Vivoxid Ltd.

Turku, Finland

Vivoxid Ltd.

Turku, Finland

Time filter

Source Type

Le Bell-Ronnlof A.-M.,University of Turku | Lassila L.V.J.,University of Turku | Kangasniemi I.,Vivoxid Ltd | Vallittu P.K.,University of Turku
Dental Materials | Year: 2011

Objectives: The aim of this study was to evaluate the load-bearing capacity and microstrain of incisors restored with posts of various kinds. Both prefabricated titanium posts and different fiber-reinforced composite posts were tested. Methods: The crowns of human incisors were cut and post preparation was carried out. The roots were divided into groups: (1) prefabricated serrated titanium posts, (2) prefabricated carbon fiber-reinforced composite posts, (3) individually formed glass fiber-reinforced composite posts with the canal full of fibers, and (4) individually formed "split" glass fiber-reinforced composite posts. The posts were cemented and composite crowns were made. Intact human incisors were used as reference. All roots were embedded in acrylic resin cylinders and stored at room temperature in water. Static load was applied under a loading angle of 45° using a universal testing machine. On half of the specimens microstrain was measured with strain gages and an acoustic emission analysis was carried out. Failure mode assessment was also made. Results: The group with titanium posts showed highest number of unfavorable failures compared to the groups with fiber-reinforced composite posts. Significance: With fiber-reinforced composite posts the failures may more often be favorable compared to titanium posts, which clinically means repairable failures. © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.


Varila L.,Åbo Akademi University | Lehtonen T.,Vivoxid Ltd. | Tuominen J.,Vivoxid Ltd. | Hupa M.,Åbo Akademi University | Hupa L.,Åbo Akademi University
Journal of Materials Science: Materials in Medicine | Year: 2012

Poly(L,DL-lactide) composites containing filler particles of bioactive glasses 45S5 and S53P4 were compared with a composite containing a slowly dissolving glass S68. The in vitro reactivity of the composites was studied in simulated body fluid, Tris-buffered solution, and phosphate buffered saline. The high processing temperature induced thermal degradation giving cavities in the composites containing 45S5 and S53P4, while good adhesion of S68 to the polymer was observed. The cavities partly affected the in vitro reactivity of the composites. The degradation of the composites containing the bioactive glasses was faster in phosphate buffered saline than in the two other solutions. Hydroxyapatite precipitation suggesting bone tissue bonding capability was observed on these two composites in all three solutions. The slower dissolution of S68 glass particles and the limited hydroxyapatite precipitation suggested that this glass has potential as a reinforcing composition with the capability to guide bone tissue growth in biodegradable polymer composites. © Springer Science+Business Media, LLC 2012.


Massera J.,Åbo Akademi University | Claireaux C.,Åbo Akademi University | Lehtonen T.,Vivoxid Ltd. | Tuominen J.,Vivoxid Ltd. | And 2 more authors.
Journal of Non-Crystalline Solids | Year: 2011

This work studied the properties of glasses with the molar composition 63.8SiO2-(11.6-x)Na2O-(0.7 + x)B2O 3-19.2CaO-3MgO-1.5Al2O3-0.2P2O 5, in which x = 0, 1, 2, 3. These glasses are of interest for the development of slowly dissolving fibers to be incorporated in composites for medical applications. The thermal properties were recorded using hot stage microscopy, differential thermal analysis, and heat treatments in the range of 800°-1000 °C. The glass crystallization behavior was determined based on calculated values of the activation energy of crystallization and the Johnson-Mehl-Avrami exponent. The structural units in the glass network were identified using infrared spectroscopy. Finally, in vitro dissolution was tested in SBF solution. The addition of B2O3 increased the glass transition temperature and reduced the working temperature. When heat treated at 900 °C, the glass with the smallest amount of B2O3 formed two crystalline phases: magnesium silicate MgSiO3 and wollastonite CaSiO3. In the other compositions, only CaSiO 3 was observed after heat treatment at 950 °C. All the glasses crystallized preferentially from the surface. Changes in the liquidus and crystallization temperatures were related to changes in the glass structure. The formation of [BO3] units led to glasses with improved resistance to crystallization and decreased liquidus temperature. In the glasses with 2.7 and 3.7 mol% B2O3, [BO3] units were transformed into [BO4] units. The formation of [BO4] led to an increase in fragility and a decrease in resistance to crystallization. All the glasses dissolved slowly in simulated body fluid. © 2011 Elsevier B.V. All rights reserved.


