From Volume 41, Issue 7, September 2014 | Pages 596-604
The management of pulp necrosis in an immature permanent incisor can pose a significant challenge with regards to both operator technique and patient management. The main aim of this paper is to outline techniques described in the endodontic management of the immature incisor: calcium hydroxide apexification; one-visit apexification; and root revascularization.
The management of pulp necrosis in an immature permanent incisor can pose a significant challenge with regards to both the techniques and behaviour management. The aim of this paper is to outline the commonly described techniques in the endodontic management of the immature incisor, although it is appreciated that readers may have varying experience of these techniques and that in some cases these may be more appropriately completed in specialist centres.
The completion of root development of the permanent incisors normally occurs in childhood, eg the maxillary central incisor normally completes its root development before the age of around 10 or 11 years-old.2 Patients with non-vital immature incisors will therefore tend to be of a young age, which may pose challenges relating to their ability to co-operate for the required treatment. Although further discussion regarding behaviour management of the child patient is outwith the scope of this article, it is worth bearing in mind that management of the immature incisor may require multiple treatment visits over a prolonged period of time, precluding the use of general anaesthesia, and therefore highlighting the need for alternative behaviour management strategies.
Completion of root development and increase in the dentinal wall thickness is reliant on the presence of a vital pulp and functioning epithelial root sheath of Hertwig. When pulpal necrosis and cessation of root development occur in a tooth with an immature root, the apex will remain wide open with thin dentinal walls and a funnel-shaped root canal.
Once a tooth has been diagnosed as being non-vital, it requires endodontic management to eliminate bacteria from the root canal and facilitate the placement of a suitable root filling to achieve an optimal coronal and apical seal. The anatomy of the immature tooth, however, poses a number of challenges with regards to endodontic management, such as the following:
In a mature incisor, both shaping and cleaning are used to debride the root canal. Given its anatomy, shaping of the root canal in the immature incisor can be technically difficult and, moreover, excessive filling should be avoided as this may further weaken the already thin dentine walls. Debridement of the root canal in an immature tooth is therefore achieved through gentle mechanical cleansing with files, copious irrigation with sodium hypochlorite (NaOCl) and placement of an antibacterial intracanal medicament, such as non-setting calcium hydroxide. Irrigation with NaOCl must be carried out carefully, as accidental extrusion of NaOCl beyond the root canal system into the periradicular tissues may result in consequences such as pain, swelling, tissue damage and paraesthesia.3 To help prevent this, a side venting needle should be carefully measured to the estimated working length, inserted into the canal passively and the irrigant injected with minimal force. The use of a lower strength of NaOCl (0.5%) when irrigating teeth with open apices and compensating the decrease in strength by increasing the volume of irrigant4 has been suggested.
Adequate obturation of the immature root canal is made difficult by the absence of an apical barrier against which the root canal filling can be condensed. An example of this is shown in Figure 1, where conventional root canal treatment has resulted in extrusion of root canal filling beyond the apex. The following are the techniques which have been described to overcome this problem:
Figure 2 shows the same tooth as in Figure 1 following removal of the extruded root canal filling and replacement with an MTA hard tissue barrier and filling of the remainder of the root canal with thermoplastic gutta-percha.
There is a lack of available evidence relating to the effectiveness of these techniques.5 The description of these techniques is based on available evidence rating low on the hierarchy of scientific evidence. Therefore, the techniques may need to be re-evaluated in light of any well designed future research.
Calcium hydroxide apexification is a technique that aims to promote the formation of a hard tissue barrier at or near the apex of the tooth, which then allows a permanent root filling to be placed in the root canal. The technique involves completely filling the immature root canal with non-setting calcium hydroxide, following initial debridement of the canal, and then subsequently replacing the calcium hydroxide after one month and then at three-monthly intervals,6 until an apical barrier develops, following which the canal can be obturated either with thermoplastic or cold lateral condensed gutta-percha. Figure 3 shows a non-vital immature maxillary left central incisor before treatment. Figure 4 shows the same tooth following placement of a Ca(OH)2 dressing and Figure 5 following apical barrier development and obturation of the root canal with thermoplastic gutta-percha.
As the potential to mature is lost due to pulpal necrosis, this technique does not result in increasing root development or dentinal wall thickness. It is, however, a predictable technique, with success rates of between 95–100% reported in the literature.7,8,9 The average time required for barrier formation ranges from 5.1–12.19 months9 and requires an average of 1.9–4.2 calcium hydroxide dressing changes.7,8
The time taken for barrier formation is reported in the literature as being influenced by:
The presence of an abscess,8 periapical radiolucency7 or clinical symptoms prior to treatment9 are not reported to influence the time taken for barrier formation.
Despite the predictability of apical barrier induction, there are a number of disadvantages of this technique:
This technique involves non-surgical placement of a suitable material at the apex of an immature root canal, thereby creating a barrier against which a root filling of gutta-percha can then be condensed. A number of materials have been described, however, MTA is most commonly used for this technique.
