[Study on the bending strength of cast porcelain material of different linker sizes].

PURPOSE: To investigate the relationship between size of different connectors and bending strength of cast porcelain materials. METHODS: The samples were divided into 5 groups according to the area of all-porcelain materials and simulated connector. In group A, simulated connector with cast porcelain material with a cross-section of 2 mm×3 mm was selected; In group B, simulated connector with cast porcelain material with a cross-section of 2 mm×4 mm was selected; In group C, simulated connector with cast porcelain material with a cross-section of 3 mm×3 mm was selected; In group D, simulated connector with cast porcelain material with a cross-section of 3 mm×4 mm was selected; In group E, simulated connector with zirconium oxide material with a cross-section of 2 mm×3 mm was selected. The fracture load was tested using classical three-point bending experiment, statistical analysis was performed using SPSS 18.0 software package. RESULTS: For lithium disilicate cast porcelain, the fracture load increased with increasing cross section area, but both below the shear zirconia fracture load with a cross section of 2 mm×3 mm(P＜0.05).The increase in width increased the fracture load of porcelain samples compared to the length. CONCLUSIONS: It is suitable to increase linker area when cast porcelain is applied to single-end bridge, which is especially achieved by increasing the width at the linker.

[Berberine promotes osteogenic differentiation of rat adipose-derived stem cells through JNK signaling pathway].

PURPOSE: This study aimed at exploring the effect of berberine (C20H18NO4) on osteogenic differentiation of rat adipose-derived stem cells(ADSCs) and clarifying the related mechanism. METHODS: ADSCs were subjected to 5, 10, 20 µmol/L berberine culture solution. The untreated ADSCs were set as the control group. Cell proliferation activity was determined by MTT method. Alkaline phosphatase (ALP) staining, semi-quantitative assay and alizarin red staining (ARS) were applied to analyze the effect of berberine on osteogenic differentiation of ADSCs. The phosphorylation level of c-Jun amino terminal kinase (JNK) protein was tested by Western blot. Runx2, OCN were tested by Western blot before and after application of JNK pathway inhibitor SP600125. SPSS 22.0 software package was used for statistical analysis. RESULTS: There was no significant difference on cell proliferation activity of ADSCs treated with 5, 10 and 20 µmol/L berberine at 1, 3 and 7 day(P>0.05). ALP staining and ARS staining in groups treated by berberine were significantly darker than those of the control group, and ALP protein secretion in the experimental group was significantly up-regulated (P<0.05). The phosphorylation level of JNK was increased after treated with 10 µmol/L berberine culture medium. The expression of osteogenic related proteins Runx2 and OCN was up-regulated in the experimental group. After inhibition of JNK signaling pathway, the expression of Runx2 and OCN was down-regulated. CONCLUSIONS: Berberine has no effect on cell proliferation of ADSCs, and can up-regulate osteogenic differentiation of ADSCs through activation of JNK signaling pathway.

[Fracture resistance of endodontically treated maxillary premolars restored with different CAD/CAM all-ceramic restorations].

PURPOSE: This study was to evaluate the fracture resistance of endodontically treated maxillary premolars restored with different CAD/CAM all-ceramic restorations in vitro. METHODS: Mesio-occluso-function tip(MOF) cavities were prepared in 21 extracted human maxillary premolars due to endodontic treatment. The teeth were divided into 3 groups. G1:conventional composite resin; G2: cavities；G3: conventional composite resin with a horizontal glass fiber post inserted palatal walls. Restorations were fabricated from a pressable lithium disilicate glass-ceramic and adhesively cemented (Rely X U200). Then, the specimens were subjected to a compressive load at a crosshead speed of 0.5 mm/min until fracture. The fractured specimens were analyzed to determine the fracture pattern using a stereomicroscope. SPSS 15.0 software package was used to analyse the data. RESULTS: G3（1570.7±108.7） had higher failure load than G1(1214.6±95.8) and G2(1285.9±87.6)(P<0.05). G1 was similar to G2.The crown was lost in G1 and G2. There was a fracture of the crown and tooth in G3. CONCLUSIONS: CAD/CAM all-ceramic crown with fiberglass posts might be an effective method for restoration of endodontically treated premolars with MOF cavity defect.

