2.2. Treatment objectives
Treatment objectives were to increase the patient confidence by restoring smile aesthetic, also to establish a class one occlusion, an ideal overjet/overbite and maintain the facial profile proportions.
Treatment plan was to reduce the front dental mass by extraction of #21 and mesializing #11 to correct the midline. Also comprehensive orthodontic treatment with four first premolar extractions was anticipated for relieving the severe crowding.
Treatment alternatives
Alternative treatment plans include extraction of two anterior double incisors and implant placement, or reduction of the incisor’s widths by splitting/hemisection and improvement of the esthetic by ceramic crowns. These options would be opened only after the patient’s skeletal maturation. Moreover, surgical, endodontic and prosthetic procedures were needed for those options. The patient preferred the less aggressive procedure therefore ext of #21 and mesialization of #11 was the chosen plan. The patient and his family granted approval for the publication of the treatment records.
Treatment progress
Due to the young age of the patient, emphasis on the oral hygiene instruction was always a priority of the visiting sessions. At the beginning, ext of #21 was ordered (Figure 5) and it was planned to consider #11 as two central incisors (readily existing in the form of a single macrodontic, fused tooth).
One week after the extraction of #21, bracket bonding of maxillary teeth (including the primary canines and molars) was performed (0.028 × 0.022-in slot size bracket, discovery® smart, Dentaurum, Germany).
Two central incisor brackets with the help of a stiff wire, as shown in figure 6, were bonded on the #11 at an exact same height to avoid unwanted forces among two parts of the fused tooth, also to increase its mesiodistal control.
0.014-in nickel titanium (Niti), 0.016-in Niti, 0.018-in stainless steel (SS) were sequentially placed in 3 months. On 0.018-in SS main archwire two tie back loop mesial to the first molars were formed. On this 18 ss working wire, 150 gram mesialization force was delivered to the #11 by incorporation of a segment of Niti push coil at right and elastomeric chain at left of fused incisor brackets.
After midline correction in 10 months, sequential extraction of primary molars and first premolars, immediately after their eruption, was ordered. Leveling and alignment of the teeth were performed according to the standard protocols. Treatment was completed in 26 months (Figure 7-10). Minor restorative treatment was done to slightly correct the form of the fused incisor (Figure 11). Hawley retainer for the upper and lower arch was provided for the patient.
Treatment results:
The facial profile remained unchanged after treatment (table 1 & figure 9). The patient smile was balanced and pleasing. The final occlusion showed a Class I occlusion with ideal overjet/overbite and coincident dental midlines. The maxillary right lateral incisor experienced palatal crown torque and labial root torque. In total, the incisor was moved across the MPS about 6 millimeters. The midline frenum was slightly stretched toward the left side but no major inflammation requiring periodontic procedures was observed. White spot lesions were observed particularly on the maxillary teeth. Based on the final radiographs, a proximation between the distal root of the fused incisor and the right lateral incisor was evident (All the other roots were parallel). That was inevitable because of the divergent roots of the fused incisor.
Discussion:
This case was a rare example of bilateral double teeth. Based on the literature, the prevalence of such condition is 5 out of 100,000 in the human being population 3. Movement of bi-rooted #11 through the MPS was successfully achieved. Indication of tooth movement through the MPS is closing a central incisor space which might be congenitally absent, severely malformed or hopeless to maintain. It aimed to avoid prosthetic treatment, reduce the number of extractions of healthy teeth, and help correct crowding and incisor proclination9. Major considerations in moving teeth across the MPS, are labial frenum inflammation and root resorption. Case studies reported that in growing patients that their suture is not yet ossified, moving incisors through the MPS would be less complicated, while in adult patients, root resorption reported to be a serious accompanying effect of teeth crossing the ossified suture. In the present study, the patient was in the early mixed dentition at the beginning of the treatment and the speed of #11 mesialization was comparable to a normal-sized tooth (0.98 mm per month). No dire root resorption was observed in this case while in Kato’s 9 and Follin’s7 studies root resorption were considerable. Chiho Kato reported replacing a missing maxillary incisor with the contralateral one in a 26 years old woman. In their case while the maxillary left incisor crown crossed the midline and 8.7% of the apex remained in the same side, the root length shortened 3.3 mm.9.
Bulut managed a case of fused maxillary central incisor by moving that across the MPS. In their case, no root resorption was observed, however frenectomy had been performed, also root canal therapy had to be done to prepare the tooth for casting restorations 11.
Likewise in the present study, a mild stretch in the maxillary frenulum toward the movement of #11 (the left side) was observed. However, its inflammation was minor and under the control. Therefore, there was no need to perform frenectomy as advised by a periodontist.
A disadvantage of this treatment plan was the long period of treatment time (26months).In spite of emphasis on the oral hygiene, the patient had lost his cooperation which resulted in poor oral hygiene and extensive white spots. Dividing the treatment period into two separate phases would have prevented such complications.
From esthetic point of view, this case, although acceptable, it was not ideal. The upper and lower midlines were coincident. However preservation of malformed incisor in front of the mouth was unattractive. A hemisection procedure to separate the teeth could be a solution. Since the #11 was asymptomatic and the patient was satisfied with the results only a minor restorative correction was performed.
Conclusion:
In complex cases of malformed teeth and severe crowding, it might be an appropriate option to move the tooth across the MPS in young patients.