A simplified technique of orthograde MTA obturation on the elected canals of posterior teeth: Two case reports.

This article suggests a simplified technique of orthograde MTA obturation in less accessible canal(s) of posteriors teeth without using costly ultrasonics or specialised carrier. Essentially few finger pluggers, absorbent points and a simple canal projection method were used. The orifice(s) of the elected canal(s) to be obturated with MTA were projected onto the external occlusal surface for easy delivery and predictive instrumentation. The idea was based on 'easy access', 'working one canal with one mix at one time', 'thorough condensation' and 'removal of excess moisture'. In case I, palatal canal of tooth no. 2 with gross apical perforation and suspected VRF was obturated with MTA. And in Case II, tooth no. 19 presented with incomplete furcal fracture extending into the canal was obturated with MTA in all 3 canals unitarily. Dense homogenous MTA obturation was achieved and both cases healed uneventfully.

INTRODUCTION

The literature is replete with data on mineral trioxide aggregate (MTA) for the management of various endodontic conditions like root end filling,[1] repair of root perforations[2] and resorptions,[3] vital pulp therapy,[45] closure of open immature apex by apical plug[6] and other root-end inductive procedures.[7] This could be attributed to its endodontically favorable physicochemical and biological properties like superior sealing, good marginal adaptation, minimal microleakage, high biocompatibility and bioinductive and antimicrobial properties, etc., These favorable properties could be due to the slow leaching of calcium hydroxide and calcium ion from the set MTA. Tricalcium and dicalcium silicate react with water to produce calcium silicate hydrate and calcium hydroxide, which is leached out of the cement with time. Calcium ions in contact with tissue fluid react to form amorphous calcium phosphate, which is later transformed to carbonated apatite crystallites in the interface.[8]

Consequently, MTA has been suggested and successfully used by eminent clinicians and researchers to obturate the entire canal.[91011] The Lawaty technique and the MTA obturation technique by Bogen and Kutler can also be exemplified.[12] But, orthograde MTA compaction still remains challenging and technique-sensitive. Porosities and inadequacies are commonly seen.

Our simplified technique of orthograde MTA obturation presented in the cases below will help even the beginners to achieve homogenous and dense MTA compaction even in the less-accessible posterior canals or in the badly mutilated teeth without the requirement of costly armamentarium.

CASE REPORTS

Case 1

A 31-year-old male patient visited my office for a persistent symptom associated with tooth no. 2. The medical history was noncontributory but he had a present history of unsatisfied endodontic treatment from his previous dentist with respect to this tooth. No written or radiographic records were available with him. His mouth opening was less than normal. On exploration, the mesiobuccal (MB) and distobuccal (DB) canals were found to be filled and were satisfactory. The unfilled palatal (PC) was well enlarged and prepared, but its apical constriction was grossly violated to such an extent that a 55 no. H file went through it easily [Figure 1a]. Apart from apical transportation and zipping, apical vertical root fracture (VRF) was also suspected. Therefore, of the many treatment options proposed, orthograde MTA obturation of the entire PC was elected and informed consent was granted.

Figure 1

Case I (a-d), Case II (e-h) and evaluation on extracted teeth (i-l). (a) Grossly violated unfilled palatal foramen of tooth #2. (b) PC projected externally. (c) PC obturated with mineral trioxide aggregate (MTA). (d) 3 months postoperative. (e) Incomplete fracture extending from the mesiolingual canal to the distal canal of tooth #19. (f) All three canals projected externally. (g) MTA obturated in all canals. (h) One-year follow-up indicates healing. (i) Voids frequently noted when all canals are packed at one time. (j) Longitudinal section to compare the ortho and retro fills. (k) LS to show the extent of coronal and apical dye leakage. (l) Homogeneity of the interface as observed after demineralization

The working length was determined electronically (Raypex 5, VDW GmbH, Munchen) and the canal was circumferentially filed upward using the H file no. 20 through 40. Further shaping was avoided as it was already shaped. Copious irrigation with 1.5% NaOCL and 15% EDTA was performed using a side-vented 27-gauge irrigation syringe. Then, white ProRoot MTA (Dentsply, Tulsa Dental Specialties, Tulsa, TN, USA) was packed in the PC [Figure 1c] as per the general technique described below [Figure 2]. The postoperative period was uneventful and tenderness to percussion resolved in 2 weeks’ time.

