Experimental Study. Core-shell Nano-fiber Reinforced Toughened Dental Resin Matrix

Objective: Fabricate PAN-PMMA core and shell nanofibes by electrospun technology. A new method was used to blend the nanofibers with dental resin monomer to realize the distribution of nanofibers in the form of single-fibe. Study the effect of core-shell nanofibers to improve the mechanical properties of Bis-GMA/TEGDMA dental light-cured resin matrix at different mass ratio, further promote the clinical application of nanofiber reinforced dental filling composite. Methods: Fabricated the different PAN-PMMA core-shell nanofibers by a single-nozzle co-electrospinning technique. The diamiter, core-shell structure and suface morphous of nanofibers were determined by scanning electron microscope(SEM) and transmition electron microscope (TEM.) observation.. Blended the choiced nanofibers with Bis-GMA/TEGDMA Light-cured resin monomer at different mass fraction respectively. group A is control group, Control specimens did not contain fiber reinforcement. group B, C, D, E contain 1%, 2%, 3%, 5% nanofibers rspectively. Specimens were prepared using a standard mold of 2mm×2mm×25mm in dimension with eight specimens in each group. The flexural strength, flexural modulus and work of fracture of Bis-GMA resin, PAN–PMMA nanofiber reinforced composites were measured in a three-point bending test. The results were entered into spass version 11.0 for analysis. Selected fracture surfaces of the 3 point bending specimens were examined by SEM to investigate the distribution of nanofibers and the fiber-matrix interface.Result: Nanofibers fabricated with high concentration polymer solution are better. TEM and SEM observation showed that the diameter of nanofibers ranged from 200nm to 400nm, the surface was smooth, no beads were observed, the core-shell structure was evident. The michanical test result shows that as the concentrition of nanofiber increaed, the michanical properties of fiber reinforced groups increased firstly, and then decreased. The result of group C is the best, compared with the group A, the flextural strength increased from 88.13Mpa to 110.08MPa, flextural modulus increased from 1.32GPa to2.273GPa, work of fracture increased from 5.15kj/m2 to 7.576kj/m2, improved FS by 25%, EY by 74%, and WOF by 47% over those of the neat resin repectively. In groupA and groupB, the fracture surface of Specimens showed that the pulled-out fibers were rough, and bonded resin particals, suggested that the fiber-matrix interface was excellent. nanofibers were well-distributed, parallel or vertical to fracture surface. In group C and group D, the nanofibers aggregated severely as the mass ratio increased and a lot of fissures among nanofibers. A large area of unreinforced resin matrix was observed.Conclusion: Core-shell nanofiber reinforced dental composite was successfully fabricated by electrospun and a new mixing technology. The mechanical properties of the light-cured resin can be improved substantialy by appreciate amount of core-shell nanofibers. The mass fraction of nanofibers is one of the important factors that influence mechanical properties of composie. 2% may be the optimal mass ratio for core-shell nanofiber reinforced Bis-GMA/TEGDMA dental composites.