Osteoblast proliferation and maturation on bioactive fiber-reinforced composite surface

Strength and bioactivity of PEEK composites containing multiwalled carbon nanotubes and bioactive glass

Polyetheretherketone (PEEK) polymer is a widely accepted implantable biomaterial in the biomedical field. However, PEEK has a low elastic modulus (E-modulus) as well as a bio-inert nature which is not conductive to rapid bone cell attachment, hence, producing delayed or weak bone-implant integration. Multiwalled carbon nanotubes (MWCNTs) represent one of the strongest known materials that could be added to a polymer to improve its mechanical properties. Bioactive glasses (BGs) can form hydroxyapatite deposits on their surfaces and form a tight bond with the bone, thus, their incorporation into the PEEK matrix may improve its bioactivity.

METHODS

Eight groups were formulated according to the type and percentage of modification of PEEK by MWCNTs and BGs. Group 1: Pure PEEK (P), Group 2: P + 3% MWCNTs (PC3), Group 3: P + 5% MWCNTs (PC5), Group 4: P + 5% BGs (PG5), Group 5: P + 10% BGs (PG10), Group 6: P + 3% MWCNTs + 5% BGs (PC3G5), Group 7: P + 3% MWCNTs + 10% BGs (PC3G10), and Group 8: P + 5% MWCNTs + 5% BGs (PC5G5). Characterization of the vacuum-pressed PEEK and PEEK composite specimens was done using FE-SEM, EDS, FT-IR and TF-XRD. Three-point load test was done to obtain the flexural strength (F.S) and the E-modulus of the specimens. Wettability was determined by measuring the contact angle with distilled water. In-vitro bioactivity was determined after immersion of specimens in simulated body fluid (SBF). Moreover, the effect of the specimens on osteoblastic cell viability was evaluated.

RESULTS

Three-point load test results have shown an improvement in both F.S. and E-modulus for groups PC5, PC3G5 and PC5G5. The lowest contact angle was obtained for group PC5G5 followed by the PC3G10 group. All specimens containing BGs showed the formation of hydroxyapatite-like deposits after their immersion in SBF, as well as an improvement in osteoblastic cell viability compared to PEEK.

CONCLUSION

PC3G10, PC3G5 and PG10, groups are promising for the fabrication of patient-specific implants that can be used in low-stress-bearing areas.

Biocompatibility of fiber-reinforced composite (FRC) and woven-coated FRC: an in vivo study

OBJECTIVES

To investigate biocompatibility and bone contact area of FRC and woven-coated FRC (FRC-C) in rats.

MATERIALS AND METHODS

Sixty rats were allocated to three groups: FRC (n=20), FRC-C (n=20), and control group (n=20). Subgroups were determined as 4th (n=10) and 12th weeks (n=10). The specimens were placed in the femur of rats. In the control group, the bone defects were left empty and sutured. Four and 12 weeks after implantation, the rats were sacrificed. Histopathological examinations were performed in a semi-quantitative manner. Twenty rats (n=20) were used for scanning electron microscopy (SEM) examination. Bone contact surfaces were calculated in SEM analysis. A chi-square test was performed to analyze the data.

RESULTS

No statistical difference was detected between the 4th and 12th weeks in the quality of bone union. Quality of bone union was lower in FRC compared to the control group in the 4th week (p=0.012) and the 12th week (p=0.017). The periosteal reaction at the 12th week was lower in FRC than in the control group (p=0.021). Bone contact of FRC and FRC-C was 85.5% and 86.3%, respectively.

CONCLUSIONS

FRC and FRC-C were biocompatible and showed no inflammation. The woven coating did not increase the quality of bone union and bone contact area, while not reducing biocompatibility.

CLINICAL RELEVANCE

The biocompatibility and good bone response of the woven glass fiber net were demonstrated to have the potential as a scaffold for the augmentation of alveolar bone deficiencies and the reconstruction of maxillofacial defects.

