Changes in Maxillary Incisor Inclination Before and After Orthodontic Treatment Across Vertical Skeletal Patterns

TL;DR

This study examines how maxillary incisor inclination changes before and after orthodontic treatment in adults with different facial structures and finds that incisor stability is influenced by treatment mechanics and facial patterns.

Contribution

The study provides new insights into the relationship between vertical skeletal patterns and maxillary incisor stability during orthodontic treatment.

Findings

No significant changes in maxillary incisor inclination were observed post-treatment across all groups.

Hyperdivergent patients showed no significant correlations between incisor angulation and skeletal axes.

Normo- and hypodivergent patients exhibited stronger associations between incisor angulation and skeletal axes.

Abstract

Objective: To evaluate changes in maxillary incisor inclination before and after orthodontic treatment in adults with different vertical facial patterns (normodivergent, hypodivergent, hyperdivergent) and to assess the relationship of incisor inclination to facial and growth axes using cephalometric and photographic records. Materials and Methods: This retrospective study included 144 non-growing patients (96 females, 48 males) with available pre- and post-treatment lateral cephalograms and smiling profile photographs. Patients were classified into three groups based on mandibular plane angle (MP/SN): normodivergent (n = 66), hypodivergent (n = 35), and hyperdivergent (n = 43). Angular measurements assessed maxillary incisor inclination and growth/facial axes. Clinical crown angulation (CCA) was evaluated from profile photographs. Statistical analyses included paired t-tests, ANOVA with Bonferroni post hoc tests, and Pearson correlation. Results: No significant changes in maxillary incisor inclination were observed post-treatment in any of the groups. Significant skeletal changes were noted in the hypodivergent group, including increases in MP/SN (p = 0.011) and IMPA (p = 0.014). Intergroup comparison revealed significant differences in changes in Facial Axis/H (p = 0.020) and MP/SN (p = 0.025). Correlations between CCA and skeletal axes were more pronounced in normo- and hypodivergent groups, while hyperdivergent patients showed no significant associations. Conclusions: These findings suggest that the stability of maxillary incisor inclination reflects controlled torque mechanics during treatment. In normo- and hypodivergent patients, skeletal axes may help guide esthetic incisor positioning; however, in hyperdivergent patients, soft tissue and smile evaluation should play a greater role when determining final incisor inclination.

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