[Changes of oral bacteria flora after wearing complete denture].

PURPOSE: This study investigateed the influence of complete denture on oral bacteria flora. METHODS: Bateria plaque samples in oral mucosa, saliva and denture surfaces in 11 edentulous patients were collected, then the 16S rRNA gene clone libraries were constructed. Pyrosequencing was used to analyze the 16S rRNA gene V3~V4 regions, oral bacteria flora were classified and identified. RESULTS: There were 64800 sequences in complete denture-wearing subjects, Streptococcus mitis, Gemella haemolysans, Rothia mucilaginosa, Porphyromonas sp, Neisseria zoodegmatis, Granulicatella elegans, Acinetobacter baumannii, Pseudomonas citrinum, Granulicatella adiacens and Fusobacterium canifelinum were the predominant species (37416 sequences). The species of denture tissue surface were similar to these of buccal vestibule after wearing denture, and the species of denture smooth surface were similar to these of tongue ventrum and the floor of mouth. CONCLUSIONS: The effect of complete denture on oral flora is still limited, and the composition of oral flora is influenced by many other factors.

[Comparison of clinical efficacy of CAD/CAM all -ceramic inlay and polymerid porcelain inlay in restoration of posterior Class II cavity].

PURPOSE: To compare the clinical efficacy of CAD/CAM all-ceramic inlay and polymerid porcelain inlay in restoring Class II cavity of posterior teeth. METHODS: Ninety-seven patients with 100 posterior teeth of ClassII cavity were recruited in this randomized control trial; Among them, 50 patients were grouped into CAD/CAM all-ceramic inlays and 47 patients were grouped into Ceramage polymerid porcelain inlay. According to the modified USPHS criteria, the incidence of postoperative sensitivity, prosthesis fracture, prosthesis falling off, and edge coloration were evaluated 12 months and 24 months after restoration. Chi-square test and Wilcoxon rank sum test were used for statistical analysis using SPSS 13.0 software package. RESULTS: Restoration in the 2 groups were successful, there was no significant difference at 12 months (P>0.05). Postoperative sensitivity and the incidence of prosthesis falling off in both groups were not significantly different (P>0.05); however, the number of prosthesis fracture of the polymerid porcelain was lower than that of the CAD/CAM all-ceramic inlays (P<0.05). The incidence of edge coloration of CAD/CAM all-ceramic inlays was lower than that of the polymerid porcelain at 24-month follow-up (P<0.05). CONCLUSIONS: Restoration with polymerid porcelain is more likely to have a higher success rate than those with CAD/CAM all-ceramic inlays. Patients undergoing CAD/CAM all-ceramic inlays have a lower incidence of edge coloration, compared with those undergoing polymerid porcelain.

The effect of Ti anodized nano-foveolae structure on preosteoblast growth and osteogenic gene expression.

The TiO2 nanotubes by anodization have been extensively studied for medical implant and orthopedic applications because of enhancing bone development. In the present study, a new nano-foveolae structure verified by SEM and AFM was prepared by simulating the nanotubes exfoliation from anodized Ti. MC3T3-E1 preosteoblasts were used to investigate the effects of new nanoscale surface on cell spreading, proliferation, and osteogenic gene expression. The new nano-foveolae structure supported preosteoblast better spreading, more filopodiaes shown by SEM (4 h), and lower proliferation (72 h) than the smooth Ti. By two weeks, the new nanoscale surface induced higher expression of osteogenic markers alkaline phosphatase (ALP), osteopontin (OPN), osteocalcin (OCN), and collagen I (COL I) with real-time RT-PCR compared to the control group. The results of this study suggest that the new nano-foveolae structure provides a favorable surface for functions of bone cells.

