金矿床开采品位合理性的模糊综合评价

本文阐述了模糊综合评判方法的基本原理和分析方法，并考虑影响矿山开采品位的多种因素而作出综合评价。通过实例分析和评价结果表明，该方法是科学的、可行的．在应用中取得了符合矿山的实际结果。     

Use of expanded polytetrafluoroethylene grafts for vascular access in hemodialysis: laboratory and clinical evaluation

Vascular access for chronic hemodialysis has evolved considerably over the past 10 years with development of vascular substitutes. The bovine heterograft is the choice of most dialysis centers when a subcutaneous conduit is needed in lieu of an in situ arteriovenous fistula. Bovine grafts have solved some problems, but further improvement in blood access prostheses is needed. Polytetrafluoroethylene (PTFE) grafts were evaluated in a laboratory and clinical study. In animals, PTFE proved to be satisfactory for fistula construction based on patency, incorporation into tissue, and ease of puncture. Ten patients underwent 11 vascular access procedures using PTFE grafts as a conduit. There were no technical operative complications. One graft was occluded by extravasation during dialysis and flow could not be restored. Otherwise, all grafts are patent 9 to 18 months postoperatively. Grafts of 8.0 mm in diameter have not given desirable flow rates, whereas 6.0 mm grafts have. Prolonged bleeding from puncture has been a problem in some cases. Otherwise, PTFE appears to be a satisfactory conduit for hemodialysis vascular access.     

Load-bearing capacity of corticocancellous bone grafts in the spine

We investigated the relationship between the densities and areas of commonly used autogenous tricortical bone grafts from the iliac crest and the fibula and their mechanical load-bearing abilities. Intact corticocancellous grafts, seven millimeters thick, were obtained during elective spinal arthrodeses from fifty-six patients: from the anterior part of the pelvis in twenty-four patients, the posterior part of the pelvis in twenty-nine patients, and the fibula in three patients. The apparent densities and cross-sectional areas of the cortical and cancellous bone were measured with use of a specific computed-tomographic technique before the specimens were mechanically tested to failure in uniaxial compression. Specimens from the anterior superior iliac spine were able to bear significantly higher axial loads (average, 3230 newtons; range, 430 to 8112 newtons) than were those from the posterior superior iliac spine (average, 1458 newtons; range, 350 to 4639 newtons) (p < 0.001). The cancellous density was the most significant single factor in the prediction of the load to failure of the grafts from the iliac crest (adjusted r2 = 0.58; p < 0.0001). When all of the physical variables (the cancellous and cortical densities and areas) were entered into a multiple-regression model, the combination of the cortical and cancellous densities and the cortical area was a good predictor (adjusted r2 = 0.68; p < 0.001) of the load to failure. The fibular grafts were stronger than those from the other two sites, but they had the least over-all cross-sectional area and cancellous bone.(ABSTRACT TRUNCATED AT 250 WORDS)     

A controlled multicenter study of adjunctive use of tetracycline periodontal fibers in mandibular class II furcations with persistent bleeding

The aim of this randomized single-blind multicenter controlled clinical trial was to clinically evaluate the effectiveness of adjunctive local controlled drug delivery in the control of bleeding on probing in mandibular class II furcations during maintenance care. 127 patients presenting with a class II mandibular furcation with bleeding on probing were included in the study. They had been previously treated for periodontitis and were participating in supportive care programs in periodontal specialty practices. Treatments consisted of scaling and root planing with oral hygiene instructions (control) and scaling and root planing and oral hygiene combined with local controlled drug delivery with tetracycline fibers (test). The following outcomes were evaluated at baseline and 3 and 6 months after therapy at the furcation site: bleeding on controlled force probing (BOP), probing pocket depth (PD) and clinical attachment levels (CAL). Levels of oral hygiene and smoking status were also assessed. Both test and controls resulted in significant improvements of BOP and PD at 3 and 6 months. The test treatment, however, resulted in significantly better improvements: BOP decreased by 52% in the control group and by 70% in the test group at 3 months; at 6 months, however, the difference was no longer significant. The test treatment resulted in a 0.5 mm greater reduction of PD than the control at 3 months, the improvement was highly significant but its duration did not extend until the 6 months evaluation. No differences were observed in terms of changes in CAL. These data indicate that addition of tetracycline fibers to mechanical therapy alone resulted in improved control of periodontal parameters during periodontal maintenance of class II mandibular furcations. Short duration of the effect, however, requires further investigations to optimize conservative treatment of these challenging defects.     

