Jiangsu Province Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, 210029, China.
The Affiliated Stomatological Hospital of Soochow University, Suzhou Stomatological Hospital, Suzhou, 215000, China.
BMC Oral Health. 2023 Nov 25;23(1):928. doi: 10.1186/s12903-023-03641-4.
Trans- inferior alveolar nerve (IAN) implantation technique was wildly used while the potential appropriate angle range in which the residual alveolar bone can bear the stress without absorption are currently unclear. This study aimed to evaluate the stress distribution pattern of the interface between bone and implant by finite element analysis (FEA) to determine the appropriate range of the implant tilt angle.
Cone beam computed tomography (CBCT) images of 120 patients with missing mandibular second molars and vertical bone height < 9 mm in the edentulous area were selected. The distances from the mandibular nerve canal to the buccal cortex, the lingual cortex and the alveolar ridge crest were measured by using a combination of software. The angular ranges of the buccal-lingual inclination of simulated trans-IAN implants were measured and three-dimensional finite element models were constructed in the mandibular second molar area according to the differences of the inclination angles. A vertical load (200N) was then applied to analyze the biomechanical conditions of the implant-bone interface during median occlusion.
The distance at the second molar from the nerve canal to the buccal cortex, lingual cortex and alveolar crest were 6.861 ± 1.194 mm, 2.843 ± 0.933 mm and 7.944 ± 0.77 mm. Trans-IAN implantation was feasible in 73.33% of patients. The minimum angle and maximum angles of the buccal-lingual inclination of the simulated implant were 19.135 ± 6.721° and 39.282 ± 6.581°. When a vertical static load of 200N was applied, the tensile stress in cortical bone gradually increased with the increase of the implant tilt angle. When the inclination angle reached 30°, the tensile stress (105.9 MPa) exceeded the yield strength (104 MPa) of cortical bone. Compared with the conventional implants, the stress peak value of the vertical ultra-short implant in cortical bone was greater than the stress peak value of the conventional implants at 10°(79.81 MPa) and 20°(82.83 MPa) and was smaller than the stress of the implant at 30°(105.9 MPa) and 40°(107.8 MPa). Therefore, when the bone mass allows, conventional-length implants should be selected whenever possible, and an operative range of the trans-IAN implantation in the mandibular second molar could be retained with an inclination angle of < 30°.
The mandibular nerve canal at the mandibular second molar was obviously biased to the lingual side, which ensured sufficient bone mass at the buccal side. In most patients with severe mandibular atrophy, it was possible to maintain a safe distance from the nerve canal with conventional-length implants via the trans-IAN implantation technique.
在下颌神经（IAN）移植技术中，广泛应用了 Trans- IAN 植入技术，但是目前还不清楚剩余牙槽骨在不吸收的情况下能够承受多大的应力。本研究旨在通过有限元分析（FEA）评估骨与植入物界面的应力分布模式，以确定植入物倾斜角度的适当范围。
选取 120 名下颌第二磨牙缺失且无牙区垂直骨高度<9mm 的患者的锥形束 CT（CBCT）图像。使用软件组合测量下颌神经管到颊侧皮质、舌侧皮质和牙槽嵴顶的距离。测量模拟 Trans-IAN 植入物颊舌倾斜角度的角度范围，并根据倾斜角度的差异在第二磨牙区域构建三维有限元模型。然后施加一个垂直负载（200N），分析正中咬合时植入物-骨界面的生物力学条件。
从神经管到第二磨牙颊侧皮质、舌侧皮质和牙槽嵴顶的距离分别为 6.861±1.194mm、2.843±0.933mm 和 7.944±0.77mm。73.33%的患者可进行 Trans-IAN 植入。模拟植入物颊舌倾斜的最小角度和最大角度分别为 19.135±6.721°和 39.282±6.581°。当施加 200N 的垂直静态载荷时，皮质骨中的拉伸应力随植入物倾斜角度的增加而逐渐增加。当倾斜角度达到 30°时，拉伸应力（105.9MPa）超过皮质骨的屈服强度（104MPa）。与常规植入物相比，在 10°（79.81MPa）和 20°（82.83MPa）时，垂直超短植入物在皮质骨中的峰值应力大于常规植入物的峰值应力，而在 30°（105.9MPa）和 40°（107.8MPa）时，植入物的峰值应力较小。因此，在骨量允许的情况下，应尽可能选择常规长度的植入物，并且可以保留下颌第二磨牙的 Trans-IAN 植入术的手术范围，倾斜角度<30°。
下颌第二磨牙的下颌神经管明显偏向舌侧，这确保了颊侧有足够的骨量。在大多数严重下颌萎缩的患者中，通过 Trans-IAN 植入技术，使用常规长度的植入物可以保持与神经管的安全距离。
