Our sinus and the nerves relaying pain from our teeth are intimately connected. Sinuses are air filled cavities inside the human skull, with small draining openings. When one develops a sinus infection (sinusitis) these small opening can be obstructed leading to the accumulation of the pus inside the sinus. The pressure of the fluid can lead to a throbbing tooth pain which is referred to, as a sinus toothache, since there is nothing wrong with the teeth. Sinus toothache feels much like common toothache and in some cases it is difficult, to rule out a tooth related ache. But if the pain is relieved by treating the sinusitis and relieving the pressure in the sinus cavities, it is a good indication that the teeth are well.