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Biomedical subjects

T Albrektsson

Publications and source records attributed to T Albrektsson.

At least 55 records · Page 3Linked to original sources
PubMed1996

Experimental study of turned and grit-blasted screw-shaped implants with special emphasis on effects of blasting material and surface topography.

In the rabbit tibia, commercially pure titanium implants blasted with 25-microns Al2O3 and TiO2 particles respectively were inserted and studied with respect to removal torque and histomorphometry. In the rabbit femur, as-machined implants and implants blasted with 75-microns Al2O3 particles were histomorphometrically compared. Before implant insertion, the differently produced surface topographies were characterized numerically and visually. The tibial implants blasted with different materials and the same sized (25 microns) blasting particles demonstrated similar results. Comparing implants blasted with 75-microns Al2O3 particles to as-machined implants, the blasted specimens exhibited a statistically significant higher bone-to-metal contact after 12 weeks in the rabbit bone.

Aluminum Oxide↗
PubMed1996

Supracrestal bone growth around partially inserted titanium implants in dogs. A pilot study.

8 titanium implants (Nobel Biocare, Göteborg, Sweden) were inserted into edentulous lower premolar areas of 4 dogs so that 6 threads of the implant protruded from the bone crest. Newly-developed perforated dome-shaped titanium space maintainers were fixed to the implant with cover screws. Autogenous bone fragments were placed under the space maintainers. On one side of the arch, the space maintainer was covered with a non resorbable cell occluding barrier. The implant/space maintainers were submerged under coronally positioned flaps. Following a 3-month healing period, there was a mean gain of new bone amounting to 2.5 mm for all specimens. A greater height of bone was found for those sites in which an ePTFE membrane was used; 3.1 mm vs. 1.9 mm (p < 0.05). This study demonstrated the potential of coronal bone growth of the alveolar bone in a protected space around crew implants with exposed treads when placed in the dog.

Alveolar Process↗
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↗
PubMed1995

A new method to obtain bone biopsies at implant sites peri-operatively: technique and bone structure.

This study aims at evaluating an objective method for the description of bone structure in the human mandible. Human bone biopsies were harvested at mandibular implant sites prior to insertion of self-tapping Mark II fixtures. Altogether 15 biopsies were taken from 12 patients. Three patients donated 2 biopsies each, one proximally and one distally taken. Ground sections of about 100 microns thickness were prepared prior to microradiography. These sections were ground to a final thickness of about 10 microns followed by histological staining. Histomorphometrical analyses were performed on the microradiographed plates and on the ground sections. On average there was a bone area of about 54% calculated on the microradiographed plates (the 100-microns sections) versus a mean bone area of 62% light microscopically (the 10-microns sections). Bone lengths were calculated on the 10-microns sections in the central part (mid-line) and on each side of the mid-line, revealing a mean of 58% in the former case and a mean of 61% in the latter case. The amount of bone varied between individuals and in different locations of the same jaw. The postoperative healing period following fixture installation is standardized regardless of bone structure. It may in the future be appropriate to more individualize this healing period based on an objective bone quality score.

Adult↗
PubMed1994

Healing of implant dehiscence defects with and without expanded polytetrafluoroethylene membranes: a controlled clinical and histological study.

Bone augmentation around implant fixtures using the technique of guided tissue regeneration has been described in a number of reports. The aim of this study was to evaluate bone fill around dehiscence defects at matched defects randomly allocated to test (expanded polytetrafluoroethylene; Gore-Tex) or control treatments within the same patient. Six edentulous subjects were treated with overdentures supported by 2 fixtures ad modum Bränemark. In addition, 2 experimental 7-mm fixtures with nearly identical dehiscence defects on the labial aspect were placed in the anterior part of the mandible. Baseline defect heights ranged from 2.5 to 4.0 mm with 2 to 4 threads exposed. The test fixture dehiscence was covered with a Gore-Tex membrane secured with a cover screw. The experimental fixtures were exposed after 5 months at stage 2 surgery and measurements and photographs repeated. The fixtures were then removed with a trephine and processed for histological evaluation. Regeneration of a hard tissue resembling bone was observed in 4 of 6 cases treated with Gore-Tex, amounting to between 95 and 100% elimination of the dehiscence and total coverage of the threads. However, in one of these cases, histological evaluation showed that it was soft tissue and not bone, and in a further case soft tissue regeneration was apparent both clinically and histologically. In another case there was no significant regeneration at either test or control defects. Although there was a trend for the Gore-Tex-treated dehiscences to respond more favourably, the differences in clinical and histological measurements between test and control failed to reach statistical significance.

