Biomedical subjects

L Hermansson

Publications and source records attributed to L Hermansson.

18 recordsLinked to original sources

PubMed2006

A novel tool for high-resolution transmission electron microscopy of intact interfaces between bone and metallic implants.

A key feature in the understanding of the mechanisms of integration versus rejection of implanted materials is a deepened understanding of the elemental and molecular compositions of the interface zone between the surface of the synthetic man-made material and the biological components of tissue. Intact interfaces between metallic implants and tissues have not been able to image and analyse on the ultrastructural level with the common transmission electron microscopy (TEM) sample preparation techniques. By using focused ion beam microscopy for site-specific preparation of TEM samples, intact interfaces between metal implants and calcified tissue were imaged for the first time. The interface's elemental and crystallographic compositions were determined using energy dispersive X-ray mapping and electron diffraction. The developed technique fulfills a long-sought-for demand to correlate the surface properties of implanted metal prostheses with the fine structure and composition of preserved interfaces with tissues.

Animals↗

PubMed2005

Psychosocial adjustment in Swedish children with upper-limb reduction deficiency and a myoelectric prosthetic hand.

AIM: To study psychosocial adjustment and mental health in children with upper-limb reduction deficiency and a myoelectric prosthetic hand. METHODS: Sixty-two parents of children aged 8 to 18 y old answered a questionnaire concerning competence and behaviour/emotional problems in their children. Of the 62 children, 37 adolescents aged 11 to 18 y old answered questionnaires concerning competence, problems and mood state. The results were compared with Swedish normative data. The children were divided into five groups based on degree of myoelectric prosthetic use. RESULTS: Children with upper-limb reduction deficiency and a myoelectric prosthetic hand showed social competence and behaviour/emotional problems similar to Swedish standardized norms. However, withdrawn behaviour was significantly higher in all children, social competence was significantly lower in girls, and social activities were significantly lower in older children with upper-limb reduction deficiency. There was a significant difference between prosthetic use groups. Non-users had significantly more delinquent behaviour problems than full-time users. There was an interaction between gender and prosthetic use in their affect on competence and behaviour/emotional problems, yielding two contrasting patterns. CONCLUSION: Children with upper-limb reduction deficiency and a myoelectric prosthetic hand are as well adjusted psychosocially as their able-bodied peers. There are indications, however, of social stigmata related to the deficiency, which have to be considered differently in boys and girls.

Adolescent↗

PubMed2004

Chemical and biological integration of a mouldable bioactive ceramic material capable of forming apatite in vivo in teeth.

Chemically bonded ceramics have several advantages compared with conventional ceramics to be used as biomaterials. Especially the possibilities to harden the material at room temperature and to control the rheology are very beneficial. This paper investigates the interface formed in vivo between a calcium aluminate based dental filling material and teeth. Class 1 occlusal fillings were made in wisdom teeth and extracted after up to four weeks. Polished cross-sections of the teeth were studied with scanning electron microscopy (SEM), focused ion beam microscopy (FIB) and transmission electron microscopy (TEM). In order to analyse the distribution of elements at the interface elemental mapping was performed using STEM and EDX. The results showed that a tight bond forms between the filling material and tooth and no gap could be found even at high magnification. A 100-200 nm wide zone with an increase in oxygen was detected in the enamel next to the filling. The zone was denser than the rest of the enamel. Elemental mapping indicated an increase of silicon and a decrease of Ca at the interface. Dark field imaging and EDX mapping showed that the calcium aluminate system formed apatite in situ during hardening through precipitation.

Aluminum Compounds↗

PubMed2003

Mechanical properties of a permanent dental restorative material based on calcium aluminate.

This paper deals with some important mechanical properties (hardness, dimensional stability, compressive and flexural strength) of an experimental version of a translucent calcium aluminate dental restorative material. All samples investigated have been made from pre-pressed tablets, with a compaction degree of approximately 60%, hydrated using a 0.15 wt % Li salt solution as an accelerator. The samples were stored in water at 37 degrees C between the measurements. As reference materials one composite, Tetric Ceram, and one glass ionomer, Fuji II, were used with specimens prepared according to the manufacturer's recommendations. For the reference materials some of the properties were published data. The results show that the calcium aluminate material has sufficient mechanical properties to be used as a permanent dental restorative taking as a reference the ISO 9917 and the ISO 4049 as well as the reference materials. In addition the results indicate that the mechanical properties are controlled by the microstructure, which is mainly determined by the grain size of the filler.

