Biomedical subjects

J Jönsson

Publications and source records attributed to J Jönsson.

At least 19 recordsLinked to original sources

PubMed2004

Does excessive occlusal load affect osseointegration? An experimental study in the dog.

AIM: The purpose of this study was to evaluate the effect of excessive occlusal load following placement of titanium implants in the presence of healthy peri-implant mucosal tissues. MATERIALS AND METHODS: Mandibular bilateral recipient sites in six Labrador dogs were established by extracting premolars and molars. After 3 months, two TPS (titanium plasma sprayed) implants and two SLA (sandblasted, large grit, acid etched) implants were placed on each side of the mandible in each dog. Three implants were lost in the initial healing phase, leaving 45 implants for evaluation. Following 6 months of healing, gold crowns were placed on implants on the test side of the mandible. The crowns were in supra-occlusal contact with the opposing teeth in order to create excessive occlusal load. Implants on the control side were not loaded. Plaque control was performed throughout the experimental period. Clinical measurements and standardised radiographs were obtained at baseline and 1, 3 and 8 months after loading. At 8 months, the dogs were killed and histologic analyses were performed. RESULTS: At 8 months, all implants were osseointegrated. The mean probing depth was 2.5+/-0.3 and 2.6+/-0.3 mm at unloaded and loaded implants, respectively. Radiographically, the mean distance from the implant shoulder to the marginal bone level was 3.6+/-0.4 mm in the control group and 3.7+/-0.2 mm in the test group. Control and test groups were compared using paired non-parametric analyses. There were no statistically significant changes for any of the parameters from baseline to 8 months in the loaded and unloaded implants. Histologic evaluation showed a mean mineralised bone-to-implant contact of 73% in the control implants and 74% in the test implants, with no statistically significant difference between test and control implants. CONCLUSION: In the presence of peri-implant mucosal health, a period of 8 months of excessive occlusal load on titanium implants did not result in loss of osseointegration or marginal bone loss when compared with non-loaded implants.

Acid Etching, Dental↗

PubMed2000

Endovascular healing is inadequate for fixation of Dacron stent-grafts in human aortoiliac vessels.

BACKGROUND: migration and kinking of stent-grafts can occur late after endovascular aneurysm repair. It is unknown if endovascular grafts incorporate enough to be permanently anchored. In this report, healing of aortic stent-grafts was assessed in humans. PATIENTS AND METHODS: we retrieved 23 Dacron stent-grafts from patients treated for an aortic aneurysm since 1993. Twelve stent-grafts were explanted at late conversion to open repair and 11 at autopsy. The deaths were unrelated to graft fixation. The median age of the patients was 74 years (IQR 55-84 years) and the grafts were explanted 9 months (1-31 months) after insertion. Microscopic slides were prepared by conventional techniques or by cutting and grinding arterial specimens embedded in plastic with the stent-grafts in situ. RESULTS: the stent-grafts detached readily from the native arteries at surgery or autopsy, except when the stents had hooks or barbs which engaged the vessel wall. A space filled with poorly organised blood components persisted between the graft and the aortic wall 2.5 years after implantation. No firm incorporation of the grafts was observed proximally in the aneurysm neck or distally in the iliac segment. A friable neo-intimal layer covered parts of the luminal aspect of the grafts. CONCLUSIONS: endovascular healing provides poor fixation of Dacron stent-grafts in humans. At present, fixation relies on the mechanical properties of the stent-grafts.

Aged↗

PubMed1992

Osseous response to implanted natural bone mineral and synthetic hydroxylapatite ceramic in the repair of experimental skull bone defects.

The purpose of this study was to assess and compare the osseous responses to implanted particles of resorbable anorganic xenograft bone mineral and non-resorbable dense synthetic hydroxylapatite of two different granule sizes. Four trephine calvarial defects were produced in each of 13 adult rabbits. The experimental materials were subsequently implanted in three defects, leaving the fourth defect for control purposes. Six animals were killed 4 weeks after surgery and seven at 14 weeks. The tissue responses were assessed by contact radiography, light microscopy, and histometry. The biocompatibility of the implants was confirmed. All defects healed uneventfully, although the resorbable hydroxylapatite seemed to promote initial bone regeneration. The importance to orthognathic surgery of early and effective healing of bone gaps, as well as of the advantage of implant resorbability to bone remodeling, are discussed.

Absorption↗

PubMed1992

Contribution of autogeneic membranous bone chips and bone paste to healing of rabbit skull defects.

In skeletal surgery, bone chips and bone paste are often used to facilitate bony repair. However, no comparative investigation between these forms of bone graft implantation has been undertaken. In this study four trephine skull defects were produced in each of 14 adult rabbits and inlays of bone paste and two separate amounts of bone chips were then implanted in each animal. The results were compared relative to a control defect and assessed by gross inspection, light microscopy, and contact radiography after periods of 4 and 15 wk. Bone chips offered only minor advantages over controls in the defects investigated and differences in bony regeneration between the diversified amounts of bone chips were negligible. After bone paste implantation, a cellular and mature bone was rapidly produced. The clinical significance of these findings is discussed.

Animals↗

PubMed1992

Regenerative response to membranous and enchondral lyophilized allogeneic bone in rabbit skull defects.

The regenerative responses of inlays of lyophilized allogeneic bone of membranous (skull) and enchondral (tibia) origin were studied in an experimental cranioplasty model in rabbits. The lyophilized bone particles were also bioassayed for inductive bone production in an orthotopic critical size defect rat model. Three trephined calvarial defects were evaluated in each of 14 adult rabbits. The experimental materials were implanted into two of the defects and the third was left empty for control purposes. The implants disclosed no major structural divergences as assessed by scanning electron microscopy. Healing was evaluated by light microscopy and contact radiography after periods of four and 15 weeks. The lyophilized bone allografts of both embryonic origins displayed a similar fashion of bone regeneration, bone marrow reappearance, and volumetric density of trabecular bone substance and displayed no obvious differences between experimental groups or intervals. The two materials exhibited low osteoinductive potential.

Animals↗

PubMed1990

Regeneration of cranial suture and bone plate lesions in rabbits. Implications for positioning of osteotomies.

The positioning of osteotomies in intramembranous cranial bone was studied by exploring the pattern of bone regeneration in growth areas (the sutural region) as compared to that of the bone plate proper. Trephine defects in the left coronal suture area and the right parietal bone were produced in fifty-nine young rabbits. A pilot study to refine operative and analytical methods comprised 22 animals. The experiments were terminated at one, three, and six weeks after surgery. The bone regenerative response was assessed by x-ray planimetry, plain microscopy, enzyme histochemistry, and fluorescent labelling. Only minor divergences in healing capacity between the two defects were found. No adverse effects on the growth process were indicated. As to clinical management, the findings suggest that osteotomies designed to traverse sutural areas will, under normal circumstances, regenerate in a similar manner and rate to adjoining bone plates.

Acid Phosphatase↗

PubMed1974