Study on the effect of chin morphology on orthodontic treatment

doi:10.7518/hxkq.2023.2022508

Abstract

Abstract:

Objective To investigate the effect of different soft-tissue morphologies on the treatment of skeletal class Ⅰ malocclusion patients by analyzing measurement data before and after treatment. Methods Pre- and post-treatment lateral cephalograms of 55 adult female Angle class Ⅰ patients were collected in the Department of Orthodontics, Hospital of Stomatology, Jilin University from January 2012 to December 2020. Chin soft-tissue morphologies in the lateral cranial radiographs were used to divide the patients into an abnormal chin morphology group (flat and retracted chins, n=27) and a normal chin morphology group (rounded and prominent chins, n=28). Relevant soft- and hard-tissue indexes were selected to study in-group varieties and intergroup differences in the varying chin morphologies before and after treatment. Results The chin-lip angle, mandibular chin angle, mandibular chin vertex angle, PP-MP, LL-E, UL-E, Po-Pos, and B-B’ thickness in the abnormal chin morphology group were significantly higher than those in the normal chin morphology group (P<0.05). Furthermore, m∶BMe and n∶B’Mes in the abnormal chin morphology group were signi-ficantly lower than those in the normal chin morphology group (P<0.05). After treatment, the mandibular chin angle, mandibular chin vertex angle, U1-SN, L1-MP, LL-E, UL-E, SNA, SNB, and B-B’ thickness of the abnormal chin morphology group significantly decreased (P<0.05), whereas the nasolabial angle, m∶BMe, n∶B’ Mes, and Po-Pos significantly increased (P<0.05). In the normal chin morphology group, the U1-SN, L1-MP, LL-E, UL-E, and B-B’ thicknesses decreased significantly (P<0.05), whereas the nasolabial angle significantly increased (P<0.05). Among them, m∶BMe and n∶B’ Mes were positively correlated. Conclusion Chin morphology affects the formulation of treatment plans. Compared with the normal chin morphology group, the abnormal chin morphology group required a larger retraction of incisors. Although the chin of soft-tissue morphology is related to the morphology of bones, the changes in soft tissue chin after treatment cannot be directly predicted according to the bone changes. Soft-tissue chin morphology affects the aesthetic assessment of the soft-tissue lateral profile and the change in soft tissue before and after treatment. The method of predicting the change in soft-tissue chin after treatment should consider the morphology of the soft-tissue chin.

Key words: chin morphology, soft tissue profile, Angle classⅠ

CLC Number:

R 783.5

Fu Yu, Li Ziwei, Zhao Menghan, Shi Ruixin.. Study on the effect of chin morphology on orthodontic treatment[J]. West China Journal of Stomatology, 2023, 41(4): 443-449.

Figures/Tables 5

Fig 1

Fig 2

Tab 1

Comparison of angle and chin indexes before and after treatment of abnormal chin morphology group and normal chin morphology group

