*Article* **Evaluation of Carbon Dioxide-Based Urethane Acrylate Composites for Sealers of Root Canal Obturation**

**Hao-Hueng Chang 1,2, Yi-Ting Tseng <sup>3</sup> , Sheng-Wun Huang <sup>1</sup> , Yi-Fang Kuo <sup>1</sup> , Chun-Liang Yeh <sup>1</sup> , Chien-Hsin Wu <sup>3</sup> , Ying-Chi Huang <sup>3</sup> , Ru-Jong Jeng 3,\* , Jiang-Jen Lin 4,\* and Chun-Pin Lin 1,2,\***


Received: 24 January 2020; Accepted: 18 February 2020; Published: 21 February 2020

**Abstract:** A new root canal sealer was developed based on urethane acrylates using polycarbonate polyol (PCPO), a macrodiol prepared in the consumption of carbon dioxide as feedstock. The superior mechanical properties and biostability nature of PCPO-based urethane acrylates were then co-crosslinked with a difunctional monomer of tripropylene glycol diarylate (TPGDA) as sealers for resin matrix. Moreover, nanoscale silicate platelets (NSPs) immobilized with silver nanoparticles (AgNPs) and/or zinc oxide nanoparticles (ZnONPs) were introduced to enhance the antibacterial effect for the sealers. The biocompatibility and the antibacterial effect were investigated by Alamar blue assay and LDH assay. In addition, the antibacterial efficiency was performed by using *Enterococcus faecalis* (*E. faecalis*) as microbial response evaluation. These results demonstrate that the PCPO-based urethane acrylates with 50 ppm of both AgNP and ZnONP immobilized on silicate platelets, i.e., Ag/ZnO@NSP, exhibited great potential as an antibacterial composite for the sealer of root canal obturation.

**Keywords:** root canal obturation; composites; urethane acrylates; nanoscale silicate platelets; carbon dioxide-based resins
