Multidisciplinary management of a fused maxillary incisor: Case report with 5‐year follow‐up

Abstract Detailed treatment planning and execution are crucial if regenerative approaches are to be attempted to retain fused permanent teeth. Long‐term follow‐up is necessary to monitor the stability of the final outcome, both esthetically and functionally.


| INTRODUCTION
year-old male presented to the dental clinic with a supernumerary tooth fused to a maxillary central incisor. Treatment included an interdisciplinary regenerative approach with 5-year follow-up. Fusion cases require meticulous diagnosis and treatment planning with the main objective of retaining the tooth and obtaining a satisfactory outcome.
"Twinning anomalies" are abnormalities of tooth shape. They include gemination, concrescence, megadontia, macrodontia, and fusion. Gemination occurs when two teeth develop from one tooth germ, resulting in a large tooth, and the number of teeth is normal. Usually, the division is incomplete and the tooth presents a single root and canal. 1 On the other hand, fusion arises by the union of two normally separated tooth germs that can be either complete or incomplete. In the case of union of two permanent teeth, the patient presents with one large tooth and an incomplete dentition. When fusion is between tooth germs of a normal tooth and a supernumerary tooth, the number of teeth is complete and it becomes more challenging to differentiate fusion from gemination. As the term "double-tooth" was introduced, 1 it presented various management challenges for the clinician particularly if they include anterior teeth. The most common problem is esthetics, not only because of their abnormal shape and size, but also because of subsequent orthodontic problems especially crowding. Caries and periodontal complications may also be at play when optimal plaque control is hindered by a subgingival fissure or union lines. 2,3 Different approaches have been proposed to deal with cases of "double teeth" ranging from surgical separation followed by esthetic recontouring only, 4 or accompanied with endodontic treatment followed by orthodontic treatment as well. 3,5 A recent systematic review of 72 cases 6 showed that most of these cases required interdisciplinary management. Half of the cases were subjected to restorative treatment following surgical hemisectioning that did not always include removal of the sectioned fragment. Most of these cases required orthodontic management to achieve a satisfactory esthetic outcome. Several cases were subjected to extraction followed by prosthetic options, while some cases were left untreated.
Interestingly, even with multidisciplinary management, the approach in each discipline may vary tremendously from cases treated conservatively using vital pulp therapy procedures to cases requiring complete pulpectomies and root canal treatment. 5,7,8 Regarding the surgical approach following hemisectioning, the option to use grafting materials and membranes has not always been pursued although several reports have recommended their use to minimize bone loss, hence better periodontal outcome. 2,9 The current case report of a young male documents an unconventional multidisciplinary approach to the management of a double maxillary anterior fusion requiring orthodontic treatment. The CARE guidelines were implemented in reporting of this case (www.care-statement.org). 10

| Patient Information
A twelve-year-old male patient presented to the Conservative Dentistry Department outpatient clinic, Faculty of Dentistry, Alexandria University in October 2013, complaining of poor esthetics. The patient was systemically healthy. He had malocclusion that was classified as Class II division 1 and requiring orthodontic treatment. Macrodontia of the maxillary central incisors was evident. Previous dental history included extractions of primary teeth and failed orthodontic treatment.

| Clinical findings
Upon oral examination, it appeared that the crown of the left maxillary central incisor was fused to a mal-aligned supernumerary tooth (mesiodens) which was situated between the two central incisors ( Figure 1A). The teeth were endodontically and periodontally healthy and the patient had fair oral hygiene.

| Diagnostic assessment
Digital periapical radiographs revealed that the two teeth were fused from the crown to the end of the root ( Figure 1B). Cone beam computed tomography scans (CBCT) evaluation revealed the two teeth were completely fused with a common root canal system in the coronal to mid-third then followed by two separate canals. At one level palatally, the teeth appeared to have a common root canal system in the apical 12 mm ( Figure 1C-G). In order to pursue orthodontic treatment of the case, a decision was made to retain the maxillary left central incisor following hemisectioning of the fused tooth along with bone graft placement in the resultant socket. The CBCT was valuable in evaluating the clinical condition as well as estimating the amount of required bone substitute ( Figure 1C-I). The treatment plan was discussed with the patient's guardian and as such provided informed written consent according to the requirements of the intuitional review board of the Faculty of Dentistry, Alexandria University (IRB NO: 00 010 556 -IORG: 0 008 839) (https:// ohrp.cit.nih.gov/searc h/search.aspx).

