Why do my upper front teeth always ache?

Depends: It could be tooth/nose/ or sinus related. Your dentist can check for cavities and/or cysts. If ok see your ent.

Occlusion?: They way you bite together may be causing you some discomfort and may be causing damage. Other issues may be need for root canal or just a good cleaning. Trauma to the area can cause aches as well. Best thing is to have them examined by a dentist.