Some studies in Australia, Brazil and Germany pointed to alcohol-containing mouthwashes as also being potential causes. The claim was that constant exposure to these alcohol-containing rinses, even in the absence of smoking and drinking, leads to significant increases in the development of oral cancer. However, studies conducted in 1985, 1995, and 2003 summarize that alcohol-containing mouth rinses are not associated with oral cancer. In a March 2009 brief, the American Dental Association said "the available evidence does not support a connection between oral cancer and alcohol-containing mouthrinse". A 2008 study suggests that acetaldehyde (a breakdown product of alcohol) is implicated in oral cancer, but this study specifically focused on abusers of alcohol and made no reference to mouthwash. Any connection between oral cancer and mouthwash is tenuous without further investigation.

In a study of Europeans, smoking and other tobacco use was associated with about 75 percent of oral cancer cases, caused by irritation of the mucous membranes of the mouth from smoke and heat of cigarettes, cigars, and pipes. Tobacco contains over 60 known carcinogens, and the combustion of it, and by-products from this process, is the primary mode of involvement. Use of chewing tobacco or snuff causes irritation from direct contact with the mucous membranes.

Tobacco use in any form by itself, and even more so in combination with heavy alcohol consumption, continues to be an important risk factor for oral cancer. However, due to the current trends in the spread of HPV16, as of early 2011 the virus is now considered the primary causative factor in 63% of newly diagnosed patients.

The annual incidence rates per million for ameloblastomas are 1.96, 1.20, 0.18 and 0.44 for black males, black females, white males and white females respectively. Ameloblastomas account for about one percent of all oral tumors and about 18% of odontogenic tumors. Men and women tend to be equally affected, although women tend to be 4 years younger than men when tumors first occur and tumors appear to be larger in females.

This condition occurs in association with denture wearing, and so those affected tend to be middle aged or older adults. 66-75% are estimated to occur in women. Epulis fissuratum is the third most common reactive lesion that occurs in the mouth, after peripheral giant cell granuloma and pyogenic granuloma.

Recurrence is common, although the recurrence rates for block resection followed by bone graft are lower than those of enucleation and curettage. Follicular variants appear to recur more than plexiform variants. Unicystic tumors recur less frequently than "non-unicystic" tumors. Persistent follow-up examination is essential for managing ameloblastoma. Follow up should occur at regular intervals for at least 10 years. Follow up is important, because 50% of all recurrences occur within 5 years postoperatively. Recurrence within a bone graft (following resection of the original tumor) does occur, but is less common. Seeding to the bone graft is suspected as a cause of recurrence. The recurrences in these cases seem to stem from the soft tissues, especially the adjacent periosteum. Recurrence has been reported to occur as many as 36 years after treatment.

To reduce the likelihood of recurrence within grafted bone, meticulous surgery with attention to the adjacent soft tissues is required.

If the causative factor persists, tissue will become more fibrous over time.

They are more common in males than females, occurring in a ratio of about 5:1. They are strongly associated with the presence of torus mandibularis and torus palatinus.

Immunotherapy with immune checkpoint inhibitors is being investigated in head and neck cancers.

Around 75% of cases are caused by alcohol and tobacco use.

Tobacco smoke is one of the main risk factors for head and neck cancer and one of the most carcinogenic compounds in tobacco smoke is acrylonitrile. (See Tobacco smoking). Acrylonitrile appears to indirectly cause DNA damage by increasing oxidative stress, leading to increased levels of 8-oxo-2'-deoxyguanosine (8-oxo-dG) and formamidopyrimidine in DNA (see image). Both 8-oxo-dG and formamidopyrimidine are mutagenic. DNA glycosylase NEIL1 prevents mutagenesis by 8-oxo-dG and removes formamidopyrimidines from DNA.

However, cigarette smokers have a lifetime increased risk for head and neck cancers that is 5- to 25-fold increased over the general population.

The ex-smoker's risk for squamous cell cancer of the head and neck begins to approach the risk in the general population twenty years after smoking cessation. The high prevalence of tobacco and alcohol use worldwide and the high association of these cancers with these substances makes them ideal targets for enhanced cancer prevention.

Smokeless tobacco is cause of oral and pharyngeal cancers (oropharyngeal cancer). Cigar smoking is an important risk factor for oral cancers as well.

