Salivary gland aplasia (also termed salivary gland agenesis) is the congenital absence of salivary glands. Usually the term relates to the absence of some or all of the major salivary glands.

It is a rare condition, and most known cases have been in association with syndromes of the ectodermal tissues, particularly the lacrimal apparatus. Example syndromes which have been reported with salivary gland aplasia include hereditary ectodermal dysplasia, mandibulofacial dysostosis and hemifacial microsomia.

The main significance of the condition is a lack of saliva, causing xerostomia (dry mouth), with accompanying susceptibility to dental caries (tooth decay), infections of the mouth, and upper respiratory tract infections (e.g., candidiasis, ascending sialadenitis, laryngitis and pharyngitis). Patients with salivary gland aplasia typically require regular application of topical fluoride to prevent tooth decay.

Salivary gland hypoplasia is relative underdevelopment of the Salivary glands. Salivary gland hypoplasia tends to produce xerostomia (dry mouth), with all the associated problems this brings.

It is a rare condition, which may occur as a congenital abnormality or result from lack of neuromuscular stimulation.

It may be associated with Melkersson–Rosenthal syndrome, and hereditary ectodermal dysplasia.

Infections involving the salivary glands can be viral or bacterial (or rarely fungal).

- Mumps is the most common viral sialadenitis. It usually occurs in children, and there is preauricular pain (pain felt in front of the ear), swelling of the parotid, fever, chills, and headaches.

- Bacterial sialadentitis is usually caused by ascending organisms from the oral cavity. Risk factors include reduced salivary flow rate.

- Human immunodeficiency virus-associated salivary gland disease (HIV-SGD).

A salivary diverticulum (plural "diverticuli") is a small pouch or out-pocketing of the duct system of a major salivary gland. Such diverticuli typically cause pooling of saliva and recurrent sialadenitis, especially parotitis. A diverticulum may also cause a sialolith to form.

The condition can be diagnosed by sialography. Affected individuals may "milk" the salivary gland to encourage flow of saliva through the duct.

Stafne defect is uncommon, and has been reported to develop anywhere between the ages of 11 and 30 years old, (although the defect is developmental, it does not seem to be present form birth, implying that the lesion develops at a later age). Usually the defect is unilateral (on one side only) and most commonly occurs in men.

The exact cause of the condition is unknown. There is most evidence to support vascular infarction and ischemic necrosis of salivary gland lobules as a mechanism for the condition. Experimentally, local anaesthetic injections and tying of the arteries is reported to trigger the development of tissue changes similar to NS in lab rats. Factors which are thought to cause this ischemia are listed below, however sometimes there is no evident predisposing factor or initiating event.

- Trauma e.g. during intubation, or surgical procedures

- Local anesthetic injection

- Smoking

- Alcohol

- Diabetes mellitus

- Vascular disease, (e.g. arteriosclerosis)

- Pressure from a dental prosthesis

- Allergy

- Bulimia

- Infection

- Ionizing radiation

Salivary gland hyperplasia is hyperplasia of the terminal duct of salivary glands.

There are two types:

- Acinar adenomatoid hyperplasia

- Ductal adenomatoid hyperplasia

Ectopic salivary gland tissue which is located in sites other than the normal location is variously described as aberrant, accessory, ectopic, heterotopic or salivary gland choristoma.

The condition is rare.

The typical age range of those affected by the condition is about 23–66 years of age. It usually occurs in smokers. The male to female ratio has been reported as 1.95:1, and 2.31:1.

Standard, and most effective, therapy to date is glandular sialadenectomy, which is associated with fairly low operative morbidity; however, in recent times, the administration of steroid (which can shrink the inflammatory lesion and is known to reduce serum IgG4 values) has been considered favorably, and may be useful in younger patients or those who refuse surgery.

The cause and pathogenesis of this chronic condition are not very well understood. Several factors have been postulated:

- Formation of a hard salivary calculus or sialolith by accumulation of calcium salts in the duct of the salivary gland (a process known as Sialolithiasis). This has been proposed as the most common cause for Küttner's tumor of the submandibular gland, with sialoliths observed in an appreciable proportion of cases. However, sialolith involvement may not be found in many cases.

- Abnormalities of the salivary gland ducts leading to excessive accumulation or retention of ductal secretions, which can excite chronic inflammations.