Volumetric changes following barrier regeneration procedures for the surgical management of grade II molar furcation defects in baboons: II. Bone, cementum, epithelium, and connective tissue

Written guidelines based on current research on infant pain assessment and management were developed by an interdisciplinary team in a neonatal intensive care unit of a regional medical center. Charts for infants who had undergone abdominal surgery were reviewed to compare patient outcomes before and after use of this pain management protocol. With the standardization of pain management strategies, the following improvements were noted: decreased length of time to extubation, decreased length of stay, better fluid management, and reduced side effects of narcotics. Additional benefits included improved pain management documentation, decreased cost, and decreased nursing time.     

Impaction of cancellous bone grafts impairs osteoconduction in titanium chambers

The method of using morselized compacted cancellous allografts for hip arthroplasty revision shows results that seem to differ dramatically from other kinds of allografting. In structural cancellous allografts, bone ingrowth usually is limited to 2 to 3 mm, whereas morselized compacted grafts seem to be remodeled totally in several cases, as judged by radiography. In the current study, impacted cancellous allografts were compared with unimpacted allografts. Seventeen rats had a bone conduction chamber implanted in the tibias bilaterally. On one side the chambers contained an impacted graft (bone volume fraction 65%) and on the contralateral side an unimpacted graft (bone volume fraction 35%). Impaction of the grafts was done preoperatively with a pressure of either 25 or 2500 MPa. Ingrowing bone could enter the cylindrical interior of the chamber only at one end. After 6 weeks the mean distance the ingrown bone had reached into the graft was measured on histologic slides. With both impaction pressures, the bone ingrowth distance was decreased to 30% of the unimpacted controls. It appears that impaction alone does not have a favorable effect on the osteoconductive properties of a bone graft. On the contrary, impaction seems to disfavor osteoconduction. However, in the clinical situation this is not necessarily a disadvantage.     

Comparative in vitro effectiveness of closed root debridement with fine instruments on specific areas of mandibular first molar furcations. I. Root trunk and furcation entrance

The purpose of this study was to compare curets with a small blade to slim ultrasonic inserts on their efficacy in removing artificial deposits from the root trunk and furcation entrance areas of mandibular molars using an in vitro model simulating a clinically closed root debridement approach. The study was conducted on 100 artificial mandibular first molars (50 right side and 50 left side) with anatomical roots. Root trunks, furcation entrances, and furcation areas of each molar were colored by a coat of black model paint. The teeth were fixed in a custom acrylic model and maintained in a firm position by modified acrylic occlusal splints. The root areas were covered with a heavy rubber dam imitating gingival tissue. The model was attached to a mannequin and mounted on a dental chair. Fifty molars (25 right, 25 left) were instrumented with the experimental curets and an equivalent number of molars with the ultrasonic inserts. The instrumentation was carried out by one experienced operator, spending 4 minutes on each molar. The instrumented areas were individually analyzed to determine the percentage of deposits remaining, using a computerized imaging routine system. One-way analysis of variance was conducted to test for differences between both types of instruments. Results revealed that the curets were significantly more efficient (P < 0.01) than the ultrasonic inserts in removing paint from both root trunks and furcation entrances. These findings should be corroborated in a clinical study to determine the potential value of the instruments tested during initial therapy or supportive care of involved mandibular furcations.     

