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This study prepared low-toxicity, elemental-releasing resin-modified glass ionomer cements (RMGICs). The effect of 2-hydroxyethyl methacrylate (HEMA, 0 or 5 wt%) and Sr/F-bioactive glass nanoparticles (Sr/F-BGNPs, 5 or 10 wt%) on chemical/mechanical properties and cytotoxicity were examined. Commercial RMGIC (Vitrebond, VB) and calcium silicate cement (Theracal LC, TC) were used as comparisons. Adding HEMA and increasing Sr/F-BGNPs concentration decreased monomer conversion and enhanced elemental release but without significant effect on cytotoxicity. Rising Sr/F-BGNPs reduced the strength of the materials. The degree of monomer conversion of VB (96%) was much higher than that of the experimental RMGICs (21–51%) and TC (28%). The highest biaxial flexural strength of experimental materials (31 MPa) was significantly lower than VB (46 MPa) (p < 0.01) but higher than TC (24 MPa). The RMGICs with 5 wt% HEMA showed higher cumulative fluoride release (137 ppm) than VB (88 ppm) (p < 0.01). Unlike VB, all experimental RMGICs showed Ca, P, and Sr release. Cell viability in the presence of extracts from experimental RMGICs (89–98%) and TC (93%) was significantly higher than for VB (4%). Experimental RMGICs showed desirable physical/mechanical properties with lower toxicity than the commercial material.

The fabrication of ceramic using additive manufacturing has been a promising technique thanks to its abilities to form complex structures and customized shapes as well as to reduce wastes in comparison with conventional methods. Concerning the lithography-based technique, its limitation includes the deterioration of large-sized parts in fabrication process owing to the excessive amount of vaporized pressure caused by debinding of polymeric binder in ceramic slurries. Besides, the binder jetting technique involves more complexities due to the powder modification in preparation for the solidification by water-based binder. Photosensitive binder jetting techniques fabricate ceramic parts using an inkjet system to deposit photo-curable polymers onto ceramic powder bed with the shape of the parts. The binder is polymerized by the ultraviolet light to entrap the ceramic powder and form the three-dimensional object. The heat treatment process is then applied to remove the binder and sinter the part. In this research, the shrinkage, density, porosity, microstructures, mechanical properties, and printing patterns of ceramic alumina fabricated by the photosensitive binder jetting technique were investigated. The results reveal that the full printing sample exhibited the shrinkage of 11 %, the density of 39 %, the flexural strength of 1.04 MPa and the compressive strength of 1.78 MPa, whereas the checkerboard-patterned sample with 50 % reduction of printing area exhibited the density of 33 %, the flexural strength of 0.42 MPa and the compressive strength of 0.72 MPa. Through the medium of checkerboard-patterned printing with 50 % of binder’s quantity at core areas, this technique enables crack minimization in the fabrication of the large-sized part (60 mm in diameter and 30 mm in height). Furthermore, the additional modifications of ceramic powder are not required.

Foot orthoses are commonly used as a noninvasive treatment to relieve foot pain. The custom full-length insoles with various materials and designs have been studied for their effectiveness in reducing plantar pressure. However, few studies have been conducted with respect to custom medial arch support on the relationships between material hardness and measured plantar pressure and level of comfort.To evaluate the effects of the hardness of custom medial arch supports on plantar pressure and comfort perception.Randomized crossover study.Two custom silicone medial arch supports of varying hardness (A and B) were fabricated using 3D printing technology and tested in 12 healthy volunteers against a commercially prefabricated arch support (C). The volunteers wore three medial arch supports in a random order, one month for each arch support with 3-4 days of washout period before wearing the next one. The plantar pressure was measured and analyzed according to each foot zone: forefoot, midfoot, and hindfoot, comparing before intervention, immediately after intervention, and 1 month after intervention. The comfort perception was assessed by collecting volunteer feedback with a questionnaire after using each medial arch support.After 1-month intervention, both 3D-printed and prefabricated medial arch supports demonstrated significantly higher average pressure in the midfoot (P0.001), whereas significantly lower average pressure in the forefoot (P0.001) and hindfoot (P = 0.014, 0.026, and 0.018 for A, B, and C, respectively), compared with those before intervention. There were no significant differences in plantar pressure distribution between the 3D-printed and prefabricated medial arch supports. However, the 3D-printed medial arch supports resulted in better comfort than the prefabricated arch support.The material hardness had no apparent effect on plantar pressure distribution. The three medial arch supports showed reducing plantar heel pressure. Further research is needed to investigate the potential effect of 3D-printed silicone medial arch supports on reducing foot pain in patients.

