Improved performance of diatomite-based dental nanocomposite ceramics using layer-by-layer assembly

Xiaoli Lu^1,2, Yang Xia¹, Mei Liu¹, Yunzhu Qian³, Xuefeng Zhou⁴, Ning Gu⁴, Feimin Zhang^1,4
1Institute of Stomatology, Nanjing Medical University, Nanjing, ²Nantong Stomatological Hospital, Nantong, ³Center of Stomatology, The Second Affiliated Hospital of Suzhou University, Suzhou, ⁴Suzhou Institute, Southeast University, Suzhou, People's Republic of China

Abstract: To fabricate high-strength diatomite-based ceramics for dental applications, the layer-by-layer technique was used to coat diatomite particles with cationic [poly(allylamine hydrochloride)] and anionic [poly(sodium 4-styrenesulfonate)] polymers to improve the dispersion and adsorption of positively charged nano-ZrO₂ (zirconia) as a reinforcing agent. The modified diatomite particles had reduced particle size, narrower size distribution, and were well dispersed, with good adsorption of nano-ZrO₂. To determine the optimum addition levels for nano-ZrO₂, ceramics containing 0, 20, 25, 30, and 35 wt% nano-ZrO₂ were sintered and characterized by the three-point bending test and microhardness test. In addition to scanning electron microscopy, propagation phase-contrast synchrotron X-ray microtomography was used to examine the internal structure of the ceramics. The addition of 30 wt% nano-ZrO₂ resulted in the highest flexural strength and fracture toughness with reduced porosity. Shear bond strength between the core and veneer of our diatomite ceramics and the most widely used dental ceramics were compared; the shear bond strength value for the diatomite-based ceramics was found to be significantly higher than for other groups (P < 0.05). Our results show that diatomite-based nanocomposite ceramics are good potential candidates for ceramic-based dental materials.

Keywords: layer-by-layer, diatomite, nanoceramics, zirconia (ZrO₂), dental materials