Biomedical subjects

E Schepers

Publications and source records attributed to E Schepers.

At least 19 recordsLinked to original sources

PubMed2006

What is uremia? Retention versus oxidation.

The uremic syndrome is characterized by the retention of a host of compounds which in healthy subjects are secreted into the urine by the healthy kidneys. These compounds disturb many physiologic functions, resulting in toxicity. However, many of the retained compounds as well as many of the pathophysiologic actions of the known retention solutes remain unknown. In this publication, we review recent information on uremic toxicity. Especially the difficulty to remove compounds, such as protein-bound compounds and larger molecules, seems to play a crucial role. New strategies enhancing their removal might be highly useful. Part of the retained compounds are the result of oxidative processes due to the inflammatory status of uremic patients; however, other compounds are not, and even the concentration of oxidative compounds will be further increased by disturbances of urinary clearance.

Hemodialysis Solutions↗

PubMed2005

Microanatomical and histological assessment of the content of superior genial spinal foramen and its bony canal.

OBJECTIVES: To assess histologically the true content of the superior genial spinal foramen and to match these findings to the microanatomical canal content observed using high-resolution magnetic resonance images of the same region. METHODS: Ten human mandibular specimens were imaged using a 9.4 Tesla MRI unit. Afterwards, eight specimens were decalcified, embedded in paraffin and serially sectioned (7 microm) for histological examination; the remaining two were embedded in methylmethacrylate and sectioned (50-60 microm). All sections were examined using routine light microscopy to inspect the superior genial spinal foramen region and its content. RESULTS: Histological observations of the superior genial spinal foramen confirmed the presence of a well-defined neurovascular bundle, with branches of the lingual nerve and lingual artery. The canal had an average diameter exceeding 1 mm and could thus be considered significant. CONCLUSIONS: The present study confirms the existence of a true superior genial spinal foramen's bony canal with neural and blood vessel content. These findings imply that surgical procedures should consider a proper preoperative assessment of the neurovascular trajectory of the superior genial spinal foramen.

Arteries↗

PubMed2004

Conserved regions in the sequence of the F4 (K88) fimbrial adhesin FaeG suggest a donor strand mechanism in F4 assembly.

Oral immunization of newly weaned piglets with recombinant F4 (K88) fimbrial adhesin FaeG induces a F4-specific immune response, significantly reducing F4+ Escherichia coli excretion following challenge. In order to use FaeG subunits in an oral vaccine against F4+ enterotoxigenic E. coli, it is necessary to determine the conservation of the adhesin subunit. Hereto, the faeG sequence was determined of 21 F4ac+ E. coli field isolates from piglets with diarrhoea and subsequently compared with these of the reference strain GIS26 and previously reported FaeG sequences from F4ab, F4ac and F4ad antigenic variant strains. The FaeG amino acid sequence was 96-100% homologous within each F4 serotype, but only 92 and 88% when the F4ab and F4ad antigenic variants were compared with the F4ac antigenic variant. Furthermore, the conserved regions of the adhesin suggest a donor strand mechanism in F4 fimbriae assembly as reported for type 1 and P pili. In conclusion, the results of the reported experiments support the usefulness FaeG in an oral subunit vaccine against F4+ E. coli infections or as a mucosal carrier since the adhesin is conserved among F4+ E. coli field isolates.

Adhesins, Escherichia coli↗

PubMed2003

Cephalometric evaluation of maxillary advancement with an internal distractor in an adult boxer dog.

OBJECTIVE: The aim of the study was to evaluate cephalometrically the effects of distraction of the maxilla over a 1-year period by means of an internal distractor applied in a boxer dog. DESIGN: Internal distractors were placed bilaterally in the internal cavity of the maxillary sinus of a 2-year-old boxer dog after a Le Fort I osteotomy. Distraction was started 5 days after surgery and activations were continued for 14 days at a rate of 1 mm/day. Standardized lateral cephalograms were taken with an extemal source of 90 kV, 60 mS immediately pre-surgery, at day 1 after the start of the distraction (dp) and at day 5 dp, day 7 dp, day 10 dp, day 14 dp (end of distraction), at 14 days of consolidation period (cp), at 28 days cp and at 56 days cp (removal of the distractors). One year after the removal of the distractor, a final lateral cephalogram was taken. Cephalometric analysis was performed and superimpositions were used for the evaluation of the sagittal position of the maxilla. RESULTS: The linear measurements, as well as the superimposition showed evidence for a significantly advanced position of the maxilla, which was stable 1 year after removal of the distractor. CONCLUSION: The application of the internal maxillary distractor in a boxer dog resulted in a sagittal advancement of the midface that was still present after 1 year.

Animals↗

PubMed2003

Maxillary distraction using a trans-sinusal distractor: technical note.

