# A concurrent bioceramic colloid design for dental crowns additive manufacturing by vat photopolymerization

## TL;DR

This paper introduces a new method for 3D printing dental crowns using bioceramic colloids, reducing waste and cost compared to traditional subtractive methods.

## Contribution

The novel approach reuses waste bioceramic powder from subtractive manufacturing to create a hybrid ceramic colloid for additive manufacturing.

## Key findings

- The characterized powder has an average particle size of 91 nm and a tetragonal crystalline structure.
- Optimum ceramic colloid is achieved at 1% wt of ceramic powder and a layer thickness of 25 microns.
- Additively manufactured parts show good homogeneity and lower cost than subtractive methods.

## Abstract

The subtractive manufacturing of bioceramic dental crowns is standard in the dental sector. Still, it is accompanied by many demerits such as raw material waste, tool wear, high cost, and difficulty in handling complex geometry. Researchers direct their efforts toward additive manufacturing due to its capability to produce products with complex geometry and low material waste. This research aims to develop a concurrent engineering approach based on waste minimization of bioceramic powder extracted from subtractive manufacturing and reuse it as a raw material mixed with a polymer resin and a dispersing agent under an indirect mixing strategy to form a hybrid ceramic colloid for bioceramic additive manufacturing. Our approach consists of six stages: raw powder characterization in which particle size, material compositions, crystalline structure, and unit cell dimensions are determined; ceramic colloid design in which ceramic colloid performance based on layer thickness, ceramic powder vol% is optimized using fuzzy-entropy and fuzzy-topsis methods; indirect mixing strategy; 3d printing of the sample; green part characterization, and manufacturing cost estimation. The characterized powder has an average particle size of 91 nm, the majority of its crystalline structure is in the tetragonal phase with unit cell dimensions in angstrom of 'a' that is equal to 3.59 and ‘c’ that is equal to 5.16, the optimum bioceramic colloid is achieved at 1% wt of ceramic powder and a layer thickness of 25 microns with an average stability of 30.2 mv. The ceramic colloid is fed into a 3d printer, and the ceramic part is additively manufactured with good homogeneity and much lower cost than subtractive manufactured dental crowns. The ceramic-colloid stability, homogeneity, and layer thickness control are good indicators of the success or failure of the additively manufactured parts.