| 1. |
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| 2. |
- Åberg, Jonas, 1982-, et al.
(författare)
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Biocompatibility and resorption of a radiopaque premixed calcium phosphate cement
- 2012
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Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 100A:5, s. 1269-1278
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Tidskriftsartikel (refereegranskat)abstract
- Calcium phosphate cements (CPC) are used as bone void filler in various orthopedic indications; however, there are some major drawbacks regarding mixing, transfer, and injection of traditional CPC. By using glycerol as mixing liquid, a premixed calcium phosphate cement (pCPC), some of these difficulties can be overcome. In the treatment of vertebral fractures the handling characteristics need to be excellent including a high radio-opacity for optimal control during injection. The aim of this study is to evaluate a radiopaque pCPC regarding its resorption behavior and biocompatibility in vivo. pCPC and a water-based CPC were injected into a circle divide 4-mm drilled femur defect in rabbits. The rabbits were sacrificed after 2 and 12 weeks. Cross sections of the defects were evaluated using histology, electron microscopy, and immunohistochemical analysis. Signs of inflammation were evaluated both locally and systemically. The results showed a higher bone formation in the pCPC compared to the water-based CPC after 2 weeks by expression of RUNX-2. After 12 weeks most of the cement had been resorbed in both groups. Both materials were considered to have a high biocompatibility since no marked immunological response was induced and extensive bone ingrowth was observed. The conclusion from the study was that pCPC with ZrO2 radiopacifier is a promising alternative regarding bone replacement material and may be suggested for treatment of, for example, vertebral fractures based on its high biocompatibility, fast bone ingrowth, and good handling properties.
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| 3. |
- Åberg, Jonas, 1982-, et al.
(författare)
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In vitro and in vivo evaluation of an injectable premixed calcium phosphate cement : cell viability and immunological response from rat
- 2010
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Ingår i: International Journal of Nano and Biomaterials. - 1752-8941. ; 3:3, s. 203-221
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Tidskriftsartikel (refereegranskat)abstract
- By using premixed calcium phosphate cement (CPC) the handling properties of the cement are drastically improved, which is a challenge for traditional injectable CPC. In this article, a premixed acidic CPC has been compared to a conventional water mixed brushite cement to evaluate whether the premixed concept affects the biological response. The cements were evaluated regarding the pH-variation in simulated body fluid (SBF). Further, the biocompatibility of the cement with human mesenchymal stem cells (MSC) was studied in vitro and eventual inflammation properties studied in vivo, after subcutaneous material injections in rats. A larger pH decrease was seen for the conventional cement than the premixed cement in SBF. For both materials, > 90% of the MSC remained alive in vitro. No systemic or macroscopic inflammation was detected, only a mild microscopic inflammation was detected around both materials. In addition to the handling benefit of premixed cements compared to conventional water mixed CPC, the premixed CPC in the present study demonstrated high and in comparison to conventional CPC comparable biocompability, both in vitro and in vivo.
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| 4. |
- Ballo, Ahmed, 1978, et al.
(författare)
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Bone tissue reactions to biomimetic ion-substituted apatite surfaces on titanium implants
- 2012
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Ingår i: Journal of the Royal Society Interface. - : The Royal Society. - 1742-5689 .- 1742-5662. ; 9:72, s. 1615-1624
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate the bone tissue response to strontium-and silicon-substituted apatite (Sr-HA and Si-HA) modified titanium (Ti) implants. Sr-HA, Si-HA and HA were grown on thermally oxidized Ti implants by a biomimetic process. Oxidized implants were used as controls. Surface properties, i.e. chemical composition, surface thickness, morphology/pore characteristics, crystal structure and roughness, were characterized with various analytical techniques. The implants were inserted in rat tibiae and block biopsies were prepared for histology, histomorphometry and scanning electron microscopy analysis. Histologically, new bone formed on all implant surfaces. The bone was deposited directly onto the Sr-HA and Si-HA implants without any intervening soft tissue. The statistical analysis showed significant higher amount of bone-implant contact (BIC) for the Si-doped HA modification (P = 0.030), whereas significant higher bone area (BA) for the Sr-doped HA modification (P = 0.034), when compared with the non-doped HA modification. The differences were most pronounced at the early time point. The healing time had a significant impact for both BA and BIC (P < 0.001). The present results show that biomimetically prepared Si-HA and Sr-HA on Ti implants provided bioactivity and promoted early bone formation.
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| 5. |
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| 6. |
- Baresel, Christian, et al.
(författare)
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WEBAP - Vågdriven syrepump för Östersjön
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Projektets huvudsakliga syfte har varit att utveckla och testa en metod för syresättning av djupvatten i Östersjön genom nedpumpning av syrerikt ytvatten med hjälp av vågdrivna syrepumpar. Inom projektet har två olika pilotanläggningar tagits fram, byggts och varit i drift mellan 2010 och 2013. En vågdriven pump (WEBAP I) testades under 2 år i Hanöbukten utanför Simrishamn och en elektrisk pump (WEBAP II) placerades i Kanholmsfjärden i Stockholms skärgård. Förutom tester for att undersöka den vågdrivna pumpens effektivitet och framtida utformning så har även effekterna av syresättning på omgivande vattens syre- och fosforkoncentrationer studerats under projektet. Med hjälp av modeller studerades uppskalning av tekniken samt beräkningar av åtgärdens klimatavtryck (carbon footprint) med hjälp av förenklad livscykelanalysmetodik (LCA). Projektet har tagit fram olika tekniska alternativ av syrepumpar för olika behov. Den vågdrivna syrepumpen använder sig direkt av vågorna som energi- och syreresurs vilket har flera fördelar, bland annat en enkel och robust konstruktion samt lokalt tillförd energi genom att vågor nyttjas. Den eldrivna pumpen är en nyutveckling som möjliggör att pumpning kan drivas av vind- och solenergi eftersom effektförbrukningen i pumpen är låg. De två testade systemen visade sig kunna pumpa ner stora mängder ytvatten, men ytterligare förbättringar och utveckling krävs för långsiktigt störningsfri funktion. Rapporten ger en del förslag till sådan utveckling.
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| 7. |
- Berglund, Anna-Karin, 1979, et al.
