Resin-based composites are widely used as dental restorative materials due to their excellent properties. They must have high modulus, high hardness, and be chemically inert while minimizing moisture uptake. To fulfill these higher standard prerequisites and properties, continuous improvements in each of their components are required. This study develops novel composites with multiple biofunctions. Light-cured Bis-GMA/TEGDMA dental resin (RK)/layered double hydroxide intercalated with fluoride ions (LDH-F)/calcium bentonite (Bt) hybrid composites were prepared. The loading ratio of LDH-F to Bt was varied, ranging from 2.5/2.5 to 10/10 parts per hundred RK and structural, mechanical, and biological properties were studied. The incorporation of even small mass fractions (e.g., 2.5 wt% of LDH-F and 2.5 wt% of Bt) in RK dental resin significantly improved the mechanical properties of the pristine resin. The synthetized materials showed antibacterial and antibiofilm effects against three bacterial strains isolated from healthy volunteers’ saliva (Streptococcus spp., Bacteroides fragilis, and Staphylococcus epidermidis) without affecting its ability to induce dental pulp stem cells differentiation into odontoblast-like cells. The capability to balance between the antibiofilm activity and dental pulp stem cells differentiation in addition with improved mechanical properties make these materials a promising strategy in preventive and restorative dentistry

Bibliografia:

- Marghalani, H.Y. Resin-Based Dental Composite Materials. In Handbook of Bioceramics and Biocomposites; Springer International Publishing: Berlin, Germany, 2016; pp. 357–405.

- Cramer, N.B.; Stansbury, J.W.; Bowman, C.N. Recent Advances and Developments in Composite Dental Restorative Materials. J. Dent. Res. 2011, 90, 402–416.

- Bowen, R.L. Use of epoxy resins in restorative materials. J. Dent. Res. 1956, 35, 360–369.

- Zagho, M.; Hussein, E.; Elzatahry, A. Recent Overviews in Functional Polymer Composites for Biomedical Applications. Polymers 2018, 10, 739.

- Zhang, H.; Darvell, B.W. Mechanical properties of hydroxyapatite whisker-reinforced bis-GMA-based resin composites. Dent. Mater. 2012, 28, 824–830.

- Patterson, J.W.H.S.H. Bentonite and fuller’s earth resources of the United States. Available online: https: //pubs.er.usgs.gov/publication/pp1522 (accessed on 17 December 2019).

- Sorrentino, A.; Gorrasi, G.; Vittoria, V. Permeability in clay/polyesters nano-biocomposites. In Green Energy and Technology; Springer: London, UK, 2012; Volume 50, pp. 237–264. ISBN 9781447141013.

- Moosavi, M. Bentonite Clay as a Natural Remedy: A Brief Review. Iran. J. Public Health 2017, 46, 1176–1183.

- Gorrasi, G.; Milone, C.; Piperopoulos, E.; Lanza, M.; Sorrentino, A. Hybrid clay mineral-carbon nanotube-PLA nanocomposite films. Preparation and photodegradation effect on their mechanical, thermal and electrical properties. Appl. Clay Sci. 2013, 71, 49–54.

- Miyazaki, M.; Ando, S.; Hinoura, K.; Onose, H.; Moore, B.K. Influence of filler addition to bonding agents on shear bond strength to bovine dentin. Dent. Mater. 1995, 11, 234–238.

- Nunes, M.F.; Swift, E.J.; Perdigão, J. Effects of adhesive composition on microtensile bond strength to human dentin. Am. J. Dent. 2001, 14, 340–343.

- Atai, M.; Solhi, L.; Nodehi, A.; Mirabedini, S.M.; Kasraei, S.; Akbari, K.; Babanzadeh, S. PMMA-grafted nanoclay as novel filler for dental adhesives. Dent. Mater. 2009, 25, 339–347.

- Nikolaidis, A.K.; Koulaouzidou, E.A.; Gogos, C.; Achilias, D.S. Synthesis and Characterization of Dental Nanocomposite Resins Filled with Different Clay Nanoparticles. Polymers 2019, 11, 730.

- Soares, C.J.; Faria-E-Silva, A.L.; De Paula Rodrigues, M.; Vilela, A.B.F.; Pfeifer, C.S.; Tantbirojn, D.; Versluis, A. Polymerization shrinkage stress of composite resins and resin cements—What do we need to know? Braz. Oral Res. 2017, 31, 62.

- Ersen, K.A.; Gürbüz, Ö.; Özcan, M. Evaluation of polymerization shrinkage of bulk-fill resin composites using microcomputed tomography. Clin. Oral Investig. 2019.

- Fronza, B.M.; Lewis, S.; Shah, P.K.; Barros, M.D.; Giannini, M.; Stansbury, J.W. Modification of filler surface treatment of composite resins using alternative silanes and functional nanogels. Dent. Mater. 2019, 35, 928–936.

