Study on the effects of mechanical pressure to the ultrastructure and secretion ability of mandibular condylar chondrocytes

During mandibular movement, condyle is subjected to repetitive compression and the mandibular condylar chondrocytes (MCCs) can detect and respond to this biomechanical environment by altering their metabolism. The present study was undertaken to investigate the effects of pressure to the ultrastructure, aggrecan synthesis, nitric oxide (NO) and prostaglandin F(1)alpha(PGF(1)alpha) secretion in MCCs. In vitro cultured rabbit MCCs were incubated and pressed under continuous pressure of 90kPa for 60min and 360min by hydraulic pressure controlled cellular strain unit. The ultrastructure, aggrecan mRNA expression, activity of nitric oxide synthase (NOS) and PGF(1)alpha secretion were investigated. Besides, nitric oxide inhibitor was used together with pressure to investigate the role of NO in mechanical effects. The appearance of MCC on TEM showed that after been pressed under 90kPa for 60min, the cellular processes became elongated and voluminous, together with aggrecan mRNA increasing. Under 90kPa for 360min, some of the cells showed distinct sign of apotosis and the aggrecan mRNA decreased. Pressure of 90kPa could cause increase of NOS activity and decrease of PGF(1)alpha composition. Inhibitor experiments indicated that pressure-induced upregulation of aggrecan mRNA and inhibition of PGF(1)alpha synthesis was partly mediated by NO. Continuous pressure could cause changes on the ultrastructure and function of MCC, as well as up-regulation of aggrecan synthesis, increase of NO secretion and decrease of PGF(1)alpha composition. NO was the upstream molecule, which mediated the response of aggrecan and PGF(1)alpha to mechanical pressure.     

A suitable base material for composite resin restorations: Zinc oxide eugenol

Objective

This in vitro study evaluated the effects of a zinc oxide eugenol (ZOE) base on the mechanical properties of a composite resin restoration.

Methods

Class I cavities were prepared on plastic teeth and filled with ZOE plus composite resin, following standard clinical procedures. The samples were sectioned sagittally and the ZOE–resin interface was exposed. After polishing, nanoindentation was performed on the region near the interface, and elastic modulus and hardness were plotted in the form of a color contour map. SEM was employed to observe the interface between composite resin and ZOE base.

Results

In the region close to the ZOE base, the elastic modulus and hardness of composite resin reduced to the values of 9.71 ± 0.54 and 0.51 ± 0.05 GPa, respectively. Eugenol from ZOE had detrimental effects on the composite resin only to a distance of less than 100 μm from the ZOE base.

Conclusion

Although eugenol suppresses polymerization slightly, by considering the biological advantages of ZOE, together with the results of the current investigation, ZOE may still be considered a suitable base material for composite resin. Bonding is essential for composite resin restorations over ZOE bases to avoid shrinkage detachment.     

Adipokines in dental pulp: Physiological,pathological, and potential therapeutic roles

BackgroundHundreds of adipokines have been identified, and their extensive range of endocrine functions—regulating distant organs such as oral tissues—and local autocrine/paracrine roles have been studied. In dentistry, however, adipokines are poorly known proteins in the dental pulp; few of them have been studied despite their large number. This study reviews recent advances in the investigation of dental-pulp adipokines, with an emphasis on their roles in inflammatory processes and their potential therapeutic applications.HighlightsThe most recently identified adipokines in dental pulp include leptin, adiponectin, resistin, ghrelin, oncostatin, chemerin, and visfatin. They have numerous physiological and pathological functions in the pulp tissue: they are closely related to pulp inflammatory mechanisms and actively participate in cell differentiation, mineralization, angiogenesis, and immune-system modulation.ConclusionAdipokines have potential clinical applications in regenerative endodontics and as biomarkers or targets for the pharmacological management of inflammatory and degenerative processes in dental pulp. A promising direction for the development of new therapies may be the use of agonists/antagonists to modulate the expression of the most studied adipokines.     

