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An experimental study of the adhesion of bacterial layers to some restorative dental materials.

In the present study a powerful method for measuring adhesion is introduced. It is based on the observation that the bacterial layer is usually capable of maintaining an interior pressure, but fractures when this pressure exceeds a certain critical value characteristic of the mechanical and adhesive properties of each specific bacteria and its formed matrix. A water jet from a nozzle was directed on the bacterial layer of the specimen. A specimen covered with a layer of Streptococcus mutans, grown in an artificial mouth, was placed on a sledge and displaced twice, at constant speed in front of the jet, thus forming two grooves in the plaque layer. When the grooves are made in parallel utilizing different water pressures, the critical pressure for causing disengagement of the plaque, pc, can be evaluated. It is claimed that pc gives an estimate of the plaque adhesion. Polished and ground surfaces of four materials were investigated, namely amalgam, PMMA, gold and porcelain-coated gold.