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Bulletin #74 February 2018

The evolving orthodontic appliance: an appliance for all seasons

The first visit of the patient to my office was in November 2016, at the age of 11.2 years, when he was accompanied by his father. The complaint was that the child’s maxillary anterior permanent teeth had not erupted into the mouth and that there were 3 deciduous incisors still in place.

Diagnosis

74_Fig._1

Fig. 1. Intraoral views of the dentition in occlusion at the first visit of the patient, in December 2016. Aside from the first permanent molars and the left maxillary lateral incisor (arrow), all other maxillary teeth were unerupted.


74_Fig._2

Fig. 2. Occlusal views of the dentition on the same day.


On examination, I noted that the only erupted permanent teeth were the four first molars and the 4 mandibular incisors, while the left maxillary lateral incisor and right maxillary first premolar had just begun to erupt (Fig. 1, 2)

The dentition showed all the signs of deterioration due to overall dental neglect. Several deciduous teeth exhibited carious lesions and some had been restored. Premature extraction and consequent space loss had occurred in both jaws and several of the remaining deciduous teeth had become mobile due to the normal shedding process. In the absence of maxillary incisors, the mandibular incisors had over-erupted. The inter-arch relations were essentially normal and crowding was expected to be a feature of the full permanent dentition, for which the space loss bore a part of the blame.

74_Fig._3

Fig. 3. Three periapical view of the anterior maxilla to show the presence of the unerupted incisor teeth, together with an indeterminate number of superimposed teeth.


Inspection and palpation of the anterior maxilla revealed bulges where permanent teeth were obviously present. The individual periapical radiographic films of the same area that the patient had brought to this first visit (Fig. 3) had been taken by a general dentist and revealed the presence of additional unerupted teeth. The child was referred for a CBCT examination.

74_Fig._4

Fig. 4. The panoramic view of the maxilla culled from the CBCT imaging.


The 2D panoramic view of the maxilla culled from the CBCT imaging scan (Fig. 4) showed the presence of all the teeth, including third molars. In the incisor region, there was superimposition of the unerupted incisors, which made identification difficult but here, too, unerupted median supernumerary tooth/teeth could also be seen. The canines and lateral incisors on each side of the maxilla appeared to be partially transposed. According to the degree of root development of the various groups of normal teeth, the dental age was set at 9-10 years i.e. 1-2 years retarded dental development.

Fig. 5. Click https://youtu.be/1U1v6E4ySYo to see a 3D video clip of the surface anatomy of the over-retained deciduous teeth, the unerupted permanent teeth and the supernumerary teeth in the anterior anterior maxilla, showing their locations and inter-relations.

Fig. 6. Click https://youtu.be/6FYkSXliroQ to see a 3D MPR video clip of integrated serial cuts in the 3 planes of space.


The axial and cross-sectional individual slices are not shown here. The 3D surface anatomy video clip (Fig.5) and 3D video clips of the serial cuts integrated in the 3 planes of space (Fig. 6) facilitated identification and location of the two supernumerary teeth on the palatal side of the central incisors, so that planning an escape route for the impacted tooth then became child’s play. These views also served to illustrate that the roots of the lateral incisors were displaced laterally and very much lingually, as they proceeded in an apical direction, due to the space-occupying supernumerary teeth.

Aims of Treatment

Although the patient was 11 years of age, his dentition corresponded to a dental age of 9-10 years, which meant that overall assessment and treatment planning of the several components of the malocclusion were premature, since most of the teeth were not expected to erupt for another 2 years or so. There is always a degree of uncertainty, however small, regarding the chances of success in resolving impactions and this dilemma must be settled before moving on to the next step. Thus, it was considered important to eliminate the cause of the impacted maxillary incisors and to bring these teeth into the arch. This entailed deciding on a short phase 1 treatment plan aimed solely at bringing the incisor into the dental arch and aligning them. A phase 2 treatment would be necessary to eliminate the crowding, for which consideration would need to be given to the possibility of extracting permanent teeth. Space creation or extraction space closing, with final artistic alignment and root torqueing would be left until that later date. However, it must be clearly understood that, for as long as the prognosis of the impacted incisors was not reasonably certain, further planning is ill-advised.

Treatment details

74_Fig._7

Fig. 7a. At surgery in January 2017, labial and palatal flaps were reflected to provide access for exposure of the incisors and for the extraction of the supernumerary teeth, respectively (surgery by Dr. Harvey Samen)

Fig. 7b. Eyelet attachments were bonded to the labial surfaces of the 3 impacted incisors, with twisted stainless steel ligatures hanging down loosely. Note the axial orientation of the eyelet attachments on the teeth.

Fig. 7c. The labial and palatal flaps were sutured back to their place (closed exposure technique), with the ligatures exiting through the sutured edges of the flaps. Note the passive position of the 0.036” self-supporting labial arch.

Fig. 7d. The labial arch has been flexed upwards and held in that position by ensnaring it with the twisted steel ligatures from each of the impacted incisors, applying extrusive force.

Fig. 7e. The occlusal view of the maxillary dentition at the completion of the surgical procedure and after extrusive force was applied.


An orthodontic appliance was required that could initially apply extrusive forces on the unerupted incisors and then be modified to apply mesiodistal and rotational forces once these teeth had erupted. To this end, molar bands with soldered 0.036” round buccal tubes and joined by a soldered stabilizing palatal arch were cemented into place (Fig. 7a). This unit represented the anchor base from which forces would be applied and against which the reactive forces would be absorbed.

