Journal of Dental Research, Vol 72, 1045-1049, Copyright © 1993 by International & American Associations for Dental Research Online Journals
Molar efficiency study of chlorinated NPG substitutes in dentin bonding
N. J. Miniotis, P. S. Bennett and A. D. Johnston
Naval Dental School, NNDC, Bethesda, MD 20814-5077.
This study evaluated and compared the contributions to dentin adhesive
bonding of three N-phenylglycine analogues with electron-withdrawing
substituents on the aromatic ring. These electron-deficient "N-compounds"
included: N-(4-chlorophenyl)-glycine (NCPG),
N-methyl-N-(4-chlorophenyl)-glycine (NMNCPG), and
N-(3,4-dichlorophenyl)-glycine (NDCPG). An experimental three-step
dentin-bonding protocol that consisted of sequential application of acidic
ferric oxalate solution, an N-compound in acetone, and a surface-active
comonomer in acetone was used. The first and third steps were held constant
throughout the study. Each N-compound (NCPG, NMNCPG, NDCPG) was used in
step two at ten concentrations ranging from 0.0 mol/L (pure acetone) to 5 x
10(-1) mol/L, depending on solubility. After overnight storage in distilled
water, the dentin-to-composite bonds were broken in tension. The data were
analyzed with ANOVA, and multiple comparisons were performed with Duncan's
Multiple Range test. All statistical tests were controlled at alpha = 0.05.
At 5 x 10(-3) mol/L, the relative effectiveness of the three N-compounds
(as measured by tensile bond strengths) was NMNCPG > NCPG > NDCPG. Of
all concentrations studied, the mean bond strengths produced with NMNCPG
were statistically as good as or better than those produced by the other
two compounds, and NCPG was always as good as or better than NDCPG.
Increased electron-withdrawing from the nitrogen of the amine group by the
substituents narrowed the effective concentration range for dentin bonding
and, in general, produced lower mean bond strengths between dentin and
composite.
