|Case of the Month
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July 2001 – Abuse of the Post Space
The purpose of a post is to retain core restorations when inadequate tooth structure remains. Posts and post space preparation are serious business. It is important to remember that posts have specific functions and that once they are placed, they can be difficult to remove in many cases.
July's cases of the month deals with what happens when the post and the post space are abused. Fig. 1 shows two mandibular anterior teeth with attempted endodontic treatment. There is a diffuse radiolucent lesion associated with both teeth. Endodontic treatment in the right central incisor is grossly short of the apex. Most significantly, the crowns of both teeth are intact. Nevertheless, the dentist has chosen to place posts in the accesses of both canals rather than merely restoring the accesses with a composite. In essence, these posts are nothing more than "Intra-Dentinal Implants". It is post space abuse. Not only do these posts have no function, they serve to make it much more difficult to perform conventional endodontic retreatment.
In many parts of the world, placement of posts is considered by insurers to be "basic dentistry" i.e./ covered at the same rate as an amalgam. As such, there is an unfortunate financial incentive for dentists to place them, even though they are not indicated. At worst, it indicates a total disdain for proper treatment. At best, it represents a fundamental lack of understanding of the role and function of the post.
Until relatively recently, these cases were often doomed to surgery. Attempted removal of the posts often involved use of slim diamond burs and troughing around the posts in an attempt to remove them with small forceps. This often necessitated removal of large amounts of dentin, weakening the tooth and compromising its integrity. More recently, ultrasonics and special post pulling devices have made the job much easier but it still requires extra effort and expense that is needless.
Figure 2. represents a different kind of post space abuse. This case was referred to me to see if I could salvage the maxillary cuspid. It was the mesial abutment of a four unit posterior bridge. Contrary to proper procedure, the post space was prepared with motorized Peeso reamers. The axis of the post space preparation bore no resemblance to the root axis and gross perforation occurred. The patient was desperate to keep the bridge. The referring dentist told me that the original treating dentist has surgerized the tooth on two previous occasions in attempt to salvage the case. Both times, it appeared that no retrofilling material had been placed. The post had merely been resected to the level of the root face and the area curretted. The perforation and subsequent surgical procedures had now caused a deep pocket and chronic periodontal defect.
At this point a third surgery was possible but even if we managed to access the area of the post perforation ( hopefully more buccal than palatal) and place a retrofilling that sealed the post perforation, there was no guarantee that the post space would not leak from the area of the crown margin and cause another failure. This is especially true when we are not sure of the quality (?!) of the crown margin seal.
I suggested that the area be evaluated for possible implant treatment rather than continuing to try to deal with a situation that has a poor prognosis. What is more remarkable to me is that the original treating dentist would have the nerve to cement such an extensive bridge in the first place, knowing full well that the perforation had occurred and that failure was imminent.
Post space preparation is a critical step in the restoration of endodontically treated tooth.
- Posts should be placed only when inadequate tooth structure remains to retain a core.
- When considering post placement, serious consideration should be given to the quality of the endodontic treatment. Once a critical abutment post has been cemented, retreatment of the case very often means surgery. When in doubt, retreat the endodontics BEFORE the post is placed.
- Post spaces are most safely prepared by removing gutta percha with heat and Gates Glidden burs. If a parallel sided post must be placed, hand reamers or post drills should be USED WITHOUT AN ENGINE to guard against possible perforation.