Numerical Simulation Of The Casting Process Of Titanium Denture Frameworks

Objective:This study was aiming at optimizing the sprue designs for the casting of titanium removable patial denture frameworks by studying the filling and solidfication process with the help of numerical simulation technology.Comparing the filling incompleteness and porosity defects in different sprue systems,a sound design was to be proposed for clinical use. Material and Method: A titanium RPD framework was fabricated.Geometry of this framework was laser-digitized and converted into a CAD software (UniGraphics) to construct a digital model,which was respectively attached with one of the four sprue systems (tree,ball,taper and runner-bar) later.After defining the initial and boundary conditions for specific titanium,both mold filling and solidification of the castings with different sprue designs were numerically simulated with a casting simulation commercial software ProCAST.Result:Numerical models of titanium RPD frameworks were achieved.The characteristics of these 3D images were clear and accurate. The mold filling process is dramatically short,completed in 0.2~0.4s.Two incompletenesses of the clasps occurred in tree type and ball type sprues,while no obvious filling defect was detected in taper type and bar type sprues.All the four sprues meetedthe directional solidification principle in the solidifying sequence of the frameworks.Shrikage porosities were confined in the sprues except for the tree type sprue,under which porosity occurred in the framework itself. Conclusion:Sprue designs play an important role in the casting quality control,which result in different filling completeness and porosity defects.Taper type and bar type sprue designs can produce sound casting results for titanium RPD frameworks.