Welcome, sapacif on the Gauge.
Yep, already years ago I used toothpaste for lapping (polishing) gears, first when I raced slot cars, then for breaking in N scale locos. This really worked fine, and the rise in performance was outstanding in some cases.
However, I'd like to add two remarks - warnings, if you like. I found out the hard way!
1. Use toothpaste only for metal gears (brass or steel, both are ok). Plastic gears either show no significant improvement - or they are destroyed.

(Ok, this was years back - perhaps todays plastics are better. If you want to try it, be VERY careful!)
2. After running in the gears (I never ran them longer than 3 minutes), C-L-E-A-N those gears meticulously! If you leave only traces of the toothpaste on the gears, you'll end up with no gear teeth at all.
(Once I did a sloppy cleaning job, and after perhaps two hours running time, an ATLAS loco began to sound strangely. She stood there, full power on, whining and vibrating. And when I inspected her, the gear teeth simply had been chewed away by that abrasive stuff.

) If you have access to an ultrasonic cleaner - use it!
Ron
PS: As far as I understand, 'Pearl Drops' is simply a liquid toothpaste which contains some bleaching agent to get those whiter-than-white teeth, like this -->
