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Biomedical subjects

A Wennerberg

Publications and source records attributed to A Wennerberg.

54 records · Page 3Linked to original sources
PubMed1996

Mixed erythrocyte chimerism: implications for tolerance of the donor immune system to recipient non-ABO system red cell antigens.

We report a case of a minor degree of ABO incompatibility in a BMT recipient, demonstrating mixed RBC chimerism, who, late in the post-transplant period, developed a warm autoimmune hemolytic anemia and subsequently developed antibodies with donor-anti-recipient specificities for non-ABO system RBC antigens. While this implies a lack of tolerance of the donor immune system for recipient non-ABO system RBC antigens, other factors may be operating and should be evaluated before such a conclusion is reached. Underscored is the importance of obtaining pretransplant RBC antigen phenotypes on both the recipient and donor.

Adult↗
PubMed1995

Anchorage of TiO2-blasted, HA-coated, and machined implants: an experimental study with rabbits.

The purpose of this study was to evaluate the histometrical and biomechanical anchorage of TiO2-blasted implants and TiO2-blasted implants coated with hydroxyapatite. The control implants were machined. Twenty-six rabbits had a total of 156 implants placed in the proximal part of the tibia. Each rabbit had a machined, a TiO2-blasted, and a TiO2-blasted, HA-coated implant placed in each tibia. After a healing period of 3 and 12 weeks, respectively, the implants placed in the right tibia were used for removal torque test, and the implants placed in the left tibia were used for histomorphometrical measurements. Preoperatively, implants from the same batches were examined topographically with a TopScan 3D system. The TiO2-blasted implants demonstrated significantly higher removal torque values than the machined implants, and they also had a significantly more irregular surface. Furthermore, significantly higher bone-to-implant contact length fractions were measured adjacent to the TiO2-blasted implants in contrast to the machined implants. The advantages of a TiO2-blasted surface were more pronounced after 3 weeks than after 12 weeks. The results demonstrated that it was possible to influence the anchorage of implants by altering the surface structure morphology. The new method with TiO2 blasting on the titanium surface improves the anchorage of implants but is not yet practicable for HA coating.

Animals↗
PubMed1995

A histomorphometric and removal torque study of screw-shaped titanium implants with three different surface topographies.

Screw-shaped implants with 3 different surface topographies, evidenced visually as well as numerically with an optical profilometer, were inserted in rabbit bone. After a healing period of 12 weeks, a statistically significant higher removal torque was needed to unscrew screws blasted with 25-microns TiO2 particles and screws blasted with 75-microns particles of AI2O3 compared with screws with a turned surface. The histomorphometric evaluation demonstrated a higher percentage of bone-to-metal contact for implants blasted with 25-microns particles of TiO2 compared with the as-machined implants. A greater surface area of bone in threads was found for the turned screws compared with screws blasted with 25-microns TiO2 particles. In the short-term follow-up, there was a better fixation of implants with an average surface roughness of 0.9-1.3-microns and with a homogeneous surface structure than of implants with an average surface roughness of 0.4 microns and with a clear direction of the surface pattern.

Aluminum Oxide↗
PubMed1993

Design and surface characteristics of 13 commercially available oral implant systems.

Thirteen commercially available oral implant systems were investigated with respect to design and surface topography. The implants were divided into four groups, depending on their different surface materials and treatments. Surface topography was measured with a measurement system for noncontact surface profilometry using confocal scanning microscopy. Results indicated that design, as well as surface topography, varied considerably between the different implant systems.

Dental Implants↗
PubMed1992

An optical three-dimensional technique for topographical descriptions of surgical implants.

The purpose of this study was to develop a noncontacting optical method for the topographical description of surfaces. The method is suitable for all types of surgical implants, including threaded ones. The TopScan 3D system employs a scanning spot and a stationary object at a relatively large working distance to enable proper object alignment, and the depth discrimination property of confocal laser scanning microscopy forms the basis of its surface profiling ability. Scanning is achieved by precision movement of the microscope objective along three orthogonal axes (X, Y, Z). Three-dimensional surface topographical maps are produced by performing a series of parallel XZ scans in Y steps. Eighty seven screw-shaped titanium implants were divided into five groups each with a different surface roughness. The five groups were obtained by varying the size of the blasting particles and by leaving one group 'as-machined'. By using the TopScan 3D approach, we were able to calculate different kinds of surface roughness parameters and to produce visual images from the groups. As expected, the surfaces blasted with large particles showed higher values for the surface parameters than those blasted with smaller particles; the latter had higher values than the 'as-machined' screws.

