Dog Gum Disease Stages: Grades 1 to 4 Explained

Veterinary dentists grade canine periodontal disease in four stages, running from grade 1 (inflamed gums with no loss of attachment) to grade 4 (more than half of a tooth's supporting bone destroyed). If your dog has red or bleeding gums, a loose tooth, a swollen face, a draining sore below an eye or sudden reluctance to eat, book a veterinary exam, because staging is a diagnosis made tooth by tooth in the clinic and cannot be read off a photograph.

The scheme most practices use is the periodontal disease staging published by the American Veterinary Dental College. The single most useful thing to understand before you read a dental chart is that the grade belongs to a tooth, not to a dog. A six-year-old terrier can carry grade 1 gingivitis on the incisors and grade 4 disease on one upper fourth premolar on the same day. Searches for "dog dental disease levels", "dog periodontal disease grades" and "dog dental disease grading" all point at this same four-step scale.

The four grades at a glance

Attachment loss means the proportion of a tooth's root support, gum attachment plus bone, that has been destroyed. It is measured with a periodontal probe and confirmed on dental radiographs.

Stage	Also called	Attachment or bone loss	Typical findings
Stage 0	Normal periodontium	None	Clean gum margin, no inflammation, healthy probing depths
Stage 1	Gingivitis, grade 1	None	Red or puffy gum margin that may bleed, plaque and early tartar, attachment intact
Stage 2	Early periodontitis, grade 2	Less than 25%	Deeper pockets than normal, first visible bone loss on X-ray, early furcation exposure
Stage 3	Moderate periodontitis, grade 3	25% to 50%	Gum recession, exposed root surface, partial furcation involvement, slight mobility
Stage 4	Advanced periodontitis, grade 4	More than 50%	Through-and-through furcation, loose teeth, pus, possible oronasal fistula

Two extra indices usually appear alongside the stage. Furcation describes how far a probe can travel into the space between the roots of a multi-rooted tooth: barely detectable, partway through, or all the way through. Mobility describes how much the tooth moves when pressed, from almost imperceptible to visibly wobbly or able to be depressed into the socket. A tooth with through-and-through furcation or marked mobility is being graded at the severe end regardless of how clean the crown looks.

What changes in the mouth at each grade

Grade 1 is gingivitis only. The gum margin is inflamed and bleeds easily when brushed or probed, plaque sits along the gum line, and early calculus may be visible. Underneath, nothing has been lost: probing depths are normal and radiographs show an intact bone crest. Grade 1 is the only stage of canine gum disease that can be fully reversed, because inflamed gum tissue can return to normal but destroyed bone does not grow back on its own. A professional cleaning under anesthesia, followed by consistent home care, is what reverses it.

Grade 2 is early periodontitis. Less than a quarter of the attachment is gone. Pockets are measurably deeper than healthy sulcus depth, X-rays show the first blunting or dip of the bone crest between roots, and breath often starts to turn. Owners usually encounter this grade on a dental chart handed over after a cleaning. It is the point where intervention has the most leverage, because the tooth is still highly salvageable and the goal shifts from reversal to arrest.

Grade 3 is moderate periodontitis. Between a quarter and half of the attachment has been destroyed. Gums recede, root surface becomes visible, pockets are deep enough to pack with food and debris, and on multi-rooted teeth a probe slips partway into the furcation. Teeth may have slight mobility. At this grade a vet is weighing advanced periodontal therapy for that tooth, which may include deep root planing, local treatment of the pocket and committed home care, against extraction. The decision depends on which tooth it is, how much bone remains, and how realistically the pocket can be kept clean afterwards.

Grade 4 is advanced periodontitis. More than half the attachment is gone. Teeth may be visibly loose, the probe may pass straight through the furcation, and pus can be expressed from the gum margin. Grade 4 is also where the complications show up: a draining tract on the face from an abscessed tooth root, an oronasal fistula where bone loss at an upper canine opens a communication into the nasal cavity and causes chronic nasal discharge or sneezing, and in small breeds a weakened lower jaw that is vulnerable to fracture. Teeth at this grade are extracted in most cases, because the support structure that would hold them has already gone.

Progression is not on a timetable. Toy and small breeds, dogs with crowded or rotated teeth, brachycephalic dogs and dogs with no home dental care tend to move through the grades faster, but results vary from dog to dog, and plenty of mouths hold steady at a low grade for years with good care.

