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Impacted canines and severe incisor root resorption: the ultimate orthodontic challenge

Published: February 2017

Bulletin #63  February 2017
Impacted canines and severe incisor root resorption: the ultimate orthodontic challenge

From a series of studies that we have published over the past few years,1-8we have learned muchinteresting and clinically relevant informationregarding the resorption of the roots of incisor teeth associated with impacted maxillary canines. This has been particularly valuable to us because it has allowed us to offer orthodontic treatment as a reasonable approach to many of the more extreme problems, where extraction would previously have been the only seemingly logical option. With some confidence, we have essentially brought many of the more severely affected resorption cases into our day-to-day clinical practice, with the expectation that they will respond to conservative, conventional orthodontic treatment and still offer a reasonable prognosis in the medium to long term.
Still today, many patients with clearly identifiable root resorption are offered extraction as the only line of treatment. In some of these cases, competent orthodontists are unprepared to accept the responsibility for what appears to incur a significant risk of failure - often motivated by the fear of subsequent legal repercussions.
Because of my interest in this specific area, a large proportion of my patient load comprises individuals with impactions of one sort or another (around 40%!) and many are referred from far and wide.The case that I present this month is by no means the only case of its type to have walked into my office, but it has certainly been one of the most severe and the most challenging.

The patient63. 1_1

Fig. 1. Intraoral view of the teeth in occlusion before treatment, taken at the first visit to my office in November 2014. The maxillary left premolar is erupting mesial to its deciduous predecessor, into the canine location (arrow).


A girl1 aged 11.3 years was seen in April 2014, diagnosed and treatment planned by a resident studying in one of the four graduate orthodontic department programs in Israel. As is common in educational programs, this process had taken several months before the patient was informed that the prognosis for the success of any orthodontic intervention was too poor to be considered for treatment in the department and, no doubt, beyond the capabilities of an inexperienced graduate student.

63._2

Fig. 2. Occlusal views of the teeth before treatment, in November 2014. The maxillary left premolar is erupting mesial to its deciduous predecessor, into the canine location (arrow).


To her first appointment in my office, in November 2014, the parent brought the radiographs, cephalometric analysis, facial appraisal and all the other diagnostic aids normally used in the deliberations leading to a plan of action. On examination, the child exhibited a convex profile, with a retrognathic lower jaw and a high lower lip lineat rest, in relation to the maxillary incisors. She was in the late mixed dentition stage, with retained deciduous second molars and maxillary deciduous canines. The mandibular canines and three of the deciduous first molars had shed during the past months. The premolar teeth, the lower permanent canines and the permanent second molars were in various stages of eruption. The molar relations were slightly class II on the right and a full unit class II on the left side (Figs. 1, 2). The four maxillary incisors were at different heights, flared distally, notably mobile (grade II mobility), the maxillary dental midline deviated 1-2mms to the right and the mandibular dental midline 2mms to the left. The maxillary and mandibular incisors were retroclined and the overbite deep, with an 80% vertical overlap and contact of the lowers high up on the cingulum of the uppers. The confirmatory cephalometric values were typical of a low Angle’s class II division 2 malocclusion.

63._363._3c

Fig. 3a-c. Initial panoramic, periapical radiographic views and cephalogram in April 2014.

From the initial panoramic and periapical views (Fig. 3a, b), taken in April 2014, the maxillary canines could be seen to be impacted and severely tipped towards the midline (‘kissing canines’) and the roots of each of the four incisors were resorbed down to the CEJ. The lateral cephalogram (Fig. 3c) showed the superimposed right and left canines posteriorly located to the long axes of the incisors and, since these crowns were in the midline area and given their long axis orientation, it was concluded that they had approached the incisors from the palatal side and had proceeded to encroach into the recently-created resorption craters in their roots. This was confirmed on the CBCT cross-sectional images, from which the severity of the resorption could be seen (Figs 4a-d) and the 3D video clip which was prepared from a very poor scan (Fig. 4e).
63._4

Fig. 4a-d. Cross-sectional views from the cone beam CT images across each of the maxillary incisors to show the relationship between the impacted canines and the incisors and the severe degree of root resorption.