Other environmental carcinogens suspected of being potential causes of head and neck cancer include occupational exposures such as nickel refining, exposure to textile fibers, and woodworking. Use of marijuana, especially while younger, is linked to an increase in squamous-cell carcinoma cases while other studies suggest use is not shown to be associated with oral squamous cell carcinoma, or associated with decreased squamous cell carcinoma.

Congenital epulis is a proliferation of cells most frequently occurring on the alveolar ridge of the upper jaw at birth. Less frequently the mass may arise from the mandibular alveolus. Rare cases can arise from the tongue. This lesion is more commonly found in female babies, suggesting hormonal involvement during embryonic development. The cause of this type of epulis is unknown. Also known as congenital granular cell tumor or Neumann's tumor; historically referred to as granular cell myoblastoma.

Multiple lesions occur in 10% of affected neonates. The tumor is typically pedunculated and varies in maximum size from 0.5 cm to 9 cm. The lesion is typically painless and does not increase in size after discovery. Some small lesions may regress over time. Treatment is surgical excision. Recurrence is extremely rare even after incomplete excision.

Amalgam tattoo is found in up to 1% of people in the general population. It is the most common cause of solitary or focal pigmentation of the oral mucosa.

Epulis (; plural "epulides") is any tumor like enlargement (i.e. lump) situated on the gingival or alveolar mucosa. The word literally means "(growth) on the gingiva", and describes only the location of the mass and has no further implications on the nature of the lesion. There are three types: fibromatous, ossifying and acanthomatous. The related term parulis (commonly called a gumboil) refers to a mass of inflamed granulation tissue at the opening of a draining sinus on the alveolus over (or near to) the root of an infected tooth. Another closely related term is gingival enlargement, which tends to be used where the enlargement is more generalized over the whole gingiva rather than a localized mass.

A study in Sweden showed that 21.5% of smokers and 3% of nonsmokers (genetic pigmentation or unknown cause) had lesions that could be classified as an oral melanin pigmentation. A gingival melanin index in 4 degrees was established. Already with a consumption of 1-3 cigarettes a day 9.3% of all 20.333 examined showed a smoker's melanosis. Pipe smokers had smoker's melanosis in 16.8%. One year after the start of cigarette smoking a clinically visible smoker's melanosis could be seen in 12.3% of women, and 17% among men.

In cigarette smokers who quit smoking, the number of individuals with smoker's melanosis becomes slowly less frequent after 2–3 months, but can still be seen in a few former smokers three years after smoking stop.

Although clinically visible genetic melanin pigmentations in the mouth are present in several ethnic groups all over the world, more mucosal areas will be melanin-pigmentet if tobacco products are used. Smoker's melanosis is found in India, Italy, Japan, Nigeria, Sweden, Turkey, USA, and several other countries.

Smoker's melanosis is expected to be found also in other tissue surfaces exposed to tobacco and tobacco smoke, for instance lips and in skin of the fingers holding the cigarette. Future studies will also show if the use of tobacco exaggerates the pigmentation of skin.

Smoking or the use of nicotine-containing drugs is the cause to Smoker's melanosis. Also tar-components (benzopyrenes) are known to stimulate melanocytes to melanin production, and other unknown toxic agents in tobacco may also be the cause. These chemical agents have a polycyclic, chain-like structure. Environmental tobacco smoke from parents is causing smoker's melanosis in their children Swedish snuff causes a small elevation of oral melanin pigmented individuals from 3.0% to 4.7%. Nicotine tablets have shown to stimulate to melanin pigmentation of the oral mucosa.

PCNA and Ki67 immunoreactivity happens in case of fibroma and peripheral granuloma.

Giant-cell fibroma is a type of fibroma not associated with trauma or irritation. It can occur at any age and on a mucous membrane surface. The most common oral locations are on the gingiva of the mandible, tongue, and palate. It is a localized reactive proliferation of fibrous connective tissue.

