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Title: 0516 - Reduction of the Intra-canal Post Strains by Increased Crown Ferrule

Authors:

Raphael Pilo (Presenter)
The Goldschleger School of Dental Medicine, Tel Aviv University

Zvi Metzger, The Goldschleger School of Dental Medicine, Tel Aviv University
Tamar Brosh, Tel Aviv University

Abstract:

Objectives: Cast post-core and crown are considered as the preferred treatment for anterior teeth with severe destruction. Our aim was to evaluate whether ferrule contributes to reduction of strains transferred to the intra-canal cast post.

Methods: The axial surfaces of 12 endodontically treated central incisors bovine teeth were reduced to 5mm and prepared for a full coverage metal crown with light chamfer finishing line. The intra-canal buccal and lingual surfaces of the cast post, fabricated by Ni-Cr alloy, were reduced by 0.4mm, to enable bonding of two miniature strain gauges (EA-06-031DE). Another identical two strain gauges were bonded on the buccal and lingual surfaces of the external surface of the root, in the same plane. The strain gauges were connected to the data acquisition system through the apex by three-wire quarter Wheatstone bridge circuit design. For each tooth 6 Ni-Cr full coverage cast crowns were fabricated covering 5mm core and either 5, 4, 3, 2, 1 or 0 mm of ferrule on tooth substance. Cementation of the cast post and core was done by ZPC. The teeth embedded in epoxy cylinders were inserted to an adjustable loading apparatus and the cemented crown was loaded at angulations of 45° till 100N. After each experiment the crown was removed by gentle cutting and a new crown with a different amount of ferrule was tested.

Results: The strains on both the post and root linearly increased with the load (r>0.94, p<0.01). The strains at the intra canal post were ±165-185µs, ±227-239µs, ±253-261µs, ±277-285µs, ±366-380µs and ±587-625µs at 5, 4, 3, 2, 1 and 0mm of ferrule respectively. The strains on the root were relatively constant (±400-470µs) for the same amounts of ferrule.

Conclusions: Crown ferrule has an important role in reducing the intra-canal strains transferred to the root by the post.

Disclosure Statement:
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: none

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