(författare)
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Nucleotide pools dictate the identity and frequency of ribonucleotide incorporation in mitochondrial DNA. : Mapping ribonucleotides in mitochondrial DNA
- 2017
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Ingår i: PLoS genetics. - : Public Library of Science (PLoS). - 1553-7404 .- 1553-7390. ; 13:2
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Tidskriftsartikel (refereegranskat)abstract
- Previous work has demonstrated the presence of ribonucleotides in human mitochondrial DNA (mtDNA) and in the present study we use a genome-wide approach to precisely map the location of these. We find that ribonucleotides are distributed evenly between the heavy- and light-strand of mtDNA. The relative levels of incorporated ribonucleotides reflect that DNA polymerase γ discriminates the four ribonucleotides differentially during DNA synthesis. The observed pattern is also dependent on the mitochondrial deoxyribonucleotide (dNTP) pools and disease-causing mutations that change these pools alter both the absolute and relative levels of incorporated ribonucleotides. Our analyses strongly suggest that DNA polymerase γ-dependent incorporation is the main source of ribonucleotides in mtDNA and argues against the existence of a mitochondrial ribonucleotide excision repair pathway in human cells. Furthermore, we clearly demonstrate that when dNTP pools are limiting, ribonucleotides serve as a source of building blocks to maintain DNA replication. Increased levels of embedded ribonucleotides in patient cells with disturbed nucleotide pools may contribute to a pathogenic mechanism that affects mtDNA stability and impair new rounds of mtDNA replication.
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| 8. |
- Corell, Hanna, 1977, et al.
(författare)
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Depth distribution of larvae critically affects their dispersal and the efficiency of marine protected areas
- 2012
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 467, s. 29-46
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Tidskriftsartikel (refereegranskat)abstract
- This study aims to improve estimates of dispersal by including information on larval traits, and in particular to explore how larval depth distribution affects connectivity and MPA (marine protected area) functionality in the Baltic Sea. A field survey showed that both invertebrates and fish differed in their larval depth distribution, ranging from surface waters to >100 m. A biophysical model of larval dispersal in the Baltic Sea showed that decreased depth distribution increased average dispersal distance 2.5-fold, decreased coastal retention and local recruitment, and substantially increased connectivity. Together with pelagic larval duration (PLD), depth distribution explained 80% of total variation in dispersal distance, whereas spawning season, and geographic and annual variations in circulation had only marginal effects. Median dispersal distances varied between 8 and 46 km, with 10% of simulated trajectories dispersing 30 to 160 km depending on drift depth and PLD. In the Baltic Sea, the majority of shallow Natura 2000 MPAs are <8 km in diameter. In the present study, only 1 of the 11 assessed larval taxa would have a recruitment >10% within MPAs of this size. Connectivity between MPAs was expected to be low for most larval trait combinations. Our simulations and the empirical data suggest that the MPA size within the Natura 2000 system is considerably below what is required for local recruitment of most sessile invertebrates and sedentary fish. Future designs of MPA networks would benefit from spatially explicit biophysical models that consider dispersal and connectivity for complex circulation patterns and informed larval traits.
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| 9. |
- Corell, Hanna, 1977-, et al.
(författare)
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Larval depth distribution critically affects dispersal and the efficiency of marine protected areas
-
Ingår i: Marine Ecology Progress Series. - 0171-8630 .- 1616-1599.
-
Tidskriftsartikel (refereegranskat)abstract
- This study aims to improve estimates of dispersal by including information on larval traits, and in particular to explore how larval depth distribution affects connectivity and MPA functionality in the Baltic Sea. A field survey showed that both invertebrates and fish differed in their larval depth distribution ranging from surface waters to more than 100 m. A biophysical model of larval dispersal in the Baltic Sea showed that decreased depthdistribution increased average dispersal distance 2.5 times, decreased coastal retention and local recruitment, and increased connectivity substantially. Together with pelagic larval duration (PLD), depth distribution explained 80% of total variation in dispersal distance, whereas spawning season, geographic and annual variations in circulation had only marginal effects. Median dispersal distances varied between 8 and 46 km, with 10% of simulated trajectories dispersing beyond 30-160 km depending on drift depth and PLD. In the Baltic Sea, the majority of shallow Natura 2000 MPAs are smaller than 8 km. In the present study, only one of the 11 assessed larval taxa would have a local recruitment >10% within MPAs of this size. Connectivity between MPAs was expected to be low for most larval trait combinations. Our simulations and the empirical data suggest that the MPA size within the Natura2000 system is considerably below what is required for local recruitment of most sessile invertebrates and sedentary fish. Future designs of MPA networks would benefit from spatially explicit biophysical models that consider dispersal and connectivity for complex circulation patterns and informed larval traits.
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| 10. |
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| 11. |
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| 12. |
- Engqvist, Anders, et al.
(författare)
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Flow regimes and long-term water exchange of the Himmerfjarden estuary
- 2009
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Ingår i: Estuarine, Coastal and Shelf Science. - : Elsevier BV. - 0272-7714 .- 1096-0015. ; 83:2, s. 159-174
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Tidskriftsartikel (refereegranskat)abstract
- A numerical model of processes determining the water exchange encountered in Baltic coastal archipelagos is calibrated and validated against salinity and temperature field data spanning two decades with approximately bi-weekly resolution assessed in the Himmerfjärden estuary. This area is resolved into 17 basins interconnected by 38 individual straits of varying geometrical properties using GIS-based methods. All formulations of the strait exchange flows are free from parameters that need calibration and permit computations of the flow through a strait contraction with or without a coincident sill under a flow classification scheme, of which the first one (a) consists of two groups of multiple layers including aspirated layers from levels beneath the sill crest. The other regimes are as follows. (b) Pure barotropic flow; (c) rotationally controlled flow and (d) plug-flow, which serves as resort solution for flow situations that cannot be solved with (a) and also for computation of the barotropic part of the total flow. For long canals where friction effects act to reduce the flow, a fifth exchange regime is used. The vertical mixing formulation is based on energy balances between supplied wind energy and its work against buoyancy forces. The values of semi-empirical parameters involved in the mixing scheme have been established by calibration against measured data of the first decade period. A statistical evaluation is performed comparing the model results with the measurements of the second decade. It is found that the accuracy of the model is yet limited by the poor temporal resolution in the boundary and the thermal forcing. The overall accuracy of this approach is found to be comparable to earlier model studies in the same area. Since the exchange flows are now based on first principles and are applied to four times more basins, it seems that this more articulated model approach can confidently be applied to more complex archipelago areas.
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| 13. |
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| 14. |
- Engqvist, Anders, et al.
