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JOURNAL OF ENDODONTICS
VOL 9, NO. 10, OCTOBER 1983
Copyright 9 1983 by the American Association of Endodontists
Retrograde Instrumentation and Obturation of the Root Canal Space Kenneth S. Serota, DDS, and Alvin Arlen Krakow, DDS
a barrel, a screw-type plunger, a set of wrenches, and an assortment of needles ranging from 18 to 30 gauge (Fig. 2).
A treatment approach is described combining retrograde biomechanical instrumentation with retrograde obturation of the root canal space prior to insertion of a retrograde filling material in the apical terminus of the canal.
FLAP DESIGN The basic principles of flap design must be utilized. However, this method requires ample visibility and access to the root end so that the flap should be more extensive than usual, as shown in Fig. 3A.
Conventional endodontic therapy is not feasible in teeth with inaccessible root canal spaces. Examples of this situation include (a) canals with cemented posts; (b) canals with calcific obstruction or obliteration; (c) canals with separated instruments; (d) abutments with short clinical crowns where conventional access would result in loss of retention; and (e) canals with iatrogenic ledging or perforation where the main canal consequently cannot be renegotiated. Surgical endodontics is the treatment of choice is these situations. Krakow and Berk (1) developed a method utilizing the Endodontic Pressure Syringe to deposit sealer into the root canal from the retrograde approach prior to insertion of the apical amalgam or alternate retrograde sealing material. Such deposition of sealer is desirable since it could be significant in teeth that have lateral canals and/or accessory canals and are involved both endodontically and periodontally. Theoretically, retrograde deposition of sealer would be further enhanced by prior retrograde instrumentation of the root canal space which would eliminate much of the contaminants contained within the space. This article deals with an approach where both biomechanical instrumentation and obturation are accomplished from the retrograde approach. The technique is illustrated in a case where retrograde biomechanical preparation could be attempted because of prior bone destruction and favorable anatomical conditions (Fig. 1).
INSTRUMENTATION The root end is beveled in the usual manner in order to relocate the apical terminus onto the buccal slope. The ease of introduction of an instrument into the pulp chamber via the apical approach (Fig. 3A) is influenced by (a) the height of the bone in relation to the length of the root; (b) the size of the canal, especially at its apical terminus; (c) the size of the osseous defect; and (d) the angulation of the tooth. A radiograph of the instrument in place is shown in Fig. 3B. Each instrument has to be curved with a semicircular configuration as shown in Fig. 4. The instrumentation is therefore limited to a push-pull motion since rotation is impossible because of anatomical limitations. Accordingly, K-type files are indicated and utilized in a typical sequence. An instrument larger than standardized # 4 0 can tear the apical opening, unless the apex is incompletely formed.
PRESSURE SYRINGE NEEDLE SELECTION One of the smaller needles is gradually curved into a half-circle (Fig. 5A) and is inserted into the root canal as far as possible through the apical terminus and radiographed in place (Fig. 5B). Most frequently the largest needle that can be introduced in this manner is a 27-gauge needle. On occasion it is possible to introduce a larger 25-gauge needle, but more often it is necessary to use a smaller 30-gauge needle.
ARMAMENTARIUM The combined approach involves the use of K-type endodontic files and the endodontic pressure syringe. The Endodontic Pressure Syringe, which was designed and developed by Greenberg (2), consists of
LOADING THE SYRINGE The pressure syringe should be completely disassembled, and the sealer is mixed to a putty-like con448
Vol. 9, No. 10, October 1983
FIG 1. A, Preoperative photograph of clinical case that was treated with a technique that combines both instrumentation and obturation of the root canal space from the retrograde approach. B, Radiograph of same case which shows radiolucency associated with necrotic pulp in a mandibular first bicuspid.
Root Canal Space
FiG 3. A, Photograph showing incision line and reflected flap. A Ktype file has been placed in the root canal through the apical foramen. Note that the flap extends several teeth anterior to the tooth being treated. Also note the extensive periapical and periodontal bone destruction. B, Radiograph showing a K-type file placed in the root canal space through the retrograde approach.
FiG 2. Photograph of the unassembled pressure syringe showing the screw plunger, barrel, wrench, and an assortment of needles of gauges from 18 to 30.
