Gutta Percha Obturation Techniques James Anthony
most common cause of endodontic failure has been
T ascribed to incomplete obturation. Filling a root canal is intended to prevent microorganisms and toxins in the canal, as well as those present in the oral cavity, from passing along the root canal and moving out into the periradicular tissues. Matsumiya and Kitamura both demonstrated that bacteria remain in the deep portions of the endodontic system, even after chemical disinfectants. Healing of the periapical tissues occurs when the nutritional supply to the bacteria is stopped by the sealing properties of obturation. Unfortunately, the endodontic system is complex, including the accessory canals, anastamoses, and apical deltas. The inability to completely obliterate the irregularities of the endodontic system with a filling material and seal the apical delta foramen has been reported to account for nearly 60% of root-canal failures. Fluid percolation into the canal arises indirectly from the blood serum, water-soluble proteins, enzymes, and salts from both the apex and oral cavity. Once in the radicular space, those products undergo degradation and diffuse out to the periapical tissues and act as an irritant, which results in periapical inflammation. Bacteria will result in the producuon of toxic products in the root canal with periapical inflammation. In current endodontic treatment, it is said that "it is more important what comes out of the canal than what goes into it." So the emphasis seems to be placed more on cleaning and preparing the endodontic system than on filling it. This does not mean that obturation is less important; rather it means that endodontic success depends on meticulous root-canal preparation. For a complete three-dimensional fill, proper instrumentation of the root canal makes it a lot easier to facilitate. The objective of obturation of the radicular space is to fill the entire endodontic system and all of its complex anatomic pathways completely and densely with a nonirritating hermetic sealing agent(s), which results in a "fluid-tight seal," especially at the apex, but also coronally (to prevent infection from the oral cavity). Success is dependent on the thoroughness of endodontic cavity design, shaping, and cleaning. The thoroughness of debridement and patency of the root-canal system facilitates its successful sealing in the three-dimensional phase. A three-dimensional fill is desired because it: 1) prevents percolation of the periapical exudate into the root-canal space (providing a culture medium for any residual bacteria); 2) prevents microorganisms from entering and reinfecting the root canal; and 3)
From Pacific Dental Service for Animals, Vancouver, British Columbia, Canada. Address reprint requests to James Anthony, Pacific Dental Service for Animals, 7555 Cambie St, Vancouver, British Columbia, Canada V6P 3H6. Copyright © 2001 by W.B. Saunders Company 1096-2867/01/1603-0005535.00/0 doi:10.1053/svms.2001.26461
creates a favorable biological environment for the process of tissue healing to take place. At present, current methods of obturation of the radicular space employ a semisolid or solid material cemented into the canal, with a root-canal sealer used to seal the interfaces between core materials, and also between core materials and the dentin walls. Countless methods have been developed to obturate the radicular space, ranging from feathers to gold. The ideal root-canal filling material would ideally have the following properties: • • • • • • • • • • •
be easily introduced; seal the canal laterally and apically; not shrink after insertion; be impervtous to moisture; be bacteriostatic, if not bacteriocidal; be radiopaque; not discolor the tooth surface; not irritate the periapical tissues; be sterile; be easily removed from the canal, if necessary; be preferably semisolid on insertion and become solid.
No product presently exists to satisfy all these criteria. However, gutta percha fulfills most of the criteria. Gutta percha products vary slightly with each manufacturer, but are generally composed of about 20% gutta percha matrix, 66% zinc oxide (filler), 11% heavy-metal sulfates (radiopacifier), and 3% waxes or resins (plasticizer). Gutta percha is a polymer of isoprene called trans-polyisoprene. Trans-polyisoprene has two phases: an alpha (more linear molecular structure) phase, and a beta phase. Most gutta percha on the market today is of the beta phase; some of the thermoplastizing units using the alpha phase say that it has more of a tacky nature and better flow characteristics. The author has noted no difference in the clinical aspects of either alpha- or beta-phase gutta percha when m use. Gutta percha does have a few disadvantages, such as its lack of rigidity and adhesiveness. These disadvantages make the product harder to manipulate, condense, and adapt to the intricacies of the endodontic system. They can be overcome by the use of sealer cement to aid adhesion and the addition of heat to soften the material, allowing for better adaptation. Gutta percha also has a limited shelf life. It becomes brittle with age, which is hastened with heat and delayed with refrigeration. The author has found that one can rejuvenate the older gutta percha by momentary immersion of the cones m hot tap water (55°C), followed by instant cooling in cold tap water. Before obturation, the canals must be properly instrumented, and it is essential that they be dry. Root-canal sealer cements are used with gutta percha techniques of obturation because of the reasons mentioned in the previous paragraph. The sealer cements act as a caulking media to fill discrepancies between the gutta percha and the dentinal walls. The sealer cements also act as a lubricant to allow for easy placement of the gutta percha.
