Stomatological Hospital of Chongqing Medical University, Chongqing, China.
Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing, China.
BMC Oral Health. 2023 Mar 10;23(1):138. doi: 10.1186/s12903-023-02843-0.
The anatomical position of the mandibular third molars (M3s) is located in the distal-most portions of the molar area. In some previous literature, researchers evaluated the relationship between retromolar space (RS) and different classifications of M3 in three‑dimensional (3D) cone-beam computed tomography (CBCT).
Two hundred six M3s from 103 patients were included. M3s were grouped according to four classification criteria: PG-A/B/C, PG-I/II/III, mesiodistal angle and buccolingual angle. 3D hard tissue models were reconstructed by CBCT digital imaging. RS was measured respectively by utilizing the fitting WALA ridge plane (WP) which was fitted by the least square method and the occlusal plane (OP) as reference planes. SPSS (version 26) was used to analyze the data.
In all criteria evaluated, RS decreased steadily from the crown to the root (P < 0.05), the minimum was at the root tip. From PG-A classification, PG-B classification to PG-C classification and from PG-I classification, PG-II classification to PG-III classification, RS both appeared a diminishing tendency (P < 0.05). As the degree of mesial tilt decreased, RS appeared an increasing trend (P < 0.05). RS in classification criteria of buccolingual angle had no statistical difference (P > 0.05).
RS was associated with positional classifications of the M3. In the clinic, RS can be evaluated by watching the Pell&Gregory classification and mesial angle of M3.
下颌第三磨牙（M3）的解剖位置位于磨牙区的最远端。在之前的一些文献中，研究人员在三维（3D）锥形束 CT（CBCT）中评估了磨牙后间隙（RS）与 M3 不同分类之间的关系。
纳入 103 名患者的 206 颗 M3。根据 4 种分类标准（PG-A/B/C、PG-I/II/III、近远中角和颊舌向角）对 M3 进行分组。通过 CBCT 数字成像重建 3D 硬组织模型。分别利用最小二乘法拟合的适配 WALA 嵴平面（WP）和咬合平面（OP）作为参考平面测量 RS。采用 SPSS（版本 26）分析数据。
在所评估的所有标准中，RS 从牙冠到牙根逐渐减小（P<0.05），最小值位于根尖。从 PG-A 分类、PG-B 分类到 PG-C 分类，以及从 PG-I 分类、PG-II 分类到 PG-III 分类，RS 均呈现减小趋势（P<0.05）。随着近中倾斜度的减小，RS 呈增大趋势（P<0.05）。颊舌向角分类标准中的 RS 无统计学差异（P>0.05）。
RS 与 M3 的位置分类有关。在临床中，可以通过观察 M3 的 Pell&Gregory 分类和近中角度来评估 RS。
