COAGGREGATION AND COAGGREGATION INHIBITION BETWEEN PERIO-PATHOGENIC AND CARIOGENIC BACTERIA

Objective To screen the coaggregating pairs between perio-pathogenic and cariogenic bacteria and to investigate the susceptibility of these coaggregations to inhibitors. Methods 4 strains of perio-pathogenic bacteria, Fusobacterium nuleatum （Fn） ATCC 10953, Actinobacilllus actinomycetem comitans （Aa） Y4, Porphyromonas gingivalis （Pg） ATCC 33277,Prevotella intermedia （Pi） ATCC 25261 and 4 strains of cariogenic bacteria, Streptococcus mutans （Sm） lngbritt, Streptococcus sanguis （Ss） 34, Actinomyces viscosus （ Av） 19246 and Lactobacillus acidophilus （La） ATCC 4356 were used to determine the coaggregating degrees of various combinations of the above bacteria by a visual assay and a turbidimetric assay. Then more than ＋ 2 （ or 20% ） coaggregation degrees＇ pairs were used to investigate the inhibitory effect of lactose and arginine and to identify the minimum of their coaggregation-inhibitory concentration. Results The coaggregation degrees of Fn-Av, Pg-Av, Fn-Sm, Fn-Ss, Fn-La and Pg-Ss pairs were higher than ＋ 2 （ 20% ）. 3.0 - 6.0mmol/L of arginine were considerably effective to the above pairs except Fn-Av pair and the disaggregation degrees were 49% - 92%. The maximum of their disaggregation degree to Fn-Av pair was just 18%. 120 - 300mmol/L of lactose were significantly effective to Pg-Ss pair, the disaggregation degrees were 57% - 91%. They partially inhibited Pg-Av pair and were almost ineffective to FnG^＋pairs. Conclusion The coaggregations between perio-pathogenic and cariogenic bacteria are highly specific. Most of them are relatively sensitive to arginine.

Effects of quaternary ammonium chain length on the antibacterial and remineralizing effects of a calcium phosphate nanocomposite

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 C/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.