A technique for placement of apical MTA plugs using modified Thermafil carriers for the filling of canals with wide apices \\CASE REPORT

A technique for placement of apical MTA plugs using modified Thermafil carriers for the filling of canals with wide apices
M. Giovarruscio, U. Uccioli, A. Malentacca, G. Koller1, F. Foschi1,
& F. Mannocci1
Introduction
Mineral trioxide aggregate (MTA) was originally introduced as a novel root-end filling material (Torabinejad 1995) with a wider range of applicability suggested subsequently (Pitt Ford et al. 1996, Torabinejad & Chivian 1999). The traditional applications of MTA (e.g. perforation repair and root-end filling) were extended to pulp capping (Eidelman et al. 2001, Karabucak et al. 2005, Nair et al. 2008, Accorinte et al. 2009, Srinivasan et al. 2009, Subramaniam et al. 2009) and also to the orthograde filling of canals in teeth with immature apices (e.g. apexification) (Felippe et al. 2006, D’Arcangelo & D’Amario 2007, Simon et al. 2007, Nayar et al. 2009). Despite the introduction of several protocols to support the use of MTA as a material for canal filling (Giuliani et al. 2002, Hayashi et al. 2004, D’Arcangelo & D’Amario 2007, Pace et al. 2007), its rheological properties make it difficult to handle and have limited its widespread adoption (Gomes-Filho et al. 2009). Although the extrusion of MTA beyond the apex in the periapical tissue is relatively safe (Tahan et al. 2010) or even beneficial (Hashiguchi et al. 2011), control of the material is recommended (Felippe et al. 2006, Tahan et al. 2010). An improved MTA placement technique is described, in which de-sheathed Thermafil carriers (Dentsply Maillefer, Ballaigues, Switzerland) were used in a series of cases with precise positioning of the material in canals with wide apices.
Clinical technique
The following protocol was validated using extracted teeth in a laboratory setting. The outcome was observed after rendering the teeth transparent (Riitano et al. 1990) with the MTA plug being assessed with the aid of a surgical operating microscope (OPMI Pico; Carl Zeiss Meditech, Jena, Germany). Subsequently, the technique was applied in
a series of clinical cases.
Canal preparation
Traditional shaping techniques can be used with this novel canal filling protocol, providing that particular attention is paid to the gauging of the canal terminus. In the cases presented, after initial patency filing with appropriately sized K-files, the working length was established radiographically. Whenever possible, depending on the apical size, a confirmatory reading with an electronic apex locator was obtained. In the case of apices ranging between size 40 and 80, cleaning and shaping of the root canals were undertaken, following a sequence that included the use of a size 20, .04 taper Profile instrument (Dentsply Maillefer, Ballaigues, Switzerland); a size 25, .08 taper ProTaper (F2) (Dentsply Maillefer); a size 40, .06 taper ProTaper (F4) (Dentsply Maillefer) and manual apical gauging using size 40 and above NiTi K-files (Dentsply Maillefer) to the working length. In larger canals, that is, over 0.8 mm, root canal preparation was focused mostly on chemo-debridement and apical gauging rather than dentine removal. Irrigation was performed with at least 5 mL of 1% NaOCl solution and a final rinse with 1 mL of 17% EDTA solution.
Stage I: preparation and selection of Thermafil carriers
The technique was divided into three main operative stages (Fig. 1a–c). During the first stage (Fig. 1a), a series of Thermafil carriers (Dentsply Maillefer) with the Gutta-percha coating removed (Fig. 2) of decreasing size were tried into the canal. A de-sheathed Thermafil carrier that would bind 1 mm short of the working length was selected and, if deemed necessary to limit or prevent over-extrusion of the MTA, the positioning was verified with an intra-operative periapical radiograph, as the Thermafil carrier is radioopaque. Subsequently, two further carriers, fitted 2 and 3 mm short of the working length, were placed.
 
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Figure 1
Clinical steps of the filling technique. (a) Try-in of the de-sheathed Thermafil carrier fitted 1 mm short of the working length. (b) MTA pellet placement, an MTA plug is created with the MTA Pellet Block and positioned at the canal terminus with progressive gentle plugging with three de-sheathed Thermafil carriers (binding 1, 2 and 3 mm short of the apex).

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Figure 2 De-sheathed Thermafil carriers with sizes corresponding to the plastic core after removal of the Gutta-percha. The radiopacity of the carrier allows confirmation of its position radiographically. Furthermore, owing to the flexibility of the carrier it is possible to negotiate curved canals and bypass ledges or fractured instruments.

