Zirconia, with outstanding mechanical strength, wear resistance, and biocompatibility, has been considered as a promising material for dental computer-aided design/computer-aided manufacture (CAD/CAM). However, high hardness and brittleness, pale appearance, and ageing cause clinical issues such as potential chipping and fracture, unwanted wear of the opposite teeth, and poor machinability, which limit the long-term performance of zirconia restoration. Materials with both high strength and toughness are still in need for dental CAD/CAM restoration[1].

On the other hand, the polymer-infiltrated-ceramic-network (PICN), with a sintered porous ceramic matrix infiltrated with polymer showed great potential for dental CAD/CAM application with a balance of machinability and mechanical property. Moreover, to fabricate better dental restoration, efforts of bio-inspiration have been made to fabricate composite mimicking the ‘brick and mortar’ microstructure of nacre, which has both high strength and toughness. As a result, zirconia could be incorporated into PICN with nacre-like microstructure to fabricate dental CAD/CAM restoration[2][3].

In this study, bioinspired nacre-like zirconia/PMMA composite has been fabricated via bi-directional freeze casting. This composite showed a similar ‘brick and mortar’ microstructure as nacre. The flexural strength ranges from 150MPa to 290MPa depending on different kinds of zirconia and different ceramic fraction, which could support the clinical use of this composite. Also, Young’s modulus of this composite is within the range of human enamel, which ensures the safety of functioning in oral cavity. Moreover, this composite shows great fracture toughness indicated by an increasing crack resistant behaviour, which ensure a better long-term clinical performance. (Figure 1.)

These results illustrated this bioinspired nacre-like zirconia/PMMA composite is promising for dental CAD/CAM restoration.

References

[1] N. C. Lawson, K. Frazier, A. K. Bedran-Russo, S. Khajotia, J. Park, and O. Urquhart, “Zirconia restorations: An American Dental Association Clinical Evaluators Panel survey,” J. Am. Dent. Assoc., vol. 152, no. 1, pp. 80-81.e2, Jan. 2021, doi: 10.1016/j.adaj.2020.10.012.

[2] A. Della Bona, P. H. Corazza, and Y. Zhang, “Characterization of a polymer-infiltrated ceramic-network material,” Dent. Mater., vol. 30, no. 5, pp. 564–569, 2014, doi: 10.1016/j.dental.2014.02.019.

[3] G. Tan et al., “Nature-Inspired Nacre-Like Composites Combining Human Tooth-Matching Elasticity and Hardness with Exceptional Damage Tolerance,” Adv. Mater., vol. 31, no. 52, pp. 1–9, 2019, doi: 10.1002/adma.201904603.