Tissue Engineering of the Periodontal Ligament Stimulated by Orthodontic Treatment

目的：本研究采用大鼠咬合功能减退模型，观察了牙周膜（PDL）的宽度、血管的数量和大小、细胞外基质的分布以及机械感受器的分布和形态。在本研究中，我们在此模型中对功能减退的牙齿施加不同的机械应力，以阐明牙周膜功能恢复的机制。此外，我们还研究了再生的可能性，牙周膜刺激正畸forces.MATERIALS和方法：咬合功能减退的大鼠模型，通过提取磨牙或设置咬板的切牙。持续或间歇施加咬合力或2-10 gf正畸力。组织化学和免疫组化观察细胞外基质和一氧化氮合酶的分布、牙齿移动和牙根吸收。当对功能低下的牙齿施加强力时，牙根吸收被诱导。提示轻力可使牙齿顺利移动，且不引起病变。机械应力影响牙周膜细胞外基质和一氧化氮合酶的分布和合成，维持牙周膜的功能。结论：机械应力对牙周膜的影响。功能减退牙与正常牙组织有明显的不同。因此，必须改变力的强度、类型和/或持续时间，以避免诸如牙根吸收的病理变化。然而，机械应力，如咬合力或正畸力，可以恢复萎缩改变的PDL，这表明适当的机械刺激是有益的，在恢复和再生PDL。

AIM: In our study using rat occlusal hypofunction model, we have reported the changes in width of the periodontal ligament (PDL), the number and the size of blood vessels, distribution of the extracellular matrix, and the distribution and the morphology of mechanoreceptors. In this study, we applied various mechanical stresses on hypofunctional tooth in this model to clarify the mechanism of recovery in the function of periodontal ligament. Further, we also examined the possibility to regenerate the periodontal ligament stimulated by orthodontic forces.MATERIALS AND METHODS: Occlusal hypofunctional rat model was prepared by extracting molars or setting bite-plate on incisors. Occlusal force or 2-10 gf orthodontic force was continuously or intermittently applied to the hypofunctional teeth. Distribution of the extracellular matrix and Nitric Oxide synthase, tooth movement and root resorption was observed histochemically and immunohistochemically.RESULTS: The distance of the tooth movement in the hypofunctional model was different from normal model. Root resorption was induced when the strong force were applied to the hypofunctional teeth. It was suggested that lighter force could move teeth smoothly without inducing pathological changes. Distribution and synthesis of the extracellular matrix and nitric oxide synthase was influenced by mechanical stress, to maintain the function of the PDLCONCLUSION: The effect of mechanical stress on periodontal ligament of the. hypofunctional tooth was different from the normal tissue. Therefore strength, type and/or duration of the force must be changed to avoid pathological change such as root resorption. However, mechanical stress such as occlusal force or orthodontic force can recover atrophically changed PDL, which suggest that appropriate mechanical stimuli are useful in recovering and regenerating PDL.