Objectives To develop a mathematical algorithm and a software package for the process of electronically surveying a scanned point cloud cast. To provide a principal premise to the subsequent computer aided design and computer aided manufacture (CAD/CAM) of removable partial denture framework, and to provide a method to improve quality control in the dental laboratory. Methods Point cloud data of a partially edentulous cast, a mandibular Kennedy Class Ⅱ Modification 2 arch, was captured using an optical scanning system with projective grating and high-resolution digital camera. Using commercial CAD/CAM software system (Geomagic Studio 6), this point cloud data was processed and the 3-D digital model of partially edentulous cast was reconstructed. From a suggested surveying angle the contour points of height were identified, and then the digital surveying lines were traced using Projection and Contour Extraction software package. The depth of undercut was measured and defined to determine the clasp termination of retainer. Results Electronic surveying line of 3-D digital dentition defect model was achieved. Digital surveying line defined the cast into undercut and non-undercut areas. Different virtualized paths of insertion could be automatically suggested when the cast was surveyed and analyzed from different angles. The depth of undercut was automatically measured and the retentive clasp termination was determined. Conclusions The mathematical algorithm and the software package in this study can be used to survey and analyze 3-D digital models of dentition defects, and to identify an electronic surveying line.

Objective To examine the shear and microtensile bond strength between a newly developed dental machinable composite resin(pelymethylmecrylate/nano SiO2-ZrO2,PNSZ)and dentin cemented using three resin luting systems and to select the most suitable one.nethods The shear and microtensile bond strength between the machinable composite resin and dentin cemented using three resin luting systems(Group A:RelyX ARC,Group B:Panavia-F,Group C:Variolink II)were tested.The broken specimens were observed with a stereomicroscope(×50)to compare their failure modes. Results In the shear tests,no significant difierence was found in bond strength among Group A[(14.07±4.67)MPa],Group B[(13.17±4.63)MPa]and Group C[(12.10±2.18)MPa](P＞0.05).In the microtensile tests,no significant difference was found in bond strength among Group A[(11.49±4.90)MPa],GroupB[(9.66±4.15)MPa].and Group C[(10.11±4.20)MPa](P＞0.05).The failure modes of all the three resin cements were predominantly adhesive failures at the dentin/cement interface.Conclusions The three typos of resin cements showed similar results in bend strength between the dental machinable composite resin and dentin.Bonding at the resin/cement interface was stronger than that at the dentin/cement interface.

Objective To develop a method of three-dimensional computer aided design(CAD)of post-and-core restoration.Methods Two plaster casts with extracted natural teeth were used in this study.The extracted teeth were prepared and scanned using tomography method to obtain three-dimensional digitalized models.According to the basic rules of post-and-core design,posts,cores and cavity surfaces of the teeth were designed using the tools for processing point clouds,curves and surfaces on the forward engineering software of Tanglong pmsthodontic system.Then three-dimensional figures of the final restorations were corrected according to the configurations of anterior teeth,premolars and molars respectively.Results Computer aided design of 14 post-and-core restorations were finished,and good fitness between the restoration and the three-dimensional digital models were obtained.Appropriate retention forms and enough spaces for the full crown restoratiohs can be obtained through this method.Conclusions The CAD of three-dimensional figures of the post-and-cort restorations can fulfill clinical requirements.Therefore they can be used in computer-aided manufacture(CAM)of post-and-core restorations.

Objective To introduce a method of digital modeling and fabricating removable partial denture(RPD) frameworks using self-developed software for RPD design and rapid manufacturing system.Methods The three-dimensional data of two partially dentate dental casts were obtained using a threedimensional crossing section scanner. Self-developed software package for RPD design was used to decide the path of insertion and to design different components of RPD frameworks. The components included occlusal rest, clasp, lingual bar, polymeric retention framework and maxillary major connector. The design procedure for the components was as following: first, determine the outline of the component. Second, build the tissue surface of the component using the scanned data within the outline. Third, preset cross section was used to produce the polished surface. Finally, different RPD components were modeled respectively and connected by minor eonnectors to form an integrated RPD framework. The finished data were imported into a selfdeveloped selective laser melting (SLM) machine and metal frameworks were fabricated directly. Results RPD frameworks for the two scanned dental casts were modeled with this self-developed program and metal RPD frameworks were successfully fabricated using SLM method. The finished metal frameworks fit well on the plaster models. Conclusions The self-developed computer aided design and computer aided manufacture( CAD-CAM ) system for RPD design and fabrication has completely independent intellectual property rights. It provides a new method of manufacturing metal RPD frameworks.

