Modeling the investment casting of a titanium crown

Area of Science:

• Materials Science
• Biomaterials Engineering
• Computational Modeling

Background:

• Titanium dental castings require precise design to avoid mechanical property degradation due to mold contamination.
• Understanding the interplay between casting process parameters and material properties is crucial for high-quality dental restorations.

Purpose of the Study:

• To develop and validate computational modeling tools for designing titanium dental castings.
• To predict the impact of mold contamination on mechanical properties and casting defects.
• To analyze macro- and micro-defects in investment cast titanium tooth crowns.

Main Methods:

• Investment casting of commercial purity grade 1 (CP-1) titanium dental crowns.
• Analysis using X-ray microtomography (XMT), optical microscopy, scanning electron microscopy, and microhardness testing.
• Coupling cellular-automata solidification and finite-difference diffusion programs with commercial casting software.
• Utilizing 3D digital images for accurate geometric representation and incorporating impurity transport.

Main Results:

• Macroscale modeling accurately predicted internal porosity (shrinkage pores) in thick sections.
• Combined micro- and macroscale modeling qualitatively predicted microstructure and contamination depth.
• A surprising result showed silicon dissolution from the mold depressed the titanium's freezing point, causing subsurface solidification.

Conclusions:

• A validated multiscale model can minimize macro- and micro-defects in CP-Ti dental castings.
• Silicon contamination from the mold significantly affects titanium's solidification and surface properties.
• Reducing silicon in mold materials is a valid approach for improving titanium casting finishability.