Objective:To investigate the accuracy of pure titanium and cobalt-chromium alloy frameworks fabricated using the additive manufacturing (AM) of selective laser melting technology (SLM) for the mandibular implant-supported fixed prostheses and the maxillary removable partial denture (RPD), and to provide a reference for clinical application of SLM pure titanium frameworks.Methods:One edentulous mandibular model with implants and screw fixed abutments at bilateral canines and the first molars was selected and used as the mandibular full arch implant-supported model. At the same time, a Kennedy class Ⅰ maxillary dentition defect model was selected. The digital models were obtained by scanning the dental models, and the metal frameworks of the mandibular full arch implant-supported denture and the maxillary RPD (design model) were designed using the 3 Shape software. Meanwhile, 12 mandibular frameworks in the cobalt-chromium alloy and the pure titanium (6 in each group were treated with heat treatment, while the other 6 were not treated), and 7 maxillary frameworks in the cobalt-chromium alloy and the pure titanium were respectively made by SLM with the improved dual-laser metal printer. The axial direction of the printing powder accumulation was taken as the Z-axis. During the design process, the software (3Shape Dental System 2018) automatically generated the X-axis and Y-axis, X axis was the sagittal axis of the dental model and Y axis was the coronal axis of the dental model. The deviation of the interface center of the abutment of the digital model of the mandibular frameworks from the design model in the X, Y and Z axes was analyzed. As for the trueness of the mandibular framework, the larger the deviation data was, the worse the trueness was. The deviation of the whole maxillary framework and 7 measuring points (palatal plate center point and bilateral occlusal rests, I bars, proximal plates) were analyzed. The fitness of the whole maxillary framework to the design model was expressed by root mean square (RMS) of the deviation data, and the fitness of measuring points was expressed by the mean±standard deviation of the data. The trueness differences of each group before and after heat treatment of the mandibular framework and the fitness of the maxillary framework were compared.Results:The cobalt-chromium alloy frameworks showed lower trueness on the X, Y, Z-axes [(96.3±12.1), (86.3±11.4), (61.2±13.2) μm] than did the pure Ti frameworks [(82.3±11.2), (72.2±10.2), (51.2±11.6) μm] by SLM, and the heat treatment could reduce the discrepancy between the SLM frameworks and STL models, for pure titanium frameworks [(62.4±11.3), (55.2±13.2), (41.3±10.8) μm] and for cobalt-chromium alloy [(84.5±10.5), (72.3±11.2), (54.2±11.6) μm]. For the thin RPD major frameworks, pure titanium had better fitness [(121.3±17.0) μm] than cobalt-chromium alloy [(174.0±18.3) μm] by SLM, and the difference was statistically significant ( P<0.05). Conclusions:Pure titanium frameworks fabricated by SLM additive manufacturing technology exhibited better fitness and trueness than did the Co-Cr frameworks after heat treatment respectively, and this satisfied the requirements of implant-supported fixed prostheses and RPD major metal frameworks.

Objective : To evaluate the effect of different surface treatments on the bonding strength between highly translucent zirconia and veneering porcelain and to provide a research basis for improving the zirconium porcelain bond strength between zirconium and ceramic material. Methods : Thirty cylindrical zirconia blocks with 10-mm diameter and 10-mm height were prepared and divided into four groups (n=7), labeled as control group (C), sandblasting group (S), bonding group (B), and sandblasting and bonding group (SB). The surface morphology of zirconia before and after sandblasting was observed in the remaining two specimens. Group C was veneered (2 mm in height and 5 mm in diameter) with porcelain powder by layering after grinding. Group S was sandblasted after grinding. Group B was veneered with a thin layer of porcelain powder as bond coating. Group SB was sandblasted and veneered with a thin layer of porcelain powder. After sintering, the shear specimens were embedded, and a shear bond strength test was conducted. Statistical analysis was conducted to analyze the data. Fracture surface analysis was also performed to determine the failure modes by stereomicroscopy. Results : The bonding strength of group C was 21.86 ± 3.18 MPa. For group S, it was 22.12 ± 3.06 MPa. For group B, it was 19.19 ± 1.46 MPa. Finally, for group SB, it was 27.76 ± 1.95 MPa. There was no significant difference in shear strength between group C, group S and group B. There was a significant difference in shear strength between each group and group SB (P < 0.05). Under a stereomicroscope, the observed fracture modes of each group were mainly mixed failure. Conclusion Sandblasting cannot significantly increase the bonding strength between zirconia and veneering porcelain. Veneering with a thin layer of porcelain powder as the bond coating has no obvious effect on the bonding strength. Sandblasting and veneering with a thin layer of porcelain powder as a bond coating can significantly improve the bonding strength between zirconia and veneering porcelain.

OBJECTIVE To establish a method for simultan eous determination of 5 kinds of pentacyclic triterpenoids as 3-O- acetyl-pomolic acid in Chaenomeles speciosa ，and to analyze the difference in the contents of C. speciosa from different producing areas by different processing technologies . METHODS HPLC method was adopted . The determination was performed on COSMOSIL 5 C18-MS-Ⅱ column with mobile phase consisted of acetonitrile -0.005 mol/L ammonium dihydrogen phosphate solution （pH value adjusted to 6.5 with phosphoric acid ）（70∶30，V/V）at the flow rate of 1.0 mL/min. The column temperature was set at 30 ℃. The detection wavelength was set at 210 nm，and sample size was 20 μL. The contents of the other four pentacyclic triterpenoids were calculated according to quantitative analysis of multi -components by single -marker（QAMS）using oleanolic acid as internal reference . The results were compared with those determined by external standard method . The total content of oleanolic acid and ursolic acid ，the total content of 5 components in C. speciosa from different producing areas and different processing technologies were compared . RESULTS The linear range of 3-O-acetyl-pomolic acid ，betulinic acid ，oleanolic acid ，ursolic acid and 3-O-acetyl ursolic acid were 4.06-81.2，2.12-42.4，9.62-192.3，7.77-155.4，4.21-84.1 μg/mL，respectively（R2＞0.999）. RSDs of precision ，reproducibility and stability （24 h）tests were all lower than 3%. The average recoveries were 98.29%-101.38% （RSDs＜3%，n＝6）. The mass fraction of 3-O-acetyl-pomolic acid ，betulinic acid ，ursolic acid and 3-O-acetyl ursolic acid measured by QAMS w ere 0.023%-0.060%，0.044%-0.528%，0.101%-0.368%，0.067%-0.221%，respectively；the deviations from the results measured by external standard method were all within 8%. The total content of oleanolic acid and ursolic acid， the total content of 5 components in C. speciosa processed by fresh -cut technology from the same producing area were higher than those in C. speciosa processed by traditional technology ，and the total content of 5 components in C. speciosa from Chongqing Qianjiang were significantly higher than those from other producing areas （P＜0.05）. CONCLUSIONS QAMS method is established for the simultaneous determination of 3-O-acetyl-pomolic acid ，betulinic acid ，oleanolic acid ，ursolic acid and 3-O-acetyl ursolic acid in C. speciosa. Established method is simple ，rapid and accurate . The total content of 5 components in C. speciosa produced in Chongqing Qianjiang is higher ，and the total content of C. speciosa processed by fresh -cut technology from the same origin is higher than C. speciosa processed by traditional technology .