Objective To establish the computer aided design (CAD) software platform of individualized abutment for the maxilla central incisor. MethodsThree-dimentional data of the incisor was collected by scanning and geometric transformation. Data mainly included the occlusal part of the healing abutment, the location carinae of the bedpiece, the occlusal 1/3 part of the artificial gingiva's inner surface,and so on. The all-ceramic crown designed in advanced was "virtual cutback" to get the original data of the abutment's supragingival part. The abutment's in-gum part was designed to simulate the individual natural tooth root. The functions such as "data offset", "bi-rail sweep surface" and "loft surface" were used in the process of CAD. ResultsThe CAD route of the individualized all-ceramic abutment was set up. The functions and application methods were decided and the complete CAD process was realized. Conclusions The software platform was basically set up according to the requests of the dental clinic.

Objective Acute lung injury induced by variety causes can be reduced by mesenchymal stem cells.Some studies have shown that mesenchymal stem cell-derived exosomes have similar features with mesenchymal stem cell,but its role in acute lung injury is less studied.The study was to investigate the protective role and underlying mechanisms of bone marrow mesenchymal stem cell-derived exosomes (BMSC-DEs) on smoke inhalation injury (SⅡ) in rats.Methods Thirty Wistar rats were randomly divided into 3 equal groups:normal control group,smoke inhalation injury (SⅡ) model group and bone marrow mesenchymal stem cell-derived exosomes (BMSC-DEs) treated group.12 h after establishing the SⅡ model,BMSC-DEs treated group was injected with 0.5 mL BMSC-DEs (derived from 4× 106 BMSCs),and normal control group and SⅡ model group were injected with equivalent volume of normal saline.7 days later,samples were collected.The histopathologic changes of lung were observed after HE staining;BCA was used to test the amounts of total protein in bronchoalveolar lavage fluid (BALF);Enzyme linked immunosorbent assay was used to test the levels of tumor necrosis factor-α (TNF-α) and keratinocyte growth factor (KGF) in the lung tissue;Immunohistochemical was used to test the levels of pulmonary surfactant protein C(SP-C).Results The BALF levels of total protein of SⅡ group was significantly higher than those of normal control group (P＜0.01) and BMSC-DEs groups(P＜0.05);Compared with normal group [(0.164±0.021) ng/L],the levels of tumor necrosis factor-α of SII and BMSC-DEs groups [(0.355±0.106)、(0.234±0.024) ng/L] (P＜ 0.05) were significantly higher,and SⅡ group was higher than that of BMSC-DEs group(P＜0.01);Compared with normal group,the KGF protein expression level in lung tissue of SⅡ group was significantly lower (P＜0.05),but BMSC-DEs group was higher (P＜0.05).BMSC-DEs group was higher than SⅡ group (P＜0.01);Immunohistochemistry showed that the SP-C expression level in lung tissue of SⅡ group was significantly lower than those of other groups (P＜0.05).There was no statistically difference between BMSC-DEs group and control group (P＞0.05).Conclusion BMSC-DEs has a protective effect of smoke inhalation injury rats,the underlying mechanism may be related to BMSC-DEs to reduce inflammation and promote restoration of the alveolar epithelial type Ⅱ.

Objective To evaluate the design and manufacture accuracy of a domestic computer aided design(CAD) and computer aided manufacture(CAM) system,and to compare it with similar foreign products.Methods Thirty models of posterior-teeth-single-crown preparations were collected,and STL data of these preparations was collected by Denmark 3Shape scanner.Three copings were made for each preparation,the one designed and manufactured using commercial CAD/CAM system (3Shape CAD software and Wieland T1 CAM equipment) was assigned into control group T0,the one designed and manufactured using domestic CAD software (developed by Peking University School and Hospital of Stomatology and Nanjing University of Aeronautics and Astronautics) and Wieland T1 CAM equipment was assigned into experimental group TCAD for design accuracy evaluation,and the one designed and manufactured using 3Shape CAD software and domestic CAM equipment(developed by Peking University School and Hospital of Stomatology,Tsinghua University and ShanDong XinHua Incorporated Company of medical apparatus and instruments) was assigned into experimental group TCAM for manufacture accuracy evaluation.Finally,the marginal fitness were compared and evaluated by using 3D & Profile measurement microscope laser.Results The marginal fitness of TCAD was 27.98 (19.10,46.57) μm in buccal,32.67 (20.65,50.82) μm in lingual,27.38 (22.53,52.61) μm in mesial,29.50 (22.68,53.65) μm in distal; of TCAM was 21.69(15.87,30.21) μm in buceal,18.51(13.50,22.51) μm in lingual,19.15(15.42,26.89) μm in mesial,22.77(18.58,32.15) μm in distal; and there were no statistical differences compared with T0 [20.16(17.16,48.00) μm in buccal,21.51(17.05,28.31) μm in lingual,23.54(17.89,30.04) μm in mesial and 23.94(17.93,28.19) μm in distal] except lingual data of TCAD.Conclusions The design and machining precision of this domestic CAD/CAM system is at the same level of those comparable foreign products.