12.1 Introduction

The aim of 3D obturation is to create a compact, homogeneous, and three‐dimensional defense against the eventual invasion of microorganisms into a root canal system that has been properly shaped and cleaned [1]. Consequently, canal obturation is currently considered a crucial step to make a root canal treatment (RCT) successful in the long term. Several root canal obturation techniques based on gutta‐percha and sealers have been proposed over the years [2, 3]. These techniques can be divided in two categories: cold techniques and warm techniques. Cold techniques, such as the single cone technique and the lateral condensation, have shown poor sealing capacity in vitro, mainly because of the insufficient adaptation capacity of the cold gutta‐percha to the canal space [4]. Moreover, the voids created cannot be fully compensated by the big amount of sealer needed in these techniques compared to warm ones [5]. On the contrary, warm techniques, which exploit the thermal properties of the gutta‐percha, allow for a better adaptation to the root canal anatomy and thus ensure a stronger sealing ability [6, 7].

Thermoplasticized gutta‐percha has been found to be able to flow into irregular spaces, such as isthmuses and lateral canals and, consequently, is considered a more effective method to fill the root canal space [8].

The gutta‐percha can be brought into the root canal as a point that is subsequently heated by means of dedicated heat carriers, then the softened material is packed by means of pluggers. The remaining part of the root canal is then back filled with thermoplasticized gutta‐percha extruded by means of devices like Obtura III Max (Obtura Spartan, Algonquin, IL) or Fast Fill (Eighteeth, Changzhou City, China).

An alternative way to do a warm obturation is by extruding directly the thermoplasticized gutta‐percha into the root canal previously dressed with sealer. When the thermoplasticized gutta‐percha is extruded into a root canal dressed with a bioceramic sealer, it is called BioConeless.

Root canal obturation by injection of thermoplasticized gutta‐percha was first described by Yee et al. in 1977 [9]. This technique is based on a direct injection of thermoplasticized gutta‐percha inside the canal by means of a dedicated gutta‐percha injector to reach a complete endodontic space filling [9, 10]. Several studies have underlined the efficacy of this technique in filling the endodontic space [11, 12]. Encouraging results have emerged from in vitro studies investigating the efficacy of canal obturation by injection‐molded thermoplasticized gutta‐percha (ITG) [11–13]. On the other hand, to date, few clinical studies are available in literature on the outcomes of teeth filled with this technique; the existing papers reported complete healing rates ranging from 93.1% to 100% after observation periods ranging between six months and three years [10, 14, 15].

According to the literature, the injection of thermoplasticized gutta‐percha has several advantages if compared to the other warm techniques; in fact, the procedure is time‐saving, it allows obtaining a good filling of the root canal system, and it is also able to fill complex anatomies (Figure 12.1a–d). The reported disadvantages are the risk of incomplete filling or overfilling [10, 13–17].

The injection of thermoplasticized gutta‐percha has been associated to zinc oxide eugenol (ZOE) sealers for a long time (since ZOE sealers were broadly used for warm vertical compaction techniques due to their wide availability, low cost, and good chemical and physical properties), but it can be used also with resin‐based sealers [18, 19].

12.2 Why BioConeless?

The spread of calcium silicate–based sealers, whose biocompatibility and excellent properties were reported by several articles, are described by some authors as the future of root canal sealers, even if at the moment there is no evidence of their superiority in terms of success rate with respect to other sealers [20–23]. Calcium silicate–based sealers were first formulated in order to be used with cold techniques, the single cone technique in particular, or lateral compaction technique [24].

In root canals with constant taper and where the fitting of the gutta‐percha point is precise, the single cone technique with bioceramic sealer works very well, because the point acts as a piston that pushes the sealer laterally, with a declinate but efficient wedge effect [25–27]. Conversely, sometimes, root canals have an oval shape (i.e. the distal roots of lower molars in the presence of a root canal whose shape is like a double‐barreled shotgun) or we are not able to reach the apex due to the presence of iatrogenic blocks, apical deltas, broken instruments, or abrupt apical curvatures: in these cases, the hydraulic push generated by the gutta‐percha point on the sealer is not efficient and the root canal filling ends up being insufficient [28–31].

