Department of Biomaterials, Max-Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany.
Dent Mater. 2010 Jan;26(1):e1-10. doi: 10.1016/j.dental.2009.09.007.
Tubules dominate the microstructure of dentin, and in crowns of human teeth they are surrounded by thick mineralized peritubular cuffs of high stiffness. Here we examine the three-dimensional (3D) arrangement of tubules in relation to enamel on the buccal and lingual aspects of intact premolars and molars. Specifically we investigate the angular orientation of tubules relative to the plane of the junction of dentin with enamel (DEJ) by means of wet, non-destructive and high-resolution phase-contrast (coherent) tomography.
Enamel capped dentin samples (n=16), cut from the buccal and lingual surfaces of upper and lower premolar and molar teeth, were imaged in water by high-resolution synchrotron-based phase-contrast X-ray radiography. Reconstructed 3D virtual images were co-aligned with respect to the DEJ plane. The average tubule orientation was determined at increasing distances from the DEJ, based on integrated projections onto orthogonal virtual planes. The angle and curl of the tubules were determined every 100 microm to a depth of 1.4mm beneath the DEJ.
Most tubules do not extend at right angles from the DEJ. Even when they do, tubules always change their orientations substantially within the first half-millimeter zone beneath the DEJ, both on the buccal and lingual aspects of premolar and molar teeth. Tubules also tend to curl and twist within this zone. Student t-tests indicate that lower teeth seem to have greater tilts in the tubule orientations relative to the DEJ normal with an average angle of 42 degrees (+/-2.0 degrees), whereas upper teeth exhibit a smaller change of orientation, with an average of 32 degrees (+/-2.1 degrees).
Tubules are a central characteristic of dentin, with important implications on how it is arranged and what the properties are. Knowing about the path that tubules follow is important for various reasons, ranging form improving control over restorative procedures to understanding or simulating the mechanical properties of teeth. At increasing depths of dentin beneath enamel, tubules are significantly tilted relative to the DEJ norm, which may be important to understand clinical challenges such as sensitivity, effectiveness of bonding techniques or prediction of possible paths for bacterial invasion. Our data show dissimilar average tubule angles of upper versus lower teeth with respect to the DEJ which presumably contributes to different shear responses of the tissue under function. The degree to which this may warrant improved restoratives or new adhesive techniques to enhance adhesive restorations merits further investigation.
牙本质的微观结构主要由小管组成，在人类牙齿的牙冠中，它们被高硬度的厚矿化管周鞘所包围。在这里，我们研究了完整前磨牙和磨牙颊舌面牙本质与釉质交界处（DEJ）小管的三维（3D）排列情况。具体来说，我们通过湿、无损和高分辨率相衬（相干）层析成像技术，研究了小管相对于牙本质与釉质交界处平面（DEJ）的角向方位。
从上颌和下颌前磨牙和磨牙的颊舌面切取牙本质覆盖釉质的样本（n=16），在水中通过高分辨率同步辐射相衬 X 射线射线照相进行成像。根据正交虚拟平面的积分投影，将重建的 3D 虚拟图像与 DEJ 平面对齐。基于在 DEJ 下方 1.4mm 深度内的正交虚拟平面上的积分投影，确定距离 DEJ 增加时的平均小管取向。确定了从 DEJ 以 100 微米的间隔到 1.4 毫米深度的小管的角度和卷曲度。
大多数小管不是从 DEJ 垂直延伸的。即使它们是垂直的，小管在 DEJ 下方的前半毫米区域内，在上下前磨牙和磨牙的颊舌面都始终会发生很大的取向变化。小管也倾向于在该区域卷曲和扭曲。学生 t 检验表明，下牙的小管取向相对于 DEJ 法线的倾斜度似乎更大，平均角度为 42 度（+/-2.0 度），而上牙的取向变化较小，平均为 32 度（+/-2.1 度）。
小管是牙本质的一个主要特征，对其排列方式和性质有重要影响。了解小管的路径对于各种原因都很重要，从改善对修复程序的控制到理解或模拟牙齿的机械性能。在牙本质深度增加到釉质下方时，小管相对于 DEJ 法线显著倾斜，这对于理解敏感性、粘结技术的有效性或预测可能的细菌入侵路径等临床挑战可能很重要。我们的数据显示，上下牙相对于 DEJ 的平均小管角度存在明显差异，这可能导致组织在功能下的剪切响应不同。这在多大程度上需要改进修复体或新的粘结技术来增强粘结修复体，值得进一步研究。