Adult↗
PubMed1993

Influence of indomethacin on the regeneration of cortical bone within titanium implants in rabbits.

The influence of indomethacin on cortical bone regeneration was studied in bone harvest chambers made of commercially pure titanium and inserted in rabbit tibia. Newly formed bone was harvested in situ every 3 wk for 33 wk. Indomethacin (1 mg/kg body weight) was given daily as subcutaneous injections for two periods, followed by two control periods with no drug administration and the same schedule was followed for indomethacin at a dose of 4 mg/kg body weight. These indomethacin dosages did not statistically influence the cortical bone regeneration.

Analysis of Variance↗
PubMed1993

Histologic investigations on 33 retrieved Nobelpharma implants.

Thirty Nobelpharma implants were retrieved from 17 patients despite a remaining clinical stability, after between 1 and 16 years of clinical function. The reasons for implant removal were bone resorption in combination with soft tissue disorders, psychological causes, implant fracture and post mortem cases. When measured at the cortical passage, there was an average of 84.9% direct bone-to-implant contact and 81.8% average surface bone area in individual threads as evaluated in a computerized morphometric system at the light microscopic level.

Adult↗
PubMed1993

A qualitative and quantitative study of retrieved femoral heads in three different types of resurface hip arthroplasties.

Tissue reactions and percentage of mineralized bone in three different types of retrieved femoral head hip resurface prostheses were studied in undecalcified ground sections without removing the metal. All of the prostheses demonstrated soft tissue between the cement-implant and bone. There were some areas without soft tissue between bone and cement. This bone was often not normally stained, indicating a disturbed mineralization. The soft tissue layer in the cemented prostheses was observed in different stages of necrosis, while the uncemented prostheses demonstrated a thick collagen membrane. One of the cemented groups demonstrated a gradual decrease of mineralized bone towards the cement. The uncemented implants revealed normal bone qualitatively and quantitatively when the bone bordering the prosthesis was excluded. Too high interfacial stresses were probably a major failure mechanism, especially in the rapidly failed noncemented prostheses. Negative long-term effects of the cement on the bone may have contributed to failure in the cemented resurface arthroplasties.

Adult↗
PubMed1993

On long-term maintenance of the osseointegrated response.

Every oral implant system must be backed up by controlled reporting of the clinical outcome. Look-alike implants do not necessarily show similar long-term clinical results. Osseointegration of an implant is not the same as clinical success, as secondary loss of osseointegration may be a frequent problem with respect to certain biomaterials as well as implant designs. For instance, with respect to solid cylinders, there is no published report documenting that such implants ever establish a steady state with respect to bone height. A continuous bone loss of half a millimetre or more will inevitably jeopardise the outcome of the implant over follow-up times of five to ten years. The author suggests a new way of reporting the outcome of oral implants in a four field table with Success, Survival, Unaccounted for and Failure categories. Success applies to those implants that meet with specific Success criteria. Survival are those implants that are still in the jaw of the patient but where criteria for success or failure are not met. Unaccounted for are implants in patients who dropped out from the study for one reason or the other including patient death. Failures are those implants which have been removed from the jaw or where absolute failure criteria such as implant mobility or therapy-resistant pain apply.

Alveolar Bone Loss↗
PubMed1993

Postimplantation irradiation for head and neck cancer treatment.

Eleven patients who had undergone surgical treatment for head and neck cancer and had titanium implants placed for skin-penetrating prostheses were irradiated postimplantation. The absorbed doses of irradiation to the implant region varied between 50 and 80 Gy. The time interval between implant surgery and irradiation varied from 4 to 60 months. Of 32 fixtures placed, 2 were removed as part of extended tumor surgery and 2 were lost in conjunction with induced chemotherapy. Five of the patients showed skin dehiscences around 9 implants after completed irradiation. Osteoradionecrosis developed in three of the patients after radiotherapy. If irradiation is to be performed in areas where titanium implants have been placed, it is recommended that all prostheses, frameworks, and abutments be removed before irradiation; the fixtures should be allowed to remain intact but should be covered with skin or mucosa.

Adolescent↗
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↗
PubMed1993

Treatment of the severely resorbed maxillae with bone graft and titanium implants: histologic review of autopsy specimens.

