FURTHER EXPERIMENTS WITH INTACT TEETH PLACED IN VARIOUS BUFFER SOLUTIONS

¹ B. Gottlieb Dental Polyclinic, Jerusalem, Israel

A gravimetric method was used for determination of loss of weight, in relation to time, of intact tooth, or powered enamel and dentin, and of enamel caps and roots of human intact teeth. The loss of weight follows an S-shaped curve.

Enamel caps bathed in lactic buffers of pH 3.95 for 15 minutes at room temperature, lose about 0.1 per cent of their weights. At higher levels of pH and in the so-called "lag period," the initial decalcification is almost insignificant. If the acid action is continuous, or at a lower pH-level, the loss of weight gradually increases, the curve assuming an exponential character.

Dentin is less resistant to decalcification by acids on account of its greater permeability, its greater number of organic channels and the smaller size of its apatite crystallites.

The gravimetric method with air-dried specimens has limited use since increased imbibition of the specimen through continued demineralization may lead to false determinations.

Experiments were especially designed to study the dissolution rate at short time intervals, instead of days. Such study was considered desirable, as it more closely approaches the clinical occurrence of dissolution of tooth structure in the oral cavity.

The separation of enamel and dentin and the establishment of a different rate of their solubility was given special consideration, as it bears on our evaluation of the different conceptions of the mechanism of caries.