Biomechanical properties of human os calcanei: relationships with bone density and fractal evaluation of bone microarchitecture

The relationship between bone strength and bone mass is well established. The link between trabecular microarchitecture and biomechanical properties has been less extensively explored. To address this question, we have tested the mechanical behaviour of calcaneus bone samples and investigated the correlations between mechanical properties on the one hand, bone density and fractal analysis of microarchitecture on the other hand. Mechanical properties of 43 human os calcanei were determined by uniaxial compression testing of samples from tuber calcanei. Ash density, bulk density and dual energy X-ray absorptiometry of the samples were measured. Fractal analysis of the trabecular bone on calcaneus radiographs was performed by two estimators derived from the fractional Brownian motion model. The mechanical properties of human os calcis were found to correlate with age and density measurements. Fractal parameters derived from the bone texture analysis showed weaker but significant correlations with bone strength. Fractal analysis of texture could account in part for the variations of bone strength, but in this study cannot explain better than density the mechanical properties of trabecular bone. Nevertheless, it provides a non-invasive means of assessing molecular bone microarchitecture.     

Clinical comparison of cellulose and expanded polytetrafluoroethylene membranes in the treatment of class II furcations in mandibular molars with 6-month re-entry

To evaluate the clinical significance of serum levels of hepatocyte growth factor (HGF) in colorectal cancer patients, we measured the venous and portal concentrations of HGF in 60 patients. The tissue concentrations in the tumour and adjacent normal mucosa were also determined. The serum HGF concentration for the peripheral venous blood of the patients was significantly higher than that in normal controls. The content of HGF in cancer tissue was also significantly higher than that in normal mucosa, and it was correlated with the serum HGF concentration for the peripheral venous blood. The serum concentration of HGF reflected pathological features, including tumour size and lymph node or liver metastasis, and it showed an association with various preoperative nutritional parameters and the preoperative haemoglobin level. The serum HGF concentration was also correlated with the serum concentrations of immunosuppressive acidic protein and interleukin-6, indices of the host's immunological condition. Serum HGF seems to be a useful index of the disease status of patients with colorectal carcinoma.     

Transplantation of stromal cells transduced with the human IL3 gene to stimulate hematopoiesis in human fetal bone grafts in non-obese, diabetic-severe combined immunodeficiency mice

The non-obese diabetic-severe combined immunodeficiency (NOD-SCID) mouse is a convenient host for human hematopoietic tissues and cells. Human fetal bone fragments engrafted subcutaneously in NOD-SCID mice sustain human hematopoiesis for several months. MS5 murine bone marrow stromal cells were transfected by electroporation with a plasmid containing the human interleukin-3 gene. As expected, stably transfected hu-IL3-MS5 cells supported human hematopoiesis in vitro more efficiently than MS5 cells. hu-IL3-MS5 cells were then injected intravenously into hu-NOD-SCID mice to test their ability to home to the mouse and/or human bone marrow, and to evaluate the role of hu-IL3 secretion on human hematopoiesis in vivo. hu-IL3 was detected in the mouse serum for up to an observation time of 8 weeks. hu-IL3-MS5 cells engrafted the bone marrow, spleen, liver and lungs of the mice but also the human bone graft. The presence of hu-IL3-MS5 cells in the human bone significantly stimulated local human hematopoiesis. This setting could be used to model the bone marrow homing of intravenously injected stromal cells or stromal cell precursors. The same experimental principle could also be applied in a therapeutic perspective to malignant human bone marrow hematopoiesis.     

The evaluation of the postoperative response in surgery on the lower third molar

BACKGROUND: The impacted third molar is often excised in the absence of clear signs of disease. On this basis and taking also into account the usual surgical hazard, an analysis of the post-surgical behavior of 100 patients that had undergone excision of the impacted third molar, is made. METHODS: All patients were observed and treated by the same surgeon and were divided into two distinct groups based on the position and depth of the tooth in the bone as observed by orthopantomography. In the first group of patients, bone fenestration was carried out by the use of mallet and gouge and the tooth was excised without odontotomy. In contrast, in patients of the second group, odontotomy always preceded tooth excision. Patients of both groups were analyzed for several different parameters including age, sex, the reason for surgery, tooth position according to Pell and Gregory, the length of excision and, finally, swelling and the reduced mouth opening that occur after surgery. RESULTS AND CONCLUSIONS: Data reported indicate non-proportional results between the two groups; there is no apparent relation between post-surgical swelling and mouth opening, the latter being always present and very pronounced.     

