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Case of the Month

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May 2004Mesial Post Placement in Mandibular Molars - A Good Idea?

May's Case of the Month deals with a case that had endodontic treatment completed in my office almost 10 years ago. Because the tooth was to be restored with the recommended cuspal coverage, a post space was prepared in the distal canal. In the report that is issued with all of my completed cases, I indicate the canal that has been prepared, the post space length and the reference point.

(More recently I have begun placing UltraDent's PermaFlo Purple Flowable composite over the other orifices rather than a tooth colored composite as I had in the past. This serves to enhance the coronal seal as well as discouraging the placement of posts in these covered canals. In the event that the dentist STILL wishes to place a post in one of these other canals, the bright purple material can be safely removed to the level of the canal orifice, exposing the gutta percha in the canal with a minimal risk of perforation.)

Fig. 1

The case had been completed in 1995. The patient was seen on recall at which time I noted that the tooth had been restored with post(s) and a full crown. Much to my dismay, I noted post placement in the mesial root, although I had clearly not made provisions for this in the endodontic treatment. A draining buccal sinus was noted to be present adjacent to the mesio-buccal midroot area. Careful periodontal probing of the area showed no obvious pockets. Pocket depths were within normal limits on all surfaces. Frank periapical pathology at the apices was absent. This was not a good omen.

Fig. 2

Tracing of the sinus showed it to originate at the midroot level of the mesial root adjacent to the level of the post. At this point the differential diagnosis included either a post perforation in the mesial root or mesial vertical root fracture. (Had the gutta percha cone traced to the furca area, there was a possibility that the mesial root could have a strip perforation due to the post placement. In that case, disassembly retreatment and attempted internal MTA repair would have been indicated.) However, the furca bone looked intact and the periodontal probing showed the furca was not involved.

Fig. 3

In any case the overall prognosis had to be downgraded. I explained to the patient that a surgical procedure would be necessary to determine whether the defect could be repaired. I was hoping for an accessible post perforation on the MB root face because I knew that had a reasonable chance of being repaired with MTA. The worst prognosis would occur with a vertical root fracture that was inoperable and doomed the tooth to extraction. My suspicions were that there was a vertical crack and I was not optimistic. Needless to say, after having spent the time and finances to restore the tooth, the patient was discouraged.

Fig. 4
Buccal View of Vertical Fracture along the Mesial aspect of the Mesial Root.

There is no way to tell when the fracture in this tooth occurred. It could have happened during the initial vertical compaction of the gutta percha but this is unlikely to occur if proper technique is used . ( i.e. Pluggers are NOT wedged against the dentin during the packing procedure.) if this was the case, it also would have shown up initially and not after 9 years.What we CAN say is that placement of a post in the mesial root of this molar was both unnecessary and likely caused stresses that either directly or indirectly led to the loss of this tooth.

Regrettably, there are still some locations where clinicians are paid "by the post" and therefore the use of the maximal number of posts is encouraged purely through financial incentive. Placement of posts in curved roots without regard to root anatomy, remaining dentin thickness and need needlessly risks eventual loss of the tooth by weakening of the dentin or outright perforation. This month's example shows a perfectly good treatment that will now necessitate placement of an implant.