In the case shown in Figures 12.2–12.6, a single cone technique with calcium silicate–based sealer was used to seal the distal root of this lower molar. The clinician was not satisfied with the result obtained with the bioactive sealer because the anatomy of the root was not correctly filled. At this point, the vertical warm compaction of the gutta‐percha was necessary in order to achieve correct filling of the root canal system. This clinical case confirms that there is not a single technique that can be used successfully to fill the root canal system in every case, but that we need to know several techniques in order to manage correctly all the clinical scenarios that we face [32].

Not every bioactive sealer can be used with warm techniques: in fact, the presence of heat tends to limit the flow of the material and to increase the setting reaction due to the evaporation of water [16].

The increasing request for a material to be used with warm gutta‐percha compaction techniques led some manufacturers to modify the composition of their sealers, making them heat‐compatible; premixed sealers containing propylene glycol instead of water, characterized by a high flow ability, were developed for this aim.

If we used a water‐based calcium silicate–based sealer, the temperature of the tip of the back‐fill device (ranging between 60 and 80 °C, according to the brand of the device chosen) would crystallize the sealer in contact with the tip, causing a total or partial block of the extrusion of gutta‐percha [33]. On the other hand, when using propylene glycol calcium silicate–based sealers, the heat is not able to cause the immediate crystallization of the product, making it possible to use heat inside of the root canal.

According to Drukteinis and Camilleri, “the unique properties of the highly flowable and dimensionally stable hydraulic calcium silicate–based sealers, the down‐pack procedure became easier and should not be performed so precisely in comparison to cases when conventional sealers are used.” Since “the hydraulic calcium silicate–based sealers are dimensionally stable and flow into all root canal irregularities, isthmuses, and dentinal tubules, therefore, the thickness of the sealer layer is not important to ensure the high‐quality obturation, even if the minimal condensation to softened gutta‐percha is applied” [24]. In addition, a microleakage study by De Angelis et al. reported promising results of the warm continuous wave of condensation combined with a bioceramic sealer [13, 34].

Other ex vivo studies by Abdellatif et al. [16] and Pontoriero et al. [17] reported good performances of bioceramic sealers combined with warm techniques thanks to the capability of the sealer to fill lateral canals and to obtain good scores in microleakage studies.

12.2.1 BioConeless: Indications

There are few indications reported for using the BioConeless technique. It is not necessary to have a specific taper to fill the root canals with the BioConeless technique, since it can be done with every kind of preparation. However, the apical size that is considered as a cut‐off is 0.7 mm. In foramina larger than that, it is not advised to use the BioConeless technique, because the risk of extrusion of gutta‐percha and sealer into the periodontium would be extremely high [35].

In the initial treatments, the BioConeless technique is particularly indicated when it is not possible to find a gutta‐percha point that is adequately fitting into the root canal, or the gutta percha point has not a good tug back or remains excessively short to the working length.

Some typical situation in which the BioConeless technique is extremely useful is that of apical deltas or abrupt apical curvatures [18, 34]: when this happens, a high pressure is required to push the gutta‐percha and sealers into the areas that have been cleaned by the irrigants, and the insertion of warm gutta‐percha into the root canals makes the filling phase easier and more predictable (Figure 12.7).

Another clinical situation in which the BioConeless technique is extremely effective and time saving is that of confluences: once the main root canal has been filled (with any technique), the secondary canal can be easily and quickly filled with bioceramic sealer and BioConeless technique [34]; in some of these cases, the pressure of the gutta‐percha on the confluent canal will further push the bioceramic sealer to the apical area filling even more the confluence (Figure 12.8).

In case of lower molars with double‐barreled shotgun‐shaped canals, the pressure applied by a single cone on the bioceramic sealer is insufficient to fill the entire anatomy; for this reason, the BioConeless technique can be used [34]. If one still wants to use the single cone technique, it is possible to use a single cone and then fill with the back‐fill device the space left between the master cone and the root canal walls, ensuring an adequate push to the bioceramic sealer to flow into the root canal system.

In retreatments, the BioConeless technique can help when we find a separated instrument that we cannot bypass or we bypassed with a lot of effort: even in this case, the pressure applied on the sealer by the warm gutta‐percha will be greater than the one applied with a single cone (Figures 12.9–12.11).

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