Obturation

Root canal obturation is an essential part of endodontic treatment. Traditional rotary instrument preparations create large and generally round canal cross-sections, which are imposed by the shape of the instruments rather than by the natural anatomy of the canals. Such round preparations can often leave behind debris, which was actively packed by the instruments into untreated "fins" and natural ramifications. Consequently, such recesses cannot be adequately obturated.

The SAF System generates a more natural and complete three-dimensional cleaning and shaping of the canal systems. When prepared with the SAF, the final canal shapes remain consistent with the original canal shapes and cross-sections. Typically, final apical canal dimensions will be 2-3 ISO sizes larger than the initial apical size and maintain the canal's natural taper .

For example, if the initial apical size was #20, the final apical size is likely to be #30-#35. The canals will be thoroughly cleaned, shaped and disinfected, while preserving their natural (round, oval, teardrop, or other) cross-sectional shapes, consistent with their natural morphologies.

Just as round tapered files cannot follow the natural canal anatomy, industrial pre-shaped cone obturation materials cannot match all of the natural and conservatively prepared final canal configurations. Therefore, to generate maximum benefit from the three-dimensional cleaning and shaping offered by the SAF System, it is important to keep in mind the need to create a more thorough three-dimensional sealing of the root canal systems by using one of the conventional canal obturation techniques .

To determine accurate final dimensions, it is recommended to gauge the prepared canal using a gutta-percha master cone or a NiTi hand-file prior to obturation.

Note that after SAF preparation, the apical portion of the canal will typically be 2-3 ISO sizes wider than the original, but not necessarily round in cross-section. Therefore, there is no need for additional apical enlargement. If additional apical enlargement is still desired, further enlargement can be achieved by using the same or larger SAF (2.0 mm if size #35 was reached). Some dentists who prefer a round apical preparation use a final touch with a hand or rotary file for that purpose . Such use should be done with care, to avoid the possible negative consequences, such as packing of debris or creation of dentinal micro-cracks.

The following methods are commonly used for the obturation of canals shaped with the SAF System, and should be applied in their conventional manner. These methods are described below in headlines as typically used and are not detailed, as users should already be acquainted with them:

A.  Lateral compaction:The conventional common method of fitting a master gutta-percha cone and adding accessory cones with obturation sealer, whilst using a spreader to laterally compact the cones and to create space for additional cones.

In oval canals, one should consider to use more than a single master cone (two, and sometimes even three) in the oval cross-section. Such an additional master cone would usually be smaller than the main master cone, and its placement can help reduce the chance for extrusion of the obturation material.

B.  Warm vertical compaction :A technique that can be excellent for the three-dimensional obturation of irregularly shaped canals created by the SAF system (versus the generally round shape and incompletely cleaned canals that are often created with conventional rotary/reciprocating instruments or hand files):

1. 1. Classic: Select a master gutta-percha cone to fit just short of working length, seating and searing it with a heated plugger to fill the apical region, and then adding small segments of gutta-percha to back-fill the coronal portion. Backfilling of the coronal portion can optionally be performed with an injectable warm/softened gutta-percha system.
   2. Continuous wave technique: Pre-fit the appropriate heat-carrier to the length and shape of the canal, insert gutta-percha with sealer to the apical region, apply a thermoplasticizing temperature (usually 200^oC) for 2-3 seconds, sustain apical pressure for 10 seconds, and use a separation burst (300^oC) for 1 second to remove the coronal segment. A cold hand-plugger is used to assure proper lodging of the apical mass and to assist in back-filling with increments of thermoplasticized gutta-percha.
   3. Combination technique - modification for long-oval canals: In oval canals, the combination of the lateral compaction and warm compaction techniques is advised in order to avoid excessive sealer/gutta-percha extrusion. Lateral cold compaction with a NiTi spreader is initially used in the apical area, followed by vertical compaction with a hot plugger, heated to 100^oC, followed by further compaction with a cold hand-plugger.

C. Carrier-based obturation : A central solid-core carrier system that provides a simple and consistent method for three-dimensional obturation following an SAF preparation. Application of sealer, pre-heating the obturator and its slow insertion into the canal will result in extremely tacky, adhesive alpha-phase gutta-percha with excellent flow characteristics, which will provide excellent adaptation to the canal walls due to the initial clean and smooth dentin surface of the SAF preparation.

D.  Chloroform-dipped customized master cone modification : When applied in oval or large canals (>#35), a chloroform-dipped customized master cone may be initially prepared and used, with either cold lateral compaction or warm vertical compaction. The customized master cone, which will have an imprint of the canal's apical portion on it, should be allowed to dry and re-harden before being used. Make sure that this method is acceptable in your country.

In this technique, it is possible to initially compress and flatten the master cone in order to give it an oval shape. The master cone to be used should reach 2-3 mm short of working length, and be held by lockable tweezers, in order to keep it at a set vertical insertion path. The apical end of the master cone is dipped in chloroform for 2 seconds, enough to soften the outer surface of the cone but leaving the core of the cone intact. It should then immediately be inserted into the root canal and pushed apically with pecking motions all the way to working length. Such pecking motions will also eliminate the interference of potential undercuts. The cone should be immediately removed from the canal and held with the locked tweezers out of the canal to allow it to dry. The chloroform will evaporate within 15 seconds, and the master cone will solidify while presenting the imprint of the apical area of the canal on its surface. The customized master cone should then be applied with some sealer into its seat, followed by either cold lateral compaction or warm vertical compaction.

E. BioCeramic sealer-based obturation : Techniques that are based on BioCeramic (BC) sealers or other similar products, combined with a single obturation cone (gutta percha, C-point, etc.), have become popular in recent years. Such obturation techniques became possible due to the introduction of new materials which are hydrophilic and have the ability to strongly adhere to dentin, while being highly biocompatible. These techniques take advantage of the sealers' flowability to fit effectively into the clean space created by the SAF instrumentation, following the natural canal morphology. Research has shown the high-level of micro push-out bond strength achieved by such obturation techniques following SAF instrumentation (Pawar et al. Int Endod J, 2015). These sealers may be used in various techniques, as advised by their manufacturers, combining the sealer, with designated cones, such as BC-covered gutta percha cones, C-points, etc.

F.  Any variation of the aforementioned obturation techniques or others may also be used.

It is important to note that other than the single-cone obturation technique, which is inadequate when addressing irregular canal morphologies, all obturation techniques enable proper sealing following SAF preparation, although some differences may be noticeable during the obturation procedure, including:

1. Less noticeable "tug-back" sensation, as such a sensation is more pronounced in round apical preparations, which will only exist after SAF preparation if the canal’s apical region was originally round in cross-section. The SAF preparation does not impose a round cross-section in the apical region and rather follows the natural anatomy of the canal.
2. Easier flow of any obturation sealer, as well as easier insertion of spreaders and accessory gutta-percha cones, due to the smoother and cleaner root canal surfaces achieved by the SAF preparation.
3. The need to use a variable amount of accessory cones, which could either be less accessory cones (with a customized master cone) or more cones (with lateral compaction) than usual. This is due to the thorough removal of debris from fins and recesses of flat-oval canals.

Note: The probability of causing micro-cracks in the radicular dentin during SAF instrumentation is much lower than when rotary/reciprocating instrumentation systems are used. This eventually implies a lower chance for obturation-related fractures in SAF-treated roots. Nevertheless, it is advised to avoid applying excessive force while obturating.