Self-limiting caries therapy with proteolytic agents.

Purpose: To determine the extent to which artificial carious dentin can be removed by agents that do not seem to attack sound dentin such as pepsin, trypsin, collagenase and NaOCl, and to evaluate the effect of the enzyme pepsin and a new enzymatic solution SFC-V (pepsin in mild acidic buffer) as a self-limiting caries therapy in deep dentin carious lesions using our new model for artificial dentin caries.

Methods: Artificial dentin caries was used to investigate different proteolytic agents which have the potential to remove carious tissue. 408 slices of coronal dentin were subjected to a demineralization regime which produces dentin caries very similar to natural lesions: acetic acid (pH 5) or lactic acid (pH 4) were used (7 days). Subsequently, sodium hypochlorite, collagenase, trypsin and pepsin were dissolved each in a suitable buffer and the demineralized dentin was treated for 10 minutes or 24 hours with these solutions. To differentiate the influence of the acidic buffer in case of pepsin, a second experiment was performed. 192 slices were exposed to lactic acid for 1 week. Subsequently the demineralized dentin surfaces were treated with either the enzyme pepsin in its acidic buffer, the acidic buffer alone, and in addition a neutral buffer as a control. In addition a fourth group was added where a new enzyme-based solution SFC-V was used. This second experiment differentiated further the influence of "diffusion enhanced by agitation" versus "diffusion" alone. The application time of the solutions was 3 minutes with and without agitation using a stiff nylon brush. To obtain information on the morphology of the pre- and post-treatment dentin surfaces, high resolution FE-SEM was used. Descriptive statistics were used based on cross tabulation of the morphological criteria.

Results: Lactic acid produced demineralized dentin covered with a surface layer removable by proteolytic enzymes while acetic acid produced only demineralized dentin. The amount of tissue removed with the current proteolytic agents ranked as follows: trypsin < pepsin < collagenase < NaOCl. The neutral and the acidic buffers did not affect the surface precipitates while the enzyme pepsin and the solution SFC-V were effective in removing the degraded organic matrix.