年轻恒牙组织形态的超微结构观察

  目的 观察年轻恒牙形态的超微结构特点,并分析年轻恒牙牙体硬组织结构特点与龋患关系。方法 取临床因正畸治疗需要而拔除的根尖孔尚未完全闭合的恒前磨牙作为标本,应用透射电镜和扫描电镜观察年轻恒牙釉质表面、髓腔内侧壁牙本质及根尖区牙骨质的超微结构形态。结果 电镜下年轻恒牙的釉质表面为多孔状,牙本质小管密集,横断面呈圆形,成牙本质细胞较多。结论 年轻恒牙的组织形态超微结构特点是龋病易感的主要因素。     

锌指E盒结合同源框2在人牙髓组织和细胞的表达

目的：检测锌指E盒结合同源框2（ZEB2）在人牙髓组织和细胞中的表达,并初步探讨其意义。方法：制作牙髓组织石蜡切片,荧光原位杂交技术（FISH）检测 ZEB2的表达;实时荧光定量聚合酶链反应（RT-qPCR）检测正常及TGF-β1刺激下人牙髓细胞（hDPCs）中ZEB2 mRNA表达水平;制作hDPCs细胞爬片, FISH检测ZEB2的表达。结果： FISH结果显示ZEB2在牙髓组织中主要表达于成牙本质细胞层,在牙髓细胞呈弱阳性表达。 RT-qPCR结果显示TGF-β1的作用促进ZEB2的表达,且具有浓度和时间依赖性,5ng/ml TGF-β1刺激ZEB2表达达最大（P〈0.05）;5ng/ml TGF-β1刺激后, ZEB2 mRNA在24h内表达逐渐上调,24h达峰值（P〈0.05）。 FISH结果示ZEB2在正常hDPCs胞质和胞核均呈弱阳性表达, TGF-β1刺激24h后ZEB2表达增强,胞核表达明显。结论： ZEB2在牙髓组织中主要表达于成牙本质细胞层,正常hDPCs中弱阳性表达,而TGF-β1可促进hDPCs中ZEB2表达,提示ZEB2可能通过参与TGF-β1信号通路调控hDPCs的成牙本质向分化过程。     

Potential Correlation between Statins and Pulp Chamber Calcification

Introduction

3-Hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (statins) are the first-line pharmaceuticals for the prevention and treatment of dyslipidemia. A recent investigation has shown that statins induced odontoblastic differentiation of dental pulp stem cells. Statins enhance the differentiation of human dental pulp cells by up-regulating mineralization nodules and odontogenic markers. This study tested the hypothesis that the systemic administration of statins results in increased dental pulp calcification.

Methods

This retrospective case-control study used digital bitewing radiographs of mandibular molars. Subjects (N = 90) aged ≥60 years were assigned to either test (n = 45) or control (n = 45) groups based on the systemic use of statins. The dimensions of the pulp chambers were measured using a standardized method for height and mesiodistal distances. The chi-square test was used to analyze the data. Multiple linear regression model analysis was performed to explore the association between statin intake and pulp calcification.

Results

Three of the 45 mandibular molars in the test group exhibited almost complete pulp chamber obliteration. There was a significant reduction in pulp chamber height ratio shown in the statin group compared with the control group (P < .0001). When the mesiodistal width was compared between the 2 groups, there was no significant difference (P = .3730).

Conclusions

The significant increase of calcification and loss of vertical height of the pulp chamber observed in mandibular molars in patients on statin medication indicated a possible increased odontoblastic activity. Therefore, systemic statins could be a contributing factor for pulp chamber calcification.     

Freeze-fracture studies of the distal plasma membrane of rat odontoblasts during their differentiation and polarisation

We have examined freeze-fracture replicas of maxillary first molar tooth germs of newborn rats at early stages of dentinogenesis to study the development of tight junctions in the distal plasma membrane of differentiating odontoblasts. In addition, freeze-fracture was combined with filipin to observe the distribution of cholesterol on the distal plasma membrane of odontoblasts during differentiation. Only gap junctions were present in early differentiating odontoblasts. The distal plasma membrane exhibited low cholesterol content, which might indicate high fluidity. With the beginning of mineral deposition in matrix-vesicles, the first signs of tight junction formation were observed. Further development revealed increasingly complex focal tight junctions. In later stages, when mineralisation is observed progressing to the fibrillar and non-fibrillar constituents of the matrix, well developed focal tight junctions were detected. Concomitantly, cholesterol in distal portions of the odontoblast plasma membrane increased, indicating, probably, a higher rigidity. Thus, a distal plasma membrane domain is established, odontoblasts become fully differentiated, and partial compartmentalisation of matrix occurs. At this stage, odontoblasts may be able to secrete specific matrix molecules to ensure the progression of mineralisation.     

Differential effects of growth differentiation factor-5 on porcine dental papilla- and follicle-derived cells

In this study, the effect of growth differentiation factor-5 (GDF-5) on the growth and differentiation of porcine dental papilla- and follicle-derived cells was investigated. Furthermore, the effect was compared with that of BMP-2. Recombinant mouse GDF-5 (rmGDF-5) enhanced alkaline phosphatase (ALP) activity in dental papilla-derived cells in a dose-dependent manner, while ALP activity in dental follicle-derived cells was reduced. In rmGDF-5 stimulated dental papilla-derived cells, the expressions of odontoblast-marker genes were up-regulated. Conversely, recombinant human BMP-2 (rhBMP-2) enhanced ALP activity dose-dependently in both dental papilla- and follicle-derived cells. When combined, GDF-5 did not further enhance BMP-2-induced ALP activities. Rather, GDF-5 reduced BMP-2-induced ALP activities in both dental papilla- and follicle-derived cells. This suggests that affinity of GDF-5 to the shared receptors may be higher than that of BMP-2 in both cell types. These observations indicate that GDF-5 regulates differentiation of both dental papilla and follicle during odontogenesis, co-operatively with other growth factors such as BMP-2.     

High resolution scanning electron microscopy of the subplasmalemmal cytoskeleton in human odontoblasts

Abstract – The subplasmalemmal cytoskeleton in human odontoblasts was studied by high resolution scanning electron microscopy. The odontoblast layer was isolated and exposed to formaldehyde, glutaraldehyde, and OsO₄ for some specimens, while the membraneous structures and soluble proteins in the dental tissue were removed by Zenker's solution and 1% OsO₄ for other specimens, without further fixation of the remaining components. The cytoskeletal elements comprised a dense network of interlacing filaments of different diameters in the cell body. Most cytoskeletal elements were parallel to the axis of the cell processes situated inside the dentinal tubules. The appearance and orientation of the investigated subplasmalemmal cytoskeletal elements was unaffected by the choice of method. Both methods confirm the presence of a subplasmalemmal cytoskeleton in human odontoblasts.