RGD peptide immobilized on TiO2 nanotubes for increased bone marrow stromal cells adhesion and osteogenic gene expression.

Recently, TiO(2) nanotube layers are widely used in orthopedics and dental applications because of their good promotion effect on bone cells. Furthermore, peptide sequences such as arginine-glycine-aspartic acid are used to modify Ti implant for binding to cell surface integrins through motif. In this study, a cellular adhesive peptide of arginine-glycine-aspartic acid-cysteine (RGDC) was immobilized onto anodized TiO(2) nanotubes on Ti to examine its in vitro responses on rat bone marrow stromal cells (BMSCs). Materials were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy techniques. High-resolution C1s scans suggested the presence of RGDC on the surface and SEM images confirmed the nanotubes were not destroyed after modification. BMSCs adhesion and osteogenic gene expression were detected in TiO(2) nanotube layers with and without RGDC modification by fluorescence microscopy, confocal laser scanning microscopy, SEM, and realtime polymerase chain reaction (Real-time PCR). Results showed that the TiO(2) nanotube layers immobilized with RGDC increased BMSCs adhesion compared to nonfunctionalized nanotubes after 4 h of cultivation. Furthermore, the osteogenic gene expression of BMSCs was dramatically enhanced on the TiO(2) nanotube layers immobilized with RGDC (10 mM) compared to the TiO(2) nanotube layers immobilized with RGDC (1 mM) and non-functionalized anodized Ti. Our results from in vitro study provided evidence that Ti anodized to possess nanotubes and then further functionalized with RGDC should be further studied for the design of better biomedical implant surfaces.

[Influence of TiN, TiCN coating on corrosion resistance of dental pure titanium].

PURPOSE: To investigate the effects of TiN and TiCN coating on corrosion resistance of pure titanium in the simulated oral environment. METHODS: The dental pure titanium commonly used in making removable denture was casted with 15 specimens, 10mm × l0mm × 1mm in size. The specimens were randomly divided into group A, group B and group C. In the group B and group C, the specimens were coated with a thickness of 2.5µm TiN and TiCN coating on surface by multi-arc physical vapor deposition, respectively. After microscopic energy spectrum analysis, microstructure and phase diffraction were examined by FESEM. Hardness and Young modulus of the various coating were determined by nanoindentation. The polarization curves of all specimens in artificial saliva were measured by PARSTAT' 2273 electrochemical station. The data were analyzed with SPSS 17.0 software package for t test, one-way ANOVA and nonparametric test. RESULTS: Both the microhardness and elastic modulus in the group B and group C were significantly superior to those in the group A (P<0.001). Meanwhile, both the microhardness and elastic modulus in the group C were significantly higher than those in the group B (P<0.01). Corrosion potential (Ecorr) was group A > group B > group C (P<0.05). However, corrosion current density (Icorr) was significantly lower in the group A than in the group B, and in the group A than in the group C (P<0.01), while not significantly different between the B and group C (P>0.05).Breakdown potential (Ebreak) was group A

Osteogenic gene expression of canine bone marrow stromal cell and bacterial adhesion on titanium with different nanotubes.

Bacterial infection and osseointegration of implant-biomaterials all play important roles in the success of an orthopedic prosthesis or a dental-implant. In this work, we evaluated the osteogenic gene expression of canine bone marrow stromal cells (CBMSCs) and the adhesion of Staphylococcus aureus (ATCC 12598) on different diameter TiO(2) nanotube layers. The CBMSCs cultured on 30 and 70 nm nanotubes displayed polygon shape, but obviously elongated when the diameter of nanotubes turned to 120 nm. A significant increase in CBMSCs proliferation by as much as about ∼300%, and osteogenic gene (RUNX-2, OPN, COL-1, and OCN) expression were observed on the 120 nm diameter nanotubes when compared to the smooth Ti. However, the adhesion of bacteria also increased with an increased tube diameter and reached highest value on 120 nm nanotubes after 4 h of incubation. ∼300-400% increase in bacterial attached to 120 nm nanotubes in contract to the smooth Ti. These data suggested reducing bacteria colonization should be considered when larger diameter nanotubes with better osteogenic property would be used as orthopedic implants or dental implants.

