[Antibacterial effects of a dental adhesive incorporating a quaternary ammonium monomer against Streptococcus mutans]

OBJECTIVE

To incorporate an antibacterial monomer, methacryloxylethyl cetyl dimethyl ammonium chloride(DMAE-CB), into a dental adhesive, and to evaluate the antibacterial activity against Streptococcus mutans (Sm) of this DMAE-CB-incorporated adhesive after being cured.

METHODS

DMAE-CB was incorporated into a dimethacrylates-based dental adhesive as experimental group. The adhesive without DMAE-CB served as a negative control. Thirty-nine specimens were fabricated for each group. The effects of the cured adhesives on the growth and adherence of Sm were evaluated with growth inhibition assay and spectrophotometry respectively. The influence of aging treatment and saliva treatment on the antibacterial efficiency of the modified adhesive was evaluated. Moreover, the bacterial growth of Sm in the eluents of two different adhesives was examined.

RESULTS

Compared with negative control, the cured DMAE-CB-incorporated dental adhesive exhibited inhibitory effect on the growth and adherence of Sm. The inhibition rate was 99% and the absorbance value was (0.332 +/- 0.063) for experimental group, significantly lower than that of negative control (0.434 +/- 0.093, P = 0.021). Moreover, after aging treatment the DMAE-CB-incorporated adhesive could still inhibit the growth and adherence of Sm; the inhibition rate was 99%, and the absorbance value of experimental group was (0.372 +/- 0.062), significantly lower than that of negative control (0.455 +/- 0.066, P = 0.022). After saliva treatment the DMAE-CB-incorporated adhesive could still inhibit the growth and adherence of Sm; the inhibition rate was 90%, and the absorbance value of experimental group was (0.299 +/- 0.061), significantly lower than that of negative control (0.370 +/- 0.068, P = 0.045). However, the eluent of DMAE-CB-incorporated adhesive didn't show inhibitory effect on the growth of Sm when compared with negative control, and the antibacterial effect and the doubling time of experimental group [(130.5 +/- 8.4) min] had no statistical difference than negative control [(126.4 +/- 7.0) min, P = 0.298].

CONCLUSIONS

The incorporation of DMAE-CB can render the dental adhesive with antibacterial activity after polymerization via influencing the growth and adherence of Sm.

On the effect of ammonium and lithium ions upon frog nerve deprived of sodium

An analysis has been made of the effect of ammonium and of lithium ions upon frog nerve deprived of sodium. Ammonium ions cannot substitute for sodium ions and restore the excitability of the nerve fibers; nor can they increase the L fraction of the membrane potential and the efficiency of the nerve reaction. Certain observations, however, indicate that the presence of ammonium ions outside the nerve fibers may delay the development of inexcitability in a sodium-free medium of nerve fibers restored by a moderate amount of sodium ions. Lithium ions can substitute for sodium and restore to nerve fibers of the A and C groups the ability to conduct impulses; the effect upon B fibers has not been investigated. Lithium cannot substitute for sodium in the role that sodium plays in the creation of the L fraction and in the establishment of the nerve reaction. In this respect lithium and sodium have opposite effects. This fact establishes an important difference between the two physiological responses that the nerve fibers can produce, the nerve impulse and the nerve reaction. With untreated nerve the depolarization of nerve by lithium ions at high concentrations is preceded by a phase of hyperpolarization; with nerve deprived of sodium the depolarization begins without delay.

The pharmacological actions of (m-hydroxyphenethyl) trimethylammonium (leptodactyline)

Leptodactyline is a naturally occurring quaternary ammonium base, which is found in large amounts in the skin of some South American amphibians of the genus Leptodactylus. It is the first example of a m-hydroxyphenylalkylamine in the living organism. In vertebrates it had powerful nicotinic actions and a marked neuromuscular blocking effect. This was considered, on the basis of experimental evidence, to be of the "depolarizing" type.