Unerupted teeth cannibalizing their neighbors: part 2

Published: April 2016

Bulletin #54 April 2016

Unerupted teeth cannibalizing their neighbors: part 2

In part 1 of the article, which appeared as the March 2016 bulletin #53 on this website, I discussed the resorptive process that affects the roots of teeth adjacent to and initiated by an impacted tooth, particularly a maxillary canine which had “lost its sense of direction” while still exercising eruptive potential. Since the canine is the most frequently seen example of this phenomenon, the present discussion will largely relate to it, although the principles are the same for other teeth. In the conclusion to the March 2016 bulletin I noted that, when the resorption has penetrated into the pulp, a merging of the resorptive soft tissue of the periodontium and the pulp occurs which is entirely free of bacteria, free of surgical trauma and, in consequence, free of inflammation. The dental pulp is healthy, vital and symptomless and the natural color of the tooth is unchanged ………….. and, because there is no pathology, no treatment is indicated, i.e. neither root canal treatment, nor surgical apicoectomy, nor extraction! It was also pointed out that, once the aberrant canine is distanced from the immediate area, the resorption abruptly ceases, as we have demonstrated in clinical research carried out in Jerusalem.1

Obviously, then, this phenomenon should be the first and most urgent priority to be addressed in the orthodontic treatment with the aim of preserving as much of the root of the tooth as possible. It should precede all other goals of the orthodontic treatment, including relegating the essential orthodontic opening of space in the arch for the canine to second place.

We now pick up the narrative again, after the danger of losing the resorbed tooth and the impacted tooth has largely receded and move on to the more routine part of the orthodontic treatment, i.e. to align the other teeth in both jaws and to achieve good occlusal relations, with appropriate follow-up. Aside from the observations and conclusions referred to in last month’s bulletin, several new questions arise that need to be addressed.


Fig. 1a. Anterior section of the maxilla depicted on a panoramic film showing 2 unerupted permanent canines. The left canine is associated with marked resorption of the root of both the central and lateral incisors.

Fig. 1b. A cross-sectional frame from the CBCT to show the severity of the oblique labial resorption of the root of the lateral incisor.

Question 1: How can a surgeon expose the impacted tooth, without devitalizing the adjacent tooth?

As with any impacted tooth, the use of radiographic imaging for accurate positional diagnosis and for searching the immediate area for additional pathology is of extreme importance before embarking on treatment of this anomaly (Fig. 1a, b). In the present context, a cone beam CT should be considered mandatory. It is logical that a labial canine needs to be exposed from the labial side and orthodontic traction similarly directed, while a palatal canine needs to be exposed and traction applied from the palatal aspect. However, there are a good number of impacted canines that are located within a progressively enlarging apical resorption crater of the incisor root. The lip of this crater may be higher on one side than on the other and this may determine which way the tooth should best be directed to resolve the impaction.


Fig. 1c, d. Together with extraction of the first premolar tooth, a full labial flap has been raised from the attached gingiva at the necks of the incisors. Only the incisal part of the crown of the canine is exposed for bonding of the eyelet attachment and the lingual aspect of the tooth, adjacent to the resorbed root of the incisor, remains untouched.

Having determined on which side to perform the exposure, my recommendation for the surgery in these difficult cases is to raise a broad, full-thickness flap from the attached gingiva around the necks of the teeth and to extend it superiorly by blunt dissection, to reveal the underlying bone. The impacted canine is beneath the surface that is exposed by the surgeon. It comprises a very thin shell of bone which bulges the flat surface of the bony profile and is often not visible radiographically. Using the various radiographic and CT images as guides, the exact location of the crown of the tooth and of the resorption front must be accurately determined on the exposed bony surface. The thin bony cover is then perforated over the crown of the tooth, as far away from the resorption front as possible to expose the dental follicle. An opening in the follicle is made which requires to be widened enough to expose a minimum of enamel surface, enough for the orthodontist to bone a small eyelet attachment (Fig. 1c, d). Because the surgeon is on hand to maintain control of bleeding, using a fine canula attached to the suction system, this entire surgical procedure may be accomplished with remarkably little surgical trauma.


Fig. 2a. An auxiliary labial archwire is ligated into the brackets “piggy-back style” over a heavy main arch with the loop in its horizontal passive mode, prior to the surgery. A full soft tissue flap has been raised from the attached gingiva of the deciduous canine and permanent incisors adjacent to the impacted right canine, which is located high above the resorbed root of the central incisor.

