Effect of tension-force on plasminogen activator activity from human periodontal ligament cells

The plasminogen activator (PA)-plasmin proteolytic system has recently received considerable attention because of its participation in a wide variety of biological activities and in pathological conditions involving tissue destruction. Excessive mechanical stress such as occlusal trauma is associated with alveolar bone loss in severe periodontitis. Therefore, mechanical stress may involve degradation of the extracellular matrix by occlusal trauma through activation of the PA-plasmin proteolytic system. We examined the effects of mechanical stress on PA activity, gene expressions of tissue type (t) PA, urokinase type (u) PA and PA inhibitor-1 (PAI-1) in human PDL cells. Human PDL cells were cultured on flexible-bottomed culture plates and placed on a Flexercell Strain Unit. The cells were flexed at 6 cycles (5 s strain, 5 s relaxation) at 9% and 18% elongation for 5 d. Application of tension-force induced significantly higher PA activity in stressed PDL cells than in non-stressed controls, and did so in a time- and magnitude-dependent manner (p<0.001, ANOVA). Western-blot analysis revealed that the high level of activity was due to tPA and not uPA. Gene expression of tPA mRNA in stressed PDL cells, as examined by RT-PCR, increased on d 5. These findings suggest that tPA may be involved in periodontal metabolism in response to mechanical stress.     

放射线检查在龋病诊断中的价值

放射线检查是龋病诊断中常用的辅助手段，本文讨论了根尖片与翼片、数字式根尖片与数字式翼片、放射屏幕影像仪（ＲＶＧ）、纵向显微放射法（ＬＭＲ）、激光诱导荧光法（ＬＡＦ）等方法在龋病诊断中的优缺点。并提出以直接数字式系统取代湿片过程和胶片贮存，尽量减少射线剂量、以及将龋病的诊断定位于早期脱矿阶段是放射线检查在龋病诊断中的发展方向。     

Comparative study of the configuration and the cleanliness level of root canals prepared with the aid of sodium hypochlorite and bis-dequalinium-acetate solutions

Bis-dequalinium acetate (BDA), a quaternary ammonium compound, was introduced as a bactericidal and chemotherapeutic agent for endodontic use. This study was undertaken to compare the efficacy of this compound to 5.25% sodium hypochlorite in the cleansing and shaping of root canals. One hundred twenty freshly extracted teeth were divided into three groups. Each group was treated with the aid of the test material; saline solution was used as a control. After completion of the endodontic preparation, a silicone imprint of the canals was performed and the teeth were decalcified. The imprints were examined three-dimensionally to determine the amount of debris and canal configuration due to defective preparation and anatomic variation. No significant difference could be observed between the tested materials with respect to cleanliness and the shape of the canals. At the apical third, however, the BDA-treated canals showed more favorable results with respect to cleanliness. On the basis of the present and previous findings, it was concluded that BDA might be a favorable replacement for sodium hypochlorite as an irrigation solution.     

Glycylprolyl dipeptidylaminopeptidase from Bacteroides gingivalis

Dipeptidyl aminopeptidase activity was found in the culture medium of Bacteroides gingivalis 381. The enzyme, hydrolyzing glycylprolyl-4-methylcoumaryl-7-amide, was purified 750-fold from culture medium by ammonium sulfate precipitation, Sephadex G-200 gel filtration, and DEAE Bio Gel A column chromatography. The molecular weight, determined by gel filtration, was approximately 160,000. The isoelectric point of the enzyme, estimated by isoelectric focusing using polyacrylamide disk gel electrophoresis, was about pH 6.2. The optimum pH of the enzyme was about 8.0, and the Km value was 0.05 mM. The enzyme activity was strongly inhibited by phenylmethylsulfonylfluoride and diisopropylfluorophosphate. The purified enzyme specifically cleaved glycylprolyl dipeptide from partially digested type I collagen.