The identification of electronic surveying lines on 3-D digital models of dentition defects / 中华口腔医学杂志

<p><b>OBJECTIVES</b>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.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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.</p><p><b>CONCLUSIONS</b>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.</p>

Single cell gel electrophoresis of a magnesium alloy coated with beta-tricalcium phosphate / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the genotoxicity of a magnesium alloy coated with beta-tricalcium phosphate (beta-TCP).</p><p><b>METHODS</b>Four groups were designed. In the first group, AZ31B magnesium alloy surface was coated with beta-TCP using chemical bath deposition, and in the second group magnesium alloy was tested. The other two groups were negative control (pure titanium) and positive control groups (0.5 mg/L bleomycin). Single cell gel electrophoresis was adopted to investigate genotoxicity of the alloy samples in different groups, and 60 cells from each group were analysed. Tail moment and tail DNA percentage were used as reliable indicators to show DNA damage in lymphocytes induced by every testing sample. Student-Newman-Keuls (SNK) test was used to compare results from 4 groups.</p><p><b>RESULTS</b>There were no significant differences in tail moment and tail DNA percentage between magnesium alloy group [(0.52 +/- 0.12), (6.82 +/- 1.81)%] and magnesium alloy coated with beta-TCP group [(0.51 +/- 0.12), (6.89 +/- 1.93)%, P > 0.05]. Tail moment and tail DNA percentage in negative group were (0.47 +/- 0.14) and (6.29 +/- 1.64)%, and tail moment and tail DNA percentage in positive group were (5.17 +/- 1.23) and (22.09 +/- 4.51)%.</p><p><b>CONCLUSIONS</b>No significant increase was found in DNA damage in lymphocytes induced by magnesium alloy coated with beta-TCP.</p>

Study on the compatibility of yttria-stabilized zirconia framework bonded to the corresponding veneering ceramic / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the bonding properties and interface characterization of a domestic 3mol yttrium-stabilized tetragonal zirconium polycrystal (3Y-TZP) framework fired on with 4 different veneering ceramics for zirconia.</p><p><b>METHODS</b>4 different commercial veneering ceramics for zirconia (VITA VM9, SHOFU VINTAGE ZR, IPS e.max Ceram, Cercon ceram kiss) were sintered on 3Y-TZP rectangulars (15 mmx5 mmx5 mm) according to the manufacturers' instructions for shear bond strength test, a metal-ceramic system(Ni-Cr alloy/VITA VMK95) was fabricated in the same type as a control group. Two bilayered specimens (3Y-TZP/VITA VM9, Ni-Cr/VMK95) were prepared for scanning electron microscope (SEM) and energy distribution spectrum (EDS).</p><p><b>RESULTS</b>The values of shear bond strength test were (18.83 +/- 1.77) MPa for 3Y-TZP/VITA VM9, (23.83 +/- 7.05) MPa for 3Y-TZP/SHOFU VINTAGE ZR, (17.87 +/- 2.30) MPa for 3Y-TZP/IPS e.max Ceram, (22.26 +/- 7.45) MPa for 3Y-TZP/Cercon ceram kiss, (20.55 +/- 5.13) MPa for Ni-Cr alloy/VITA VMK95. There was no statistically significant between all-ceramic groups and the control group (P > 0.05). The failure modes in all-ceramic groups showed predominately adhesive at the interface. SEM showed the 3Y-TZP/VITA VM9 contacted tightly at the interface, while EDS detected Si element diffused into 3Y-TZP material.</p><p><b>CONCLUSION</b>The results indicate that domestic 3Y-TZP has a good interface compatibility with 4 commercial veneering ceramics, as a dental framework material, it can satisfy the clinical requirements.</p>

Influence of fluoride ion-implanted titanium on the formation of focal adhesion plaque in vitro / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the chemical composition of the modified surface of fluoride ion-implanted titanium and assess the effect on the formation of focal adhesion plaque in vitro.</p><p><b>METHODS</b>Pure commercial titanium discs were treated with fluoride ion implantation by plasma immersion ion implantation technique (PIII) and chemical composition and value of the surface modification layer were characterized by X-ray photoelectron spectrometer (XPS). In order to investigate the formation of focal adhesion plaque, MG-63 cells were seeded onto the surfaces of the modified Ti discs and quantified by morphometric analysis using an immunofluorescence microscope.</p><p><b>RESULTS</b>The full range XPS spectra and fitting results indicated that the surface of fluoride ion-implanted titanium was the mixture of titanium dioxide and titanium trifluoride. Meanwhile, the quantity of focal adhesion plaque on fluoride ion-implanted titanium was more than that on the non-implanted titanium after 6 hours' cell culture.</p><p><b>CONCLUSION</b>The XPS data revealed that the modified surface layer of fluoride ion-implanted titanium contained titanium dioxide and titanium trifluoride, which could enhance the formation of focal adhesion plaque.</p>

Computer aided design and computer aided manufacture of sacrificial pattern of removable partial denture framework / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To introduce a method applied in computer aided design and computer aided manufacture (CAD-CAM) of removable partial denture framework for rehabilitating edentulous arch of Kennedy Class II and found a basis for this project.</p><p><b>METHODS</b>Point cloud data of dental stone model was obtained by laser scanning. The following processes were made: drawing framework outline on the reconstructed triangle mesh model, picking up and processing its inner side data as the data of tissue surface, shelling it for 3-D model of framework, and transferring the data to rapid prototyping equipment for manufacture.</p><p><b>RESULTS</b>3-D model of the removable partial denture framework was preliminarily accomplished. The resin framework used as a sacrificial pattern was manufactured with the rapid prototyping equipment. The fit between resin framework and plaster model was good.</p><p><b>CONCLUSIONS</b>This method, as an integrated procedure including data acquisition, 3-D computer modeling and fabrication by rapid prototyping, is feasible to implement CAD-CAM of removable partial denture framework.</p>