牙周韧带细胞在纯钦表面的附着特征

目的 观察牙周韧带细胞在商用纯钛表面的附着特征。方法 MTT法分析牙周韧带细胞在商用纯钛表面的早期粘附，采用落射荧光观察细胞的粘附形态。结果 牙周韧带细胞在纯钛表面的早期粘附2h达到饱和态，且呈现不同的粘附时相。细胞之间逐渐以丝状结构联接，丝状结构与钛片的打磨走向一致，最后融合成片。结论 牙周韧带细胞在纯钛表面的粘附具有规律性，纯钛的表面处理方法对细胞的生长极性有明显影响。     

人牙龈和牙周韧带成纤维细胞的体外培养及生物学特性研究—细胞形态，生长曲线及碱性磷酸酶活性测定

目的：建立人牙龈和牙周韧带成纤维细胞体外培养模型并对其生物学特性作初步探讨。方法．；采用组织块法常规条件下分别进行牙龈和牙周韧带成纤维细胞的培养，通过光镜，透射电镜，生长曲线及碱性磷酸酶测定等手段对其部分生物学特性进行研究。结果：两种培养的原代及传代细胞在光镜下细胞排列及结构无明显判别，传代培养时牙龄纤维细胞有接触抑制现象，而牙周韧带成纤维细胞则可呈复层生长，牙周韧带成纤维细胞排列方向性较明显，生长曲线表明牙周韧带成纤维细胞增殖活性高于牙龄成纤维细胞；碱性磷酸酶活性测定及染色法显示两者有明显的判别。结论：体外培养的两种细胞在形态及排列上相似，但百细胞亚型的组成上存在差异。     

牙周韧带细胞在纯钛表面的附着特征

目的　观察牙周韧带细胞在商用纯钛表面的附着特征。方法　MTT法分析牙周韧带细胞在商用纯钛表面的早期粘附 ,采用落射荧光观察细胞的粘附形态。结果　牙周韧带细胞在纯钛表面的早期粘附 2h达到饱和态 ,且呈现不同的粘附时相。细胞之间逐渐以丝状结构联接 ,丝状结构与钛片的打磨走向一致 ,最后融合成片。结论　牙周韧带细胞在纯钛表面的粘附具有规律性 ,纯钛的表面处理方法对细胞的生长极性有明显影响     

牙周韧带细胞与成体干细胞

成体干细胞是目前研究的热点，人们陆续在多种组织中找出了成体干细胞。但是牙周韧带中成体干细胞及其与牙周韧带细胞的关系，目前尚无统一认识。本文将对该方面的研究现状作一综述。     

人牙龈和牙周韧带成纤维细胞的体外培养及生物学特性研究——细胞形态、生长曲线及碱性磷酸酶活性测定

目的 :建立人牙龈和牙周韧带成纤维细胞体外培养模型并对其生物学特性作初步探讨。方法 :采用组织块法常规条件下分别进行牙龈和牙周韧带成纤维细胞的培养 ,通过光镜、透射电镜、生长曲线及碱性磷酸酶测定等手段对其部分生物学特性进行研究。结果 :两种培养的原代及传代细胞在光镜下细胞排列及结构无明显差别 ,传代培养时牙龈成纤维细胞有接触抑制现象 ,而牙周韧带成纤维细胞则可呈复层生长 ,牙周韧带成纤维细胞排列方向性较明显 ,生长曲线表明牙周韧带成纤维细胞增殖活性高于牙龈成纤维细胞 ;碱性磷酸酶活性测定及染色法显示两者有明显的差别。结论 :体外培养的两种细胞在形态及排列上相似 ,但在细胞亚型的组成上存在差异。     

纯钛表面牙周韧带细胞牙骨质附着蛋白的表达

目的以牙骨质附着蛋白为分化指标，分析牙周韧带细胞在纯钛表面的分化趋势，并探讨诱导矿化对牙周韧带细胞牙骨质附着蛋白表达的影响。方法第三代牙周韧带细胞在商用纯钛表面接种后，分别进行常规培养和矿化液诱导矿化培养，通过免疫荧光原位检测牙骨质附着蛋白的表达，并比较诱导矿化对牙骨质附着蛋白表达的影响。结果牙周韧带细胞在纯钛表面初期呈条纹状生长，常规培养和诱导矿化培养务件下均能表达牙骨质附着蛋白，诱导矿化对牙骨质蛋白的表达无明显影响。结论在常规培养务件和诱导矿化培养条件下，纯钛表面生长的牙周韧带细胞能高度表达牙骨质附着蛋白，提示纯钛表面体外培养的牙周韧带细胞具有形成牙骨质的分化趋势，从而可为种植体周构建牙周韧带结构提供在种植体侧的锚着点。     