Why dental X-rays, and not the gum line, decide the grade

Most of a dog's tooth lies below the gum. The crown you can see is the smaller part of the structure, and periodontal disease destroys the part you cannot see first. That is why awake examination can suggest a problem but cannot grade it.

Accurate staging needs two things done under general anesthesia: circumferential probing of every tooth to measure pocket depth, recession, furcation and mobility, and full-mouth intraoral radiographs to measure bone loss. X-rays reveal horizontal bone loss across a whole arcade, vertical defects along a single root, root resorption, retained root fragments and abscesses at the root tip, none of which are visible from the outside. Anesthesia-free scaling cannot do any of this. It polishes the visible crown while the disease below the gum line goes unmeasured and untreated, and the American Veterinary Dental College does not endorse it.

Periodontal disease is also not just a mouth problem. Research suggests an association between severe periodontal disease in dogs and inflammatory changes elsewhere in the body, and chronic dental pain is a recognised cause of behaviour change, reduced appetite and withdrawal. Dogs rarely stop eating because of dental pain until it is extreme, so a normal appetite is not evidence of a healthy mouth.

What stage 4 before and after photos actually show

People look for dog gum disease pictures by stage, and stage 4 before and after images in particular, for an understandable reason: they want to calibrate what they are seeing in their own dog's mouth. Photos are useful for recognising warning signs, and genuinely misleading for grading.

A photo shows calculus, gum colour, recession, pus and obvious mobility. It cannot show attachment loss, which is the actual definition of the grade. A tooth thickly caked in tartar may turn out to be grade 1 or 2 once cleaned and radiographed. A tooth that looks almost presentable may be grade 4 with a hollowed-out bone bed underneath. Typical before and after sets compare a mouth loaded with calculus and inflamed gums against the same mouth after scaling, polishing and extraction of the teeth that could not be saved. What they illustrate is the result of treatment, not a diagnostic scale.

The better version of that photo search is your own dog's records. Ask your clinic for the dental chart and the radiographs taken at the last procedure. Those two documents tell you the grade of every individual tooth, which teeth are being monitored and which are at risk next time.

Treatment at each grade and what home care can realistically do

Treatment is chosen per tooth, by your veterinarian, after probing and radiographs. Broadly, grade 1 calls for professional cleaning and daily home care. Grade 2 adds subgingival scaling and root planing of affected pockets. Grade 3 means advanced periodontal therapy or extraction depending on the tooth and the remaining bone. Grade 4 usually means extraction, with repair of any fistula and management of pain. Whether antibiotics, local therapies or referral to a board-certified veterinary dentist belong in the plan is a clinical judgement, so talk to your vet about what each affected tooth needs rather than assuming a single approach covers the whole mouth.

Home care is what controls plaque between procedures, and plaque is what drives the disease. Daily toothbrushing with a toothpaste made for dogs remains the most effective home measure. Where brushing is not tolerated, the Veterinary Oral Health Council maintains a list of dental diets, chews, gels and water additives that have met its standards for reducing plaque or calculus, and that list is a sensible filter against marketing claims. Avoid very hard chews such as antlers, bones and hard nylon, which carry a real risk of slab fractures in the carnassial teeth.

Home care slows accumulation. It does not clean below the gum line and does not regrow lost bone, which is why it supports professional care rather than replacing it.

Key Takeaways

• Canine periodontal disease is graded 1 to 4, based on the percentage of a tooth's attachment and bone support that has been lost.
• Grade 1 is gingivitis with no attachment loss and is reversible; grades 2, 3 and 4 involve bone loss, where the aim becomes stopping further damage.
• Grades are assigned per tooth, so one dog can have several different grades in the same mouth.
• Accurate grading requires periodontal probing and full-mouth dental radiographs under general anesthesia.
• Photos cannot determine a stage, because the disease happens below the gum line; your dog's own dental chart and X-rays can.
• Red or bleeding gums, persistent bad breath, facial swelling, a draining sore under an eye, chewing on one side or dropping food all warrant a veterinary exam.

Your veterinarian owns the diagnosis, the grading and the treatment plan for every tooth in your dog's mouth, because those decisions rest on measurements and radiographs that cannot be made at home. Home care works alongside that plan, keeping plaque down between professional visits so the mouth has the best chance of holding its ground.

Related reading: Dog Emergency Signs covers the symptoms that mean a same-day or emergency visit rather than a routine appointment, including facial swelling and sudden refusal to eat.