唾液腺腺癌VEGF和NOS的表达与癌细胞增殖关系的研究

目的:研究唾液腺腺癌组织血管内皮生长因子(VEGF)、诱导型一氧化氮合酶(iNOS)、内皮型一氧化氮合酶(eNOS)的表达与癌细胞增殖的相关性。方法:应用免疫组化方法检测47例唾液腺腺癌手术切除标本VEGF、iNOS、eNOS和增殖细胞核抗原(PCNA)的分布及表达。结果:①30例(63.83%)唾液腺腺癌组织表达VEGF,31例(65.96%)表达iNOS;33例(70.21%)表达eNOS;②VEGF与iNOS的表达具有明显相关性,VEGF与eNOS的表达无明显相关性;③表达VEGF的唾液腺腺癌PCNA标记指数(PLI)明显高于不表达VEGF的唾液腺腺癌;表达iNOS的唾液腺腺癌PLI明显高于不表达iNOS的唾液腺腺癌。表达eNOS的唾液腺腺癌PLI与不表达eNOS的唾液腺腺癌无显著差异(P>O.05)。结论:①VEGF与iNOS的表达具有明显相关性,说明iNOS在VEGF的生成和发挥作用过程中起重要作用;②PLI随着VEGF和iNOS表达的增加而增加;说明两者对唾液腺腺癌细胞增殖具有促进作用。     

Relationships between implant stability, image-based measures and nitric oxide levels

For monitoring of dental implants, practitioners seem to use simultaneously a variety of image-based and laboratory measurements. This longitudinal study was conducted to analyse the possible relationships between nitric oxide (NO) content of peri-implant sulcus fluid (PISF), marginal bone levels and implant stability in terms of resonance frequency analysis (RFA) at immediately (IL) and conventionally (CL) loaded mandibular molar dental implants from the same individuals. Dental implants were placed in 10 patients who had first molar loss bilaterally in the mandibular area. One site of the patient was determined as IL and the other site was CL. PISF samples, marginal bone level and RFA were taken for all dental implants during a 12-month follow-up period. For both types of loading, there were no significant changes at implant stability (ISQ) and PISF volume during the whole study period. The lowest total nitrite levels were observed at the end of 12 months. Marginal bone gain of 0.22 and 0.09 mm was noticed between 6 and 12 months in IL and CL groups, respectively. During the study period, negative correlation was noted between radiographic bone level and ISQ at both IL and CL sites; however, this correlation reached a significant level only at 6 months in CL implant group (P = 0.015). Although not significant, marginal bone loss seems to have a negative relationship with the implant stability values regardless of the mode of loading. NO metabolism around IL and CL dental implants may not demonstrate a significantly different pattern.     

大鼠实验性牙周炎牙龈组织中一氧化氮含量改变的研究

目的:探讨NO在牙周炎病理进程中的作用。方法:健康Sprague-Dawley大鼠共72只,随机分为正常对照组和牙周炎组,每组36只。参照DiPaola法复制大鼠牙周炎动物模型。分别于术后1、4和8周时处死动物,每个时间点每组处死动物12只。采用分光光度仪测量大鼠牙龈组织中亚硝酸盐(NO2-)和硝酸盐(NO3-)的含量,以间接确定NO含量;采用组织切片法观察牙周组织的组织病理学改变;应用Tiger细胞图象仪测量附着丧失(AL)。结果:术后4周和8周时,牙周炎组牙龈组织NO2-/NO3-含量明显高于正常对照组(P<0.01);在牙周炎组,术后8周牙龈组织NO2-/NO3-含量明显高于术后4周(P<0.01)。在牙周炎组,术后4周和8周与术后1周比较,AL显著增加(P<0.01);术后8周与4周比较,AL显著增加(P<0.01)。结论:NO2-/NO3-含量与牙周组织的破坏程度、AL直接相关。NO的合成在牙周组织疾病的进程中发挥作用,提示在牙周炎的治疗中控制NO的合成具有临床应用价值。     

Nitric oxide promotes the progression of periapical lesion via inducing macrophage and osteoblast apoptosis