牙周韧带细胞及成骨样细胞在纯钛表面附着的形态学比较

目的：从形态学上比较牙周韧带细胞及成骨样细胞在纯钛表面的附着及增殖情况。方法：在相同的培养条件下，商用纯钛表面分别接种牙周韧带细胞和成骨样细胞，采用倒置显微镜及扫描电镜进行形态学观察。结果：两种细胞在纯钛表面均附着、生长良好，7天后细胞即连接成片，并在钛片边缘存在“细胞聚集”现象，呈现复层生长。扫描电镜显示两种细胞附着早期呈“伪足”样伸展，附着后期形成大量的细胞外基质成份。两种细胞在细胞形态、“伪足”形态及钛片周边聚集形态上均存在明显差异。结论：牙周韧带细胞和成骨样细胞与纯钛均有良好的生物相容性，在体外培养过程中，呈现不同细胞形态、“伪足”形态及钛片周边聚集形态，提示两种细胞在分化过程中可能存在差异。     

Scleraxis在牙周韧带细胞、牙龈成纤维细胞中的表达

目的研究碱性螺旋-环-螺旋转录因子 Scleraxis 能否在人牙周韧带细胞、牙龈成纤维细胞、骨髓基质细胞中表达,及其与牙周韧带细胞分化能力的关系。方法体外培养人牙周韧带细胞、牙龈成纤维细胞和骨髓基质细胞,RT-PCR 法检测牙龈成纤维细胞、骨髓基质细胞及不同代次牙周韧带细胞中 Scleraxis 的表达。结果 Scleraxis 在牙周韧带细胞、骨髓基质细胞及牙龈成纤维细胞中的表达差异有统计学意义(P<0.05)。其 Scleraxis 与β-肌动蛋白吸光度比值分别为0.877±0.024,0.438±0.031,0.313±0.083。Scleraxis 在牙周韧带细胞中的表达最强,在牙龈成纤维细胞中表达最弱。牙周韧带细胞中 Scleraxis 的表达随培养代次的增加而减弱。结论 Scleraxis 可表达于体外培养的牙周韧带细胞、牙龈成纤维细胞和骨髓基质细胞,Scleraxis 可能在牙周韧带细胞的分化过程中起重要作用。     

人牙周韧带纤维及细胞含量的组织学测定

目的：测定成人牙周韧带组织中的各类纤维含量以及夏普氏纤维征牙骨质和牙槽骨硬骨板中的分布情况。方法：选取外科切除含健康牙的人下颌骨块，进行纤维特殊染色，用体视框和图象分析法测量。结果：人牙周韧带中胶原纤维含量最多，约为60％，细胞成分约占8％，夏普氏纤维在乐槽骨骨硬板和牙骨质中的分布密度分别为1．90％，1．88％。结论：人牙周韧带组织中的纤维以胶原纤维为主，并含有少量的其它纤维和细胞成分。其特殊的纤维类型及分布是牙周韧带行使正常生理功能的组织结构学基础。     

人牙周韧带细胞在聚羟基乙酸支架上体外三维培养的实验研究

目的：应用聚羟基乙酸(polyrglycolic acid，PGA)作为人牙周韧带细胞(periodontal ligament cell，PDLC)的三维体外培养支架，观察细胞的形态学特征和生物学性状。方法：将人牙周韧带细胞与PGA三维支架进行体外复合培养，用倒置相差显微镜和扫描电镜观察细胞形态结构及其与支架的粘附性和组织相容性，并用Ⅰ型胶原抗体检测细胞的Ⅰ型胶原分泌情况。结果：光镜和扫描电镜显示，人PDLC在PGA三维支架上粘附良好，分泌基质旺盛。免疫组化染色显示细胞支架复合物中Ⅰ型胶原表达阳性。结论：人PDLC在PGA三维支架上能够维持其形态学特征及生物学性状。聚羟基乙酸具有良好的粘附性和生物相容性，适宜进一步作为构建组织工程化牙周韧带的支架材料。     

A nonlinear finite element analysis of the periodontal ligament under orthodontic tooth loading

The stressed state of the periodontal ligament (PDL) is understood to play a critical role in the tooth movement initiated by orthodontic treatment. Finite element simulations have been used to describe PDL stresses for orthodontic loading; however, these models have predominantly assumed linear mechanical properties for the PDL. The present study sought to determine the importance of using nonlinear mechanical properties and nonuniform geometric data in computer predictions of periodontal ligament stresses and tooth movements. A 2-dimensional plane-strain finite element model of a mandibular premolar was constructed based on anatomic data of transverse sections of tooth, PDL, and bone from a 24-year-old cadaveric man. A second model was constructed of the same tooth but with a PDL of uniform thickness. Each of these was prescribed linear or nonlinear elastic mechanical properties, as obtained in our own experiments. Predictions of the maximum and minimum principal stresses and von Mises stresses in the PDL were determined for extrusive and tipping forces. The results indicated that biofidelic finite element models predicted substantially different stresses in the PDL for extrusive loading than did the uniform thickness model, suggesting that incorporation of the hourglass shape of the PDL is warranted. In addition, incorporation of nonlinear mechanical properties for the PDL resulted in dramatic increases in the stresses at the apex and cervical margin as compared with the linear models.     

