Microbiologia En Odontologia

RESEARCH REPORTS
Biomaterials & Bioengineering

L. Cheng1,2, M.D. Weir1, K. Zhang1,3,
S.M. Xu1, Q. Chen2, X. Zhou2*,
and H.H.K. Xu1,3-5,*
1

Biomaterials & Tissue Engineering Division, Dept. of
Endodontics, Prosthodontics and Operative Dentistry,
University of Maryland Dental School, Baltimore, MD 21201,
USA; 2State Key Laboratory of Oral Diseases, West China
College of Stomatology,Sichuan University, Chengdu, China;
3
Dept. of Orthodontics, School of Stomatology, Capital
Medical University, Beijing, China; 4Center for Stem Cell
Biology & Regenerative Medicine, University of Maryland
School of Medicine, Baltimore, MD 21201, USA; 5Marlene
and Stewart Greenebaum Cancer Center, University of
Maryland School of Medicine, Baltimore, MD 21201, USA;
*corresponding authors,hxu@umaryland.edu and zhouxd@
scu.edu.cn

Antibacterial nanocomposite
with calcium Phosphate and
Quaternary Ammonium

J Dent Res 91(5):460-466, 2012

AbstrAct

Secondary caries is a frequent reason for restoration failure,
resulting from acidogenic bacteria and their biofilms. The
objectives of this study were to: (1) develop a novel nanocomposite containing nanoparticles of amorphouscalcium
phosphate (NACP) and quaternary ammonium dimethacrylate (QADM); and (2) investigate its mechanical and antibacterial durability. A spray-drying technique yielded NACP
with particle size of 116 nm. The nanocomposite contained
NACP and reinforcement glass fillers, with QADM in the
resin. Two commercial composites were tested as controls.
Composites were inoculated with Streptococcusmutans.
After 180-day water-aging, NACP+QADM nanocomposite
had flexural strength and elastic modulus matching those of
commercial controls (p > 0.1). NACP+QADM nanocomposite reduced the biofilm colony-forming units (CFU) by
3-fold, compared with commercial composites (p < 0.05).
Metabolic activity and lactic acid production of biofilms on
NACP+QADM were much less than those on commercialcomposites (p < 0.05). The antibacterial properties of
NACP+QADM were maintained after water-aging for 30,
90, and 180 d (p > 0.05). In conclusion, the novel NACPQADM nanocomposite greatly decreased biofilm metabolic
activity, CFU, and lactic acid, while matching the loadbearing capability of commercial composites without antibacterial properties. The NACP-QADM nanocomposite
with strong and durableantibacterial properties, together
with its previously reported Ca-PO4 release capability, may
render it useful for caries-inhibiting restorations.

KEY WOrDs:

antibacterial nanocomposite, amorphous calcium phosphate nanoparticles, Streptococcus
mutans, quaternary ammonium salt, stress-bearing, dental
caries.

DOI: 10.1177/0022034512440579
Received November 17, 2011; Last revisionJanuary 11,
2012; Accepted February 8, 2012
© International & American Associations for Dental Research

460

IntrODuctIOn

D

ental composites are increasingly popular because of their esthetics
and direct-filling capabilities (Ferracane, 2011). Extensive studies have
improved the fillers, resins, and handling and polymerization properties (Bayne
et al., 1998; Lim et al., 2002; Spencerand Wang 2002; Watts et al., 2003; Xu X
et al., 2006; Drummond, 2008). Nonetheless, composites accumulate more
biofilms/plaques than other restoratives (Zalkind et al., 1998; Beyth et al.,
2007). Plaques contribute to secondary caries, which is a main reason for
restoration failures (Deligeorgi et al., 2001). Replacing failed restorations
consumes 50 to 70% of dentists’ time. Replacementdentistry costs $5 billion/year in the USA (Jokstad et al., 2001). To combat caries, antibacterial
composites containing quaternary ammonium salts (QAS) were developed
(Imazato, 2003, 2009). Resins containing 12-methacryloyloxydodecylpyridinium bromide (MDPB) markedly reduced bacterial viability (Imazato et al.,
1994). Other antibacterial resins used agents including methacryloxylethyl
cetyl...