Had dental work today. Took two aleve (naproxen) afterwards at 1pm and two more at 5pm. At 930 pm my head is pounding. Can I take an ibuprofen 800 now?

Yes, you can. However, if you need additional pain relief, you can combine aleve with Tylenol (acetaminophen) . Always talk to your doctor before combining any medications.
No... Aleve and Ibuprofen are the same type of drug...NSAIDS. By taking them together you effectively are overdosing. Tylenol (acetaminophen) is a different type of drug and can be taken concurrently and may have a synergistic effect. .
Pounding Head. Aleve (naproxen) is usually a very safe product for short periods. When you take 2 aleve (naproxen) you effective taking a prescription dose of Naprosyn, the first use of this chemical introduces 20 years ago. Is your head ache in the area of your dental care? Is it on the side of the dental care? Consult your dentist!!