NEWSLETTERS

Treatment of the "Classic" Dilacerate Maxillary Incisor

Published: May 2012

Bulletin #11 - May 2012

Treatment of the "Classic" Dilacerate Maxillary Incisor

In last month’s bulletin (Bulletin #10 April 2012 on this website), an overall approach to the resolution of the “classic” dilacerate maxillary incisor was recommended and it was pointed out how an understanding of the manner in which this unique and very special anomaly occurs is basic in guiding us in our treatment. It was emphasized that, in spite of the grossly disfigured form of the root of this central incisor and its extreme ectopic location, it is possible to bring it into its designated place in the dental arch, to make it appear indistinguishable from the healthy and beautifully-formed contralateral central incisor and to do so with a very fair prognosis. This is no mean feat, since the affected tooth and the normal “next-door-neighbor” are destined to be placed side by side at the front of the mouth, inviting the strictest standards of comparison. However, by applying accepted and logical procedures in the orthodontic, oral surgery and periodontal management of the case, results can be enormously satisfying from every point of view.

A single case of a dilacerate central incisor and extreme dislocation of the crown of the incisor, displaced into the anterior nasal spine, will be presented and followed from the mixed dentition period, through to the patient’s mid-teens, several years after treatment had been completed and the patient was in retention. Other cases will be introduced to illustrate certain different procedures which have advantages in specific situations and may be preferred.

Fig._1a_d

Fig. 1 The presenting condition (case 1), a. the anterior intra-oral view, b. the view of the palpable incisal edge of the dilacerate tooth, c. the panoramic view, show the relationship between the tooth and the anterior nasal spine and, e. the lateral view, showing the extreme vertical displacement of the incisal edge. (Several of the illustrations of this case appeared in an earlier article by the author in Seminars in Orthodontics1 and are published here with the kind permission of Elsevier Inc.)

Case description

When first seen, the patient was a 10.7 year old female who had a history of trauma to the front of the mouth as the result of a fall, at the age of 2.6 years. The parents’ concern for seeking treatment was that the right central incisor and both lateral incisors had erupted and there was no sign of eruption of the left central incisor, despite the fact that its deciduous predecessor had shed 3 months earlier (Fig. 1a).

The clinical examination revealed a normal facial profile, normally related jaws, a mixed dentition with a class 1 relationship of the molars and no crowding. Although the lateral incisor on the affected side was tipped mesially, there was almost adequate space for the unerupted incisor, which was palpable by raising the upper lip and displacing the frenum very high in the reflection of the sulcus, within and slightly to the left of the anterior nasal spine (Fig. 1b). All four permanent first molars, 4 mandibular and 3 maxillary incisors had erupted and the deciduous canines and molars showed no signs of pre-shedding mobility. The teeth were caries free and the patient’s oral hygiene was good.

The initial records that were commissioned included a panoramic and periapical views, a cephalogram (Figs. 1c & d) and plaster casts of the teeth, together with cone beam CT imaging. The CBCT was performed on an early NewTom machine which has long since been put out to grass.

From the radiographs, it was noted that all permanent teeth were present and in various stages of development, permitting an assessment of dental age of the patient at 9 years (Fig. 1c). On the basis of the clinical examination and these records, an orthodontic treatment plan was formulated for the immediate future and was restricted to the resolution and alignment of the impacted incisor. It was calculated that a second phase of treatment would be necessary in the permanent dentition. For exposure of the impacted tooth, a 2 stage surgical intervention was planned, with the predicted future need for root canal treatment and apicoectomy of the dilacerate central incisor.

Orthodontic preparation

Fig._2a_c

Fig. 2 The modified Johnson “twin-arch” appliance (case 1) showing the sectional anterior light 0.016”) wire, held in long buccal 0.020” tubular arms, which are slotted into 0.036” soldered molar tubes. There is also a soldered cut-back palatal arch (unseen).

Plain orthodontic bands were fitted to the maxillary first permanent molars and an impression taken with them in place. The bands were then removed from the teeth, relocated in the impression and a model was cast. On the plaster model, a cut-back palatal arch was prepared and soldered to the bands, while 0.036” round tubes were soldered on the buccal side. A modified Johnson “twin” arch, whose buccal tube sections were 0.036” external diameter and 0.020” internal diameter, was also prepared, with an anterior sectional arch of 0.016” wire. These buccal tube sections were a sliding tube-within-a-tube fit into the soldered buccal tubes, while the 0.016” sectional archwire was held in the buccal tube sections by incorporating a few bends in the wire and drawing it through to its appropriate length. This provided the buccal part of this complex archwire with rigidity and direction, while the anterior portion was provided with flexibility.