[Study of corrosion behavior of titanium with anodized oxidation film].

OBJECTIVE: To investigate the variation of the corrosion resistance of anodized oxidation film on titanium by electrochemical methods. METHODS: TiO2 nanotube layer was formed on Ti surface by anodization. The morphology was observed with scanning electron microscope (SEM) and the crystal phase was analyzed using X-ray diffraction(XRD) before and after annealing. Polarization curves were examined by electrochemical methods. RESULTS: Titanium oxide nanotubes with 80 nm diameter and 400 nm length was seen on Ti after anodization. The annealing nanotubes was anatase crystalline phase by X-ray diffraction analysis. The self-corrosion potential and break-down potential of smooth Ti were significantly lower than TiO2 nanotubes by anodization (P < 0.05). The self-corrosion current and passived current were significantly higher than TiO2 nanotubes by anodization (P < 0.05). Annealing improved the corrosion resistance of anodized oxidation film on titanium. CONCLUSION: The results of electrochemical examinations indicate that the TiO2 nanotubes by anodization increases the corrosion resistance of titanium.

In vitro corrosion study of different TiO2 nanotube layers on titanium in solution with serum proteins.

Titanium oxide nanotubes prepared by anodization have received considerable attention in the biomaterials domain. The objective of this study was to demonstrate the electrochemical behavior of different diameter TiO(2) nanotube layers on titanium in phosphate buffered saline (PBS) and Dulbecco's minimum essential medium+10% fetal calf serum (D-FCS) using open circuit potentials (OCP), electrical impedance spectroscopy (EIS), and a potentiodynamic polarization test. The results showed that the nanotubes had higher OCP, higher resistance of the inter barrier layer (R(b)), and lower I(pass) in the two test solutions compared to the smooth Ti, especially the 30 nm diameter nanotubes. The corrosion resistance of the nanotubes in D-FCS was higher than in PBS because of protein adsorption from the D-FCS solution as suggested by scanning electron microscope (SEM) images. In addition, protein aggregates of 30 nm diameter nanotubes caused the model of EIS spectra to transform from two-layer to three-layer. The corrosion behavior of the nanotubes for use as a dental implant material is discussed.

Corrosion behaviour and surface analysis of a Co-Cr and two Ni-Cr dental alloys before and after simulated porcelain firing.

This study evaluated the corrosion behaviour and surface properties of a commercial cobalt-chromium (Co-Cr) alloy and two nickel-chromium (Ni-Cr) alloys [beryllium (Be)-free and Be-containing] before and after a simulated porcelain-firing process. Before porcelain firing, the microstructure, surface composition and hardness, electrochemical corrosion properties, and metal-ion release of as-cast alloy specimens were examined. After firing, similar alloy specimens were examined for the same properties. In both as-cast and fired conditions, the Co-Cr alloy (Wirobond C) showed significantly more resistance to corrosion than the two Ni-Cr alloys. After firing, the corrosion rate of the Be-free Ni-Cr alloy (Stellite N9) increased significantly, which corresponded to a reduction in the levels of Cr, molybdenum (Mo), and Ni in the surface oxides and to a reduction in the thickness of the surface oxide film. The corrosion properties of the Co-Cr alloy and the Be-containing Ni-Cr alloy (ChangPing) were not significantly affected by the firing process. Porcelain firing also changed the microstructure and microhardness values of the alloys, and there were increases in the release of Co and Ni ions, especially for Ni from the Be-free Ni-Cr alloy. Thus, the corrosion rate of the Be-free Ni-Cr alloy increased significantly after porcelain firing, whereas the firing process had little effect on the corrosion susceptibility of the Co-Cr alloy and the Be-containing Ni-Cr alloy.

