Oral Frictional Hyperkeratosis (FK)
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
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
FK may be discovered by accident during a routine oral examination..
Photo of Hyperkeratosis affecting the gum / gingiva in the right lower quadrant
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.
Last Updated 26th December 2014

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.

Useful Websites & Article:

Emedicine.com (Dermatology)

Bond's Book of Oral Diseases (4th Edition)  / The Maxillofacial Center for Diagnostics & Research

J Oral Maxillofac Surg 2009.  Morsicatio Mucosae Oris — A Chronic Oral Frictional Keratosis, Not a Leukoplakia