Unraveling intertwined incisor roots
Published: July 2014
Bulletin #35 - July 2014
Unraveling intertwined incisor roots
Fig. 1. The smile and initial intraoral photographs, showing the missing left central incisor and midline deviation
The patient was a female who was due to be drafted into the Israeli Defense Forces to fulfill her compulsory 2-year national service, shortly after commencing her orthodontic treatment. At 18 years of age, she had been referred to me by a colleague for the treatment of her impacted dilacerate maxillary central incisor. The space in the dental arch for the tooth had almost completely closed due to the mesial drifting of the two adjacent incisors (Fig.1). Her malocclusion was defined as Angle’s class 2 division 2 subdivision of the left side, where there was a cusp-to-cusp post-normal (class 2) relation. The teeth of the right side were correctly occluding in a class 1 relation. The lower arch was fairly well aligned. The left central incisor was palpable on the labial side of the arch within the protruding, thick and fleshy midline frenum.
This case was one of four which were presented in a discussion of pre-eruptive intracoronal resorption (PEIR) in the July 2013 bulletin #24 in this series, the features of which were illustrated in the radiographs and the CBCT of her dilacerate tooth.
Fig. 2a. The initial panoramic view showing the unerupted dilacerate left central incisor, showing pre-eruptive intracoronal resorption (PEIR) in its mesial incisal edge corner (arrow)
Fig. 2b. The lateral cephalogram shows the degree of displacement of the incisor crown and the curved root.
The “classic” type of dilacerate central incisor is generally accepted as being the result of trauma to the anterior dentition in the second or third year of life. 1 It features a malformed root which takes the form of a tight upward curve in the antero-posterior plane, bringing the crown tip high in close relation with the anterior nasal spine (see video in bulletin # 28 December 2013 http://www.dr-adrianbecker.com/page.php?pageId pageId =273).
Fig. 3a & b. Screen shots from the CBCT. The PEIR lesion is plainly seen (arrow)
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Fig. 4a. An axial (horiozontal) cut from the CBCT showing the curvature of the dilacerate incisor wrapped palatally around the root of the lateral incisor
Fig. 4b. A transaxial (vertical) view of the lateral incisor showing its intimate relation to the root of the central incisor.
There is little or no rotation of the tooth and no mesio-distal displacement of crown or root apex. In the present atypical case, as seen in the radiographs (Fig. 2) and CBCT (Fig. 3) the antero-posterior curvature of the root was less pronounced, but there was a marked degree of distal displacement of the root apex, while a small section of the apical portion of the root exhibited a sharp distal bend. This resulted in the palatal and distal location of the root of this tooth in relation to the root of the adjacent lateral incisor (Fig. 4). There was accompanying mesial displacement of the crown to well beyond the maxillary anatomic midline. The root of the lateral incisor on the same side was displaced labially to a mild degree and would later require lingual root torque to idealize its alignment. As noted in the July 3013 bulletin #24 (http://www.dr-adrianbecker.com/page.php?pageId=281&nlid=59), the PEIR lesion was seen in the mesial corner of the incisal edge of the crown.
The reason for presenting this case in this month’s bulletin is that both the antero-posterior curve of the root and the distal bend in its apical portion must be considered serious impediments to the attainment of an ideal positional correction of this tooth, in the 3 planes of space, since root uprighting and labial root torque are required. This was achieved while maintaining the vitality and integrity of the existing anatomy of the tooth, without having to resort to apicoectomy and root canal therapy. The only ancillary treatment performed was the restoration of the PEIR lesion in the mesial incisal corner of the crown of the tooth.
Fig. 5a & b. Evaluating the relationship of the hooked root end of the central incisor to the lateral incisor, using the tube shift (parallax) method.