| Endodontic therapy
Under local anesthesia (2% Mepivacaine, 1:20 000 epinephrine), access cavities were prepared for the fused teeth showing pulpal communication between the teeth (Figure 2A-B). Working lengths were estimated and the canals were instrumented using the step-back technique till size 60 hand files along with copious irrigation with 2.5% Sodium Hypochlorite (NaOCl) ( Figure 2C-D). Finally, Ethylenediaminetetraacetic acid (EDTA) (Glyde, Dentsply) was placed for 1 minute to remove the smear layer followed by irrigation with saline. The canal was completely dried using sterile paper points. A thick slurry mix of Pro-root white Mineral Trioxide Aggregate (MTA) (Dentsply Sirona) was packed using an amalgam carrier and Schilder pluggers. The supernumerary (mesiodens) was irrigated, dried, and filled with Calcium Hydroxide Ultracal XS (Ultradent). The access cavity for the central incisor was then restored with composite (Ivoclar, Vivadent) ( Figure 2E-F).

| Surgical procedure
Two months later, the patient was recalled for surgery. The day prior to surgery the patient had orthodontic brackets and bands cemented ( Figure 3A-C). At time of surgery, the patient's face was disinfected , the mouth was rinsed with chlorhexidine HCL (Hexitol, Arab Drug Company ), and the teeth were polished under local and regional anesthesia (infiltration + incisive and infraorbital nerve blocks with Mepicaine-L (Mepivacaine HCL 2% + levonordefrin 1:20 000, Alex Co. For Pharmaceuticals), sulcular incisions were made mesial, labial, and palatal using micro-surgical blades (Braun Melsungen AG, Aesculap division, Tuttlingen).
A mucoperiosteal flap was reflected just to expose the crestal bone. Using a round end tapered coarse diamond stone (Jota AG, Ruthi, Switzerland) on a high-speed handpiece with copious cooling, an initial guiding groove was created through the distal 1/3 of the mesiodens to avoid injury to the permanent incisor. Then, the crown was sectioned along that groove till the cervical line ( Figure 3D). Periotomes (Kohdent Roland Kohler Medizintechnik GmbH & Co. KG) were then used to dissect the periodontal ligament attachment. A perioperative digital periapical radiograph was taken to confirm proper orientation of the cuts before proceeding. Sectioning took place using a cross-cut tapered carbide extra-long surgical fissure bur on a bur extender (Jota, AG) mounted on a low speed handpiece at 30 000 RPM and 1:1 torque (Nouvag AG, Goldach) with copious saline irrigation. After gentle luxation, the sectioned part was grasped and removed using artery forceps. The sectioned surface was smoothened and lightly planed with curettes ( Figure 3E-G). The socket was rinsed with sterile saline, and hemostasis was accomplished using sterile gauze in preparation for placement of Emdogain ® (Institute Straumann AG Postfach, Basel Switzerland). Pref Gel ™ ( Institute Straumann AG Postfach, Basel Switzerland ) was then injected according to the manufacturer's instructions onto the sectioned and planed surface after which it was rinsed with sterile saline. Emdogain ® was also injected in the socket itself and mixed with the synthetic bone graft (70S/30C Bioglass, 11  Alphintern (Amoun Pharmaceutical Company) as well as antibiotics, Dalacin C 300 mg (Pfizer, Canada) twice daily for five days. At the 4-month follow-up, the examination following healing and tissue contraction revealed a high frenal attachment in relation to both central incisors and a decision to perform a frenectomy was taken ( Figure 4).

| Orthodontic intervention
The patient was referred for orthodontic evaluation after surgical-endodontic interventions. The decision to follow-up for one year prior to orthodontic treatment to correct maxillary prognathism was taken to allow for the evaluation of the success of surgical intervention. One year later and for a period of 24 months, the following orthodontic protocol was adapted. Bilateral upper first premolars were extracted followed by full upper and lower arches bonded edge-wise appliances with

| Follow-up until four years
The patient was regularly recalled up to 4 years post-surgical intervention to ensure the absence of complications and general satisfaction with the ongoing treatment. Surgical re-intervention was planned in the event of development of any complications. Following endodontic treatment, the patient reported mild sensitivity to cold which quickly resolved within two weeks post-surgically and the tooth remained asymptomatic. Following surgical intervention, healing was complication-free. CBCT at one-year follow-up revealed the apex of the supernumerary tooth had been retained ( Figure 5). Clinical examination revealed presence of a sinus tract draining pus which was traced to the central incisor and was communicating with a deep pocket on the mesial surface of the central incisor. A decision was made to perform conservative treatment via periodontal scaling and curettage to avoid disturbing the tooth movement during active orthodontic treatment. The patient was recalled for bimonthly periodontal examination (Table 1) and remained asymptomatic and stable up to 4 years in spite of persistence of a deep periodontal pocket ( Figure 5). The tooth showed no mobility yet some discoloration was the only complaint by the patient. After 4 years, CBCT and periapical radiographs showed the presence of a thin labial plate of bone although a periapical lesion had developed surrounding the left maxillary central incisor and adjoined apex of supernumerary ( Figure 6).