Fig. 4e. A 3D CBCT video clip - click here.


Problem list
1.    Impacted canines
2.    Resorbed incisors with poor prognosis
3.    Retroclined upper and lower incisors
4.    Excessive curve of Spee – deep incisor overbite
5.    Unilateral class II relation
6.    Crowding in the maxillary dentition
7.    Midline discrepancy

Treatment options
a.    No orthodontic treatment. Ignore the class II relation. Refer for prosthodontic treatment
b.    Extract the impacted canines without orthodontic treatment. Ignore the class II relation. Refer for prosthodontic treatment
c.    Extract the 2 or 4 incisors and bring the canines into the incisor place. Ignore the class II relation
d.    Extract the 4 incisors and bring the canines into the place of 2 incisors – with prosthodontic replacement of the other two. Ignore the class II relation
e.    Extract the 4 incisors and the canines– with prosthodontic replacement of 6 anterior teeth. Ignore the class II relation
f.    Attempt orthodontic treatment to resolve the canine impaction and align the maxillary incisors.
Resolve the class II relation and midline discrepancy.
g.    Attempt orthodontic treatment to resolve the canine impaction and align the maxillary incisors. Ignore the class II relation.

A critical look at the treatment options
It was recognized that denial of some form of treatment would result in further damage, with continued resorption, loss of the four incisor teeth within a short time and the likely eruption of the canines with a strong mesial orientation, close to the midline. On the other hand, orthodontic treatment would also cause further damage, since the biomechanical movement of actively resorbing incisor teeth would exacerbate the resorption.
To extract the canines themselves would undoubtedly arrest the resorption, but would leave the patient with incisor teeth with a short life expectancy. More importantly and despite their abnormal locations, the canines were the only uncompromised anterior teeth, with long and healthy roots and good crown anatomy.
Choosing 2 of the 4 incisors for extraction on the basis of their position or their prognoses is difficult, since they were all similarly compromised in the extent of the resorption. Furthermore, a fixed bonded appliance would be needed and it would be difficult to treat without including brackets on the two remaining compromised incisors. Extracting all four incisors would make temporary artificial replacement mandatory for much of the period of canine alignment, which would be difficult to achieve in the presence of artificial crowns. Post-treatment prosthodontic rehabilitation would be needed separately in the short to medium term and then definitively with implants at the age of 18-20 years.
Extracting the 4 incisors and the impacted canines would be a heavy price to pay, both psychologically and socially, for an 11 year old child. On the positive side, extraction and immediate replacement with a removable acrylic denture would offer the fastest and least complicated result in the short to medium term, notwithstanding its many shortcomings, inconveniencies and hardships for a young person. However, it should be remembered that deciduous molars were still present in the mouth and the premolars and second molars were unerupted.
Full orthodontic treatment, aimed at aligning the teeth, creating space, resolving the canine impaction, treating the class II relation of the molars, reduction of the overbite, re-aligning the dental midlines represented a long and complicated treatment for this child and is not without its risks even for a patient with non-resorbed teeth. Unnecessarily long, involved and sophisticated treatments would certainly increase the chances of further resorption and loss of the resorbed teeth.
Orthodontic treatment limited to resolving the canine impaction and providing incisor alignment, without treatment the class II relationship is to aim for a compromised outcome. Still not without its risks and doubts, even if successfully performed, this option was considered to provide her with the best outcome for the lowest iatrogenic shortcomings. This was the treatment approach adopted for this young girl. It was the method maintaining a maximum of the patient’s existing dentition for the short to medium term. It was nevertheless recognized that at some future date, hopefully lasting beyond the patient’s growth period, prosthodontic rehabilitation of the anterior teeth would be needed following the demise of one or more of the incisor teeth.
The approach to treatment
The patient’s parents were carefully apprised of the severity of the problem of the active resorptive process involving the child’s anterior teeth and informed that, with no treatment, she would lose them in a relatively short period. This was fully understood by the parents and, although they also signed a written statement to this effect prior to the commencement of the treatment they were nevertheless reminded of this at regular intervals during the treatment. 63._5

Fig. 5. Intraoral views of the teeth showing the initial orthodontic preparation immediately prior to surgical exposure of the canines. Note that the deciduous second molars and the deciduous right first premolar carry brackets as a precaution to reinforce the anchorage, if required. The blue elastic (separator) modules are a protection against chafing of the cheek mucosa in the initial stages.