In this pilot study, the principle of distraction osteogenesis was used to advance the midface of a boxer dog. A modified high Le Fort I-type osteotomy was performed. Following a latency period of 5 days the maxilla was distracted 14 mm in 14 consecutive days at a rate of 1 mm per day. Ten weeks after the completion of the distraction, multiple biopsies were taken across the distraction gap. Histological observation showed bone deposition in the osteotomy sites. Soft and hard tissue formation resulted in complete healing across the distraction gap. The maxillary sinus was used to accommodate the distraction device. Superimposition of the standardized lateral cephalograms taken at the end of distraction and 14 months after the removal of the distractors showed no sign of relapse in the achieved sagittal advancement of the maxilla. This small, intraoral trans-sinusal placed distractor has a completely new conceptual design, and may be helpful in distraction of maxilla in children and adults with midfacial hypoplasia.

Animals↗

PubMed2002

A newly designed vertebral replacement implant to reconstruct the thoracolumbar spine anteriorly.

Calcium phosphate compounds are becoming of increasingly great importance in the field of biomaterials and, in particular, as bone substitutes. In this way donor-side morbidity can be avoided. A type A lesion of the vertebral body can be the reason of a neurological deficit, requiring a corpectomy by means of an anterior approach, tricortical bone grafting and internal stabilization to get a fusion over time. It is our aim to introduce in this study a newly designed vertebral replacement device, tested in an animal model, using domestic pigs. Two biomaterials, Cementek and Biobon were primarily macroscopically and microscopically evaluated, using a critically sized bone defect of a vertebral body and compared with autologous bone grafts. The final tests consisted of two groups of four animals. A corpectomy at the level of L4 was created and stabilized by means of the newly designed vertebral replacement implant. Autologous bone grafts were applied in one group of animals and Cementek in the other to fill the remaining space. Fusion was studied using anteroposterior and lateral radiographs, followed by a computer tomography. The biocompatibility of the biomaterials and autologous bone grafts were in order of: Cementek > autologous bone grafts > Biobon. In the final tests after a six months period, a fusion was diagnosed in four cases, two delayed unions, and two obvious non-unions. An analysis of the failures in this animal study can possibly clarify the shortcomings of this concept. Perhaps, subtle changes of the design combined with other synthetic bone substitutes can possibly improve the fusion rate in the near future.

Animals↗

PubMed2001

Maxillary sinus floor augmentation using bioactive glass granules and autogenous bone with simultaneous implant placement. Clinical and histological findings.

This clinical study was undertaken to: 1) evaluate the use of bioactive glass Biogran combined with autogenous bone as grafting material for maxillary sinus augmentation with simultaneous implant placement using radiography and histology; and 2) document the short-term post-loading success of implants inserted in sinus cavities augmented with this material. Unilateral or bilateral sinus augmentation was performed in 12 patients with 3-5 mm of alveolar crestal bone height in the posterior maxilla prior to grafting. The sinuses were grafted with bioactive glass mixed in a 4:1 ratio with autogenous bone. Simultaneously, 2-3 threaded titanium implants were inserted into the augmented sinuses. Second stage surgery was carried out 9 to 12 months post implantation. At abutment connection, 10 core biopsy specimens were taken from different grafted sites and evaluated histologically. All 27 implants were clinically stable at second stage surgery. A mean increase in mineralized tissue height of 7.1 +/- 1.6 mm was evident when comparing the pre-surgical CT scans with those performed 9-12 months following the sinus augmentation procedure. Evaluation of the cores yielded a mean of 30.6 +/- 5.7% of bone tissue in the grafted sites. One implant failed during the prosthetic phase while the remaining 26 implants were stable 12 months post loading. This study suggests that Biogran/autogenous bone graft combination used in one-stage sinus augmentation yields sufficient quality and volume of mineralized tissue for predictable simultaneous implant placement in patients with 3-5 mm of bone height prior to grafting.

Adult↗

PubMed2000

Bone healing in porous implants: a histological and histometrical comparative study on sheep.

Tissue integration in four types of porous implant materials (Interpore 200 or Corallin hydroxyapatite, hydroxyapatite blocks, hydroxyapatite granules and polymethylmethacrylate) was evaluated in vivo. Porous blocks measuring 20 mm x 10 mm x 8 mm were implanted in mandibles and iliac crests of sheep. Bone healing in porous blocks was studied at 2 and 6 months after implantation. The behavior of the material itself was also analyzed. Histological and histomorphometrical analysis revealed bone healing depending upon healing time and material. On the basis of analysis of variance, differences in amounts of bone ingrowth at 2 and 6 months were statistically significant (p=0.0039 in mandible; p=0.0351 in iliac crest). The longer the time span, the more mineralized tissues were observed in the specimen. Our data confirmed that hydroxyapatite has osteoconductive capacities. Porous PMMA was found to be biocompatible, but it showed less bonegrowth within the pores. Interpore 200, which had the highest surface to volume ratio was found to display the highest level of osseointegration and biodegradation.