In mid-March 2003, the molar bands with associated soldered palatal arch were transferred to the mouth and securely cemented into place. Brackets were then bonded to the three erupted incisors and the composite Johnson archwire ligated into place to achieve initial leveling and appropriate space opening in the central incisor location, as needed (Fig. 2a-c). Once this had been achieved, a measured length of stainless steel tube was threaded on to the anterior portion of the composite archwire and ligated firmly between the brackets of the erupted adjacent teeth, to hold the achieved space and to establish a degree of stability against the intended application of extrusive forces.

In these cases, I have a personal preference for the placement of simple Begg brackets on the incisors, because archwire insertion is into a vertical slot, which is particularly efficacious when dealing with teeth that need to be vertically extruded. Nevertheless, any bracket type may be used, according to operator preference. In general and as seen in this case, the soldered palatal arch and the erupted and ligated incisor teeth provide adequate anchorage for most situations of this nature.

Fig._3a_d

Fig. 3 This illustration shows an alternate design for increased anchor needs on another patient (case 2). Brackets have been bonded to the deciduous canines and molars and the palatal arch has been augmented with a Nance acrylic button, to enhance the resistance of this composite anchor unit.The credit for this approach is attributed to Prof. Dr. Herman van Beek of Amsterdam.

Should it be desired, the anchorage may be further enhanced if orthodontic brackets are also placed on the deciduous canines and molars, together with the addition of an acrylic Nance Button on the palatal arch (Fig. 3a-d). In this situation, a standard sequence of full length archwires may be placed in the usual manner, to achieve leveling and space opening, prior to the placement of a similar stabilizing heavier arch immediately before surgery.

Surgical exposure

In mid-May 2003, the patient was referred to the oral surgeon, with the view to his exposing the tooth to provide access for the application of extrusive forces.

In all these cases, a decision must be made together with the oral surgeon or periodontist and ahead of time, as to what type of exposure should be executed. This should not be considered their business alone and, in many ways, the initiative for a preferred approach should come from the orthodontist. If direct exposure is made through the oral mucosa – the so-called “window” technique - it needs to be made immediately opposite the tooth, very high and close to or even above the mucosal reflection in the sulcus. This creates several problems:-

1. in the post-surgical follow-up, the soft tissue will heal over and access will be lost.

2. the natural progress of the tooth is upwards and backwards, with no chance of spontaneous eruption being evoked by the exposure.

3. placement of an attachment at the time of surgery will be obligatory

4. when the tooth is erupted through this portal, it will be invested with thin unattached oral mucosa on all its sides.

5. the eventual outcome will be characterized by a long clinical crown and very thin, mobile and easily damaged mucosal tissue.

The use of a partial thickness attached gingival tissue apically repositioned pedicle graft taken from the alveolar ridge2 also presents problems:

1. the distance for this distance that this graft has to be repositioned is great and the vertical releasing incisions will extend into the lip tissue. 

2. the excess flap tissue will be difficult to disperse and will re-bury the exposed tooth.

3. placement of an attachment at the time of surgery will be obligatory

4. a large area of exposed and sensitive submucous connective tissue will need to be dressed with periodontal pack for a few weeks.

5. the eventual outcome will exhibit a tooth with unsightly lumpy gingival architecture of attached gingiva and a long clinical crown.

A closed surgical exposure is the only remaining alternative3 and this was the procedure that was performed in this case. However it, too, has problems that need to be considered in relation to the dilacerate central incisor and it is only appropriate for the early stages of the resolution of the impaction:

1. an attached gingival flap needs to be raised all the way up to the impacted tooth and an attachment must be placed on the tooth. A pigtail ligature or gold chain needs to be drawn down to exit the fully re-sutured flap at its inferior edge on the crest of the ridge .

2. placement of an attachment at the time of surgery will be obligatory

3. as the tooth comes down, the incisal edge will become labially prominent and there is a distinct possibility of its erupting through the thin and loose labial oral mucosa.

4. accordingly, at this stage an apically repositioned flap procedure will need to be undertaken to place gustatory attached gingiva on the labial side of the tooth.

Nevertheless, when properly executed, the combination of a closed eruption exposure and a subsequent apically repositioned flap procedure provides the optimum conditions for achieving a good outcome, as seen in the case displayed in last month’s bulletin (Bulletin #10 April 2012 on this website) and in the examples presented here.

Fig.4a_d

Fig. 4 a. At surgery (case 1), a wide full thickness flap was raised from the crest of the ridge and minimal bone was removed over a small area of the distal and palatal aspects of the tooth and an eyelet was bonded to the labial-facing palatal surface. A twisted soft steel ligature wire was threaded through the eyelet (green arrows) before the surgical flap was resutured in its former position, in a closed eruption procedure. b. A cut and curved steel tube maintains the prepared incisor space. An elastic chain, drawn between the attachments on the adjacent teeth, was raised to engage its middle portion over the twisted steel ligature, which was fashioned into a hook (yellow arrows) to provide light extrusion force. c. within a few weeks, the palpable bulge of the incisor could be seen to descend (blue arrow), as the elastic chain flattened out, losing its potency and requiring to be re-activated by rolling up the twisted ligature hook and re-attaching a new elastic chain. d. The tooth came down further and appeared to be ready to erupt through the oral mucosa, above the attached gingival (purple arrow). The patient was referred back to the surgeon for the second surgical episode.