Stage 1:
According to conclusions drawn from our earlier studies, this type of resorption is extremely aggressive and only arrests when the offending canine is distanced from the area. Accordingly, it was recommended there that the surgical exposure and traction of the canines be performed as a first and urgent priority, even before space had been provided in the dental arch to accommodate them.2, 3
In order to achieve this in this patient, molar bands with a soldered transpalatal arch, which were to act as the source of anchorage for the traction applied to the canines,were cemented into place. As a precaution against loss of anchorage, which would be displayed by mesial tipping of the molars, brackets were bonded to the deciduous second molars and the erupted right first premolar and sectional rectangular arches prepared in order to resist this movement, should they become necessary (Fig. 5).4 Brackets were not placed on the incisor teeth for as long as the resorptive potential of the canineswas rampant, which was for as long as they were in close proximity of the incisor roots.
Surgery was performed in January 2015 under general anesthetic cover by Prof.Nardy Casap-Caspi, Chair of the Department of Oral and Maxillofacial Surgery at the Hadassah School of Dental Medicine of the Hebrew University of Jerusalem.
The question as to whether an open or closed procedure should be performed was discussed between us. In general in these difficult circumstances, my preference is for a closed procedure,5-7 since a wide mucoperiosteal flap provides superior visibility, the bleeding area is at the periphery of the flap and it is easier to identify the follicle and the crown of the tooth. It is also easier to keep clear of the resorbing area of the truncated incisor roots, for fear of devitalizing them and to bond attachments to the crowns of the canines, as far as possible away as possible from this sensitive area, with excellent hemostasis. In the final instance, the surgical flap is fully closed over, to protect against the inadvertent collateral exposure of incisor roots. In the present case, however, the surgeon was concerned that with such extreme resorption, the mere opening of the soft tissue flap was likely to endanger the resorption front even before the canines were exposed and cause incisor devitalization. 63._6

Fig. 6a. An occlusal view of the palatal area showing the molar bands and soldered transpalatal arch. The bilateral bulges in the anterior palate indicate the location of the impacted canines (arrows).

Fig. 6b. Two individual open exposure procedures were performed in November 2014 (see text) and small eyelets bonded on the distal aspect of each of the canines. Light extrusive force was applied between the twisted steel ligature connector and soldered loops on the transpalatal arch. In this manner, the forces were drawing the canines away from the resorbing incisor roots.

Fig. 6c. In March 2015, the canines had erupted clear of the incisor roots. Note the location of the bonded eyelets. This was done to ensure that the traction would not cause unwanted rotation of the canines, during their movement in a purely horizontal and posterior direction.


Accordingly, an individual open exposure was performed on each of the two canines. Although canines may cause a very palpable bulge in the pre-surgery palate (Fig. 6a), the mucosa covering them is always very thick and when a circular piece of tissue is excised, the tooth lies in the depth of a narrow cylindrical opening which oozes blood continuously from its 360o cut inner surface, making attachment bonding highly unreliable. Nevertheless, with the surgeon providing and maintaining hemostasis and a moisture-free surgical field with the help of electrocautery and high-power suction, I was able to successfully bond the eyelets deliberately on the distal aspect of both, so the traction would not result in rotation of the teeth (Fig. 6b, c). Elastic thread was then tied from the eyelet attachments to the transpalatal soldered arch, providing immediate traction in a horizontal and posterior direction. In this way, the canines were distanced from the resorption front and free of any contact with the walls of the resorption craters in the incisor roots.
63._7

Fig. 7. Following the distancing of the canines from the immediate area, the destructive threat potential of the canines had been eliminated. This permitted the placement of orthodontic brackets on the resorbed incisors in March 2015, with the aims of intrusive alignment, proclination and the provision of space for future canine alignment.