Stage II: preparation of the MTA plug
The MTA plug is formed during the second stage (Fig. 1b): MTA (Dentsply Maillefer) is
mixed as suggested by the manufacturer, and a MTA plug is formed by placing it in the pellet block (G. Hartzell & Son, Concord, CA, USA) (Lee 2000). The MTA Pellet Block allows the size of the plug to be selected according to the size of the canal terminus from stage I (Fig. 3a). Once mixed, the MTA is placed into the groove in the MTA Pellet Block corresponding to the apical diameter.
Stage III: placement of the MTA plug using de-sheathed Thermafil carriers
The MTA plug was placed at the end of the Thermafil carrier and then inserted into the root canal using the smallest de-sheathed Thermafil carrier determined in stage I

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Figure 3 (a) The MTA Pellet Block (G. Hartzell & Son, Concord, CA, USA) allows accurately sized MTA cement plugs to be formed using the corresponding notches on the sides of the block. (b) Once the MTA pellet has been formed, it can be inserted to the canal terminus with the aid of the preselected de-sheathed Thermafil carrier.

(Fig. 3b). Following the placement of the first apical plug, the other two carriers, reaching 2 and 3 mm short of the working length, respectively, were used to condense the material and to obtain a final apical plug of at least 3 mm length as demonstrated by diaphanisation (Fig. 4). A three mm plug is recommended to obtain the best possible seal using MTA (Al-Kahtani et al. 2005). Alternatively, longer MTA plugs (5 mm) can be prepared when apical surgery is planned following the completion of the orthograde filling or to negotiate apical curvature.
It was noted that, if MTA appeared over dried and therefore difficult to manipulate,  a droplet of water may be used to increase the flowability of the mixed MTA; on the other hand, if the material was found to be over-hydrated, a paper point may be used to re-establish the correct water to powder (w:p) ratio. When an apical stop is not present, such as in cases involving resorbed apices, an apical barrier technique using materials such as collagen matrices (Spongostan, Ethicon, Sommerville, NJ, USA) may be used (De-Deus & Coutinho-Filho 2007, Gharechahi & Ghoddusi 2012), prior to placing MTA with the technique described.
Case 1
In case 1 (Fig. 5a,b), a 32-year-old patient presented with an apical radiolucency located on tooth 27. An acute apical distal curvature was noted. Intraoperatively, an apical diameter greater than size 40, associated with a nontapered apical third, was noted. The filling technique was used to create an apical plug 6 mm long beyond the level of the curvature. The flexibility of the de-sheathed Thermafil carrier allowed the negotiation of the curvature for the adaptation of the MTA apical plug.
Case 2
In case 2 (Fig. 6a–d), a 23-year-old patient presented complaining of recurrent infections on tooth 46. Radiographic examination revealed the presence of a large periradicular radiolucency with furcation involvement. A fractured instrument was noted in the mesial root canal. After patency was gained and working length was determined for all five canals, apical gauging indicated the presence of wide apices in the mesiobuccal and middle mesial canals (>0.4 mm). The filling technique was used to adapt the MTA plugs. Radiographs taken at 6 months and 1 year confirmed a reduction of the radiolucency associated with the mesial root and furcal area.

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Figure 4 Visualization of the MTA apical plug using cleared teeth. The surgical optical microscope image shows the ingress of MTA in the apical delta; traditional Gutta-percha backfilling was successfully used.


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Figure 5 (a) Case 1. Preoperative periapical radiograph of tooth 27 affected by chronic apical periodontitis (b) Postoperative radiograph showing the extent of the MTA apical plug placed with the de-sheathed carriers through the curved apical third.

Case 3
In case 3 (Fig. 7a–c), a 22-year-old male patient presented with tooth 47 affected by post-treatment chronic apical periodontitis. Apical gauging revealed wide apical foramina (>0.4 mm). Apical plugs of 3 mm diameter were formed with the aid of the MTA Pellet Block and applied using the previously fitted de-sheathed Thermafil carriers. An eighteen-month recall revealed healing of the radiolucency.
Case 4 In case 4 (Fig. 8a–c), a 26-year-old female patient presented with a large periapical lesion associated with tooth 21. An apical plug was placed with a size 120 de-sheathed Thermafil carrier. A collagen sponge was preventively placed beyond the apex to create an apical barrier to prevent MTA extrusion. The MTA plug was carried in the canal with the de-sheathed Thermafil carrier. In this case, the straight canal did not represent difficulties in positioning the MTA plug, but the use of sizes 100, 120 and 140 de-sheathed Thermafil carriers allowed for precise gauging of the canal. A follow-up radiograph at 3 months showed initial signs of healing.