Bone Screws↗
PubMed1991

Glow-discharge pretreated implants combined with temporary bone tissue ischemia.

The aim of present experimental study, was to investigate whether glow-discharge pretreated screws improved the implant take if initial blood flow was prevented in the implant bed. Glow discharge treatment has in previous studies in soft tissue showed to be advantageous for biological adhesion, presumably due to an increase in surface energy. In bone tissue, so far, positive effects of glow discharge have not been reported. One reason for this could be that circulating blood would immediately contaminate the implant surface and lower the high energy state. To prevent circulating blood to reach the implant bed, we used an infant pneumatic cuff placed on the right leg of the rabbit. The pressure was 300 mm Hg during 2.5 hours. The left leg served as control. After 5 minutes when there were no longer a noticeable pulse, 40 glow-discharged pretreated screws were inserted in the tibia. After 7 weeks the animals were sacrificed. There were no significant differences in torque measurements or histomorphometric analysis between control and test implants.

Adhesiveness↗
PubMed1989

Influence of external administration of epinephrine on bone regeneration.

The effect of local administration of epinephrine was tested in a rabbit experimental model. Identical commercially pure titanium implants were inserted in the right legs of New Zealand white rabbits after pretreatment with epinephrine; the left legs served as controls. This acute administration of epinephrine was shown to have no significant impact on the incorporation of the implant as measured after 7 weeks.

Animals↗
PubMedDate not supplied

Oxidized implants and their influence on the bone response.

Surface oxide properties are regarded to be of great importance in establishing successful osseointegration of titanium implants. Despite a large number of theoretical questions on the precise role of oxide properties of titanium implants, current knowledge obtained from in vivo studies is lacking. The present study is designed to address two aspects. The first is to verify whether oxide properties of titanium implants indeed influence the in vivo bone tissue responses. The second, is to investigate what oxide properties underline such bone tissue responses. For these purposes, screw-shaped/turned implants have been prepared by electrochemical oxidation methods, resulting in a wide range of oxide properties in terms of: (i) oxide thickness ranging from 200 to 1000 nm, (ii) the surface morphology of barrier and porous oxide film structures, (iii) micro pore configuration - pore sizes<8 microm by length, about 1.27 microm2 to 2.1 microm2 by area and porosity of about 12.7-24.4%, (iv) the crystal structures of amorphous, anatase and mixtures of anatase and rutile type, (v) the chemical compositions of TiO2 and finally, (vi) surface roughness of 0.96-1.03 microm (Sa). These implant oxide properties were divided into test implant samples of Group II, III, IV and V. Control samples (Group I) were turned commercially pure titanium implants. Quantitative bone tissue responses were evaluated biomechanically by resonance frequency analysis (RFA) and removal torque (RT) test. Quantitative histomorphometric analyses and qualitative enzyme histochemical detection of alkaline (ALP) and acidic phosphatase (ACP) activities were investigated on cut and ground sections after six weeks of implant insertion in rabbit tibia. In essence, from the biomechanical and quantitative histomorphometric measurements we concluded that oxide properties of titanium implants, i.e. the oxide thickness, the microporous structure, and the crystallinity significantly influence the bone tissue response. At this stage, however, it is not clear whether oxide properties influence the bone tissue response separately or synergistically.

Journal Article↗
PubMedDate not supplied

Suggested guidelines for the topographic evaluation of implant surfaces.

The bone anchorage components of commercially available oral implant systems differ in surface roughness by at least sixfold. Correct reporting of the surface roughness of implant systems is important, since one cannot exclude the possibility that surface roughness will influence clinical results. However, many confusing statements are found in the literature when the surface topography of implants is described. Different measuring instruments and techniques strongly influence the outcome of a topographic characterization. Furthermore, a screw-type design introduces problems for most measuring instruments. Without a standard procedure, it is generally impossible to compare values from one study with another. The aim of the present study was to suggest standards for topographic evaluation of oral implants in terms of measuring equipment, filtering process, and selection of parameters. It is suggested that the measuring instrument be able to measure all parts of a threaded implant if the investigation relates to such a design. Preferably, 3-dimensional measurements should be performed. On screw-type implants, tops, valleys, and flanks should be evaluated. At least 3 samples in a batch should be evaluated, filter size must be specified, and at least one of each height, spatial, and hybrid parameter should be presented.