63._8

Fig. 8a, b. A new panoramic and a new periapical film taken in September 2015 is shown during the alignment and space opening stage.


Stage 2.
Three months later, in April 2015, the canines had been drawn posteriorly in the palate and were erupted sufficiently to consider them no longer a danger for further root resorption. In accordance with the findings from our earlier work,2 therefore, I was now confident that it would be safe to begin to align the affected incisors and to create space for the eventual alignment of the canines.
Orthodontic brackets were placed on the incisors and the newly-erupted left first premolar and an initial ultra-light nickel-titanium archwire was tied into the brackets to achieve alignment and levelling (Fig. 7). This involved a considerable measure of intrusion of the incisors. Once alignment was achieved, a heavy (0.020 inch round) base arch was placed and open coil springs were ligated between first premolars and lateral incisors (Fig. 8) and the incisors were thus tipped labially and raised to reduce the excessive cover of the lower lip at rest. In this manner, the overjet was increased until there was excessive space in the canine area to accommodate these teeth.

63._9

Fig. 9a, b. Occlusal and anterior views of the dentition at completion of the alignment and space opening stage in December 2015. Note that traction on the canines was renewed from newly bonded eyelets on the mid-labial aspect of the crowns of the canines, to avoid unnecessary rotation during their movement towards the heavy (0.022inch round) labial base archwire.


Stage 3.
At this time, new eyelet attachments were substituted on the labial aspect of the canines, in place of those that had been bonded at the time of surgery (Fig. 9a). Elastic thread traction was applied directly to the labial archwire, which now consisted of a completely passive round 0.022” steel base arch. In this manner, the buccally-directed forces applied to the canines provided reciprocal anchorage for one another and the rigid archwire prevented unwanted lingual forces from being transferred to the incisors and premolars.  A mandibular fixed appliance was also placed at this juncture (Fig. 9b), with the sole aims of levelling the lower occlusal plane (curve of Spee) and achieving a degree of incisor proclination to assist in reducing the incisor overjet. With the canines brought quickly into their place in the arch, the eyelets were replaced by regular orthodontic brackets and the excessive space closed down, by retracting the incisors and reducing the overjet to more acceptable proportions.63._10

Fig 10. Intraoral views of the dentition at the completion of the orthodontic treatment, 10 day after the appliances were debonded in early January 2017 (2 weeks before publication of this bulletin). Only absolutely essential treatment was performed in this highly compromised case and no attempt had been made to treat the class II relation of the left hand side.


At this stage, a re-evalulation of the situation was undertaken. It was noted that good alignment and root orientation had been achieved, although torque values of the treated canines were inadequate (Fig. 10). The radiographs showed little-to-no change in root length of the incisors, although there appeared to be an improved level of bone support for them, following the elimination of the destructive influence of the canines once they had been distanced from the area (Fig. 11a, b). 63._1163._11b

Fig. 11a, b. The post-treatment panoramic and periapical views taken on the day appliances were removed, in January 2017, show a minor degree of resorption of the roots of the maxillary posterior teeth. The reader is invited to compare the root lengths of the maxillary incisor teeth at this stage vis-à-vis their pre-treatment length In March 2014 (Fig. 3).


