In recent years, various types of core crown prostheses that are full coverages on the cast core in the anterior teeth of edentulous patients have been increasingly used.
As compared with previous post crown prostheses, the two stage system by means of cast core technique makes it possible to retain part of vital teeth depending upon the degree of their decay and a firm retention can be expected as a result. Further, it is established that repair of the damage of prostheses is relatively easy and the equilibrium relationship between the abutment teeth in crown and bridge dentistry can be simply made, the clinical merit of this cast core technique being highly regareded for these reasons.
Studies on castcore technique, however, are maninly confined to the method of its manufacture and research from a dynamic point of view is yet scanty. Since the crown prostheses by cast core technique determines different forms of cast core in accordance with the residual amount of natural crown substance, it is highly important froma clinical standpoint to examine what influence would be brought about by this residual crown on abutment teeth. Few studies have been published based on the two-dimensional photoelastic experiment to the knowledge of the author. But this kind of study does not led itself to adequate clinical assessment because of the fact that it is conducted on a two-dimensional plane and, therefore, a three-dimensional analysis of cast core technique is desirable.
In the present study, the author was concerned with a three-dimensional photoelastic experiment of theeffect of cast core on the abutment teeth as their foundation in the anterior teeth of edentulous patients from a dynamic point of view.
Efforts were directed to the treatment of inferiority of residual crown substance in terms of structural and physical considerations.
At the same time, a comparison was made between one stage system and two stage system prostheses together with possible effect of crowns on the abutment teeth in the case of medullated teeth.
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