A cross-sectional study of age-related changes in the position of upper and lower lips relative to the esthetic plane

Abstract Understanding age-related changes in the position of the upper lip relative to the esthetic plane (UL-EP) and lower lips relative to the esthetic plane (LL-EP) is crucial for optimizing aesthetic outcomes in orthodontic and orthognathic treatment. Previous studies often lack comprehensive a...

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Main Authors: Xiaoqi Zhang, Waseem AI-Gumaei, Lu Xing, Xiaoqian Zhang, Minqi Li, Hu Long, Wenli Lai
Format: Article
Language:English
Published: Nature Portfolio 2025-04-01
Series:Scientific Reports
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Online Access:https://doi.org/10.1038/s41598-025-98777-4
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author Xiaoqi Zhang
Waseem AI-Gumaei
Lu Xing
Xiaoqian Zhang
Minqi Li
Hu Long
Wenli Lai
author_facet Xiaoqi Zhang
Waseem AI-Gumaei
Lu Xing
Xiaoqian Zhang
Minqi Li
Hu Long
Wenli Lai
author_sort Xiaoqi Zhang
collection DOAJ
description Abstract Understanding age-related changes in the position of the upper lip relative to the esthetic plane (UL-EP) and lower lips relative to the esthetic plane (LL-EP) is crucial for optimizing aesthetic outcomes in orthodontic and orthognathic treatment. Previous studies often lack comprehensive adjustments for confounding factors and ignore the nonlinear relationships. This study addresses these issues by investigating age-related changes in upper and lower lip positions relative to the E-line. This cross-sectional study analyzed the lip positions of 2961 individuals (Age: 21.45 ± 7.43). Data were adjusted for confounding factors, including gender, dental, skeletal, and soft tissue parameters. Statistical methods, including Restricted Cubic Splines (RCS), multivariate regression, interaction analysis, and mediation analysis, were employed to identify age-related changes and their interactions. The findings indicate a significant decrease in both UL-EP and LL-EP distances with increasing age, following non-linear patterns of rapid decline, slight increase, and gradual decrease. Interaction analysis revealed significant interactions between age and variables such as gender, ANB, SN-MP, L1-MP, and overjet. The UL-EP decreases most rapidly in males with a Class III hypodivergent skeletal pattern and lingual inclination of lower incisors. In contrast, the LL-EP decreases most rapidly in patients with a Class III skeletal pattern and normal overjet. Mediation analysis suggests that age influences lip position through factors such as overjet, ANB, L1-MP, and Prn-Sn. These findings underscore the multi-phase, non-linear changes in lip position with age and highlight the critical role of age-specific considerations in orthodontic and orthognathic treatment planning. By identifying precisely when, where, and for whom these changes occur, clinicians can facilitate more individualized and effective outcomes.
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spelling doaj-art-690de3aad178486a993d6748ace2b4282025-08-20T03:13:57ZengNature PortfolioScientific Reports2045-23222025-04-0115111210.1038/s41598-025-98777-4A cross-sectional study of age-related changes in the position of upper and lower lips relative to the esthetic planeXiaoqi Zhang0Waseem AI-Gumaei1Lu Xing2Xiaoqian Zhang3Minqi Li4Hu Long5Wenli Lai6State Key Laboratory of Oral Diseases, National Clinical Research Center of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan UniversityState Key Laboratory of Oral Diseases, National Clinical Research Center of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan UniversityState Key Laboratory of Oral Diseases, National Clinical Research Center of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan UniversityYunnan Key Laboratory of Stomatology Affiliated Hospital of Stomatology School of Stomatology Kunming Medical UniversityDepartment of Bone Metabolism, School and Hospital of Stomatology, Cheeloo College of Medicine , Shandong University & Shandong Key Laboratory of Oral Tissue Regeneration & Shandong Engineering Research Center of Dental Materials and Oral Tissue Regeneration & Shandong Provincial Clinical Research Center for Oral DiseasesState Key Laboratory of Oral Diseases, National Clinical Research Center of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan UniversityState Key Laboratory of Oral Diseases, National Clinical Research Center of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan UniversityAbstract Understanding age-related changes in the position of the upper lip relative to the esthetic plane (UL-EP) and lower lips relative to the esthetic plane (LL-EP) is crucial for optimizing aesthetic outcomes in orthodontic and orthognathic treatment. Previous studies often lack comprehensive adjustments for confounding factors and ignore the nonlinear relationships. This study addresses these issues by investigating age-related changes in upper and lower lip positions relative to the E-line. This cross-sectional study analyzed the lip positions of 2961 individuals (Age: 21.45 ± 7.43). Data were adjusted for confounding factors, including gender, dental, skeletal, and soft tissue parameters. Statistical methods, including Restricted Cubic Splines (RCS), multivariate regression, interaction analysis, and mediation analysis, were employed to identify age-related changes and their interactions. The findings indicate a significant decrease in both UL-EP and LL-EP distances with increasing age, following non-linear patterns of rapid decline, slight increase, and gradual decrease. Interaction analysis revealed significant interactions between age and variables such as gender, ANB, SN-MP, L1-MP, and overjet. The UL-EP decreases most rapidly in males with a Class III hypodivergent skeletal pattern and lingual inclination of lower incisors. In contrast, the LL-EP decreases most rapidly in patients with a Class III skeletal pattern and normal overjet. Mediation analysis suggests that age influences lip position through factors such as overjet, ANB, L1-MP, and Prn-Sn. These findings underscore the multi-phase, non-linear changes in lip position with age and highlight the critical role of age-specific considerations in orthodontic and orthognathic treatment planning. By identifying precisely when, where, and for whom these changes occur, clinicians can facilitate more individualized and effective outcomes.https://doi.org/10.1038/s41598-025-98777-4E-lineEsthetic planeLipsFacial estheticsAgeCephalometric
spellingShingle Xiaoqi Zhang
Waseem AI-Gumaei
Lu Xing
Xiaoqian Zhang
Minqi Li
Hu Long
Wenli Lai
A cross-sectional study of age-related changes in the position of upper and lower lips relative to the esthetic plane
Scientific Reports
E-line
Esthetic plane
Lips
Facial esthetics
Age
Cephalometric
title A cross-sectional study of age-related changes in the position of upper and lower lips relative to the esthetic plane
title_full A cross-sectional study of age-related changes in the position of upper and lower lips relative to the esthetic plane
title_fullStr A cross-sectional study of age-related changes in the position of upper and lower lips relative to the esthetic plane
title_full_unstemmed A cross-sectional study of age-related changes in the position of upper and lower lips relative to the esthetic plane
title_short A cross-sectional study of age-related changes in the position of upper and lower lips relative to the esthetic plane
title_sort cross sectional study of age related changes in the position of upper and lower lips relative to the esthetic plane
topic E-line
Esthetic plane
Lips
Facial esthetics
Age
Cephalometric
url https://doi.org/10.1038/s41598-025-98777-4
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