The biocompatibility of glass-fibre reinforced composites (GFRCs) - a systematic review

Purpose Fiber-reinforced composites (FRCs) have received considerable attention, owing to their potential use in dental prostheses or bone fracture fixation applications. The aim of this systematic review was to analyze and report the biological properties of FRCs reported in the existing literature.Study selections A systematic search of four databases (PubMed/MEDLINE, Scopus, Web of Science, and Cochrane library) was performed to identify all relevant studies published between 1962 and 2019. The search was limited to laboratory-based studies published in English. Citation mining was also performed through cross-referencing of included studies and hand searching of relevant journals.Results A total of 1283 potentially relevant articles were initially identified, and thirty-three articles were full-text screened. In the final ten studies included for review, four investigated bacterial adhesion and growth abilities on FRCs, four investigated the fibroblastic cytotoxicity of different surface-treated FRCs, and two investigated the osseointegration between bone and FRCs. Owing to the heterogeneity of fiber types, FRC-coating, and lack of standardized testing protocols, a meta-analysis was not feasible. The included studies indicated that glass fibers, and in particular E-glass fibers, are superior to ceramics and other FRCs in terms of bacterial adherence, fibroblast cytotoxicity, and cell viability.Conclusions Glass-fiber-reinforced composites are cytocompatible materials that possess satisfactory biological properties and can be used in dental prosthesis and craniofacial implants. Further research is necessary to regulate the matrix ion release/degradation of FRCs to prolong the initially demonstrated properties.

The biocompatibility of glass-fibre reinforced composites (GFRCs) - a systematic review

PURPOSE

Fiber-reinforced composites (FRCs) have received considerable attention, owing to their potential use in dental prostheses or bone fracture fixation applications. The aim of this systematic review was to analyze and report the biological properties of FRCs reported in the existing literature.

STUDY SELECTIONS

A systematic search of four databases (PubMed/MEDLINE, Scopus, Web of Science, and Cochrane library) was performed to identify all relevant studies published between 1962 and 2019. The search was limited to laboratory-based studies published in English. Citation mining was also performed through cross-referencing of included studies and hand searching of relevant journals.

RESULTS

A total of 1283 potentially relevant articles were initially identified, and thirty-three articles were full-text screened. In the final ten studies included for review, four investigated bacterial adhesion and growth abilities on FRCs, four investigated the fibroblastic cytotoxicity of different surface-treated FRCs, and two investigated the osseointegration between bone and FRCs. Owing to the heterogeneity of fiber types, FRC-coating, and lack of standardized testing protocols, a meta-analysis was not feasible. The included studies indicated that glass fibers, and in particular E-glass fibers, are superior to ceramics and other FRCs in terms of bacterial adherence, fibroblast cytotoxicity, and cell viability.

CONCLUSIONS

Glass-fiber-reinforced composites are cytocompatible materials that possess satisfactory biological properties and can be used in dental prosthesis and craniofacial implants. Further research is necessary to regulate the matrix ion release/degradation of FRCs to prolong the initially demonstrated properties.

Biomechanical and biological evaluations of novel BPA-free fibre-reinforced composites for biomedical applications

This aim was to assess the biomechanical and biocompatibility properties of novel glass fibre-reinforced composites (FRCs) with a fluorinated urethane dimethacrylate (FUDMA) resin. Three ratios of FUDMA/TEGDMA (30/70 wt%, 50/50 wt%, 70/30 wt%) and two ratios of control FRCs with bis-GMA/TEGDMA (50/50 wt% and 70/30 wt%) containing long silanized E-glass fibres were prepared. Despite 70 wt% bis-GMA-FRC showed a significantly higher flexural strength (p < 0.05), 50 wt% FUDMA- and bis-GMA-FRCs were not differ from each other. The greatest surface hardness and weight increase after water storage were found in 70 wt% and 30 wt% FUDMA-FRCs, respectively. No significant difference was found in water sorption and solubility among all groups. Average surface roughness was 1.80 ± 0.05 μm, while 70 wt% FUDMA-FRC exhibited the greatest contact angle (p > 0.05). Viabilities and ALP activities of MC3TC-E1 cells in all FUDMA-FRCs were higher than bis-GMA-FRCs after 5 days. To conclude, the novel FUDMA-FRCs are potential substitutes that exhibited superior cytocompatibility properties but comparable biomechanical properties to bis-GMA-FRCs.