Several processes have been used to produce polylactide for bone replacement. The challenge remains, however, to produce these devices by a simpler and more economical process. In this study, a method of combining powder and liquid parts was introduced. Star-shaped polylactides with molecular weights ranging from 3 to 16 kg/mol were synthesized and blended with a linear polylactide (Mw = 188 kg/mol) using the technique of emulsion solvent evaporation. The blends in a form of spherical powder were characterized by scanning electron microscopy, gel permeation chromatography, and particle size analysis. The heat-curing polylactide was fabricated by mixing the powder with triethylene glycol dimethacrylate, molded, and then heated in a hot water bath to solidify. The effects of powder composition in terms of amount and molecular weight of the star-shaped polylactide on mechanical properties were investigated. The results showed an increase in flexural strength with increase in the amount of star-shaped polylactide. The powder comprised star-shaped polylactide having the molecular weight of 10,770 g/mol, not less than 80wt%, offered the fabricated heat-curing polylactide with high strength ranging from 95 to 100 MPa. This formulation was further incorporated with hydroxyapatite to improve biocompatibility and subjected to degradation at 37°C. Mechanical test and weight loss determination together with biological test were conducted at certain times during degradation of the materials. Both materials with and without hydroxyapatite showed mechanical stability upon degradation for at least 6 months, but the one with hydroxyapatite revealed significantly better bioactivity at the end of 1-year follow-up study, making it the most promising material for bone implants.

Polymeric cement based on poly (methyl methacrylate) (PMMA) has been known as a common material for fixation of prostheses with the advantages of mechanical properties. However, one of drawbacks of PMMA cement is heat produced during polymerization. The elevating temperature during polymerization resulting from exothermic polymerization of MMA can cause bone cellular necrosis. Additionally, the residual MMA monomer after polymerization is an issue regarding the biocompatibility of cement. In this study, a resorbable cement based on polylactide (PLA) has been developed. Its physical, mechanical and biological properties were investigated as an alternative biocompatible bone cement. The dual-cured polylactide cements prepared by combining spherical powder of star-shaped and linear PLA blends with triethylene glycol dimethacrylate liquid were radically polymerized by UV-VIS light and self-curing methods. Flexural strength, maximum temperature during polymerization and biocompatibility via the percentages of cell viability using MTT assay of the dual-cured polylactide were determined to meet requirements for bone cement. The best flexural strength of 108 MPa was achieved from the cement composed of 80%-wt of star-shaped PLA with molecular weight (Mw) of 10770. The preparation of cement using paste/liquid mixing, in which the powder was allowed to wet in the liquid before mixing, significantly encouraged mechanical properties compared to powder/liquid mixing due to satisfactory solubility of PLA prior to polymerization. The amount of initiator/activator was studied to fine-tune the maximum temperature during polymerization. The maximum temperature during polymerization of the PLA cement was in the range of 80-90 degree Celsius and the percentage of osteogenic cell viability immediately after cement setting was 83 indicating a non-toxic material. Therefore, this PLA cement polymerized with a dual curing mode is promising for a resorbable bone cement.