Following a careful evaluation of the radiographic and CBCT images of the immediate area (Fig. 5), treatment was commenced, with the initial object being the creation of space in the arch. Tip Edge Plus brackets (TP Orthodontics) were bonded to the maxillary teeth, which were aligned and space regained for the impacted central incisor using a coil spring, within 10 weeks. At the time of referral to the oral surgeon, 2 weeks later, a 0.020” round steel archwire was in position, threaded with a stainless steel tube of 0.036” gauge holding the space between the brackets of the adjacent erupted incisors. In this way, all the maxillary teeth were integrated into a single anchor unit, in preparation to accept the reactive forces that would counter the forces that would be aimed at resolving this maximum anchorage impaction.
Surgical access to the tooth was gained by a labial approach, in which a labial muco-gingival flap was raised from the crest of the alveolar ridge, with vertical releasing incisions to enable exposure of the tooth high in the labial sulcus (surgery by Dr. Harvey Samen). The PEIR lesion was clearly seen and was sealed off with composite bonding material, without any attempt made to excavate the mush within. The rationale for this is that the lesion is not carious, but it is non-bacterial and completely sterile, receiving its nutrient supply through the dental follicle, from which it was now isolated by the composite filling.
The treatment provided in this case closely followed the description of these cases in general, as described in Bulletin #11 – May 2012 – Treatment of the “Classic” Dilacerate Maxillary Incisor http://www.dr-adrianbecker.com/page.php?pageId=281&nlid=30 in this site.
An eyelet attachment was bonded to the palatal aspect of the incisor crown’s anatomy (the under surface), using light-cured bracket bonding material, with a twisted soft stainless steel ligature of 0.012” gauge thread through it. No attempt was made to expose the tooth more than the minimum size requirement to accept the small attachment, while hemostasis was controlled by the surgeon. The bonding procedure was performed by the orthodontist who was in attendance and needs to be responsible for attachment location and for the direction that the ligature wire should be drawn and where and how it should exit the surgical wound. The flap was re-sutured back to its former place, with the pigtail ligature drawn through its sutured lower edge. The tooth was now completely re-covered by the surgical flap (closed surgical exposure), with only the free end of the ligature visible. This was shortened and turned upwards into a hook, flush with the alveolar ridge. An elastic chain was stretched between the brackets of the two adjacent teeth and its middle portion was drawn upwards to engage the ligature hook and, thereby, to apply the initial extrusive force.
Over the ensuing 2 months, the tooth was drawn down until it bulged the mucosa on the labial side of the ridge and appeared about to erupt too high on the ridge, in the loose oral mucosa. This occurs frequently with the dilacerate incisors and, in order to avoid this outcome, simple periodontal surgery is needed. A second labial flap was raised at this time, again including attached gingiva, its edge raised and sutured to the labial side of the crown of the tooth (apically repositioned flap). Further extrusive forces brought the crown of the tooth occlusally. Once the labial side of the tooth was adequately visible and accessible, the palatal eyelet was removed and the patient referred to the dentist to restore the PEIR affected mesial corner of the tooth. On the same day, a new eyelet was bonded to the labial side and traction was renewed to bring the tooth to the occlusal level.
The entire duration of downward traction was only 3 months, before a Tip Edge Plus bracket could be substituted for the labial eyelet and a new 0.020” round steel base arch engaged in all the brackets.
Fig. 6a. An occlusal view of the maxillary dentition showing the considerable degree of labial root torque needed for the central incisor. Note that the lateral incisor needs to be lingually root torqued, but to a much lesser degree. The patch of composite bonding material seen on the cingulum area was the site of the initial eyelet attachment and was removed at this stage.
Fig. 6b. A torqueing auxiliary for a single tooth.
Fig. 6c. The torqueing auxiliary is first ligated into the bracket of the tooth, under the heavy (0.020”) steel round main arch.
Fig. 6d. A side view of the initial ligation.
Fig. 6e. The long arms of the auxiliary are ligated under the main arch to introduce a labial torqueing moment on the central incisor. In contrast to a rectangular archwire, this does not cause reciprocal lingual torque on the adjacent teeth. At the same visit, uprighting springs were placed in the vertical slots of the central and lateral incisors in a move to distance their root apices from each other, thereby permitting the intended movement.
