*Article*

#### **Novel CaF2 Nanocomposites with Antibacterial Function and Fluoride and Calcium Ion Release to Inhibit Oral Biofilm and Protect Teeth**

**Heba Mitwalli 1,2, Abdulrahman A. Balhaddad 1,3, Rashed AlSahafi 1,4, Thomas W. Oates 5, Mary Anne S. Melo 5,6, Hockin H. K. Xu 5,7,8 and Michael D. Weir 5,\***


Received: 18 May 2020; Accepted: 28 July 2020; Published: 1 August 2020

**Abstract:** (1) Background: The objective of this study was to develop a novel dental nanocomposite containing dimethylaminohexadecyl methacrylate (DMAHDM), 2-methacryloyloxyethyl phosphorylcholine (MPC), and nanoparticles of calcium fluoride (nCaF2) for preventing recurrent caries via antibacterial, protein repellent and fluoride releasing capabilities. (2) Methods: Composites were made by adding 3% MPC, 3% DMAHDM and 15% nCaF2 into bisphenol A glycidyl dimethacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) (denoted BT). Calcium and fluoride ion releases were evaluated. Biofilms of human saliva were assessed. (3) Results: nCaF2+DMAHDM+MPC composite had the lowest biofilm colony forming units (CFU) and the greatest ion release; however, its mechanical properties were lower than commercial control composite (*p* < 0.05). nCaF2+DMAHDM composite had similarly potent biofilm reduction, with mechanical properties matching commercial control composite (*p* > 0.05). Fluoride and calcium ion releases from nCaF2+DMAHDM were much more than commercial composite. Biofilm CFU on composite was reduced by 4 logs (*n* = 9, *p* < 0.05). Biofilm metabolic activity and lactic acid were also substantially reduced by nCaF2+DMAHDM, compared to commercial control composite (*p* < 0.05). (4) Conclusions: The novel nanocomposite nCaF2+DMAHDM achieved strong antibacterial and ion release capabilities, without compromising the mechanical properties. This bioactive nanocomposite is promising to reduce biofilm acid production, inhibit recurrent caries, and increase restoration longevity.

**Keywords:** dental nanocomposite; calcium fluoride nanoparticles; remineralization; antibacterial; protein repellent; oral biofilm