Fig. 2b. The twisted steel ligature from the bonded eyelet attachment is threaded through the terminal helix of the auxiliary archwire.

Fig. 2c. The loop of the auxiliary archwire is turned upward under light finger pressure and secured by turning over the twisted ligature to hold it against the re-sutured flap in its active mode. A small ball of composite material is cured over the helix and ligature to present a smooth and comfortable extremity to avoid ulceration of the oral mucosa.

The full flap must be sutured back to its former place to re-cover the tooth and the newly bonded eyelet. The twisted steel ligature that was tied into the eyelet of the attachment is taken through a pierced needle hole or slit in the middle of the sutured flap, opposite the location of the tooth beneath. In this way, the orthodontist will have the opportunity to apply traction to the tooth immediately, by tying a custom-made spring or elastic thread to the ligature. The initial activation is done before the patient is discharged from the operatory and while the area is still anesthetized, both for a labial canine (Fig. 2a-c) and for a palatal canine (Fig. 3a-f). BBB._Fig._3a_c

Fig. 3a. A full palatal flap is reflected from the gingival margins of the adjacent teeth to reveal the palatal side of the canine, which is very close to the root of the lateral incisor. Note the presence of an auxiliary archwire with a vertical loop in its passive mode, overlying the rectangular base archwire, having been placed immediately prior to the surgery.

Fig. 3b. An eyelet attachment is place on the palatal side.

Fig. 3c. The full flap is re-sutured back to its former place, with the twisted connector ligature exiting through the palatal mucosa.


Fig. 3d. The vertical loop of the auxiliary archwire is pushed palatally and upwards to be ensnared into its active horizontal mode in the shortened connector, which is turned into a hook. The active force is vertically directed.

Fig. 3e, f. Two months later, the canine has erupted away from the lateral incisor and a new eyelet is substituted on the anatomically labial aspect of the canine for direct elastic traction to the archwire.

It should be abundantly clear that an open surgical procedure should be avoided, since the crown of the impacted tooth cannot be exposed adequately without also exposing the root of its neighbor, if one is to ensure that it will not close over within a few days post-operatively. When the impacted tooth is located directly in the actively resorbing apical section, any open procedure is likely to cause a loss of vitality of the resorbed tooth.

Question 2: After the canine has been distanced and the resorption has stopped, is moving the affected tooth a viable option or will this re-kindle the resorption process?

The etiology of this form of resorption is concerned with the proximity of the impacted tooth and its potential for eruptive movement. Following the distancing of the impacted tooth, therefore, there is no reason to suspect further resorption from this cause. Nevertheless, resorption occurs from other causes during orthodontic movement of a tooth, particularly the arguably predictable orthodontically induced inflammatory root resorption (OIIRR),2. but also others.3 However, these are generally insignificant and, if the further movement of the tooth is kept to an acceptable minimum, there is no reason to suspect further danger to the tooth.

In part 1 of this article, I asked how the oral surgeon, the periodontist, the endodontist and the pediatric dentist would view the above scenario and whether they might advise treatment for the problem created by this variety of root resorption. Now let’s ask what the orthodontist would or should do?

Question 3: Should the orthodontist “dare” to move the tooth or should he/she be frightened of being sued if, perchance, the tooth were to be further compromised and possibly lost during the treatment?

In these cases, the parent must be brought into the discussion and informed of the problem together with the options for treatment. The parent should be advised, at the outset, that there is a danger that the tooth may be lost and the decision to nevertheless attempt orthodontic resolution should be made together with the parent. A signed statement to that effect should be elicited from the parent.

During the period of active root resorption, the immediate area of alveolar bone is rarified and this appears on a radiograph as a dark radiolucency. The tooth itself exhibits a marked degree of mobility, depending on how much of the root has been lost. While the impacted tooth is being moved away from the immediate area, the resorbed tooth must be treated with great care. It should not be used as a supportive element for the orthodontic appliance or a counter balance to forces exerted elsewhere. With certain exceptions, the tooth should not carry a bracket or be tied into the orthodontic scheme until much later.

In the weeks and months that follow, the resorbed tooth becomes much firmer and this is related to the deposition of new bone in the apical area which can be easily seen on a routine periapical film. However, given the reduced root length, correspondingly reduced forces should be used in order to keep the force per unit of root surface to a physiologic level. Towards the end of the overall orthodontic treatment, the resorbed tooth can be included into the general appliance scheme and reasonable orthodontic forces applied to move it into the desired position, including root uprighting and torqueing vectors. Optimal rather than ideal finishing procedures should be the rule.

