Enhancement of thermal, mechanical and physical properties of polyamide 12 composites via hybridization of ceramics for bone replacement.

This study reports the influence of ZrO2/ß-TCP hybridization on the thermal, mechanical, and physical properties of polyamide 12 composites to be suited for bone replacement. Amount of 15 wt% of nano-ZrO2 along with 5,10,15,20 and 25 wt% of micro-ß-TCP was compounded with polyamide 12 via a twin-screw extruder. The hybrid ZrO2/ß-TCP filled polyamide 12 exhibited higher thermal, mechanical and physical properties in comparison to unfilled polyamide 12 at certain filler loading; which is attributed to the homogenous dispersion of ZrO2/ß-TCP fillers particle in polyamide 12 matrix. The hybrid ZrO2/ß-TCP filled PA 12 demonstrated an increment of tensile strength by up to 1%, tensile modulus of 38%, flexural strength of 15%, flexural modulus of 45%, and surface roughness value of 93%, as compared to unfilled PA 12. With enhanced thermal, mechanical and physical properties, the newly developed hybrid ZrO2/ß-TCP filled PA 12 could be potentially utilized for bone replacement.

Mechanical and cytotoxicity properties of hybrid ceramics filled polyamide 12 filament feedstock for craniofacial bone reconstruction via fused deposition modelling.

OBJECTIVE: To compare the mechanical and biological properties of newly developed hybrid ceramics filled and unfilled polyamide 12 (PA 12) for craniofacial reconstruction via a fused deposition modelling (FDM) framework. METHODS: 15wt% of zirconia (ZrO2) as well as 30, 35, and 40wt% of beta-tricalcium phosphate (ß-TCP) were compounded with PA 12, followed by the fabrication of filament feedstocks using a single screw extruder. The fabricated filament feedstocks were used to print the impact specimens. The melt flow rate, tensile properties of fabricated filament feedstocks, and 3D printed impact properties of the specimens were assessed using melt flow indexer, universal testing machine, and Izod pendulum tester, respectively. The microstructure of selected filament feedstocks and broken impact specimens were analysed using a field emission scanning electron microscope and universal testing machine. Human periodontal ligament fibroblast cells (HPdLF) were used to evaluate the cytotoxicity of the materials by (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromid) (MTT) assay. RESULTS: Hybrid ceramics filled PA 12 indicated sufficient flowability for FDM 3D printing. The tensile strength of hybrid ceramics filled PA 12 filament feedstocks slightly reduced as compared to unfilled PA 12. However, the tensile modulus and impact strength of hybrid ceramics filled PA 12 increased by 8%-31% and 98%-181%, respectively. A significant increase was also detected in the cell viability of the developed composites at concentrations of 12.5, 25, 50 and 100mg/ml. SIGNIFICANCE: The newly developed hybrid ceramics filled PA 12 filament feedstock with improved properties is suitable for an FDM-based 3D printer, which enables the creation of patient-specific craniofacial implant at a lower cost to serve low-income patients.

Water sorption characteristics of restorative dental composites immersed in acidic drinks.

OBJECTIVES: To determine the diffusion coefficient, water sorption and solubility of various types of restorative dental composites and to evaluate the effect of acidic media (orange juice and coke) on their characteristics. METHODS: Resin composite specimens (Filtek™ Z350, Spectrum(®) TPH(®)3 and Durafill(®) VS) were prepared in a stainless steel mold of 1mm thickness and 10mm diameter (n=5) and light-cured. All samples were dried at 37°C, immersed in media (distilled water, orange and coke) at 37°C and weighed at suitable time intervals (15, 35, 155, 320, 785, etc.min) until 40 days of immersion and then were dried again for 40 days. Diffusion coefficient (m(2)s(-1)) was determined according to Fick's second law while water sorption and solubility (µg/mm(3)) were calculated based on BS EN ISO 4049:2000. Data of water sorption and solubility were analyzed with One-Way ANOVA and post hoc Scheffe test at p=0.05. RESULTS: The experimental data obtained were obeyed and nearly fitted to the diffusion theoretical data plot. The highest values of diffusion coefficients were presented by Durafill(®) VS (32.23-45.25×10(-13)m(2)s(-1)). Diffusion coefficients of Filtek™ Z350 and Spectrum(®) TPH(®)3 were the highest when immersed in coke media followed by distilled water and orange juice. The water sorption of most composites was significantly increased after immersion in coke and orange (p<0.05). Meanwhile only Spectrum(®) TPH(®)3 showed an increase in solubility when immersed in coke media. Z350 presented the highest water sorption after immersion in distilled water and coke (16.13 and 18.22µg/mm(3)) while Durafill(®) VS presented the highest solubility (7.20-9.27µg/mm(3)). SIGNIFICANCE: The exposure of restorative dental composites to acidic drinks can cause an increase in diffusion coefficient, water sorption and solubility parameters which may accelerate the degradation process and thus reduce the life span of composite restoration.