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Figure 6 (a) Case 2. Preoperative radiograph of tooth 46 affected by chronic apical periodontitis with a pre-existing root filling with a fractured instrument. (b) After patency was regained in all canals, apical gauging indicated wide foramina on the mesiobuccal and middle mesial canals. A working length radiograph was taken with de-sheathed Thermafil carriers in the three mesial canals and GP cone in the 2 distal canals. (c) The carrier plugging technique was used in the wide apices (>0.4 mm). Postoperative radiograph showing the mesiobuccal and middle mesial canals filled with pre-formed MTA plugs. The mesiolingual canal was filled with a mixed technique: GP in the 3 mm of apex and to pulpal floor with vertically compacted white MTA. Distal canals were filled with thermoplastic Gutta-percha. (d) One-year radiographic recall of tooth 46 following restoration by the referring dentist. The radiograph shows complete healing.

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Figure 7 (a) Case 3. Preoperative radiograph showing tooth 47 affected by chronic apical periodontitis in the presence of a failing root filling. (b) Intra-operative radiograph to confirm the successful formation of 3 mm MTA terminal plugs using sheathed Thermafil carriers. The apical gauge was determined to be larger than size 40. (c) Eighteen-month recall. Healing of the periapical lesion was observed. The filling coronal to the MTA pellet was carried out using thermoplasticized Gutta-percha.

Case 5
In case 5 (Fig. 9a–c), a 19-year-old female patient presented with failing root canal treatments on teeth 11 and 21, following dental trauma. Four millimetre apical plugs were positioned as described previously. With accurate gauging and positioning to the working length of the de-sheathed Thermafil carriers, it was possible to minimize extension of MTA. The fourteen-month recall showed signs of healing.
 
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Figure 8 (a) Case 4. Preoperative radiograph of tooth 21 with an open apex and a large periradicular lesion. (b) Postoperative radiograph showing the 3-mm MTA plug, 2-mm thermoplastic Gutta-percha backfilling and a fibre post with composite core restoration. (c) Three-month recall radiograph showing initial healing of the periapical radiolucency.
 
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Figure 9 (a) Case 5. Preoperative radiograph of teeth 11 and 21 showing poor root filling and posttreatment disease. (b) Postoperative radiograph showing the 4-mm MTA plugs, 2-mm thermoplastic Gutta-percha backfilling and a fibre post restoration with a composite core. (c) Fourteen-month radiographic recall showing initial signs of healing.
 
Discussion
This novel technique for the filling of root canals wider than 0.4 mm at the canal terminus was developed in extracted teeth, which were than cleared. The use of transparent teeth allowed direct visualization of the quality of the apical plugs in a nondestructive manner (Venturi et al. 2003). The use of Thermafil carriers as gauging instruments has been described in the past (Saunders et al. 1993). The plastic carrier of Thermafil has several advantages compared with its predecessor made of metal (Clark & ElDeeb 1993). The plastic Thermafil carriers, unlike conventional metal pluggers, are flexible and can be used to negotiate curved canals and may also be pre-curved to bypass ledges or fractured instruments. The laboratory tests with the support of a surgical microscope allowed for refinement of the technique prior to being applied clinically. The use of the de-sheathed Thermafil carriers allows the insertion of MTA plugs to the desired working length in a reproducible and predictable manner. Complete setting of MTA is expected to occur in most cases within 72 h even if the powder was not fully mixed with aqueous media (Budig & Eleazer 2008), owing to the uptake of liquid from the surrounding tissues. The de-sheathed Thermafil carriers might also be used to compact the material; however, excessive condensation will affect the final strength and hardness of the set MTA (Nekoofar et al. 2007). The improved sealing ability of MTA, used as orthograde plug in wider apices, has been demonstrated in previous studies (Orosco et al. 2010). The most frequent physiological shape of the apical foramen is round (52.9%) followed by an oval shape (25.2%) (Martos et al. 2010). However, chronic apical periodontitis may lead to altered anatomy, with periforaminal and foraminal resorptions being present, respectively, in over 80% of roots associated with periapical lesions (Vier & Figueiredo 2002). Iatrogenic errors such as stripping, over-instrumentation and apical transportation may also alter the physiological anatomy of the apical foramen (Moore et al. 2009, Gergi et al. 2010). In the presence of oval canals, it is also possible to provide a good adaptation of the MTA, which would be otherwise difficult to achieve with round section Gutta-percha points (Sahni et al. 2008).
Conclusion
The adoption of de-sheathed Thermafil carriers as flexible MTA pluggers provides improved control and consequently a reduced risk of MTA extrusion in cases of canals with wide apices.
Disclaimer
Whilst this article has been subjected to Editorial review, the opinions expressed, unless specifically indicated, are those of the author. The views expressed do not necessarily represent best practice, or the views of the IEJ Editorial Board, or of its affiliated Specialist Societies.

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