Healthy Gingival Sulcus
A healthy sulcus probes shallow with no bleeding.
- 1–3 mm: Normal sulcus depth (no disease present)
- <10%: Bleeding on probing (sites in health)
- 0 mm: Attachment loss (tissue fully intact)
- ~25 g: Probing force (light, controlled pressure)
What the probe actually measures
Distance from gum margin to pocket base, in mm.
Why healthy tissue resists bleeding
Tight junctional epithelium seals out probe trauma.
Setting the diagnostic baseline
Healthy readings anchor future disease comparisons.
Probe Insertion Technique
Correct angulation keeps the depth reading accurate.
- ~parallel: Probe angulation (to tooth long axis)
- 1 mm steps: Walking stroke (around each tooth)
- 6: Sites per tooth (standard full-mouth chart)
- nearest mm: Reading rounding (standard convention)
Guiding the tip along the tooth
Keep the probe tip against the root surface.
Finding resistance at the base
Gentle pressure stops at junctional epithelium.
Avoiding false high readings
Too much angulation or force overstates depth.
Gingivitis Pocket
Inflammation deepens the pocket without losing attachment.
- 3–4 mm: Typical depth (pseudo-pocket forming)
- >50%: Bleeding on probing (inflamed sites)
- 0 mm: Attachment loss (still reversible)
- Full: Reversibility (with plaque control)
Swelling without bone change
Edema raises the margin, not the attachment level.
Why bleeding appears now
Fragile, engorged capillaries rupture under light probing.
The reversible window
Plaque control alone restores the healthy sulcus.
Moderate Periodontitis Pocket
Depth and attachment loss now rise together.
- 4–5 mm: Typical depth (true periodontal pocket)
- 1–2 mm: Attachment loss (measurable, not reversible)
- ~70%: Bleeding on probing (active sites)
- Mild–moderate: Bone loss (on radiographs)
True pocket, not just swelling
Junctional epithelium migrates apically along the root.
Reading attachment loss
CAL adds recession to the probing depth.
Treatment implications
Scaling and root planing targets this stage.
Severe Periodontitis Pocket
Deep pockets signal major bone and attachment loss.
- >5–6 mm: Typical depth (advanced destruction)
- >4 mm: Attachment loss (severe, often irreversible)
- ~90%: Bleeding on probing (actively progressing sites)
- Elevated: Tooth risk (mobility and loss risk)
Bone support collapses
Alveolar bone recedes well below the cementoenamel junction.
Why the probe sinks deeper
Little tissue resistance remains at the pocket base.
Beyond nonsurgical therapy
Deep sites often require surgical intervention.