Journal Article↗

PubMed1998

Bioactive glass fiber/polymeric composites bond to bone tissue.

Bioactive glass fibers were investigated for use as a fixation vehicle between a low modulus, polymeric composite and bone tissue. In an initial pilot study, bioactive glass fiber/polysulfone composites and all-polysulfone control rods were implanted into the rabbit tibia; the study was subsequently expanded with implantation into the rabbit femur. Bone tissue exhibited direct contact with the glass fibers and adjacent polymer matrix and displayed a mechanical bond between the composite and bone tissue after six weeks implantation. Interfacial bond strengths after six weeks implantation averaged 12.4 MPa, significantly higher than those of the all-polymer controls. Failure sites for the composite at six weeks generally occurred in the bone tissue or composite, whereas the failure site for the polymer implants occurred exclusively at the implant/tissue interface. The bioactive glass fiber/polysulfone composite achieved fixation to bone tissue through a triple mechanism: a bond to the bioactive glass fiber, mechanical interlocking between the tissue and glass fibers, and close apposition and possible chemical bond between the portions of the polymer and bone tissue. This last mechanism resulted from an overspill of bioactivity reactions from the fibers onto the surface of the surrounding polymer which we call the "halo" effect.

Animals↗

PubMed1998

Finite element analysis of non-axial versus axial loading of oral implants in the mandible of the dog.

The influence of axial and non-axial occlusal loads on the bone remodelling phenomena around oral implants in an animal experiment is simulated in a finite element analysis. The axial and non-axial loading conditions were introduced by inserting a bilaterally supported fixed partial prosthesis and a cantilever fixed partial prosthesis on two IMZ implants in the mandible of beagle dogs. Earlier quantitative and qualitative histological analyses revealed a statistically significant different remodelling response between both loading conditions. Two-dimensional and three-dimensional models are built to analyse and compare von Mises equivalent stress, maximum principal stress, maximum principal strain and strain energy density distributions, first around a free-standing implant and subsequently around the implants of the two prosthesis designs under the respective resultant in vivo loads. Strong correlations between the calculated stress distributions in the surrounding bone tissue and the remodelling phenomena in the comparative animal model are observed. It is concluded that the highest bone remodelling events coincide with the regions of highest equivalent stress and that the major remodelling differences between axial and non-axial loading are largely determined by the horizontal stress component of the engendered stresses.

Alveolar Process↗

PubMed1996

The influence of abutment surface roughness on plaque accumulation and peri-implant mucositis.

Bacterial adhesion to intra-oral, hard surfaces is firmly influenced by the surface roughness to these structures. Previous studies showed a remarkable higher subgingival bacterial load on rough surfaces when compared to smooth sites. More recently, the additional effect of a further smoothening of intra-oral hard surfaces on clinical and microbiological parameters was examined in a short-term experiment. The results indicated that a reduction in surface roughness below R(a) = 0.2 microns, the so-called "thresholds R(a)", had no further effect on the quantitative/qualitative microbiological adhesion or colonisation, neither supra- nor subgingivally. This study aims to examine the long-term effects of smoothening intra-oral hard transgingival surfaces. In 6 patients expecting an overdenture in the lower jaw, supported by endosseus titanium implants, 2 different abutments (transmucosal part of the implant): a standard machined titanium (R(a) = 0.2 microns) and one highly polished and made of a ceramic material (R(a) = 0.06 microns) were randomly installed. After 3 months of intra-oral exposure, supra- and subgingival plaque samples from both abutments were compared with each other by means of differential phase-contrast microscopy (DPCM). Clinical periodontal parameters (probing depth, gingival recession, bleeding upon probing and Periotest-value) were recorded around each abutment. After 12 months, the supra- and subgingival samples were additionally cultured in aerobic, CO2-enriched and anaerobic conditions. The same clinical parameters as at the 3-month interval were recorded after 12 months. At 3 months, spirochetes and motile organisms were only detected subgingivally around the titanium abutments. After 12 months, however, both abutment-types harboured equal proportions of spirochetes and motile organisms, both supra- and subgingivally. The microbial culturing (month 12) failed to detect large inter-abutment differences. The differences in number of colony- forming units (aerobic and anaerobic) were within one division of a logarithmic scale. The aerobic culture data showed a higher proportion of Gram-negative organisms in the subgingival flora of the rougher abutments. From the group of potentially "pathogenic" bacteria, only Prevotella intermedia and Fusobacterium nucleatum were detected for anaerobic culturing and again the inter-abutment differences were negligible. Clinically, the smoothest abutment showed a slightly higher increase in probing depth between months 3 and 12, and more bleeding on probing. The present results confirm the findings of our previous short-term study, indicating that a further reduction of the surface roughness, below a certain "threshold R(a)" (0.2 microns), has no major impact on the supra- and subgingival microbial composition.

