Oroxylin A inhibits inflammatory cytokines in periodontitis via HO­1.

Periodontal disease is a common infectious disease that can lead to the loss of teeth. Hower how to effectively suppress the inflammation with medication is unclear. The aim of the present study was to investigate the anti­inflammatory effect of Oroxylin A in periodontitis and its potential role through heme oxygenase­1 (HO­1). Primary rat gingival fibroblasts (RGFs) were cultured using the tissue block method and identified by immunofluorescence. Following lipopolysaccharide (LPS) stimulation of RGFs, Oroxylin A was administered at 50, 100, 200 or 400 µg/ml. Reverse transcription­quantitative PCR was used to assess mRNA expression of cyclooxygenase (COX)­2, TNF­α, RANKL and osteoprotegerin (OPG). Western blotting was used to detect protein expression levels of COX ­2, TNF­α, RANKL and OPG. Following HO­1 knockdown, the same treatment was performed. The expression of COX­2 in rat gingival tissue was observed by immunohistochemistry. One­way analysis of variance and Student's t test were used for statistical analysis. Oroxylin A downregulated mRNA expression of COX­2, TNF­α, RANKL and OPG in LPS­induced RGFs. With increase of Oroxylin A dose, the expression of HO­1 was gradually upregulated. When HO­1 was knocked down, Oroxylin A did not downregulate the expression of COX­2, TNF­α, RANKL and OPG in LPS­induced RGFs. Immunohistochemical results showed that expression of COX­2 was downregulated by Oroxylin A, and the expression of TNF­α, RANKL and OPG were also downregulated. Oroxylin A decreased expression of inflammatory cytokines in LPS­induced RGFs and had a good inhibitory effect on periodontitis in rats.

Advances on biodegradable zinc-silver-based alloys for biomedical applications.

The biodegradable metals have great potential for the biomedical applications, which could be gradually degraded, absorbed, or excreted in the human body, avoiding the removal though secondary surgery. Zinc-based alloys are novel series of degradable metals for medical applications, and they are gaining lots of attention in the research field of absorbable metals. Zinc-silver (Zn-Ag) alloys show superior mechanical strength, good biodegradability, biocompatibility, and antibacterial properties, which render them to be potential candidates for biomedical applications. In this paper, we reviewed the development of Zn-Ag alloys in terms of mechanical properties, degradabilities, biocompatibilities, antibacterial properties, and potential applications in dentistry.

Interleukin-8/ß-catenin mediates epithelial-mesenchymal transition in ameloblastoma.

OBJECTIVE: Epithelial-mesenchymal transition (EMT) is important in the tooth development and tumor invasion. We investigated the effect of interleukin-8 (IL-8) on the EMT process in primary-cultured ameloblastoma tumor cells (AM-P) and ameloblastoma immortalized tumor cells (AM-L) and its underlying mechanism. METHODS: IL-8 levels in ameloblastomas were detected by immunofluorescence staining and ELISA. AM-P cells and AM-L cells were stimulated with IL-8, and EMT transcription factors, total ß-catenin and phosphorylated-ß-catenin (p-ß-catenin) levels were determined by Western blot analysis and immunofluorescence staining. ß-catenin siRNA was used to knockdown ß-catenin expression in AM-P cells and AM-L cells stimulated with IL-8. RESULTS: IL-8 was highly expressed in the solid ameloblastomas. IL-8 promoted the EMT process in ameloblastoma tumor cells in vitro, as evidenced by decreased E-cadherin and increased vimentin, twist and zeb1 levels. IL-8 also increased total ß-catenin and p-ß-catenin expression in ameloblastoma tumor cells, and ß-catenin knockdown partially inhibited the EMT process in tumor cells, as evidenced by increased E-cadherin, and decreased vimentin and zeb1 levels. CONCLUSIONS: IL-8 could promote EMT in ameloblastoma tumor cells by activating ß-catenin and its downstream transcription factor zeb1.

[Bond strength evaluation of four adhesive systems to dentin in vitro].

