Proliferation and migration of rat incisor mesenchymal cells

Abstract– Sixty female Wistar rats were injected with tritiated thymidine and killed at intervals between 1 hr and 72 hr after injection. Autoradiographs of paraffin and Vestopal W embedded sagittal sections of the maxillary incisors were prepared. The distribution of labeled cells after 1 hr revealed the basal pulp cells and the preodontoblasts as proliferative cells. The growth rate of the incisor and the migration of the basal pulp cells were established from the position of labeled cells at 72 hr observation time. The number and localization of labeled and unlabeled mitoses were registered in order to determine the duration of the generation cycle of the proliferative cells. The identical cell generation time of preodontoblasts and basal pulp cells and the migration pattern of the latter indicate that the preodontoblasts are renewed by preodontoblast multiplication and not by migration of basal pulp cells.     

Effects of alternating and direct electrical current application on the odontoblastic layer in human teeth: an in vitro study

AIM: The aim of this study was to investigate the influence of a low intensity alternating current on the odontoblasts and odontoblast layer and compare this with the effects of a direct current. METHODOLOGY: Teeth extracted for orthodontic reasons were immersed in physiological saline stabilized with thymol crystals. Within 1 h of extraction, an alternating or direct current was applied on the crown in the direction of the apex of the tooth for 120-360 s. The current doses were 12, 30, 60, 600, 1800, 3600, 7200, 24,000 and 144,000 microC. The teeth were fixed in Bouin or Baker fluids, the pulps removed, dehydrated and immersed in paraffin, then sectioned, stained with haematoxylin and eosin, and studied under a light microscope. RESULTS: Neither direct nor alternating current, similar to that applied in electrical caries diagnosis caused histological changes in the odontoblasts. CONCLUSIONS: There was no difference between direct and low intensity alternating current in the response of the odontoblast.     

咬合创伤后牙本质形成相关细胞的形态学变化

目的：探讨大鼠咬合创伤牙齿牙本质形成相关细胞以及牙本质的变化。方法：制备大鼠下颌第一磨牙咬合创伤,观察7d、15d、30d、90d时间点牙本质的形成与吸收,牙髓组织中与牙本质形成相关的细胞的形态和数目变化。结果：实验性咬合创伤的早期,牙髓组织中成牙本质细胞和多细胞层细胞增生活跃,牙本质形成增多现象,增生区域的牙体硬组织表面为坚硬组织破坏和牙本质暴露。后期可以出现细胞萎缩现象,牙本质吸收明显。结论：咬合创伤影响牙本质的形成功能,这种影响可能与相应区域牙本质是否暴露无关。     

人牙胚体外器官培养模型的建立

目的 :建立人牙胚体外器官培养模型 .方法 :分泌前期人牙胚采用Trowell型支架培养法 ,RPMI 16 4 0培养基(含 2 0 0 g·L-1FBS ,2 0 0mg·L-1谷氨酰胺 ,2 0 0mg·L-1L 抗坏血酸 ,1× 10 -7mol·L-1维甲酸 ,10 0kU·L-1青霉素 ,10 0kU·L-1链霉素 ) ,在 37℃ ,5 0mL·L-1CO2 +95 0mL·L-1空气条件下进行培养 ,每 4 8h更换一次培养基 .体外培养 .2 ,4 ,6和 8d随机抽取牙胚进行组织学观察 .结果 :培养的牙胚组织结构关系与对照组一致 ,牙尖部形态进一步突出 ,细胞形态典型 .在 8d时 ,牙尖之间部分造釉器细胞和成牙本质细胞开始出现坏死 .结论 :为体外研究人类牙齿正常发育及各种因素对牙齿发育的影响提供了一个实用的模型     

Tertiary dentinogenesis with calcium hydroxide: A review of proposed mechanisms

Calcium hydroxide has been used extensively in dentistry for a century. Despite its widespread use as a pulp‐capping agent, its mechanisms of action still remain ambiguous. Understanding its modes of action will lead to a broader understanding of the mechanisms associated with induced dentinogenesis and help in optimizing the currently available agents to target specific regenerative processes to obtain the best possible clinical outcomes. A literature search relating to mechanisms of dentinogenesis of calcium hydroxide up to December 2011 was carried out using pubmed and MEDLINE database searches as well as manual searching of cross‐references from identified studies. Resulting suggestions regarding dentinogenic mechanisms of calcium hydroxide range from direct irritating action of the material to induction of release of biologically active molecules. The purpose of this article is to discuss various mechanisms through which calcium hydroxide may induce tertiary dentinogenesis in the light of observations made in included studies.     

Transforming Growth Factor-β1 (TGF-β1) in dentine matrix

Transforming Growth Factor-β (TGF-β) and other members of this family of growth factors have been implicated in tooth development and dental tissue repair. This study aimed to investigate regulatory factors for TGF-β1 in rabbit incisor dentine matrix and the expression of receptors for TGF-β in dental tissues better to understand the control of its biological activity. Approximately half of the TGF-β1 in dentine matrix was present in active form. TGF-β1 was found in association with latency associated peptide (LAP), betaglycan and decorin in an isolated dentine matrix preparation. Immunohistochemistry showed strong staining for TGF-β type I and II receptors in odontoblasts with more variable and weaker staining of other pulpal cells. Association of TGF-β1 with betaglycan, decorin and LAP may regulate the availability and biological activity of this growth factor and influence its presentation to the TGF-β type I and II receptors on odontoblasts. During dental tissue repair, such control processes will be important in regulating the biological effects of TGF-β1 on cells of the dentine-pulp complex.     

Collagen and Elastin in Scleroderma

The amino acid compositions of insoluble collagen and elastin purified from skin biopsies of normal subjects and scleroderma patients were conlpared. Collagen from dermis-subcutaneous tissue from the patients shows a significant increase of 3-OH proline and a slight increase in 4-OH proline and OH-lysine.

The greater hydroxylation in collagen of scleroderma tissue can be tentatively explained by the higher levels of hydroxylating enzymes in a tissue with increased collagen synthesis.