Feline Odontoclastic Resorptive Lesions
Feline Odontoclastic Resorptive Lesion or FORLs used to be known as Neck Lesions or Cat Cavities.
FORL's are VERY common - according to one survey 72% of cats over the age of 5 years will have one or more FORL's.
The following series of diagrams tries to give you some information about the development of FORL's - starting with a healthy tooth.
FORL's are the subject of a great deal of research - the exact cause (or aetiology) is uncertain, which is why treatment can be such a problem.
The earliest sign of a potential problem is often the development of gingivitis around the teeth.
Gingivitis is often a response to plaque accumulation. Plaque is made up of living and dead bacteria, together with other organic matter. It appears very quickly in the mouth and can only be controlled by scrupulous oral hygiene.
One theory about the formation of FORL's relates to an unusual response to the plaque bacteria by the inflammatory cells.
There is loss of an area of enamel and the inflammed gingiva moves in to fill the space.
At this stage the lesions do not appear particularly painful - however the gums often bleed when touched with a cotton bud.
It is important to note that the tooth destruction is an active process - not simply rotting (like in caries). The tooth is actively destroyed by the cats own cells.
To prove that the development of FORL's is not simply a direct local reaction to plaque - some of them form from the inside of the tooth.
The cells that "eat away" at the tooth structure are called odontoclasts and sometimes they become active on the inside of the pulp chamber. The tooth substance is destroyed from the inside.
These can be difficult to diagnose. The tooth may appear pinker than usual at the area of the lesion - but a definitive diagnosis really requires x-rays.
The destruction of the tooth has proceeded - dentine as well as the enamel has been affected.
As dentine contains nerve endings it is not surprising that these lesions now become really quite painful. Cats can "judder" their jaws when faced with eating hot or cold food. They sometimes also do this when the lesions are touched with a cotton bud - as well as show obvious pain by trying to get away. They can sometimes be head shy and resent handling, occasionally they go off their food - or are reluctant to eat dry foods.
The pulp chamber is now affected (if it didn't already have an internal resorptive lesion present).
Teeth in this state can remain in the jaw for months. Obviously they are very painful - there is direct connection to the dental nerves. In addition there is a very real likelihood of tooth root abscesses developing as infection can pass down the pulp chamber.
X-Rays are often vital in properly diagnosing FORL's. They can show up lesions inside the teeth - also they can be used to examine a jaw with apparently no teeth present - but which may well have retained tooth roots.
Destruction of the tooth continues.
The tooth structure continues to be eaten away - either by extension of the original FORL, or from new ones on the other side of the tooth.
The tooth continues to be painful throughout this process.
Loss of the Crown
Eventually the tooth destruction is so advanced that the tooth crown will fall off.
You will probably not see this small piece of ivory - it is often swallowed.
The inflammed gum knits together over the retained tooth root.There is a range of possible outcomes - the following two slides show the two extreme positions.
Ankylosis & Resorption of the Root
The inflammed gingiva settles down. The body's defence mechanisms manage to clear any infection. The tooth roots start to become integrated into the jaw bone (ankylosis). Over time further resorption of the tooth root and ingrowth of the jaw bone occurs.
The infection and inflammation continues. Tooth root abscesses are common and sinus tracts may discharge out onto the gums under the lips.
The mouth continues to be painful and cats resent having their heads held, or their mouths examined.
If many teeth are affected a generalised inflammation of the mouth (stomatitis) can occur.
Most cats seem to end up with a combination of the last two pages. However it seems that most cats with retained roots do experience some on-going problems. Equally in most cats with Gingivitis-Stomatitis syndrome radiographs reveal retained roots in the jaw.
It is imperative that FORL's are properly investigated and treated - and this does mean dental radiographs.
Did You Know?
Using a disclosing solution can demonstrate how much plaque is present in even a seemingly healthy mouth.