Adult↗

PubMed1991

Bioactive glass particulate material as a filler for bone lesions.

Calcium-phosphate ceramic particulates are often used as filler material for enhanced repair of dental bone defects. Although evidence of bone ingrowth in the scaffold of these particles has been described, it is not observed consistently. Fibrous tissue often encapsulates these particles, which can subsequently become dispersed into the surrounding tissues or even exfoliated. The aim of the present study was to evaluate bioactive glass granules (Biogran) as a filler for osseous lesions, and to compare them with two commercially available Hydroxylapatite (HA) granules. The particulates were implanted in the jaws of five beagle dogs, resected and evaluated after 1, 2, 3, 6 and 12 months of implantation. Histological analysis revealed an improvement in repair of all the lesions. A massive osteoconductive bone growth was seen near the walls of the bony cavities, but in greater amounts around the bioactive glass granules than around the HA materials. On top of this massive growth a trabecular bone growth was observed in the centre of the bony cavities. These trabeculae were associated with the glass particles, which exhibited osteophilic properties, while fibrous tissue separated the bone tissue from the HA particles. The centres of many of the particles are excavated, and are subsequently filled by newly formed bone tissue. This internally formed bone tissue is not necessarily connected to the surrounding bone tissue, and functions as a nucleation site for further bone repair. For the mesenchymal cells within the eroded glass particles this inner environment acts as a stimulus to differentiate into osteoblasts and to start their osteogenetic potential. This phenomenon was not observed around the HA materials. If the latter were surrounded by fibrous tissue, disintegration of the surface by giant cells was observed.

Adhesiveness↗

PubMed1989

Interfacial analysis of fiber-reinforced bioactive glass dental root implants.

Bioactive glass can form an effective bond with bone. Essential for this connection are the interfacial reactions which lead to the development of a Si-rich film covered by a CaP-rich film. The presence of these layers can be demonstrated clearly by EDX analysis of fiber-reinforced bioactive glass and bulk bioactive glass implants installed for 4 and 16 months in the partial edentulous jaws of beagle dogs. EDX analysis reveals three types of microchemical interface. The first type develops when the implant is bonded to bone. Here, a smooth transition of the CaP profile can be observed between bioactive glass and the bone, thus providing for a compositional gradient between the implant and the surrounding tissues. The second type is seen when the implant surface is surrounded by fibrous tissue. This causes a discontinuity in the CaP profile. The third type is characterized by a gradual decrease in the Ca and P concentrations across the interface, caused by the presence of Ca and P in the fibrous tissue near the implant surface. This suggests that the interface is dynamic in time and transforms to a functionally better optimized interface. EDX analysis does not reveal any metal fiber ion contamination of the outer glass rim of the implant. When stainless-steel or wrought Co-Cr alloy is exposed to the surrounding fluids, the interfacial osteogenesis is disturbed, possibly by a synergistic effect of glass ions and metal ions. Exposure of titanium does not interfere with this osteogenesis. The bone bonding can also be influenced by surgical trauma. However, with precise implantation techniques, an enhancement of bone growth by osteoconductivity can be measured.

Animals↗

PubMed1988

Histological and histomorphometrical analysis of bioactive glass and fibre reinforced bioactive glass dental root implants.

Bioactive glass has the ability to bond with bone, but it cannot be used as a load bearing device due to its limited mechanical properties. By reinforcing bioactive glass with a ductile second phase, a structurally reliable material is obtained. The aim of the present study was to evaluate histologically and morphometrically the interfacial behaviour of submerged composite dental root implants. Therefore, bulk and composite implants were subgingivally installed in the partially edentulous jaws of Beagle dogs and harvested after 4 and 16 months. Histologically, the connection between the implants and bone tissue could be clearly demonstrated. This bone connection is mainly located at the cortical bone level. In the vicinity of the infraalveolar nerve a fibrous tissue contact was found. It is shown that surgical trauma, motion at the glass to tissue interface, and gross ion dissolution from the material adversely affect the interfacial osteogenesis. If these factors are controlled, bone bonding is found over a larger area than the initial area of contact between the implant and bone tissue. This means that bone grows out along the implant surface, starting from the initial contact area. No difference was observed between the interfacial behaviour of bulk bioactive glass and intact fibre reinforced bioactive glass implants.

Animals↗

PubMed1988