Objective: To investigate the clinical application effect of the along-axis extraction method in the extraction of impacted mandibular third molars (IMTM) and to compare the biomechanical characteristics of different root extraction techniques through three-dimensional finite element analysis.
Methods: A total of 68 patients requiring IMTM extraction were enrolled and randomly divided into two groups: the experimental group underwent the along-axis extraction method, while the control group underwent the traditional buccal bone removal and root extraction method. The duration of the procedure, intraoperative and postoperative complications were recorded. Three-dimensional finite element analysis further revealed the stress distribution in the tooth root, jawbone, periodontal ligament, and mandibular canal during different root extraction methods.
Results: The duration of root extraction, pain score and swelling on the first postoperative day in the control group were (7.87±3.90) min, 4.62±1.90 and (11.37±5.12) mm, respectively, which were significantly higher than those in the experimental group [(5.74±2.37) min, 3.87±1.19 and (7.22±3.39) mm, respectively]. The root fracture rate and lingual bone plate fracture rate in the control group were significantly higher than those in the experimental group (P < 0.05). The results of finite element analysis showed that the control group ' s lingual al-veolar bone had the higher peak equivalent stress, and lingual bone plate fracture was prone to occur. The periodontal ligament of the experimental group had the higher equivalent stress value, making it more likely to rip and more likely to cause root displacement. When subjected to force, the experimental group' s instantaneous root displacement was higher, but the control group ' s root displacement was more pronounced in the lingual direction.
Conclusion: This study suggests that the along-axis extraction me-thod can not only effectively shorten the operative time but also reduce postoperative complications after extraction of impacted mandibular third molars, and enhance the safety of the operation and the patient' s comfort. Three-dimensional finite element analysis shows the biomechanical characteristics of various root extraction techniques visually, serves as a valuable guide for choosing and refining clinical surgical techniques, and confirms that extracting a tooth' s root along its long axis yields better clinical results.
目的: 探讨顺牙根长轴拔牙法在下颌阻生第三磨牙拔除术中的临床应用效果，并通过三维有限元分析比较不同方法的生物力学特性。
方法: 纳入68例患者，随机分为两组，试验组采用顺牙长轴取根法，对照组采用传统颊侧去骨后取根法，统计取根手术时长、术中及术后并发症情况。通过构建不同取根方法的三维有限元模型，模拟并分析取根过程中牙根、颌骨、牙周膜及下颌管的受力情况。
结果: 对照组的手术取根时长、术后第1天的疼痛评分和术后肿胀度分别为(7.87±3.90) min、(4.62±1.90)分和(11.37±5.12) mm，均显著高于试验组的(5.74±2.37) min、(3.87±1.19)分和(7.22±3.39) mm；对照组的术中牙根折断率和舌侧骨板骨折率也均显著高于试验组。有限元分析结果显示，对照组舌侧牙槽骨的等效应力峰值最高，易出现舌侧骨板骨折；试验组模型牙周膜的等效应力峰值最高，易出现牙周膜撕裂，有利于牙根脱位。牙根在受力时，试验组的牙根瞬时位移量高，而对照组的牙根朝向舌向移位趋势更明显。
结论: 顺牙根长轴取根法能有效减少下颌阻生第三磨牙拔除术的创伤，提高手术安全性和患者舒适度。三维有限元分析为不同取根方式下的生物力学特性提供了直观展示，为临床手术方法的选择和优化提供了重要参考，辅助验证了顺牙长轴拔牙法具有更佳的临床效果。
Keywords: Complications; Mandible; Molar, third; Tooth extraction; Tooth, impacted.