The aim of this study was to prepare RMGICs for pulp protection that contain polyacids functionalized with methacrylate groups (CMs) to enable light-activated polymerization without the need for toxic 2-hydroxyethyl methacrylate (HEMA) monomers. The effects of using CM liquids with 0 or 5 wt% HEMA on the physical/mechanical properties and cytotoxicity of the experimental RMGICs were assessed. Spherical pre-reacted glass fillers (SPG) were used as the powder phase. The experimental RMGICs were prepared by mixing SPG with CM liquid (0 wt% HEMA, F1) or CMH liquid (5 wt% HEMA, F2). Commercial materials (Vitrebond, VB, TheraCal LC, TC) were used for the comparisons. The degree of monomer conversion and fluoride release of both F1 and F2 were significantly lower than those of VB. F1 showed comparable biaxial flexural strength with VB but higher strength than TC. The dimensional stability (mass/volume changes) of the experimental materials was comparable with that of the commercial materials. F1 and F2 exhibited higher Sr/Ca ion release and relative cell viability than VB. The use of CMH liquid reduced the strength but enhanced the fluoride release of the experimental RMGICs. In conclusion, the experimental RMGICs showed comparable strength but lower cytotoxicity compared to the commercial RMGICs. These novel materials could be used as alternative materials for pulp protection.

Digital light processing (DLP), a subclass of vat photopolymerization, is one of the most efficient additive manufacturing (AM) techniques that can be used to print complex objects with high precision at a greater speed than those of the other AM processes. However, printed objects are typically brittle because networks of cured resins are highly crosslinked, thereby limiting their range of possible applications. Currently, only a few commercial photocurable elastomers used for DLP can produce materials with moderate tensile strain, poor strength, and low modulus. Herein, we present a simple method for preparing photocurable resins that not only exhibit a low viscosity at room temperature, but also demonstrate tunable elasticity and strength. These novel resins are prepared from commercially available acrylate-based oligomers and monomers, which are appropriately selected to achieve a variety of mechanical properties. Subsequenlty, key parameters are investigated, including the viscosity of the uncured resin, critical energy at which the resin begins to solidify (Ec), depth of penetration of the curing light (Dp), and degree of curing. The viscosities of the developed resins range between 0.85 and 3.10 Pa s, and their curing and mechanical properties can be adjusted by varying the oligomer-to-monomer weight ratio. The Ec (6.9–9.2 mJ cm−2) and Dp (192–271 μm) of all the uncured resins are obtained from the working curves. The developed photoelastomers exhibit a wide range of tensile properties (tensile strain of 110–365%, tensile strength of 0.8–10 MPa, and modulus of 0.5–10 MPa), thereby facilitating their use in various applications.

Calcium phosphate cements (CPCs) have been extensively used as bone graft substitutes for the repair of bone defect due to its biocompatibility, osteoconductivity and in-situ setting capability. They poorly degrade thus limiting their use in tissue engineering application. A possible strategy to improve the speed of CPC degradation is to add porogen to CPC to create macropores that can enhance cement resorption and can consequently be replaced by new bone. The as-generated macropores are generally not connected because of spherical shape of the porogens which can limit the extent of newly formed bone. The aim of this study was to fabricate CPCs having tubular macroporous structure by incorporating fast-dissolving maltodextrin microstrips (MDMS) and explore their properties such as setting time, mechanical property, microstructure and degradability of the cements. The results showed that after immersing MDMS-embedded composites in simulated body fluid under physiological condition for 1 d MDMS rapidly disintegrated (more than 70%), generating tubular macropores in CPCs. The disintegration of MDMS completed in 1 week. CPCs containing MDMS lower than 30% by weight had the same final setting time as those without MDMS. The average values of compressive strength of the CPC composites decreased with the disintegration of MDMS. % Porosity and pore interconnectivity increased with increasing MDMS content. In addition, MDMS-embedded CPCs were cell friendly with excellent cell adhesion, indicating a possible candidate as bone graft substitutes.

The fabrication of hydroxyapatite scaffolds for bone tissue engineering applications by using lithography-based additive manufacturing techniques has been introduced due to the abilities to control porous structures with suitable resolutions. In this research, the use of hydroxyapatite cellular structures, which are processed by lithography-based additive manufacturing machine, as a bone tissue engineering scaffold was investigated. The utilization of digital light processing system for additive manufacturing machine in laboratory scale was performed in order to fabricate the hydroxyapatite scaffold, of which biocompatibilities were eventually evaluated by direct contact and cell-culturing tests. In addition, the density and compressive strength of the scaffolds were also characterized. The results show that the hydroxyapatite scaffold at 77% of porosity with 91% of theoretical density and 0.36 MPa of the compressive strength are able to be processed. In comparison with a conventionally sintered hydroxyapatite, the scaffold did not present any cytotoxic signs while the viability of cells at 95.1% was reported. After 14 days of cell-culturing tests, the scaffold was able to be attached by pre-osteoblasts (MC3T3-E1) leading to cell proliferation and differentiation. The hydroxyapatite scaffold for bone tissue engineering was able to be processed by the lithography-based additive manufacturing machine while the biocompatibilities were also confirmed.