Figure 2

Schematic illustration of the canal projection method and orthograde mineral trioxide aggregate compaction technique. Note: The elected canal is depicted as transported, apically perforated and gouged near the orifice. See text for description of the technique

Technique

Obturate all normal canal(s) with gutta percha (GP) and leave the ones elected for MTA packing. Debride the chamber free of any sealer or GP remnants. Cut a 6% taper GP stump and plug the orifice and the coronal third of the elected canal snugly (alternately, any large metal plugger may also be used). Around 10 mm of the GP stump should be extruding out of the cavity to assist its removal later [Figure 2a]. Fill the entire cavity around the GP stump with a dual cure syringeable core composite material, e.g., Paracore (Coltene Whaledent, Switzerland) following the manufacturer's instructions [Figure 1b and f]. Slowly rotate and pull out the GP stump to establish a unit canal with its orifice projected to the external surface occlusally [Figure 2b]. Enlarge the transported orifice using safe end burs or GG drill to enhance the funnel size and to gain straighter access [Figure 2c].

Select a set of three finger/handle pluggers (P1, P2 and P3). P1 is the largest plugger that goes till the working length without binding. It usually corresponds to the Master apical file (MAF) size or to one or two sizes lesser, depending on the canal curvature and the size of the preparation. P2 goes till the region of the junction of the apical and middle thirds or slightly beyond, but around 2-3 mm short of WL and P3 till the mid half. Also, select the largest lentulo spiral (LS) that goes to the junction of the apical and middle third without binding.

Now, irrigate the canal thoroughly and dry it using microsuction aspirators. Mix MTA with sterile water or proprietary liquid to a moderately viscous creamy consistency. Place the mix to the funnelled orifice using a fine cement carrier and tease it down briefly. Now, use LS at 1000 rpm in a slow pumping motion to carry it down to the middle third [Figure 2d]. LS may be introduced till the apical third if the apex is closed. If open, it can be completely avoided and, instead, P3 and P2 may be used sequentially. Now, insert P1 till the WL and give five to ten quick up and down strokes of 3-5 mm amplitude circumferentially [Figure 2e]. But, if the apical constriction is grossly violated, one or two slow light pushes 0.5 mm short of the WL with a thicker mix are preferable. Soak out the excess moisture from the canal using an absorbent point corresponding to the MAF size [Figure 2f] and work the P1 in a similar manner again. By this time, a hard apical base is felt and the WL will be shortened by around 0.5 mm. If this is not seen, then repeat the above step. As a greater length of MTA is condensed and the WL shortens by 3 mm or more, a radiographic confirmation is advised. Then, P2 takes the charge and a similar procedure is followed [Figure 2g]. The rest of the larger part of the canal is completed using P3 [Figure 2h] and the butt end of the larger paper points. After radiographically confirming the pack, a moist cotton is sandwiched and closed with temporary stoppings.

Note: Our technique did not require a messing gun, specialized carrier or ultrasonic vibration, but it is very important that the shortening of the WL while packing is gradual and in small thicknesses. The abrupt shortening by large thicknesses usually heralds inadequacies and porosities. This often happens due to introduction of large size pluggers or absorbent points out of the sequence in haste, particularly when the mix is crumbly or thick. Whenever it happens, P1 should be tried with little greater pressure to push it down, but it should be immediately confirmed radiographically. If porosities are evident, then try flushing with water or else peck it out with ultrasonic files.

Case 2

A 40-year-old asthmatic and phobic male was referred from a local clinic to manage the incomplete fracture of tooth no. 19 that runs from the mesiolingual canal (MLC) to the distal canal (DC) in the furcal region [Figure 1e]. There was persistent dull pain on biting that reportedly developed after the shaping session and after all the presenting symptoms of acute apical abscess were controlled. As per the previous records, the mesial and distal canals were prepared by protaper files (Dentsply Maillefer) up to F3 and F5, respectively. There was periapical radiolucency in the mesial root and minimally in the furcal region too.

