A Method for Additive Manufacturing of Functionally Graded Dental Crowns

Abstract

Leucite containing ceramic has been proven in past research to have increased abrasive wear resistance in dental composites when compared to commercially available dental composite materials. Using this material as a basis for manufacturability, the additive manufacturing (AM) method of vat photopolymerization (VP) was selected. Functional grading was also incorporated into the manufacturing process to better represent the natural tooth structure. The effect of incorporating functionally graded additive manufacturing (FGAM) into the manufacturing process of a dental crown will result in an internal structure that more closely resembles that of a natural tooth.

The traditional layer-based method of AM technologies poses several challenges for functional grading. This research effort is the first to develop a new method in the form of shellbased manufacturing, since commercially available slicing software is incapable of producing shell-based manufacturing g-code. The focus of this thesis addresses this issue and details a program that collects layer-based g-code and converts the data into shell-based g-code. The program utilizes the g-code produced by slicing software when given an .STL file of a crown geometry, and coverts that g-code into separate and unique g-codes for each shell. After extracting X and Y coordinate data from the original g-code, an algorithm creates concentric regions bounded by the interior and exterior walls of each layer. The concentric regions become the basis for each shell, and the newly created coordinate data is converted into separate and unique g-code for each shell.

The objective of this research is to develop a methodology for the FGAM of dental crowns. VP is the best AM technique because of its high resolution and accuracy, which is necessary for the production of small and complex geometry like those found in dental crowns. However, the AM method of fused deposition modeling (FDM) is used to prove the concept of converting layerbased g-code to shell-based g-code due to current machine availability. To resolve the issues of resolution and accuracy, the crown geometry was scaled 500%. Four separate shells were created using FDM, which proves the concept that layer-based g-code can be converted to separate shellbased g-code.