| Re-intervention surgery
A decision to re-intervene surgically was made and initiated following termination of the orthodontic retention stage (Figure 7). This was done by reflecting a full thickness flap which exposed a long vertical narrow osseous defect on the mesial surface of the maxillary left central incisor . Periodontal debridement of the granulation tissue and root planing was done. The retained apex was removed and root end resection of the maxillary left central incisor was also done. Plateletrich fibrin (PRF) membranes were prepared from 20 cc of the patient's venous blood without anticoagulant. The blood was centrifuged at 3000 rpm for 10 minutes to produce 3 PRF clots which were then squeezed to obtain compact membranes. One PRF membrane was then adapted along the planed root surface and another membrane was placed underneath the flap immediately prior to its repositioning. The patient was followed up for another year and revealed markedly reduced periodontal probing and attachment loss readings (Table 1) with very good gingival contour. Periapical radiographs revealed periapical bone healing; however, mesial crestal bone height did not improve at the time of last follow-up. Regarding the orthodontic treatment, skeletal changes can be summarized as follows. In the antero-posterior plane, the discrepancy between maxilla and mandible was reduced due to retruding of the maxilla and protruding of the mandible (as evidenced by: SNA-SNB -ANB -Wits appraisal) ( Table 2). In the vertical plane, increasing of the facial height occurred (as evidenced by: Fr/MP -SN/MP -Pal/MP). Regarding the dental changes, reduction of overjet occurred mainly by retrusion of the maxillary incisors (as evidenced by: 1 Fr -1 Md) (Figure 8). After one year of de-bonding and retention using the Hawley appliance, the patient showed stable occlusion and no morbid changes in the surgery area. At 4-year CBDCT follow-up, no signs of root resorption or blunting could be detected. However, 1 year of follow-up after the second surgery revealed some relapse as evidenced by increased spacing between the maxillary central incisors. Clinical documentation of case progression is shown in Figure 8.

