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Resorptive Lesions



Cats get an unusual dental disease.  It's not cavities.  It's not periodontal disease.  It is a condition which happens very rarely to dogs or people, but which is quite common in cats.  We're talking about Resorptive Lesions  (but we'll call them RL's for short from now on).  They used to be called FORL's, which is short for Feline Odontoclastic Resorptive Lesion.  The veterinary dental guru's now just call them Resorptive Lesions, or RL's,  because as our understanding of them progressed, we found that the odontoclasts weren't such a big part of it after all.  I guess the key point here is that while we as veterinary dentists are very familiar with what Resorptive Lesions look like, we really are just in the investigative stages as far as understanding what causes them.

What is an RL?  An RL is a hole in the tooth.  While there are some important differences between RL's in cats and the cavities we have all had, there are many similarities.  A cavity is a hole in the tooth.No Description  In the picture of a human tooth below, the cavity is the brown spot visible at 9:00.  Cavities are caused by decay.  Bacteria in the mouth feed off sugars, and ferment them to make acids, which eat away the protective enamel.

Once the cavity gets through the hard enemel, it begins to attack the softer, sensitive dentin underneath.  It is at this point that the tooth becomes painful.  As the cavity progresses, it erodes through the dentin into the pulp of the tooth.  The exposed pulp then become infected, and abcessNo Description resized to 300 pixels widees form at the tooth roots.The x-ray to the right is of a cavity in a human tooth.  The cavity istelf is the dark "hole" seen in the right half of the tooth.


Cavities are caused by bacteria and happen from the outside in.  RL's are caused by some as-yet undetermined process, likely involving either the cat's own immune system or a defect in vitamin D metabolism, or maybe both, and happen from the inside out.  But the net effect is the same.  In the picture below, we see the teeth in the bottom jaw of a cat.  Notice how red and inflammed the gums are.  The redness is worse around the tooth on the right.  An x-ray of these same teeth is posted beside the photograph.

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Like the cavity, the RL is seen as a darker spot in the tooth.  In this case, the RL is located on the left root of the righthand-most tooth.  Notice the similarity to the cavity in the human tooth shown above.

Like cavities, once there is a hole leading from the sensitive dentin to the outside, the tooth becomes very painful.  How painful is it?  The answer is very painful.  Most cats with RL's will exhibit teeth-chattering when the RL's are touched even lightly with even a Q-tip.  Basically, the tooth is so painful that merely touching it with a soft object will send the cat into jaw spasms of pain.  Your cat may not show many other signs of pain, however.  This does not mean that the cat does not feel pain. Click Here for a more detailed discussion about how to tell if your cat is in pain.

The Treatment of Choice for RL's is Extraction.  It does no good to put a filling in an RL.  The erosive process that caused them in the first place will dissolve the tooth out from around the filling, and the filling will simply fall out.  While it may seem a bit extreme to extract a tooth with an RL, just consider the alternative:  Living daily with a very painful tooth.

There are things to know about extracting teeth with RL's.    Look again at the radiograph of the cat tooth with an RL.  This time observe the roots closely.  You wil note that the smallest tooth has roots that seem No Descriptionblurry or indistinct when compared to the roots of the neighboring teeth.  This is because the roots are starting to be resorbed too.  The tooth as a whole is undergoing a disease process, and not only is there a hole eaten away from the crown, the roots are becoming weak and brittle.  If weak and brittle weren't enough, the roots also become cemented into the jaw bone.

This means that teeth with RL's can be very difficult to extract.  The roots tend to shatter and fragment, making it difficult to get the whole root.  It is in general a bad idea to leave root fragments in place because they are often infected, and retained root tips can continue to No Description resized to 300 pixels widebe painful. 

The radiograph at the left shows another cat with two retained root tips.  One is easily visible, and the second is barely visible just to the left of the obvious one.  There is a fairly obvious dark halo around the root tip we can easily see.  This halo is caused by infection in the retained root tip.  Infection trapped deep in this buried root tip is eating away the bone at the tip of the retained root, causing the dark halo.





It takes a lot delicate work using the proper techniques and the right instruments to safely and completely remove RL teeth.  RL teeth must be removed surgically.  In a surgical extraction, the gums are cut, moved out of the way, the tooth is cut carefully into pieces, some of the overlying bone is removed, and the tooth is gently removed.  Then you MUST take post-extraction x-rays to be sure you got all the root tips.  Then the gums are sewn back into place.  Because this can be a very lengthy, delicate procedure, treating your cat's RL's can be fairly expensive.

Most cats develop RL's in more than one tooth.  It is quite common to have to extract many teeth at a time.  Sometimes all the teeth must be reomoved.  However, once the healing process is over, the cats are much happier without all those painful teeth.

No DescriptionRL's  are a common and very painful dental condition in cats.  Many cats suffer years in silence with very painful teeth.  Treating RL's is not simple, but your cat will definitely thank you for the relief!