The effect of anatase TiO2 nanotube layers on MC3T3-E1 preosteoblast adhesion, proliferation, and differentiation.

Titanium oxide nanotube layers by anodization have received considerable attention in biomedical application. Previous studies have demonstrated increased osteoblast (bone-forming cell) adhesion and function on nanotube layers compared with unanodized counterparts. More recently, one study showed amorphous TiO(2) nanotube diameter determined cell fate. The anatase phase is known to be much more beneficial for bone growth than amorphous phase, so there is increasing demand to explore the response of osteoblast on anatase phase TiO(2) nanotube layers. For this reason, we evaluated MC3T3-E1 preosteoblast behavior on different diameter nanotube layers with anatase phase. The results showed that the diameter of 20-70 nm provided an effective length scale for cell adhesion, alkaline phosphatase activity, and mineralization. However, cell adhesion, alkaline phosphatase activity, and mineralization were severely impaired on nanotube layers with 100-120 nm. Interestingly, the filopodia seemed not spread into the nanotubular and like extending anatase nanotube walls, where there may be higher numbers of atoms at the surface compared to the nanotubular architecture. To our surprise, the proliferation rates of cells cultured on anatase nanotube layers increased with increasing tube diameter from 20 to 120 nm, which may be attributed to different length and nanometer-scale roughness of the nanotube layers.

[Corrosion resistance and wear resistance of Ni-Cr alloy after coating titanium nitride (TiN) in oral containing fluorine environment].

PURPOSE: The aim of this study was to evaluate the corrosion resistance and wear resistance of Ni-Cr alloy after coating titanium nitride (TiN) in oral containing fluorine environment. METHODS: Physical vapor deposition was established to coat titanium nitride (TiN) on the surface of dental cast Ni-Cr alloy to form TiN/Ni-Cr compound. Both Ni-Cr alloy and TiN/Ni-Cr compound were exposed to 37 degrees centigrade, artificial saliva containing 0.24% NaF. The polarization curves of the specimens were measured by PARSTAT 2273 electrochemical station to investigate its corrosion resistance. Vicker's hardness was measured by HXD-1000TMC/LCD micro-hardness tester to investigate its wear resistance. Statistical analysis was performed by SAS 8.2 software package for Student's t methods. RESULTS: The corrosion potential of Ni-Cr alloy was -362.407 mV, the corrosion current density was 1.568µAcm(-2),the blunt-breaking potential was 426 mV bofor TiN coating. The corrosion potential of TiN/Ni-Cr compound was -268.638 mV, the corrosion current density was 0.114µAcm(-2),the blunt-breaking potential was 1142 mV after TiN coating. Polarization curves showed TiN/Ni-Cr compound improved the corrosion potential and blunt-breaking potential, decreased the corrosion current density. The Vicker's hardness of Ni-Cr alloy was 519.75±27.27 before TiN coating, the Vicker's hardness of TiN/Ni-Cr compound was 803.24±24.64, the D-value between them was 283.49±39.34. The difference of Vicker's harnesses between Ni-Cr alloy and TiN/Ni-Cr compound had significant (P<0.01). CONCLUSION: The results demonstrate that the TiN coating can improve the corrosion resistant to F-and the surface hardness of Ni-Cr alloy. Supported by Research Fund of Science and Technology Commission of Shanghai Municipality (Grant No.08DZ2271100), Shanghai Leading Academic Discipline Project (Grant No.S30206 ) and Research Fund of Health Bureau of Shanghai Municipality (Grant No.2009074).

Corrosion behaviors of TiO2 nanotube layers on titanium in Hank's solution.