- Tanner, J.; Tolvanen, M.; Garoushi, S.; Säilynoja, E. Clinical Evaluation of Fiber-Reinforced Composite Restorations in Posterior Teeth—Results of 2.5 Year Follow-up. Open Dent. J. 2018, 12, 476–485.

- Nedeljkovic, I.; Teughels, W.; De Munck, J.; Van Meerbeek, B.; Van Landuyt, K.L. Is secondary caries with composites a material-based problem? Dent. Mater. 2015, 31, e247–e277.

- Bernardo, M.; Luis, H.; Martin, M.D.; Leroux, B.G.; Rue, T.; Leitão, J.; DeRouen, T.A. Survival and reasons for failure of amalgam versus composite posterior restorations placed in a randomized clinical trial. J. Am. Dent. Assoc. 2007, 138, 775–783.

- Imazato, S.; McCabe, J.F. Influence of incorporation of antibacterial monomer on curing behavior of a dental composite. J. Dent. Res. 1994, 73, 1641–1645.

- Mirsayar, M.M. On fracture analysis of dental restorative materials under combined tensile-shear loading. Theor. Appl. Fract. Mech. 2018, 93, 170–176.

- Mirsayar, M.M.; Park, P. Modified maximum tangential stress criterion for fracture behavior of zirconia/veneer interfaces. J. Mech. Behav. Biomed. Mater. 2016, 59, 236–240.

- Tavassoli Hojati, S.; Alaghemand, H.; Hamze, F.; Ahmadian Babaki, F.; Rajab-Nia, R.; Rezvani, M.B.; Kaviani, M.; Atai, M. Antibacterial, physical and mechanical properties of flowable resin composites containing zinc oxide nanoparticles. Dent. Mater. 2013, 29, 495–505.

- Costantino, U.; Nocchetti, M.; Gorrasi, G.; Tammaro, L. Hydrotalcites in nanobiocomposites. In Multifunctional and Nanoreinforced Polymers for Food Packaging; Elsevier: Amsterdam, The Netherlands, 2011; pp. 43–85.

- Bugatti, V.; Esposito, L.; Franzetti, L.; Tammaro, L.; Vittoria, V. Influence of the powder dimensions on the antimicrobial properties of modified layered double hydroxide. Appl. Clay Sci. 2013, 75–76, 46–51.

- Stencel, R.; Kasperski, J.; Pakieła, W.; Mertas, A.; Bobela, E.; Barszczewska-Rybarek, I.; Chladek, G. Properties of Experimental Dental Composites Containing Antibacterial Silver-Releasing Filler. Materials 2018, 11, 1031.

- Xu, H.H.K.; Sun, L.; Weir, M.D.; Antonucci, J.M.; Takagi, S.; Chow, L.C.; Peltz, M. Nano DCPA-whisker composites with high strength and Ca and PO(4) release. J. Dent. Res. 2006, 85, 722–727.

- Tammaro, L.; Vittoria, V.; Calarco, A.; Petillo, O.; Riccitiello, F.; Peluso, G. Effect of layered double hydroxide intercalated with fluoride ions on the physical, biological and release properties of a dental composite resin. J. Dent. 2014, 42, 60–67.

- Conte, R.; De Luise, A.; Valentino, A.; Di Cristo, F.; Petillo, O.; Riccitiello, F.; Di Salle, A.; Calarco, A.; Peluso, G. Hydrogel Nanocomposite Systems. In Nanocarriers for Drug Delivery; Elsevier: Amsterdam, The Netherlands, 2019; pp. 319–349.

- Chenicheri, S.; Usha, R.; Ramachandran, R.; Thomas, V.; Wood, A. Insight into Oral Biofilm: Primary, Secondary and Residual Caries and Phyto-Challenged Solutions. Open Dent. J. 2017, 11, 312–333.

- Zitzmann, N.U.; Berglundh, T. Definition and prevalence of peri-implant diseases. J. Clin. Periodontol. 2008, 35, 286–291.

- Albrektsson, T.; Buser, D.; Chen, S.T.; Cochran, D.; DeBruyn, H.; Jemt, T.; Koka, S.; Nevins, M.; Sennerby, L.; Simion, M.; et al. Statements from the Estepona Consensus Meeting on Peri-implantitis, February 2-4, 2012. Clin. Implant Dent. Relat. Res. 2012, 14, 781–782.

- Wade, W.G. The oral microbiome in health and disease. Pharmacol. Res. 2013, 69, 137–143.

- Calarco, A.; Di Salle, A.; Tammaro, L.; De Luca, I.; Mucerino, S.; Petillo, O.; Riccitiello, F.; Vittoria, V.; Peluso, G. Long-Term Fluoride Release from Dental Resins Affects STRO-1 + Cell Behavior. J. Dent. Res. 2015, 94, 1099–1105.

- Di Salle, A.; Spagnuolo, G.; Conte, R.; Procino, A.; Peluso, G.; Rengo, C. Effects of various prophylactic procedures on titanium surfaces and biofilm formation. J. Periodontal Implant Sci. 2018, 48, 373.

