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短波红外 (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，可能会因牙髓管的闭塞和三级牙本质的形成而受到阻碍。到目前为止，还缺少术中直接可视化牙齿 3 维解剖结构的方法。在这里，我们评估了在逐步接入准备期间使用短波红外辐射（SWIR）进行导航的情况。九颗牙齿（3颗前牙、3颗前磨牙和3颗磨牙）从人体捐献者的上颌或下颌中整体移植，牙周组织包括牙槽骨和粘膜。分析分别在基线以及 5 毫米、7 毫米和 9 毫米的制备深度处进行。对于反射，从咬合方向使用波长为 1,550 nm 的 SWIR，而对于透照，则使用波长为 1,300 nm 的 SWIR 从颊侧和口腔侧的边缘牙龈处穿过每个样本。使用 SWIR 透照，牙髓结构可以在到达牙髓室之前被识别为约 2 毫米的较暗区域，尽管它们在正常情况下无法区分。磨牙分叉区域的强度高于根管区域。通过叠加分段微计算机断层扫描（μCT）图像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。通过层次聚类分析，这两个片段都可以得到确认并与特定的聚类相关联。计算 µCT 的局部厚度并与 SWIR 透照图像相关联，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了解牙髓可见度的关键因素。总之，短波红外透照可以在牙髓通路准备过程中实现直接的临床实时导航。