Clinical Techniques in Small Animal Practice, Vol 16, No 3 (August), 2001: pp 155-158
Most sealer cements are based on zinc oxide and eugenol combined with other additives. The combination of zinc oxide and eugenol forms zinc eugenate, which is a prostaglandin inhibitor, offering some anti-inflammatory effect. All sealer cements cause some periapical inflammation, which subsides with time. The ideal sealer cement would have the following properties: • be tacky when mixed and adhere to the canal wall; • set slowly; • have fine powder particles that will mix easily with the liquid cement; • be radiopaque; • expand while setting; • be bacteriostatic; • be nonirritating to the periapical tissues; • be insoluble in tissue fluid; • not stare the tooth structure; • be soluble in common solvents if the need for removal arises; • not provoke an immune response in the periapical tissues; • not be mutagenic nor carcinogenic. There are many types of sealer cements; none fulfill all of the above properties. The ones most commonly used are zinc oxide eugenol, calcium hydroxide cement, praformaldehyde cement (in some countries, this product is considered unwise to use because of its tissue destructiveness and potential for carcinogenic effects), AH26, Diaket, and other pastes. To ensure a thorough coating of cement, which is absolutely necessary, special files have been developed (EZ-Fill bidirectional spiral files) that are similar to lentulo files. Ideally, one wants only a minimal amount of sealer cement driven apically, laterally, and coronally. Many methods of obturating the radicular space with gutta percha have been developed. Some are tried and tested; others are new, innovative, and awaiting final judgment. All methods use the physical characteristic of gutta percha having plasticity or flow. Each technique is designed to force the gutta percha to flow into the radicular canal, filling the fine details of the endodontic system, especially the delta foramina, and finally condensing into a solid core. None of the obturation techniques will be effective without proper debridements and instrumentation. It is important to remember that all obturation methods presently do not completely seal; they all leak to some degree. The conscientious operator will try to master all techniques, because knowing only one technique limits the cases one can treat. The methods of obturation that are addressed in this article are as follows: • • • • • • • • •
master cone condensation; lateral condensation; heated lateral condensation; vertical condensation; eucapercha or chloropercha condensation; thermomachanical condensation; injectable thermoplasticized; Thermafil; Successfil and Simplifill.
The master-cone or single-cone technique involves the selection on one gutta percha (all cones are sized to ISO standards or can be converted to ISO standards) cone that is one size larger than the last file used in the standardized instrumentation technique. The cone is placed into the dry canal, and a "tug back '~ 156
(a slight tug is needed to withdraw the cone) should be felt. One can measure the length of the cone in the canal upon withdrawal to see if it is seated to the apex; however, a radiograph should be taken to confirm placement. The master cone is then coated with sealer cement (lentulo files can be used or instrumentation files in reverse twists are used to place sealer cement into the radicular space), placed into the canal, and condensed with pluggers or spreaders. This is a very simple technique, but it is unlikely to provide an effective seal and eventual failure can result. The objective of lateral condensation is to fill the canal with gutta percha points, condensing them laterally against the sides of the canal walls via the use of spreaders. A master cone is adequately fitted. The cone is withdrawn, coated with sealer cement, and seated into place (Fig 1). A root-canal spreader is placed beside the master cone and condensed in a lateral fashion. A smaller accessory cone whose tip is coated with sealer is placed in the space created by the lateral condensation of the spreader. This process is repeated until the canal is completely obturated. The excess gutta percha is removed with a heated instrument, and the restoration can then commence. The key instrument to lateral condensation is the finger plugger. This instrument should be prefitted into the canal space to within 1 mm of the apical working length. Remember that lateral condensation is not gutta perch cones in a sea of sealer cement. Warm lateral condensation uses a heated instrument such as a spreader before insertion into the canal (Fig 2). The softened gutta percha is easier to condense and will result in a denser root filling. Electric heated units such as the Endo Tec, Touch and Heat (Fig 3), and System B are available, but simply heating a spreader in a flame is effective. Various modifications to this simple technique have been recommended, such as the "continuous wave condensation" described by Buchanan. Heated lateral condensation methods combine the apical control of cold lateral condensation and the greater homogeneity of warm lateral condensation. The vertical condensation technique involves the use of a master cone with sealer cement that is placed into the canal. The master cone is condensed using root-canal pluggers to force the material apically. Subsequent segmented gutta percha is placed in the canal and condensed apically, and is repeated until the entire canal is obturated. One can modify this method using a warm gutta percha technique, which aids in the filling of lateral canals. This is performed by incorporating several waves of vertical compaction of warmed gutta percha. A heated carrier such as a root-canal plugger is heated to redness and is immediately forced into the coronal portion of gutta percha. A cold plugger is inserted and vertical pressure is applied to the heated gutta percha, forcing the material apically. This allows for intimate adaptation to the canal walls and delta foramina, but it is difficult and time consuming. The chloropercha technique uses chloroform that is considered carcinogenic in human dentistry and is not advised for use. The euchapercha technique consists of flooding the prepared canal with eucalyptus oil resin, and then seating a previously fitted master cone to the desired apical portion or dipping the preformed master cone in eucalyptus oil resin and then fitting the cone in the canal. The cone is then withdrawn a few seconds later and placed in alcohol to harden the formed cone. Sealer cement is coated on the apex and the cone is fitted into the canal. Lateral or vertical condensation may follow. This procedure has the disadvantage in that the eucalyptus oil resin will JAMES ANTHONY
Fig 3. The Touch and Heat allows for a very rapid heat build up on the probe. The probe tips can be straightened or can be ordered, which allows for the tip to reach the apex of the canine teeth.