Biomaterial and implant induced ossification: in vitro and in vivo findings

Material-induced ossification is suggested as a suitable approach to heal large bone defects. Fiber-reinforced composite-bioactive glasses (FRC-BGs) display properties that could enhance the ossification of calvarial defects. Here, we analyzed the healing processes of a FRC-BG implant in vivo from the perspective of material-induced ossification. Histological analysis of the implant, which was removed 5 months after insertion, showed the formation of viable, noninflammatory mesenchymal tissue with newly-formed mineralized woven bone, as well as nonmineralized connective tissue with capillaries and larger blood vessels. The presence of osteocytes was detected within the newly generated bone matrix. To expand our understanding on the osteogenic properties of FRC-BG, we cultured human adipose tissue-derived mesenchymal stromal cells (AD-MSCs) in the presence of two different BGs (45S5 and S53P4) and Al2 O3 control. AD-MSCs grew and proliferated on all the scaffolds tested, as well as secreted abundant extracellular matrix, when osteogenic differentiation was appropriately stimulated. 45S5 and S53P4 induced enhanced expression of COL2A1, COL10A1, COL5A1 collagen subunits, and pro-osteogenic genes BMP2 and BMP4. The concomitant downregulation of BMP3 was also detected. Our findings show that FRC-BG can support the vascularization of the implant and the formation of abundant connective tissue in vivo. Specifically, BG 45S5 and BG S53P4 are suited to evoke the osteogenic potential of host mesenchymal stromal cells. In conclusion, FRC-BG implant demonstrated material-induced ossification both in vitro and in vivo.

An overview of development and status of fiber-reinforced composites as dental and medical biomaterials

Fibr-reinforced composites (FRC) have been used successfully for decades in many fields of science and engineering applications. Benefits of FRCs relate to physical properties of FRCs and versatile production methods, which can be utilized. Conventional hand lamination of prefabricated FRC prepregs is utilized still most commonly in fabrication of dental FRC devices but CAD-CAM systems are to be come for use in certain production steps of dental constructions and medical FRC implants. Although metals, ceramics and particulate filler resin composites have successfully been used as dental and medical biomaterials for decades, devices made out of these materials do not meet all clinical requirements. Only little attention has been paid to FRCs as dental materials and majority of the research in dental field has been focusing on particulate filler resin composites and in medical biomaterial research to biodegradable polymers. This is paradoxical because FRCs can potentially resolve many of the problems related to traditional isotropic dental and medical materials. This overview reviews the rationale and status of using biostable glass FRC in applications from restorative and prosthetic dentistry to cranial surgery. The overview highlights also the critical material based factors and clinical requirement for the succesfull use of FRCs in dental reconstructions.

Evaluation of intensity of artefacts in CBCT by radio-opacity of composite simulation models of implants in vitro

OBJECTIVES

The aim was to compare the intensity of artefacts in CBCT images caused by different percentages of radio-opacifying material in composite simulation models of implants. Titanium and zirconia models of implants were used as a reference for the evaluation of the intensity of artefacts.

