Journal of Dental Research, Vol 68, 1337-1344, Copyright © 1989 by International & American Associations for Dental Research Online Journals
Substitutes for N-phenylglycine in adhesive bonding to dentin
A. D. Johnston, E. Asmussen and R. L. Bowen
Paffenbarger Research Center, American Dental Association Health Foundation, Gaithersburg, Maryland 20899.
Using bond strength measurements, we investigated a number of related
compounds in order to elucidate the role of the surface-active ingredient,
N-phenylglycine (NPG), in experimental two-step and three-step bonding
protocols resulting in adhesive bonding to dentin. All active compounds
identified for the two-step or the three-step protocol were
N-aryl-alpha-amino acids, and the results delineate some of the key
features of the NPG molecule for bonding. For the three-step protocol,
there was a requirement for a secondary or tertiary aromatic amino group, a
carboxylic acid group, and a single (secondary or tertiary) methylene unit
between those two functional groups of the amino acid. For the two-step
protocol, additional substitutions at the para position of the phenyl ring
on the amine improved the bond strength. In both protocols, para-methyl-
and para-chloro-substituted NPG analogues ranked higher than NPG. A
"catalytic" effect of the aromatic tertiary amino group on the
polymerization of the adhering resin in both procedures could not be ruled
out.