OBJECTIVE: To compare the adhesive strength and observe the bonding interface. According to statistic analysis and scanning electron microscope (SEM) observation, the resistance capacity of four adhesive systems is evaluated. METHODS: Prime & Bond NT (PBNT), Tetric N-Bond (TNB), Clearfil SE Bond (CSEB), G Bond (GB) were bonded to the occlusal surfaces and mesial surfaces of third molars respectively. The mesial resins received shear force experiment and the fracture load were recorded. The tensile bond strength (TBS) of the remaining parts were tested. The interfacial configuration were observed under SEM. RESULTS: In the shear bond strength (SBS) experiment, PBNT and TNB showed the best result, but there was no significant difference between them (P>0.05). The SBS of PBNT was stronger than that of CSEB and GB (P<0.05). The SBS of TNB was stronger than that of GB (P<0.05). There was no significant difference between TNB and CSEB (P>0.05). In accordance with the shear force result, the TBS of PBNT and TNB was larger than CSEB and GB (P<0.05). Under SEM, resin tags of PBNT and TNB were longer and slender, the bonding layer was thick. Resin tags of CSEB were shorter, the ones of GB were the fewest and shortest. CONCLUSION: Compared to self-etching system, total-etching system could reach better bonding strength. There is some connection between the interfacial configuration of adhesives and bond strength of them.

[Evaluation of the shaping ability of four Ni-Ti rotary instruments in the preparation of simulated curved root canals].

PURPOSE: To evaluate the effect of four Ni-Ti rotary instruments on the preparation of L-shaped resin root canals. METHODS: 40 L-shaped resin root canals (curvature=38.5°) were divided randomly into four groups: Hero642,Protaper, K3 and Mtwo. Resin root canals were prepared according to the protocols. Preparation time was recorded. Original and postoperative canal images were scanned and superimposed. The preparation effect was evaluated by computer software, such as resin removal amount in inner and outer wall of root canals, change of curvature degree and radius, etc. The data was analyzed with SPSS13.0 software package. RESULTS: The preparing time of K3 was the longest. Mtwo was the shortest(P<0.05). Resin removal amount showed significant difference among the four instruments in inner root canal wall at BC, O and HO as well as in outer root canal wall at AC, HO and O. Protaper achieved the largest tapered canal,but was the worst for centering ability in the bend. Apical transportation increased near to apical foramen. The four Ni-Ti rotary instruments showed no significant difference regarding safety, undesirable shape, change of root canal's curvature degree and radius except two instrument fracture cases (K3 and Protaper) and two step cases(K3). Postoperative working length tended to be shorter,and root canals were straightened. CONCLUSIONS: Mtwo prepares simulated resin curved root canals fast. Postoperative root canal's taper by Protaper is significantly larger than Hero642. The 4 Ni-Ti rotary instruments perform good cutting ability and keep root canal's original curvature well.

Influence of cavity design on the biomechanics of direct composite resin restorations in Class IV preparations.

This study evaluated the effect of cavity design on stress distribution and fracture resistance of direct composite resin restorations in Class IV preparations. A finite element analysis (FEA) model of the maxillary central incisor with a Class IV cavity was established. Five model variations were studied: (i) a 1-mm bevel (ii) a 2-mm bevel, (iii) a plain chamfer, (iv) a stair-step chamfer, and (v) butt joints (a control configuration). All FEA variations modeled a tooth restored with composite resin loaded under 100 N at an angle of 45° to the longitudinal axis. The interfacial von Mises stress was evaluated. The FEA was complemented with an in vitro assessment. Fracture resistance of direct composite resin restorations was tested with a universal testing machine and fracture patterns were observed. Finite element analysis showed that stress in chamfer and stair-step chamfer models was more homogenously distributed, while stress in bevel models was relatively concentrated at lingual regions. Fracture resistance of a 1-mm bevel preparation was lower than for the 2-mm bevel, plain chamfer, and stair-step chamfer preparations, but was higher than for butt joints. The stair-step chamfer group presented the most favorable failure pattern. Considering biomechanics and esthetics, the present study indicates that the stair-step chamfer and 2-mm bevel should be recommended for clinical restoration.