METHODS

Seven different percentages of radio-opacifying BaAlSiO2 fillers were added to composite resin to fabricate seven step wedges and simulation models of implants. Titanium and zirconia simulation models of implants were also fabricated. Aluminium step wedge was used as a reference for the measurement of grey values in intraoral radiographs. Step wedges were exposed with a Planmeca Intra X-ray machine (Planmeca Oy, Helsinki, Finland). All composite, titanium and zirconia simulation models of implants were exposed with a SCANORA(®) 3D dental X-ray machine (Soredex, Tuusula, Finland). Images and grey values were analysed with ImageJ software (National Institutes of Health, Bethesda, MD). To demonstrate possible artefacts between all the simulation models of implants, the images were also visually compared with each other using ImageJ software.

RESULTS

Artefacts were clearly present in CBCT images caused by titanium and zirconia and when the composite material consisted at least 20% BaAlSiO2. The intensity of artefacts increased when the radio-opacity of the composite material increased.

CONCLUSIONS

Materials containing less radio-opacity produce less pronounced artefacts. The cut-off point for artefacts is at 20% radio-opaque filling material in composite material.

Osseointegration of fiber-reinforced composite implants: histological and ultrastructural observations

OBJECTIVES

The aim of this study was to evaluate the bone tissue response to fiber-reinforced composite (FRC) in comparison with titanium (Ti) implants after 12 weeks of implantation in cancellous bone using histomorphometric and ultrastructural analysis.

MATERIALS AND METHODS

Thirty grit-blasted cylindrical FRC implants with BisGMA-TEGDMA polymer matrix were fabricated and divided into three groups: (1) 60s light-cured FRC (FRC-L group), (2) 24h polymerized FRC (FRC group), and (3) bioactive glass FRC (FRC-BAG group). Titanium implants were used as a control group. The surface analyses were performed with scanning electron microscopy and 3D SEM. The bone-implant contact (BIC) and bone area (BA) were determined using histomorphometry and SEM. Transmission electron microscopy (TEM) was performed on Focused Ion Beam prepared samples of the intact bone-implant interface.

RESULTS

The FRC, FRC-BAG and Ti implants were integrated into host bone. In contrast, FRC-L implants had a consistent fibrous capsule around the circumference of the entire implant separating the implant from direct bone contact. The highest values of BIC were obtained with FRC-BAG (58±11%) and Ti implants (54±13%), followed by FRC implants (48±10%), but no significant differences in BIC or BA were observed (p=0.07, p=0.06, respectively). TEM images showed a direct contact between nanocrystalline hydroxyapatite of bone and both FRC and FRC-BAG surfaces.

CONCLUSION

Fiber-reinforced composite implants are capable of establishing a close bone contact comparable with the osseointegration of titanium implants having similar surface roughness.

Cytotoxicity of coated and uncoated fibre-reinforced composites

OBJECTIVE

Currently, there are many fibre-reinforced composites (FRCs) available which differ in the type and volume fraction of fibres, pre-treatment of fibres and matrix composition. The aims of this in vitro investigation were to determine whether there is a difference in biocompatibility of FRCs and if coating FRCs with resin composites influences their cytotoxic potential.

MATERIALS AND METHODS

Five different FRC materials were tested which were either uncoated or coated with flowable or viscous resin composite. Artificial saliva extracts were prepared according to USP-XXIII and ISO-10993 to determine cytotoxicity by testing cell viability and growth of primary human gingival fibroblasts (HGF) using MTT assay, LIVE/DEAD(®) assay and cell proliferation assay. The influence of eluates on fibres of the cytoskeleton was investigated by vimentin, tubulin and actinin immunostainings. A two-way ANOVA followed by Scheffe's post-hoc test, which included the factors FRC material and coating procedure, was performed to assess cytotoxicity.

RESULTS

All extracts of FRC materials displayed minor cytotoxic potential on HGF cell viability, cell proliferation and integrity of the cytoskeleton. The type of FRC material significantly influenced cell viability (MTT assay) (p < 0.0001), whereas neither the presence of a coating nor the type of coating material resulted in altered cell viability. Distribution and organization of cytosolic fibres was not affected after HGF exposure to eluates.