(författare)
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Vattenutbyte i Björnöfjärdssystemet
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Vattenutbytet för hela Björnöfjärdssystemet (uppdelat i sina tre delbassänger: Björnöfjärden, Säbyviken samt Torpe-Infjärden) har modellerats för 12-årsperioden 1993 till och med 2004 med CouBa -modellen. Drivningen har utformats som vattenstånds- och täthetsvariationer för den hydrauliska randen mot Nämdöfjärden, vinddriven vertikal omblandning samt sötvattentillrinning. Hypsografiska sund- och bassängdata har omformats till det format som modellen kräver, men har för övrigt inte modifierats t.ex. för den vassbeväxning som föreligger i sunden. Långtidsmedelvärdet för det utbytta volymflödet till hela Björnöfjärdsområdet har beräknats till 0,96 m3/s, vilket är i det närmaste identiskt med tidigare uppskattning baserad på massbalans för salt. Den genomsnittliga uppehållstiden för vattnet (AvA) i Björnöfjärdssystemet har på samma sätt beräknats till cirka 4,5 månad för ytvattnet respektive 3 månader för bottenvattnet. I jämförelse med majoriteten av Östersjöns kustområden är detta att betrakta som ett mycket långsamt vattenutbyte, vilket förklaras av de morfologiska förhållandena med ett smalt och grunt sund mellan Björnöfjärdssystemet och den utanförliggande Nämdöfjärden.
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| 15. |
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| 16. |
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| 17. |
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| 18. |
- Engqvist, Ulf, et al.
(författare)
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Child and adolescent psychiatric patients and later criminality
- 2007
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Ingår i: BMC Public Health. - : Springer Science and Business Media LLC. - 1471-2458. ; 7:147, s. 221-
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Tidskriftsartikel (refereegranskat)abstract
- Background Sweden has an extensive child and adolescent psychiatric (CAP) research tradition in which longitudinal methods are used to study juvenile delinquency. Up to the 1980s, results from descriptions and follow-ups of cohorts of CAP patients showed that children´s behavioural disturbances or disorders and school problems, together with dysfunctional family situations, were the main reasons for families, children, and youth to seek help from CAP units. Such factors were also related to registered criminality and registered alcohol and drug abuse in former CAP patients as adults. This study investigated the risk for patients treated 1975-1990 to be registered as criminals until the end of 2003. Methods A regional sample of 1,400 former CAP patients, whose treatment occurred between 1975 and 1990, was followed to 2003, using database-record links to the Register of Persons Convicted of Offences at the National Council for Crime Prevention (NCCP). Results Every third CAP patient treated between 1975 and 1990 (every second man and every fifth woman) had entered the Register of Persons Convicted of Offences during the observation period, which is a significantly higher rate than the general population. Conclusions Results were compared to published results for CAP patients who were treated between 1953 and 1955 and followed over 20 years. Compared to the group of CAP patients from the 1950s, the results indicate that the risk for boys to enter the register for criminality has doubled and for girls, the risk seems to have increased sevenfold. The reasons for this change are discussed. Although hypothetical and perhaps speculative this higher risk of later criminality may be the result of lack of social control due to (1) rising consumption of alcohol, (2) changes in organisation of child social welfare work, (3) the school system, and (4) CAP methods that were implemented since 1970.
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| 19. |
- Engqvist, Ulf, et al.
(författare)
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Hur går det för barn- och ungdomspsykiatrins patienter? : Samverkan krävs mellan pediatrik, barn- och vuxenpsykiatri
- 2000
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Ingår i: Läkartidningen. - 0023-7205. ; 97:23, s. 2856-2861
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Tidskriftsartikel (refereegranskat)abstract
- Under 1990-talet har både den vuxenpsykiatriska och den barn- och ungdomspsykiatriska vården varit föremål för statliga utredningar. Psykiatrireformen som avsåg den vuxenpsykiatriska verksamheten medförde bl.a. ett ökat primärkommunalt ansvar för psykiskt sjuka. När motsvarande utredning kring den barn- och ungdomspsykiatriska vården presenterades 1998, betonades både behovet av förbättrat samarbete mellan vuxen- och barn- och ungdomspsykiatri samt mellan den barn- och ungdomspsykiatriska vården och kommunernas socialtjänst. I en studie vid Östersunds sjukhus genomförd inom ramen för forskarutbildningen vid Karolinska Institutet i Stockholm har barnpsykiatriska patienter beskrivits med särskild hänsyn tagen till samarbetet både med vuxenpsykiatrin och socialtjänsten. Här presenteras data om 1 420 tidigare barn- och ungdomspsykiatriska patienter och deras framtida situation. Observationstiderna varierar mellan 5-20 år och intresset har fokuserats på BUP-patienternas framtida behov av vuxenpsykiatriska hjälpinsatser, deras självmordsrisk och kriminalitetsutveckling. Nästan 2 % har avlidit under observationstiden, huvudsakligen på grund av självmord. Fler än var fjärde patient har sökt kontakt med vuxenpsykiatrin, medan drygt var tredje har kommit i kontakt med kriminalvården. Emellertid utgör de tidigare BUP patienterna bara en mindre del (8 procent) av de aktuella åldersgrupperna inom vuxenpsykiatrin. Resultaten aktualiserar därför frågan om barnpsykiatrins samarbete med barnsjukvården. Kanske måste detta utvidgas än mer, om målet är att tidigt identifiera barn som utvecklar egna psykiatriska besvär och om effektiva preventiva åtgärder ska kunna utvecklas.
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| 20. |
- Engqvist, Ulf, 1951-, et al.
