Dental question: is it ok to use neem in toothpaste?

No: First of all use only a pea sized portion of toothpaste that has the ADA seal on the package which says the product actually does what it says on the packaging. Adding tree oil may interfere with some of the toothpaste's properties. Concern that prolonged use, beyond 6 weeks, may cause kidney damage. No good scientific articles affirming effectiveness. I would not encourage its use.