Investigation of the Effects of Photopolymer Resin Composition on the Mechanical Properties of Complex Dental Constructs, Fabricated Using Digital Light Processing
Authors: Raines Regan , Salary Roozbeh (Ross) 
Published: February 2023

Abstract
The overarching goal of this research work is to fabricate mechanically robust, dimensionally accurate, and porous dental structures, potentially used for the treatment of dental fractures, anomalies, as well as structural deformities with a focus on oral and maxillofacial surgery applications. In pursuit of this goal, the objective of the work is to investigate the mechanical properties of dental constructs, composed of medical-grade photopolymer resins and fabricated using digital light processing (DLP) process. The fabricated dental constructs not only are porous, but also have complex microstructures imparted by triply periodic minimal surface (TPMS) designs. This study tests the following central hypothesis: the mechanical properties of DLP-fabricated dental structures are significantly affected by photopolymer resin composition. In addition, the following research question is answered in this study: which of the chosen medical-grade photopolymer resins has the most significant impact on the mechanical properties of fabricated dental structures. DLP is a vat-photopolymerization additive manufacturing process, which has emerged as a high-resolution, robust method for the fabrication of a broad range of biological tissues and constructs for oral and dental tissue engineering applications. In the DLP process, the printing process takes place on the basis of radiation-curable resins or liquid photopolymers. Upon exposure to UV light, the resin materials become a solid (via chemical transformation) through a process known as photopolymerization. The DLP process consists of several parameters (such as layer thickness, cure depth, and UV lamp intensity) that significantly influence the functional properties of fabricated dental structures. In spite of the advantages and engendered applications, DLP is inherently complex; the complexity of the DLP process, to a great extent, stems from complex physio-chemical phenomena (such as UV light photopolymerization) in addition to resin (photopolymer)-process interactions, which may adversely affect not only the surface morphology, but also the mechanical properties and ultimately the functional characteristics of the fabricated dental scaffolds. As a result, integrated physics-guided process and material characterization would be required for optimal fabrication of porous and complex dental structures. Particularly in this study, the influence of three medical-grade photopolymer resins on the compression properties as well as the dimensional accuracy of TPMS dental constructs is systematically investigated. The compression properties of the DLP-fabricated dental constructs are measured using a compression testing machine. Furthermore, the dimensional accuracy of the dental constructs is measured via physical measurements and with the aid of a laser scanner. Besides, analysis of variance (ANOVA) is utilized to identify statistically significant photopolymer resin(s). The outcomes of this study pave the way for high-resolution fabrication of complex and porous dental structures with tunable medical and functional properties.