(författare)
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The occurrence and nature of early signs of schizophrenia and psychotic mood disorders among former child and adolescent psychiatric patients followed into adulthood
- 2008
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Ingår i: Child and Adolescent Psychiatry and Mental Health. - England : BioMed Central Ltd. - 1753-2000. ; 2:1, s. 30-
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Tidskriftsartikel (refereegranskat)abstract
- Background This investigation was designed to characterize psychotic disorders among patients originally treated as in- and outpatients by child and adolescent psychiatric services and subsequently followed-up into mid-adulthood. The age at the first onset on symptoms, possible changes in diagnoses, early signs noted prior to or upon admission to child and adolescent psychiatric care and possible differences between patients with early- and later- onset disorder were of particular interest.MethodsThe study population consisted of patients (285 in- and 1115 outpatients) born between 1957 and 1976 and admitted to and treated by child and adolescent psychiatric care units in Jämtland County, Sweden, between 1975 and 1990. The status of their mental health was monitored until 2003 using official registries and hospital records. Diagnoses based on the ICD-8 and -9 systems, which were used in Sweden from 1968-1997, converted to diagnoses according to ICD-10, which has been in use since 1997. The Comprehensive Assessment of at Risk Mental States was employed to assess the information concerning psychopathology provided by the hospital records.ResultsBy the end of the follow-up period 62 former child and adolescent psychiatric patients (36 females and 26 males), 4.4% of the entire study group, had received an ICD-10 diagnosis of "F20-29: Schizophrenia, schizotypal and delusional disorders" (48) and/or "F30-39: Psychotic mood disorders" (14). One-third (21) of these individuals were given their initial diagnosis of psychosis in connection with child and adolescent psychiatric care. Two of these 21 were not treated later for this disorder in general (adult) psychiatric care whereas the remaining 19 individuals were diagnosed for the same type of disorder as adults. The other 41 patients were diagnosed as psychotic only in connection with general (adult) psychiatric care. The mean age at the time of first onset of symptoms was 21.4 years (SD 6.4) and corresponding median age was 18. Behavioural changes and positive symptoms were the most frequent signs associated with a diagnosis of "F20-F29: Schizophrenia, schizotypal and delusional disorders" made during child and adolescent psychiatric care. In cases where a specific psychopathology developed later on the initial admission to child and adolescent psychiatry involved unspecified psychopathology.ConclusionsIn summary, it appears that psychotic disorders are relatively uncommon among patients admitted to child and adolescent psychiatric care in Sweden. However, individuals experiencing early onset of disorders categorized as "F20-29: Schizophrenia, schizotypal and delusional disorders" may already exhibit typical symptoms upon admission to child and adolescent psychiatric care of the age of 13-17; whereas late-onset disorders it appear not be associated with any obvious signs or symptoms years before the disorder has developed fully. Finally, certain cases of psychotic disorder during adolescence seem to have been episodic.
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| 21. |
- Ghajeri, Farnaz, et al.
(författare)
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The Influence of Residuals Combining Temperature and Reaction Time on Calcium Phosphate Transformation in a Precipitation Process
- 2022
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Ingår i: Journal of Functional Biomaterials. - : MDPI. - 2079-4983. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Precipitation is one of the most common processes to synthesize hydroxyapatite, which is the human body’s mineral forming bone and teeth, and the golden bioceramic material for bone repair. Generally, the washing step is important in the precipitation method to remove the residuals in solution and to stabilize the phase transformation. However, the influence of residuals in combination with the reaction temperature and time, on calcium phosphate formation, is not well studied. This could help us with a better understanding of the typical synthesis process. We used a fixed starting ion concentration and pH in our study and did not adjust it during the reaction. XRD, FTIR, ICP-OES, and SEM have been used to analyze the samples. The results showed that combining residuals with both reaction temperature and time can significantly influence calcium phosphate formation and transformation. Dicalcium phosphate dihydrate formation and transformation are sensitive to temperature. Increasing temperature (60◦C) can inhibit the formation of acidic calcium phosphate or transform it to other phases, and further the particle size. It was also observed that high reaction temperature (60◦C) results in higher precipitation efficiency than room temperature. A low ion concentration combining reaction temperature and time could still significantly influence the calcium phosphate transformation during the drying. © 2022 by the authors.
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| 22. |
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| 23. |
- Grandfield, Kathryn, et al.
(författare)
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Bone response to free form fabricated hydroxyapatite and zirconia scaffolds : a transmission electron microscopy study in the human maxilla
- 2012
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Ingår i: Clinical Implant Dentistry and Related Research. - : Wiley. - 1523-0899 .- 1708-8208. ; 14:3, s. 461-469
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Tidskriftsartikel (refereegranskat)abstract
- Background: Understanding the interfacial reactions to synthetic bone regenerative scaffolds in vivo is fundamental for improving osseointegration and osteogenesis. Using transmission electron microscopy, it is possible to study the biological response of hydroxyapatite (HA) and zirconia (ZrO2) scaffolds at the nanometer scale.Purpose: In this study, the bone-bonding abilities of HA and ZrO2 scaffolds produced by free-form fabrication were evaluated in the human maxilla at 3 months and 7 months.Materials and Methods: HA and ZrO2 scaffolds (ø: 3 mm) were implanted in the human maxilla, removed with surrounding bone, embedded in resin, and sectioned. A novel focused ion beam (FIB) sample preparation technique enabled the production of thin lamellae for study by scanning transmission electron microscopy.Results: Interface regions were investigated using high-angle annular dark-field imaging and energy-dispersive X-ray spectroscopy analysis. Interfacial apatite layers of 80 nm and 50 nm thickness were noted in the 3- and 7-month HA samples, respectively, and bone growth was discovered in micropores up to 10 µm into the samples.Conclusions: The absence of an interfacial layer in the ZrO2 samples suggest the formation of a direct contact with bone, while HA, which bonds through an apatite layer, shows indications of resorption with increasing implantation time. This study demonstrates the potential of HA and ZrO2 scaffolds for use as bone regenerative materials.
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| 24. |
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| 25. |
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| 26. |
- Grandfield, Kathryn, et al.
(författare)
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Free form fabricated features on CoCr implants with and without hydroxyapatite coating in vivo : a comparative study of bone contact and bone growth induction
- 2011
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Ingår i: Journal of materials science. Materials in medicine. - : Springer Science and Business Media LLC. - 0957-4530 .- 1573-4838. ; 22:4, s. 899-906
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Tidskriftsartikel (refereegranskat)abstract
- The current study evaluates the in vivo response to free form fabricated cobalt chromium (CoCr) implants with and without hydroxyapatite (HA) plasma sprayed coatings. The free form fabrication method allowed for integration of complicated pyramidal surface structures on the cylindrical implant. Implants were press fit into the tibial metaphysis of nine New Zealand white rabbits. Animals were sacrificed and implants were removed and embedded. Histological analysis, histomorphometry and electron microscopy studies were performed. Focused ion beam was used to prepare thin sections for high-resolution transmission electron microscopy examination. The fabricated features allowed for effective bone in-growth and firm fixation after 6 weeks. Transmission electron microscopy investigations revealed intimate bone-implant integration at the nanometre scale for the HA coated samples. In addition, histomorphometry revealed a significantly higher bone contact on HA coated implants compared to native CoCr implants. It is concluded that free form fabrication in combination with HA coating improves the early fixation in bone under experimental conditions.