Prognostic factors in low grade (WHO grade II) gliomas of the cerebral hemispheres: the role of surgery

OBJECTIVE: To assess the role of surgery on survival of patients with grade II gliomas of the cerebral hemispheres. METHODS: One hundred and thirty one low grade hemispheric gliomas surgically treated (biopsied patients excluded) between 1978 and 1989 were retrospectively reviewed. Thalamic, basal ganglia, callosal, or ventricular location were not considered. All tumours were World Health Organisation (WHO) grade II gliomas: 42 fibrillary and 11 gemistocytic astrocytomas, 49 oligodendrogliomas, and 29 oligoastrocytomas. Patients' ages ranged from 14 to 63 (mean 32.9, median 34) years, Karnofsky performance from 0.50 to 0.90 (mean 80.7, median 80), and postsurgical follow up of the living patients from 24 to 190 (mean 97.02, median 93) months. Postoperative external radiotherapy was performed in 49 cases. RESULTS: The overall survival probability at five years was 97.1%, at eight years 76.1%, and at 10 years 62.7% (median survival time 144 months). The impact on survival of the following variables was analysed: age (< 20, 21-40, and > 40 years), Karnofsky score (80-100, 70 < or = 70), histology, tumour extension (T1 < 3 cm, T2 3-5 cm, T3 > 5 cm maximum diameter), extent of surgical resection (S1 radical, S2 subtotal < 10% residual tumour, S3 partial-10%-50% residual tumour), and radiotherapy (either performed or not). A significant positive association with survival at univariate analysis was found for the age group < 20 years (P = 0.003), for total and subtotal surgical resections (S1 and S2; P < 0.001) and for the non-irradiated patients (P = 0.0049), whereas a shorter survival probability was noticed for gemistocytic astrocytomas (P < 0.001) and for tumour extension > 5 cm (T3; P = 0.0193). Karnofsky performance did not show any significant association with survival. The most relevant factor affecting survival at the multivariate analysis was the extent of surgical resection, which resulted as the only variable retaining a significant value (P = 0.001, risk factor = 2.20). CONCLUSIONS: The data strongly support the role of a surgical removal as extensive as possible in the treatment of these tumours.     

The evaluation of lyophilized polymer matrices for administering recombinant human bone morphogenetic protein-2

Novel unitary devices, prepared by lyophilization of viscous solutions of sodium carboxymethylcellulose (CMC) and methylcellulose (MC), were evaluated as sustained-release delivery systems for recombinant human bone morphogenetic protein-2 (rhBMP-2). In vitro characterization of the unitary devices, which contained rhBMP-2-loaded poly (d,l lactide-co-glycolide) (PLGA) bioerodible particles (BEPs), was conducted over a 2-month period. Determinations included buffer uptake, mass and molecular weight loss and rhBMP-2 release from the unitary devices. CMC devices imbibed approximately 16 times their weight of buffer, while with MC, equilibrium uptake was approximately 6 times the dry weight of the devices. Overall mass loss percentages were approximately 55 and 35%, respectively, for CMC and MC devices. rhBMP-2 release from the devices was essentially a triphasic process: an initial phase during which "free" protein (rhBMP-2 present on the surface and within the pores of the PLGA BEPs) was released, a lag period during which no release was discerned, and then release of "bound" rhBMP-2 (protein adsorbed to the BEPs). The release of bound protein correlated with the mass loss of the polymer which began after 3 weeks. Release from the unitary devices was lower than that from the BEPs alone, due to a retardation effect of the gelled CMC/MC polymers. In rabbits in which full-thickness cranial bone defects were created, the implants were well tolerated and induced significant new bone growth during an 8-week evaluation period. The CMC devices appear to have induced bone earlier (at 2 weeks), but this did not affect eventual 8-week results. CMC devices without rhBMP-2 appeared to provide some bone conduction, in contrast to the blank MC devices.     

