The goal of this study was to evaluate the in vitro cellular toxicity and biological behavior of new bone graft composites after subcutaneous implantation during remodeling and wound-healing processes. We developed composites based on hydroxyapatite (obtained by deproteinizing bovine bone), collagen (obtained from bovine tendon) and chitosan (obtained from gladii of the squid species Loligo), that were characterized by different techniques (X-ray, FT-IR, Thermogravimetry, DSC and SEM). Three biomaterials were evaluated here: B1 (collagen/chitosan/hydroxyapatite), B2 (collagen/hydroxyapatite) B3 (collagen/hydroxyapatite). For in vitro cytotoxicity tests, two cell lines were used: HEp human larynx tumor cells (ATCC-CCL-23) and VERO cells from African green monkey (Cercopithecus aethiops). These toxicity tests demonstrated that the evaluated composites are not toxic. In biocompatibility tests, the results of a histological analysis showed that all three biomaterials present a low inflammatory tissue reaction. The tissue response was most favorable for sample B3, followed by B2 and B1, in that order. Based on these results, we conclude that all three biomaterials show good biocompatibility and no evidence of cytotoxicity; thus, these materials represent good candidates for tissue and graft engineering for use in bone regeneration.
This study aimed to analyze the kinetic parameters of two monomers using attenuated total reflectance Fourier transform infrared (ATR-FTIR): 2,2-bis-[4-(2-hydroxy-3-methacryloxypropyl-1-oxy)-phenyl] propane (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA). The following were calculated to evaluate the kinetic parameters: maximum conversion rate (Rp max ), time at the maximum polymerization rate ( max ), conversion at Rp max , and total conversion recorded at the maximum conversion point after 300 s. Camphorquinone (CQ) and phenyl propanedione (PPD) were used in this study as photoinitiators, whereas N,Ndimethyl-p-toluidine (DMPT) amine was used as a coinitiator. LED apparatus and halogen lamp were used in turn to evaluate the effect that light source had on the monomer kinetics. The mass concentration ratio for the three resin preparations was 0.7 : 0.3 for Bis-GMA and TEGDMA: R1 (CQ + DMPT), R2 (PPD + DMPT), and R3 (PPD + CQ + DMPT). The PPD association with the CQ photoinitiator altered the polymerization kinetics compared to a resin containing only the CQ photoinitiator. The light sources exhibited no significant differences for max of R1 and R3. Resins containing only the PPD initiator exhibited a higher max than those containing only CQ. However, the Rp max decreased for resins containing the PPD photoinitiator.
The effect of different propionaldehyde ratios on the properties of bis-GMA-based comonomers and copolymers diluted with propoxylated bis-GMA (CH 3 bis-GMA) was evaluated. Five experimental comonomers were prepared combining bis-GMA with CH 3 bis-GMA and propionaldehyde at 0, 2, 8, 16, 24 mol%. Light polymerization was effected with the use of 0.2 wt. (%) each of camphorquinone and N,N-dimethyl-p-toluidine. Resin degrees of conversion (%DC) were evaluated by FT-IR spectrophotometry and T g by Differential Scanning Calorimeter. Complex viscosity (η*), the effect of temperature on η*, and Microhardness (H) for dry and wet samples were also determined. Data were analyzed by Student's t-test, one-way ANOVA and Tukey-Kramer test (α = 0.05). The group with 24 mol% additive had a significant increase in %DC and H, and the lowest comonomer T g and η*. No remarkable variation was noted in copolymers T g s. All resins presented Newtonian behavior of viscosity, which linearly decreased with increased temperature. The η* decreased sigmoidally as the additive ratio increased.
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