior pelvic region (N=15) and the chin region (N=18). The implanted bone in all three groups was particulated to granules of 2-3 mm(2) using a bone mill. All biopsies were analyzed by means of microradiography. The anterior pelvic bone grafts showed a mineralized tissue grade of 35.1+/-7.6% before milling and augmentation. The posterior pelvic bone grafts exhibited a mineralization of 30.7+/-9.5% and the chin bone grafts 74.6+/-8.6%. At second-stage surgery after 6 months, the mineralization was 36.1+/-7.59% in the areas where bone grafts from the anterior pelvic crest were used. Probes harvested from sites with posterior pelvic bone augmentations showed a mineralization rate of 34.5+/-6.5%, and sites were chin bone grafts were applied expressed a mineralization of 54+/-8.6% (P=0.003 compared with the pre-operative value). The comparison of the microradiographical results demonstrated significant differences in the mineralization grades depending on the origin of the graft. The origin of the grafts and their remodeling influenced the mineralization rates found at 6 months. How these data may influence the long-term clinical outcome considering implant survival and bone resorption has to be examined in further long-term studies.

Bone Density↗

PubMed1991

Approximal caries diagnosis using fiber-optic transillumination: a mathematical adjustment to improve validity.

Several studies were conducted recently to evaluate the use of Fiber-Optic Trans-Illumination (FOTI) in the diagnosis of approximal carious lesions. All these studies utilized radiographic readings to validate the FOTI diagnoses. Other investigations studied the value of radiographic readings using more solid validating techniques, which made it possible to judge the true state of decay, such as histology, cavity preparation and microradiography. In this study, data from both types of studies were used to estimate the validity of FOTI diagnosis of approximal caries relative to the true status of decay through correction for radiographic misclassification. The results indicate that particularly the sensitivity of FOTI diagnosis has yet to be determined.

Dental Caries↗

PubMed1978

Histology of benign virus induced tumors of the skin.

The majority of findings in relation to warts have been passed on from one textbook to the other since the end of the last century. More recent studies have been carried out with the electron microscope. But information is lacking as to histology, histochemistry, examination with the phase-contrast microscope, with the interference microscope, microradiography and other new techniques. Warts are a proliferation of the epidermis caused by a virus, and we know that the culprit acts in the epidermis itself. Warts are acanthomas, and a transition to malignancy is possible in predisposed persons. It is most remarkable that in the malignant tumors of epidermodysplasia verruciformis, no virus could be found. As the demonstration of viruses with the electron microscope and other techniques cannot be made as a matter of routine, we have to search for a simpler method with the light microscope. With the application of more elaborate procedures, new information about epidermal proliferation will certainly be obtained.

Carcinoma, Squamous Cell↗

PubMed1980

Detecting dentinal sclerosis in decalcified sections with the Pollak trichrome connective tissue stain.

The supply of young human teeth for controlled human pulp studies is inadequate. Dentinal sclerosis in older teeth modifies the expected pulpal responses. Decalcification, necessary to interpret pulpal responses, destroys the primary evidence of sclerosis. At present we are unable to detect the degree of sclerosis and the pulp response in the same preparation. Valid interpretations on older teeth cannot be accomplished until this problem is resolved. Fifty-seven teeth, normal and carious, representing a wide age span were fixed, embedded in Bioplastic and sectioned with the Bronwill Model No. 77 through the middle of the M-D plane on the labio-lingual plane to obtain an undecalcified ground section for examination with reflected and transmitted light and Faxitron 805 microradiography. The remaining portions of the tooth were decalcified, processed in paraffin and subjected to a variety of histochemical reactions including the Pollak trichrome stain. The Pollak trichrome and the Pollak trichrome solution No. 6 modification stains provided the greatest correlations with the sclerotic areas in the radiographs of the ground sections. Areas of dentin indicative of sclerosis prior to decalcification stained orange-red with the Pollak trichrome stain and deep orange with the Pollak trichrome solution No. 6 modification.

Dentin↗

PubMed1984

Dental involvement in congenital chloride diarrhea.

Dental involvement in a case of congenital chloride diarrhea (CCD) was studied using light microscopy of decalcified and undecalcified sections, microradiography and TEM. Mixed enamel lesions were found, involving gross hypoplasia at the cuspal level and hypocalcification occurring all over enamel. The hypocalcification resulted in the immature aspect of the prismatic enamel, porosities, amorphous areas, prominent incremental lines and round-ended crystallites. A marked hypocalcification suggests a temporary break of amelogenesis likely related to acute episodes of the disease. Globular calcifications were associated with enamel formation. Dentinal hypocalcification was conspicuous and diffuse all over dentine. A globular mineralization pattern was revealed by the tretracycline (TC) stain which was well preserved in decalcified sections, thus indicating that TC uptake is related to the organic matrix. It is unlikely that TC alone is responsible for the hypocalcified areas which extended widely beyond the TC-stained bands. It is suggested that TC uptake only adds to dental defects induced by the metabolic troubles of CCD.

Alkalosis↗

PubMed1994

Experimental odontomas in osteopetrotic op/op rats.

Osteopetrosis is an autosomal recessive disease in several mammalian species. Osteopetrotic op/op rats suffer from complete failure of tooth eruption related to reduced bone resorption. In our earlier studies, op/op rats grafted with bone marrow cells 3 days after birth were cured of the disease and their molar eruption was restored. However, the incisors failed to erupt and their proliferating ends were distorted, forming odontomas. The purpose of the present investigation was to study the odontogenic tissues in the odontomas, using the correlated techniques of radiography and microradiography of undecalcified material, together with histology of decalcified material and scanning electron microscopy.

Animals↗

PubMed1980

Bone tissue formation within a sintered microporous glass-fiber network implanted in extraction sockets in the rat.

Implants were prepared by sintering glass-fibers into a three-dimensional network with meshes smaller than 20 micron. Oblong 5 x 2 x 0.15 mm sheets of the test material were implanted in maxillary incisor alveoli in eight white rats. The alveoli were closed with a suture in the overlying mucosa. After 3 months the animals were sacrificed and sections from the site of implantation prepared. In three animals only root remnants were found but in the remaining five the implants were wholly or partially embedded in bone tissue. Sections studied with transmitted light, microradiography, and scanning electron microscopy showed that mineralized tissue had also formed within the pores of the network. The intimate contact between the individual fibers and the bone within the network was corroborated through microchemical analysis (EDX).

Alveolar Process↗