Molar Intrusion using TADs in the Management of an Anterior Open Bite: A Case Report

Case report

A fit and well 16-year-old white male was referred by his general dental practitioner complaining that his front teeth did not meet. There was a history of digit sucking until the age of 5 years. Extra-orally, he presented with a Class I skeletal profile with an increased lower anterior face height (LAFH) and increased maxillary–mandibular planes angle (MMPA). He had competent lips and no obvious asymmetries. On smiling, there was increased posterior gingival show and reduced upper incisor show. Intra-orally, he presented in the permanent dentition with a moderately restored LL6, uneven wear of UR1 and UL1, and the upper arch was spaced with an increased curve of Spee. In occlusion, he had a Class I incisal relationship, a 4-mm anterior open bite, a 2-mm overjet, bilateral Class I molar relationships and bilateral ¼ unit Class II canine relationships. The centrelines were coincident (Figures 1 and 2).

A panoramic radiograph indicated crowded third molars, a large restoration on the LL6 and occlusal caries in the LL7. Cephalometric analysis indicated a skeletal I base with increased vertical proportions (a steep MMPA and LAFH percentage) and proclined lower incisors (Figure 3) (Table 1).

Treatment objectives

The treatment objectives for the patient were to establish a normal overbite, align the anterior teeth for ideal inclination, and improve the facial and dental aesthetics.

Treatment options

Two treatment options were presented to the patient. The first involved the extraction of the UR8, UL8, LL6 and LR8 to relieve crowding and upper and lower fixed appliances to prepare for orthognathic surgery. Surgery would consist of a Le Fort I maxillary osteotomy with differential maxillary impaction to allow for autorotation of the mandible and closure of the anterior open bite.

The second treatment option involved the extraction of the UR8, UL8, LL6 and LR8 to relieve crowding, upper and lower fixed appliances and two palatal TADs with a modified transpalatal arch for molar intrusion to close the anterior open bite.

The patient opted for orthodontic camouflage. He was informed of the planned treatment and consent was obtained.

Treatment progress

The patient had his carious cavities restored by his general dental practitioner and was referred to the Oral Surgery department for the removal of the UR8, UL8, LL6 and LR8. A modified rigid transpalatal arch was fitted from the upper first molars with 5-mm clearance from the palate.

Both arches were bonded with 0.022” x 0.028” MBT-prescription pre-adjusted edgewise appliances. Dental levelling and alignment were achieved with a sequence of 0.014” and 0.018” nickel titanium arch wires, followed by rectangular nickel titanium (0.016” x 0.022” and 0.019” x 0.025”), leading to 0.019” x 0.025” stainless steel working arch wires. All upper arch wires were swept with an increased curve of Spee to maintain both the existing increased curve of Spee and the anterior open bite. This was to ensure there would be no incisor extrusion.

Once in working arch wires, TADs were placed for molar intrusion. After local anaesthesia infiltration in the palate, two 1.5-mm-diametre and 9-mm-length long-necked TADs were inserted palatally between first and second molars on either side using a slow speed contra-angle handpiece. The TADs were loaded immediately with elastic chain to the TPA hooks to produce an intrusive force (Figure 4). After three months of molar intrusion (Figure 5a), a new lateral cephalogram was taken (Figure 6), which showed proclination of the upper and lower incisors, reduction in the LAFH and MMPA, and reduction in the anterior open bite (Table 1).

After 6 months, we felt that we had achieved sufficient molar intrusion, so we removed the TPA and bonded molar tubes on the first molars and began retracting upper and lower labial segments and closing the LL6 space using elastic chain (Figure 5b). The mesially impacting LL8 was disimpacted using a pushcoil between the LL7 and LL8 on a round nickel titanium wire (Figure 7).

Radiographs taken 26 months into treatment show normalized incisor inclinations, an increased interincisal angle and average vertical dimensions (Figure 8). There was improvement in the apical base relationship (ANB) due to the counterclockwise autorotation of the mandible (Table 1). There was slight blunting of the upper lateral incisor roots.

Active orthodontic treatment was complete in 30 months (Figure 9). After 3 months of occlusal and gingival settling, the patient was referred to his general dental practitioner to restore the wear of his UR1 and UL1 (Figure 10). Upper and lower vacuum-formed retainers were provided for lifelong wear.

Treatment results

A balanced facial profile, improved smile aesthetics and sound interdigitation were achieved. The photographs show improvement in the overbite and the vertical dimensions. The upper centerline is in line with the facial midlines, but the lower centerline has veered to the left due to loss of control during space closure in the lower left quadrant. This could have been prevented, perhaps, with skeletal anchorage in the mandible during space. On smiling, the patient's upper incisor show and upper posterior gingival show have been greatly enhanced. The patient was satisfied with the treatment results, and the outcome was stable at 6 months.

Discussion

This patient's chief complaint was functional in nature, which we addressed successfully. The aesthetic improvements were a bonus for the patient, who was very pleased with the result.

An MBT bracket prescription was used for: increased palatal root torque in the upper incisors to prevent the appearance of over retraction when correcting the upper labial segment inclination; increased lingual crown torque in the lower incisors to prevent forward tipping of the already-proclined lower labial segment; and increased buccal root torque in the upper molars to prevent the palatal cusp tips from creating interferences that might prop the mouth open.

Using a modified TPA meant fewer TADs were needed for molar intrusion. The 1.5-mm diameter is ideal for intra-radicular placement, the 9-mm length is necessary for stability in the posterior maxilla, and the long neck is preferred to prevent soft tissue overgrowth over the TAD. There is greater room for placement of TADs in the palate as opposed to buccally, as there is more intra-radicular space where the upper molars have just one palatal root rather than two buccal roots. The TPA is modified by allowing 5-mm palatal clearance to allow for molar intrusion, and with mesial and distal arms from the molar bands from which to apply the intrusive force using the elastic chain from the TADs.

The correction of the anterior open bite was achieved predominantly through counterclockwise autorotation of the mandible secondary to molar intrusion and removal of upper third molars, and uprighting the upper and lower labial segments. There was also slight extrusion of the upper incisors (Figure 11). Restoration of the incisal wear with resin composite added the finishing touch to improve the smile aesthetics.

Anterior open bite correction was stable at 6 months, which is promising when we know that 80% of relapse occurs in the first year after active orthodontic treatment. The outlook for the stability of this anterior open bite closure is positive, as the patient had competent lips to start, the interincisal angle has increased due to the ‘drawbridge effect’ of retracting and minimally extruding the anterior segments, and the patient has no non-nutritive sucking habits or tongue thrust.

Conclusion

This case report presents an effective, well-tolerated, non-surgical alternative to close anterior open bites in non-growing patients using skeletal anchorage with TADs and fixed appliances. A great emphasis must be placed on retention, particularly in the first year after active orthodontic treatment. A longer follow-up is necessary to assess long-term stability of anterior open bite closure using this treatment modality.