Perio Chart Measurements Explained: CAL, Gingival Margin, Furcation and Mobility
Key takeaways
- A complete perio chart records much more than pocket depth: gingival margin, clinical attachment level (CAL), bleeding and suppuration, furcation involvement, mobility, and often plaque and the mucogingival junction.
- CAL is the true measure of attachment loss: probing depth plus recession, or probing depth minus gingival overgrowth.
- Furcation is usually graded with the Glickman classification (Grade I–IV); mobility with the Miller index (Class I–III).
- These measurements feed directly into periodontal staging – Class II or III furcations and mobility of degree 2 or more are complexity factors.
Perio chart measurements at a glance
| Measurement | What it shows | How it’s recorded |
|---|---|---|
| Probing depth (PD) | Depth of the sulcus or pocket | mm, six sites per tooth |
| Gingival margin (GM) | Position of the gum edge relative to the CEJ | mm, positive or negative depending on charting convention |
| Clinical attachment level (CAL) | Total loss of periodontal support | mm, calculated from PD and GM |
| Bleeding on probing (BOP) | Active inflammation | Yes/no per site; summarized as a percentage |
| Suppuration | Pus from the pocket; active infection | Yes/no per site |
| Furcation involvement | Bone loss between the roots of multi-rooted teeth | Grade I–IV (Glickman) |
| Mobility | How much the tooth moves | Class I–III (Miller) |
| Mucogingival junction / attached gingiva | Width of keratinized, attached tissue | mm |
| Plaque | Biofilm present at the site | Yes/no per site or a plaque score |
Gingival margin
The gingival margin is the edge of the gum tissue around the tooth. On a perio chart, it is recorded as its distance from the cementoenamel junction (CEJ) – the line where the enamel of the crown meets the cementum of the root. If the gum has receded and the margin sits below (apical to) the CEJ, that distance is recession. If the gum is swollen or overgrown and sits above (coronal to) the CEJ, the margin covers part of the crown. Charting software and paper forms use different sign conventions for these two cases, so check yours before you calculate anything.
Clinical attachment level (CAL)
CAL is the distance from the CEJ to the base of the pocket. Unlike probing depth, it doesn’t move when the gum line moves, which makes it the most reliable measure of attachment loss – and the main input for periodontal staging.
How to calculate clinical attachment level
| Gingival margin position | Formula | Example |
|---|---|---|
| Apical to the CEJ (recession) | CAL = PD + recession | PD 4 mm + 2 mm recession = 6 mm CAL |
| At the CEJ | CAL = PD | PD 4 mm = 4 mm CAL |
| Coronal to the CEJ (overgrowth) | CAL = PD − distance from margin to CEJ | PD 5 mm, margin 2 mm above CEJ = 3 mm CAL |
The third row is why a 5 mm reading isn’t always periodontitis: swollen tissue can create a pseudo-pocket with little or no attachment loss.
Bleeding on probing and suppuration
Bleeding on probing is recorded per site, usually as a red mark on the chart, and summarized as the percentage of bleeding sites. It is the key sign of active inflammation: under the 2017 AAP/EFP classification, gingivitis on an intact periodontium is defined as bleeding at 10% or more of sites, with 10–30% considered localized and more than 30% generalized. Suppuration (pus) is recorded separately and points to an active infection in the pocket.
Furcation involvement and classification
A furcation is the area where the roots of a multi-rooted tooth divide. When periodontitis destroys bone in that area, the furcation becomes “involved.” It is detected with a curved Nabers probe and most often graded with the Glickman classification:
| Glickman grade | Description |
|---|---|
| Grade I | Incipient. The probe can feel the furcation entrance but cannot enter it horizontally by more than about 1 mm; bone loss is rarely visible on radiographs. |
| Grade II | The probe enters the furcation horizontally, but bone remains and the probe does not pass through to the other side (a cul-de-sac). |
| Grade III | Through-and-through: the probe passes completely between the roots, but the entrance is still covered by gum tissue. |
| Grade IV | Through-and-through, with recession leaving the furcation entrance clinically visible. |
Some practices use the Hamp classification instead, which is based on horizontal probing depth: Class I is less than 3 mm, Class II is 3 mm or more without passing through, and Class III is through-and-through. Under the 2017 staging system, Class II or III furcation involvement is a complexity factor for Stage III periodontitis.
Tooth mobility classification
Mobility is checked by holding the tooth between two rigid instrument handles (not fingertips) and applying gentle pressure. The Miller index is the most widely used scale:
| Class | Description |
|---|---|
| Class I | Slightly more than normal; up to about 1 mm of horizontal movement |
| Class II | More than 1 mm of horizontal movement, with no vertical movement |
| Class III | More than 1 mm of horizontal movement and vertical depressibility in the socket |
Secondary occlusal trauma with mobility of degree 2 or more is one of the factors that can place a case in Stage IV.
Mucogingival junction and attached gingiva
The mucogingival junction (MGJ) is the line where firm, keratinized gingiva meets the looser alveolar mucosa. The width of attached gingiva is the distance from the gingival margin to the MGJ, minus the probing depth. Too little attached gingiva – especially with recession – is recorded as a mucogingival defect and may need monitoring or treatment.
Recording it all, accurately
A full chart for a 28-tooth patient can mean 168 probing depths plus margins, bleeding points, furcations and mobility – every one of which affects the diagnosis. Skipped or estimated entries make staging less reliable and progression harder to prove. For the full workflow, see our perio charting guide and periodontal probing technique, or practice with our free online perio chart.
Chart every measurement by voice
With Denti.AI Voice Perio, hygienists speak pocket depths, bleeding, recession, furcation and mobility as they probe, and the perio chart fills in on screen. A full-mouth chart takes about 5 minutes, saves straight to your practice management system, and comes with a patient-friendly oral health report. Voice Perio is part of OneStop Clinical, together with Denti.AI Scribe for AI clinical notes.
Frequently asked questions
How do you calculate clinical attachment level?
If the gum has receded below the CEJ, CAL = probing depth + recession. If the gum margin is at the CEJ, CAL = probing depth. If the gum is swollen above the CEJ, CAL = probing depth minus the distance from the margin to the CEJ.
What is the Glickman furcation classification?
Grade I: incipient, the probe cannot enter the furcation horizontally by more than about 1 mm. Grade II: the probe enters but does not pass through. Grade III: through-and-through, but covered by gum tissue. Grade IV: through-and-through and clinically visible because of recession.
What are the classes of tooth mobility?
Under the Miller index, Class I is up to about 1 mm of horizontal movement, Class II is more than 1 mm of horizontal movement without vertical movement, and Class III is more than 1 mm of horizontal movement plus vertical depressibility.
What is the gingival margin on a perio chart?
The gingival margin is the position of the edge of the gum relative to the cementoenamel junction (CEJ). It is used with probing depth to calculate clinical attachment level.