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| 27. |
- Grandfield, Kathryn, et al.
(författare)
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High-resolution three-dimensional probes of biomaterials and their interfaces.
- 2012
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Ingår i: Philosophical transactions. Series A, Mathematical, physical, and engineering sciences. - : The Royal Society. - 1364-503X .- 1471-2962. ; 370:1963, s. 1337-51
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Tidskriftsartikel (refereegranskat)abstract
- Interfacial relationships between biomaterials and tissues strongly influence the success of implant materials and their long-term functionality. Owing to the inhomogeneity of biological tissues at an interface, in particular bone tissue, two-dimensional images often lack detail on the interfacial morphological complexity. Furthermore, the increasing use of nanotechnology in the design and production of biomaterials demands characterization techniques on a similar length scale. Electron tomography (ET) can meet these challenges by enabling high-resolution three-dimensional imaging of biomaterial interfaces. In this article, we review the fundamentals of ET and highlight its recent applications in probing the three-dimensional structure of bioceramics and their interfaces, with particular focus on the hydroxyapatite-bone interface, titanium dioxide-bone interface and a mesoporous titania coating for controlled drug release.
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| 28. |
- Grandfield, Kathryn, 1986-
(författare)
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Nanoscale Osseointegration : Characterization of Biomaterials and their Interfaces with Electron Tomography
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bone response is one of the key determining factors in the overall success of biomaterials intended for bone regeneration and osseointegration. Understanding the formation of bone at an implant surface may lead to the improved design of biomaterials for the future. However, due to the inhomogeneity of bone tissue at an interface, two-dimensional images often lack detail on the interfacial complexity. Furthermore, the increasing use of nanotechnology in the design and production of biomaterials demands characterization techniques on a similar nano length scale.While current analysis methods, such as X-ray tomography, transmission electron microscopy, focused ion beam microscopy and scanning electron microscopy, provide a basis for analysing biomaterials and biointerfaces, they are incapable of doing so with both nanometre resolution and three-dimensional clarity. In contrast, electron tomography may be used to characterize the three-dimensional structure of biomaterials and their interfaces to bone with nanometre resolution.In this work, hydroxyapatite scaffolds, and laser-modified titanium and Ti6Al4V implants were studied in contact with human or rabbit bone. Z-contrast electron tomography revealed that the orientation of collagen in bone apposing hydroxyapatite, titanium and Ti6Al4V implants is consistently parallel to the implant surface, where the bioactive layer that precipitates on HA is oriented perpendicular to the implant surface. With this method, complete three-dimensional nanoscale osseointegration of titanium-based implants was also established.The extension of this technique from interfacial analyses to the design of biomaterials provided an understanding of the pore structure of mesoporous titania. In further investigations, the open three-dimensional pore network, as revealed by electron tomography, showed promise as a coating that improves implant osseointegration and enables site-specific drug-delivery from an implant surface.In summary, it was demonstrated that two-dimensional characterization techniques were insufficient for the investigation of nanostructured biomaterials, as well as their interfaces to bone. Visualizing biointerfaces and biomaterials with nanometre precision in three-dimensions can expose new fundamental information on materials properties and bone response, enabling better design of biomaterials for the future.
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| 29. |
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| 30. |
- Grandfield, Kathryn, et al.
(författare)
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Three-dimensional structure of laser-modified Ti6Al4V and bone interface revealed with STEM tomography
- 2011
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Ingår i: Frontiers in Electron Microscopy in Materials Science.
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Konferensbidrag (refereegranskat)abstract
- The Ti6Al4V titanium alloy is one of the most routinely used materials in implant technologies. It is a suitable biomaterial due to its intrinsic mechanical properties, the excellent biocompatibility of its native surface titanium-dioxide layer, and its ability to osseointegrate. The early interaction between an implant’s surface and bone is a leading factor for implant success, where multiple surface properties contribute to improved bone anchorage. An important parameter is surface topography, both on the micron and nanoscale. Laser-modification has been performed in the thread valleys of Ti6Al4V screws to alter their surface chemistry and topography to form a nanostructured surface titanium-dioxide. Since the valley regions are associated with increased bone formation kinetics and influential to implant bonding, the modified screws may exhibit enhanced bone attachment. In order to understand the underlying mechanisms and structure of the interface to nanostructured implant surfaces, characterization techniques with sufficient resolution are needed. Z-contrast electron tomography offers the possibility to explore the interfacial structure with high-resolution in three-dimensions. Furthermore, by operating in STEM mode, artifacts arising from diffraction contrast in the crystalline implant are avoided, while a high-degree of compositional contrast is maintained in the bone matrix. The aim of the present paper was to evaluate Z-contrast electron tomography as a tool to analyze the bone interface to a nanostructured implant surface. Implants were placed in the rabbit tibia and removed with surrounding bone after 8 weeks. Focused ion beam (FIB) was used to prepare specimens for transmission electron microscopy (TEM). Elemental analysis with energy dispersive x-ray spectroscopy (EDXS) over the implant-bone interface confirms the intermixing of bone apatite and titanium dioxide. This was further substantiated with three-dimensional reconstructions created from Z-contrast electron tomograms. Collagen fibers of the surrounding bone appear to have been laid down parallel to the implant surface. Accordingly, visualization of the laser-modified interface with nanoscale three-dimensional resolution, as offered by Z-contrast electron tomography, gives new insights into bone bonding mechanisms between roughened titanium-dioxide surfaces and bone.
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| 31. |
- Grandfield, Kathryn, 1986-, et al.
(författare)
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Three-dimensional structure of laser-modified Ti6Al4V and bone interface revealed with STEM tomography
- 2013
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 127, s. 48-52
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Tidskriftsartikel (refereegranskat)abstract
- The early interaction between an implant's surface and bone is a leading factor for implant success, where multiple surface properties contribute to improved bone anchorage. An important parameter is surface topography, both on the micron and nanoscale. Laser-modification has been performed in the thread valleys of Ti6Al4V screws to alter their surface chemistry and topography to form a nanostructured surface titanium-dioxide. Implants were placed in the rabbit tibia, removed with surrounding bone after 8 weeks, fixated, dried and resin embedded. Focused ion beam milling (FIB) was used to prepare specimens from the resin blocks for transmission electron microscopy (TEM). Z-contrast electron tomography offered the possibility to explore the interfacial structure with high-resolution in three-dimensions. With this technique, collagen fibers of the surrounding bone appear to have been laid down parallel to the implant surface. Accordingly, visualization of the laser-modified interface with nanoscale three-dimensional resolution, as offered by Z-contrast electron tomography, gives new insights into bone bonding mechanisms between roughened titanium-dioxide surfaces and bone.
