Bioactive-Enhanced Polyetheretherketone Dental Implant Materials: Mechanical Characterization and Cellular Responses
The aim of this study was to characterize the mechanical properties of a bioactive-modified polyetheretherketone (PEEK) manufacturing approach for dental implants and to compare the in vitro biological behavior with titanium alloy (Ti6Al4V) as the reference. PEEK, PEEK with 5% hydroxyapatite (HA), PEEK with 5% beta-tricalcium phosphate (βTCP), and Ti6Al4V discs were produced using hot pressing technology to create a functionally graded material (FGM). Surface roughness values (Ra, Rz), water contact angle, shear bond strength, and Vickers hardness tests were performed. Human osteoblasts and gingival fibroblasts bioactivity was evaluated by a resazurin-based method, alkaline phosphatase activity (ALP), and confocal laser scanning microscopy (CLSM) images of fluorescent-stained fibroblasts. Morphology and cellular adhesion were confirmed using field emission gun-scanning electron microscopy (FEG-SEM). Group comparisons were tested using analysis of variance (Tukey post hoc test), α = .05. All groups presented similar roughness values (P > .05). Ti6Al4V group was found to have the highest contact angle (P < .05). Shear bond strength and Vickers hardness of different PEEK materials were similar (P > .05); however, the mean values in the Ti6Al4V group were significantly higher when compared with those of the other groups (P < .05). Cell viability and proliferation of osteoblast and fibroblast cells were higher in the PEEK group (P < .05). PEEK-βTCP showed the highest significant ALP activity over time (P < .05 at 14 days of culture). An enhanced bone and soft-tissue cell behavior on pure PEEK was obtained to the gold standard (Ti6Al4V) with equivalent roughness. The results substantiate the potential role of chemical composition rather than physical properties of materials in biological responses. The addition of 5% HA or βTCP by FGM did not enhance PEEK mechanical properties or periodontal cell behavior.
Field emission gun-scanning electron micrographs after surface treatment of titanium alloy, polyetheretherketone (PEEK), PEEK–hydroxyapatite, and PEEK–β-tricalcium phosphate samples (magnification ×150).
Figure 2. Contact angle (°) and roughness values (Ra [μm] and Rz [μm]) for titanium alloy (Ti6Al4V), polyetheretherketone (PEEK), PEEK–hydroxyapatite (HA), and PEEK–β-tricalcium phosphate (βTCP) surfaces as mean and standard deviation. *All pairwise comparisons for mean of contact angle measurements are significantly different (P < .05). Figure 3. (a) Shear bond strength and (b) Vickers hardness recorded for Ti6Al4V, PEEK, PEEK-HA, and PEEK-βTCP materials as the mean and standard deviation. Figure 4. Bar charts showing osteoblast and fibroblast viability measured as the mean using fluorescence intensity expressed in arbitrary resorufin units and osteoblast and fibroblast proliferation ratios as the mean calculated as the reason for the presence resorufin at 7 days/1 day, 14 days/1 day, and 14 days /1 day. Error bars represent standard deviation. Repeated-measures 1-way analysis of variance with post hoc Tukey test were used for comparisons between study groups. Statistical significance: *P < .05.
(a) Field emission gun-scanning electron micrographs (FEG-SEM) of osteoblasts cultured on titanium alloy (Ti6Al4V), polyetheretherketone (PEEK), PEEK–hydroxyapatite (HA), and PEEK–β-tricalcium phosphate (βTCP) surfaces at 1 day and 7 days with magnification ×5000 and ×2000, respectively. (b) FEG-SEM of fibroblasts cultured on Ti6Al4V, PEEK, PEEK-HA, PEEK-βTCP surfaces at 1 day with magnification ×1000 and at 7 days with magnification ×500.
Mean alkaline phosphatase activity (mU/μL) measured in osteoblasts cultured on titanium alloy (Ti6Al4V), polyetheretherketone (PEEK), PEEK–hydroxyapatite, and PEEK–β-tricalcium phosphate for 7 and 14 days, respectively. A one-way analysis of variance with post hoc Tukey test was used for comparisons between study groups. Error bars represent the standard deviation. *P < .05.
Fluorescence photomicrographs of DAPI fluorescent nucleic acid staining of fibroblasts after 3 days in cell culture on titanium alloy (Ti6Al4V), polyetheretherketone (PEEK), PEEK–hydroxyapatite, and PEEK–β-tricalcium phosphate specimens. Images are representative of 3 replicates.
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