With due informed consent, Interlig fiber (Angelus, Brazil) was bonded across the fracture and the rest of the core was built using a para core after blocking all three canal orifices with GP stumps [Figure 1f]. This partial core served as an intracoronal splint and bypassed the need of extracoronal splinting during treatment. It also helped in sealing the fracture in its earliest stage, restricting further ingress of microbes. After verifying the WL electronically, the canals were irrigated copiously with 1.5% NaOCL, 15% EDTA and 2% chlorhexidine solution, respectively. Then, each canal was unitarily obturated with pro root MTA as described in the technique above [Figure 1g].

The recall visit at 1 year revealed radiographic evidence of osseous healing in relation to the mesial root apex, and there was no evidence of further furcal breakdown [Figure 1h].

DISCUSSION

The canal projection method used in our technique could be a cheaper and easy alternative to projector endodontic instrument guidance systems (PEIGS, CJM Engineering, CA, USA) used for restoring badly broken down teeth prior to endodontic treatment.[13] The only modification needed is to shape the coronal third of the canal first. Apart from this, the other advantages of the unitary approach and our method of packing are: (1) Simplifies access to the less-accessible canals and there is no need of tedious orientation even if the internal anatomy of the pulp chamber is grossly violated and such are not uncommon in retreatment cases. It gives a feel like working on anterior teeth with a single canal. (2) Only the culprit canal(s) that require MTA is(are) selectively worked, (3) early strengthening and sealing of fracture is possible, (4) addition of water is not frequent; rather, one small fresh mix for one canal is our principal, (5) no specialized carrier or ultrasonic vibration is required. Hand condensation has also been reported to be the preferred method of orthograde placement.[14] We also prefer to avoid K files, except in extreme curvatures, as it tends to file up MTA particularly in the initial stage of packing, which is the most technique-sensitive stage too. (6) A lesser amount of MTA is needed and (7) there is no risk of blocking the other canals while working in one canal.

We have consistently observed that if the access cavity is flooded with MTA over all the prepared canals to be packed as suggested in other popular techniques, one has to go either very quickly in all canals to avoid blocking or one has to keep adding a considerable amount of water beyond the recommended ratio of 3:1 to maintain workability, relying more on flow. Abrupt shortening and porosities may be prone in both ways [Figure 1i]. In our case, one canal is packed at one time and is relied on thorough condensation and removal of excess moisture but less on flow. Our preliminary examination reveals a dense homogenous pack with good marginal adaptation, minimal porosities and dye leakage [Figure 1j–l].

The disadvantage of this technique may be the need of restoring the core in two stages. In general, the disadvantages of MTA are: Retrieval difficulties (particularly in curved canals), technique sensitivity, discoloration (grey MTA), slow set, cost and larger canal preparation requirement. But, usually, for canal preparations up to an ISO 25 tip size, 6% taper is adequate for our technique. It may also be argued that “retrievability” and “hermetic seal” may often be mutually exclusive. The entire canal length sealed by MTA will minimize coronal microleakage as well, which otherwise is also a cause of failure in endodontic therapy.[15] Also, comparable healing rates were seen when retreatments with MTA obturation were compared with combined conventional retreatment and surgery.[16] In the event of surgical intervention, if required after orthograde MTA obturation, the case could be advantageously accomplished by plain resection of the root(s) without retrograde filling. Root resection of 3 mm at the 0° bevel angle removes the majority of anatomic entities and 93% of the lateral canals that are potential causes of failure.[17] Retro preparation, if needed particularly to treat isthmus,[18] can still be done through MTA. Also, from the animal studies, no significant difference in healing was observed when set MTA was compared with freshly mixed root end filling.[19]

Therefore, developing a reliable, porosity-free and easy method of orthograde MTA packing may prevent a number of needless endodontic surgeries or may help the surgical procedure to be minimally invasive. Further clinical trials and strong research evidences are still awaited.

CONCLUSION

Posterior MTA obturation can be simplified by this canal projection method and unitary approach of packing elected canal(s).