- Immune, especially autoimmune, cause - which has gained steam, given the observation that the tissue of the glands is overrun with lymphoid immune cells and fibrous connective tissue, as well as corroboration from markedly similar lesions (with histologic and immunohistochemical findings) seen elsewhere in the body. The presence of abundant Immunoglobulin G4 (IgG4) associated with Plasma cells infiltrating into the salivary glands, as well as increased serum IgG4 concentration, has been noted with patients with Küttner's tumor.

This chronic condition is primarily observed in adult (40–70 years) patients. However, Küttner's tumor, with prominent immunopathological features, has been described in an 11-year-old boy in Brazil in 2012.

Sclerosing polycystic adenosis is a rare, reactive inflammatory condition of the salivary glands. It may be mistaken for salivary gland neoplasia. It does not seem to be a fatal disease.

The prevalence of salivary stones in the general population is about 1.2% according to post mortem studies, but the prevalence of salivary stones which cause symptoms is about 0.45% in the general population. Sialolithiasis accounts for about 50% of all disease occurring in major salivary glands, and for about 66% of all obstructive salivary gland diseases. Salivary gland stones are twice as common in males as in females. The most common age range in which they occur is between 30 and 60, and they are uncommon in children.

The Stafne defect is thought to be caused by an ectopic portion of the submandibular salivary gland which causes the bone of the lingual cortical plate to remodel. Rarely, the defect can be completely surrounded by bone, and this has been theorized to be the result of entrapment of embyonic salivary gland tissue within the bone. Similar, but rarer, defects may be present in the anterior portion of the lingual surface of the mandible. These are not termed Stafne defects which specifically refers to the posterior location. The anterior defects may be associated with the sublingual salivary gland.

Occurs in adults, with peak incidence from 20–40 years of age. A causal link with cytomegalovirus (CMV) has been strongly implicated in a 2011 research.

Generally, there is a good prognosis for low-grade tumors, and a poor prognosis for high-grade tumors.

An "accessory salivary gland" is ectopic salivary gland tissue with a salivary gland duct system. The most common location of accessory salivary gland tissue is an extra major salivary gland in front of the parotid gland. It is typically about 3 cm or less in size, and drains into the parotid duct via a single tributary. Accessory parotid tissue is found in 21-56% of adults. Any disease process which affects the salivary glands, including cancer, may also occur within an accessory salivary gland tissue.

Salivary gland atresia is congenital blockage or absence of the orifice of a major salivary gland duct or part of the duct itself.

It is a very rare condition. The submandibular salivary gland duct is usually involved, having failed to cannulate during embryological development. The condition first becomes apparent in the first few days after birth where a submandibular swelling caused by a retention cyst is noticed.

This is a rare condition, probably caused by an allergic reaction, in which there is sudden swelling of the salivary glands. It is associated with other allergic conditions such as asthma, urticaria, allergic rhinitis and food allergy.

Little is known about the total incidence of salivary gland tumours as most benign tumours go unrecorded in national cancer registries. The majority of salivary tumours are benign (65-70%). Within the parotid gland 75 - 80% of tumours are benign. Around 50% of the tumours found in the submandibular glands are benign. Sublingual gland tumours are very rare but if present, they are most likely to be malignant.

In the United States, salivary gland cancers are uncommon with an incidence rate of 1.7 in 100000 between 2009 and 2013.

Gingival cyst of adult is a rare condition. The incidence is less than 0.5%. It is formed from the rests of dental lamina. It is found in the soft tissues on the buccal and labial portions of the jaw. It usually occurs on the facial gingiva as a single small flesh colored swelling, sometimes with a bluish hue due to the cystic fluid. Sometimes, it may occur in cluster, either unilaterally or bilaterally or on the lingual surface of the alveolar process. It is most commonly seen in the canine and premolar regions of the mandible, and are sometimes confused with lateral periodontal cysts. It is not normally problematic, but when it grows larger, it can cause some discomfort. It can be removed by simple surgical excision. They are developed late in life, generally up to the sixth decade of age.

The lesion is usually present in children. Ranulas are the most common pathologic lesion associated with the sublingual glands.

In one report, about 20% of individuals with mealtime syndrome had strictures upon sialography. For unknown reasons, strictures seem to be more common in females.

Treatment may include the following:

- Surgery with or without radiation

- Radiotherapy

Fast neutron therapy has been used successfully to treat salivary gland tumors, and has shown to be significantly more effective than photons in studies treating unresectable salivary gland tumors.

- Chemotherapy

They generally have a good prognosis. In one larger study, the 5-year and 10-year survival were over 90% and 80% respectively.