Advances in Dental Research, Vol 8, 307-311, Copyright © 1994 by International & American Associations for Dental Research
Calculus formation and inhibition
G. H. Nancollas and M. A. Johnsson
Department of Chemistry, State University of New York at Buffalo 14214.
The formation, development, and dissolution of hard deposits such as
calculus are complex processes that involve numerous calcium phosphate
phases as well as the interaction of these ions with organic molecules.
Although formation is determined by thermodynamic driving forces, kinetic
factors are also important determinants for the precipitation of specific
calcium phosphate phases. The overall process, therefore, may involve the
formation of metastable intermediates which may subsequently transform into
the more stable hard deposits observed in vivo. A knowledge of the kinetics
of growth of both individual calcium phosphate phases and their mixtures is
important for elucidating the mechanism of calculus formation. Although
salivary proteins are effective inhibitors of the mineralization reactions
that take place in dental plaque, once adsorbed, their conformation may
change to present surfaces that catalyze the nucleation of mineral phases.
The variable pH conditions in plaque, expressed in terms of free ionic
concentrations, will markedly alter the supersaturations with respect to
typical calcium phosphate precursor phases such as dicalcium phosphate
dihydrate (DCPD) and octacalcium phosphate (OCP). Physical-chemical studies
have shown that the mineralization of all the calcium phosphate phases is
controlled by reactions at the surface rather than by diffusion of lattice
ions through the contacting liquid phase. This makes the rates of reaction
very sensitive to ions and molecules in the solution that may absorb at the
active growth sites and, while not significantly incorporating into the
precipitated crystal phases, markedly influences the rates of
mineralization and demineralization.(ABSTRACT TRUNCATED AT 250 WORDS)