MTA is a material similar to Portland cement. The major components are:
The technique for the placement of MTA as an apical barrier involves firstly debridement of the canal by gentle filing, copious irrigation and placement of calcium hydroxide dressing. An apical barrier of MTA is placed at a subsequent visit, provided the tooth is symptom free, and it has been suggested that at least a 4 mm apical barrier of MTA is most effective.12 MTA hardens (sets) optimally in the presence of moisture; some accept that the moisture required is derived from the surrounding (apical) tissues and dentine, allowing apexification and obturation of the remaining radicular canal in a single visit, while others would place a damp cotton wool pellet in the radicular canal, dress the tooth temporarily and obturate after the MTA would be expected to have hardened (set). Obturation of the remaining radicular canal is most easily carried out using a thermoplastic technique, eg SuperEndo Beta (B&L Biotech).
Figure 6 shows a non-vital immature maxillary left central incisor before treatment and Figure 7, the same tooth following placement of an MTA apical barrier and filling of the remainder of the root canal with thermoplastic gutta-percha.
There is limited evidence for the long-term efficacy of MTA as an apical barrier, and a recent review article suggests that, although current data shows that MTA can be used as an apical barrier in teeth with necrotic pulps and open apices, more investigations are needed to prove its long-term efficacy.13 Prospective studies have reported clinical success rates of 94.1%, with a follow-up time of 12.53 months (+/- 2.94 SD)14 and radiographic success rates of between 76.5% and 81%.14,15 A recent systematic review and meta-analysis, which compared the efficacy of MTA and Ca(OH)2 in the endodontic management of immature teeth, found no difference between materials regarding clinical success, radiographic success or occurrence of apical barrier.16
Placement of a hard tissue barrier with MTA has the following advantages over apexification with calcium hydroxide:
However, there are a number of disadvantages in using MTA for the endodontic management of immature incisors including:
Root revascularization (root regeneration, regenerative endodontic technique (RET)) is a technique first described in 200120 that can result in deposition of hard tissue at both the apex and the lateral dentinal walls, resulting in an increase in root length and thickness, thus strengthening a non-vital immature tooth against fracture.21
For revascularization of the dental pulp to occur, a specific clinical environment must exist. There must be effective disinfection of the canal, presence of a matrix into which new tissue can grow and effective sealing of the coronal access to resist further bacterial penetration.21
Banchs and Trope described that the technique involves:21
In the case described by Banchs and Trope, this technique was performed on a non-vital immature mandibular second premolar with a large periapical radiolucency, and then followed up clinically and radiographically.21 The periapical radiolucency completely resolved by 6 months; at one year there was radiographic evidence of continued apical development and at 2 years there was complete apical closure and obvious thickening of the dentinal walls. The authors suggested that, if no root development is seen within 3 months, then more traditional apexification techniques could commence.
The clinical evidence regarding the outcomes of this technique is limited to case reports, case series and small prospective trials. A prospective pilot study, using a different treatment protocol to that described above, suggested complete resolution of clinical signs and symptoms and appreciable healing of periapical lesions was evident in 79% of cases, thickening of dentinal walls in 57% of cases and increased root length in 71% of cases. No case presented with pain, re-infection or radiographic enlargement of pre-existing apical pathology.22 Another study with a study population of 12 indicated a high success rate for the 25% of patients for whom the procedure could be completed, with all patients exhibiting completion of root development and a positive response to pulp testing. However, the treatment was unable to be completed and evaluated for the remaining 75% of patients, either because of pain following placement of the triple antibiotic paste (22%), failure to induce bleeding after canal disinfection (44%) or failure to return for recall appointments (33%). This study therefore highlights potential technical challenges in completing the technique.23 A recently published study used a similar technique to that described above, with the exception that Ca(OH)2 was used as a canal disinfectant rather than the triple antibiotic paste originally described. After a follow-up period of 6–26 months, all 20 patients in the study had resolution of clinical signs and symptoms, radiographic evidence of periapical wound healing and thickening of the dentinal walls, while 75% had radiographic evidence of continuing root development. In addition, 20% of patients had radiographic evidence of pulp canal obliteration and 10% formed a hard tissue barrier in the pulp canal space between the MTA plug and the apex.24
A recent review article concluded that, while available low level evidence indicated the pulp-dentine complex has the potential to regenerate in necrotic immature permanent teeth, that studies with higher levels of evidence are needed to confirm the findings.25
Figure 8 shows a non-vital immature maxillary right central incisor before treatment. Figure 9 shows the same tooth following the process of canal debridement with NaOCl and triple antibiotic paste, stimulation of a blood clot matrix and placement of an MTA plug. Following a three month review, thickening of dentinal walls and continuing root development is evident radiographically (Figure 10).
Advantages of this technique include:22
This paper highlights the potential difficulties involved in the endodontic management of the non-vital immature incisor, including debridement of the root canal due to its shape, possible irrigant and medicament ejection due to the open apex, and difficulty condensing root-filling materials as a result of a lack of an apical constriction or barrier. The authors have described the techniques which overcome these difficulties and, while some may be more suited to specialist centres, it is hoped that knowledge of these techniques will aid the general dental practitioner in selecting an appropriate management option.
