Statement of problem

The anterior mandible has conventionally been deemed as a safe zone for dental implants. However, with the evolution of cone beam computed tomography (CBCT), several anatomic challenges have been identified that, if violated, can lead to surgical complications, including life-threatening hemorrhage.

Purpose

The purpose of this observational clinical study was to obtain standardized average values for the location of the sublingual artery (SLA), submental artery (SMA), and mandibular incisive canal (MIC) and to determine whether differences exist between dentate and edentulous individuals. In addition, the prevalence of these anatomic landmarks on CBCT images was determined. An additional objective was to study the cross-sectional morphology of the anterior mandible.

Material and methods

CBCT images of 125 edentulous and 100 dentate patients were studied at the anterior mandible for the prevalence of SLA, SMA, and MIC. Measurements of these 3 structures were then made from the inferior cortical border of the mandible to the superior border of each structure to obtain average anatomic measurements. The cross-sectional shapes of anterior mandibles were then categorized, and the prevalence of each shape in this sample was calculated.

Results

The prevalence of SLA across all 225 CBCT images was 100% for edentulous patients and 98% for dentate patients. The SLA was located approximately 15 mm above the inferior border of the mandible. The prevalence of SMA was 94% for edentulous patients and 88% for dentate patients. The SMA was located approximately 5 mm above the inferior border of the mandible. The prevalence of MIC was 61% for edentulous patients and 59% for dentate patients. The MIC was located approximately 11 mm above the inferior border of the mandible in edentulous patients and approximately 14 mm above the inferior border of the mandible in dentate patients. Five distinct shapes were observed for the cross-sectional morphology of the anterior mandible: hourglass (1%), pear (53%), sickle (4%), ovoid (26%), and triangular (17%). The distance from the crest of the residual ridge to a minimum 6-mm width in the anterior mandible was approximately 4 mm.

Conclusions

The SLA and SMA vascular structures were consistently identified in the anterior mandible on CBCT images, both in dentate and edentulous patients, whereas the mandibular incisive canal was not consistently visualized. Average values from the inferior border of the mandible to the SLA, SMA, and MIC were computable. The cross-sectional morphology of the anterior mandible is diverse in dentate and edentulous mandibles, with pear shaped being the most common in both. These findings should be taken into consideration when dental implants are planned in the anterior mandible.

中文翻译：

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使用锥形束计算机断层扫描分析下颌前部解剖：对 225 幅下颌图像的研究。

问题陈述

前颌骨通常被认为是种植牙的安全区域。然而，随着锥形束计算机断层扫描 (CBCT) 的发展，已经确定了一些解剖学挑战，如果违反这些挑战，可能会导致手术并发症，包括危及生命的出血。

目的

这项观察性临床研究的目的是获得舌下动脉 (SLA)、颏下动脉 (SMA) 和下颌切牙管 (MIC) 位置的标准化平均值，并确定有齿和无牙颌个体之间是否存在差异。此外，还确定了 CBCT 图像上这些解剖标志的普遍性。另一个目的是研究前颌骨的横截面形态。

材料与方法

在下颌前部研究了 125 名无牙颌和 100 名有齿患者的 CBCT 图像，以了解 SLA、SMA 和 MIC 的患病率。然后从下颌骨的下皮质边缘到每个结构的上边缘对这 3 个结构进行测量，以获得平均解剖测量值。然后对前颌骨的横截面形状进行分类，并计算该样本中每种形状的患病率。

结果

在所有 225 张 CBCT 图像中，无牙颌患者的 SLA 患病率为 100%，而有齿患者的 SLA 患病率为 98%。SLA 位于下颌骨下缘上方约 15 mm 处。无牙颌患者的 SMA 患病率为 94%，而有齿患者的 SMA 患病率为 88%。SMA 位于下颌骨下缘上方约 5 mm 处。无牙颌患者的 MIC 患病率为 61%，而有齿患者的 MIC 患病率为 59%。MIC 位于无牙颌患者下颌下缘上方约 11 mm 处，而齿状患者位于下颌下缘上方约 14 mm 处。前下颌骨的横截面形态观察到五种不同的形状：沙漏（1%）、梨形（53%）、镰刀形（4%）、卵形（26%）和三角形（17%）。

结论

在 CBCT 图像中，SLA 和 SMA 血管结构在有齿和无牙颌患者的前下颌骨中一致地被识别，而下颌切牙管未一致地可视化。从下颌骨下缘到 SLA、SMA 和 MIC 的平均值是可计算的。下颌前牙的横截面形态在有齿和无牙颌中是不同的，梨形是两者中最常见的。当计划在下颌前部种植牙时，应考虑这些发现。