New Antimicrobial Macromers for Dental Self-Etch Adhesives

Objectives:

Antimicrobial adhesives help to eliminate remaining bacteria after minimally invasive therapy. This pilot-study investigates trialkylammonium-oligo(oxazoline)-methacrylamides M2a and M2b of varying spacer-length as antimicrobial macromers in the two-component self-etching adhesive AdheSEŽ.

Macromer M2a (n=23; M=1914 M2b (n=55; M=3705 g/mol)

Methods:

Four experiments were conducted using the following formulations.

Exp.1 : Antimicrobial Activity
Experimental	Control
AdheSEŽPrimer+2.5wt.-%M2b (AP-2.5b)	AdheSEŽPrimer (AP)
AdheSEŽPrimer+5wt.-%M2b (AP-5b)	AdheSEŽPrimer (AP)
AdheSEŽBond+2.5wt.-%M2b (AB-2.5b)	AdheSEŽBond (AB)
AdheSEŽBond+5wt.-%M2b (AB-5b)	AdheSEŽBond (AB)
Exp.2 : Storage-Stability (42°C)
AP-2.5a	AP+AB
AP-2.5b	AP+AB
Exp.3 : Comparison of antimicrobial activities
AB-5b	AB
AB+5wt.-% MDPB (AB-M)	AB
AB+5wt.-% Q-DAPMAA (AB-Q)	AB
Exp.4 : Leaching-Resistance
GDMA+HEMA+M2a (22.3+77+3.7 wt-%)(GH-a)	not applicable
GDMA+HEMA+MDPB (22.3+77+3.7 wt-%)(GH-M)	not applicable

Exp.1) Each combination of experimental versus control formulation was applied onto one glass slide, spray-inoculated with S.mutans (ATCC, strain 25175), incubated under agar (24h/37°C) and stained with 2,3,5-triphenyltetrazoliumchloride to determine colony-forming-units (CFU).

Exp.2) Shear-bond-strength (SBS) (ISO/TS-11409, n=5) of AP-2.5a and AP-2.5b stored at 42°C to bovine dentin was determined using AB and Tetric EvoFlow composite.

Exp.3) Activity of AB-5b against S.aureus (ATCC, strain 25923) was compared to that of N-pyridinium-10-hydroxydecyl-methacrylate (MDPB) in AB-M or N-dodecyl-N,N-dimethyl-N'-(3-propylammonium)-methacrylamide (Q-DAPMAA) in AB-Q.

Exp.4) A glass slide coated with GH-a or GH-M was washed with phosphate buffer at 25°C for 4 and 7 days and activity against S.mutans determined as in experiment 1.

Results:

Exp.1
sample	CFUxcm-2	control	CFUxcm-2
AP-2.5b	6	AP	35
AP-5b	0	AP	58
AB-2.5b	6	AB	74
AB-5b	4	AB	75
Exp.2
weeks@42°C	SBS [MPa]
	AP-2.5a	AP-2.5b	AP+AB
0	18.4±1.7	19.3±1.9	19.4±4
4	17.3±4.3	22.4±4.5	21.2±4
8	18.8±1.5	19.0±2.4	19.9±1.8
Exp.3
sample	CFUxcm-2	control	CFUxcm-2
AB-5b	0	AB	>>100
AB-M	33	AB	76
AB-Q	>>100	AB	>>100
Exp.4
days of washing		CFUxcm-2
		GH-a	GH-M
4		0	>>100
7		0	>>100

Conclusions:

In-vitro experiments with trialkylammonium-oligo(oxazoline)-methyacrylamides showed M2a and M2b's applicability as potent antimicrobial agents in self-etching adhesive formulations.