Gum disease — periodontal disease, in clinical language — is one of the most common conditions in adult dentistry, and one of the most preventable. It also tends to be silent in its earliest stages, which is part of why it progresses unnoticed for so many patients. Knowing what gum disease looks like at each stage, what is happening underneath the surface, and which stages can be fully reversed is one of the most empowering pieces of dental knowledge a patient can have.
This guide walks through the four stages most dentists describe — gingivitis, mild periodontitis, moderate periodontitis, and severe periodontitis — explaining what is happening in your mouth at each step, the signs to watch for, and what kind of treatment is typically needed.
What Gum Disease Actually Is
Gum disease is a chronic, bacterial-driven inflammation that affects the gums and the bone supporting the teeth. The same plaque that causes cavities, when allowed to accumulate at the gumline, sets off an immune response. Over time, the inflammation breaks down the small fibers that attach the gum to each tooth, and eventually the bone underneath. The deeper the disease goes, the harder it is to clean and the further it tends to progress — a slow, self-reinforcing cycle.
The American Dental Association overview of gum disease summarizes the science clearly, and our overview of periodontal treatments explains what care looks like at our office.
Stage 1: Gingivitis (Reversible)
Gingivitis is inflammation of the gum tissue without bone loss. The gums become slightly red, slightly puffy, and bleed easily when brushing or flossing. There may be mild bad breath. Pocket depths around the teeth are still in the 1 to 3 millimeter healthy range, and X-rays show normal bone level.
What's Happening
Plaque has accumulated at the gumline, often in spots that home care is not reaching consistently. The gums are responding with inflammation, but the supporting structures — bone and ligament — are still intact. This is the most important stage to recognize, because it is fully reversible.
Reversing Gingivitis
With consistent twice-daily brushing, daily cleaning between teeth, and a professional cleaning, gingivitis often resolves within 7 to 14 days. The redness fades, bleeding stops, and the tissue tightens back around the teeth. Our resource on how to prevent gum disease at home walks through the daily habits that make this routine.
Patients who address gingivitis early avoid the long, much harder path that follows when it progresses.
Stage 2: Mild Periodontitis
When gingivitis is left untreated, the inflammation can progress beyond the gum tissue and begin affecting the small fibers and bone that hold each tooth in place. At this stage, pocket depths typically reach 4 to 5 millimeters, and X-rays show small amounts of bone loss between teeth. The gums may still bleed when brushed and may start to look slightly receded.
What's Happening
Bacteria have moved deeper into the now-larger space between tooth and gum. The pocket itself becomes a habitat — it is harder for a toothbrush to reach the bottom, and the oxygen-poor environment favors more aggressive bacterial species. The body's immune response continues, and small amounts of bone are lost as part of the chronic inflammation.
Treatment at This Stage
Mild periodontitis is typically treated with a non-surgical procedure called scaling and root planing — sometimes called a "deep cleaning." Our resource on scaling and root planing explained walks through what the visit looks like. Most patients also begin a more frequent cleaning interval (every three to four months) to keep the disease from re-progressing.
With proper treatment and good home care, mild periodontitis can usually be stabilized. Some pocket reduction is possible as the gum tissue tightens back around clean root surfaces.
Stage 3: Moderate Periodontitis
Moderate periodontitis brings deeper pockets — typically 5 to 7 millimeters — and more visible bone loss on X-rays. Gums may recede meaningfully, exposing portions of the tooth roots. Some teeth may begin to feel slightly mobile, and small spaces may open between teeth where the gum tissue has shrunk away.
What's Happening
The bacterial colonies have established themselves deeper, and the bone loss has progressed beyond the early stage. Periodic flare-ups (sometimes painful, sometimes silent) may occur as the disease continues. Without treatment, this stage often progresses steadily.
Treatment at This Stage
Treatment becomes more involved. In addition to scaling and root planing, your dentist may recommend localized antimicrobial therapy, a referral to a periodontist for evaluation of surgical options, or other targeted interventions. Frequent maintenance — every three months — becomes essential to prevent re-progression.
