You're reclined in the chair, the hygienist is working around your mouth with a thin instrument, and someone starts calling out numbers: "Three, two, three… four, three, five… three, three, four." Nobody explains what they mean, and by the time your mouth is free enough to ask, the moment has passed. If you've ever left an appointment wondering whether those numbers were good news or bad news, this article is for you.
Here is the short version: those numbers are pocket depths — measurements, in millimeters, of the space between your gum and your tooth. They are the single most important screening tool we have for gum disease, a condition that affects nearly half of American adults over 30 and usually causes no pain until it is advanced. As a periodontist, I read these charts every day, and I want you to be able to read yours too. Understanding your numbers turns a mysterious ritual into something you can actually track, question, and improve.
The Short Answer
The numbers are gum pocket depths in millimeters, measured at six points around every tooth. 1–3 mm is healthy. 4 mm is a warning sign. 5 mm and above usually means gum disease with bone loss, because pockets that deep can't be cleaned at home and become protected breeding grounds for bacteria. Bleeding during the measurement means active inflammation. The trend over time matters as much as any single number.
What Is Periodontal Charting?
Periodontal charting is a systematic map of the health of your gums and the bone that supports your teeth. Your teeth don't sit directly in bone like fence posts in concrete — they're suspended by a ligament and surrounded by gum tissue that attaches to the tooth a few millimeters below the visible gumline. The shallow groove between the gum and the tooth is called the sulcus, and in a healthy mouth it's only 1 to 3 millimeters deep.
To measure it, we use a periodontal probe — a slender instrument with millimeter markings, like a tiny ruler. The probe is gently slipped into the sulcus until it meets resistance where the gum attaches to the tooth. The depth at that point is the number you hear called out. It's not sharp and it isn't cutting anything; with healthy gums, probing is barely noticeable. When it's tender or bleeds, that itself is diagnostic information.
At The Loft Dental Studio we record this with digital periodontal charting, which lets us overlay today's measurements on previous visits and see exactly which sites are stable, improving, or quietly getting worse. That trend line is where the real diagnostic power lives.
Why Six Numbers Per Tooth?
Gum disease doesn't attack a tooth evenly. One side of a molar can be perfectly healthy while the surface facing the next tooth is losing bone. That's why we measure six specific sites on every tooth: three along the cheek side (front corner, middle, back corner) and three along the tongue side. A full adult mouth generates up to 168 measurements — which is why the numbers come fast and the hygienist doesn't stop to translate each one.
This is also why a single bad number matters even in an otherwise healthy mouth. A lone 6 mm pocket on the back of one molar can mark a developing abscess, a cracked root, or a spot of localized bone loss — problems that would be invisible if we only glanced at your gums or averaged the readings.
The Number Ranges: What Each One Means
| Pocket Depth | What It Means |
|---|---|
| 1–3 mm, no bleeding | Healthy. The gum is snugly attached and you can keep these areas clean with brushing and flossing. This is the goal. |
| 1–3 mm with bleeding | Gingivitis — inflammation without bone loss. Fully reversible with a professional cleaning and better home care. |
| 4 mm | The warning zone. Either significant inflammation or the earliest stage of periodontitis. At 4 mm, floss and brush bristles are reaching their physical limit. |
| 5–6 mm | Established periodontitis with likely bone loss. These pockets cannot be cleaned at home. Bacteria colonize the root surface below the gumline and the immune response slowly destroys supporting bone. |
| 7 mm and above | Advanced disease. Substantial bone loss, often with looseness, gum recession, or pus. These teeth are at genuine risk and need specialist care promptly. |
Why does the cutoff sit around 4 millimeters? It's mechanical, not arbitrary. A toothbrush bristle and a strand of floss can disrupt bacteria about 3 millimeters below the gumline. Deeper than that, plaque matures undisturbed into a structured biofilm, hardens into calculus (tartar), and triggers a chronic immune response. Your own inflammation, not the bacteria directly, does most of the bone destruction. The deeper the pocket, the more protected the bacteria, and the faster the cycle feeds itself. That is the entire logic of periodontal treatment: eliminate the deep, uncleanable pocket.
The Other Numbers on Your Chart
Pocket depth gets called out loud, but a complete chart records several other findings, and they matter just as much.
Bleeding on probing
If a site bleeds when gently probed, it's actively inflamed — healthy gum tissue doesn't bleed from a few grams of pressure. Bleeding on probing is one of our best indicators of current disease activity, as opposed to old, stable damage. A 5 mm pocket that never bleeds may simply be a scar of past disease being maintained well; a 4 mm pocket that bleeds every visit is an active problem. If your gums also bleed at home, my article on why gums bleed when you brush covers this in depth.
