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Biomedical subjects

J Ahlqvist

Publications and source records attributed to J Ahlqvist.

At least 19 recordsLinked to original sources
PubMed2006

The use of dental radiographs for identification of children with unrestored dentitions.

The success of dental identification is often dependent on the extent of previous dental care and the location of detailed dental records. However, several factors limit available comparable data among children. There are often no clinical indications for dental radiography before the age of five and many children and adolescents have no restorative care. This reduces the amount of individualizing information suitable for comparative identification. The aim of this study was to investigate matching of dental x-rays from children without fillings at different ages, and to see if radiographic expertise facilitated radiographic comparison. Five general dental practitioners (GDP) and five oral and maxillofacial radiologists (OMR) attempted to match bitewing examinations from 30 children. The results showed that dentists are likely to match bitewing radiographs in these conditions. This likelihood is further enhanced when oral and maxillofacial radiologists compare images. This suggests that manual comparison of bitewings from children allow sufficient concordant visible points for identification to occur.

Adolescent↗
PubMed2005

Co-purification of soluble membrane cofactor protein (CD46) and human herpesvirus 6 variant A genome in serum from multiple sclerosis patients.

The association of human herpesvirus 6 (HHV-6) and multiple sclerosis (MS) has been supported by several immunological and molecular studies. Recently, membrane cofactor protein (CD46) has been identified as the cellular receptor for the A and B variants of HHV-6. Elevated levels of soluble CD46 (sCD46) have been reported in the serum and CSF of MS patients. The aim of this study was to investigate a possible correlation between elevated levels of soluble CD46 and the presence of serum HHV-6 DNA in MS patients. An immunoaffinity column comprised of immobilized monoclonal antibodies to CD46 was developed to isolate sCD46 from cell free body fluids of MS patients and controls. After immunoaffinity purification, DNA was extracted from anti-CD46 column eluates and subjected to PCR amplification. Of the 42 MS samples tested, 4 serum samples were HHV-6 positive, 3 of which were typed as HHV-6A. The co-purification of sCD46 and HHV-6 DNA from MS sera indicates that HHV-6 is tightly connected to its receptor, CD46, in the serum of MS patients.

Antigens, CD↗
PubMed2004

10-year follow-up of onlay bone grafts and implants in severely resorbed maxillae.

Thirty patients with extremely resorbed maxillae had reconstructive bone grafts from the ala iliaca and endosseous implants in a one-stage procedure. The first ten patients constituted a development group and the following 20 patients a routine group. The marginal bone level and implants success rate was evaluated in a prospective long-term follow-up for a minimum of 10 years (10-13 years). Clinical and radiographic examinations were performed at 6 months and then annually up to 5 years. The final examinations were performed at the 10-year follow-up. The bridges were removed at every clinical examination. Marginal bone loss was seen up to the 3-year examination, where it averaged 4.6 mm in the routine group. Between the 3- and 10-year follow-up no significant change was registered. The initial bone loss was probably due to the design of the 3.6 mm conical unthreaded marginal part of the implant. The implant success rate was 83.1% in the routine group. Failures mostly occurred during the first 2 years (14 out of 20). A substantial amount of bone can be gained in patients with extremely resorbed maxillae, when treated with bone graft according to the procedure described in this study.

Adult↗
PubMed2004

Virtual reality for simulation of radiographic projections: validation of projection geometry.

OBJECTIVE: To develop a software for virtual reality (VR) simulation of X-ray images based on perspective projections through a patient model derived from data from a CT examination and to evaluate the accuracy in the projection geometry obtained by the software. METHODS: A VR software was developed on a personal computer, with models of a patient, an X-ray machine and a detector. The model of the patient was derived from data from a CT examination of a dry skull. Simulated radiographic images of the patient model could be rendered as perspective projections based on the relative positions between the models. The projection geometry of the software was validated by developing an artificial CT data set containing high attenuation points as objects to be imaged. The accuracy in projection geometry was evaluated in a systematic way. The distances between two dots, representing the projected test points in the simulated radiographic images, were measured. They were compared with theoretical calculations of the corresponding distances using traditional mathematical tools. RESULTS: The difference between the simulated and calculated projected distances never exceeded 0.5 mm. The error in simulated projected distances was in most cases within 1%. No systematic errors were revealed. CONCLUSION: The software, developed for personal computers, can produce simulated X-ray images with high geometric accuracy based on perspective projections through a CT data set. The software can be used for simulation of radiographic examinations.