Varila L.,Åbo Akademi University | Fagerlund S.,Åbo Akademi University | Lehtonen T.,Vivoxid Ltd | Tuominen J.,Vivoxid Ltd | Hupa L.,Åbo Akademi University
Journal of the European Ceramic Society | Year: 2012

In vitro bioactivity of glasses is usually measured in buffered solutions whereby a formation of a hydroxyapatite layer on the surface is taken as an indication of the bioactivity. In this work we compare the layer formation on three glasses in simulated body fluid, Tris buffer solution, sodium phosphate buffered saline and osteoblast medium. Two of the glasses are known bioactive glasses, 45S5 (45wt.% SiO 2) and S53P4 (53wt.% SiO 2), while the third is an experimental composition with a higher silica content (68wt.% SiO 2). Plates of the glasses were immersed in the solutions at 37°C for different times up to two weeks. The results showed clear differences between the layer developments on the three glasses in the different solutions. The results indicated that the relative order of the reactivity depended on the solution. Thus, results gained in different solutions for different glasses cannot be directly compared. © 2012 Elsevier Ltd.


Lehtonen T.J.,Vivoxid Ltd | Tuominen J.U.,Vivoxid Ltd | Hiekkanen E.,Vivoxid Ltd
Journal of the Mechanical Behavior of Biomedical Materials | Year: 2013

This article describes the dissolution behavior of three silica-based resorbable glasses manufactured by an industrial-type continuous fiber drawing process yielding fibers with tensile strength of 1800-2300. MPa. The results of a long-term in vitro degradation testing of the manufactured high strength bioresorbable glass fibers are presented. The degradation was performed by exposing the glass fibers to SBF and TRIS for 26 weeks at physiological conditions at 37. °C. All fibers showed continuous resorption throughout the study and two of the fibers revealed bioactivity by forming a calcium phosphate (CaP) layer in SBF. © 2013 Elsevier Ltd.


Lehtonen T.J.,Vivoxid Ltd. | Tuominen J.U.,Vivoxid Ltd. | Hiekkanen E.,Vivoxid Ltd.
Acta Biomaterialia | Year: 2013

An in vitro degradation study of three bioresorbable glass fiber-reinforced poly(l-lactide-co-dl-lactide) (PLDLA) composites was carried out in simulated body fluid (SBF), to simulate body conditions, and deionized water, to evaluate the nature of the degradation products. The changes in mechanical and chemical properties were systematically characterized over 52 weeks dissolution time to determine the degradation mechanism and investigate strength retention by the bioresorbable glass fiber-reinforced PLDLA composite. The degradation mechanism was found to be a combination of surface and bulk erosion and does not follow the typical core-accelerated degradation mechanism of poly(α-hydroxyacids) . Strength retention by bioresorbable glass fiber-reinforced PLDLA composites can be tailored by changing the oxide composition of the glass fibers, but the structure-property relationship of the glass fibers has to be understood and controlled so that the phenomenon of ion leaching can be utilized to control the degradation rate. Therefore, these high performance composites are likely to open up several new possibilities for utilizing resorbable materials in clinical applications which could not be realized in the past. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.


PubMed | Vivoxid Ltd.
Type: Journal Article | Journal: Acta biomaterialia | Year: 2012

An in vitro degradation study of three bioresorbable glass fiber-reinforced poly(l-lactide-co-dl-lactide) (PLDLA) composites was carried out in simulated body fluid (SBF), to simulate body conditions, and deionized water, to evaluate the nature of the degradation products. The changes in mechanical and chemical properties were systematically characterized over 52 weeks dissolution time to determine the degradation mechanism and investigate strength retention by the bioresorbable glass fiber-reinforced PLDLA composite. The degradation mechanism was found to be a combination of surface and bulk erosion and does not follow the typical core-accelerated degradation mechanism of poly(-hydroxyacids). Strength retention by bioresorbable glass fiber-reinforced PLDLA composites can be tailored by changing the oxide composition of the glass fibers, but the structure-property relationship of the glass fibers has to be understood and controlled so that the phenomenon of ion leaching can be utilized to control the degradation rate. Therefore, these high performance composites are likely to open up several new possibilities for utilizing resorbable materials in clinical applications which could not be realized in the past.

Loading Vivoxid Ltd. collaborators
Loading Vivoxid Ltd. collaborators