Relation between length of fiber post and its mechanical retention

The aim of this paper is to verify how the length of the fiber post may influence its retention in an insertion site.

Forty double conicity posts were used: 20 were inserted in epoxy resin cubes, the other 20 were inserted in extracted teeth at 2 different depth (5 mm and 10 mm). The samples were tractioned by an Instrom machine registering the postsite detach value. The root canals were examined by SEM. Statistical evaluation was made using the t-test.

The results of the sample with resin cubes show a direct proportionality between the insertion length and the post retention. This relation was not appreciated in the sample which used extracted teeth: the differences between the 5 mm and 10 mm insertion are not statistically significant. The extracted posts observation show that the fixing cement stays on the post.

In ideal conditions the retention is directly proportional to the insertion length. The weakest interface of the adhesive system is the one between dentin and fixing cement.