[Doodle bug7]

This is something that I found and not my opinion either way.

I am rather surprised that the neurologist can make a statement like this.
The cause of trigeminal neuralgia is generally not known (though some theories float around). However, it is clear that the vast majority of times the problem starts fairly close to the ganglion, or within the ganglion--almost certainly within the cranial cavity.
Trigeminal neuralgia is known to have "trigger points" that are at quite some distance from the ganglion. It seems far more likely that the galvanic charge stimulated a trigger that was always there.
Now, that doesn't mean that the charge was unrelated to the continued symptoms, since once sensitized, these pathways are thought to require less stimulation to continue the pain, and this is likely what happened to you.
In any case, unless the electrode actually touched the metal restorative material, I see no reason that it would have any influence on the transmission of electrical charge through the skin to the nerve trunk in question. It was almost certainly soft tissue conduction, and probably would have happened to predisposed persons whether dental restorations were present or not.