Biomedical subjects

T Albrektsson

Publications and source records attributed to T Albrektsson.

At least 73 records · Page 4Linked to original sources

PubMed1992

A histomorphometric study of unthreaded hydroxyapatite-coated and titanium-coated implants in rabbit bone.

Hydroxyapatite-coated and titanium-coated IMZ dental implants were investigated in an animal study. The implants were placed in the distal femurs of rabbits. Six months after placement, histomorphometric evaluation of the bone-to-implant contact was conducted. The hydroxyapatite-coated specimens demonstrated significantly more direct bone contact compared to the titanium-coated controls.

Alveolar Process↗

PubMed1991

State of the art in oral implants.

Uncontrolled oral implant devices are still being widely used. The documentation of most oral implant systems is poorly backed up or not followed up for an adequate time period. Success rates are being quoted without reference to any defined success criteria. Frequently used oral implant designs such as the Core-Vent, IMZ and Calcitek hydroxyapatite coated implants are in neither case supported by any adequate clinical reports from minimally 5-years of follow-up. Other implant systems such as the ITI, some subperiosteal designs and the Tübingen implant demonstrate well-controlled and acceptable 5-year data but are not followed up in a sufficient number or have demonstrated less good results in the 10-year evaluation. The Small transosteal staple has been adequately reported for more than 10 years of follow-up, whereas the Brånemark implant is the only endosseous design that has demonstrated acceptable 15-year success rates.

Dental Implantation, Endosseous↗

PubMed1991

Guided tissue regeneration for implants placed into extraction sockets: a study in dogs.

Twelve 10 mm implants were placed into immediate extraction sockets in dogs. Six implants were isolated with PTFE membranes and 6 sites served as controls. Standardized clinical measurements were taken at test and control sites. At 18 weeks the dogs were anesthetized and flaps were laid for the purpose of obtaining clinical measurements. The average gain of bone around augmented implants was 2.6 mm, while control sites had an average bone gain of 1.0 mm. Ridge width adjacent to augmented sites increased by 1.2 mm and control sites had an increased width of 0.6 mm. Histologic evaluation of test and control specimens showed greater bone formation around augmented implants. Implants augmented with PTFE membranes had clinically significant amounts of bone regeneration when compared with controls.

Alveolar Process↗

PubMed1991

Removal torque for bone-cement and titanium screws implanted in rabbits.

Screw-shaped implants of commercially pure titanium and polymerized methyl methacrylate were inserted into the rabbit tibia. The animals were divided into two groups, and the implants were unscrewed after 5 weeks and 9 months, respectively. After both intervals, removal torque was greatest for the titanium implants. This difference was probably due to lower biocompatibility for the plastic material.

Animals↗

PubMed1991

Histomorphometric studies of hydroxylapatite-coated and uncoated CP titanium threaded implants in bone.

Threaded hydroxylapatite-coated implants of commercially pure (CP) titanium were inserted in the rabbit tibial metaphysis. Uncoated CP titanium screw implants inserted in the contralateral leg served as controls. After 6 weeks and 1 year postinsertion, the semiloaded implants were histomorphometrically analyzed. While not significant, there was more direct bony contact with the hydroxylapatite-coated implants after 6 weeks of follow-up. One year after insertion, there was significantly more direct bone-to-implant contact with the uncoated CP titanium controls.

Animals↗

PubMed1991

A removal torque and histomorphometric study of bone tissue reactions to commercially pure titanium and Vitallium implants.

Screw-shaped commercially pure (CP) titanium and Vitallium implants were inserted in the rabbit tibial metaphysis. After a healing period of 3 months, it was demonstrated that a higher torque was needed to remove the CP titanium implants (average 24.9 Ncm) compared to Vitallium implants (average 11.7 Ncm). The histomorphometric part of the study revealed more bone-to-metal contact for the CP titanium implants (average 34.7%) compared to the Vitallium implants (average 21.7%). The results obtained in this study could be explained by differences in the topography or in biocompatibility of the metals, or a combination of these two factors.

Animals↗

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↗

PubMed1990

Bone formation in porous implants of delrin and commercially pure titanium.

