Nowadays, personalized medical implants are frequently produced through additive manufacturing. As all medical devices have to undergo specific washing and sterilization before application, the effects of a predefined cleaning routine that is available to the clinical institutes, washing with chemical agent and formaldehyde fumigation, on the mechanical behavior of printed parts are examined. Mechanical properties of parts manufactured by fused filament fabrication (FFF) and ARBURG plastic freeforming (APF) using two poly(methyl methacrylate) (PMMA)-based materials, 3Diakon and CYROLITE MD H12, respectively, are analyzed using flexural and impact tests. An influence of cleaning treatments on the mechanical properties of APF samples is not detected. FFF samples, however, show lower impact strength after washing, but not after sterilization. The fracture surfaces, porosity values, or chemical structure assessed by Fourier-transform infrared (FTIR) spectroscopy could not explain this decrease. Influence of the cleaning treatments on the material itself is assessed using thin compression-molded specimens. The influence on the stress–strain curves is negligible, apart from a slight but significant reduction in the yield stress. FTIR spectroscopy and scanning electron microscopy analyses of the fracture surfaces do not show detectable differences among differentially treated samples.