Does a tongue ring lead to more dental plaque?

No, but...: The presence of a tongue ring does not generally contribute to the accumulation of additional dental plaque on the teeth. However, it does raise the risk of tongue infection, sensitivity reactions to the ring in contacting tissues, and chipping of the teeth, especially the lower front teeth, which are particularly difficult to repair well. Tongue rings are not good for oral health.

Other issues: That is what you should not be worrying about. There are other much more serious issues that should concern you. The ring constantly rubbing against your gum tissue will lead to recession, bone loss and possibly losing a tooth/teeth. I have seen many instances of people biting on their tongue ring and fracturing their teeth. Some had to be extracted. In addition it is more prone to infection.

No...: ...But it does give it more places to hide and build-up.