Clinicians have been using implants made by titanium or delrin with varying results. In this study dividable implants, bone growth chambers (BGC), of titanium and delrin were inserted into the rabbit tibia. The ingrowth of hard tissue into a canal in the implant was evaluated after 3 weeks by microradiography and numerically determined by computer analysis. Results showed that bone ingrowth into titanium implants was significantly larger than into delrin implants (P less than 0.005). The possible reasons for this are discussed.

Animals↗

PubMed1990

Qualitative interfacial study between bone and tantalum, niobium or commercially pure titanium.

Tantalum (Ta), niobium (Nb) and commercially pure titanium (c.p. Ti) were sputtered on to the surfaces of polycarbonate plastic implants. After 3 month of insertion, in the tibial metaphysis of rabbits, the implants were removed with a surrounding bone collar and processed for light (LM) and electron microscopy (EM). By EM a zone of ground substance tens of nanometers wide without collagen filaments was noticed surrounding the Ta implants. Multinucleated macrophages could occasionally be recognized in the interface zone. Foreign body reactions were more striking at the Nb interface while no multinucleated macrophages were observed in the c.p. Ti interface. The ground substance layer had a thickness in the range of 40-60 nm for the Nb implants, whereas in c.p. Ti sections the collagen filaments were noticed 20-40 nm from the metal surface. There are more subtle differences between tantalum and c.p. titanium than between c.p. titanium and niobium which seems to be less well tolerated when implanted in bone.

Animals↗

PubMed1990

Histologic comparison of ceramic and titanium implants in cats.

This study compared the reparative processes around cylindrical glass-ceramic-coated and pure titanium implants placed in feline femurs. Six weeks after implant placement, bone specimens with inserted implants were prepared for histologic examination including histomorphometric quantification of the relative implant surface areas that were in contact with bone. The glass-ceramic implants were surrounded by a 0.2- to 0.5-mm envelope of fibrous connective tissue [corrected]. By contrast, the major part of the titanium implants (81% +/- 5%) was in direct contact with living lamellar or woven bone. Thus, titanium and glass ceramic evoked different reparative processes when implanted in bone, and only the titanium implants appeared to become osseointegrated.

Animals↗

PubMed1990

[Direct bone anchorage of oral implants: clinical and experimental considerations of the concept of osseointegration].

The term osseointegration is analyzed in relation to its theoretical and clinical definitions, and comparisons are made to other implant modalities. The term osseointegration has a clear clinical meaning, but there is doubt about its precise usage in an experimental setting. Clinically, an implant can be described as osseointegrated if there is no discernable movement when force is applied to the fixture. This is in contrast to implants surrounded by fibrous connective tissue, which move within soft tissue. Newly developed laboratory techniques may be used in the future to precisely characterize osseointegration in the laboratory.

Dental Implantation↗

PubMed1989

Activation and migration of leukocytes and vascular leakage induced by serum-opsonized zymosan particles in hamster cheek pouch.

The effect of topically applied serum-opsonized zymosan (SOZ) and zymosan-activated serum (ZAS) was studied in the hamster cheek pouch. Our data suggest that early vascular leakage, evaluated by intravital fluorescence microscopy after injection of FITC-dextran, and accumulation of polymorphonuclear granulocytes (PMNGs), quantitated in fixed whole tissue specimens, induced by ZAS and SOZ were caused by complement activation, whereas the late leakages (greater than 20 min after SOZ application) was PMNG-dependent. Inhibition of prostaglandin and leukotriene synthesis by indomethacin, nordihydroguaiaretic acid (NDGA), and BW755C influence early and late vascular leakage as well as accumulation of PMNGs. These drugs also inhibited the activation of hamster PMNGs in vitro, as evaluated by chemiluminescence, in a dose-dependent manner. (-)-Terbutaline, an adrenergic beta agonist, decreased vascular leakage but had no effect on PMNG activation and accumulation.

Animals↗

PubMed1989

Morphometrical studies of human femoral condyles.