Nonlinear stress-strain behavior of periodontal ligament under orthodontic loading.

Previous studies of the periodontal ligament (PDL) have applied high forces to the dental units to examine the stress-strain behavior of this soft tissue. In this study, cadaveric specimens of mandibular premolars from 2 young adult and 2 elderly adult donors were tested to determine the biomechanical behavior of the PDL over an orthodontic force range. Transverse specimens were prepared from 9 premolars and subjected to loading in intrusion and extrusion. Stress-strain curves for both loading directions had distinct toe and linear regions, demonstrating nonlinear behavior of the PDL. The average linear shear modulus was higher for intrusion than for extrusion. The toe extrusive modulus was higher for the young group, and extrusive toe size was larger for the elderly group. In extrusion, the average modulus was higher for the cervical margin and the apex regions than for the midroot regions. The size of the toe region was smaller for intrusion than extrusion. The results indicate age-dependent, location-dependent, and load-direction-dependent nonlinear properties of the human PDL and suggest that analytical computer simulations of orthodontic tooth movements might benefit from incorporating the nonlinear material properties of the PDL.     

牙周膜本构模型的研究进展

牙周膜的形变与牙齿的移动联系密切,阐明两者之间的关系对于正畸治疗有很大帮助.建立牙周膜本构模型对研究牙周膜应力-应变关系有重要意义.线弹性、非线性等本构模型已被提出,但仍存在争议,主要原因是牙周膜体内、体外的实验数据不够精确.本文就牙周膜本构模型的种类,牙周膜相关体内、体外实验的进展作一综述,并进行了展望.     

Effect of splinting on the mechanical and histological properties of the healing periodontal ligament in the vervet monkey (Cercopithecus aethiops)

Healing of the periodontal ligament (PDL) after extrusive luxation of two upper central incisors was evaluated when one tooth was splinted and the other left untreated. One millimetre thick, transverse sections of tooth, PDL and alveolar bone were examined in a materials testing machine. Load deformation curves were recorded and a number of mechanical properties were assessed. To eliminate the influence of differences in sizes and fibre arrangements, load values were reduced by the area and deformation values by the width of the PDL, and comparisons between splinted and non-splinted teeth were made at identical root levels 2 weeks after injury. Healing was also evaluated histologically at 1, 2, 3, 4 and 8 weeks after injury. There were no significant differences in mechanical and histological properties between splinted and non-splinted teeth, which suggests that splinting is of doubtful value in treatment of extrusive luxated teeth. The values for the mechanical properties of injured PDL had returned to 50-60% of those of uninjured PDL by 2 weeks after injury, indicating a rapid healing rate.     

Force-induced IL-8 from periodontal ligament cells requires IL-1beta

During orthodontic tooth movement, mechanical stresses induce inflammatory reactions in the periodontal ligament (PDL). We hypothesized that chemokines released from PDL cells under mechanical stress regulate osteoclastogenesis, and investigated the profiles and mechanisms of chemokine expression by human PDL cells in response to mechanical stress. In vitro, shear stress and pressure force rapidly increased the gene and protein expressions of IL-8/CXCL8 by PDL cells. Consistently, amounts of IL-8 in the gingival crevicular fluid of healthy individuals increased within 2 to 4 days of orthodontic force application. The PDL cells constitutively expressed low levels of IL-1beta, which were not further increased by mechanical stress. Interestingly, neutralization of IL-1beta abolished IL-8 induction by mechanical stresses, indicating that IL-1beta is essential for IL-8 induction, presumably though autocrine or paracrine mechanisms. Finally, experiments with signal-specific inhibitors indicated that MAP kinase activation is essential for IL-8 induction.     

