Effect of two kinds of surface pretreatments on bending strength to the modified polyetheretherketone / 华西口腔医学杂志

OBJECTIVE@#To evaluate the effect of sandblasting or acid etching on the three-point bending strength to the modified polyetheretherketone (PEEK).@*METHODS@#Forty-eight bars (15 mm×2 mm×1 mm) of specimens were fabricated from the modified PEEK (BioHPP). They were randomly divided into the following groups: A, B, C and D groups, which were blasted with alumina particles; E, F, and G groups, which were etched with 98% concentrated sulfuric acid; and control group H. The sand blast pressure of groups A, B and C was 0.2 MPa, and the grain sizes of the sand blasted were 120, 50, and 250 µm, respectively. Group D was blasted with 120 µm particle size at 0.7 MPa pressure. Groups E, F and G were acid etched for 60, 120, and 300 s, respectively. No surface treatment was conducted in group H. After all the specimens were processed, one sample was randomly selected from each group to observe its surface morphology under a scanning electron microscope (SEM), and the other specimens were tested for their three-point bending strength. SPSS 22.0 software was used to analyze the experimental data and to test whether the difference was statistically significant.@*RESULTS@#SEM observation showed that the surface morphology of the specimen changed after the treatment and revealed different degrees of cracks, pits, or voids. The three-point bending test indicated that the strength of the specimens treated with sandblasting or concentrated sulfuric acid decreased compared with that of the control group (P0.05). The strength of group D was lower than that of group A at the same particle size (P0.05).@*CONCLUSIONS@#The bending strength of BioHPP could be significantly decreased by surface sand blasting or concentrated sulfate etching as the sandblasting pressure increased, but the bending strength did not decrease as sand particle size and acid etching time changed.

Mechanism of PRDX3 Involved in Development and Progression in Clear Cell Renal Cell Carcinoma / 中山大学学报(医学科学版)

@#【Objective】 To investigate the relationship between the expression of PRDX3 （thioredoxin-dependent peroxide reductase）and the occurrence and development of ccRCC （clear cell renal cell carcinoma）. 【Methods】 The expression of PRDX3 was first verified in 16 cases of ccRCC tissues and adjacent normal tissues. In the present study ， according to the PRDX3 over-expression level，we established the stable PRDX3 overexpression cell lines and knockdown cell lines in 786-O cell lines. We detected the growth rate of tumor cells after overexpression and knockdown of PRDX3. Interaction proteins with PRDX3 were searched by anti-flag pull-down test combined with LC- MS/MS technique. The interaction between PRDX3 and PRDX1（peroxiredoxin 1）was preliminarily explored.【Results】The western blot results showed that PRDX3 were down- regulated in 14 out of 16 ccRCC tissue samples about 1.78 times. Stable PRDX3 overexpression and knockdown cell lines and those control group were successfully established［786O- PRDX3（+）and 786O- PRDX3（-），786O- PRDX3 KN and 786O- PRDX3 NCi］. PRDX3 expression in 786O- PRDX3（+）was 2.1 times higher than 786O- PRDX3（-）at mRNA level and 1.8 times at protein level. PRDX3 expression in 786O- PRDX3 KN was 0.48 times lower than 786O-PRDX3 NCi at mRNA level and 0.51 times at protein level. The cell growth rate of 786O-PRDX3 （+）cell lines was significantly lower than that of 786O-PRDX3（-）. Meanwhile ，there was no significant difference in 786O-PRDX3 KN and NCi cell lines. Pull-down results shows that PRDX3 may interact with PRDX1 through disulfide bond and the binding sites of those two proteins were identified respectively.【Conclusion】PRDX3 was down- regulated expression in renal clear cell carcinoma and the interaction with PRDX1 may be involved in the occurrence and development of tumor. Increasing the expression level of PRDX3 can significantly reduce the growth rate of tumor cells. Based on PRDX3 ，it is possible to develop targeted drugs for treating renal clear cell carcinoma.

