Digital Assessment of Vertical and Horizontal Esthetic Alignment in Young Adults: A Cross-Sectional Study

This study aimed to quantitatively evaluate the vertical and horizontal esthetic alignment parameters among young adults with high facial esthetic quality, thereby establishing reference benchmarks for natural facial symmetry and deviations.

A total of 220 participants aged 18-25 years were included following strict esthetic and dental inclusion criteria. Standardized frontal facial photographs were obtained and analyzed using digital design software. Vertical midline relationships (pupil-incisor, philtrum-incisor, pupil-philtrum) and horizontal planes (pupil-incisal, pupil-commissure, commissure-incisal) were measured. Vertical deviations were categorized into five groups, and horizontal relationships were classified as parallel or non-parallel. Gender-based differences were assessed using chi-square analysis (p < 0.05).

Reliability was excellent for vertical measurements (ICC = 0.93 intra-observer, 95% CI: 0.90-0.96; ICC = 0.88 inter-observer, 95% CI: 0.83-0.92) and substantial for horizontal plane assessments (Fleiss' kappa = 0.80; 95% CI: 0.72-0.87). Vertical midline alignment decreased progressively from the dental to the upper facial reference lines, with the highest coincidence observed in the philtrum-incisor relationship (48.6%) and the lowest in the pupil-philtrum alignment (23.4%). Horizontal plane parallelism showed a similar decreasing pattern toward upper facial structures. Gender comparisons revealed no significant differences in vertical midline alignment (p > 0.05). Commissure-incisal parallelism was significantly higher in males (p = 0.032), while other horizontal relationships showed no significant gender differences.

Vertical and horizontal esthetic relationships follow characteristic patterns across facial levels, reflecting the natural asymmetry of the human face. Gender-related differences were minimal and plane-specific rather than generalized. Objective digital measurements provide reliable reference data for clinicians in establishing facially driven esthetic treatment plans.

This study provides reference data for natural facial symmetry in young adults, highlighting that minor asymmetries are normal and often esthetically acceptable. Clinicians should focus on harmony with facial flow rather than perfect geometric symmetry. From a clinical perspective, objective digital assessment of vertical and horizontal reference relationships may assist clinicians in selecting appropriate esthetic reference planes during facially driven treatment planning. Rather than defining strict normative values, these findings support an individualized approach that respects natural facial variability.