One of a series of patients with extremely resorbed maxillae treated with bone grafts from the hip in combination with Brånemark self-tapping fixtures died in a car accident 4 months after implant surgery. Autopsy specimens from this patient were analyzed to evaluate the amount and extent of "osseointegration" after 4 months of healing. Histologic examination revealed that minimal bone was in direct contact with the titanium and the general pattern was that of soft tissue screw anchorage. There were no signs of sequestering of the transplanted bone. The connection between the nasal cavity and the sinus mucosa with respect to the transplants seemed to be without adverse reactions. The superior part of the transplant did show signs of newly formed bone. The grafted specimens showed indications of delayed bone response compared to the nongrafted situation. All implants were clinically stable as studied postmortem.

Alveolar Bone Loss↗
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↗
PubMed1992

Tissue-integrated implants in children.

The aim of this study is to present our clinical experience with tissue-integrated extra-oral implants in children. Thirty consecutive cases of children with a total of 59 standard titanium fixtures inserted in the temporal bones and used as bone-anchorage for auricular epistheses (14 cases) and hearing aids (16 cases) were studied. The surgical procedure is performed in two steps and involves an extremely gentle handling of the soft tissue and bone. The patients were followed with regular check-ups for an average of 40 months after hearing aid/prosthesis fitting. The fixture survival rate was 96.6% for the whole group. The hearing aids had a reaction-free skin penetration in 91.67% of the postoperative observations and the prostheses had a reaction-free skin penetration in 75.00% of the postoperative observations. It is concluded that the use of 'osseointegrated', implants in carefully selected cases, in children, appears to be a reliable method for bone anchorage of epistheses and bone conduction hearing aids. A close follow-up and control of this patient category is especially important with respect to the long-term results.

Adolescent↗
PubMed1992

Histomorphometric analyses of hydroxyapatite-coated and uncoated titanium implants. The importance of the implant design.

Hydroxyapatite-coated and uncoated titanium screws were inserted in the rabbit tibial metaphysis and evaluated by histomorphometry after 6 months of follow-up. There was no difference in direct bone contact between the HA-coated implants and the uncoated controls. The effect of HA-coating on screw-shaped implants seems to be uncertain, in contrast to unthreaded cylindrical designs, where there is more abundant documentation in favour of HA-coated implants.

Animals↗
PubMed1992

Healing-in of root analogue titanium implants placed in extraction sockets. An experimental study in the beagle dog.

The aim of these animal experiments was to characterize and evaluate the healing-in of root analogue titanium implants fitting with high precision to the alveolar wall. Four beagle dogs were used in the study. The roots of the 3rd and 4th mandibular premolars in both quadrants of 3 dogs and in 1 quadrant of 1 dog (dog 4) were extracted after hemisection. Each root was machine-copied to 1 titanium analogue. In dog 4, however, 2 titanium analogues were fabricated from each of the 4 extracted roots. This enabled insertion of analogues also into the contralateral sockets obtained by extraction of the corresponding roots immediately before implant installation, which was undertaken 2 weeks after the first extractions. Thus, in all, 32 analogues were implanted in their respective (or contralateral) sockets following ridge incision and elevation of mucoperiosteal flaps. The analogues were carefully covered by the repositioned flaps. In dog 4, 2 analogues from the immediate sockets and 2 from the 2-week sockets were surgically exposed and supplied with titanium crowns after a healing period of 2 months. The healing after implantation was evaluated by clinical, radiographic and histological measures after 2, 12 or 36 months. Two analogues (6%) were lost due to early (during the 1st week) exposure to the oral cavity. Another 2 analogues (6%) were, although not exposed, encapsulated by soft tissue and were easily removed with a surgical forceps. Twenty-eight analogues (88%) were healed-in by contact between bone and implant (osseointegration).(ABSTRACT TRUNCATED AT 250 WORDS)

Alveolar Process↗
PubMed1992

Intermittent micromotion inhibits bone ingrowth. Titanium implants in rabbits.

We studied the effects of micromotion on bone ingrowth into a 1-mm canal through a titanium chamber implanted in the proximal tibia of rabbits. The implant surface became "osseointegrated," but an interior core was movable, allowing the central portion of the canal to be moved in relation to the ends. Thus, the ingrowing bone in the canal had to pass an area of ad latus motion. When implanted in rabbit tibiae, the canal became filled with ingrown cancellous bone. Bone ingrowth was inhibited by 20 cycles of 0.5-mm movement applied during a 30-second period once daily. With this regimen, the canal was usually filled with vascularized fibrous tissue and significantly less bone. The micromotion chamber may enable detailed studies of the effects of different motion variables on ingrowth of bone.

Alloys↗