摘要
正畸治疗的疗程一般较长，许多学者致力于加速牙齿移动速度、缩短正畸疗程的研究，而加速牙齿移动速度的本质是加速正畸骨改建的过程。
正畸牙齿移动发生的牙周组织的骨改建是一个复杂的、包括骨沉积于骨吸收的双向作用过程。研究表明，骨组织中有多个局部因子紧密调控着骨改建过程。其中TGF-β是重要的调节因子之一。TGF-β是一种多功能细胞因子，它具有促进细胞增生、调节细胞分化、促进细胞外基质合成及与其它生长因子共同参与免疫调节作用。TGF-β1是涉及骨沉积和骨吸收偶联过程的关键细胞激肽之一，通过促进基质蛋白（胶原、纤维粘接素）的形成、蛋白酶抑制剂的生成以及减少金属蛋白酶的合成，来促进组织基质生成、促进成骨细胞的分化与增殖，抑制破骨细胞前体的形成及骨吸收[8]。同时TGF-β1在体内与体外均可上调血管生成多肽，从而促进新生血管生成。
弱激光照射因其具有生物刺激作用，且使用方便，对身体无害，易被患者接受，便于临床推广等优点，已被广泛应用于临床医学各学科和口腔医学领域。有研究报道临床应用弱激光照射可缓解正畸治疗牙齿移动加力所引起的疼痛，还可以加快正畸牙齿移动速度，提高牙周组织的改建能力。
本实验的目的是（1）研究兔实验性牙齿移动时牙周组织中TGF-β1的表达变化；（2）弱激光照射对实验性牙齿移动中TGF-β1表达的影响；（3）研究弱激光照射对正畸牙齿移动牙周组织改建的影响作用
实验方法：35只健康日本大耳白兔，随机分成7组：未加力组、加力1天、3天、5天、7天、14天及21天组，每组5只。实验动物自身对照，右侧为实验侧，左侧为对照侧。动物模型的建立：以兔上颌切牙为支抗牙，
80g力拉上颌第一磨牙向近中移动。He-Ne激光照射兔实验侧颊部皮肤。He-Ne激光波长632.8nm，输出功率20mW，光斑直径3.0cm，照射距离0.5m，照射时间15min/次。除1天、3天组分别照射1次、3次外，其余各组连续照射5次，每天1次。实验组动物分别在1、3、5、7、14、21天应用多聚甲醛颈动脉灌注处死。取上颌第一磨牙及其牙周组织，制作以上颌第一磨牙为中心的、近远中方向的组织切片，行TGF-β1免疫组化染色及HE染色。观察各组标本牙周组织的变化及TGF-β1的表达情况，对TGF-β1染色灰度积分进行图像分析。
实验结果：在未加力组及加力各组牙周组织的张力区与压力区中TGF-β1均有表达。成纤维细胞、骨细胞、破骨细胞为弱阳性表达；成骨细胞为强阳性表达。加力第1天，张力区及压力区牙周组织未见明显变化，仅是牙周膜纤维排列略紊乱，TGF-β1的染色略强于未加力组的正常状态。加力第3天，压力区破骨明显，可见有吸收陷窝，破骨细胞的TGF-β1染色呈阳性表达。 加力第5天，压力区破骨活动继续存在，张力区成骨活动逐渐活跃，TGF-β1含量增加至较高水平。加力第7天牙周膜中TGF-β1的含量略降低，但仍维持较高水平，且张力区染色强度明显大于压力区。加力第14天，牙周膜中TGF-β1含量大幅减少，张力区染色强度略高于压力区。加力第21天，牙周膜中TGF-β1含量接近基础状态水平，张、压力区染色强度无明显差异。弱激光照射侧与对照侧相比，从加力后第3天开始到加力后第7天TGF-β1表达明显增强。在实验第21天照射侧与对照侧相比没有显著性差别。
结论: 该实验牙周膜中TGF-β1的含量变化表达了机械压力所引起的生物学应答的综合反应，即机械压力引起正畸牙周组织中TGF-β1的变化，
在TGF-β1的调节下，牙周组织发生改建，完成牙齿移动。弱激光照射的生物刺激作用进一步促进了牙周组织中TGF-β1的表达，从而加强了骨改建反应的活跃程度。
弱激光具有生物刺激效应，能增强各种酶的活性，影响细胞膜的通透性。牙周组织吸收激光能量后将光能转化为组织的内能，随着照射剂量的增加，实验侧无论是压力区还是张力区TGF- β1表达均较对照侧增高，且持续时间长。实验侧TGF- β1表达的时间变化规律与对照侧是基本相似的，张力区、压力区的峰值均出现在牙齿受力后第5天。由于弱激光的生物刺激效应促进成纤维细胞和成骨细胞增殖，并能提高二者的活性。张力区成骨细胞TGF- β1的表达较压力区破骨细胞的表达要强，说明TGF- β1对成骨的影响较大。
TGF- β1具有促进成骨的作用，还能促进血管生成。弱激光照射能有效促进正畸牙周组织中TGF- β1的表达，从而促进正畸牙周组织的改建。因此可以作为一种辅助治疗手段，以便提高临床正畸疗效。
Orthodontic treatment is a long term treatment. Many studies focused on how to accelerate tooth movement and reduce the active treatment time. In Physiology, The accelerating tooth movement is a process of promoting bone remodeling induced by orthodontic force, which include alveolar bone resorption and apposition. The relative research reveal that there many local factors modulating the bone remodeling process. One of them is TGF，a multifunctional modulating factor family, promote the cell hyper genesis, differentiation, and the extra cell matrix generation, also modulate the immunosystem by combining with other growth factors. TGF-β1is one of key cellular peptide, relative to the bone remodeling including bone resorption and apposition, promote the formation of cellular matrix and protein enzyme inhibitor; Decrease MMP formation. By the aboving function TGF-β1 promote osteoblast differentiation and formation and inhibit the pre-osteoclast differentiation process . Meanwhile, in Vivo and in Vitral , TGF-β1 up-modulate vascular formation peptide and promote vascular formation.