Effects of mechanical stress on the mRNA expression of S100A4 and cytoskeletal components by periodontal ligament cells

The periodontal ligament (PDL) functions under constant mechanical stress, and PDL cells obviously control PDL functions under such conditions. We have previously found that the mRNA expression of the Ca2+-binding protein S100A4 and beta-actin is higher in the PDL from erupted teeth than in the PDL from teeth under eruption. This suggested a role for S100A4 in the response of PDL cells to mechanical stress, possibly by coupling Ca2+ and the cytoskeletal system. In the present study, we investigated the direct effects of cyclical stretching on the mRNA expression of S100A4 and two cytoskeletal components (beta-actin and alpha-tubulin) by PDL cells. In Northern blotting analysis, the expression of S100A4, beta-actin, and alpha-tubulin mRNAs was higher in the PDL from fully erupted and functional bovine teeth than in partially erupted ones. Similarly, when bovine PDL cells were mechanically stimulated by means of the Flexercell Strain Unit, the expression of S100A4, beta-actin, and alpha-tubulin mRNAs increased over the control levels. The results of our present study indicate that S100A4 is involved in the responses of PDL cells to mechanical stress possibly by coupling Ca2+ to the cytoskeletal system in these cells.     

Restoration of mechanical strength and morphological features of the periodontal ligament following orthodontic retention in the rat mandibular first molar

Biomechanical properties and morphological features of the periodontal ligament (PDL) in the rat mandibular molars were examined during orthodontic retention. Seventy-three male rats of the Wistar strain, 8 weeks of age, were used for biomechanical analysis and six rats for morphological analysis. An elastic band was inserted between the mandibular first and second molars for 4 days; after removal of the elastic band the interdental space was filled with resin for 4 and 8 days. The maximum shear stress, tangent modulus, and failure strain energy density of the PDL of the first molar in the experimental animals decreased markedly following application of an orthodontic force. They increased rapidly and were restored completely to the control levels by the 8th day after retention. Light microscopy showed severe compression and extension of the PDL in the experimental animals on the 8th day after retention. Birefringent collagen fibre bundles running across the compressed and expanded PDL were observed, although they appeared to be thinner with less insertions into the alveolar bone or cementum in the experimental animals than in the controls. This suggests that the periodontal collagen fibres were partially reorganized and rearranged during retention. The reorganization and rearrangement of periodontal collagen fibres seemed to be partly related to the restoration of mechanical strength of the rat molar PDL during the 8 days of retention.     

Identification of genes related to mechanical stress in human periodontal ligament cells using microarray analysis

BACKGROUND AND OBJECTIVE: Differential expression of genes in human periodontal ligament (PDL) under mechanical stress, such as orthodontic force, is thought to be involved in the remodeling of PDL cells and periodontal tissues. However, little is known about the genes expressed in PDL cells under mechanical stress. MATERIAL AND METHODS: We employed microarray analysis to assess, in a comprehensive manner, the gene expression profiles in PDL cells compressed by a static force using an in vitro three-dimensional culture system. Six genes were selected and validated by quantitative real-time polymerase chain reaction analysis, consistent with the microarray data. RESULTS: The microarray data revealed that 108 of 30,000 genes tested were differentially expressed by mechanical force loading. Among them, 85 genes were up-regulated by mechanical stress, while 23 genes were down-regulated, judging by the thresholds of a two-fold increase/decrease compared with the controls. Thirty-two of the up-regulated and eight of the down-regulated genes, well-characterized in protein function, were involved in numerous biological processes including cell communication, cell signaling, cell cycle, stress response, and calcium release. However, several genes differentially expressed in our microarray data have not been well defined as stress-response molecules. CONCLUSION: Our microarray is the first to show the gene profile in PDL cells caused by mechanical stress; however, further studies to clarify the physiological function of these molecules in PDL cells are required.     

Mechanical characterization of bovine periodontal ligament

This study is part of a research program that aims to develop a constitutive three-dimensional model of the periodontal ligament (PDL) through the identification of pertinent material parameters. As part of this program, bovine PDL was utilized to establish stress-strain responses under tensile and compressive loading conditions. Fresh bovine molars were secured, frozen and prepared to appropriate dimensional specifications. Bar-shaped specimens that comprised portions of dentine, PDL and bone were produced. Push-pull tests were conducted using a specifically constructed loading machine. Full range monotonic stress-strain diagrams were generated. The effect of a rate increase on cyclic S-E diagrams was also determined. The influence of specimen thickness was expressed in terms of modulus of elasticity, strength, uniaxial maximizer strain, and strain energy density. The overall load-response was heavily hysteretic in compression. On the tensile side, after a steep rise, the curve tended to flatten out asymptotically. Variations in rate that spanned four orders of magnitude had no effect on reciprocal load responses. The E-modulus was in the 4-8 MPa range, the strength of the PDL was 1-2 MPa, the maximizer strain was at 45-60% and the strain energy density ranged between 0.3 and 0.4 MPa.