Gum recession
Recession is measured as the distance the gumline has migrated down the root, also in millimeters. It matters because it adds to the total support the tooth has lost. A 3 mm pocket with 3 mm of recession means 6 mm of lost attachment — the same destruction as a 6 mm pocket, just distributed differently. Clinicians combine these into clinical attachment level, the most accurate measure of true disease severity. Significant recession can often be corrected with gum grafting, which restores both coverage and the protective band of firm tissue around the tooth.
Mobility
Tooth looseness is graded 0 to 3. Grade 1 is slight, barely perceptible movement; grade 2 is visible movement side to side; grade 3 means the tooth can move up and down in its socket. Mobility usually reflects substantial bone loss, though a heavy bite or grinding habit can contribute.
Furcation involvement
Molars have two or three roots that branch like a tree. When bone loss reaches the point where the roots divide, the probe can slip into that junction — a "furcation." These areas are notoriously difficult to keep clean and are graded I to III by how far the probe passes through. Furcation involvement is one of the strongest predictors of future tooth loss, and one of the clearest signals that a specialist should be managing the tooth.
What Happens at Each Stage: The Treatment Ladder
The numbers aren't just a report card — they map directly to treatment.
- Healthy numbers (1–3 mm, minimal bleeding): routine professional cleanings and solid home care. Your job is to keep it that way.
- Gingivitis (bleeding, no bone loss): a thorough professional cleaning and improved brushing and flossing typically resolve it completely, often within weeks. This is the last fully reversible stage — take it seriously.
- 4–5 mm pockets: the standard first treatment is scaling and root planing — a deep cleaning under local anesthetic that removes bacteria and calculus from the root surfaces below the gumline. When inflammation resolves, swollen tissue tightens back against the tooth and pockets commonly shrink by 1 to 2 millimeters.
- Pockets that stay 5 mm or deeper after deep cleaning: this is periodontist territory. Options include LANAP laser therapy, which removes diseased tissue and disinfects the pocket without cutting or sutures and can stimulate true reattachment, and bone regeneration procedures for suitable defects. The right choice depends on the pattern of bone loss, which is exactly what the chart and 3D imaging reveal.
- After any treatment: periodontal maintenance visits every 3 to 4 months, with re-charting to verify the numbers are holding. Gum disease is controlled, not cured — maintenance is what keeps the results.
Key Takeaway
Ask for your numbers at every visit, and ask how they compare to last time. A mouth full of stable 2s and 3s is a win worth knowing about. A site that has drifted from 3 to 4 to 5 over three visits is a problem worth catching — and catching it on the chart, years before it hurts, is the entire point of measuring.
Can the Numbers Get Better?
Yes — and this surprises many patients who assume the chart only ever gets worse. When inflammation resolves after scaling and root planing, pocket depths routinely improve. Shallow and moderate pockets respond best. When we re-chart 4 to 8 weeks after treatment, it's common to see 4s become 3s and 5s become 3s or 4s.
Deeper pockets caused by true bone loss are more stubborn, because cleaning alone can't rebuild bone. But this is where modern periodontics has changed the outlook. LANAP laser treatment has histologic evidence of new attachment forming on previously diseased root surfaces, and regenerative procedures using grafting materials and growth factors can rebuild bone in the right defect shapes. Not every site is a candidate for regeneration — anyone who promises to regrow bone everywhere is overselling — but the era when a deep pocket automatically meant cutting the gums down or losing the tooth is over. My philosophy is to save teeth and maintain them, and the chart is the tool that tells us, tooth by tooth and site by site, what saving them will take.
Why the Numbers Matter More Than Pain
Periodontal disease is sometimes called a silent disease, and the label is earned. It doesn't behave like a cavity, which eventually announces itself with sensitivity or a toothache. Gum disease destroys bone gradually and painlessly for years. By the time teeth feel loose or gums visibly recede, the disease is usually advanced and the options are narrower and more expensive.
The probing numbers are how we catch it in the silent years, when treatment is simpler, cheaper, and far more likely to preserve every tooth. This is also why "nothing hurts" is never a reason to skip exams, and why a checkup that never includes probing is incomplete. If your dental visits haven't included a full periodontal charting in over a year, request one — it takes about ten minutes and it is the most information-dense ten minutes in dentistry.
When Your Numbers Mean You Should See a Periodontist
General dentists manage early gum disease well. But certain findings on the chart warrant a specialist's evaluation: multiple pockets of 5 mm or more, pockets that persist after a deep cleaning, any furcation involvement, increasing mobility, aggressive bone loss at a young age, or gum disease alongside diabetes or a family history of tooth loss. If any of these sound familiar, my guide on the signs you need to see a periodontist goes further, and a consultation costs far less than the tooth you might otherwise lose. Comprehensive periodontal treatment is most effective when it starts before the chart reads 7.
