Quality Resource Guide l A Guide to Contemporary Endodontic Technology 6th Edition 9 www.metdental.com Root Canal Filling There have been a growing number of technologies used in root canal filling in recent years. The newer technologies involve thermoplasticized gutta percha. In the following section a brief description of the available systems will be provided. Traditionally, lateral condensation of gutta percha has been the technique taught in most dental schools. However, filling of root canals with vertical compaction of heat plasticized gutta percha has also been popular, in a few dental schools, but required a more extensive instrumentation of root canals to ensure a highly tapered preparation. With the advent of rotary instrumentation and the use of instruments with high taper in a crown-down manner, the difficulties of preparing a highly tapered canal while maintaining the original canal shape were reduced. Thus, the vertical compaction method became more popular, because it assured good seal when tested in microleakage studies. The use of the System B (Kerr Endodontics), which allows an endodontic plugger to be electrically heated to preset values (usually 200 degrees C), further popularized this technique particularly among endodontists. System B provides a more controlled heat source that can easily be used to both plasticize the gutta percha when warm, and compact the gutta percha mass when cold. The method involves selecting a plugger that fits within 4-5 mm of the empty canal, then placing a master cone point to the working length. The System B plugger is driven through the cone to reach its pre- determined position, then maintained cold under pressure to condense the gutta percha in the apical third of the canal. The plugger is then heated again briefly to disengage it from the mass and withdrawn promptly. Another heat source device that could provide the same functionality is the Touch ‘n Heat (Kerr Endodontics). This device comes with pluggers, as well as spreaders that can be used for warm lateral condensation. When using System B or Touch ‘n Heat, the dentist can continue to back fill the canal with a device that injects plasticized gutta percha such as the Elements or Obtura III systems (Kerr- Endodontics) or the Calamus unit (Dentsply-Sirona). The Obtura System involves a high temperature (again about 200 degree C) thermoplasticized gutta percha (GP) that is injected from a gun into the root canal. All systems require sealer to be used, even the thermoplasticized gutta percha. However, thermoplasticized GP may fit better into the canals space irregularities. Other systems are available in which there is a core material with coating of gutta percha. An example of this is GuttaCore (Dentsply-Sirona). This system consists of GP on a harder core of cross-linked gutta percha, which is fabricated in different sizes. The instrumented canal is first measured using a metal sizing instruments to assess the size of the carrier to use. Next, the suitable carrier is placed in a small oven that is provided with the system, which warms the outer GP to a temperature that can be molded into the canal space. While these systems offer efficiency and ease of use, they do not provide adequate length control. Furthermore, retreatment of cases with the older plastic or metallic carriers has been particularly challenging, as the core material is frequently difficult to remove. GuttaCore was introduced to facilitate the retreatment process. It is important to emphasize that the seal in any gutta percha filling is dependent on the adequate application of sealer. Many different types of sealers are available. They vary according to the material and the setting time. While the seal of most available sealers is comparable, it is recommended that the dentist not use sealers that contain paraformaldehyde as they have been shown to be quite irritating to periapical tissues. Eugenol-based materials also produce some inflammation on the cellular level; however, they are used by many dentists, as it is believed that without microbial irritants, the inflammation is subclinical in its magnitude. Calcium hydroxide- based sealers are well tolerated. However, there is no value for calcium hydroxide within a sealer, since after setting the material cannot ionize and raise the pH, which is how calcium hydroxide is effective against microbial irritants. Resin sealers such as AH-Plus remain the most popular root canal sealer currently, and the one to which newer sealers is frequently compared in studies. More recently, several tricalcium silicate-based sealers have been introduced. These sealers, like MTA, are very biocompatible, and can be used in a single cone technique with gutta percha. In addition, they expand slightly upon setting, presumably enhancing the seal. One clinical observational outcome study showed reasonable success in cases that had minimal canal preparation and were obturated with a single cone and Bioceramic (BC) Sealer (Brasseler). 69 Regenerative Endodontic Therapy There has also been a growing interest in the regeneration of pulp following necrosis in teeth with immature apex. The reason for this interest is a combined interest in promoting the continued development of the root in immature teeth, as well as the surge of information on stem cell research that offers the possibility of regeneration of the pulp dentin complex. Immature teeth with pulp necrosis and apical lesions present a special problem because of the inability to perform traditional endodontic treatment, the weak structure of the tooth and the lack of alternative treatments for the young child. Seminal case reports have introduced the technique of pulp revascularization, following disinfection with antibiotic mixtures and induction of a blood clot that is covered with MTA. 73, 74 Numerous case reports, case series, cohort studies, randomized trials and systematic reviews have shown that in these cases control of infection and increase in root length and dentin thickness are possible. Animal studies have revealed that most of the mineralized tissue following revascularization is cementum or bone, and that the single most important factor in revitalization is bacterial control. 75 As noted, MTA placed in the chamber and some antibiotics, such as minocycline, can cause significant discoloration. Therefore, newer tricalcium silicates, non- minocycline antibiotics (such as metronidazole and ciprofloxacin together with clindamycin, doxycycline or a cephalosporin) or regular calcium hydroxide medicament can be used to control the infection. Observational studies have shown that antibiotic formulations are better than calcium hydroxide. 76,77l