Mineral trioxide aggregate apical plug method for the treatment of nonvital immature permanent maxillary incisors: Three case reports.

Treatment of nonvital immature permanent teeth with calcium-hydroxide is associated with some difficulties such as weakened tooth fracture, root canal reinfection and long treatment time. Mineral trioxide aggregate (MTA) apical plug method is an alternative treatment option for open apices, and has gained popularity in the recent times. In this case report, we have attempted to present successful treatment of three maxillary incisors with open apices and periapical lesions with MTA. After preparing the access cavity, the working length was determined. The root canals were irrigated with 2.5% Sodium hypochlorite (NaOCl) and disinfected with calcium-hydroxide for two weeks. MTA was then placed in the apical 3 millimeters of the root canal. The remaining part of the root canal was filled with gutta-percha and the coronal restoration was finished with composite resin. After six months the radiographic examination showed a decrease of periapical lesions. At a 1-year and 18-months follow up, radiological and clinical successful healing of the incisor teeth was seen. MTA seems as an effective material for the apical plug method for the treatment of nonvital immature permanent teeth with open apices.

INTRODUCTION

Complete formation of the root and closure of the apical foramen continues for up to 3 years following eruption of the tooth.[1] If the pulp of young permanent teeth is damaged before the closure of the apical foramen, pulp necrosis may occur. In immature teeth, dentinal tubules are wide and allow the penetration of bacteria and their irritants. Hence, root resorption occurs instantly after trauma in these teeth. Root canal treatment should be done as soon as possible to inhibit the root resorption. The biggest problem in endodontic treatment of these teeth is obtaining an apical seal. The purpose of the apexification therapy used in nonvital immature teeth is to induce the formation of a hard tissue barrier at the root apex or the completion of apical development.[1] Calcium hydroxide is commonly used for this aim.

Recently, synthetic apical barriers with a variety of materials have been proposed as alternatives to the traditional apexification treatment method with calcium hydroxide.[2] Mineral trioxide aggregate (MTA) is the most popular material for this aim. MTA has been suggested to create an apical plug at the root-end and helps to prevent the extrusion of the filling materials.[3] The material consists of fine hydrophilic particles of tricalcium silicate, silicate oxide and tricalcium oxide.[4] When MTA is mixed with sterile water, it forms a colloidal gel, and its setting time is 3 - 4 hours in the presence of moisture.[5] The following three clinical cases describe the use of MTA as an apical plug. Root canal treatment and follow-ups of three nonvital immature permanent upper central incisors are presented. All the cases had signs of apical periodontitis and trauma history.

CASE REPORTS

Case 1

A 14-year-old boy with no general health problems was referred to the Faculty of Dentistry of Selcuk University on August 14, 2007. The patient and his mother reported that the permanent maxillary left incisor was traumatized 4 years ago when he fell down. The clinical examination revealed a labial sinus tract in the area of the upper left incisor which was accompanied by swelling. Periapical radiographic examination revealed an immature tooth with a wide open apex and a radiolucent area in the apical region of the maxillary left incisor [Figure 1a]. In the clinical tests, tooth was not tender to percussion and did not respond to the vitality tests. After the application of the rubber dam, an access cavity was prepared. Approximate working length was established with both radiographic method and the apex locator (Root ZX, J Morita MFQ Corp., Kyoto, Japan). The root canal was lightly mechanically cleaned using Hedstroem-files under irrigation with 2.5% sodium hypochlorite (NaOCl; Caglayan Kimya, Konya,Turkey). Then the root canal was dried with sterile paper points and a solid mix of calcium hydroxide (Sultan Healthcare Inc., USA) with distilled water was placed into the root canal. After placing a sterile cotton pellet, the access cavity was closed with a temporary filling material (Cavit, 3M Espe, Seefeld, Germany).