Giant-cell fibroma (GCF) is a benign non-neoplastic lesion first described by Weathers and Callihan (1974). It occurs in the first three decades of life and predominates in females (Houston, 1982; Bakos, 1992). Clinically, the GCF presents as an asymptomatic, papillary and pedunculated lesion. The most predominant location is the mandibular gingiva (Houston, 1982; Bakos, 1992). Histologically, the GCF is distinctive, consisting of fibrous connective tissue without inflammation and covered with stratified squamous hyperplastic epithelium. The most characteristic histological feature is the presence of large spindle-shaped and stellate-shaped mononuclear cells and multinucleated cells. These cells occur in a variety of lesions, such as the fibrous papule of the nose, ungual fibroma, acral fibrokeratoma, acral angiofibroma and desmoplastic fibroblastoma (Swan, 1988; Pitt et al., 1993; Karabela-Bouropoulou et al., 1999; Jang et al., 1999).

Despite many studies, the nature of the stellated multinucleate and mononuclear cell is not clear (Weathers and Campbell, 1974; Regezi et al., 1987; Odell et al., 1994; Magnusson and Rasmusson, 1995).

Also termed a "pregnancy tumor" or "granuloma gravidarum", this lesion is identical to a pyogenic granuloma in all respects apart from the fact that it occurs exclusively in pregnant females. There is usually pregnancy gingivitis also. Pregnancy epulis commonly occurs during the third trimester of pregnancy.

Treatment usually involves surgical removal of the lesion down to the bone. If there are any adjacent teeth, they are cleaned thoroughly to remove any possible source of irritation. Recurrence is around 16%.

Generally buccal exostoses require no treatment. However, they may be easily traumatized causing ulceration, or may contribute to periodontal disease if they become too large, or can interfere with wearing a denture (false teeth). If they are creating problems, they are generally removed with a simple surgical procedure under local anesthetic.

Depending on the pet's unique condition, there are several treatment options, including surgery, chemotherapy and radiation therapy. Treating the pain adequately is also of crucial importance to improve the pet's quality of life, especially if amputation is not performed.

This type of gingival enlargement is sometimes termed "drug induced gingival enlargement" or "drug influenced gingival enlargement", abbreviated to "DIGO". Gingival enlargement may also be associated with the administration of three different classes of drugs, all producing a similar response: Gingival overgrowth is a common side effect of phenytoin, termed "Phenytoin-induced gingival overgrowth" (PIGO).

- anticonvulsants (such as phenytoin, phenobarbital, lamotrigine, vigabatrin, ethosuximide, topiramate and primidone NOT common for valproate)

- calcium channel blockers (antihypertensives such as nifedipine, amlodipine, and verapamil). The dihydropyridine derivative isradipidine can replace nifedipine and does not induce gingival overgrowth.

- cyclosporine, an immunosuppresant.

Of all cases of DIGO, about 50% are attributed to phenytoin, 30% to cyclosporins and the remaining 10-20% to calcium channel blockers.

Drug-induced enlargement has been associated with a patient's genetic predisposition, and its association with inflammation is debated. Some investigators assert that underlying inflammation is necessary for the development of drug-induced enlargement, while others purport that the existing enlargement induced by the drug effect compounds plaque retention, thus furthering the tissue response. Careful attention to oral hygiene may reduce the severity of gingival hyperplasia. In most cases, discontinuing the culprit drug resolves the hyperplasia.

The most common bone tumor is called osteosarcoma, and typically affects middle-age to older dogs of large and giant breeds. Osteosarcoma is less common in cats. Osteosarcoma is an aggressive cancer that can develop in any bone of the body but the majority is seen in the limbs (e.g. long bones such as radius, humerus, femur, and tibia).

It is commonly seen in Boxer dogs and other brachycephalic breeds, and in the English Springer Spaniel. It usually starts around middle age and progresses. Some areas of the gingiva can become quite large but have only a small attachment to the rest of the gingiva, and it may completely cover the teeth. Infection and inflammation of the gingiva is common with this condition. Under anesthesia, the enlarged areas of gingiva can be cut back with a scalpel blade or CO laser, but it often recurs. Gingival enlargement is also a potential sequela of gingivitis. As in humans, it may be seen as a side effect to the use of ciclosporin.

This variation of normal anatomy is seen in the majority of adults. It is estimated about 80% of people have oral Fordyce spots, but seldom are granules found in large numbers. They are not usually visible in children, and tend to appear at about age 3, then increasing during puberty and become more obvious in later adulthood. They are more prominent in males.

All cases reported appear to represent sporadic occurrence. There is no specific inheritance pattern. The male-to-female ratio of affected is 1.8:1 and is often diagnosed before the age of 9. The disorder affects the right and left sides of the maxilla almost equally.