## 4 Discussion
### Properties of 3D-Printed Materials for Maxillofacial Prosthesis
Resins used in 3D printing differ significantly in nature from medical-grade silicones, and further studies are needed to fully understand their suitability for maxillofacial prosthetics. The latest PolyJet 3D printers offer advanced multi-material capabilities, enabling precise reproduction of skin consistency and color through voxel-level pigmentation, achieved by jetting drops as small as 40 picoliters. In contrast, silicone 3D printing is evolving towards multi-material applications, with innovations such as pre-nozzle extruders allowing the use of multiple silicone consistencies within a single piece. However, silicone 3D printing still lags behind PolyJet technology in terms of detail reproduction, with a minimum drop size that limits precision and necessitates skilled post-processing. While silicone 3D printing can achieve a layer thickness of 0.4 mm, PolyJet resin printers are \begin{table}
\begin{tabular}{l l} \hline \hline
**Author(s), Year** & **Provided Material Properties** \\ \hline [PERSON] et al. (2023) [10] & Minimum marginal thickness 0.4 mm greater than conventional silicon (below 0.1 mm). \\ [PERSON] et al. (2022) [12] & Shore hardness of approximately 80 A; \\  & Layer thickness of 14-micron (0.014 mm). \\  & Shore hardness of approximately 20 A; \\ [PERSON] et al. (2022) [35] & Elastic modulus for each studied group between 0.39 and 0.46 MPa. \\ [PERSON] et al. (2021) [13] & Variable Shore hardness grades: prosthesis bulk (60 A), \\  & concha (40 A), and lobula (20 A). \\  & Shore hardness of 26 to 28 A; \\ [PERSON] et al. (2019) [16] & Tensile strength of 0.8 to 1.5 MPa; \\  & Near resistance of 2 to 4 kg/cm (19.61 to 39.23 N/cm). \\ [PERSON] et al. (2018) [15] & Shore hardness of 40 A; \\  & Layer thickness of 0.4 mm. \\  & Depending on formulation, \\  & Shore hardness between 19.7 \(\pm\) 0.52 and 22.2 \(\pm\) 0.9 A; \\  & Near strength between 1.587 \(\pm\) 0.11 and 7.057 \(\pm\) 0.98 kN\({}^{-1}\); \\  & Tensile Strength between 1.217 \(\pm\) 0.15 and 4.297 \(\pm\) 0.22 MPa. \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Material’s mechanical properties. capable of printing with a much finer resolution of 0.014 mm, making them more suitable for intricate detail reproduction [12]. Despite these advantages, one major limitation of PolyJet Matrix technology in maxillofacial prosthetics is its susceptibility to UV-induced degradation. Studies have demonstrated that prolonged exposure to ultraviolet (UV) light can lead to color instability, particularly yellowing and fading, affecting the aesthetic longevity of printed prostheses [1]. This issue is also present in conventionally manufactured prostheses [31]. Additionally,opolymer-based materials used in PolyJet printing may undergo surface embrittlement and polymer degradation over time, resulting in reduced mechanical properties, such as lower tensile strength and increased brittleness [2; 8]. Another potential concern is dimensional stability, as UV-induced post-polymerization shrinkage may lead to shape alterations, affecting prosthesis fit and function [50]. These challenges highlight the need for long-term studies evaluating UV resistance, material durability, and strategies to enhance the photostability of PolyJet-printed maxillofacial prostheses. Future research should explore UV-resistant coatings, stabilizing additives, and alternative resin formulations to mitigate the effects of environmental exposure and improve clinical viability. Both materials are advancing towards the integration of multi-functional additives, enabling tailored properties for specific applications [52; 53]. This includes biocompatible and antibacterial formulations for direct 3D printing, which reduces reliance on post-processing while improving clinical outcomes [54]. Further research is needed to optimize these enhancements for long-term performance in clinical environments.