What tooth resorption (TR) is
In TR, specialised cells (odontoclasts) break down tooth tissue. The process often starts at the neck of the tooth, where the crown meets the gum, and may extend into the root. The tooth loses its normal structure and can become painful to touch.
TR is most often diagnosed in cats. Resorption also occurs in dogs, but much less often and may have different features. The cause is not fully understood; the process progresses, and there is currently no preventive method that reliably stops it.
Stages and types of TR — what owners should know
Under the AVDC classification, TR is assessed by stage (1–5) according to lesion depth, and by type: type 1 — the root retains normal radiographic structure; type 2 — the root is replaced by bone-like tissue; type 3 — a combination of both patterns.
In early stages there may be only a faint red line at the gum. Later the tooth can look "worn", the crown may fracture, and gingiva may grow over the lesion. What owners see externally does not show the full picture — radiographs show how deep the process has gone.
- Stage 1 — mild loss of hard tooth tissue
- Stage 2 — lesion extends into dentine but does not reach the pulp cavity
- Stage 3 — lesion reaches the pulp cavity, but most of the tooth remains intact
- Stage 4 — most of the tooth structure is lost
- Stage 5 — remnants of hard tissue are seen radiographically and are fully covered by gingiva
How TR shows up day to day
Classic signs: a cat may keep eating but chew on one side, suddenly pull the head back, drop food or show jaw trembling; also avoid dry food, drool, or avoid touch to the face. I regularly see cats that eat normally and only have mild bad breath — yet under anaesthesia several affected teeth are found.
Reduced grooming, especially of the face, is another signal. The cat may lick less or stop grooming properly because jaw movement and touching the mouth are painful.
Why radiographs are essential
TR cannot be reliably diagnosed by external examination alone. Under anaesthesia I examine and probe every tooth, assess the gums and visible defects, and dental radiographs help determine stage, resorption type and root status.
Sometimes a tooth looks normal while dental radiographs may show resorptive changes of the root. Sometimes the crown is badly affected and radiographs help plan extraction. Without full-mouth dental radiography it is possible to miss affected teeth and underestimate sources of dental pain.
Why a cat may still eat when a tooth hurts
Cats are skilled at masking pain. Hunger and feeding habits often outweigh discomfort. The cat adapts: chooses soft food, eats on one side, swallows pieces with less biting or food manipulation. Owners see a "normal appetite" and postpone the visit.
At consultation I always ask about details: has the food changed, does the cat refuse treats, does it avoid touch to the face. These details often matter more than overall appetite.
How treatment is chosen
Treatment depends on the clinical findings and radiographic type of resorption. Lesions that have not entered the oral cavity may be monitored clinically and radiographically. Clinically significant lesions are generally treated by extraction. Crown amputation is reserved for selected radiographically confirmed type 2 lesions that meet strict clinical criteria — without endodontic or periodontal disease and without caudal stomatitis. Restoring or sealing TR defects is not indicated.
Full dental diagnostics in my practice include dental radiography, because some pathology cannot be seen on a conscious exam. Extraction decisions are made only after assessing the films. The goal is to remove pain and inflammation, not to "save at any cost" a tooth that no longer functions. After extraction cats usually adapt well and eat normally.
- Lesion not communicating with the oral cavity — individual monitoring
- Clinically significant lesions — tooth extraction
- Type 2 resorption meeting strict radiographic criteria — crown amputation may be considered
Prevention and monitoring
There is no prevention that reliably stops TR from developing. Home brushing with a veterinary toothpaste reduces plaque and improves overall oral health, but it does not stop TR.
How often to repeat dental assessment and radiographs is decided individually, based on age, previous findings, symptoms and risk of progression. If TR has already been diagnosed in one tooth, other teeth are more likely to be affected over time, so monitoring matters. Dental radiography remains essential when comprehensive diagnostics are clinically indicated.
What to do if you suspect TR
Book a consultation with a veterinary dentist. At that visit I assess what is visible without anaesthesia, discuss symptoms and plan a full examination with radiography. Do not wait for obvious symptoms or further tooth destruction.
Do not try to treat pain with antibiotics or painkillers without a diagnosis. They may temporarily mask symptoms but do not stop the tooth from breaking down.
When to see a vet
- The cat suddenly pulls the head back or stops mid-meal, chews on one side, or avoids dry food
- Worn, darkened teeth or a red line near the gum are noticeable
- Persistent bad breath, drooling, or avoiding touch to the face
- Grooming of the face has reduced
- TR was diagnosed before — a follow-up examination is needed
What not to do at home
- Don't assume "worn" teeth are just a sign of ageing without an examination
- Don't delay a visit because appetite seems "normal" — pain can be hidden
- Don't treat symptoms with antibiotics without a diagnosis
- Don't force the mouth open to inspect teeth — it hurts the cat and does not give a full picture
- Don't expect toothbrushing to cure TR
Frequently asked questions
FORL is an outdated name for the same condition. The modern AVDC term is tooth resorption (TR). In clinical practice I use TR.
Tooth resorption is most commonly discussed in cats, but it also occurs in dogs. The types of lesions, possible causes and treatment approach may differ, so dental radiographs are required for diagnosis.
For clinically significant lesions, extraction is the primary treatment. Crown amputation is considered only for radiographically confirmed type 2 resorption without endodontic or periodontal disease and without caudal stomatitis. The decision follows examination and dental radiographs.
Yes — most cats adapt well. Many owners notice the cat eats even better once pain is removed.
The interval for repeat dental assessment and radiographs is decided individually based on age, previous findings, symptoms and risk of progression.
Brushing with a veterinary toothpaste helps overall oral health but does not stop TR. Dental radiography remains essential when comprehensive diagnostics are clinically indicated.
Sources and professional guidelines
- AVDC: Tooth ResorptionКласифікація резорбції зубів (TR) за стадіями та типами
- AVDC NomenclatureНоменклатура та термінологія AVDC
- WSAVA Global Dental GuidelinesГлобальні настанови з ветеринарної стоматології
- AAHA Dental Care Guidelines for Dogs and CatsКлінічні настанови з дентального догляду