Related Experiment Video
Updated: May 28, 2026
Measuring Maxillary Posterior Tooth Movement: A Model Assessment using Palatal and Dental Superimposition
Published on: February 23, 2024
Three-dimensional crown-root movement in first premolar extraction cases treated with two clear aligner systems based
Luyao Qu1,2, Runzhe Fang1,2, Ruomei Li1,2
1Department of Orthodontics, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Aims:
To quantify and compare the three-dimensional (3D) deviations of crown and root movements produced by two clear aligner systems based on different materials-SmartTrack (ST) and MasterControl S (MCS)-in first premolar extraction cases using a 3D crown-root registration approach.
Methods:
This retrospective cohort study included 29 patients (58 dental sides) treated with ST (n = 15) or MCS (n = 14). Pretreatment (T0) CBCT images were integrated with T0 and post-treatment (T1) intraoral scans and superimposed using palatal rugae as reference structures. Linear mixed-effects models (LMM) were applied to estimate between-material differences while adjusting for age, sex, and standardized planned movement magnitude. Estimates are reported with 95% confidence intervals (CI).
Results:
The two systems demonstrated no statistically significant difference in deviation in sagittal crown retraction of the maxillary central incisor (U1) (ST: 1.25 (1.30) mm; MCS: 2.13 (1.82) mm; LMM difference: - 0.81 mm; 95% CI - 1.89-0.28; P = 0.145). MCS demonstrated smaller deviation in sagittal root positioning for the second premolar (U5) (difference: 1.07 mm; 95% CI 0.21-1.93; P = 0.015) and first molar (U6) (difference: 1.04 mm; 95% CI 0.13-1.94; P = 0.025). ST showed improved control of U5 axial inclination (difference: 3.33°; 95% CI 0.27-6.39; P = 0.033) and torque (difference: 3.04°; 95% CI 0.08 to 6.00; P = 0.044). Both systems exhibited a consistent "roller-coaster effect", with no significant difference in unplanned U1 extrusion (difference: 0.14 mm; 95% CI - 0.73-1.02; P = 0.747).
Conclusions:
The biomechanical performance of clear aligner systems appears to vary depending on tooth position and movement vector. SmartTrack demonstrated better control of premolar angulation and torque, whereas MasterControl S showed closer agreement with the planned sagittal root position.
