title: Effects of quaternary ammonium chain length on the antibacterial and remineralizing effects of a calcium phosphate nanocomposite.
abstract: Composites containing nanoparticles of amorphous calcium phosphate (NACP) remineralize tooth lesions and inhibit caries. A recent study synthesized quaternary ammonium methacrylates (QAMs) with chain lengths (CLs) of 3-18 and determined their effects on a bonding agent. This study aimed to incorporate these QAMs into NACP nanocomposites for the first time to simultaneously endow the material with antibacterial and remineralizing capabilities and to investigate the effects of the CL on the mechanical and biofilm properties. Five QAMs were synthesized: DMAPM (CL3), DMAHM (CL6), DMADDM (CL12), DMAHDM (CL16), and DMAODM (CL18). Each QAM was incorporated into a composite containing 20% NACP and 50% glass fillers. A dental plaque microcosm biofilm model was used to evaluate the antibacterial activity. The flexural strength and elastic modulus of nanocomposites with QAMs matched those of a commercial control composite (n = 6; P > 0.1). Increasing the CL from 3 to 16 greatly enhanced the antibacterial activity of the NACP nanocomposite (P < 0.05); further increasing the CL to 18 decreased the antibacterial potency. The NACP nanocomposite with a CL of 16 exhibited biofilm metabolic activity and acid production that were 10-fold lesser than those of the control composite. The NACP nanocomposite with a CL of 16 produced 2-log decreases in the colony-forming units (CFU) of total microorganisms, total streptococci, and mutans streptococci. In conclusion, QAMs with CLs of 3-18 were synthesized and incorporated into an NACP nanocomposite for the first time to simultaneously endow the material with antibacterial and remineralization capabilities. Increasing the CL reduced the metabolic activity and acid production of biofilms and caused a 2-log decrease in CFU without compromising the mechanical properties. Nanocomposites exhibiting strong anti-biofilm activity, remineralization effects, and mechanical properties are promising materials for tooth restorations that inhibit caries.
authors.affiliation: Department of Orthodontics, School of Stomatology, Capital Medical University, Beijing, China.|Biomaterials & Tissue Engineering Division, Department of Endodontics, Periodontics and Prosthodontics, School of Dentistry, University of Maryland, Baltimore, USA.
authors.forename: Ke
authors.initials: K
authors.lastname: Zhang
authors.affiliation: Biomaterials & Tissue Engineering Division, Department of Endodontics, Periodontics and Prosthodontics, School of Dentistry, University of Maryland, Baltimore, USA.|State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Cheng
authors.affiliation: Biomaterials & Tissue Engineering Division, Department of Endodontics, Periodontics and Prosthodontics, School of Dentistry, University of Maryland, Baltimore, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Weir
authors.affiliation: Department of Orthodontics, School of Stomatology, Capital Medical University, Beijing, China.
authors.forename: Yu-Xing
authors.initials: YX
authors.lastname: Bai
authors.affiliation: Biomaterials & Tissue Engineering Division, Department of Endodontics, Periodontics and Prosthodontics, School of Dentistry, University of Maryland, Baltimore, USA.|Center for Stem Cell Biology & Regenerative Medicine, School of Medicine, University of Maryland, Baltimore, USA.|Department of Mechanical Engineering, University of Maryland, Baltimore County, USA.
authors.forename: Hockin H K
authors.initials: HH
authors.lastname: Xu
mesh_terms: D000900:Anti-Bacterial Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D058491:Bacterial Load / Q000187:drug effects; D018441:Biofilms / Q000187:drug effects*; D002130:Calcium Phosphates / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D015169:Colony Count, Microbial; D003188:Composite Resins / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D055119:Elastic Modulus; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D053761:Nanocomposites / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D012463:Saliva / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents; D002130:Calcium Phosphates; D003188:Composite Resins; D008689:Methacrylates; D000644:Quaternary Ammonium Compounds; C519480:amorphous calcium phosphate