测量指标	异常颏组		正常颏组		P值
测量指标	①矫治前	②矫治后	③矫治前	④矫治后	①和②	③和④	①和③	②和④
鼻唇角/°	95.24±8.86	101.74±8.74	93.70±8.90	102.63±8.63	0.000*	0.000*	0.525	0.707
颏唇沟角/°	141.28±14.71	140.14±12.41	130.84±12.01	133.23±11.68	0.604	0.098	0.006*	0.038*
下颌颏角/°	142.75±8.60	133.24±8.59	127.19±6.17	125.29±6.91	0.000*	0.071	0.000*	0.000*
下颏顶角/°	150.55±7.22	143.27±6.63	142.07±5.35	141.81±5.83	0.000*	0.792	0.000*	0.391
m∶BMe	0.19±0.04	0.20±0.03	0.21±0.03	0.21±0.03	0.041*	0.161	0.023*	0.043*
PP-MP/°	28.66±5.20	29.23±4.84	24.61±5.11	24.86±5.84	0.064	0.438	0.005*	0.004*
MP-SN/°	33.60±5.41	32.79±5.94	31.21±5.38	31.13±5.60	0.334	0.760	0.107	0.306
L1-MP/°	103.40±6.82	94.94±6.80	102.27±7.54	95.27±7.64	0.000*	0.000*	0.563	0.866
UL-E距/mm	2.00±1.90	-0.02±1.60	0.64±1.85	-1.22±1.69	0.000*	0.000*	0.010*	0.009*
SNA/°	82.54±4.00	81.69±3.98	82.93±4.16	82.37±3.68	0.003*	0.065	0.727	0.515
SNB/°	78.68±3.99	78.17±3.84	79.55±3.71	79.16±3.59	0.015*	0.075	0.406	0.325
Po-Pos/mm	12.72±1.75	13.54±2.40	12.29±1.80	11.92±2.18	0.044*	0.089	0.033*	0.143
n∶B’Mes	0.17（0.15，0.20）	0.21（0.20，0.25）	0.23（0.22，0.27）	0.25（0.23，0.27）	0.000*	0.050	0.000*	0.007*
U1-SN/°	115.95（108.80，119.80）	101.95（93.85，107.45）	116.58（109.68，122.53）	102.83（96.11，106.03）	0.000*	0.000*	0.405	0.649
LL-E距/mm	5.35（4.70，6.30）	1.75（0.40，2.25）	2.98（1.60，4.61）	0.15（-1.68，1.40）	0.000*	0.000*	0.000*	0.001*
ANB/°	4.05（2.45，5.00）	3.60（2.15，5.35）	3.93（2.04，4.48）	3.73（1.85，4.19）	0.153	0.493	0.266	0.424
B-B’厚度/mm	13.31（12.76，16.46）	12.05（10.92，13.62）	12.10（11.07，12.69）	10.90（9.93，12.38）	0.000*	0.016*	0.000*	0.023*
Gn-Gns厚度/mm	8.61（7.50，9.36）	8.38（7.46，9.37）	8.92（8.17，9.59）	9.12（8.30，9.70）	0.904	0.665	0.289	0.074
Me-Mes厚度/mm	6.48（5.29，7.44）	6.59（5.48，7.61）	6.89（6.40，8.09）	7.63（6.39，8.18）	0.564	0.387	0.064	0.030*

Tab 1

Tab 2

Tab 3

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测量指标	异常颏组	正常颏组	P值
鼻唇角/°	6.51±5.09	8.92±7.56	0.172
颏唇沟角/°	-1.14±11.30	2.39±7.38	0.174
下颌颏角/°	-9.51±7.82	-1.89±5.33	0.000*
下颏顶角/°	-7.28±6.69	-0.26±5.21	0.000*
m∶BMe	0.01±0.03	0.01±0.03	0.162
PP-MP/°	0.57±1.53	0.24±1.63	0.445
U1-SN/°	-14.09±5.14	-14.33±5.87	0.876
L1-MP/°	-8.46±5.67	-7.01±5.83	0.351
UL-E距/mm	-2.02±1.04	-1.86±1.17	0.594
SNA/°	-0.85±1.37	-0.56±1.54	0.462
SNB/°	-0.51±1.01	-0.38±1.10	0.662
ANB/°	-0.34±1.07	-0.17±1.11	0.575
B-B’厚度/mm	-2.02±1.87	-0.66±1.32	0.003*
Gn-Gns厚度/mm	0.07±1.39	0.11±1.06	0.905
Me-Mes厚度/mm	1.44±1.47	0.52±1.49	0.024*
MP-SN/°	0.35（-0.20，1.40）	-0.23（-1.44，1.18）	0.083
LL-E距/mm	-3.90（-4.80，-3.05）	-3.23（-3.90，-2.28）	0.024*
Po-Pos/mm	0.85（-0.65，2.75）	-0.50（-1.00，0.49）	0.006*
n∶B’Mes	0.047（0.029，0.070）	0.010（-0.008，0.036）	0.000*

变量1	变量2	r值	P值
n∶B’Mes	m∶BMe	0.707	0.000*
n∶B’Mes变化量	m∶BMe变化量	0.068	0.621

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