The effect of canal preparation on the formation and leakage characteristics of the apical dentin plug.

The effects of canal preparation on the formationand leakage characteristics of the apical dentin plug were investigated. Seventy root canals in extracted human teeth were instrumented from one to five consecutive file sizes. The teeth were immersed in 45 Ca, sectioned, and autoradiographed to determine apical leakage. Several specimens were examined under the scanning electron microscope to determine the nature of the apical plug. There was a general trend for leakage to decreasewith a greater degree of canal preparation. The scanning electron microscope study showed the process of dentin plug formation was a gradual packing of particles of dentin into the apical region of the canal, usually over residual pulp tissue. As preparation continued, a greater proportion of hard tissue particles was generated in proportion to soft tissue. Instrumentation in the initial stages resulted in fibrous plugs which did not stop leakage.