Journal Article↗

PubMed2001

Upper limb deficiencies in Swedish children--a comparison between a population-based and a clinic-based register.

OBJECTIVE: To validate information in the Swedish Register for Congenital Malformations (SRCM). METHODS: A comparison was made with a clinic-based register kept at the Limb Deficiency and Arm Prosthesis Centre (LDAPC). The report frequency and the quality of the information in SRCM were analysed. Cases were classified according to a detailed, clinically relevant classification, the ISO 8548-1:89 method. OUTCOME MEASURES: The completeness of SRCM was first estimated. The Kappa statistic was then used to assess the agreement between the two registers regarding individual categories and across all categories. RESULTS: For the period 1973-1987, we found 125 cases of upper limb reduction deficiencies (ULRD) in the clinic-based register, of which 117 was found in the national register. The completeness of SRCM was thus estimated to be 94% (95% confidence interval 89-98%). The inter-register agreement varied from almost perfect agreement in laterality of deficiency (Kappa 0.98) to substantial agreement in type and level of deficiency (Kappa 0.72-0.79). For specific levels of transverse deficiency, however, the agreement varied between -0.05 and 0.66. CONCLUSIONS: The results indicate that SRCM, with its calculated underestimation of 6%, can be used for studying the prevalence of ULRD in Sweden. However, as SRCM is a surveillance register, the quality of some information seems to be low, making detailed description of cases difficult. Use of the population register data for clinical purposes could therefore result in lower validity. Additional information and follow-up of specific cases are therefore recommended.

Arm↗

PubMed1999

Zirconia-fluorapatite materials produced by HIP.

Composites of tetragonal zirconia and fluorapatite were sealed in steel tubes and hot isostatically pressed at 1200 degrees C. The phases formed in the samples were evaluated by X-ray powder diffraction. When the composites contained larger amounts of fluorapatite, the tetragonal zirconia changed gradually into the cubic phase with decreasing zirconia content. These phase changes occurred due to a transfer of calcium from fluorapatite, which acted as an additional dopant in zirconia. Small amounts of monoclinic zirconia were also present in all samples. The cell dimension in fluorapatite was changed with the composition of the composite. However, decomposition of the fluorapatite was not possible to detect. Vickers hardness and fracture toughness were measured and ranged from 5.1 to 10.8 GPa and 0.9-5.5 MPam1/2, respectively. Microstructures in the composites were studied with scanning electron microscopy.

Apatites↗

PubMed1997

Surface-dimpled commercially pure titanium implant and bone ingrowth.

The purpose of this investigation was to examine the effect of the surface macrostructure of a dimpled commercially pure titanium (cp Ti) implant on bone ingrowth in vivo by means of histological examination and a push-out test. Cylindrical implants were inserted in one femur of each experimental rabbit and the animals were killed at 1.5, 3 and 13 months after implantation. The femur with the implant of each animal was then examined in a push-out test. The fracture surfaces of the bone-implant interface after the push-out test were examined under light and electron microscopy. It seems that the dimpled cp Ti surface results in the increased retention of the cp Ti implant in bone due to interlocking between vital bone and the dimples.

Animals↗

PubMed1996

Sintering of partially-stabilized zirconia and partially-stabilized zirconia-hydroxyapatite composites by hot isostatic pressing and pressureless sintering.

In this study two sintering techniques, pressureless sintering (PS) and hot isostatic pressing (HIP), were used for comparing the sinterability of two yttria-partially-stabilized zirconia/hydroxyapatite (PSZ/HA) composites. Virtually dense ceramics were obtained using HIP at a maximum pressure of 160 MPa for 1 h at 1225 degrees C for both PSZ powders and their HA composites. The ceramic bodies, produced using PS at the same temperature as in the HIP process and higher, had densities from 80% to 97% of theoretical density, depending on the properties of the PSZ powders. FTIR spectra of composites sintered by HIP and PS at 1225 degrees C were compared, indicating a degradation of HA by PS but no degradation by HIP. The bending strength of HIPed ceramics was measured and found to be high. It is concluded that it is possible to produce dense PSZ/HA composites by the HIP or PS processes. For the PS, the reactivity of powders is the key factor during the densification. The HIP technique is the preferable technique for producing stable and dense HA-containing composites.