BBB. Fig. 4a_1

Fig. 4a. This is the completed result of the case illustrated in Fig. 1a-d. The quality of the periodontium on the treated (left) side and its appearance compare favorably with those of the normally erupted canine of the opposite side.


Fig. 4b. Periapical views of the anterior teeth shows the shortening of the root of the left central incisor. The severe oblique resorption of the entire labial side of the root of the lateral incisor is represented on this film as thin, indistinct and radiolucent, but almost full length.

Question 4: At the completion of treatment, will it be possible to achieve a result in which the appearance can be made indistinguishable from the teeth on the other side and where periodontic parameters are in the range of normal?

Since the resorbed incisor will be of normal shape and color, the likelihood of achieving a good appearance are very good. If the impacted tooth has been erupted through attached gingiva, its periodontic parameters will be close to ideal (Fig. 4a).

BBB._Fig._5a BBB._Fig._5b

Fig. 5a. A right labial canine has been drawn through the oral mucosa, high in the vestibulum.

Fig. 5b. Reparative periodontal surgery was not performed and the result shows the long clinical crown of the canine invested with labial oral mucosa. The unaffected canine of the unaffected left side is invested with mildly inflamed but attached gingiva.

On the other hand, if a labially impacted tooth has been erupted through the oral mucosa, without any modifying surgical procedure being undertaken to obviate it (Fig. 5a), the periodontal tissue that invests the labial side of the tooth in the final instance will be very thin, mobile and red and the clinical crown will be elongated in comparison with an opposite unaffected side (Fig. 5b). The non-keratinized mucosal tissue will ulcerate easily in function and during simple oral hygiene procedures.

Question 5: At the completion of treatment, will it be possible to achieve a result in which the prognosis of the affected tooth is equivalent to that of the unaffected tooth on the other side, or at least, that it may last long enough to pose as a medium term stop-gap until the child’s general growth has ceased and an artificial implant-borne replacement can be advised?


Fig. 6a. A case with severe root resorption of both maxillary lateral incisors due to impaction of the canines, seen here in May 1999.


Fig. 6b. The same case on the day appliances were removed, in June 2002. There is a good height of alveolar crestal bone, which provides no more than a millimeter or two of support for the severely resorbed lateral incisors.


Fig. 6c. The same case at follow-up 5.6 years later, in December 2007, with a twistflex bonded retainer in place. Note the vertical increase in bony support, consolidation of bone and good trabecular pattern around the stunted root ends.

Unless the remaining portion of the root of the tooth is very short indeed, the prognosis of the tooth will be good and may last for many years, possibly as long as many of the other neighboring teeth1. In the event that the root of the tooth is very truncated, with no more than a millimeter or two of alveolar bone support, splinting the tooth with a lingual bonded twistflex type of retainer will eliminate mobility and usually permit the retention of the tooth into adulthood (Fig. 6a-c).


Fig. 7a. The left lateral incisor has lost almost its entire root to resorption.


Fig. 7b. The clinical intra-oral view of the anterior dentition shows the shallow concavity in the profile of the alveolar process of the atrophic edentulous area corresponding to the area where resorption of the root has occurred (arrow).

Question 6: Will the form of the alveolar ridge in the immediate area be normal?

New alveolar bone accompanies the eruption of teeth, whether following natural or mechanically-encouraged eruption. Thus, from this standpoint the bone height will undoubtedly be increased to the level of the interproximal bone linking the adjacent teeth. However, within a short time after completion of treatment, the surface profile of the area above the tooth will often feature a shallow concavity (Fig. 7a, b), corresponding to the area where one would normally expect to see the outline of the missing incisor root. So, the vertical height of the alveolus is normal and its width in the area of the cervical margin of the tooth will be similarly normal. However, in the area corresponding to the loss of root, it will become bucco-lingually very narrow, since this will have effectively turned into an atrophic edentulous area.


1. 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

2. Brezniak N, Wasserstein A. Orthodontically induced inflammatory root resorption. Part I: The basic science aspects. Angle Orthodontist 2002;72:175-9.

3. Becker A, Chaushu S. Les six formes de résorption associées à l’inclusion dentaire (Impacted teeth and the 6 incarnations of resorption). L’Orthodontie Francaise,2015;86:277–286.