Oral Frictional Hyperkeratosis (FK)
What is Oral Frictional Hyperkeratosis (FK)?

Hyperkeratinisation - excessive growth of stubbornly
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 (
), 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

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
may be discovered by accident during a routine oral
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
Last Updated 26th December 2014
In most patients with FK, the cause can be easily identified.  A habit of cheek-
biting, chewing or tongue thrusting can usually be identified as the responsible
irritant if the site of the white patch is examined in careful relationship to the level
at which the teeth meet, a broken denture or a jagged tooth surface.

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