Three main pairs of salivary glands are: the submandibular glands under the jaw, the sublingual glands under the tongue, and the parotid glands in front of the ears. In submandibular gland, the most common reason for surgery is when there's a blockage. This can happen if a stone forms in the duct of the gland and other simple treatments don'''t work. For the parotid glands, surgery might be needed for a few reasons. There could be tumours, usually not cancerous but sometimes cancerous. Other reasons include long-lasting infections and swelling that doesn't get better with normal treatments. In rare cases, surgery might be needed to control too much saliva coming from the parotid gland.