Figure 1

(a) A preoperative radiograph of maxillary left central incisor with an open apex in the first case of the case reports, (b) Radiographic evaluation of Mineral trioxide aggregate level in the first case of the case reports, (c) Follow-up after 6 months of the first case of the case reports, (d) Follow-up at 18 months of the first case of the case reports

After a 2-week interval the sinus tract disappeared and there were no other symptoms. The calcium hydroxide dressing was removed by instrumentation and irrigation with 2.5% NaOCl and 17% Ethylenediaminetetraacetic acid (EDTA; Wizard, Rehber Kimya San, Istanbul, Turkey). The root canal was dried with sterile paper points. MTA (Pro-Root MTA, Dentsply Maillefer, Ballaigues Switzerland) was mixed according to manufacturer's instructions and was placed with a small amalgam carrier to the canal orifice. The MTA mixture was then adapted to the canal walls using a thick gutta-percha cone which was tightened 3 millimeters shorter than the working length. The correct position of the MTA mixture was controlled with a periapical radiograph [Figure 1b]. A wet sterile paper point was then placed in the coronal part of the root canal and access cavity was closed with a temporary filling material for the setting of the MTA. The temporary filling material and paper point was removed after two days and the set of the MTA was gently tested. The rest of the canal was obturated with lateral condensation technique of the gutta-percha in association with a root canal sealer AH Plus (Dentsply, DeTrey, Konstanz, Germany). Coronal restoration was completed with a hybrid composite resin (Clearfil ST, Kuraray Medical Co., Japan).

The clinical follow-up at 6 months and 18 months exhibited an adequate clinical function, and absence of clinical symptoms and any sinus tract. The radiographic follow-up at six months revealed a decrease of the periapical lesion [Figure 1c], and at eighteen months showed a complete healing of the periapical radiolucency with regeneration of the periradicular tissue and new cement formation at end of the root [Figure 1d].

Case 2

A 15-year-old girl presented with a buccal sinus tract accompanied by swelling in the area of the maxillary left incisor. At 8 years of age, she suffered a trauma to this area. A crown fracture had occurred and it was restored with composite resin. The patient and her mother told that the tooth was extirpated 4 months ago. The patient did not experience any discomfort, except for an occasional bad taste in his mouth. The tooth was asymptomatic, and the clinical examination revealed physiological mobility and slight discoloration. Radiographic examination of tooth showed an immature tooth with a wide open apex and a radiolucent area at the end of the root-canal system [Figure 2a]. After removing the temporary filling material the working length was determined with the radiographic technique. Calcium hydroxide disinfection was applied to the root canal for a 2-week interval. The method for the creation of an apical plug with MTA mixture was applied as in Case 1 [Figure 2b]. The remaining part of the root canal was filled with warm vertical condensation technique of the gutta-percha and root canal sealer, and the crown was restored with a hybrid composite resin.

Figure 2

(a) A preoperative radiograph of maxillary left central incisor with an open apex in the second case of the case reports, (b) Radiographic evaluation of Mineral trioxide aggregate level in the second case of the case reports, (c) Follow-up after 6 months of the second case of the case reports, (d) Follow-up at 18 months of the second case of the case reports

The clinical examination after 6 and 18 months showed the absence of buccal sinus tract. The periapical radiograph at 6 months revealed the reduction of the radiolucent area at the apical region [Figure 2c] and after 18 months, radiographic examination showed a further reduction of the radiolucency [Figure 2d].

Case 3

A 12-year-old girl with no general health problems was referred to our clinic on March 14, 2008. The patient and her father reported that the permanent maxillary left incisor was traumatized 2 years ago when she fell down. There was a buccal sinus tract on the gingival region of the upper left incisor. The clinical examination revealed an enamel-dentin crown fracture and the pulp of the tooth was open. The mobility of the tooth was in normal limits. Radiographic examination of teeth revealed an immature permanent tooth with an open apex and radiolucent lesion at the periapical area [Figure 3a]. After disinfecting the root canal with calcium hydroxide during two weeks, MTA was placed to the apical part of the canal. The protocol for the creation of an apical plug with MTA was implemented as in Case 1. Figure 3b shows the radiographic appearance of the MTA filling in the apical 3 millimeters of the root. The remaining root canal filling was completed with gutta-percha and root canal sealer, with vertical condensation technique of the gutta-percha. The coronal third of the root was restored with a Ribbond fiber (Washington, the USA) and fluid composite (point4, Kerr, Bioggio, Switzerland). Composite-bonded resin and strip crown was used for the coronal restoration.