It was not considered helpful to place brackets on the deciduous canines and first molars due to their expected and fairly imminent shedding. However, with such long spans present between molar bands and unerupted incisors, an archwire of considerable thickness would be necessary to apply the extrusive force and yet be self-supporting, in the absence of intermediate support in the premolar area. In order to obtain a vertical vector of force in the anterior region, the archwire was required to slide tightly in the molar tube, with no up-and-down “play,” which meant employing a full thickness, 0.036” gauge, stainless steel wire. The only distortion permitted would be its integral elasticity engendered by the intentional upward displacement (loading). The archwire was not inserted until the surgical episode itself.

Under local anaesthetic cover, the surgeon performed the procedure on January 1 2017. At surgery, the over-retained deciduous incisors, the right side deciduous canine, first molar and the two supernumerary teeth were extracted (Fig. 7a). Following the exposure of the impacted incisors, small eyelet attachments were bonded to their labial surfaces by the orthodontist. Each eyelet was threaded with a twisted soft steel ligature wire which was drawn down to exit the sutured edge of the replaced buccal and palatal flaps (Fig. 7b, c). Before the patient left the surgeon’s operatory, the orthodontist re-inserted the 0.036” labial archwire into the molar tubes and, with gentle finger pressure, flexed its anterior portion upwards and secured it there by turning the individual twisted wires ligatures over it (Fig. 7d, e). This created an extrusive force on the re-covered incisors, a force that may be easily calibrated in both magnitude and range with this method.

74_Fig._8

Fig. 8a, b. In April 2017, the 3 incisors have erupted. The eyelets were removed and orthodontic brackets were bonded in their place.


Four subsequent short visits to the orthodontist were required to progressively activate the labial arch in this way, before the 3 impacted incisors were fully erupted (Fig.8a, b). The self-supporting labial archwire was discarded and orthodontic brackets were substituted for the eyelets on the central incisors. At this and subsequent visits, brackets were placed on the lateral incisors, the first premolars and the deciduous left canine and both second deciduous molars. By October 2017, the 4 anterior teeth were aligned in all planes of space, except for the needed labial root torque on the right lateral incisor.

At this point, with the aims of the phase I treatment plan successfully achieved, the dilemma regarding the prognosis of the incisors was considered to be favourably resolved. The expected survival value of the incisors was declared similar to that of normally-erupted incisors in any other patient. Accordingly, a re-evaluation and extension of the treatment plan could be made to include the run-up to phase II.

74_Fig._9

Fig. 9. The panoramic view was taken in October 2017 after the newly-erupted incisors had been aligned and leveled. On the basis of a re-evaluation of the further development seen on this film, all the remaining deciduous teeth were removed together with the extraction of the four first premolar teeth.


In the present case, the degree of crowding in both jaws, the further root development of the unerupted canines and premolars were evaluated on a new panoramic film (Fig. 9). Additionally, the unerupted maxillary canines were now palpable labially overlapping the roots of the lateral incisors (Fig. 10). These facts made it desirable to eliminate the remaining deciduous teeth and, at the same time, to extract the four unerupted first premolars. It was felt that this could inter alia increase the chances of spontaneous canine eruption (Fig. 10). A mandibular lingual arch appliance was prepared and cemented into place in late November 2017, together with mandibular incisor brackets for the purpose of alignment of the incisors.

74_Fig.10

Fig. 10. In December 2017, the phase I treatment was considered complete. The appliances were left in place to function as space maintainers. With the canines in their palpably buccal ectopic locations (arrows), it was considered inappropriate to attempt the needed labial root torque of the lateral incisors. No attempt was made at to correct the midline discrepancy, nor to partially close off the excess space. These items should be dealt with in the phase II treatment, expected to commence in a year or so.


Adequate alignment was achieved a month later and the appliances were left in place as space maintainers pending the eruption of the remaining teeth, when brackets would be bonded and the phase II plan would be initiated. Labial root torqueing of the lateral incisors would only be appropriate after the canines had erupted and been drawn distally, away from their close proximity to the incisor roots, in the phase II treatment (Fig. 11).

74_Fig._11

Fig. 11. Occlusal views of the dentition at the completion of phase I in December 2017.


The evolving orthodontic appliance

In the mixed dentition period, when the incisors are impacted and the deciduous teeth will shortly exfoliate or are already lost, the ability to apply forces to erupt the incisors hinges on bands placed on the two permanent molars and, preferably linked by a transpalatal arch for support. Following the surgical episode, the only visible anterior signs of an appliance were the twisted steel ligatures and the self-supporting archwire. Three months later and once the incisors were fully erupted, brackets were substituted for the initial eyelets and the appliance became a fully bonded appliance, still with round buccal tubes and soldered palatal arch. Following the extraction of the four premolars and remaining deciduous teeth, a 0.020” round “straight” stainless steel wire was placed in the brackets.

It was anticipated that the premolars and canines would take a year or so to fully erupt and before they could be successfully bracketed. At that time, the molar bands would be removed and substituted by bands carrying rectangular cross-section tubes to be prepared for the stage II orthodontic treatment plan, in which appropriate torque control of the teeth would need to be established.