CONCLUSIONS
The current case presented with a complete dentition and an abnormally large central incisor. This may be due to the fusion between a permanent central incisor and a supernumerary mesiodens. The term "double-tooth" therefore seems more applicable in such a case. The main problems encountered in the management of double teeth are the lack of sufficient information reporting the best line of treatment and the relative absence of long-term follow-up of these interventions. 3 Consensus indicates that a multidisciplinary approach is the best choice for dealing with these cases. Therefore, a combined endodontic, periodontal, and orthodontic intervention was applied. The management strategy determined was dependent on clinical and radiographic findings and anticipated topography following hemisectioning of the twinned tooth. The current case reports a five-year follow-up period.
The main observations were that this protocol resulted in improved function, maintenance of alveolar bone height as well as patient and parent satisfaction with the treatment. Orthodontic results were stable and resulted in a normal occlusion and a drastic improvement in esthetics. There was no root resorption and barely any mobility after the end of therapy. Endodontic therapy using a mineral trioxide aggregate (MTA) monoblock was selected since MTA represents a highly biocompatible material that has excellent sealing properties, in addition to exceptional antibacterial and bioinductive abilities. 12 MTA monoblock filling has been suggested for filling of immature necrotic teeth with open apices and has been shown not only to strengthen the roots but that upon its removal for post space preparation, its sealing properties appear not to be affected. [12][13][14] MTA is also most commonly used as a retrograde filling material to seal apical ramifications during endodontic root resection due to its previously mentioned properties. 12 In the current case report, since endodontic therapy was commenced prior to surgical intervention, it was crucial to select a filling material that would not only maintain long-term sealing but would also have bioactive properties once it was exposed to the periodontal and bone tissues upon hemisectioning of the fused tooth. 12 This in addition to the presence of the bone graft  3 mo  1  2  1  1  2  3  0  0  0  0  0  0   18 mo  2  3  2  3  2  5  0  0  0  1  0  3   48 mo  1  1  1  1  1  5  0  0  0  0  0  3   60 mo  2  2  1  1  1  3  1  material and enamel matrix derivative which would-together with the MTA-potentially provide an excellent substrate for new hard tissue formation and periodontal re-attachment. The periodontal strategy applied was to try and obliterate the resultant socket from extraction of the mesiodens in order to promote tissue regeneration and preserve bone around the remaining central incisor. Splinting was also applied to prevent tooth movement and stabilize the ensuing clot. The lag period between surgery and commencement of active orthodontic therapy in the current work was to allow these tissues to regenerate uninterrupted. The use of enamel matrix derivative (EMD) in conjunction with the bone alloplast plays a crucial role in orchestrating tissue healing and bone formation. Studies indicate that EMD significantly decreases interleukin-1 beta (IL-1β) and RANKL expression, thereby promoting bone remodeling. EMD increases bacterial and tissue debris clearance, as well as fibroplasia and angiogenesis by inducing endothelial cell proliferation, migration, and capillary-like sprout formation. 15 Another important aspect of EMD is its reported biomimetic effect and its capacity to play a role in dentin, acellular cementum, and alveolar bone formation during embryonic tooth development. 16 Therefore, the use of EMD was an attempt to prompt the regeneration of not only new bone, but also of a more favorable periodontal attachment to the hemisectioned tooth. With the same methodology, a reported study showed a higher incidence of healed periodontal ligament tissues (PDL) around re-implanted teeth in beagle dogs. 17 Other histologic studies demonstrated that EMD results in limited epithelial down growth. Moreover, human biopsies have reported the possibility of complete periodontal regeneration or new connective tissue attachment after EMD application to roots in intra bony periodontal defects. 18 Unlike regular periodontal surgery, periodontal measurements at the mesiolabial aspect of tooth #21 at the site of the extracted mesiodens were constantly changing. Three months after surgery, there was a 3 mm CAL which increased to 7 mm at one year. After starting the orthodontic movement, further CAL reached 9mm then stabilized at 7 mm after 4 years. An explanation is the possibility that moving the tooth led to bone and tissue remodeling and hence the increased measurements during active orthodontic movement. Moreover, clinical and radiographic examination revealed the presence of a deep groove running from the cervical aspect of the tooth including a great aspect of the root, probably due to cutting through the root of the mesiodens at a slightly more distal plane. This groove might have predisposed to plaque retention and some attachment loss. Although the deep periodontal pocket that developed may be considered a clinical shortcoming of this case, a decision to delay the second intervention was made to avoid disturbing bone remodeling during the phase of active orthodontic intervention. Additionally, a mid-line diastema remained again possibly due to the retained root apex which may have prevented closure of this space during orthodontic activation. These sub-optimal outcomes lead to the decision to perform a second surgery to improve the final outcome which may include orthodontic management again in the future. Other cases studies such as that by Kim et al 19 while show a better final outcome did not represent the same challenges as found in the current case including the presence of pulpal communication which entailed root canal therapy of the tooth prior to resection and profound treatment planning using multiple CBCT scans. While this case is similar to ours, it appears very difficult to have ideal results due to the many variables involved. A compromise is usually reached, and satisfactory, stable clinical, and esthetic results are considered sufficient by the clinician particularly if the patient is satisfied with the final result. Indeed, the remaining sites at both central incisors were normal and in line with a clinically healthy periodontal attachment. Continuous follow-up and periodontal maintenance were carried out during the follow-up period and a second surgical intervention was performed using PRF. The choice to use PRF was done to avoid excessive costs by the re-use of EMD for the second surgery in addition to the ability of PRF to serve as a membrane to augment the mucoperisoteal flap thereby possibly contributing as well to the overall enhanced results. This is in virtue of its well-documented benefits in regenerative dentistry applications and oral surgery indications. 20 Indeed, this lead to further probing depth and attachment loss reduction. Regarding the orthodontic results, they showed improvement and normalization of facial and dental arch relationships due to the use of retraction mechanics in the upper arch with gentle force control, which was chosen to suite the surgical-endodontic treatment that was performed in the area of the upper central incisors, as well as facilitating proper follow-up of changes in the periodontally and endodontically treated tooth. During the initial evaluation of the patient, the decision to extract the fused central and supernumerary tooth could have resulted in correction of the overjet and have stable occlusion results, yet it would have jeopardized the chance to have a normally shaped dentition and smile similar to that in the presence of the natural centrals, laterals, and canines. The risk of undergoing retraction of the surgically managed segment was finally evaluated after one-year follow-up, since the patient and his