Computer Simulation↗
PubMed2002

Bone graft remodelling and implant success rate in the treatment of the severely resorbed maxilla: a 5-year longitudinal study.

A total of 30 patients, 10 in a developmental group and 20 in a routine group, with extremely resorbed maxillae were treated with bone grafting from the hip and implant placement in a one-stage procedure. All patients were followed for a minimum of 5 years and were examined regarding the long-term success rate of the implants and marginal bone level. The implant success rate was 74.6% for the whole patient group and 85.8% for the routine group, after 5 years. The marginal bone along the implant surface decreased continuously, up to 3 years and thereafter the bone level stabilized. In the routine group, changes in bone graft dimensions over time were also evaluated by computerized tomography. The mean height of the bone graft postoperatively at all implant sites was 8.3 mm. The total mean bone height, including bone graft and residual alveolar crest, was 12.4 mm. After 5 years the total bone height had decreased to a mean of 10 mm. The mean width of the bone graft was 12 mm postoperatively and 8.7 mm at the 5-year examination. A substantial amount of bone can be gained in patients with extremely resorbed maxillae, when treated with bone graft according to the procedure described in this study.

Adult↗
PubMed2001

Atherosclerosis, and Newton, Poiseuille, Reynolds and Prandtl.

Atherosclerotic fibrous plaques typically manifest at inlets of branches and in expansions etc. of large elastic arteries. A resting man with a surface area of 1.78 m(2)produces energy at a rate of 100 W (86 kcal/h), mainly by core organs. Core blood heat is convected to arterial walls and conducted through tissues to be lost from body surfaces. High losses are compensated by an increase in the basal metabolic rate, and vice versa. In laminar flow, the fluid-tube wall heat transfer coefficient is higher close to tube inlets than downstream. Unless lipoprotein etc. suspects are exceptions from the rule that an increase in temperature speeds up chemical reactions, transfer of core heat may contribute to plaque localization. In laminar flow, heat transfer is little influenced by viscosity. Hence correlations between blood viscosity and cardiovascular disease (CVD) may reside in other mechanisms: viscosity limits flow relatively more in small than in large arteries, and viscosity-linked thixotropic properties of blood increase resistance to flow in capillaries and postcapillary venules (exchange vessels). The exchange vessels of large arteries belong to the vasa vasorum, in which reduction of flow induces diffuse parent artery wall changes found also in plaques. Correlations between blood viscosity and peripheral symptoms of CVD may be explained by reduced flow in vascular loops of symptomatic organs, even if maximum flow is limited by upstream plaques. Physiological differences in the type of blood flow and in blood-tissue exchange between vessels of different size may shed light on apparent paradoxes in research on CVD.

Animals↗
PubMed2000

Swelling of synovial joints - An anatomical, physiological and energy metabolical approach.

The direction and part of the rate of fluid filtration between synovial capillary (subscript capill) plasma and joint (subscript j) cavity fluid depends on the hydrostatic (P(capill)-P(j)) and colloid osmotic (COP(plasma)-COP(j)) pressure differences and on the osmotic efficiency (coefficient sigma) of 'colloids' across the barrier between plasma and synovial fluid. The rate of filtration also depends on capillary endothelial hydraulic conductance (L(p)) and surface area (A). Synovial fluid protein is removed by lymphatics, or split to be resorbed or used up by cells. Physiologists put together as equations the above, as well as other terms, all of these influenced by numerous factors. The equations offer a frame for a multifactorial approach to diseases associated with joint swelling and suggest, among others, that in the presence of weak generalized exsudation, synovial joints are loci minores resistentiae to swelling. The influence of joint cartilage energy demands on synovial blood flow may have been underrated. There are many accepted clinical, laboratory and morphological findings that fit this physiological frame that merits further clinical research.

