Objectives: Additive manufacturing is gaining impact in the field of maxillofacial prosthetics due to the possibility to fabricate cost-reduced, personalized and geometrically complex objects [1-3]. 3D-printed polyvinyl alcohol (PVA) could have a significant impact on the creation of molds for production of maxillofacial prostheses. The 3D scanned limb is printed as a prosthesis prototype for final matching by the anaplastologist to the patient. The adjusted prototype is used to produce a mold for the conventional casting of definitive soft tissue prosthesis. The main advantage of this process is the fact that the adjusted pattern made of PVA can be easily dissolved in water within the mold. However, little information is provided about mechanical stability and quality of 3D printed PVA objects.
The aim of this work is to ascertain the mechanical properties of PVA objects printed with a RepRap industrial 3D printer (Kühling&Kühling, Kiel, Germany) and establish a protocol to print with consistent quality.
Material and Methods: A protocol was developed to print PVA in layer thickness of 0.1 mm and rectangular infill patterns at 45° angles with 50% density. Flexural strength and Young’s modulus was determined according to print direction (X, Y, Z) and object position by three-point flexural tests of 15 samples per print direction. The fracture surfaces were inspected with regard to pores and textures by electron microscopy.
Results: Average results of objects printed in the X-direction were 95.62 N/mm2 ±2.95 N/mm2 in flexural strength and 1879.77 N/mm2 ±83.83 N/mm2 for Young’s modulus. Lower values were measured in the Y-direction: flexural strength was 80.98 N/mm2 ±7.43 N/mm2 and Young’s modulus was 1702.48 N/mm2 ±134.19 N/mm2. In the Z-direction values were as low as 12.85 N/mm2 ±2.46 N/mm2 for flexural strength and 701.32 N/mm2 ±228.57 N/mm2 Young’s modulus. Mean values were statistically different on a p=0.05 level (ANOVA, Post Hoc Tukey HSD). No statistical differences were found according to the objects’ position on the printbed.
Conclusion: This experiment showed anisotropic characteristics of PVA objects fabricated by fused deposition modelling. The low values in Z-direction indicate poor layer-to-layer adhesions.