Endodontic access preparation is one of the initial steps in root canal treatments and can be hindered by the obliteration of pulp canals and formation of tertiary dentin. Until now, methods for direct intraoperative visualization of the 3-dimensional anatomy of teeth have been missing. Here, we evaluate the use of shortwave infrared radiation (SWIR) for navigation during stepwise access preparation. Nine teeth (3 anteriors, 3 premolars, and 3 molars) were explanted en bloc with intact periodontium including alveolar bone and mucosa from the upper or lower jaw of human body donors. Analysis was performed at baseline as well as at preparation depths of 5 mm, 7 mm, and 9 mm, respectively. For reflection, SWIR was used at a wavelength of 1,550 nm from the occlusal direction, whereas for transillumination, SWIR was passed through each sample at the marginal gingiva from the buccal as well as oral side at a wavelength of 1,300 nm. Pulpal structures could be identified as darker areas approximately 2 mm before reaching the pulp chamber using SWIR transillumination, although they were indistinguishable under normal circumstances. Furcation areas in molars appeared with higher intensity than areas with canals. The location of pulpal structures was confirmed by superimposition of segmented micro–computed tomography (µCT) images. By radiomic analysis, significant differences between pulpal and parapulpal areas could be detected in image features. With hierarchical cluster analysis, both segments could be confirmed and associated with specific clusters. The local thickness of µCTs was calculated and correlated with SWIR transillumination images, by which a linear dependency of thickness and intensity could be demonstrated. Lastly, by in silico simulations of light propagation, dentin tubules were shown to be a crucial factor for understanding the visibility of the pulp. In conclusion, SWIR transillumination may allow direct clinical live navigation during endodontic access preparation.

中文翻译：

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在牙髓通路准备中通过 SWIR 可视化牙髓结构


牙髓通路准备是根管治疗的初始步骤之一，可能会受到牙髓管闭塞和三级牙本质形成的阻碍。到目前为止，一直缺少对牙齿 3 维解剖结构进行术中直接可视化的方法。在这里，我们评估了在逐步进入准备期间使用短波红外辐射 （SWIR） 进行导航。9 颗牙齿 （3 颗前磨牙、3 颗前磨牙和 3 颗磨牙） 与完整的牙周组织一起从人体供体的上颌或下颌中移出，包括牙槽骨和粘膜。在基线以及制备深度分别为 5 mm、7 mm 和 9 mm 时进行分析。对于反射，SWIR 在距咬合方向 1,550 nm 的波长下使用，而对于透射，SWIR 以 1,300 nm 的波长从口腔和口腔侧穿过边缘牙龈的每个样品。使用 SWIR 透射照明，可以在到达牙髓室之前大约 2 mm 处将牙髓结构识别为较暗的区域，尽管它们在正常情况下无法区分。磨牙的分叉区域比有根管的区域更密集。通过分段显微计算机断层扫描 （μCT） 图像的叠加来确认牙髓结构的位置。通过放射组学分析，可以在图像特征中检测到牙髓和牙髓旁区域之间的显着差异。通过分层聚类分析，可以确认两个片段并将其与特定聚类相关联。计算 μCT 的局部厚度并与 SWIR 透射图像相关联，从而可以证明厚度和强度的线性依赖性。 最后，通过光传播的计算机模拟，牙本质小管被证明是理解牙髓可见性的关键因素。总之，SWIR 透射照明可能允许在牙髓通路准备期间直接进行临床实时导航。