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What is Oral Frictional Hyperkeratosis (FK)?

Hyperkeratinisation – excessive growth of stubbornly attached keratin (a fibrous protein produced by the body) – may happen for a number of reasons and may be genetic (runs in the family), physiological (normal bodily response to certain stimuli), pre-cancerous and cancerous. The change may result from chemical, heat or physical irritants. It is not known to be infectious.

Friction (the constant rubbing of two surfaces against each other) in the mouth may result in white patches.

Various names have been used to describe particular examples of Frictional Hyperkeratosis (FK), including those resulting from excessive tooth-brushing force (toothbrush keratosis), the constant rubbing of the tongue against the teeth (tongue-thrust keratosis), and that produced by the habit of chronic cheek or lip biting (cheek or lip-bite keratosis).

What are the signs and symptoms of FK?

Most patients with FK are free of symptoms. A patient may notice a thickening of an area of skin in the mouth or FK may be discovered by accident during a routine oral examination..

What are the causes of FK?

The white patches of FK that develop in the mouth are formed in the same way that calluses form on the skin of hands and feet. The most common causes are long-term tissue chewing (biting the inside of the cheek or lips), ill-fitting dentures, jagged teeth, poorly adapted dental fillings or caps, and constant chewing on jaws that have no teeth. The constant irritation encourages the growth of keratin, giving the skin involved a different thickness and colour.

Occasionally, an FK may develop as a result of the constant rubbing of a tobacco pipe, musical instrument, orthodontic brace, or perhaps a workman’s tool, which is held in the mouth for convenience. These sorts of factors can be picked up by the doctor or dentist asking the right questions.

White patches associated with smoking can be difficult to distinguish from FK but it is important to identify the cause, as treatment is quite different for each condition.

FK can be successfully treated by removing the frictional element – correcting ill-fitting dentures, fillings, crowns, jagged teeth etc.