The antonyms for the term "fixed bridges" can be various, depending on the context. If we are talking about dental procedures, then the antonyms can be removable bridges, dentures, or implants. In the context of infrastructure, the antonyms can be floating bridges, suspension bridges, or cable-stayed bridges. In terms of flexibility and mobility, the antonyms can be rigid, immovable, or invariable. When it comes to the opposite of the term's purpose, the antonyms can be broken bridges, missing bridges, or unmaintained bridges. Regardless of the context, the antonyms for fixed bridges all share a common trait of being the polar opposite of what is considered as stable, steady, and permanent.