Biocompatible Materials↗

PubMed1995

Hydroxyapatite-alumina composites and bone-bonding.

Hydroxyapatite-alumina (HA/Al2O3) composites, with HA contents of 15, 25, 30 and 70, and pure HA as well as pure Al2O3, were densified at 1275 degrees C at a top pressure of 200 MPa for 2 h, using glass-encapsulated hot isostatic pressing. From the sintered ceramics, cylinders 2.8 x 6 mm2 were prepared by ultrasonic machining and implanted into the femoral cortical bones of 12 New Zealand White rabbits for 3 months. After killing the animals, the femur was dissected out and cut into three sections, each containing one cylinder. The specimens were mounted in a push-out device and force was applied along the long axis of the cylinder. The maximum force required to loosen the implant was recorded and the fracture surface of the bone implant was studied by scanning electron microscopy (SEM). The results indicate the important role of HA in new bone apposition to the implants, reflected by increasing bonding strength with increasing HA content in the composites. However, the relationship between HA content and the bonding strength was not linear. The composite with 70% HA and the pure HA ceramic had the same level of bonding strength and similar fracture interfaces in SEM, which supports the high bonding strength detected (about 15 MPa). Fractures occurred both in the bone and in the implant, indicating the stress transfer ability of the contact zone. This study presents qualitatively and quantitatively HA-dependent characteristics in bone-bonding. The mechanical strength of the composites was measured by a three-point bending test. The bending strength of the materials decreases with increasing HA content.

Aluminum Oxide↗

PubMed1993

High-strength dental gypsum prepared by cold isostatic pressing.

Powder of a dental plaster (Moldabaster, Bayer) was compacted by cold isostatic pressing (CIP) at 300 MPa for 10 min and immersed in water for 1 h. The compressive strength of the CIP-processed material was compared with that of conventionally processed material. The green block of plaster before water immersion was carvable with a green density and green strength of 50% and 5 MPa, respectively. The compressive strength of the CIP-processed gypsum after 24 h was three times higher than that of conventionally processed, 103 compared with 29 MPa, and the microhardness (Vickers hardness number, VHN) of CIP-processed materials was 40 compared with 12 VHN. An increase of density was also recorded. It seems that the CIP process produced a dense and pore-free gypsum with a composite-like structure. The high-strength gypsum processed by CIP may extend the applications of this material in the medical field as implant materials.

Biomechanical Phenomena↗

PubMed1993

Evaluation of biocompatibility of various ceramic powders with human fibroblasts in vitro.

Cell reaction to powders of ceramics was studied in vitro. Cultured human fibroblasts were exposed to different types of ceramic powders: zirconia (ZP), alumina (A), tricalcium phosphate (TCP) and hydroxyapatite (HA), at various concentrations. The cell viability at the different exposure times was measured by the colony formation (expressed as colony forming efficiency, CFE), neutral red uptake (NR) and colorimetric tetrazolium (MTT) reduction. Alumina and hydroxyapatite showed no cytotoxic effects at studied doses (1-500 mug/ml) while zirconia and tricalcium phosphate inhibited cell viability, with 50% of CFE reduction at the concentration of about 50 mug/ml. In order to study the cytotoxic mechanism of zirconia powder, two further experiments were included, viz. the cellular response to the sintered zirconia ceramic powders (CZP) which were obtained by crushing the sintered ceramic material; and the measurement of the degradation of zirconia ceramic plate in the different solutions, i.e., either in saline or in 0.02 M lactic acid (pH 2.72). Similar cell reactions were obtained for the CZP and ZP by using MTT and NR assays. Slow releases of ions from zirconia ceramic plate, yttrium in both solutions and zirconium and yttrium in lactic acid, were detected.

Aluminum↗

PubMed1991

Evaluation of the mechanical properties of hot isostatically pressed titania and titania-calcium phosphate composites.

A number of composites based on titania and calcium phosphates, hydroxyapatite, bone ash or beta-tricalcium phosphate, were sintered by glass-encapsulated hot isostatic pressing at 925 degrees C. The mechanical properties of the titania and titania-calcium phosphate composites--three-point bending strength, fracture toughness and Young's modulus--were 250-450 MPa, 2.5-2.9 MPa m1/2 and 230-270 GPa, respectively. Hardness and density were also measured. The results suggest that these composites have potential applications in medicine as implant materials.

Calcium Phosphates↗

PubMed1990