Materials Science Cement Distribution and Bond Strength in Cemented Posts

Abstract

Rods of lucite were drilled to receive a #5 parapost to a depth of 4 mm and 7 mm. Posts were fitted and cemented either by coating the post with cement or by placing the cement in the prepared hole with a lentulo spiral in a low-speed hand-piece and then inserting the pre-coated post. Photographs were taken to determine the distribution of the cement. The lentulo spiral distributed the cement along the entire length of the preparation, but coating alone did not distribute the cement evenly.

The tensile strength with these two methods of post cementation was also compared in four groups of extracted teeth. In Groups IA and IIA, the post preparation was rinsed with 2 ml of 5.25% NaOCl and dried with paper points and blasts of air. In Group IA, the post was coated with zinc phosphate cement and seated. In Group IIA, the cement was placed into the post space with a lentulo spiral in a slowly rotating hand-piece; the post was then coated and seated. In Groups IB and IIB, the post preparation was rinsed with 1 ml of 17% Na2 EDTA followed by 1 ml of 5.25% NaOCl to remove the smeared layer at the dentin-cement interface. The posts were then cemented as in IA and IIA. Under the conditions of this experiment, the following conclusions can be drawn:

(1) Placing cement into the preparation with a lentulo spiral increased the tensile strength and the overall cement distribution.

(2) Removing the smeared layer increased the tensile strength, whether the post was simply coated with cement or cemented into place using a lentulo spiral.

(3) The greatest tensile strength occurred when the smeared layer was removed and the post was cemented into place using a lentulo spiral and coating combination.

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