Journal Article↗
PubMed1998

Sources of radiographic distortion in conventional and computed tomography of the temporal bone.

OBJECTIVES: To identify those bony regions of the glenoid fossa where, due to the inclination, there is an increased risk of radiographic distortion in conventional and computed tomography (CT). METHODS: The inclination of the roof and posterior wall of the glenoid fossa was determined relative to established imaging planes. Measurements were performed on 50 corrected coronal MR and 50 axial CT images and 200 sagittal cryosections of 50 temporomandibular joints (TMJs). The location of regions with unfavourable bone wall inclination was identified using the condyle as a reference. RESULTS: The inclination of parts of the fossa roof exceeded the limit for reliable depiction in corrected sagittal and coronal planes in 40% and 8% of the joints respectively. The inclination of parts of the posterior wall of the fossa exceeded the limit for reliable depiction in corrected sagittal and in true sagittal planes in 100% and 84% of the joints respectively. In 84% of the joints the inclination exceeded the limit for reliable depiction in the axial plane. For both bone walls the regions with unfavourable inclination were in the medial part of the joint. CONCLUSIONS: The angulation of parts of the roof and posterior wall of the glenoid fossa in relation to established imaging planes makes them highly susceptible to distortion. The oblique coronal projection is well suited for depiction of the roof of the fossa and preferable to a sagittal projection. An oblique axial projection is required for the posterior wall.

Adolescent↗
PubMed1998

Joint fluid hydrostatic pressures that empty synovial capillaries of red cells have a wide range and correlate with pressures emptying arterioles.

OBJECTIVE: To study if, as predicted by calculations based on 3 Starling pressures, the fourth one, capillary pressure, may increase enough to contribute to joint swelling. METHODS: At magnifying arthroscopy, red cells mostly flow separated from each other in capillaries and precapillary vessels (arterioles). These are emptied of erythrocytes at intraarticular injection of saline to "tamponade" pressures. Patients sent for arthroscopy of the knee joint for mechanical or other lesions, or "internal derangement" (n = 30) or osteoarthritis (n = 26) were studied. RESULTS: The range of capillary (including postcapillary venular) tamponade pressure was 9-70 mm Hg. It correlated (r = 0.536, p < 0.001) with arteriolar tamponade pressure (range 20-100 mm Hg). CONCLUSION: If intravascular hydrostatic pressure is the main determinant of tamponade pressure, then increase of capillary pressure, possibly due to arteriolar dilatation induced precapillary pressure increase, may be a key mechanism in enhanced formation of synovial fluid.

Adolescent↗
PubMed1996

Autogenous onlay bone grafts fixed with screw implants for the treatment of severely resorbed maxillae. Radiographic evaluation of preoperative bone dimensions, postoperative bone loss, and changes in soft-tissue profile.

Thirty patients with severely resorbed edentulous maxillae underwent combined treatment of iliac bone onlay graft and titanium implants. The patients were followed for 3 years. They were radiographically examined before surgery to evaluate the bone volume at the intended implant sites. Only 13/156 implant sites were suitable for implant insertion. The bone level at the implant surfaces was evaluated after 6 months and 1, 2, and 3 years, respectively. There was a continuing decrease of the bone level throughout the follow-up period with a mean loss of 4.9 mm after 3 years and with no difference between sexes. Twenty-six implants were radiographically examined before removal, and only three of these implant sites showed radiographic signs of failure. The soft-tissue profile was analyzed cephalometrically by the subtraction technique. The upper lip generally moved inward and the apex of the nose and the columella downward and inward. The anterior facial height increased in most of the patients, resulting in a downward and inward change of the lower lip, the mentolabial sulcus, the soft-tissue pogonion, and the soft-tissue gnathion.

Adult↗
PubMed1995

Karl Popper.

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England↗