Root Resorption of Central Incisor by Impacted Canine in Unusual Transposition: Orthodontics and Implant Rehabilitation: 3-Year Follow-Up

This case presents an unusual transposition of an impacted canine on the central incisor that provides a multidisciplinary approach to its resolution. The patient comes to the consultation for mobility of the central incisor. Clinically, tooth mobility was confirmed with tooth crowding and persistence of the temporary canine. Cone beam tomography (CBCT) observed the atypical position of the permanent canine that caused root resorption of the ipsilateral central incisor and the need to extract both teeth. The conservative treatment of the bone structures during the dental enucleation of the impacted canine carried out by odontosection and the immediate bone grafting of the defect projected an acceptable regeneration of the bone volume for the insertion of the implant. The orthodontic treatment managed to correct the bite, position the upper premolar in the place of the canine tooth and maintain the space to place the implant in the central incisor. The three-year fol-low-up shows maintenance of the peri-implant crestal bone level, the success of orthodontic treatment with recovery of the patient’s function and aesthet-ics.


Introduction
The case presented is unique because it presents an impacted canine in the un- Becker and Chaushu found that dental transpositions have a relatively low prevalence in the population, approximately 0.1% to 0.4% in both jaws. They are generally unilateral, more frequent in the upper arch between 70% and 80% and between canines and premolars. Furthermore, they state that when an impacted permanent maxillary canine is diagnosed and a malocclusion exists, a full orthodontic evaluation is needed for overall planning. The orthodontist will perform a clinical examination. When all the information is gathered, a treatment plan will be formulated to resolve the general malocclusion, which may lead to the decision to extract the permanent teeth [3].
It is quite clear that the greatest risk is the possibility of root resorption in the adjacent teeth. Studies using Cone Beam computed tomography (CBCT) indicate that the percentage of root resorption in lateral incisors caused by impacted canines ranges from 38% for Ericson and Kurol [4] to 66.7% reported by Walker et al. [5].
Grisar et al. advise that treatment planning for the impacted maxillary canine should be based on 3D images. With CBCT, it is possible to correctly define the position of the impacted maxillary canine and recognize accompanying anomalies such as ankylosis, root dilaceration with or without anchoring to the floor of the sinus or nasal cavity, resorption of neighboring teeth or odontoma [6].
Becker et al. studied the influence of age on impacted teeth, claiming that they are more difficult to treat in adults, the success rate among patients older than 30 years was 41%, while the success rate for those of 20 at 30 years was 100% [7].
The unusual transposition of the impacted canine leads to the loss of two fundamental teeth for the esthetics and function of the stomatognathic system. The objective of our interdisciplinary approach work is to present a predictable treatment plan to rehabilitate normal dental anatomy, position and occlusion through synchronous orthodontic and implantology treatment.

Clinical Findings
The patient has a mesofacial biotype, with a straight profile. Transversally both jaws of her present compression, causing a cross bite from canine to second molar on the left side. The midlines do not match and the highlight and criss-cross above are minimal. On the right side she presents molar and canine class I and molar and canine class III on the left side ( Figure 1).

Diagnostic Evaluation
The first diagnostic imaging method is panoramic radiography or orthopantomography ( Figure 2  Using the models of the jaws mounted on the articulator, frontal and profile photographs, the orthodontic treatment plan was initiated using the lateral cranial X-ray of the patient to perform the cephalometric study and determine the treatment plan ( Figure 3(a), Figure 3(b)).

Therapeutic Intervention
The equations In the planning of the treatment (interdisciplinary) and prior to orthodontic treatment, in the initial stage it was decided to perform the simultaneous enucleation of the two impacted canine teeth and central incisor with root resorption mobility and poor prognosis. Digital radiovisiography (RVG) with a Kodak 5100 radiovisiograph was used to control the sequence of the surgical procedure (Figure 4).
After infiltrative anesthesia with 4% articaine, a simple extraction of the incisor was performed and a mucoperiosteal flap was detached in the anterior area of the palate. Using the post-extraction socket as access, the dental canine crown was sectioned (Figure 4(b)). The root portion was dislocated and extracted with a straight elevator, and the cavity toilet was completed with a molt curette ( Figure 4(c)). The bone defect was filled (Figure 4(d)) with a synthetic bone graft from Argentinean beta tricalcium phosphate ceramic developed by Garces Villalá et al. [8].

Orthodontic Treatment
In    were placed, to which tooth 21 was placed to maintain the space until the implant was placed ( Figure 5(c)).

Implantological Treatment
After the bone graft had healed (Figure 6(a) and Figure 7(a)), the insertion surgery of the hexagonal internal connection dental implant was performed ( Figure 6(b) and Figure 6(c)). The access was made with an incision towards the palatine (Figure 7(b)) and an upper labial frenectomy was also performed (Figure 7(c)) to prevent gingival recession on the future dental crown of the implant. After four months of hard and soft tissue healing (Figure 7(d)), a gingival healing abutment (Figure 7(e)) is connected, allowing soft tissue stability after four weeks (Figure 7(f)). At this time, the impression is taken with regular silicone, a transfer is used and its adjustment is controlled radiographically ( Figure   6(d)). On plaster models, a metal casting is made, its fit ( Figure 6(e)) and dental occlusion (Figure 7(g)) are checked, which will support the ceramic of the finished prosthesis (Figure 6(f) and Figure 7(h)).

Monitoring and Results
The

Discussion
In the present case, a possibility of comprehensive multidisciplinary treatment of an unusual dental transposition is presented, respecting biological and biomechanical criteria. Miranda Candeiro et al. affirm that dental transpositions are more frequent in the female sex and the left side is generally the most affected [9], which is consistent with the present case. The limitations observed in our work were the lack of regular follow-up (quarterly controls were avoided due to the COVID 19 pandemic), in addition, the unforeseen event of foreign body infection (seed) which modified the initially available bone volume.
Mithridade et al. suggest treatment alternatives other than the one proposed, such as the placement of implants through impacted teeth to avoid invasive surgery [10], however its routine application is not justified due to the lack of patients with long-term follow-up. Another possible treatment approach chosen by Cruz consists of orthodontic traction of the impacted canine and its repositioning [11] but in our case, it would have a poor prognosis because the impaction is very deep with marked angulation and the root of the canine is fully formed.  central incisor is very unfavorable and its orthodontic displacement could damage other teeth [12]. For this reason, we consider that our treatment plan, although it performs the dental extraction of the impacted canine which could be tractioned by orthodontics, preserves the integrity of the neighboring teeth. Yan et al. [13] published that maxillary canine impaction increases the risk of root resorption at adjacent teeth (incisors and first premolars). Physical proximity (\1 mm) between the impacted canine and an adjacent root is the most important predictor for root resorption. This situation was verified in our case, on the upper central incisor with a poor prognosis due to root resorption that had to be extracted (regardless of the chosen treatment plan) and rehabilitated by means of a dental implant.

Conclusion
The However, a longer follow-up period is needed to validate its routine application.

Patient Perspective
The patient favorably evaluated the treatment and highlighted the emotional support provided by the professional team, especially during the COVID-19 pandemic.

Informed Consent
The patient accepted the proposed treatment and signed the corresponding informed consent.