| Dentition defect is a common oral disease in clinic.It refers to the condition that a number of teeth are missing in the maxillary or mandibular dentition,while some natural teeth are still remaining.Dentition defect has impact on mastication,pronunciation and aesthetics,in the long term,it may also damage the stomatognathic system and affect the health of the whole body.In clinical practice,removable partial denture(RPD)is widely used because of its extensive indications and economic efficiency.Especially,the RPD of titanium metal stent has the advantages of good biocompatibility,excellent mechanical properties and comfortable taste and so on.The traditional manufacturing method of RPD is lost-wax technique.With the development of computer-aided design/computer-aided manufacture(CAD/CAM)in the field of prosthodontics,RPD metal frameworks are made by digital technology increasingly.Among them,Computer numerical control(CNC)cutting is a mature technology and has been widely used in oral removable dentures.At the same time,Selective laser melting technology is developing rapidly in the field of metal processing,such as metal crown,fixed bridge,implant guide plate and so on,which puts forward more possibilities for the processing and manufacture of all kinds of oral restoration.Objective: Titanium scaffolds were made by using three processes: 3D printing embedded wax and lost-wax technique,CNC cutting and selective laser melting.The accuracy and suitability of titanium stents were evaluated,and the advantages and disadvantages of various methods were discussed.Methods: A standard maxillary Kennedy ? class defect of gypsum model was choosed as the reference model,24 impressions of the master cast were made and divided into 3 groups: casting group(n = 8),CNC group(n = 8)and SLM group(n =8).The casting group was used as the control group,the CNC group and the SLM group as the experimental group.1.Three-dimensional optical scanner was used to scan each group supports toobtain point cloud data and save it in a Standard Language Triangle(STL)format.Imported the point cloud data and the CAD data of the stents into Geomagic Qualify2013 software,the CAD of the stents were set as Test,scanned data was set as Reference,and performed 3D deviation analysis after the optimal fit alignment to compare the accuracy of each group of specimens.2.The plaster models with a silicone rubber membrane were acquired,scaned the plaster models with a three-dimensional optical scanner to obtain theirs point cloud datas,and output the datas in STL format.Imported the point cloud data together with the scanned data of the reference model into Geomagic Qualify 2013 software,performed the 3D deviation analysis after the optimal fit alignment,and calculated the film thickness.3.X-ray images of each group of specimens were obtained by X-ray nondestructive inspection,the morphology was observed by SEM,and checked the defects in each group of specimens.Datas were imported into SPSS 21.0 for statistical analysis.Results: 1.The casting and the CNC group had better stability in the accuracy of titanium frameworks,while the SLM group had significantly lower accuracy than the casting group and the CNC group.2.There was no significant difference in the suitability of titanium frameworks between the casting and the CNC group,but the titanium frameworks in the SLM group was significantly lower than that of the other two groups.Among them,the suitability of RPD titanium rest and major connector: there was no significant difference between the casting and the CNC group,and the SLM group was significantly lower than the casting and the CNC group.There was no significant difference in the adjacent panel areas.3.X-ray nondestructive inspection showed that the RPD titanium scaffolds in the CNC and SLM group were relatively uniform,with no obvious internal defects.Different number of bubbles were found in the casting group and different parts,which were significantly different from the other two groups.Under electron microscope,the structure of CNC group was uniform,but that of casting group and SLM group was not uniform.Conclusion: From the point of view of the accuracy,suitability and internal structure of titanium stents,the result of CNC cutting titanium stents are better among the three processing methods,which can be preferred in clinic apply. |
PDF Full Text Request