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| 32. |
- Grandfield, Kathryn, 1986-, et al.
(författare)
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Ultrastructural characterisation of the hydroxyapatite–coated pedicle screw and human bone interface
- 2012
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Ingår i: International Journal of Nano and Biomaterials. - 1752-8933 .- 1752-8941. ; 4:1, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- The early fixation of pedicle screws is crucial for improving spinal stabilisation. Firm and immediate fixation between pedicle screws and bone prevents aseptic loosening and implant failure. Coating with hydroxyapatite is a possible method to improve the fixation of metallic implants in bone. In this study, scanning transmission electron microscopy (STEM) has been used to investigate the ultrastructure of the plasma–sprayed hydroxyapatite coating and human bone interface in detail. Focused ion beam sample preparation also enabled the investigation of the bone–lacunae interface. An intimate contact and elemental analysis between bone and HA coatings suggests bioactive fixation. Therefore, coating with hydroxyapatite leads to enhanced biocompatibility at the ultrastructural level and may lead to improved early and long–term fixation of pedicle screws.
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| 33. |
- Grandfield, Kathryn, et al.
(författare)
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Visualizing biointerfaces in three dimensions : electron tomography of the bone-hydroxyapatite interface
- 2010
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Ingår i: Journal of the Royal Society Interface. - : The Royal Society. - 1742-5689 .- 1742-5662. ; 7:51, s. 1497-501
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Tidskriftsartikel (refereegranskat)abstract
- A positive interaction between human bone tissue and synthetics is crucial for the success of bone-regenerative materials. A greater understanding of the mechanisms governing bone-bonding is often gained via visualization of the bone-implant interface. Interfaces to bone have long been imaged with light, X-rays and electrons. Most of these techniques, however, only provide low-resolution or two-dimensional information. With the advances in modern day transmission electron microscopy, including new hardware and increased software computational speeds, the high-resolution visualization and analysis of three-dimensional structures is possible via electron tomography. We report, for the first time, a three-dimensional reconstruction of the interface between human bone and a hydroxyapatite implant using Z-contrast electron tomography. Viewing this structure in three dimensions enabled us to observe the nanometre differences in the orientation of hydroxyapatite crystals precipitated on the implant surface in vivo versus those in the collagen matrix of bone. Insight into the morphology of biointerfaces is considerably enhanced with three-dimensional techniques. In this regard, electron tomography may revolutionize the approach to high-resolution biointerface characterization.
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| 34. |
- Jarmar, T., et al.
(författare)
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Characterization of the surface properties of commercially available dental implants using scanning electron microscopy, focused ion beam, and high-resolution transmission electron microscopy
- 2008
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Ingår i: Clinical Implant Dentistry and Related Research. - : Wiley. - 1523-0899 .- 1708-8208. ; 10:1, s. 11-22
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Since osseointegration of the respective implant is claimed by all manufacturing companies, it is obvious that not just one specific surface profile including the chemistry controls bone apposition. PURPOSE: The purpose was to identify and separate out a particular set of surface features of the implant surfaces that can contribute as factors in the osseointegration process. MATERIAL AND METHODS: The surface properties of several commercially available dental implants were extensively studied using profilometry, scanning electron microscopy, and transmission electron microscopy. Ultrathin sections prepared with focused ion beam microscopy (FIB) provided microstructural and chemical data which have not previously been communicated. The implants were the Nobel Biocare TiUnite (Nobel Biocare AB, Goteborg, Sweden), Nobel Biocare Steri-Oss HA-coated (Nobel Biocare AB, Yorba Linda, CA, USA), Astra-Tech OsseoSpeed (Astra Tech AB, Molndal, Sweden), Straumann SLA (Straumann AG, Waldenburg, Switzerland), and the Branemark Integration Original Fixture implant (Branemark Integration, Goteborg, Sweden). RESULTS: It was found that their surface properties had differences. The surfaces were covered with crystalline TiO(2) (both anatase and rutile), amorphous titanium oxide, phosphorus doped amorphous titanium oxide, fluorine, titanium hydride, and hydroxyapatite, respectively. CONCLUSION: This indicates that the provision of osseointegration is not exclusively linked to a particular set of surface features if the implant surface character is a major factor in that process. The studied methodology provides an effective tool to also analyze the interface between implant and surrounding bone. This would be a natural next step in understanding the ultrastructure of the interface between bone and implants.
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| 35. |
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| 36. |
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| 37. |
- Jarmar, T., et al.
(författare)
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Technique for preparation and characterization in cross-section of oral titanium implant surfaces using focused ion beam and transmission electron microscopy
- 2008
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Ingår i: Journal of Biomedical Materials Research Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 87:4, s. 1003-9
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Tidskriftsartikel (refereegranskat)abstract
- The surface properties of materials are believed to control most of the biological reactions toward implanted materials. To study the surface structure, elemental distribution, and morphology, using transmission electron microscopy (TEM) techniques, thin foils of the surface (in cross-section) are needed. These have been cumbersome to produce, in particular, from the normally irregular screw-shaped metal implants. Focused ion beam (FIB) microscopy has been developed partly for TEM sample preparation, mainly within the microelectronics industry. Our study describes a method based on FIB for producing electron transparent foils/sections from a metal implant for TEM analysis. Using a screw-shaped titanium dental implant, it was demonstrated that thin foils can be prepared with submicron specificity and from almost any surface geometry. A comparison of different lift-out techniques showed that the in situ lift-out preparation technique allowed plasma cleaning and produced particularly good samples with excellent yield. The titanium oxide on the implant surface was analyzed using energy-filtered TEM (EFTEM) and high-resolution TEM (HRTEM) and the TiO(2) rutile phase being determined via the lattice parameters. This study provides the first set of data for the optimization of a new route for preparation and analysis of biomaterial surfaces and interfaces.
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| 38. |
- Karlsson, Joakim, et al.