Pretransplantation immunoadsorption therapy in patients immunized with human lymphocyte antigen: effect of treatment and three years' clinical follow-up of grafts

Sensitization against human lymphocyte antigen (HLA) occurs frequently in previously transplanted patients that lose a first cadaveric graft. To shorten their time on the waiting list and reduce the incidence of early rejection in such patients, we performed immunoadsorption therapy by a tryptophan column in 10 patients as an attempt to remove circulating antibodies prior to regrafting. Resynthesis of antibodies was suppressed with cyclophosphamide and prednisolone. Following the course of immunoadsorption therapy, the panel reactive antibodies (PRA) decreased by more than 50% from the pretreatment values. In the present study, 8 patients were transplanted with cadaveric renal grafts. At the time of follow-up, graft survival was 63% in these patients (2-36 months post-transplantation, mean 23 months). There was one incidence of acute rejection, one graft was lost within 48 h owing to renal artery thrombosis, and one was lost within 2 weeks as a result of stenosis. The serum creatinine levels were down to near normal during the first 3 weeks in hospital (p < 0.0001) and remained at this level during the period of follow-up. We conclude that immunoadsorption might be a beneficial pretransplantation therapy and an alternative to plasmapheresis in HLA-immunized patients awaiting kidney transplantation.     

Clinical evaluation of myeloma osteoclastic bone lesions: II. Induced hypocalcemia test using salmon calcitonin

Acute effects of salmon calcitonin (SCT) were tested by an SCT induced hypocalcemia test (SCT delta Ca test) in 70 cases of multiple myeloma (MM) (including 52 untreated patients) with bone involvement. Response to SCT in terms of maximum induced hypocalcemia (M delta Ca) was compared to normal controls (NC) and correlated with the main presenting features and clinical status. Acute effects are significantly more marked in MM than in NC (p less than .001). There is a good correlation with the extent of lytic bone lesions (p less than .01), the presence of hypercalcemia (p less than .02) and the myeloma cell mass (p less than .05). After correction for bone involvement response to SCT (M delta Ca) was stronger in IgA lambda MM than in IgG kappa (p less than .01). It is of particular interest that acute effects are significantly more marked in cases of active disease than in non-active disease. We conclude that the SCT delta Ca test might be of practical value in the management of MM.     

A comparative study of osseointegration of titanium implants in autogenous and freeze-dried bone grafts

PURPOSE: This study was undertaken to compare the rate and degree of osseointegration of dental implants when placed into either autogenous corticocancellous chip or freeze-dried corticocancellous chip bone grafts. MATERIALS AND METHODS: The canine ilium was used as the model site. Thirty experimental and 15 control implants were placed in 15 dogs: autogenous versus freeze-dried corticocancellous chip bone grafts around the exposed implant surfaces. In addition to the placement of control implants, the apical portion of the grafted implants acted as their own control. The implants were harvested at 1, 2, and 3 months. The evaluation of the integration process was performed by means of light microscopy, microradiography, and histomorphometry. RESULTS: Using this model, the results indicate that at 1 month there was no statistical difference in the degree of osseointegration in the two bone grafts. At 2 months, there was a statistically greater degree of osseointegration noted in the autogenous corticocancellous chip sites than in the freeze-dried bone grafts. At 3 months, the degree of osseointegration in the two groups was 70% and 33%, respectively. At 3 months, there was virtually 100% integration with trabecular bone at the control implant sites. CONCLUSION: The results indicate that at 2 months postoperatively implants placed in an autogenous bone chip graft osseointegrate to a significantly greater degree than implants placed in a freeze-dried bone chip graft, and this difference remains at 3 months.     

A comparative analysis of subchondral replacement with polymethylmethacrylate or autogenous bone grafts in dogs

A comparative analysis was made of subchondral replacement with polymethylmethacrylate and autogeneic bone grafts in defects in the medial femoral condyles of dogs. The defect produced a 50% reduction in subchondral stiffness. An in vitro preparation helped establish that subchondral stiffness returned to normal after reconstruction with polymethylmethacrylate. The in vivo model demonstrated a reduction in subchondral stiffness in both groups at three weeks, but the bone grafted side returned to normal and the methylmethacrylate side recovered to 79% of the control at 12 weeks. There were no deleterious effects on the articular cartilage in either group when analyzed histologically and biochemically. A marked increase in new bone formation and subchondral porosity was found in the polymethylmethacrylate groups. This study supports the clinical use of subchondral polymethylmethacrylate after the exteriorization and curettage of benign bone tumors such as giant cell tumors.