The anterior dentition at this point included a right maxillary central incisor which required distal root uprighting, a left lateral incisor which required minor distal root uprighting and a degree of lingual root torque. The crown of the newly erupted dilacerate left central incisor clearly indicated the need for much labial root torque and mesial root uprighting, although it was obvious from the radiographs that the terminal bend in the root of this tooth would only permit corrective movements of the two left incisors to a minimal degree (Fig. 6).
An auxiliary torqueing spring was constructed of 0.016” stainless steel and is illustrated in figure Fig. 6b. Its placement and activation is shown in Fig. 6c-e. This was left in place for 3 months and, simultaneously, an auxiliary uprighting spring was placed in the lateral incisor bracket to move its root distally. This could be described as over-corrected uprighting, whose aim was to permit the root end of the central incisor to be torqued labially notwithstanding the bend in its root apex.
Fig. 7a. Only when much of the labial root torque had occurred, a reciprocal torqueing spur was used to lingually torque the lateral incisor, while continuing the labial torque on the central incisor.
Fig. 7b. A close up view of the two incisors shows the reciprocal torqueing spur placed behind the main arch, while a “sidewinder” uprighting spring is placed in the vertical slots of the Tip Edge brackets, to distance the root apices from each other.
Fig. 8a. The anterior section of the panoramic view on the day appliances were removed, shows the minimal degree of separation of the incisor root ends. The restoration of the incisal edge PEIR lesion can be seen.
Fig. 8b. A periapical view on the same day shows a periapical area of bone resorption that appears to be an abscess. However, the tooth responded to vitality testing. Follow-up radiographs are therefore expected to show bony fill-in in the future.
Fig. 8c & d. The before and after lateral cephalograms show the amount of labial root torque achieve during treatment. The arrows indicate the apex of the dilacerate incisor. The apex was not unduly prominent in the labial sulcus and, accordingly, apicoectomy and root canal therapy were not undertaken.
Labial root torque with an auxiliary like this is very rapid. However, it was quickly seen that the root of the lateral incisor was being adversely torqued in a labial direction, which indicated that the roots had clashed despite the precaution taken, with the central incisor still under-torqued. Accordingly, an uprighting spring mechanism was placed on the central incisor in order to move its root towards the anatomic midline. Thus, opposing mesio-distal uprighting movements of the central and lateral incisors were undertaken at the same time, in an effort to provide space in the apical region for the roots ends to correct their existing reversed bucco-lingual relationship. At the same time, a simple reciprocal torqueing auxiliary rapidly effected the lingual root torque of the lateral incisor and labial root torque of the central incisor (Figs. 7, 8).
Fig. 9. Intraoral views taken on the day appliances were removed and the maxillary twistflex splint was placed.
Much of the treatment time was involved in treatment of the incisor tooth and the various forces that were brought to bear had to be resisted by the remaining teeth, including those in the lower jaw with the use of intermaxillary forces. The illustration in Fig. 9 shows the alignment and occlusion at the end of 26 months of orthodontic treatment. The influence that midline correction had on the patient’s smile was quite dramatic (Fig. 10).
Fig. 10a & b. The juxtaposed pre- and post-treatment smiles to show the achieved alignment and midline correction.
The final periapical radiograph (Fig. 8b), taken on the day appliances were removed, shows a circumscribed area of radiolucency around the dilacerated root apex of the central incisor. Since the tooth has responded to vitality testing and is symptomless, it is hoped that this represents an area of immature bone that is the result of the extensive root movement of the tooth, which will disappear as further calcification proceeds. Careful radiographic monitoring has been introduced to oversee developments during the succeeding months.
Reference
1 ..1. Topouzelis N, Tsaousoglou P, Pisoka V, Zouloumis L. Dilaceration of maxillary central incisor: a literature review. Dental Traumatology 2010;26:427–433.
