The present invention relates to an endodontic core assembly. Endodontic core assemblies are used in providing a core or anchor for an artificial tooth or the like. The core is usually integral with a post which is normally adapted to be inserted in and fixedly secured to the root canal of a tooth, the root canal usually requiring a preliminary preparation by a reamer.
Since the core is normally exposed to very substantial loads both torsional and flexing, it is very important that the post be embedded within the root canal as firmly as possible. Three basic systems are known for this purpose: The first system is a threaded post, which is usually combined with a suitable cement to secure a firm hold within the root canal. The second known system is a frictional arrangement which is somewhat similar to the threaded system in that the side walls of the root canal are frictionally engaged by the post and the overall bond is further improved by the use of cement. The third known system is so-called cemented system in which the post is made such as to be relatively loose in the root canal and is secured to the root canal walls solely by a suitable cement filling the space between the canal and the post.
Of the above-mentioned three systems, the threaded and frictional system are disadvantageous in that they require a relatively substantial pressure to be exerted upon the inside wall of the root canal engaged by the post. Such forces are directed generally radially outwardly and may result in undesired damage to the root canal which in turn, may give rise to reduced strength of the overall hold of the post (and thus the core) in the root canal.
From the standpoint of avoiding excessive radial pressures on the root canal walls, the cemented arrangement appears to be better advantaged than the first two since there is no active pressure exerted upon the walls of the canal. On the other hand, the canal being usually somewhat conical and usually decreasing in width with the increasing depth of the canal, the problem is to provide a reasonably strong hold by merely the cementing of the post within the prepared root canal. In practice, the cemented version therefore suffers from the drawback of a reduced strength of the anchoring of the post within the canal, the reduction in the strength of the hold being a trade-off for the elimination of the undesired radial stress to which the root canal is subjected with the first two systems. The present invention relates to the third mentioned group, i.e. to the cemented systems.