CONCLUSIONS

There is a lack of knowledge about the leaching behaviour of commonly available fully pre-impregnated FRCs and their interactions with coating materials. The coating of FRCs with resin composite materials did not impact biocompatibility.

Biological responses of human gingival fibroblasts (HGFs) in an innovative co-culture model with Streptococcus mitis to thermosets coated with a silver polysaccharide antimicrobial system

This study sought to evaluate the in vitro biological response of human gingival fibroblasts (HGFs) co-coltured with Streptococcus mitis to bisphenol A glycidylmethacrylate/triethylene glycol dimethacrylate (BisGMA/TEGDMA) thermosets coated with Chitlac-nAg, a nanocomposite system with antimicrobial properties. To avoid bacterial adhesion to dental devices and to reduce cytotoxicity against eukaryotic cells, we coated BisGMA/TEGDMA methacrylic thermosets with a new material, Chitlac-nAg, formed by stabilizing silver nanoparticles, which have well-known antimicrobial properties, with a polyelectrolyte solution containing Chitlac. Cytotoxicity, cell morphology, cell migration and inflammatory interleukine-6 (IL-6) and prostaglandin E2 (PGE2) secretion were evaluated. Our results showed that the cytotoxicity exerted on HGFs by our nanocomposite material was absent in our co-culture model, where fibroblasts are able to adhere and migrate. After 24 h thermosets coated with Chitlac as well as those coated with Chitlac-nAg exerted a minimal cytotoxic effect on HGFs, while after 48 h LDH release rises up 20%. Moreover the presence of S. mitis reduced this release in a greater amount with Chitlac-nAg coated thermosets. The secretion of IL-6 was significant in both Chitlac and Chitlac-nAg coated thermosets, but PGE2 production was minimal, suggesting that the IL-6 production was not related to an inflammatory response. Co-culture and the addiction of saliva did not influence IL-6 and PGE2 secretion. Data obtained in the present work suggest that Chitlac n-Ag coated thermosets could significantly improve the success rates of restorative dentistry, since they limit bacterial adhesion and are not toxic to HGFs.

Bioactive glass particulate filler composite: Effect of coupling of fillers and filler loading on some physical properties

OBJECTIVES

The aim of this study was to investigate the effect of silanization of biostable and bioactive glass fillers in a polymer matrix on some of the physical properties of the composite.

METHODS

The water absorption, solubility, flexural strength, flexural modulus and toughness of different particulate filler composite resins were studied in vitro. Five different specimen groups were analyzed: A glass-free control, a non-silanized bioactive glass, a silanized bioactive glass, a non-silanized biostable glass and a silanized biostable glass groups. All of these five groups were further divided into sub-groups of dry and water-stored materials, both of them containing groups with 3wt%, 6wt%, 9wt% or 12wt% of glass particles (n=8 per group). The silanization of the glass particles was carried out with 2% of gamma-3-methacryloxyproyltrimethoxysilane (MPS). For the water absorption and solubility tests, the test specimens were stored in water for 60 days, and the percentages of weight change were statistically analyzed. Flexural strength, flexural modulus and toughness values were tested with a three-point bending test and statistically analyzed.

RESULTS

Higher solubility values were observed in non-silanized glass in proportion to the percentage of glass particles. Silanization, on the other hand, decreased the solubility values of both types of glass particles and polymer. While 12wt% non-silanized bioactive glass specimens showed -0.98wt% solubility, 12wt% silanized biostable glass specimens were observed to have only -0.34wt% solubility. The three-point bending results of the dry specimens showed that flexural strength, toughness and flexural modulus decreased in proportion to the increase of glass fillers. The control group presented the highest results (106.6MPa for flexural strength, 335.7kPA for toughness, 3.23GPa for flexural modulus), whereas for flexural strength and toughness, 12wt% of non-silanized biostable glass filler groups presented the lowest (70.3MPa for flexural strength, 111.5kPa for toughness). For flexural modulus on the other hand, 12wt% of silanized biostable glass filler group gave the lowest results (2.57GPa).

