Comparative evaluation of vertical dimension changes with clear aligners and fixed appliances: A prospective cephalometric cohort study.

BACKGROUND

The control of vertical dimension remains a critical aspect of comprehensive orthodontic treatment. This study compared vertical dimensional changes produced by clear aligners (CAs) to those produced by fixed appliances (FAs) during comprehensive orthodontic treatment, assessing whether modern aligner therapy provides comparable vertical control with conventional mechanics.

METHODS

A prospective cohort of 52 adults (CA group: 26 and FA group: 26) was evaluated. Baseline comparability was confirmed for age, sex, malocclusion type, and skeletal pattern. Standardized lateral cephalograms were obtained before (T0) and after treatment (T1). Cephalometric variables included the SN-GoGn (mandibular plane angle), FMA (Frankfort-mandibular plane angle), N-Me (total anterior facial height), S-Go (posterior facial height), and ANS-Me (lower anterior facial height). Intraobserver and interobserver reliability exceeded an intraclass correlation coefficient of 0.90. Paired and intergroup comparisons were performed (α = 0.05).

RESULTS

Both groups exhibited small increases in vertical parameters within physiological limits. In the CA group, the SN-GoGn angle showed a statistically significant but clinically minor increase (<1°; P = 0.016). The FA group presented slightly greater increases in SN-GoGn and plane angle FMA (P <0.05), consistent with mild clockwise mandibular rotation. Linear measurements (N-Me, ANS-Me, and S-Go) increased slightly in both groups. Intergroup comparisons (ΔT1-T0) revealed no statistically significant differences in any variable (P >0.05), and effect sizes were small (Cohen d <0.30).

CONCLUSIONS

Vertical dimensional changes associated with CA and FA treatments were minimal and comparable. Under current protocols, CAs provide adequate vertical control in mild-to-moderate malocclusions without inducing clinically relevant mandibular rotation. Further randomized and 3-dimensional studies are warranted to confirm these findings in more complex vertical discrepancies.