An eyelet attachment was bonded on the anatomic palatal aspect (the underside) of the crown of the incisor (Fig. 4a) by the orthodontist at the time of surgical exposure, with a twisted steel pigtail ligature being drawn from the eyelet downward and held in place by the fully replaced and sutured flap. Its end was then shortened and turned upwards to form a hook. This was all performed under local anaesthetic cover.

Orthodontic extrusive traction

Before leaving the surgeon’s operating room, an elastic chain was stretched across the edentulous space which had been enlarged to accomodate the aberrant incisor, between the brackets of the adjacent teeth and the space maintained and stabilized by the inter-bracket tube that had been placed on the archwire. The middle section of this tensed elastic chain was then gently raised to engage the hooked end of the pigtail ligature, to apply immediate and measurably light extrusive force of good range to the dilacerate tooth (Fig. 4b). The tooth responded rapidly and, by the beginning of August 2003, its incisal edge could be seen to bulge the labial oral mucosa covering the lower part of the labial aspect of the alveolar ridge, with the distinct danger of erupting above the attached gingiva (Fig. 4c, d).

Fig._5a_d

Fig. 5 a. A new flap of attached gingiva was again taken from the crest of the ridge (case 1), and raised over the incisal edge of the tooth, where it was sutured, in the manner of an apically repositioned flap, leaving the incisor exposed. Further traction was applied to the palatal eyelet, until the labial aspect of the tooth became more exposed. b. A new eyelet was placed in a vertical orientation on the labial aspect of the tooth and further traction applied by threading the NiTi archwire through the new eyelet. The initial eyelet was removed. c. With the crown in alignment, there was about 900 of labial root torque needed to align the labial face of this tooth with its antimere. d. Labial root torque was applied until the root apex was in danger of piercing the labial sulcular mucosa (arrow). The appliances were then removed and further treatment delayed until the full permanent dentition had erupted.

The need for additional surgery

So, a second surgical episode had to be planned, in order for the tooth to be invested in attached gingiva and not with loose oral mucosa. For this, an apically repositioned flap was raised from the crest of the ridge, under local anaesthetic cover and re-located over the incisal edge, on the anatomic labial side of the tooth (Fig. 5a).

Further orthodontic extrusion

Six weeks later, in September 2003, traction from the initial palatal eyelet had brought the tooth further occlusally and, following a short period of traction with a bonded labial eyelet (Fig. 5b), a broad enough site for optimum bracket bonding had become accessible on the labial aspect. The eyelets were removed and a standard bracket placed in it ideal location on the anatomic labial aspect of the tooth (Fig. 5c). The anterior section of the labial arch and steel tube space maintainer were then removed and substituted by a NiTi anterior section for final crown leveling.

With the teeth aligned and leveled, the long axis of the crown of the tooth required approximately 90 degrees of labial root torque for the labial side of the crown to to reach its normal orientation (fig. 5c). This task was commenced in December 2003 and continued until the fixed appliance was removed and replaced by a simple removable Hawley retainer after 14 months of treatment. This occurred in May 2004 and its timing was determined by the appearance of a hard tissue bulge in the labial alveolus, identified as the root apex of the tooth (Fig. 5d). Further root torque was needed, but not appropriate at this stage, since this would have required an apicoectomy and root canal treatment, which should only be performed as an integral part of the artistic finishing in the full permanent dentition. With deciduous molars still present and permanent teeth unerupted, phase 2 treatment was still some time in the future.

Phase 2 orthodontic treatment

Fig.6a_c

Fig. 6 At age 14.2 years (case 1), treatment was re-started and a fully bracketed Tip-Edge set up was placed, with an auxiliary Begg-type torqueing auxiliary tied into the bracket of the dilacerate incisor. Full root torque was performed, followed by a root canal treatment. a. The palpable bulge of the labially-facing root apex tooth was clearly seen (arrow). b. Merely raising the flap exposed the very prominent apex (arrow). c. The apex was amputated and the root filling can be clearly seen on the illustration (arrow).

In September 2006, at the age of 14.2 years, orthodontic treatment was re-commenced with the view to aligning all the permanent teeth and to complete the labial root torque of the incisor. Apicoectomy with root canal treatment of the incisor was performed in January 2007 (Fig. 6) and appliances were removed in late April 2007. A twistflex retainer was bonded to the palatal aspects of the 6 maxillary anterior teeth. In addition, a similar retainer was bonded on the labial side of the two central incisors and left in place for a year, before being removed.