(författare)
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Characterization and comparison of materials produced by Electron Beam Melting (EBM) of two different Ti-6Al-4V powder fractions
- 2013
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Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136 .- 1873-4774. ; 213:12, s. 2109-2118
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Tidskriftsartikel (refereegranskat)abstract
- Electron Beam Melting (EBM) has been recognized as a revolutionary technique to produce mass-customized parts to near-net-shape from various metallic materials. The technique produces parts with unique geometries from a powder stock material and uses an electron beam to melt the powder layer-by-layer to fully solid structures. In this study we have investigated the use of two different Ti-6Al-4V powders of different size fractions in the EBM process; a larger 45-100 mu m powder, and a smaller 25-45 mu m powder. We have also investigated the effects of two build layer thicknesses, 70 mu m and 50 mu m. respectively. We hypothesize that the smaller powder has the potential to improve surface resolution of parts produced in the EBM process. The EBM as-built parts were investigated regarding surface and bulk chemistry, surface oxide thickness, macro- and microstructure, surface appearance and mechanical properties. We conclude from the results that both powders and both build layer thicknesses are feasible to use in the EBM process. The investigated material properties were not significantly affected by powder size or layer thickness within the studied range of process parameters. However, the surface appearance was found to be different for the samples made with the different powder sizes.
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| 39. |
- Karlsson, Joakim, 1984-, et al.
(författare)
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Digital image correlation analysis of local strain fields on Ti6Al4V manufactured by electron beam melting
- 2014
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 618, s. 456-461
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Tidskriftsartikel (refereegranskat)abstract
- Additive manufacturing, or 3D-printing as it is often called, build parts in a layer-by-layer fashion. A common concern, regardless of the specific additive manufacturing technique used, is the risk of inadequate fusion between the adjacent layers which in turn may cause inferior mechanical properties. In this work, the local strain properties of titanium parts produced by Electron Beam Melting (EBM®) were studied in order to gain information about the quality of fusion of the stock powder material used in the process. By using Digital Image Correlation (DIC) the strain fields in the individual layers were analyzed, as well as the global strain behavior of the bulk material. The results show that fully solid titanium parts manufactured by EBM are homogenous and do not experience local deformation behavior, neither on local nor on a global level.
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| 40. |
- Karlsson, Joakim, 1984-, et al.
(författare)
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Thickness dependency of mechanical properties for thin-walled titanium parts manufactured by Electron Beam Melting (EBM®)
- 2024
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Ingår i: Additive Manufacturing. - : Elsevier. - 2214-8604 .- 2214-7810.
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Tidskriftsartikel (refereegranskat)abstract
- Metal powder bed additive manufacturing technologies, such as the Electron Beam Melting process, facilitate a high degree of geometric flexibility and have been demonstrated as useful production techniques for metallic parts. However, the EBM process is typically associated with lower resolutions and higher surface roughness compared to similar laser-based powder bed metal processes. In part, this difference is related to the larger powder size distribution and thicker layers normally use As part of an effort to improve the resolution and surface roughness of EBM fabricated components, this study investigates the feasibility of fabricating components with a smaller powder size fraction and layer thickness (similar to laser based processes). The surface morphology, microstructure and tensile properties of the produced samples were evaluated. The findings indicate that microstructure is dependent on wall-thickness and that, for thin walled structures, tensile properties can become dominated by variations in surface roughness.
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| 41. |
- Karlsson, Joakim, 1984-, et al.
(författare)
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Thickness dependency of surface properties for thin-walled titanium parts manufactured by Electron Beam Melting (EBM®)
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Ingår i: Additive Manufacturing. - 2214-8604 .- 2214-7810.
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Tidskriftsartikel (refereegranskat)abstract
- The surface morphology of components produced by powder bed metal additive manufacturing is of interest for multiple industry sectors including biomedical and aerospace. For some applications, improvements in surface finish can reduce or eliminate the requirement for secondary finishing processes. In this study, titanium alloy (Ti6Al4V) samples were manufactured using the Electron Beam Melting (EBM) process. The effect of variations in sample thickness, powder size distribution and layer thickness were measured with three different techniques, both for direct measurement and comparison of the techniques. Ra-values in the range of 15 µm – 37 µm were obtained and varied depending on measurement technique. However, independent of technique, Ra values were found to be dependent on powder size distribution, build layer thickness, and wall thickness. Analytical transmission electron microscopy of cross sections prepared by focused ion beam milling revealed that the outermost surfaces consisted of an oxide layer of 5 nm -6 nm thickness.
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| 42. |
- Kreisel, Katrin, 1991, et al.
(författare)
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DNA polymerase η contributes to genome-wide lagging strand synthesis.
- 2019
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Ingår i: Nucleic acids research. - : Oxford University Press (OUP). - 1362-4962 .- 0305-1048. ; 47:5, s. 2425-2435
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Tidskriftsartikel (refereegranskat)abstract
- DNA polymerase η (pol η) is best known for its ability to bypass UV-induced thymine-thymine (T-T) dimers and other bulky DNA lesions, but pol ηalso has other cellular roles. Here, we present evidence that pol η competes with DNA polymerases α and δfor the synthesis of the lagging strand genome-wide, where it also shows a preference for T-T in the DNA template. Moreover, we found that the C-terminus of pol η,which contains a PCNA-Interacting Protein motif is required for pol ηto function in lagging strand synthesis. Finally, we provide evidence that a pol η dependent signature is also found to be lagging strand specific in patients with skin cancer. Taken together, these findings provide insight into the physiological role of DNA synthesis by pol η and have implications for our understanding of how our genome is replicated to avoid mutagenesis, genome instability and cancer.
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| 43. |
- Kreisel, Katrin, 1991, et al.