1. A completely obturated canal using lateral condensaFig tion.
slowly leach out, resulting in cone shrinking and causing a void in the apex and possible failure. The thermomechanical method (TLC [Fig 4], McSpadden Spatulator, or the MicroSeal) of condensation uses specially constructed files fitted on a slow hand piece• The frictional heat from the compactor plasticlzes the gutta percha cones that are in the canal, and the flutes force the softened gutta percha apically. The gutta percha can easily be forced beyond the apex, and the files can break easily• There is a possibility of tissue damage (peridontium) due to the heat generated by the files• Void in the canal can also result from improper use. There are two mjectable gutta percha systems: one system uses a high-melting-point gutta percha (160°C: the Obtura); the other system uses a low-melting-point system (60°C: Successfil) (Fig 5). Both systems work extremely well when the
canals have been adequately prepared, cleaned, and dried. These systems work very well in cases with unusual internal anatomy. With these systems, the use of a sealer cement that does not set up too quickly in the presence of heat is advised. It is speculated that the removal of the smear layer from the canal walls will benefit allowing better penetration of the sealer cement and thermoplastized gutta percha into the dentinal tubules. Control of the flow of thermoplasticized gutta percha is a problem that can be avoided by using apical barriers. There has been no evidence of thermal damage to the periodontal ligaments with the use of these materials. But practice is needed to master these techniques. Having sufficient flaring at the coronal third, proper instrumentation, slow-setting sealer cements, good vertical condensation, cleanliness, and good organization are all required to ensure success. The core gutta percha carriers deliver the gutta percha in a thermoplasticized state, which allows excellent adaptation to the prepared canal. Control of the flow is still a problem, but can be overcome. Proper instrumentation, straight-line access to the apex, and a tapered, funneled coronal third preparation are absolutely essential for success. These core carriers are flexible and can go with the curves
Fig 2. A hand spreader with a solid metal "bulb" to allow for a longer, consistent heat transfer when using the heated gutta percha techniques. GU-I-IA PERCHA OBTURATION TECHNIQUES
Fig 4. The TLC (thermal lateral condensation) is a rotary file used on a slow hand piece that uses friction to "plasticize" the gutta percha, forcing the material apically.
of the canal. With proper placement of the carriers, the gutta percha on the carrier is not stripped off either the canal walls or the apex. Additional vertical condensation and axillary cones or thermoplasticized backfill maybe necessary. Once the core has been seated, it is important not to vibrate or move the core within the canal when removing the coronal component (the handle). Hybrid techniques have been developed to overcome difficulties that maybe be inherent in any one basic method. Thermafil, Successfil, and Alpha Seal are either metal or plastic cores (files) that are ISO-standardized and covered with alpha-phase gutta percha. These instruments use a specific heater that thermoplasticizes the gutta percha on the file. Once thermoplasticized, the properly sized file is inserted into the sealer cement-coated canal and seated (Fig 6). The shaft of the carrier is either severed off via a bur or heat (Thermafil and Alpha Seal), or the file is quickly twisted in reverse, leaving the gutta percha at the apex and removing the file from the canal. The canal, if not completely filled, can be backfilled with injectable thermoplasticized gutta percha. Proper instrumentation is
Fig 5. The Successfil heater with gun and canules. A new heater (which is very similar to this unit) has been developed by Coletene Wheldent, who has bought out the Successfil unit from Hygenic. The use of the new heater is the same as the Successfil unit.
Fig 6. A diagram of the Thermafil carrier seated in place showing the intended locations of the gutta percha and carrier.
paramount with these techniques. Insufficient heating of the material will result in the gutta percha being removed form the carrier on insertion. When insemng the heated carriers into the canal, it must be inserted to the working length with apical pressure, without rotation. Rotation of the carrier on insemon will result in stripping of the gutta percha from the carrier. These techniques are easy to do on well-prepared straight canals. Once variables exit in the canals such as curves or excessive lengths (as in the dog canine teeth) these procedures are very difficult to do. The ideal end result of endodontics is a lasting hermetic seal of the endodontic system. This would allow re-establishment of the periodontium. Over 90% of endodontic failures come from improper obturation (in the human feld, which is considered to be similar to veterinary dentistry)° but the reasons for these failures are usually related to improper canal preparation. Most instruments and techniques developed recently describe a system that is to be followed in its entirety, which discards other instruments that have proven useful in the past. Dedication to one system may make sense from a manufacturer's viewpoint. The use of traditional instruments and techniques in a new way with slight modifications and few new instruments is of benefit to the veterinary dentist. One can modify one's traditional techniques without incurring great expense and the need to master an entirely new technique. Learning by evolution as the need arises is more effective than learning by revolution.