An investigation into the retentive strength of coronal-radicular post and cores placed into the unmodified root after cleaning and shaping in accordance with the BU technique
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Abstract
Retention of a coronal restoration is one of the primary, and perhaps most significant functions served by a post and core. Over the past three decades a multitude of techiques and post systems have been proposed which enhance the retentive values, but little uniformity or agreement has been achieved.
The literature describes a wide range of retentive values for various post and core systems. Frequently ignored is the fact that strength or resistance in one dimension is sacrificed to increase the retentive component. At present, none of the many researchers in this field specifically state what retentive force is required to achieve clinical significance.
Ninety recently extracted, single rooted teeth were selected for this study. Endodontic therapy was performed as dictated by the Schilder Technique and then the crown were sectioned at the cemental-enamel junction. A post space seven millimeters in depth was prepared by removing only gutta percha. In this fashion, the maximum inherent strength of the root was maintained.
Four post systems were then placed: 1) entirely amalgam, 2) entirely glass ionomer, 3) a Unitek endopost passively placed with glass ionomer as a cementing agent, and
4) a Unitek endopost passively placed with zinc phosphate cement as the luting agent.
The prepared teeth were then tested to a point of failure with an Instron Hodel 1122 machine.
The results of this investigation indicate that the most retentive system was the Unitek endopost cemented with zinc phosphate cement, followed by the amalgam post and core, the Unitek endopost cemented with glass ionomer and lastly the glass ionomer post and core.
The following conclusions were drawn:
1) Retention can be gained without further modification of the canals prepared with the Schilder Technique.
2) A passively placed Unitek endopost cemented with zinc phosphate cement proved to be most retentive, with glass ionomer posts the weakest.
3) These post systems would not further compromise the inherent strength of the root after completion of the endodontic therapy, as no additional dentin was removed.
4) To fully assess the usefulness of these post and core systems, cast crowns should be prepared, placed and then tested for retentive and shear strength.
Description
Thesis (MSD) --Boston University, Henry M. Goldman School of Graduate Dentistry, 1986 (Endodontics).
Includes bibliography (leaves 180-197).
Includes bibliography (leaves 180-197).
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This work is being made available in OpenBU by permission of its author, and is available for research purposes only. All rights are reserved to the author.