Yes. The last three or four teeth in the upper jaw have roots that are in close relationship to the floor of the maxillary sinuses. It is not uncommon for patients with chronic sinusitis to have pain radiate into the maxillary teeth. Likewise, patients with dental problems in the maxillary teeth that lie in close contact with the floor of the sinus can refer pain to the sinuses.
Yes. The roots of the upper molars can go up into the sinuses. When the lining of the sinus is inflamed the roots can also be inflamed causing pain.
Yes. The "upper teeth" or mandibular teeth.. Not just molars are just under the maxillary sinus cavity. An infection of the sinuses can cause tooth pain. In fact i ask my patients with sinusitis if they have tooth pain as a symptom. However, severe tooth pain could also be a dental infection... Best to get both checked out.