Biocompatible Materials↗
PubMedDate not supplied

Factors affecting the shear bond strength of bonded composite inlays.

PURPOSE: This article analyzes the influence of different pretreatments on the bond strength between inlays and the resin cement of three different composite inlay systems: Z-100, Targis, and Art Glass. MATERIALS AND METHODS: Four separate treatments of the composite-bonding agent interface were investigated: (1) untreated surface, (2) grinding, (3) sandblasting, and (4) sandblasting followed by silane treatment. Surface topography, roughness, and shear bond strength were evaluated using digital scanning electron microscopy, confocal laser scanning profilometry, and a Lloyd LRX equipped for shear bond testing, respectively. RESULTS: The bond strength is presented both with respect to composite surface pretreatment and with respect to different composite inlay systems. Independent of the composite inlay system, the sandblasted and silane-treated surface was found to give the highest bond strength values, followed by the sandblasted and ground surfaces. The untreated surface showed the lowest bond strength. For pretreated surfaces, Targis showed the highest (P < 0.05) bond strength values, followed by Art Glass and Z-100. This distribution, however, was reversed for the untreated interface, where Z-100 showed the highest bonding strength (P < 0.05). CONCLUSION: Surface pretreatment and roughness as well as the inlay material have an impact on the bond strength and the retention of composite inlays.

Adhesiveness↗
PubMedDate not supplied

Bone and soft tissue integration to titanium implants with different surface topography: an experimental study in the dog.

The aim of the present experiment was to study the peri-implant soft and hard tissues formed at titanium implants with 2 different surface configurations and to give a topographic description of the surfaces examined. In 5 beagle dogs, the mandibular premolars were extracted. Three months later, 4 self-tapping standard implants (SI) and 4 Osseotite implants (OI) of the 3i Implant System were placed. The marginal 3 mm of the OI is turned, while the remaining part has an acid-etched surface structure. Abutments were connected after 3 months. A plaque control period was initiated, and after 6 months block biopsies were obtained. From each animal 2 units of each implant type were processed and embedded in EPON. The remaining biopsies were processed for ground sectioning. The histometric measurements performed on the EPON sections revealed that the peri-implant soft tissues and the marginal level of bone-to-implant contact were similar for SI and OI sites. In the ground sections, bone-to-implant contact (BIC%) and bone density assessments were made in 2 different zones. Zone I represented the contact area measured from the marginal level of bone-to-implant contact (B) to a position 4 mm above the apex of the implant, and zone II represented the apical 4 mm of the implant. For the SI sites, the BIC% was 56.1% in zone II and 58.1% in zones I + II. The corresponding figures for the 01 sites were 76.7% and 72.0%. The BIC% was significantly larger at OI than at SI sites. Bone density values were similar at the SI and OI sites.

Acid Etching, Dental↗
PubMedDate not supplied

Influence of occlusal factors on treatment outcome: a study of 109 consecutive patients with mandibular implant-supported fixed prostheses opposing maxillary complete dentures.

PURPOSE: This study was undertaken to investigate the relationship between occlusal variables and clinical and radiologic findings as well as patient response to treatment outcome in patients with mandibular implant-supported fixed prostheses opposing maxillary complete dentures. MATERIALS AND METHODS: The study group consisted of 109 consecutive patients attending for annual control. They had received their mandibular implant-supported prostheses according to the Brånemark system on average 8 years previously (range 1 to 27 years). All patients were interviewed with standardized questions by one examiner, who also performed the clinical examination. The questions focused on the patients' opinion on masticatory and prosthetic function and problems. The clinical examination comprised occlusal and prosthetic factors and the health of the oral mucosa. RESULTS: The great majority of the patients were very satisfied with their present dental situation and masticatory function. Two thirds reported no problems with their maxillary complete dentures at all. Balanced occlusion was found bilaterally in 61%, and a further 4% had balanced function on one side. More than one third thus lacked balanced occlusion. Only about 60% had optimal occlusion, and 8% had poor occlusion according to common prosthodontic criteria. This was interpreted as a continuing impairment of the occlusion with time. The mean bone loss was 0.5 mm, according to available radiographs, for a mean observation period of 54 months. There were no or only weak correlations between the variables examined. CONCLUSION: The occlusal factors registered were of limited importance for patient satisfaction and treatment outcome recorded clinically and radiographically at follow-up examination of the actual prosthodontic rehabilitation.