Fig.7

Fig. 7. The case seen in mid-April 2012, 5.0 years after completion of the treatment (case 1). A twistflex lingual bonded splint is present.

Fig.8Fig. 8 The periapical view mid-April 2012, 5.0 years after completion of the treatment shows excellent bone condensation around the root of the affected incisor and depicts how the root canal filling turns a 900 angle, terminating at the vertical amputation face.

Post-treatment follow-up

The patient has been seen periodically since the completion of treatment. In late 2010, the patient complained of a relapsed proclination of the dilacerate tooth which was found to have become detached from the palatal bonded splint. Wearing a new Hawley retainer over the existing splint with activated labial arch brought the errant tooth back into alignment within 2 weeks and it was rebonded to the splint without further complications.

Critical review

Given the extreme initial displacement of the crown of the tooth, the extreme curvature of its root, the extreme degree of labial root torque that would be necessary, the extreme root amputation required and the root canal treatment that that would entail, what sort of prognosis could be offered for such a tooth? Until about 25-30 years ago and like most of my colleagues even today, I saw no future in attempting to offer such treatment. Indeed the only advice that I would offer at that time4 was to extract the tooth, to remove its entire root portion and to preserve the perfect crown. I would then clean out and fill the pulp chamber with filling material and bond the crown into its desired place, between the two adjacent incisors, in the hope that this would hold until the very young patient reached an age when a permanent restoration could be placed – which, in that pre-implant era, meant a fixed bridge.

It came as a complete surprise to me to see the results that are achievable, when I first started treating these teeth conservatively. For this to happen, it is my firm conviction that it is imperative to follow a logical sequence of treatment procedures that involves mutual understanding and close cooperation between the surgeon/periodontist and the orthodontist. It also involves an awareness of the need for appropriate timing of these procedures in relation to the development of the dentition as a whole. Much root torque is needed in the phase 1 treatment stage and the determinant for stopping the movement must be the appearance in the labial alveolus of an obvious bulge of the periosteum covering the root apex, beneath the mucosa. In some cases, full torque can be achieved without the appearance of an excessive bulge, in which case apicoectomy is unnecessary, as seen here in case 3 (Figs. 9-12) and as demonstrated last month on this website (Bulletin #10 April 2012). However, labial orthodontic relapse of the tooth will occur if further root development or even mere apexification of the tooth continues, since it takes place in close contact with the labial periosteum. This displaces the apex lingually and causes a labial relapse of the crown, tipping it labially.

Fig.9

Fig. 9 A similarly dilacerate right incisor in another patient (case 3), presented in the anterior intra-oral, occlusal and occlusal radiographic views.

Fig._10

Fig. 10 Tangential (true lateral) and periapical views of the tooth (case 3) on the day that surgical exposure was undertaken and an attachment bonded. Both films show the severity of the displacement and the distance that must be traveled by the tooth to reach alignment and before root movement is initiated.

Fig.11

Fig. 11 The case (case 3) seen in mid-April 2012, 8.3 years after completion of treatment.

Fig.12

Fig. 12 The occlusal intra-oral and periapical radiographs views seen in mid-April 2012, 8.3 years after completion of treatment. As with the case illustrated in last month’s bulletin (see Bulletin #10 April 2012), apicoectomy was not needed in this case.

Follow up of these cases over the post-treatment years has shown a remarkable longevity for these teeth, with no deterioration in their immediate post-treatment appearance, but they do need to be monitored periodically to be sure that the splint is intact. From our experience with the results of the above treatment protocol, there is ample reason to be confident of seeing these compromised teeth last for many years beyond adolescence and well into adulthood. Certainly, when the terminal demise of the tooth is at hand, there will be plenty of alveolar bone in the area to accept a future implant. It should be remembered that considerable amounts of alveoloar bone will have been generated by the eruption of the tooth (Figs. 8, 12), in stark contrast to the gaping defect that would have resulted had the dilacerate tooth been extracted in the early mixed dentition period.

In a few cases, the only “fly in the ointment” is likely to be intrinsic discoloration that is a by-product of the endodontic treatment. The tooth will then be distinguishable more because of its root canal treatment, rather than for its having been an impacted tooth (Fig. 7).

References

  1. Becker A. Extreme tooth impaction and its resolution. Seminars in Orthodontics, 2010, 16:222-233.
  2. Vanarsdall R, Corn H. Soft tissue management of labially positioned unerupted teeth. American Journal of Orthodontics, 1977; 72:53-64
  3. Vermette M, Kokich V, Kennedy D. Uncovering labially impacted teeth: Apically repositioned flap and closed-eruption techniques. Angle Orthodontist 1995; 65:23-32
  4. Becker A, Stern N, Zelcer Z. Utilization of a dilacerated incisor tooth as its own space maintainer. Journal of Dentistry, 4:263-264, 1976