Thirty-six cadaver knees were examined by various morphometrical methods in order to obtain mathematical and graphical data concerning the geometry of the lower end of the femora. It was found that the paramedian sagittal curves represented magnifications of a certain curvature pattern specific to the medial and the lateral femoral condyle. These curves could be expressed mathematically for each condyle. Furthermore, we found dimensional as well as geometrical intervariations between the different size groups in the knee sample. This could serve as an argument for preferring a different design for medial and lateral condyle components in knee prostheses.

Femur↗

PubMed1989

Ultrastructural differences of the interface zone between bone and Ti 6Al 4V or commercially pure titanium.

Commercially pure (CP) titanium and Ti 6Al 4V alloy were sputtered onto polycarbonate plastic implants to analyse hard tissue reactions to the two metals. The implants were inserted in the tibial metaphyses of five rabbits. Three months later they were removed and processed for light microscopy (LM) and transmission electron microscopy (TEM) investigations. At the LM level, disordered woven bone was seen in the interface zone of Ti 6Al 4V, whereas organized bone was observed in direct contact with the CP titanium implants. TEM examination of Ti 6Al 4V sections revealed a 500-1000 A thick collagen-free proteoglycan layer compared to 200-400 A for CP titanium. A surface analysis test was performed to compare the magnetron sputtered film with bulk Ti 6Al 4V alloy. This test revealed no major differences between the experimental implant and the bulk alloy. More natural-like tissue reactions were observed to CP titanium than to Ti 6Al 4V alloy.

Alloys↗

PubMed1989

Wear of ion-implanted pure titanium against UHMWPE.

Six specimens were manufactured from commercially pure titanium (grade IV) to resemble femoral head prostheses, and five of them ion implanted to increase the wear properties. Together with three cobalt-chrome controls they were run for one million cycles on a 10-station joint simulator. For the first time both the polymer and metallic wear were quantified in the same study. The purpose of the investigation was to estimate the potential for using commercially pure titanium as a bearing surface against ultrahigh-molecular-weight polyethylene for total joint application. It was concluded that the wear properties of titanium were improved by ion implantation, and that these positive effects could probably be enhanced with development of a better polishing technique, and by finding methods of extending the penetration depth of the nitrogen ions.

Biocompatible Materials↗

PubMed1989

Chronic skull-anchored percutaneous implants in non-human primates.

Three groups of chronic, skull-anchored, percutaneous implants differing in materials, design and surgical procedures used for implantation, were tested in macaque monkeys in conjunction with studies of an inner ear stimulation device. Implants from the first two groups in which high-speed drilling methods and stainless steel materials were used, showed a high percentage of failures during the first 3 months after implantation of the percutaneous connector. Implants in the third group, in which measures were taken to preserve living bone tissue, all survived for greater than 7 months. Probable factors relating to implant survival are care of the bone during surgery, postsurgical mechanical trauma, materials and other details of the surgical procedure.

Animals↗

PubMed1989

Patients' attitudes to the bone-anchored hearing aid. Results of a questionnaire study.

A questionnaire constructed to evaluate subjective patient opinions about a new bone-anchored hearing aid was sent to the first 65 patients who underwent this treatment. All 62 patients who were reached responded to the questions formulated according to the critical incident approach. 74% of the patients stated that they were very pleased with what they regarded as an improved sound transmission. 32% of the patients had noticed a qualitative improvement and the same percentage spontaneously commented on their improved cosmetic appearance with the new hearing aid.

Adolescent↗

PubMed1989

Osseointegrated knee prostheses. An experimental study in rabbits.

Osseointegration, defined as direct bone-to-implant contact, has been suggested as an approach for improving the results of arthroplasties of the major joints. An experimental investigation in femoral-patellar joint of the rabbit was performed to evaluate whether osseointegration could be achieved in a one-stage surgical procedure. After three months, it was found that the screws used for anchorage of the prosthesis showed an average direct bone-to-implant contact of 60% in three selected consecutive threads on each side. The range was 40-90%. These figures correspond well with previously reported ones from bone anchored titanium fixtures. It was therefore concluded that osseointegration of dynamically loaded screws used for anchorage of a femoral-patellar joint prosthesis may be achieved in spite of the fact that no controlled healing period for the screws was observed.

Animals↗