SIGNIFICANCE

The silanization of glass fillers improved the properties of the glass as well as the properties of the composite. Silanization of bioactive glass may protect the glass from leaching at early stage of water storage.

Multi-layer porous fiber-reinforced composites for implants: in vitro calcium phosphate formation in the presence of bioactive glass

OBJECTIVES

Glass-fiber-reinforced composites (FRCs), based on bifunctional methacrylate resin, have recently shown their potential for use as durable cranioplasty, orthopedic and oral implants. In this study we suggest a multi-component sandwich implant structure with (i) outer layers out of porous FRC, which interface the cortical bone, and (ii) inner layers encompassing bioactive glass granules, which interface with the cancellous bone.

METHODS

The capability of Bioglass(®) 45S5 granules (100-250μm) to induce calcium phosphate formation on the surface of the FRC was explored by immersing the porous FRC-Bioglass laminates in simulated body fluid (SBF) for up to 28d.

RESULTS

In both static (agitated) and dynamic conditions, bioactive glass granules induced precipitation of calcium phosphate at the laminate surfaces as confirmed by scanning electron microscopy.

SIGNIFICANCE

The proposed dynamic flow system is useful for the in vitro simulation of bone-like apatite formation on various new porous implant designs containing bioactive glass and implant material degradation.

The effect of exposed glass fibers and particles of bioactive glass on the surface wettability of composite implants

Measurement of the wettability of a material is a predictive index of cytocompatibility. This study was designed to evaluate the effect of exposed E-glass fibers and bioactive glass (BAG) particles on the surface wettability behavior of composite implants. Two different groups were investigated: (a) fiber reinforced composites (FRCs) with different fiber orientations and (b) polymer composites with different wt. % of BAG particles. Photopolymerized and heat postpolymerized composite substrates were made for both groups. The surface wettability, topography, and roughness were analyzed. Equilibrium contact angles were measured using the sessile drop method. Three liquids were used as a probe for surface free energy (SFE) calculations. SFE values were calculated from contact angles obtained on smooth surfaces. The surface with transverse distribution of fibers showed higher (P < 0.001) polar (γ^P) and total SFE (γ^TOT) components (16.9 and 51.04 mJ/m², resp.) than the surface with in-plane distribution of fibers (13.77 and 48.27 mJ/m², resp.). The increase in BAG particle wt. % increased the polar (γ^P) value, while the dispersive (γ^D) value decreased. Postpolymerization by heat treatment improved the SFE components on all the surfaces investigated (P < 0.001). Composites containing E-glass fibers and BAG particles are hydrophilic materials that show good wettability characteristics.

Stress and Strain Analysis of the Bone-Implant Interface: A Comparison of Fiber-Reinforced Composite and Titanium Implants Utilizing 3-Dimensional Finite Element Study

This study analyzed stress and strain mediated by 2 different implant materials, titanium (Ti) and experimental fiber-reinforced composite (FRC), on the implant and on the bone tissue surrounding the implant. Three-dimensional finite element models constructed from a mandibular bone and an implant were subjected to a load of 50 N in vertical and horizontal directions. Postprocessing files allowed the calculation of stress and strain within the implant materials and stresses at the bone-to-implant interface (stress path). Maximum stress concentrations were located around the implant on the rim of the cortical bone in both implant materials; Ti and overall stresses decreased toward the Ti implant apex. In the FRC implant, a stress value of 0.6 to 2.0 MPa was detected not only on the screw threads but also on the implant surface between the threads. Clear differences were observed in the strain distribution between the materials. Based on the results, the vertical load stress range of the FRC implant was close to the stress level for optimal bone growth. Furthermore, the stress at the bone around the FRC implant was more evenly distributed than that with Ti implant.