(författare)
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Simultaneous mapping and quantitation of ribonucleotides in human mitochondrial DNA
- 2017
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Ingår i: Journal of Visualized Experiments. - : MyJove Corporation. - 1940-087X. ; 2017
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Tidskriftsartikel (refereegranskat)abstract
- © 2017. Established approaches to estimate the number of ribonucleotides present in a genome are limited to the quantitation of incorporated ribonucleotides using short synthetic DNA fragments or plasmids as templates and then extrapolating the results to the whole genome. Alternatively, the number of ribonucleotides present in a genome may be estimated using alkaline gels or Southern blots. More recent in vivo approaches employ Next-generation sequencing allowing genome-wide mapping of ribonucleotides, providing the position and identity of embedded ribonucleotides. However, they do not allow quantitation of the number of ribonucleotides which are incorporated into a genome. Here we describe how to simultaneously map and quantitate the number of ribonucleotides which are incorporated into human mitochondrial DNA in vivo by Next-generation sequencing. We use highly intact DNA and introduce sequence specific double strand breaks by digesting it with an endonuclease, subsequently hydrolyzing incorporated ribonucleotides with alkali. The generated ends are ligated with adapters and these ends are sequenced on a Next-generation sequencing machine. The absolute number of ribonucleotides can be calculated as the number of reads outside the recognition site per average number of reads at the recognition site for the sequence specific endonuclease. This protocol may also be utilized to map and quantitate free nicks in DNA and allows adaption to map other DNA lesions that can be processed to 5´-OH ends or 5´-phosphate ends. Furthermore, this method can be applied to any organism, given that a suitable reference genome is available. This protocol therefore provides an important tool to study DNA replication, 5´-end processing, DNA damage, and DNA repair.
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| 44. |
- Lindahl, Carl, et al.
(författare)
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Biomimetic calcium phosphate coating of additively manufactured porous CoCr implants
- 2015
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 353, s. 40-47
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to study the feasibility to use a biomimetic method to prepare biomimetic hydroxyapatite (HA) coatings on CoCr substrates with short soaking times and to characterize the properties of such coatings. A second objective was to investigate if the coatings could be applied to porous CoCr implants manufactured by electron beam melting (EBM). The coating was prepared by immersing the pretreated CoCr substrates and EBM implants into the phosphate-buffered solution with Ca2+ in sealed plastic bottles, kept at 60 degrees C for 3 days. The formed coating was partially crystalline, slightly calcium deficient and composed of plate-like crystallites forming roundish flowers in the size range of 300-500 nm. Cross-section imaging showed a thickness of 300-500 nm. In addition, dissolution tests in Tris-HCl up to 28 days showed that a substantial amount of the coating had dissolved, however, undergoing only minor morphological changes. A uniform coating was formed within the porous network of the additive manufactured implants having similar thickness and morphology as for the flat samples. In conclusion, the present coating procedure allows coatings to be formed on CoCr and could be used for complex shaped, porous implants made by additive manufacturing.
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| 45. |
- Moren, Lina, et al.
(författare)
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Attribution of fentanyl analogue synthesis routes by multivariate data analysis of orthogonal mass spectral data
- 2019
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Ingår i: Talanta. - : ELSEVIER SCIENCE BV. - 0039-9140 .- 1873-3573. ; 203, s. 122-130
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Tidskriftsartikel (refereegranskat)abstract
- Chemical attribution signatures (CAS) can be used to obtain useful forensic information and evidence from illicit drug seizures. A CAS is typically generated using hyphenated chemical analysis techniques and consists of a fingerprint of the by-products and additives present in a sample. Among other things, it can provide information on the samples origin, its method of production, and the sources of its precursors. This work investigates the possibility of using multivariate CAS analysis to identify the synthetic methods used to prepare seized fentanyl analogues, independently of the analogues acyl derivatization. Three chemists working in two labs synthesized three different fentanyl analogues, preparing each one in duplicate by six different routes. The final collection of analogues (96 samples) and two intermediates (16 + 32 samples) were analysed by GC-MS and UHPLC-HRMS, and the resulting analytical data were used for multivariate modelling. Independently of analogue structure, the tested fentanyls could be classified based on the method used in the first step of their synthesis. The multivariate models ability to classify unknown samples was then evaluated by applying it to six new fentanyl analogues. Additionally, seized fentanyl samples was analysed and classified by the model.
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| 46. |
- Omar, Omar, et al.
(författare)
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In situ bone regeneration of large cranial defects using synthetic ceramic implants with a tailored composition and design
- 2020
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 117:43, s. 26660-26671
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Tidskriftsartikel (refereegranskat)abstract
- The repair of large cranial defects with bone is a major clinical challenge that necessitates novel materials and engineering solutions. Three-dimensionally (3D) printed bioceramic (BioCer) implants consisting of additively manufactured titanium frames enveloped with CaP BioCer or titanium control implants with similar designs were implanted in the ovine skull and at s.c. sites and retrieved after 12 and 3 mo, respectively. Samples were collected for morphological, ultrastructural, and compositional analyses using histology, electron microscopy, and Raman spectroscopy. Here, we show that BioCer implants provide osteoinductive and microarchitectural cues that promote in situ bone regeneration at locations distant from existing host bone, whereas bone regeneration with inert titanium implants was confined to ingrowth from the defect boundaries. The BioCer implant promoted bone regeneration at nonosseous sites, and bone bonding to the implant was demonstrated at the ultrastructural level. BioCer transformed to carbonated apatite in vivo, and the regenerated bone displayed a molecular composition indistinguishable from that of native bone. Proof-of-principle that this approach may represent a shift from mere reconstruction to in situ regeneration was provided by a retrieved human specimen, showing that the BioCer was transformed into well-vascularized osteonal bone, with a morphology, ultrastructure, and composition similar to those of native human skull bone.
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| 47. |
- Palmquist, Anders, 1977, et al.
(författare)
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Biomechanical, Histological and Ultrastructural Analyses of Laser Micro- and Nano-structured Titanium Alloy Implants : A Study in Rabbit
- 2010
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Ingår i: Journal of Biomedical Materials Research - Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 92A:4, s. 1476-1486
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate the biomechanical properties and ultrastructure of the bone response of partly laser-modified Ti6Al4V implants compared with turned, machined implants after 8 weeks in rabbit. The surface analyses performed with interference microscopy and electron microscopy showed increased surface topography with micro- and nano-sized surface features as well as increased oxide thickness of the modified surface. The biomechanical testing demonstrated a 270% increase in torque value for the surface modified implants compared with the control implants. Histological evaluation of ground sections of specimens subjected to biomechanical testing revealed ongoing bone formation and remodeling. A histological feature exclusively observed at the laser-modified surface was the presence of fracture in the mineralized bone rather than at the interface between the bone and implant. Transmission electron microscopy (TEM) was performed on Focused Ion Beam (FIB) prepared samples of the intact bone-implant interface, demonstrating a direct contact between nanocrystalline hydroxyapatite and the oxide of the laser-modified implant surface. In conclusion, laser-modified titanium alloy implants have significantly stronger bone anchorage compared with machined implants and show no adverse tissue reactions.
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| 48. |
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| 49. |
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| 50. |
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