Treatment effects and biomechanical analysis of TMA spring appliance

Background/Aim
Among Angle's classification, skeletal class III is the most difficult to treat. Treatment using the TMA spring intraoral appliance was investigated in the late mixed dentition and showed desirable effects. The present work aimed to investigate, biomechanically, the TMA spring appliance in the early mixed-dentition stage with specifically outlined force direction, duration, and magnitude in order to provide solid results that can be relied upon clinically.
Patients and methods
The sample consisted of 20 patients with an age range 8–10 years and an average of 8.6 years. Lateral cephalograms were taken and analyzed before treatment (T1), posttreatment (T2), and postretention (T3). The patients were instructed to wear the TMA spring appliance 12–16 h/day for 9 months, followed by 6 months of retention. The appliance delivered a force of 400 g/per side as measured with the force gauge.
Results
Comparing T1–T2 and T1–T3, there was a significant difference between sexes in points U6/S perpendicular; =0013 and =0.0159, SNA (=0.0122, =0.0371), and ANB (=0.0491) at T1–T2. There was a significant difference in the whole sample for all the skeletal, dental, and soft-tissue measurements; value less than 0.05, regarding treatment and retention changes.
Conclusions
The TMA spring appliance enhanced the cooperation of the patients, resulted in forward movement and clockwise rotation of the maxilla. Mandibular clockwise rotation and dentoalveolar changes also contributed to the overall correction of class III.