Aged↗
PubMedDate not supplied

Bone tissue response to commercially pure titanium implants blasted with fine and coarse particles of aluminum oxide.

The present study compares the bone response to commercially pure titanium screws with two different degrees of surface roughness. Implants blasted with 25- and 250-micron particles of aluminum oxide were placed in rabbit tibiae after the surface roughness of the implants had been measured. After 4 weeks, there was a significantly higher bone-to-metal contact for implants blasted with 25-micron particles compared to those blasted with 250-micron particles. The present study indicates that a highly increased surface roughness compared to a moderately increased one is a short-term disadvantage for bone tissue.

Aluminum Oxide↗
PubMedDate not supplied

A 1-year follow-up of implants of differing surface roughness placed in rabbit bone.

Screw-shaped implants were prepared with three different surface topographies: One was left as machined, ie, a turned surface, and two were blasted surfaces with differing degrees of surface roughness. The surface topography was measured with a confocal laser scanning profilometer and the surface roughness was characterized using height and spatial descriptive parameters. The turned surface had an average surface roughness of 0.96 micron and an average peak spacing of 8.6 microns. The two blasted surfaces had surface roughness values of 1.16 microns and 1.94 microns, respectively; the corresponding values for the peak spacing parameter were 10.00 microns and 13.22 microns, respectively. After 1 year in rabbit bone, the bone response to the turned implants was compared with the response to the two blasted implant surfaces. Firmer bone fixation was found for the two blasted surfaces, with statistically significant increases in removal torque and percentage of bone-to-metal contact. Furthermore, about 2 mm from the implant surface, the titanium release was similar for the turned and the 25-micron aluminum oxide-blasted implants.

Aluminum Oxide↗
PubMedDate not supplied

Microhardness and surface topography of a composite resin cement after water storage.

PURPOSE: The aims of this study were to assess changes in the microhardness and surface roughness of a dual-cured composite resin cement after water storage for different periods of time. MATERIALS AND METHODS: Sixty specimens were divided into four groups comprising high- and low-viscosity cement specimens stored either dry or in water for 1 to 60 days. Microhardness and surface roughness measurements were made after 1, 7, and 60 days of storage. RESULTS: It was found that that although interactions complicated the interpretation of the results, the water-stored samples had a significantly lower microhardness compared to the dry-stored specimens for every time interval. In addition, the high-viscosity specimens had a significantly higher microhardness compared to the low-viscosity specimens. An increased microhardness was found for all groups, except for the low-viscosity, water-stored specimens after 60 days of water storage, which was attributed to an effect of the chemical postcuring process. Although difficult to evaluate from a clinical point of view, the laser profilometry analysis revealed that a significantly increased surface roughness was found after water storage and increased storage time that was possibly caused by a deterioration of the resin-matrix surface. CONCLUSION: For the permanency of the interfacial luting material, a high microhardness value seems to be important.

Analysis of Variance↗
PubMedDate not supplied

A quantitative comparison of machined commercially pure titanium and titanium-aluminum-vanadium implants in rabbit bone.

Screw-shaped implants made from rods of commercially pure titanium (grade 1) and titanium-aluminum-vanadium (grade 5) were machined, and the implant surface structures were numerically described before being placed in rabbit tibiae for healing periods of 1 months, 6 months, and 12 months. Quantitative comparisons of the removal torque (Ncm) necessary to loosen the implants from the bone bed were performed. Short-term (1 month) observations revealed no significant differences between the two tested materials. However, after 6 and 12 months, the commercially pure titanium implants were significantly more stable in the bone bed, as compared to the alloy samples. After 6 months, the commercially pure titanium had a mean removal torque of 29 Ncm versus 23 for the alloy (P = .01), and after 12 months, the mean removal torque was 38 Ncm for commercially pure titanium as compared to 35 Ncm for the alloy (P = .01). Quantifications of the bone tissue response to the materials did not show any significant differences; however, the commercially pure titanium showed a tendency to have a higher percentage of bone in contact with the implant as compared to the alloy screws. Bone volumes in the threads were similar. The absence of any quantitative light microscopic difference after 1 month following placement may relate to the fact that there was a sparse amount of bone, since the tissue was in the organization/granulation phase. After 6 and 12 months of follow-up, substantial bone formation had occurred, resulting in significantly increased removal torques for the commercially pure titanium samples.

Alloys↗