下颌第三磨牙生长及萌出情况与下颌牙列拥挤度的相关性研究

doi:10.13591/j.cnki.kqyx.2025.11.002

Abstract

Abstract:

Objective To explore the association between the growth condition of mandibular third molars(M3) and the parameters of mandibular dental arch through a retrospective cross-sectional study on M3 in adults, and to provide a basis for the selection of clinical treatment of M3. Methods A total of 221 adult patients were randomly selected for our study. Dolphin software was used to analyze the CBCT of all the patients. Parameters of the mandibular dentition including the entire dental crowding(EDC) were recorded. Then the association between M3 growth condition and these parameters was analyzed. Results The mesio-impacted angle of M3 was positively correlated with EDC(P<0.05), and negatively correlated with the retromolar space(RMS, P<0.01). It was worth noting that median mesio-impacted M3 significantly increased EDC(P<0.01), and the erupting M3 in the vertical orthotopic position significantly increased RMS(P<0.01). Conclusion For patients with median mesio-impacted M3 or insufficient RMS, preventive removal of M3 may be considered clinically, which may help to reduce crowding and prevent relapse after orthodontic treatment.

Key words: mandibular third molar, dental crowding, CBCT, orthodontic treatment

CLC Number:

R783.5

WANG Yuting, HU Min, FAN Wei, GU Qihui, WANG Zhendong, ZHU Linlin. Study on the correlation between the growth and eruption of the mandibular third molar and the crowding of the mandibular dentition[J]. Stomatology, 2025, 45(11): 808-813.

Figures/Tables 6

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References 21

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基本情况		病例量	百分比(%)
性别	女	140	63.35
	男	81	36.65
分组	对照组(S0V0)	54	24.43
	垂直高位阻生(S1V1)	29	13.12
	垂直中位阻生(S1V2)	4	1.81
	垂直低位阻生(S1V3)	2	0.90
	近中高位阻生(S2V1)	6	2.71
	近中中位阻生(S2V2)	42	19.00
	近中低位阻生(S2V3)	47	21.27
	水平高位阻生(S3V1)	6	2.71
	水平中位阻生(S3V2)	6	2.71
	水平低位阻生(S3V3)	25	11.31
安氏分类	Ⅰ	100	45.25
	Ⅱ	91	41.18
	Ⅲ	30	13.57
垂直面型	低角	30	13.57
	均角	130	58.82
	高角	61	27.60
合计		221	100

测量项目	定义
下颌第三磨牙存在与否	双侧均无M3归为对照组(S0V0),双侧均有M3且生长情况对称归为研究组。
下颌第三磨牙倾斜角(M3-M2)	测量M3牙长轴与下颌第二磨牙(M2)牙长轴之间的成角,0°~15°归为垂直组(S1),16°~75°归为近中组(S2),76°~90°归为水平组(S3)。
下颌第三磨牙高度	记录M3与M2接触点的位置,以最高点为准,接触点位于M2釉牙骨质界上方1 mm以上的归为高位组(V1),位于M2釉牙骨质界上下1 mm范围内的归为中位组(V2),位于M2釉牙骨质界下方1 mm以下的归为低位组(V3)。
下颌全牙列拥挤度 (EDC)	逐个测量下颌牙齿宽度并相加,得出牙弓应有长度;连接双侧M2牙冠远中面最凸点(L7D点)并沿下颌牙槽嵴顶作弧线,测出牙弓现有长度,计算并记录牙弓应有长度和牙弓现有长度之差。
下颌磨牙后间隙(RMS)	连接双侧下颌第一磨牙近中颊尖(M1)与下颌中切牙近中切角(L1)作下颌𬌗平面(OP),该平面与下颌升支前缘相交所形成的点,测量该点与L7D点之间的距离。
下颌牙弓长度	连接双侧L7D点形成一条线,自下颌牙弓前段最突点向该线作垂线,测量该长度。
下颌牙弓宽度	连接双侧下颌尖牙牙尖,记录为33—43间宽度;连接双侧下颌第一恒磨牙近中颊尖,记录为36—46间宽度;连接双侧下颌第二恒磨牙近中颊尖,记录为37—47间宽度。
前牙覆盖	上颌中切牙舌侧面至下颌中切牙唇侧面之间的距离。
Spee曲线深度	连接M2远中颊尖与L1作一条直线,测量该直线到Spee曲线最低点之间的距离,测量双侧取平均值。

测量项目	分组					F	P
测量项目	对照组(n=54)	S1V1(n=29)	S2V2(n=42)	S2V3(n=47)	S3V3(n=25)	F	P
下颌全牙列拥挤度	1.65±1.42	1.97±1.66	4.31±2.41	2.09±2.04	2.48±1.71	13.54	0.00^**
下颌磨牙后间隙	9.47±1.48	12.84±1.75	10.30±1.98	9.60±1.60	9.37±1.61	23.48	0.00^**
牙弓长度	44.35±2.65	44.74±4.27	44.35±2.84	45.40±3.25	44.73±1.74	0.95	0.44
33—43间宽度	26.91±2.31	27.35±1.98	27.08±2.36	27.56±2.27	27.13±2.89	0.55	0.70
36—46间宽度	46.24±3.50	46.32±3.22	45.09±3.93	46.07±4.06	47.00±3.86	1.16	0.33
37—47间宽度	52.37±3.97	51.46±4.92	51.81±3.79	52.45±4.25	52.86±4.22	0.54	0.71
前牙覆盖	4.05±1.89	2.65±1.88	4.60±7.51	4.05±2.10	4.07±2.22	1.12	0.35
Spee曲线深度	1.57±0.47	1.27±0.58	1.51±0.56	1.34±0.65	1.32±0.59	2.20	0.07

与M3-M2的相关性	下颌全牙列拥挤度	下颌磨牙后间隙	牙弓长度	33—43间宽度	36—46间宽度	37—47间宽度	前牙覆盖	Spee曲线深度
r	0.21^**	-0.41^**	0.00	-0.06	0.01	0.12	0.06	0.00
P	0.01	0.00	0.96	0.42	0.91	0.11	0.45	1.00

Study on the correlation between the growth and eruption of the mandibular third molar and the crowding of the mandibular dentition

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