Silver-polysaccharide nanocomposite antimicrobial coatings for methacrylic thermosets

Bisphenol A glycidylmethacrylate (BisGMA)/triethyleneglycol dimethacrylate (TEGDMA) thermosets are receiving increasing attention as biomaterials for dental and orthopedic applications; for both these fields, bacterial adhesion to the surface of the implant represents a major issue for the outcome of the surgical procedure. Moreover, the biological behaviour of these materials is influenced by their ability to establish proper interactions between their surface and the eukaryotic cells of the surrounding tissues, which is important for good implant integration. The aim of this work was to develop an antimicrobial non-cytotoxic coating for methacrylic thermosets by means of a nanocomposite material based on a lactose-modified chitosan and antibacterial silver nanoparticles. The coating was characterized by UV-vis spectrophotometry, optical microscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). In vitro tests were employed for a biological characterization of the material: antimicrobial efficacy tests were carried out with both Gram+ and Gram- strains. Osteoblast-like cell-lines, primary human fibroblasts and adipose-derived stem cells, were used for LDH cytotoxicity assays and Alamar blue cell proliferation assays. Cell morphology and distribution were evaluated by SEM and confocal laser scanning microscopy. In vitro results showed that the nanocomposite coating is effective in killing both bacterial strains and that this material does not exert any significant cytotoxic effect towards tested cells, which are able to firmly attach and proliferate on the surface of the coating. Such biocompatible antimicrobial polymeric films containing silver nanoparticles may have good potential for surface modification of medical devices, especially for prosthetic applications in orthopedics and dentistry.

Prepolymerized vs. in situ-polymerized Fiber-reinforced Composite Implants – a Pilot Study

The aim of this study was to investigate bone response to bioactive fiber-reinforced composite (FRC) implants under two polymerization conditions. Glass-fiber-dimethacrylate composite was tested as prepolymerized cylinder-shaped FRC implants and as cylindrical FRC implants polymerized in situ with blue light transmitted and scattered by the glass fibers. Ten FRC implants (6 prepolymerized and 4 in situ-polymerized implants) were placed in the right tibias of 3 pigs by means of a press-fit technique. After 12 weeks, light microscopy revealed only mild foreign-body reaction, with no accumulation of inflammatory cells on both the prepolymerized and the in situ-polymerized implants. The prepolymerized implants appeared to be fully integrated, whereas the in situ-polymerized implants were almost completely surrounded by a fibrous capsule. The present study suggests that in situ polymerization of FRC implants results in fibrous capsule formation and prevents integration with bone.

Effects of heat treatment of wood on hydroxylapatite type mineral precipitation and biomechanical properties in vitro

Wood is a natural fiber reinforced composite. It structurally resembles bone tissue to some extent. Specially heat-treated birch wood has been used as a model material for further development of synthetic fiber reinforced composites (FRC) for medical and dental use. In previous studies it has been shown, that heat treatment has a positive effect on the osteoconductivity of an implanted wood. In this study the effects of two different heat treatment temperatures (140 and 200 degrees C) on wood were studied in vitro. Untreated wood was used as a control material. Heat treatment induced biomechanical changes were studied with flexural and compressive tests on dry birch wood as well as on wood after 63 days of simulated body fluid (SBF) immersion. Dimensional changes, SBF sorption and hydroxylapatite type mineral formation were also assessed. The results showed that SBF immersion decreases the biomechanical performance of wood and that the heat treatment diminishes the effect of SBF immersion on biomechanical properties. With scanning electron microscopy and energy dispersive X-ray analysis it was shown that hydroxylapatite type mineral precipitation formed on the 200 degrees C heat-treated wood. An increased weight gain of the same material during SBF immersion supported this finding. The results of this study give more detailed insight of the biologically relevant changes that heat treatment induces in wood material. Furthermore the findings in this study are in line with previous in vivo studies.