Porous oligolactide-hydroxyapatite composite scaffolds were obtained by stereolithographic fabrication. Gentamicin was then coated on the scaffolds afterwards, to achieve antimicrobial delivery ability to treat bone infection. The scaffolds examined by stereomicroscope, SEM, and μCT-scan showed a well-ordered pore structure with uniform pore distribution and pore interconnectivity. The physical and mechanical properties of the scaffolds were investigated. It was shown that not only porosity but also scaffold structure played a critical role in governing the strength of scaffolds. A good scaffold design could create proper orientation of pores in a way to strengthen the scaffold structure. The drug delivery profile of the porous scaffolds was also analyzed using microbiological assay. The release rates of gentamicin from the scaffolds showed prolonged drug release at the levels higher than the minimum inhibitory concentrations for S. aureus and E. coli over a 2-week period. It indicated a potential of the scaffolds to serve as local antibiotic delivery to prevent bacterial infection.

The merging of stereolithography (SLA) technology to the medical field certainly benefits the manufacturing of parts, especially those patient-specific for the clinical use. This technique, however, has hardly been exploited medically due to a limited number of biodegradable resins for SLA processing. To extend application of SLA in the biomedical field, photocurable oligolactide resins were developed and examined for biodegradation and biocompatibility. The degradation was studied by monitoring the changes in weight loss, and thermal and mechanical properties of the photocured specimens in phosphate buffered saline (PBS) at 37°C. The results demonstrated that a resin composition played an important role in degradation, and the retarded degradation rate was observed for the highly crosslinked resin containing hydroxyapatite (HA). The less cytotoxic sample was also obtained from the resin with higher content of HA. These findings suggest the possible use of the developed photocurable oligolactide resins in SLA manufacturing of biodegradable implants, where their degradation behaviors can be designed by varying the resin composition. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 604–611, 2014.

The study aimed to investigate the selective blue-laser lithography that can fabricate the biomedical materials. The major advantage of using blue-laser instead of UV laser is to lower the machine and operating costs but still keeping the proper part quality for biomedical applications. The material used in the study is the bisphenol a diglycidylether methacrylate (BisGMA) which is specific formulated for photo-polymerizing with blue laser (wavelength = 473nm). The fabricated parts were preliminarily examined by flexural strength testing and in vitro testing of toxicity by direct contact test. The results showed that the flexural strength of fabricated part was about 92% as compared to the flexural strength of hand-pressed PMMA. The in vitro testing of toxicity, confirmed that the fabricated part by the selective blue-laser lithography with BisGMA material has good biocompatibility.

Stereolithography (SL), one of rapid prototyping techniques, has many advantages over other methods in fabrication of three dimensional objects, particularly those used in biomedical fields. Various complex medical objects, especially scaffold, can be precisely custom-constructed using this technique. This research aims to evaluate the effect of different scaffold architectures, fabricated with photosensitive liquid polymer using SL technique, on cell responses in terms of cell proliferation and alkaline phosphatase (ALP) activity. A variety of difunctional and trifunctional (meth)acrylate resin formulations were evaluated for mechanical strength by three-point bending using Universal Testing Machine. Volume shrinkage for each formulation was also investigated. The most promising resin composition for stereolithography technique that exhibited good mechanical strength and low shrinkage was chosen for scaffold fabrication. Five scaffold architectures with different percentages of porosity, designed by computer-aided design program (CAD), were successfully fabricated to microscale scaffolds using stereolithography apparatus equipped with UV laser source. Microscale images of stereolithographic-fabricated scaffolds were observed under a scanning electron microscope (SEM). Alamar blue and alkaline phosphatase assays were used to investigate biological responses of scaffolds. The results revealed that no significant difference in cell proliferation for all patterns after 21-day culture period whereas a lower porous scaffold exhibited a greater ALP activity. 