This study aimed to elucidate the modulation by nitric oxide (NO) of the apoptosis of macrophages and osteoblasts, the essential cellular components in the development of periapical lesions. Lipopolysaccharide (LPS) induced prominent nitrite synthesis in J774 mouse macrophage cell lines. Exposure to LPS induced obvious apoptosis in J774 cells, whereas transient transfection with murine inducible nitric oxide synthase (iNOS), small interfering RNA (siRNA) diminished this effect. Tumor necrosis factor-alpha (TNF-alpha) and S-nitroso-N-acetyl-DL-penicillamine (SNAP) (a NO donor) triggered apoptosis in UMR-106 rat osteoblastic cell lines and a synergistic effect was noted when TNF-alpha and SNAP were added to the medium together. Administration of siRNAs for c-Fos and c-Jun: components of activator protein-1 (AP-1) and transforming growth factor-beta1 attenuated the combined effect markedly. Terminal deoxynucleotidyl transferase-mediated nick end-labeling (TUNEL) stain in a rat model of induced periapical lesion showed positive apoptotic signals in macrophages and osteoblasts. Administration of N(G)-monomethyl-l-arginine markedly diminished the extent of bone loss and the amounts of apoptotic macrophages and osteoblasts. In conclusion, NO mediates LPS-stimulated apoptosis of macrophages. It also induces osteoblast apoptosis and augments the pro-apoptotic effect of cytokines. Inhibition of NO synthesis in vivo attenuates apoptosis and the size of periapical lesions. Taken together, these results suggest that NO may promote the progression of periapical lesion by inducing the apoptosis of macrophages and osteoblasts.     

Activation and hydrogen absorption in thermally prepared RuO2 and IrO2

A reflection-type electrochemical cell was used to perform electrochemical in situ X-ray diffraction studies of RuO₂ and IrO₂ electrodes. X-ray diffractograms were recorded in situ as a function of the polarization time while the electrodes were poised at ?0.5 V vs SCE in 1 M H₂SO₄ at room temperature. At this potential, strong hydrogen evolution is observed at the surface of the electrodes. In both cases, there is a shift of the X-ray diffraction peaks of the rutile structure towards the lower 2θ angle values with the polarization time, indicating that the volume of the unit cell increases. In the case of RuO₂, the unit cell volume increases from 64.00 to 65.34 ų, which corresponds to a volume increase of ～2%. In comparison, the unit cell volume of IrO₂ increases from 65.56 to 66.00 ų (0.66%). These changes in the structure of the oxides occur on the time scale of a few hours. These modifications are not totally reversible, as the volume of the unit cell of both RuO₂ and IrO₂ stays slightly expanded compared to that of the pristine materials when the electrodes are brought back to open circuit conditions after extensive cathodic polarization. In the case of RuO₂, the expansion of the unit cell occurs almost exclusively along the a–a plane, suggesting that hydrogen is inserted between the O–O atoms in this plane. The significance of these results in the context of the activation process of RuO₂ and IrO₂, that is the propensity of these oxides to become better performing electrode materials when they are cathodically polarized, is discussed.     

Carbon paste electrodes of the mixed oxide SiO2/Nb2O5 prepared by the sol–gel method: dissolved dioxygen sensor

A carbon paste of SiO₂/Nb₂O₅ material was used as the electrode in the development of a dissolved dioxygen sensor in 1.0 mol l^?1 KCl solution at pH 6.2. The material was prepared by the sol–gel method. In the investigation of its electrochemical properties, linear and cyclic voltammetric and chronoamperometric techniques were employed. Dioxygen reduction, which was diffusion controlled, occurred at ?280 mV vs. SCE by a two electron mechanism, producing peroxide. A linear response between the cathodic peak current intensity and the dissolved O₂ concentration was obtained for the region between 1.0 and 13.6 mg l^?1. The stability proved to be very good over successive voltammetric cycles. The electrode response time was about 5 s. The electron transfer reactions were explained as being to an n-type semiconductor of niobia dispersed in the silica surface.     

颞下颌关节骨关节病动物模型关节滑液NO水平变化的研究

目的 研究一氧化氮(NO)与颞下颌关节骨关节病(TMJOA)模型的关系.方法 选用9只山羊通过关节上腔内注射0.5%胶原酶制造TMJOA实验动物模型,注射前、注射后4、 8、 12、 24周分别抽取关节滑液,以硝酸还原酶法检测关节滑液中NO的水平变化.结果 实验性TMJOA山羊关节滑液中NO水平明显升高,以注射胶原酶后12周为最高.结论 NO可能在TMJOA发生、进展过程中起着重要的作用.