JOURNAL OF E N D O D O N T I C S I VOL 7, NO 6, JUNE 1981
Clinical use of injection-molded thermoplasticized gutta-percha for obturation of the root canal system: a preliminary report Jay Marlin, DMD; Alvin Arlen Krakow, DDS; Roger P. Desilets, Jr., DDS; and Poul Grin, DMD
T h e t e c h n i q u e of i n j e c t i o n - m o l d e d t h e r m o p l a s t i c i z e d g u t t a - p e r c h a was a p p l i e d in vivo in a v a r i e t y of clinical cases. T e e t h w e r e b i o m e c h a n i c a l l y i n s t r u m e n t e d b e f o r e o b t u r a t i o n of the r o o t canal space. T h e r m o p l a s t i c i z e d g u t t a - p e r c h a was injected u s i n g a r e c e n t l y d e v e l o p e d d e l i v e r y s y s t e m . H e a l i n g in 125 cases w a s e v a l u a t e d on the basis of clinical a n d r a d i o g r a p h i c findings.
Gutta-percha has been used to obturate the root canal space effectively for more than 100 years.' Currently, the obturation techniques most commonly used involve lateral condensation, vertical condensation of warm gutta-percha, or gutta-percha softened by a solvent, such as chloroform. Recently, the technique of injection-molding was applied to thermoplasticized gutta-percha for the obturation of the root canal space by Yee and others 2 who instrumented teeth biomechanically using a standardized method. The teeth were then obturated with injected thermoplasticized gutta-percha, with and without sealer. Control teeth were obturated with lateral condensation of gutta-percha cones and AH-26 sealer with finger pluggers using the method described by Luks, a or with vertical condensation of warm gutta-percha and Kerr sealer using the technique originally described by Schilder? The quality of the seal obtained with the experimental method was
assessed by radiographs, visual examination of fillings recovered after the teeth were decalcified, and dye penetration techniques. The findings indicated that the experimental approach resulted in a sealing of the root canal space that was equal to or better than that resulting from the control techniques. The injection-molding method of obturating the root canal space was further evaluated by Torabinejad and others a using the scanning electron microscope to evaluate the interface between gutta-percha and dentin. The following obturation techniques were compared: obturation with injection-molded guttapercha; lateral condensation of gutta-percha cones; vertical condensation with warm gutta-percha; and obturation with chloropercha. The electron photomicrographs were inspected to determine the quality of the adaptation of the filling material to the root canal wall; the presence of voids; the extent and thickness of root canal sealer; and the reproduc-
tion of irregularities of the canal wall on the surface of the filling material. The findings confirmed the earlier observation that injection of thermoplasticized gutta-percha in conjunction with the sealer represents an effective approach to obturation of the root canal space in vitro.
Clinical use Some practical aspects of the experimental technique for the injection of thermoplasticized gutta-percha needed technical improvement and development before the method could be clinically applied. In the experimental technique, the source of heat was impractical, and there was no insulation of the delivery system to protect either the patient or the clinician. Herschowitz, Marlin, and Stiglitz ~;have recently developed a delivery system that overcomes these problems (Fig 1). The equipment consists of an injectionmolding syringe and an electrical control unit. The syringe consists of 277
several components. T h e barrel has an attached heating element and is insulated to minimize heat loss and to protect the patient and clinician. T h e syringe plunger is designed to prevent the backward flow of heated gutta-percha. The needles are specially designed (Fig 2) and available in gauges 18, 20, and 25. In the majority of the cases, the 25-gauge needle is used after the canal has been flared with no. 40 standardized instruments (Fig 3). T h e no. 20 and 18 gauge needles are used after instrumentation with no. 110 instruments, and in cases of incompletely formed or immature roots. T h e control unit regulates the current to provide the appropriate heat within the syringe. Different settings are used for various needle sizes to standardize the consistency of the extruded thermoplasticized guttapercha. T h e syringe is loaded from the rear with commercially available guttapercha cones. Any size cone that will fit into the syringe can be used. A needle is selected to properly fit the canal (Fig 3). A drop of sealer is wiped along the coronal half of the canal with a paper point. T h e sealer acts as a lubricant, which facilitates both the flow and the condensation of the gutta-percha. W h e n the guttapercha is sufficiently heated, it flows freely from the needle. T h e guttapercha is ready for injection when it is sticky enough to adhere to any surface and will string out to a thread-like strand. It should be noted that this test is not uncomfortable when a finger is used as the testing surface (Fig 4). T h e initial deposition of injected gutta-percha is illustrated in Figure 5. The needle is displaced coronally when apical deposition of gutta-percha is completed. Injection is continued as the needle is incre278
Fig l Delivery system for injection-molded thermoplasticized gutta-percha recently developed.'~ Control box regulates heat developed m syringe and adjusted according to needle gauge to standardize consistency of extruding guttapercha. Black sleeve of syringe is insulation.
Fig 2-Needles available in no. 18, 20, and 25 gauges.
Fig 3-Radiograph of mandibular molar shows 25 gauge needles in distal canal and one of mesial canals. Needles extend into apical portion of canals.
Fzg 4--Photograph shows extruded gutta-percha adhering to finger. At sufficient temperature, it flows freely jqom needle, is sticky, and can be drawn out to veryfine strand. At this temperature and consistency, gutta-percha is not uncomfortable to touch.
mentally withdrawn, filling the remaining part of the canal. A h a n d or finger plugger, dipped in alcohol to prevent adhesion of the gutta-percha to the instrument, is used to condense the filling material to the apex. Additional gutta-percha is injected
to fill the b o d y of the canal. The completed case is illustrated in Figure 6. Figures 7 to 10 demonstrate that the technique can be used throughout the mouth. Patients were recalled six to 12 months postoperatively.
