ISW Treatment for Skeletal Class III Malocclusion with Poor Arch Coordination

An adult female (30 years old) came to our clinic with a chief complaint about not able to chew food well and bilateral posterior crossbite. Clinical examination revealed skeletal Class III malocclusion with posterior crossbite and poor arch coordination. Due to her refusal to receive orthognathic surgery, non-surgical treatment was adopted. With successful width decrease of lower arch by two 1st molars extraction; then mesial drive of two 2nd and 3rd molars with closed coil spring, Class III malocclusion was corrected by ISW technique combined with Class III elastics. Treatment was completed in about 18 months and a desirable occlusion after the active treatment was achieved.


Introduction
Coordination between the upper and lower arches is one of the most important aspects of achieving stable functional and esthetic results during orthodontic treatment. Because a transverse discrepancy could induce an adverse periodontal response, unstable dental camouflage, and functional and esthetic problems, maintenance of an adequate overjet during treatment should be essential [1][2][3][4][5][6]. ISW (improved super-elastic Ti-Ni alloy wire, developed by Tokyo Medical and Dental University) for nonsurgical treatment of adult skeletal Class III malocclusion with poor arch coordination will be discussed.

History and Diagnosis
An adult female (26 years old) came to our clinic with a chief complaint of not able to chew food well and bilateral posterior crossbite. Her lateral profile was concave, and the frontal view showed slightly facial asymmetry phenomenon ( Figure 1). Clinical examination revealed bilateral Class III molar relationship, right canine class III tendency with left canine class I relationship, bilateral posterior crossbite, and mild crowding over lower anterior teeth with mandibular shift to right side resulting in facial asymmetry ( Figure 2). Panoramic film showed #28, #38, #48 existence ( Figure 3). This patient refused to receive orthognathic surgery, so we decided to adopt non-surgical orthodontic treatment. LH (Low Hysteresis Improved Super-elastic Ti-Ni alloy wire, developed by Tokyo Medical and Dental University) technique with mesial drive of two 2nd and 3rd molars mesial drive of closed coil spring successfully decreases the width of lower arch by two 1st molars extraction, Class III malocclusion was corrected by ISW technique combined with Class III elastics. Treatment was completed within 18 months and a desirable occlusion with adequate overbite and overjet was achieved. The cephalometric analysis showed a skeletal class III jaw relationships (SNA: 74.    The radiographic methods of the research include intraoral photos, posteroanterior cephalometric projection, lateral cephalometric projection and panoramic x-ray films. Also, the cephalometric analyses before and after the treatment were presented in this case. About the treatment plan, full-mouth DBS (Direct Bonding System) and the method of leveling with 0.016 x 0.022 LH were used from the start of active treatment, and elastic chain was also used between 35 & 37 and 45 & 47. And then, for mesial drive of #37,47, closed coil springs (100 gf) were set over crimpable hook-37 and crimpable hook-47. Intermaxillary elastics was also set to facilitate 37 & 47 mesial drive and uprighting. Torque control of #36,37,46,47 was subsequently perfomed and #36,37,46,47 were re-DBS with #16,17,26,27 brackets, 0.018 x 0.025 ISW was placed to reinforce the torque control to the lower dentition. For the finishing and detailing of the case, Re-DBS of #41,42 for better rotation control. IME was set between 14 to 47 and 24 to 37 for interdigitation and tripping was performed over 32 to 42 for reduction of black triangle. Crown lingual torque was added on #38 and reverse curve was set in the lower dentition. After debonding, a circumferential retainer was delivered for the upper arch and a Hawley retainer for the lower arch was used for the retention.
The analysis showed a skeletal Class III with bilateral posterior crossbite. L1 to mandibular plane angle showed a severe labially tipped upper incisor and slightly lingually tipped lower incisor, to correct the poor arch coordination lower bilateral first molar must be extracted to decrease the lower arch length efficiently.

Treatment Results
After 18 months of active treatment, for the final finishing and detailing stage, on 2009-12-07, Re-DBS of #41,42 was performed for better rotation control. IME was set between 14 to 47 and 24 to 37 for interdigitation, and stripping was performed over 32 to 42 for reduction of black triangle. Crown lingual torque was also added on #38 and reverse curve was set in the lower dentition ( Figure  12). On 2010-01-27, debonding of full mouth bracket was performed and circumferential retainer was delivered for the upper arch and Hawley retainer for the lower (Figure 13). For the total treatment time of 12 months, a stable occlusion was achieved, and the asymmetrical appearance improved after the treatment (Figures 14-19).

5/3
After a retention period of 6 months by a functional appliance to maintain the intermaxillary relationship and to adjust the musculature tension, a new balanced facial appearance was observed.

Discussion
Treatment of Class III case is always a challenging scope of orthodontics in its difficulty and time consuming. The key element to achieve a successful therapy lies exactly in differentially diagnosing a Class III case as dental/functional or skeletal problem. This case showed true skeletal Class III from her cephalometric analysis. After 18 months of non-surgical orthodontic treatment, her poor arch coordination was corrected [7][8][9][10][11][12][13].

Length and Width Change of Lower Arch
When using ISW for molar mesial drive, there are space closure effect and toe in effect. These two effects aided in better molar relationship and stable interdigitation (Figure 20).

Torque Control (Offset) During 37,47 Mesial Drive
The time interval for molar mesial drive was shown on Figure  21. After 2 months of active treatment considered stable. After 6 th months of active treatment, 37,47 lingual tipping was corrected by off -set. And when it steps to 11th months after active treament, lingual tipping was under control (Figure 21).

Effect of Intermaxillary Elastics (IME)
For the comparison of intermaxillary elastics (IME) effect, 8 months after active treatment was the uprighting effect. While 9 months after active treatment demonstrated the mesial drive effect, 12 months and 15 months of intermaxillary elastics (IME) showed significant phenomenon of interdigitation effect and bite control (extrusion) effect ( Figure 23).

Conclusion
This case showed skeletal Class III malocclusion with bilateral posterior crossbite. Poor arch coordination results in difficulty in chewing food well. In answer to this patient's decision, non-surgical treatment was adopted. With successful width decrease of lower arch by two 1st molars extraction; then mesial drive of two 2nd and 3rd molars with closed coil spring, Class III malocclusion was corrected by ISW technique combined with Class III elastics. After 18 months of active treatment, a normal occlusion and a desirable cusp interdigitation were achieved. Therefore, adult posterior crossbite with mild crowding combined with skeletal class III tendency can be treated with LH treatment.