Int J Stomatol

Int J Stomatol ›› 2025, Vol. 52 ›› Issue (6): 748-754.doi: 10.7518/gjkq.2025086

• Orthodontics • Previous Articles     Next Articles

Factors influencing the efficiency of maxillary expansion in clear aligner orthodontic treatment

Ziwei Tang(),Yu Jin,Wenli Lai()   

  1. State Key Laboratory of Oral Diseases & National Center for Stomatology & National Clinical Research Center for Oral Diseases & Dept. of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China
  • Received:2024-05-17 Revised:2025-07-06 Online:2025-11-01 Published:2025-10-23
  • Contact: Wenli Lai E-mail:745749262@qq.com;wenlilai@scu.edu.cn

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Abstract:

Objective To assess the factors influencing the efficiency of maxillary expansion during clear aligner treatment (CAT). Methods A total of 54 nonextraction CAT patients undergoing maxillary expansion were selected. Baseline data were collected, and crown lengths were measured via cone-beam computed tomography (CBCT). A model overlap was used to measure the maxillary expansion efficiency and torque changes. Linear analysis was performed to identify factors influencing expansion efficiency. Results Single-factor linear analysis revealed that maxillary first-molar expansion efficiency was significantly influenced by age, root length, crown-root ratio, attachment design, designed and actual expansion amount, actual torque changes, and designed-actual torque changes (P<0.05). Stepwise multivariate linear ana-lysis identified the crown-root ratio, attachment design, and designed and actual expansion amount as significantly affec-ting maxillary first-molar expansion efficiency (P<0.05). Conclusion During CAT expansion treatment, to the focus should be on the patient’s crown-root ratio. Bilateral attachment design and careful consideration of expansion amount limits in treatment planning are crucial to enhancing patient expansion efficiency.

Key words: maxillary expansion, clear aligner treatment, cone-beam computed tomography

CLC Number: 

  • R783.5

TrendMD: 

Fig 1

Measurement of crown and root lengths of maxillary first molars using Invivo"

Fig 2

Model alignment and measurements using Geomagic Wrap 2021"

Tab 1

Baseline data on clinical characteristics"

临床特征（x±s）/n
年龄/岁27.02±6.88
性别
男10
女44
治疗时间/月24.97±9.79
安氏分类
Ⅰ类28
Ⅱ类19
Ⅲ类7
颌间牵引
无牵引19
Ⅱ类牵引27
Ⅲ类牵引8
IPR/mm0.52±1.03
附件16牙
无附件17
水平矩形附件19
垂直矩形附件3
优化附件15
附件26牙
无附件17
水平矩形附件24
垂直矩形附件4
优化附件9
附件16、26牙
无附件12
16或26牙有附件13
16、26牙均有附件29
16牙牙冠长度/mm5.99±0.37
16牙牙根长度/mm13.19±1.31
26牙牙冠长度/mm5.93±0.38
26牙牙根长度/mm13.01±1.38
16牙冠根比0.46±0.05
26牙冠根比0.46±0.06
16牙设计转矩/（°）a0.43±3.82
16牙实际-设计转矩/（°）b-1.04±2.36
26牙设计转矩/（°）a-0.56±3.11
26牙实际-设计转矩/（°）b-0.54±2.99

Tab 2

Comparison of designed and actual expansion for different tooth position"

牙位数量设计扩弓量/mm实际扩弓量/mm扩弓实现率/%P值
13—23牙422.48±1.651.84±1.3772.48±15.65P<0.001
14—24牙493.08±1.262.50±1.2479.29±16.54P<0.001
15—25牙523.19±1.652.64±1.4282.65±14.74P<0.001
16—26牙542.67±1.512.09±1.3675.65±15.12P<0.001
17—27牙361.61±1.061.13±0.8370.18±18.92P<0.001

Fig 3

Comparison of the amount of arch expansion and efficiency of arch expansion at different tooth positions"

Tab 3

One-way linear analysis of the efficiency of arch expansion of maxillary first molars"

测量项目扩弓实现率/%P值β95%置信区间
年龄/岁0.013-0.74-1.30~-0.18
治疗时间/月0.8890.03-0.39~0.45
上颌IPR/mm0.382-1.79-5.76~2.18
16牙牙冠长度/mm0.3075.77-5.20~16.74
16牙牙根长度/mm<0.001-7.18-9.63~-4.74
26牙牙冠长度/mm0.2186.79-3.89~17.47
26牙牙根长度/mm<0.001-6.86-9.18~-4.54
16牙冠根比<0.001194.80130.65~258.95
26牙冠根比<0.001158.19101.27~215.11
16—26牙设计扩弓量/mm0.0253.060.47~5.65
16牙设计转矩/（°）0.2970.57-0.49~1.64
16牙实际-设计转矩/（°）<0.0014.272.98~5.57
26牙设计转矩/（°）0.2050.85-0.45~2.15
26牙实际-设计转矩/（°）<0.0013.622.66~4.58
性别
男69.12±14.95参照
女77.14±14.930.1318.02-2.23~18.27
安氏分类
Ⅰ类76.06±15.62参照
Ⅱ类74.38±16.130.715-1.68-10.64~7.28
Ⅲ类77.45±15.120.8321.39-11.35~14.12
牵引
无牵引75.85±15.35参照
Ⅱ类牵引75.27±16.580.900-0.58-9.63~8.46
Ⅲ类牵引76.47±10.100.9250.61-12.11~13.34
附件16牙
无附件62.95±13.35参照
水平矩形附件82.75±22.79<0.00119.8011.57~28.02
垂直矩形附件86.58±5.360.00423.638.20~39.06
优化附件78.87±13.34<0.00115.927.19~24.65
附件26牙
无附件64.62±14.18参照
水平矩形附件85.55±9.19<0.00120.9313.74~28.13
垂直矩形附件83.59±11.950.00518.986.37~31.58
优化附件66.57±11.800.6841.95-7.40~11.30
附件16、26牙
无附件62.95±13.88参照
单侧附件68.73±13.590.2405.78-3.75~15.32
双侧附件84.01±15.12<0.00121.0612.88~29.24

Tab 4

Stepwise multifactorial linear analysis of arch expansion efficiency of maxillary first molars"

测量项目P值β95%置信区间
16牙冠根比0.04758.152.26~114.05
26牙冠根比0.02456.899.32~104.46
16牙实际-设计转矩/（°）0.0291.32-19.30~-8.69
26牙实际-设计转矩/（°）0.0431.1211.51~24.43
附件26牙
无附件参照
水平矩形附件0.2363.89-2.45~10.24
垂直矩形附件0.2265.58-3.33~14.48
优化附件0.099-5.86-12.68~0.95
附件16、26牙
无附件参照
单侧附件0.6721.55-5.58~8.68
双侧附件0.0706.61-0.35~13.58
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