It was decided that more damage would be done by using the affected incisors as anchorage in the attempt to labially root torque the canines than to leave the canines in their present positions. Thus, treatment was declared completed and the appliances were removed. Debonding brackets from teeth with such compromised support is not a procedure to be undertaken with relish. It required the greatest care to avoid excessive forces on these weakened teeth. Although mobility was still present, it had noticeably lessened when compared to their condition at the initiation of treatment, 24 months earlier.
In line with the restricted aims of treatment noted above, no attempt was made to address the class II relationship, although there was an unplanned improvement of the midline alignment. A bonded lingual 3-to-3 twistflex steel retainer was prepared on a plaster cast and bonded on the maxillary incisors the same day, together with a simple removable Hawley retainer in the mandibular arch, in late December 2016.
In retrospect
The patient is now 13 years of age and it is with some justified optimism that we may be permitted to hope that the incisors will be maintained at least until she reaches an age where implant prosthodontics can be reasonably considered. Indeed, as we have reported in an published study that we authored and which was granted the BF & Helen E. Dewel Clinical Research Award of the AJODO1 for 2016, and elsewhere, our experience shows that these teeth are often maintained well past this time and into the patient’s 3rd and even 4th decades, provided the canines are effectively and rapidly distanced from the immediate area.2 The case will be followed over the next few years and further lessening of mobility is expected, due to increased bone support and as bone maturation occurs and bony trabeculation is re-established, in the months following the cessation of orthodontic tooth movement.
The occlusion is far from ideal, particularly on the left side, where the molars are in a full class II interdigitation and the premolars and canine are cusp-to-cusp. Nevertheless, by comparison with the alternative approaches listed above, this has been the least aggressive, most conservative and most satisfying of all the available options. Many of us might feel embarrassment to show this case to colleagues who routinely produce ideal alignment and occlusal outcomes. But, if we are to relate to orthodontics primarily as a health profession, there can be no excuse for denying treatment to a child suffering from a potentially mutilated dentition of this enormity, simply because we cannot achieve an ideal board examination outcome.
It is emphasized in relation to this and similar cases, that success can only be achieved if
1.    the orthodontist is meticulous in the accurate positional diagnosis of the impacted tooth in relation to surrounding structures,
2.    the case is treatment planned and it is determined that resolving the canine impaction and saving the resorbed teeth are in the best interests of the patient  – i.e. that the case would be best served with a non-extraction procedure,
3.    the direction that traction must take is determined
4.    an appropriate simple mechanism for applying directional traction is designed and prepared
5.    no brackets are placed and no forces applied to teeth that are undergoing active resorption, until the cause (the impacted adjacent tooth) has been removed.
6.    the impacted canine is exposed even before space has been provided for it in the dental arch
7.    immediate extrusive force is applied preferably at the surgical scene by the orthodontist who should ideally be present
8.    the orthodontist limits treatment by only undertaking orthodontic tasks that are essential, avoiding requirements of lesser importance unless and until simple periapical radiographic follow-up of the teeth in the affected area is made.



References
1.    Chaushu S, Kaczor-Urbanowicz K, Zadurska M, Becker A. Predisposing factors for severe incisor root resorption associated with impacted maxillary canines. American Journal of Orthodontics and Dentofacial Orthopedics, 2015;147:52-60
2.    Becker A, Chaushu S.  Long-term follow-up of severely resorbed maxillary incisors following resolution of etiologically-associated canine impaction. American Journal of Orthodontics and Dentofacial Orthopedics 2005, 127: 650-654
3.    Becker A, Chaushu S.Impacted teeth and the 6 incarnations of resorption.(Les six formes de résorption associées à l’inclusion dentaire)L’OrthodontieFrancaise 2015, 86:277–286
4.    Becker A, Chaushu G, Chaushu A. An analysis of failure in the treatment of impacted maxillary canines. American Journal of Orthodontics & Dentofacial Orthopedics 2010;137:743-54
5.    Becker A, Chaushu S. Palatally impacted canines: The case for closed surgical exposure and immediate orthodontic traction. American Journal of Orthodontics and Dentofacial Orthopedics 2013;143:451-459
6.    Becker A. The orthodontic treatment of impacted teeth. 3rd edition, 2012. Oxford: Wiley-Blackwell Publishers. 2012. ISBN-13:978-1-4443-3675-7, ISBN-10:1-4443-3675-4
7.    Becker A, Caspi N, Chaushu S. Conventional Wisdom and the surgical exposure of impacted teeth. Orthodontics & Craniofacial Research, 2009; 12:82-93
8.    Becker A. Extreme tooth impaction and its resolution. Seminars in Orthodontics, 2010, 16:222-233