Effects of body-shade resin layer thickness on the color of polyetheretherketone-Crea.lign restorations / 华西口腔医学杂志

OBJECTIVE@#This study aims to assess the effects of the different thicknesses of body-shade resin layers on the color of polyetheretherketone (PEEK)-Crea.lign restorations.@*METHODS@#Five PEEK specimens with the thickness of 0.6 mm were prepared. The color values of PEEK specimens were measured. Afterward, opaque-shade resin layers (0.1 mm) and body-shade resin layers (1.5 mm) were stacked with mold. The five specimens were evenly ground to a thickness of 1.4, 1.2, 1.0, 0.8, 0.6, 0.4, 0.2, and 0.0 mm in sequence. After grinding and ultrasonic cleaning, the color value was measured.@*RESULTS@#With the constant thickness of PEEK and 0.1 mm thickness of opaque-shade resin layer, the L*, a*, and b* values all showed downward trend with the increased thickness of the body-shade resin layer (1.0-1.4 mm). With the constant thickness of PEEK and 0.1 mm thickness of opaque-shade resin layer, the color difference between the adjacent groups was less than 1.5 NBS. This difference between nonadjacent groups was more than 1.5 NBS when the thickness of the body-shade resin layer reached 0.6 mm. Color difference between PEEK-Crea.lign restoration and PEEK was more than 1.5 NBS.@*CONCLUSIONS@#The thickness change in the body-shade resin layers influence the color of the PEEK-Crea.lign restorations. Using A2 shade Crea.lign, opaque-shade resin layer thickness is 0.1 and 0.6 mm thickness of body-shade resin layer can produce color which clinically acceptable.

Influence of nano-silica content on flexural properties of the aluminum borate whisker and silica filler composite resins / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To discuss the influence of nano-silica content which was hydrolyzed by tetraethyl orthosioate (TEOS) on the aluminum borate whisker (AlBw) and silica filler composite resins on flexural properties.</p><p><b>METHODS</b>The nanometer-size silicon dioxide (SiO2) particles were prepared by sol-gel method based on tetraethyl orthosioate. Different proportion of AlBw and SiO2 were fused and attached onto the surface of AlBw through high temperature, then polymerized with resin matrix after surface siliconization and their flexural strength and flexural modulus were determined. The effects of heat treatment to the surface morphology of AlBw and the shapes of the mixture at various proportions were characterized by TEM.</p><p><b>RESULTS</b>The flexural properties of dental composite resins with AlBw-SiO2 compound as inorganic fillers were significantly improved. The flexural property of a new type of dental composite resins was(130.29 +/- 8.38) MPa, when the mass ratio of AlBw and nano-SiO2 particle was 3:1.</p><p><b>CONCLUSION</b>Nano-silica content which was hydrolyzed by tetraethyl orthosioate improved flexural properties of the aluminum borate whisker and silica filler composite resins.</p>

Comparison of fracture resistance of pulpless teeth restored with fiber reinforced composite posts and three kinds of resin core material / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To compare the fracture resistances of pulpless teeth restored with FRC (Fiber Reinforced Composite) posts and three kinds of resin core material.</p><p><b>METHODS</b>A total of 42 recently extracted upper incisors were randomly divided into 3 groups. Group A was restored with prefabricated glass-fiber posts and Artglass polymer core; group B with prefabricated glass-fiber posts and Charisma composite resin core; and group C with prefabricated glass-fiber posts and AB composite resin core. In every group, the core material was processed by hot-press and non hot-press respectively. The posts size and shape were identical in the 3 groups. All teeth were fully covered with polycarbonate resin crowns. Fracture resistance was measured by applying point force at 130 degrees to the long axis of the teeth on an universal testing machine.</p><p><b>RESULTS</b>Mean fracture threshold was 505.4 N +/- 42.0 N and 564.1 N +/- 41.7 N in group A, 411.3 N +/- 23.3 N and 315.3 N +/- 19.1 N in group B and 358.4 N +/- 36.1 N and 423.4 N +/- 47.5 N in group C. In all groups, there was no posts fracture and polycarbonate resin crowns fragmentation.</p><p><b>CONCLUSION</b>The composite restoration of FRC posts combined with resin core and resin crown can improve the fracture resistance of the pulpless roots. The strength of resin core material can be increased by hot-press methods.</p>