Degradation of Silicone Rubber Causes Provox 2 Voice Prosthesis Malfunctioning

Objective/Hypothesis. Provox 2 voice prosthesis requires periodic replacement due to biofilm proliferation which causes malfunctioning of the valve. The aim of this study was to show that Provox 2 voice prosthesis malfunctioning is due not only to valve obstruction caused by biofilm but also to the silicone variations. Design Methods. Prospective study on the malfunction of Provox2 voice prostheses. Methods. Through photographic and electron microscopic assessment, the authors studied nine Provox 2 voice prostheses, which were removed due to malfunctioning. Results. Findings revealed that the silicone undergoes a degenerative process, thus causing the surface to become rough, deformed, swollen, and translucent. Furthermore, electron microscopy confirmed the presence of immune system cells and biofilm on the prosthesis surface and their role in creating a structural nonhomogenous structure in the silicone, which is deformed due to the presence of "crests" caused by material degeneration. Conclusion. The degenerative process of the silicone seems to be related to the oxygen present in the trachea and esophagus and to the production of oxygen-free radicals on the biofilm's part and the immune system.