Membrane phenomena in carious dissolution of the teeth

Abstract

Experiments are described that have been conducted to ascertain the role of Donnan membrane effects in carious dissolution of the mineral components of the tooth structures. When a solution of an ionized macromolecular substance is separated from another solution by a semipermeable membrane, which arrests the macromolecules but allows free passage to small ions from both sides, the latter are distributed over both solutions in a peculiar way. Under certain circumstances, depending on the net particle charge, a drop of the pH on one side of the membrane can be effected, accompanied by a rise of the pH on the other side. We applied this principle to the problem of carious tooth decalcification. It was possible to predict and obtain results in vitro that closely resemble actual caries, much more so than could be achieved until now with the use of buffered or unbuffered acids. Further experiments, partly still under way, strongly suggest that the beneficial effect of saliva on the tooth substance, mostly described as a mineralizing or remineralizing activity, may also be ascribed to a Donnan membrane effect, the macromolecular agent being salivary mucin.