Bone that has already been lost generally does not regrow on its own. The goal at this stage shifts from reversal to control: stopping further loss, supporting the teeth that remain, and keeping the disease in remission.
Stage 4: Severe (Advanced) Periodontitis
Severe periodontitis features pockets of 7 millimeters or deeper, significant bone loss, noticeable mobility of one or more teeth, persistent bad breath, gum abscesses, and sometimes pus around the gumline. Some teeth may be at risk of being lost.
What's Happening
The supporting bone has been substantially destroyed in some areas. The teeth most affected are often back molars that are harder to clean, but front teeth can be involved as well. At this point the disease is a major factor in the patient's overall oral health and sometimes in their general health as well.
Treatment at This Stage
Treatment becomes a coordinated plan, often involving surgical procedures performed by a periodontist (gum specialist), some teeth that may be too compromised to save, and ongoing maintenance every three months indefinitely. Our resource on when a tooth needs to be extracted explains how that decision is made when a tooth's prognosis is poor.
The good news, even at this stage, is that the disease is treatable. Many patients with severe periodontitis can be stabilized, retain most of their teeth, and continue functioning well — just with a higher level of professional attention than someone whose disease was caught earlier.
How the Stages Are Diagnosed at a Visit
Your hygienist measures pocket depth around each tooth at periodic exams using a thin, ruler-like probe. The numbers are recorded and compared visit-to-visit to spot trends. X-rays show bone level around each root and confirm what the probe suggests. Together, these data points define the stage and shape the treatment plan. For more on what imaging reveals, see our resource on what dental X-rays can detect.
"Periodontal numbers tell a story over time. A 4 mm pocket today is a different conversation than a 4 mm pocket that was 2 mm two years ago. The trend matters as much as the number."
The Big Picture: Stage Catches Disease Earlier
The single most powerful idea about gum disease is that the earlier you catch it, the easier the path back. Gingivitis can be reversed in a week or two with consistent home care. Mild periodontitis usually responds well to scaling and root planing. Moderate and severe stages require more, and bone that is lost generally stays lost. The math always favors catching it early.
To be evaluated and find out exactly where you stand, schedule a periodontal evaluation or learn more on our overview of gum disease care. For prevention, our companion piece on preventing gum disease at home walks through the daily habits that protect your gums for life. Patients in Folsom, CA without dental insurance may also find our membership plans helpful for ongoing maintenance.
Frequently Asked Questions
Can gum disease really be reversed?
The earliest stage — gingivitis — is fully reversible with consistent home care and professional cleanings. Once the disease progresses to periodontitis and bone loss, it can be controlled and stabilized but not reversed in the strictest sense. The bone that has been lost does not generally regrow on its own.
How do dentists measure how advanced gum disease is?
A small ruler-like probe is gently inserted between the tooth and gum to measure pocket depth in millimeters. Healthy pockets are 1 to 3 mm; 4 to 5 mm suggests early periodontitis; 6 mm and above is moderate to severe. X-rays add information about bone level around each tooth root.
Is bleeding when I floss a sign of gum disease?
Often, yes — bleeding gums are usually a sign of inflammation, even mild. The good news is that early-stage bleeding from inflammation typically resolves within a week or two of consistent daily flossing and proper brushing. Bleeding that persists past two weeks of good home care should be evaluated.
Can gum disease affect my overall health?
Research has shown associations between periodontal disease and conditions including diabetes, heart disease, and adverse pregnancy outcomes. While the relationships are complex and not always causal, treating gum disease appears to support better overall health outcomes for many patients.
How often should I be checked if I have a history of gum disease?
Patients with a history of periodontal disease often benefit from periodontal maintenance visits every three to four months rather than the standard six. The shorter interval helps keep the bacterial population in check and gives the team a chance to address early changes before they progress.