It is well known that the growth of osteoblast cultured on titanium with nanotube layers can be significantly increased compared to unanodized surfaces. In the current study, the corrosion behavior of titanium with nanotube layers was studied in naturally aerated Hank's solution using open circuit potentials (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests. The electrochemical results indicated that TiO2 nanotube layers on titanium showed a better corrosion resistance in simulated biofluid than that of smooth-Ti. The OCP, corrosion rate (I(corr)), passive current density (I(pass)) and the oxygen evolution potential (E(o)) were significantly influenced by titanium oxide nanotube layers acquired by anodization. The anatase nanotube layer showed higher OCP and smaller current density than the amorphous nanotube layer. EIS analysis showed that the annealing had a significant effect on the corrosion resistance of the outer tube layer (R(t)), but little effect on the corrosion resistance of the inter-barrier layer (R(b)) for nanotube layers. The results suggested that titanium with TiO2 nanotube layers has an adequate electrochemical behavior for use as a dental implant material.

[The effect of different dispersive methods on flexural strength nano-ZrO(2) reinforced denture polymethyl methacrylate].

PURPOSE: To study the effect of different dispersive methods on flexural strength of nano-ZrO(2)/polymethl methacrylate(PMMA) composite samples. METHODS: The nanometer ZrO2 particles which were modified by coupling agent Z-6030 were mixed to PMMA as the filler materials (3%) by means of handle disperse, ball milling disperse and ultrasonic wet disperse, respectively. Pure PMMA was used as blank control .With reference to the standard of ISO-1567:1999, standard samples were made and tested by three-point bending test. Then the data of flexural strength of the four groups were analyzed statistically with SAS 6.12 software package for one-way ANOVA(Newman-Keuls test). And the optimized synthesis way of the PMMA composite materials was selected. RESULTS: The flexural strength of the ball milling group and the ultrasonic group were significantly higher than the handle group and blank group(P<0.05), with an increase of 17%,10% compared with the blank group. There was no significant difference between the ball milling group and the ultrasonic group (P>0.05). CONCLUSION: Dispersal ways have effect on the flexural strength of PMMA composite materials which are filled with ZrO(2) particles.

[Fabrication of titanium dioxide nanotube array and effects of its osteoblast proliferation and alkaline phosphatase activity].

OBJECTIVE: To investigate preparation parameters of TiO2 nanotube layer with anodization, and to evaluate the osteoblast activity on TiO2 nanotube layer in vitro. METHODS: Titanium dioxide nanotube layer was grown using anodization method. TiO2 nanotube layers with different structure were obtained by controlling the voltage and time of anodization and rinsing process after anodization. Pure titanium without anodization was used as control. Osteoblasts were cultivated on the anodizated TiO2 nanotube, and the growth of osteoblasts was then evaluated and analyzed. RESULTS: The voltage, duration of anodization and rinsing process following anodization were key factors to affect morphology of TiO2 nanotube layer. The area of osteoblast cultured on TiO2 nanotube layer was larger than that on pure titanium. Results from methylthiazol tetrazolium (MTT) test showed that the proliferation of osteoblasts after 96 h cultivation on TiO2 nanotube layer (0.62 +/- 0.02) was significantly higher than that on unanodizated titanium (0.55 +/- 0.03, P < 0.05). Three weeks later, the alkaline phosphatase (ALP) activity on TiO2 nanotube layer [(130.8 +/- 5.1) A(405)/mg] was significantly higher than that on unanodizated titanium [(109.6 +/- 4.5) A(405)/mg, P < 0.05]. CONCLUSIONS: The structure of TiO2 nanotube layer was greatly associated with anodization voltage. The TiO2 nanotube layer had a positive effect on osteoblast behavior.

[Influence of different amount of silane coupling agent on the flexural strength of PMMA/nanometer ZrO2 composites].

