Mechanical Properties and In Vitro Biocompatibility of Hybrid Polymer-HA/BAG Ceramic Dental Materials

The aim of this study is to prepare hybrid polymer-ceramic dental materials for chairside computer-aided design/computer-aided manufacturing (CAD/CAM) applications. The hybrid polymer-ceramic materials were fabricated via infiltrating polymerizable monomer mixtures into sintered hydroxyapatite/bioactive glass (HA/BAG) ceramic blocks and thermo-curing. The microstructure was observed by scanning electron microscopy and an energy-dispersive spectrometer. The phase structure was analyzed by X-ray diffraction. The composition ratio was analyzed by a thermogravimetric analyzer. The hardness was measured by a Vickers hardness tester. The flexural strength, flexural modulus, and compressive strength were measured and calculated by a universal testing machine. The growth of human gingival fibroblasts was evaluated by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) colorimetric assay and immunofluorescence staining. The results showed that the sintering temperature and BAG content affected the mechanical properties of the hybrid polymer-ceramic materials. The X-ray diffraction analysis showed that high-temperature sintering promoted the partial conversion of HA to β-tricalcium phosphate. The values of the hardness, flexural strength, flexural modulus, and compressive strength of all the hybrid polymer-ceramic materials were 0.89-3.51 GPa, 57.61-118.05 MPa, 20.26-39.77 GPa, and 60.36-390.46 MPa, respectively. The mechanical properties of the hybrid polymer-ceramic materials were similar to natural teeth. As a trade-off between flexural strength and hardness, hybrid polymer-ceramic material with 20 wt.% BAG sintered at 1000 °C was the best material. In vitro experiments confirmed the biocompatibility of the hybrid polymer-ceramic material. Therefore, the hybrid polymer-ceramic material is expected to become a new type of dental restoration material.