588 Theories and techniques of oral implantology

widening it to accept the post. Because of the various densities of the tissues to be penetrated, this stage is particularly dangerous in respect to instrument fracture. It should therefore be done with special care, starting with small diameter reamers and proceeding slowly, with frequent counterclockwise reversing, debridements, and irrigations to re-move the shavings and blood clots.

Another danger encountered at this stage is the tooth's turning or even being extracted by the rotational force of the reamer. This is particularly true in cases where the periodontium is very weak or has been extensively destroyed. If the tooth does move, the borehole in bone may be drilled in a wrong direction. If the borehole is made in a wrong direction, the tooth and hole in bone will be improperly aligned. Therefore loose teeth should be temporarily stabilized by some extraneous means. Usually a firm grip between the fingers will suffice, but other methods of fixation, such as pressing onto an existing denture, wire-looping, or splinting with composition-impression material, may prove necessary.

Small mistakes are sometimes unavoidable but can usually be corrected by spot-grinding. Teeth accidentally extracted by rotational forces during reaming are not necessarily lost; they can be reimplanted. Their sockets should be artificially deepened before reimplanting and stabilizing such teeth with endodontic implants to provide a better hold in the bone.

Once the hole in bone is created, the post is inserted to its base and its depth verified by an x-ray. At this stage, it is easy either to deepen the borehole or, if necessary, to retract the post from the deep end of the borehole. After a satisfactory depth has been determined, the new emergence point is marked on the post. The post is withdrawn, and a circular notch is ground slightly below the emergence point mark just deep enough to ensure an easy break in the last stage of the operation. The reason for notching the post below the last emergence mark is so that the pin will not protrude at the incisal edge or rest right at it. In notching the post, care must be taken not to cut too deeply; the post may break prematurely, making it difficult to set the implant at the exact depth intended. On the other hand, if the notch is too shallow, too great a force will have to be used to break the post, and it may even be necessary to cut it with diamond disks. This could overheat the implant in the bone and would make proper filling of the trephined cavity impossible.

Sixth, bleeding from the borehole into the root canal must be arrested. Usually instilling 3 to 4 droplets of epinephrine solution (1:100) or Calyxl is effective, but firmly packing the foramen and the periapex with Kri paste invariably helps. After arresting the hemorrhage, the canal walls are throughly cleaned and dried with ether. Failure to do this endangers cementing the implant to the canal walls.

Seventh, the implant and canal are ready for cementing. The apex of the tooth has already been packed with Kri paste. If this has been done properly, it should prevent any cement from reaching the bone. Thin-flowing oxyphosphate of zinc cement is then pressed into the root canal with a Jiffy tube. That part of the implant to lie in bone is coated with a thin layer of Kri paste (and/or Ledermix paste), and that part to remain in the root canal is covered with a more sticky cement mix. The opera-tor can deduce from his two sets of markings which part will lie flush with the apex of the tooth. This section is coated with a nonsoluble endodontic cement, the rest with viscous oxyphosphate of zinc cement. The coated post is then quickly pushed into the borehole until the uppermost mark is slightly below the trephine opening. Heated, softened gutta-percha is used to press the cement firmly home between the stabilizer and the canal walls.

Eighth, a few moments before the cement sets, the surplus part of the stabilizer is broken at the circular notch and discarded. Then the gutta-percha is pressed further into the cavity, and any remaining space is filled with cement. Once the cement has set and the surface has been trimmed, the implantation is completed. The tooth is immediately stabilized, and its firmness will increase as bone reforms around the endodontic post.

With the stabilizer pin in place, the tooth is usually well protected against tongue thrusts and other buccolingual movements. However, Linkow feels that splinting the affected tooth is also necessary to protect it from lateral movements. A single pin has little retentive power in bone and acts only to improve the root-to-crown ratio. As a narrow post, it can also serve as a pivot, particularly if the tooth is very loose. For this reason, splinting is advised in most cases. Naturally, a multirooted tooth with more than one pin implant has less chance of being rotated, and splinting in such cases may be superfluous.

A more simplified implantation technique is that of Edelman and Linkow. This technique, instead of