Nonenzymatic glycation is a multistep, slow reaction between reducing sugars and free amino groups of long-lived proteins, which affects the structural and mechanical properties of collagen-rich tissues via accumulation of advanced glycation end products (AGEs). Dental collagen is exposed to glycation as part of the natural aging process. However, in case of chronically high blood glucose, the process can be accelerated, resulting in premature stiffening of dentin, leading to tooth fragility. The molecular mechanisms whereby collagen glycation evokes the loss of mechanical stability in teeth are currently unknown. In this study, we used 2-photon and atomic force microscopies to correlate structural and mechanical changes in dental collagen induced by in vitro glycation. Young tooth samples were demineralized and cut longitudinally into 30-µm sections, then artificially glycated in 0.5 M ribose solution for 10 wk. Two-photon microscopy analysis showed that both the autofluorescence and second harmonic–generated (SHG) signal intensities of glycated samples were significantly greater than those of the controls. Regarding the structural alteration of individual collagen fibers, a remarkable increase could be measured in fiber length of ribose-treated sections. Furthermore, nanoindentation of intertubular dentin regions revealed significantly higher stiffness in the ribose-treated samples, which points at a significant accumulation of AGEs. Thus, collagen glycation occurring during sustained exposure to reducing sugars leads to profound structural and mechanical changes in dentin. Besides the numerous oral complications associated with type 2 diabetes, the premature structural and mechanical deterioration of dentin may also play an important role in dental pathology.

非酶糖基化是还原糖与长寿命蛋白质的游离氨基之间的多步缓慢反应，通过高级糖基化终产物 (AGEs) 的积累影响富含胶原蛋白的组织的结构和机械特性。作为自然老化过程的一部分，牙齿胶原蛋白暴露于糖基化。然而，在长期高血糖的情况下，这个过程会加速，导致牙本质过早硬化，导致牙齿脆弱。胶原糖基化引起牙齿机械稳定性丧失的分子机制目前尚不清楚。在这项研究中，我们使用 2 光子和原子力显微镜来关联体外糖基化诱导的牙科胶原蛋白的结构和机械变化。将年轻牙齿样品脱矿质并纵向切成 30 µm 切片，然后在 0.5 M 核糖溶液中人工糖化 10 周。双光子显微镜分析表明，糖化样品的自发荧光和二次谐波产生（SHG）信号强度均显着高于对照。关于单个胶原纤维的结构改变，可以测量到核糖处理切片的纤维长度显着增加。此外，管间牙本质区域的纳米压痕显示在核糖处理的样品中硬度显着提高，这表明 AGEs 显着积累。因此，在持续暴露于还原糖期间发生的胶原糖基化会导致牙本质发生深刻的结构和机械变化。