Fig 5-Radiograph of same mandibular molar shown in Fzgure 3 taken immediately after injection of thermoplasticized gutta-percha shows canals almost completely filled.
Fig 6-Top, radiograph of same case after gentle manual condensation of the thermoplasticlzed gutta-percha. Bottom, six-month recall radiograph showing decrease in szze of periapical radiolucent area.
Rig 7--Mandibular canine. Left, preoperative radiograph shows referred case previously treated unsuccessfully. Middle, immediate postoperative radiograph shows obturation of two existing root canals and lateral canal associated with perilateral radiolucent area on mesial aspect of root. Right, six-month postoperative radiograph. 279
Fig 8--Maxillary premolar. Top, preoperative radiograph of @rred case. Bottom, left, immediate postoperative radiograph shows obturation of two canals. Bottom, right, 12-month recall radiograph shows complete healing.
Fig 9--Mandibular molar and adjacent premolar. Left, preoperative radiograph shows periapical radiolucent area related to molar. Right, 12month recall radiograph shows healing. Lateral canal in premolar was filled.
RESULTS Six- and 12-month postoperative radiographs available in 125 cases showed 54 of 56 cases with preoperative periapical radiolucent areas to have partial or complete resolution; 67 of 69 cases without any original periapical radiolucent areas showed no radiographic changes. All 280
patients were reported comfortable clinically.
DISCUSSION A new method of obturating the root canal system using injectionmolded thermoplasticized gutta-percha is currently being tested clinically. Preliminary findings in 125 cases
indicate that the method shows promise because the success rate seems comparable to the rate achieved with conventional guttapercha obturation procedures. Furthermore, the usual length of time required to introduce the gutta-pe r~ cha into a prepared root canal with the thermoplastic injection method was less than 20 seconds. On comple"
JOURNAL OF E N D O D O N T I C S ! VOL 7, N O 6, JUNE 1981
Fig lO-Maxillary molar. Preoperative radiograph shows severely alllacerated roots and infrabony pocket in tooth of recently referred patient with severe periodontal and endodontic involvement. B, immediate postoperative radiograph shows obturation and inserted posts in extremely dilacerated roots. Treatment was rendered despite poor prognosis because of strategic value of retaining terminal abutment.
tion of the injection process, the gutta-percha retained sufficient plasticity to allow manual condensation for up to two minutes. The obvious reduction of chair time offers the potential for a decrease in cost of endodontic treatment, which should make endodontic treatment available to a larger portion of the population. In the present evaluation, a new instrument is being used for plasticizing the gutta-percha. This instrument greatly facilitates the clinical adaptations of the technique of injection molding. However, the silver needles that were used are available in only three sizes, no. 18, 20, and 25 gauges; therefore, in m a n y instances the instrument cannot be introduced as far apically as might be desired. In the original in vitro approach, thinner needles were available, and they Were introduced to within 4 mm of
the apical terminus of the canal. Considerable effort has been made to develop needles that are fine enough to be introduced clinically into the apical portion of narrow canals. The critical factors are the thickness of the silver walls surrounding the lumen, which influences heat transmission, and the diameter of the lumen, which affects frictional resistance. These factors have opposite influences on the flow of guttapercha through a needle of given diameter. In some cases, control of the extension of the gutta-percha as it is condensed into the apical portion might prove to be a problem. However, the authors have found that overextension of gutta-percha is prevented by the constriction in the apical preparation of the canals, which is normally accomplished during the biomechanical preparation
sequence. Furthermore, they have found that the flow of gutta-percha stopped short of the apical terminus of the canal when the gutta-percha was not heated sufficiently or when the body of the canal was inadequately instrumented. In these instances, the gutta-percha can be easily removed while it is still soft, and the appropriate correction can be made. Thus far, only short-term observations are available regarding the clinical success of the injection-molding approach. Nevertheless, the results are most encouraging. Definitive conclusions, however, must await longer-term observations. Dr. Marlin is a lecturer on endodontics at the Harvard School of Dental Medicine, and associate clinical professor of endodontics at Forsyth Dental Center. Dr. Krakow is associate clinical professor of endodontics at Harvard School of Dental Medicine, staff associate at Forsyth Dental Center, and chairman of the department of endodontics at both institutions. Dr. Desilets is clinical instructor in endodontics at the Harvard School of Dental Medicine and staff associate at Forsyth Denter Center. Dr. Gr0n is senior staff m e m ber at Forsyth Dental Center. Requests for reprints should be directed to Dr. Krakow, Harvard School of Dental Medicine, Forsyth Dental Center, 140 The Fenway, Boston, 02115.
References I. Milas, V. B. Pathways of the pulp, ed 1. St. Louis, C. V. Mosby Co., 1976, p 629. 2. Yee, F.S., and others. Three-dimensional obturation of the root canal using injectionmolded, thermoplasticized dental gutta-percha. J Endod 3(5):168-174, 1977. 3. Luks, S. Gutta-percha versus silver points in the practice ofendodontics. NY Dent J 31:341-350, 1965. 4. Schilder, H. Filling root canals in three dimensions. Dent Clin North Am 723, 1967. 5. Torabinejad, M., and others. Scanning electron microscopic study of root canal obturation using thermoplasticized gutta-percha. J Endod 4(8):245-250, 1978. 6. Herschowitz, S. B.; Marlin, J.; and Stiglitz, M. R. US Patent no. 831714.