The aim of this investigation was to determine degree of conversion, and flexural and compressive strength of photocurable acrylic resin. The acrylic resins based on bis-phenol A glycidyl dimethacrylate (BisGMA) and triethylene glycol dimethacrylate (TEGDMA) were formulated and then irradiated with red light to form a solid crosslinked polymer. Various post curing conditions were studied to investigate their effects on curing efficiency. Degree of conversion was analyzed by means of Fourier Transform Infrared Spectroscopy (FTIR) to monitor the quantity of remaining acrylic double bond in the cured resin. Three-point bending and compressive strength were tested using Universal Testing Machine (UTM) to evaluate the mechanical performance. Our investigation demonstrated that the formulated acrylic resins were possibly polymerized under irradiation with red light and degree of conversion and mechanical properties were closely correlated.

The major concern related to biodegradable bone substitute materials is the loss of mechanical strength which can be undesirable when occurring too quickly before new bone formation. In this study, the multifunctional lactide oligomers having 2, 3, and 4 arms end capped with methacrylate groups were synthesized with the aim of improving the degradation properties. Their composites with hydroxyapatite (HA) were photopolymerized and subjected to accelerated degradation at 60 °C. The results showed that increasing number of arms significantly improved thermal and mechanical properties as well as biocompatibility of the composites. All composites although varying in number of arms had similar levels of bone-specific gene expression and calcification indicating their equal bioactivity in supporting bone formation. The high HA content in the composites was proposed to be responsible for enhanced osteoblast response, and this tended to suppress the effects of polymeric structure.

Xylan was first modified with maleic anhydride (MA) to obtain xylan-MA. The derivative was then blended with polyvinyl alcohol (PVA) to generate xylan-MA/PVA hydrogel. Xylan-MA was prepared by reacting xylan with MA under an acidic condition. A ring opening of MA occurred, yielding ester linkages between xylan and MA, as verified by 13C-NMR and FTIR. The effects of reaction temperature and weight ratio of xylan to MA on esterification were examined. Thermal stability of modified xylan derivatives was compared with that of pure xylan using TGA. The blends of xylan-MA with PVA became crosslinked gel after being heated at high temperature. The influences of MA and PVA contents on strength and swelling behaviors of the gels were investigated. The cytotoxicity of the gels was also evaluated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1914–1918, 2006

The Pd-PCy 3 (Cy=cyclohexyl) system effectively catalyzed hydrosilylation polymerization of dihydrosilanes with p - or m -diethynylbenzene to give silylene-divinylene polymers with Ph, Me, and/or vinyl substituents at the silicon atoms. The resulting polymers showed characteristic absorption and fluorescence spectra in ultraviolet to visible region. p -Phenylene polymers displayed λ max peaks in longer wavelength region than the corresponding m -phenylene polymers. In TGA, the 5% weight loss temperatures (Td 5 ) ranged from 436 to 501 °C, indicating rather high thermal stability of these polymers. Vinyl group-containing polymers exhibited higher Td 5 values and char yields than other polymers.

The merging of stereolithography (SLA) technology to the medical field certainly benefits the manufacturing of parts, especially those patient-specific for the clinical use. This technique, however, has hardly been exploited medically due to a limited number of biodegradable resins for SLA processing. To extend application of SLA in the biomedical field, photocurable oligolactide resins were developed and examined for biodegradation and biocompatibility. The degradation was studied by monitoring the changes in weight loss, and thermal and mechanical properties of the photocured specimens in phosphate buffered saline (PBS) at 37°C. The results demonstrated that a resin composition played an important role in degradation, and the retarded degradation rate was observed for the highly crosslinked resin containing hydroxyapatite (HA). The less cytotoxic sample was also obtained from the resin with higher content of HA. These findings suggest the possible use of the developed photocurable oligolactide resins in SLA manufacturing of biodegradable implants, where their degradation behaviors can be designed by varying the resin composition.

