Guo Xueqiang, Gao Yang, Zhang Fan, Wang Meng, Tian Xia, Huang Qing, Liu Xinqiang
Department of Stomatology, Qingdao Women and Children's Hospital, Qingdao University, Tongfu Road No.6, Qingdao, 266000, People's Republic of China.
Department of Orthodontics, The Affiliated Hospital of Qingdao University, Jiangsu Road No.16, Qingdao, 266003, People's Republic of China.
Clin Oral Investig. 2023 Feb;27(2):671-680. doi: 10.1007/s00784-022-04782-6. Epub 2022 Nov 14.
The aim of this study was to compare the difference in length and width of the mandibular retromolar space (RMS) stratified by the different eruption and impaction statuses of the third molars in patients with skeletal Class I malocclusion.
The right mandibular RMS in 186 adult patients categorized according to the different statuses of the third molar was analyzed by using cone-beam computed tomography (CBCT). The shortest distances between the inner lingual cortex of the mandibular body and second molar root were measured parallel to the posterior occlusal line (POL) at depths of 2, 4, 6, 8, and 10 mm (mandibular retromolar space length in root level, RL) on the axial slices with the cementoenamel junction (CEJ) as the reference level. The width of the RMS and second molar root was measured vertical to the POL at the terminal point of the molar distalization at depths of 2, 4, 6, 8, and 10 mm (width of the mandibular retromolar space, BW/ width of the second molar distal root, TW) from the CEJ.
RL in different measurement planes was 2.72 ± 2.22 ~ 3.74 ± 2.26 for Group A, 5.27 ± 1.68 ~ 9.10 ± 2.04 for Group B, 1.94 ± 2.34 ~ 5.71 ± 4.37 for Group C, 1.83 ± 2.95 ~ 5.05 ± 4.24 for Group D, and 5.93 ± 3.97 ~ 10.52 ± 2.16 for Group E. The BW measurement results for A ~ E group were 9.71 ± 1.41 ~ 10.51 ± 1.81, 9.83 ± 1.39 ~ 12.55 ± 2.11, 9.96 ± 1.21 ~ 12.17 ± 1.62, 9.82 ± 1.47 ~ 12.28 ± 2.77, and 10.02 ± 1.20 ~ 12.75 ± 0.82, respectively. There was no significant difference between men and women in any measurements (P > 0.05). Patients with normal third molars erupted and those vertically impacted possessed larger RMS lengths than those in which the third molars were missing, horizontally impacted or mesially impacted (P < 0.05). In each measurement plane, TW was significantly smaller than BW (P < 0.05).
Sex had no effect on the length or width of the mandibular RMS. Different statuses of third molars can also differentially affect the mandibular RMS. The mandibular RMS width is not a limit for mandibular molar distalization.
When considering the distalization of mandibular molars, more attention should be directed to the lingual cortex of the mandible, and CBCT scans are recommended for patients who require significant mandibular molar distalization. The mandible buccal shelf and retromolar area maybe a safe zone to insert the miniscrew for molar distalization.
本研究旨在比较骨骼Ⅰ类错牙合患者中，根据第三磨牙不同萌出和阻生状态分层的下颌磨牙后间隙（RMS）的长度和宽度差异。
使用锥形束计算机断层扫描（CBCT）分析186例成年患者根据第三磨牙不同状态分类的右侧下颌RMS。在下颌体舌侧皮质与第二磨牙牙根之间的最短距离，在以牙骨质釉质界（CEJ）为参考水平的轴向切片上，于2、4、6、8和10mm深度处平行于后牙合线（POL）进行测量（牙根水平的下颌磨牙后间隙长度，RL）。RMS和第二磨牙牙根的宽度在距CEJ 2、4、6、8和10mm深度处（下颌磨牙后间隙宽度，BW/第二磨牙远中牙根宽度，TW）于磨牙远移终点处垂直于POL进行测量。
A组在不同测量平面的RL为2.72±2.22至3.74±2.26，B组为5.27±1.68至9.10±2.04，C组为1.94±2.34至5.71±4.37，D组为1.83±2.95至5.05±4.24，E组为5.93±3.97至10.52±2.16。A至E组的BW测量结果分别为9.71±1.41至10.51±1.81、9.83±1.39至12.55±2.11、9.96±1.21至12.17±1.62、9.82±1.47至12.28±2.77和10.02±1.20至12.75±0.82。在任何测量中，男性和女性之间均无显著差异（P>0.05）。第三磨牙正常萌出和垂直阻生的患者比第三磨牙缺失、水平阻生或近中阻生的患者具有更大的RMS长度（P<0.05）。在每个测量平面中，TW均显著小于BW（P<0.05）。
性别对下颌RMS的长度或宽度无影响。第三磨牙的不同状态也可不同程度地影响下颌RMS。下颌RMS宽度不是下颌磨牙远移的限制因素。
在考虑下颌磨牙远移时，应更多关注下颌舌侧皮质，对于需要显著下颌磨牙远移的患者建议进行CBCT扫描。下颌颊侧牙槽嵴和磨牙后区可能是插入微型螺钉进行磨牙远移的安全区。
