Structural Behavior of Bioinspired Dental Multilayer


Student thesis: Doctoral Thesis

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Awarding Institution
Award date22 Mar 2017


Tooth restoration is widely adopted to restore tooth function and improve oral health. However, current dental restorative products yield high failure rates and consequently entail additional medication costs and deterioration of oral health. This dissertation presents study of structural behaviors of dental composites and dental multilayer structures by combining both experimental and computational study.

Firstly, mechanical properties and deformation mechanism of dental composites were elucidated by multiscale indentation experiments in the goal of providing deeper understanding on the deformation mechanism of resin-based dental composites. Zirconia nanoparticle (NP) reinforced epoxy composites with 10-70 wt% NP filling contents were fabricated. A modified rule of mixtures was selected to describe relationship between NPs filling contents and elastic modulus which provided a basis for future designs of bioinspired dental restorative structures with epoxy/nano-zirconia composites. Indentation size effect (ISE) was characterized by conducting indentation tests from micro- to nanoscale. A model was proposed to describe relationship between indentation depth and hardness of epoxy/nano-zirconia composites. Mechanism and implication of ISE were discussed.

Secondly, tantalized by the superior damage resistance and sustainability of natural teeth, a bioinspired functionally graded dental adhesive (FGDA) was adopted to enhance bulk failure load of dental multilayer structure. FGDA was constructed with 5 mini layers of epoxy/nano-zirconia composites. From the bottom to the top layer of FGDA, mechanical properties were adjusted by adding NP filling contents which were 10, 20 30, 40 and 50 wt% in this thesis. Hertzian contact experiment was carried out on glass/FGDA/substrate dental multilayer structure. Structural bulk failure load was improved for more than 100% by introduction of FGDA comparing with that in conventional glass/cement/substrate dental multilayer structure. Assisted with high speed camera system and scanning electron microscopy (SEM), a three-stage crack evolution was characterized in the structures. Similar to the cracks generated in enamel of natural teeth, cracks generated in glass layer were successfully arrested by or deviated along glass-FGDA interfaces. Therefore, FGDA could maintain structural integrity and prevent restorative structure from a catastrophic fracture.

Last but not least, adhesive thickness dependency of radial crack initiation was studied in dental multilayer structure. Adhesive thickness ranged from several to more than a hundred microns, which was clinically relevant thickness of dental adhesives. Hertzian contact experiment was conducted on glass/cement/Z100 dental multilayer structure. Viscoelastic properties of the dental cements were applied to finite element analysis (FEA) simulation to predict strength of glass top layer and critical load of subsurface radial crack initiation. This investigation can provide useful information to design of dental multilayer with higher crack resistance.