FIG 4. Photograph of a K-type file that has been curved with the use of a hemostat in preparation for its retrograde introduction into the root canal space.
Serota and Krakow
Journal of Endodontics needle, filling the hub again, and repeating the procedure. The closed end of the wrench is slipped onto the barrel, with the bend away from the patient's mouth, to act as a handle (Fig. 7). The screw-type plunger is inserted and turned until some sealer appears at the needle tip (Fig. 8). D E P O S I T I O N OF SEALER The needle is reinserted through the apical terminus to its original position. As the screw plunger is turned, the needle is gradually withdrawn until the entire canal is filled (Fig. 9). As the sealer is deposited, the back pressure of the sealer against the needle tends to push the needle out of the canal. INSERTION OF APICAL A M A L G A M OR A L T E R N A T E FILLING MATERIAL The instrumentation of the canal tends to create a recess in the area of the foramen. The retention created by this recess should be further enhanced by undercutting with a #1/4 round bur. Amalgam is most frequently used to seal this apical preparation (Fig. 10). Injection-molded thermoplasticized gutta-percha has also been utilized as an alternate approach.
FIG 5. A, Photograph of pressure syringe needle curved with the use of a hemostat to permit retrograde access to the root canal space. B, Radiograph of pressure syringe needle placed into the root canal space for the retrograde approach. Note that it extends all the way into the chamber.
FIG 7. Photograph showing the wrench with the closed end over the syringe barrel. Note that the wrench bends away from the needle (and consequently from the patient during insertion).
FIG 6. Photograph showing complete loading of the pressure syringe needle hub with sealer. sistency. The hub of the needle is filled brimful (Fig. 6). In order to avoid trapping air, this is accomplished by incrementally pushing small amounts of sealer along one side, down to the depth of the hub, until it is completely backfilled. The needle is screwed onto the syringe barrel, displacing the sealer from the hub of the needle into the lumen of the barrel. Additional sealer can be inserted into the barrel by removing the
FiG 8. Photograph showing sealer being extruded from the tip of the needle.
Root Canal Space
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FIG 9. Radiograph showing root canal obturated with sealer w h i c h was deposited in a coronal to apical direction from the r e t r o g r a d e approach.
FIG 1 0. R a d i o g r a p h showing closure of the apical preparation with amalgam.
Schacter and Cappuccino (in a personal communication) have reported that the adaptation of the guttapercha to the walls of the canal at the apical terminus appears to be comparable to the adaptation of the amalgam, when evaluated by scanning electron microscopy.
quate surgical accessibility is a preequisite for this approach. More access is required for retrograde biomechanical instrumentation than for retrograde obturation. Surgical accessibility may be inadequate in certain molars, particularly with palatal roots of maxillary molars.
DISCUSSION Seltzer and Bender (3), Simon et al. (4), and Langeland et al. (5) have indicated that the existence of lateral canals, accessory canals, and/or communications from the pulp chamber to the furcation in multirooted teeth can be important factors which affect the success rate for conventional endodontic treatment. Yet in situations where surgical endodontics must be utilized, these anatomical complexities of the root canal system are not usually addressed. Biomechanical instrumentation and obturation of the canal accomplished from the retrograde approach prior to insertion of a retrograde seal should enhance the success rate of surgical endodontic treatment. Ade-
Dr. Kenneth Serota is a staff associate in dentistry at the University of Toronto, and a staff associate in endodontics, Forsyth Dental Center. Dr. Alvin Arlen Krakow is an associate clinical professor in endodontics and chairman, Department of Endodontics at Harvard School of Dental Medicine, and a staff associate and chairman, Department of Endodonfics at Forsyth Dental Center.
References 1. Krakow AA, Berk H. Efficient endodontic procedures with the use of the pressure syringe. Dent Clin North Am 1965;9:387-99. 2. Greenberg M_ Filling root canals in deciduous teelh by an injection technique. D Digest 1961 ;67:574-5. 3. Seltzer S, Bender lB. The interrelationship of pulp and periodontal disease. Oral Surg 1963; 16:1474-90. 4. Simon JHS, Glick D, Frank AL. The relationship of endodontic-periodontic lesions. J Periodont 1972;43:202-8. 5. Langeland K, Rodrigues H, Dowden W. Periodontal disease, bacteria, and pulpal histopathology. Oral Surg 1974;37:257-70.