- Constructing and Using a Drip Flow Reactor. Available online: https://www.cs.montana.edu/ webworks/projects/stevesbook/contents/chapters/chapter011/section021/blue/page001.html (accessed on 1 September 2019).

- He, Z.; Liang, J.; Zhou, W.; Xie, Q.; Tang, Z.; Ma, R.; Huang, Z. Effect of the quorum-sensing luxS gene on biofilm formation by Enterococcus faecalis. Eur. J. Oral Sci. 2016, 124, 234–240.

- Sorrentino, A.; Tortora, M.; Vittoria, V. Diffusion behavior in polymer-clay nanocomposites. J. Polym. Sci. Part B Polym. Phys. 2006, 44, 265–274.

- Sorrentino, A.; Gorrasi, G.; Tortora, M.; Vittoria, V. Barrier properties of polymer/clay nanocomposites. In Polymer Nanocomposites; Mai, Y.-W., Yu, Z.-Z., Eds.; Elsevier: Cambridge, UK, 2006; pp. 273–296. ISBN 978-1-85573-969-7.

- Sorrentino, A. Nanocoatings and ultra-thin films for packaging applications. In Nanocoatings and Ultra-Thin Films; Makhlouf, A.S.H., Tiginyanu, I., Eds.; Elsevier: Oxford, UK, 2011; pp. 203–234. ISBN 9781845698126.

- La Noce, M.; Paino, F.; Spina, A.; Naddeo, P.; Montella, R.; Desiderio, V.; De Rosa, A.; Papaccio, G.; Tirino, V.; Laino, L. Dental pulp stem cells: State of the art and suggestions for a true translation of research into therapy. J. Dent. 2014, 42, 761–768.

- Yang, X.; van der Kraan, P.M.; Bian, Z.; Fan, M.; Walboomers, X.F.; Jansen, J.A. Mineralized Tissue Formation by BMP2-transfected Pulp Stem Cells. J. Dent. Res. 2009, 88, 1020–1025.

- Weiss, E.I.; Shalhav, M.; Fuss, Z. Assessment of antibacterial activity of endodontic sealers by a direct contact test. Dent. Traumatol. 1996, 12, 179–184.

- Stewart, P.S. Antimicrobial Tolerance in Biofilms. Microbiol. Spectr. 2015, 3.

- Stoodley, P.; Dodds, I.; Boyle, J.D.; Lappin-Scott, H.M. Influence of hydrodynamics and nutrients on biofilm structure. J. Appl. Microbiol. 1998, 85, 19S–28S.

- Zaltsman, N.; Ionescu, A.C.; Weiss, E.I.; Brambilla, E.; Beyth, S.; Beyth, N. Surface-modified nanoparticles as anti-biofilm filler for dental polymers. PLoS ONE 2017, 12, e0189397.

- Yao, Y.; Berg, E.A.; Costello, C.E.; Troxler, R.F.; Oppenheim, F.G. Identification of protein components in human acquired enamel pellicle and whole saliva using novel proteomics approaches. J. Biol. Chem. 2003, 278, 5300–5308.

- Größner-Schreiber, B.; Teichmann, J.; Hannig, M.; Dörfer, C.; Wenderoth, D.F.; Ott, S.J. Modified implant surfaces show different biofilm compositions under in vivo conditions. Clin. Oral Implants Res. 2009, 20, 817–826.

- Thomas, W.E.; Trintchina, E.; Forero, M.; Vogel, V.; Sokurenko, E.V. Bacterial Adhesion to Target Cells Enhanced by Shear Force. Cell 2002, 109, 913–923.

- Marquis, R.E. Antimicrobial actions of fluoride for oral bacteria. Can. J. Microbiol. 1995, 41, 955–964.

- Marquis, R.E.; Clock, S.A.; Mota-Meira, M. Fluoride and organic weak acids as modulators of microbial physiology. FEMS Microbiol. Rev. 2003, 26, 493–510.

- Sturr, M.G.; Marquis, R.E. Inhibition of proton-translocating ATPases of Streptococcus mutans and Lactobacillus casei by fluoride and aluminum. Arch. Microbiol. 1990, 155, 22–27.

- Guha-Chowdhury, N.; Iwami, Y.; Yamada, T. Effect of Low Levels of Fluoride on Proton Excretion and Intracellular pH in Glycolysing Streptococcal Cells under Strictly Anaerobic Conditions. Caries Res. 1997, 31, 373–378.

- Guha-Chowdhury, N.; Clark, A.G.; Sissons, C.H. Inhibition of purified enolases from oral bacteria by fluoride. Oral Microbiol. Immunol. 1997, 12, 91–97.

- Matsui, R.; Cvitkovitch, D. Acid tolerance mechanisms utilized by Streptococcus mutans. Future Microbiol. 2010, 5, 403–417.