Figure 3

(a) A preoperative radiograph of maxillary left central incisor with an open apex in the third case of the case reports, (b) Radiographic evaluation of Mineral trioxide aggregate level in the third case of the case reports, (c) Follow-up at 1 year of the third case of the case reports

At 1 year follow-up [Figure 3c], the sinus tract had disappeared and healing of the radiolucent area and absence of clinical symptoms was registered.

DISCUSSION

Calcium hydroxide is the most commonly used material for apexification. It has had a high success rate when used for apexification treatment in several studies.[6-8] However, there are some disadvantages of this material. One of them is that the treatment requires a very long time which is from 3 to 21 months.[3] The required time is dependent on the diameter of the open apex, the rate of tooth displacement and the tooth repositioning method after trauma.[9] During a long period of time, root canal may be reinfected by the leakage of the temporary coronal filling. The success rate decreases by 10% in teeth with poor coronal filling.[3] Hence, performing a permanent treatment is better, as it avoids the reinfection of the root canal. Also there is possibility of fracture of the weakened teeth. After leaving calcium hydroxide in the root for more than 30 days, the fracture resistance reduces.[2] The patient's motivation is also one of the critical factors. Multiple appointments and esthetic problems may be a reason of patient complaint in the calcium hydroxide apexification treatment.[10]

In recent times, creating MTA apical plug in one visit is suggested for the treatment of the nonvital immature permanent teeth as an alternative to long-term apexification treatment. Lee and colleagues first described this material to dental literature in 1993.[11] MTA is a material which has less leakage, better antibacterial properties, high marginal adaptation, short setting time (~ 4 hours), a pH of 12.5 and is more biocompatible.[8] Scaffolding is provided for the hard tissue barrier by MTA.[4] A bioactive material MTA stimulates the production of interleukins and cytokine realese. So it is capable of promoting the hard tissue formation.[5] The clinician may restore the tooth after setting of MTA.[2] Thus, the fracture resistant of the teeth with thin dentinal walls increases. MTA can be used in teeth with pulp necrosis and inflamed periapical lesions because it may set in moist environments.[12]

In MTA plug technique, root canals must be disinfected with temporary calcium hydroxide dressing before placing MTA for two weeks.[13] This is because performing chemo-mechanical preparation alone is not effective for the complete elimination of microorganisms. Hence, we used calcium hydroxide dressing for two weeks in these cases. The clinician should not push MTA to the apical tissues for the treatment to be successful.[3] Using surgical microscope is proposed for an appropriate placement of MTA.[3] In these clinical cases, after calcium hydroxide medication, we placed MTA to the apical parts of the canals with a fitted gutta-percha cone under radiographic evaluation. In Erdem and Sepet's[12] clinical report, one of the cases in which MTA was extruded did not exhibit complete healing. According to their opinion reasons of the failure are width and unusual shape of the canal, difficulties at disinfecting the canal and dentinal tubules and the porous structure of the apical calcified barrier. Although MTA was extruded in our third case, healing of the periradicular area of the left central incisor can be seen at 1 year follow up on the radiograph [Figure 3c].

In these three cases, 6 months, 1 year and 18 months radiographic and clinical follow-ups revealed the supreme healing of the apical lesions and the regeneration of periradicular tissues. The clinical examination of these cases confirmed the suitability of this method and our results are similar to other cases[312131415] where the MTA plug technique was used for the endodontic treatment of nonvital immature teeth with an open apex.

CONCLUSION

MTA apical plug method is effective because of the less requirement of treatment time, appointments and radiographs, and better fracture resistance after the treatment of nonvital immature permanent teeth. Nevertheless, long-term studies should be done to test this method.