Soft laser irradiation has benn used widely in the clinical work and dentistry, with its facility of no side effect, acceptable by patients. The clinical application of soft laser in orthodontics proved that soft laser irradiation could relieve the pain from
orthodontic force, accelerate the velocity of tooth movement, and promote alveolar bone remodeling.
The purposes of our study are (1) to investigate the TGF-β1 expression level changes in PDL during the experimental rabbit tooth movement process, (2) to investigate the effect of soft laser irradiation on TGF-β1 expression level in PDL, (3) to investigate the effect of soft laser irradiation on alveolar bone remodeling.
Materials and methods:
The rabbits whose weights were almost 2.0 kilogram were chosen , and they were divided into normal group and experimental( 1、3、5、7、14、21 day ) group randomly . Each group had 5 rabbits, and the total number was 35. A coil spring was deposited between the maxillary first molar and the maxillary central incisor, the first molar of rabbit was considered as the orthodontic tooth and the central incisor was being the anchorage tooth. Using 80g force to make the first molar mesial movement. In every experimental group, low level laser irradiated the first molar at the right side, and the left side was considered as control. Irradiation time of low level laser ranged from 1 day to 5 day, once a day, 15 min each time. All experimental animals were irradiated 5 times except that 1 day group were irradiated one time and 3 day group were irradiated three times. 35 rabbits were perfused and sacrificed at 1 day, 3 day, 5 day, 7 day, 14 day and 21 day. All of tissue sections were processed,
then proceeded with HE staining and TGF-β1 immunohistochemical staining. Observing the histological changes of periodontal tissue, and the result was analyzed by the Computer Image Analyzing System and treated by statistics test.
Results: There are TGF-β1expression in the compression and tension side of PDL in both groups of non orthodontic treatment groups and orthodontic treatment groups. Lower expression of TGF-β1 was detected in the fibroblast, osteocell, osteoclast; with higher expression level in the osteoblast. In the 1 day group, no significant changes of TGF-β1 expression was noted, except disturbing sequence of fibroblasts shapes. In the 3 days group, osteoclast activation was noted and strong TGF-β1 expression exist in the compression side . In the 5 day group, osteoclast activation still exist, meanwhile significant osteoblast activation was found with peak level in this stage. In 7 day group, the expression level of TGF-β1 remain strong , but lower than 5 day group. And it level was stronger in the tension side of PDL than compression side. In 14 day group, expression of TGF-β1 in PDL decreased dramatically with higher expression level in the tension side. In 21 day group, TGF-β1 expression level return to the normal situa
引文
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