The dressing prepared from GTMAC modified chitin–PAA was introduced with the aim of facilitating wound healing, particularly those effectively absorbing exudates, maintaining a moist wound environment and controlling bacterial proliferation. Chitin was chemically modified with acrylic acid to encourage a moist wound healing environment. The highly water-absorbable resulting product (chitin–PAA) was further reacted with glycidyltrimethylammonium chloride (GTMAC) to impart antibacterial activities. The final product, chitin–PAA–GTMAC was characterized by the techniques of Fourier Transform Infrared (FTIR), solid state 15N NMR, and elemental analysis. Their cytotoxicity and antibacterial activities against S. epidermidis and E. coli were evaluated which found increasing effects in those properties with increasing degree substitution of GTMAC. All materials also showed good blood-clotting ability. The collagen gel contraction assay was used to analyze the behavior of fibroblasts after contact with the gels. The extent of the gel contraction as well as the examination of the secreted interleukin-8 (IL-8) and transforming growth factor-β1 (TGF-β1) were investigated. The results showed that chitin-PAA modified with GTMAC could stimulate the production of IL-8, but TGF-β1. Fibroblasts presented normal spreading and formation of cellular processes in the collagen gels with all of the modifications. Furthermore, all modified gels except for the highest GTMAC content gel [chitin–PAA–GTMAC (1:20)] were found a greater extent in gel contraction than the unmodified chitin–PAA. It suggested the promoting effect of GTMAC on cell proliferation if the GTMAC content in the gel was not too high, that is, the mole ratio of glucosamine to GTMAC of the gel should not greater than 1:10. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A:, 2011.

Polyacrylic acid grafted chitin (Chitin-PAA) contains a hydrogel characteristic that makes it more suitable for wound dressing application. In animal models, Chitin-PAA dressing exhibited properties as a promising dressing. Epithelization promotion, rapid reduction of wound size, reduction of inflammatory cell response, and less toxicity had been noted.Carryout a pilot clinical comparative study of Chitin-PAA dressing, lipido-colloid absorbent dressing, and alginate wound dressing in the treatment of partial-thickness wound.Between June 2006 and March 2007, 36 partial-thickness wounds were randomized into three groups and three different types of dressing were used. Each wound was treated until it was completely healed, and a visual analogue scale was used for the pain evaluation.The present study shows the visual analogue pain score in the Chitin-PAA group seems to be a bit higher than the Urgocell group but not statistically different. The completely healed day is not significantly different. Three patients in the lipido-colloid absorbent dressing groups had wound infection but eventually healed after treatment.There was no statistical difference in terms of visual analogue pain score and healing time between the lipido-colloid absorbent dressing, alginate dressing, and chitin-PAA dressing.

Charged derivatives of chitosan, N -sulfofurfuryl chitosan (SFC) and N -[(2-hydroxyl-3-trimethylammonium)propyl]chitosan chloride (HTACC) were prepared by reductive alkylation of amino groups of chitosan (CHI) using 5-formyl-2-furansulfonic acid, sodium salt (FFSA) as a reagent and ring opening of glycidyltrimethylammonium chloride (GTMAC) by amino groups of chitosan, respectively. The chemical structures of the charged derivatives were verified by 1 H NMR and FTIR analyses. Multilayer assembly of SFC, HTACC, CHI and the selected oppositely charged polyelectrolytes was monitored by a quartz crystal microbalance (QCM). Stratification of the multilayer film fabricated on plasma-treated poly(ethylene terephthalate) (treated PET) substrate was demonstrated by water contact angle data. The coverage of the assembled films was characterized by AFM and ATR-FTIR analyses. The bioactivity of the deposited multilayer film on the treated PET substrate was tested against selected proteins having a distinctive size and charge. This research strongly suggests that both SFC and HTACC are potential candidates for altering the surface bioactivity of materials.

Hydrogermylation polymerization of diphenylgermane with aliphatic and aromatic diynes smoothly proceeded in the presence of Pd-PCy 3 (Cy = cyclohexyl) catalysts to give new germylene-divinylene polymers in high yields.