PURPOSE: To study the influence of different amount of silane coupling agent Z-6030 on the flexural strength of PMMA/nanometer ZrO(2) composites. METHODS: Nanometer ZrO(2) particles were modified by silane coupling agent Z-6030 with different percentages.In situ polymerization method was used to combine PMMA/ nanometer ZrO(2) composites of denture base plate. With reference to the standard of ISO1567:1999, standard samples of the experimental group were made. PMMA II type powder and PMMA II type liquor were used,which was not added nanometer ZrO(2) and silane coupling agent to make the standard samples of common denture base plate. PMMA II type powder and PMMA II type liquor were used,which was added nanometer ZrO(2) unmodified by silane coupling agent to make the standard samples of the control group. The data of flexural strength of the base plate materials were tested with three-point bending test. One-way ANOVA was adopted to analyze the data using SAS 6.12 software package. RESULTS: When the percentage of silane coupling agent Z-6030 was 3.5%,the flexural strength of PMMA/nanometer ZrO(2) composite resin material of denture base plate was strongest, which was significantly higher than that of the common denture base plate group,the control group,2.0% group,4.0% group,4.5% group and 5.0% group(P<0.05). 0.5% group,1.0% group,1.5% group,2.5% group,3.0% group and 3.5% group had no significant difference with each other(P>0.05). 0.5% group,1.0% group,1.5% group,2.0% group,2.5% group,3.0% group,4.0% group,4.5% group,5.0% group,the common denture base plate group and the control group had no significant difference with each other(P>0.05). CONCLUSION: Using proper percentage of silane coupling agent Z-6030 can improve the flexural strength of PMMA/nanometer ZrO(2) composite resin material of denture base plate. This study showed that the best range of the percentage of silane coupling agent Z-6030 was 3.5%.

[The influence of the try-in pastes on the colour of all-ceramic veneers].

PURPOSE: To study the influence of the try-in pastes on the color of all-ceramic veneers made by Ips-empress II system. METHODS: 50 discolored teeth were collected and restored with all-ceramic veneers. Five try-in pastes including A1, A3, transleucent(Trt), white opaque(WOT) and B0.5 opaque(B0.5),which were different in shade, were respectively used to try in before cementing. The color was measured by the ShadeEye, a digital colorimeter, and expressed in terms of 3 coordinate values (L*,a*,b*) of the CIEL*a*b* system. Then the color differences(deltaEa*b*) of all-ceramic veneers[deltaEa*b*=(deltaL*(2)+deltaa*(2)+deltab*(2))(1/2)] as well as the value of L*deltaC(ab)[C(ab)=(a*(2)+b*(2))(1/2)] and H(ab)[H(ab)=arctan(b*/a*)]were calculated. Meanwhile,the thickness of the measurement point was measured and recorded. One-way ANOVA was used to analyze deltaEa*b* as well as L*,C(ab) and Hab. RESULTS: The average thickness of the ceramic was 1.088mm, and the colour of the veneers after try in with WOT paste and B0.5 paste performed a higher L* value than the other pastes (P<0.05).And the veneers also showed a higher C(ab) value after try in with WOT,B0.5 and A3 paste than the A1 and Trt paste (P<0.05). No significant differences were found in Hab value after these 50 veneers tried in with these five kinds of pastes. CONCLUSIONS: It's more advisable to choose the WOT or the B0.5 luting agent to cement the veneer when the abutment tooth is severely discolored, while the Trt or the A1 shade and A3 shade luting resin may be more appropriate if the abutment tooth doesn't discolor or a little compared with the adjacent tooth.

[Progress of research on fiber posts].

In the last few decades, casting metal has been the most commonly used post-core systems. But the elastic modulus of metal posts is higher than that of the dentin. Root fractures often happen because of the higher elastic modulus. The fiber posts can reduce or avoid root fractures because their elastic modulus is similar to that of the dentin. Therefore, they are widely used clinically to preserve tooth tissues and restore them after failure. This review article aims to introduce the recent research of the fiber posts.