Periodontal Probing: Probe Types, Markings and Technique
Key takeaways
- A periodontal probe measures pocket depth in millimeters. The most common types are the UNC-15, Williams, Marquis, WHO/CPI and Nabers probes.
- Probe six sites per tooth with a light force (roughly 10–25 g), keeping the probe as parallel to the long axis of the tooth as possible.
- Use a walking stroke and record the deepest reading at each site.
- Inconsistent force and angulation are the biggest sources of error in periodontal probing.
What is a periodontal probe?
A periodontal probe is a thin, blunt-tipped instrument with millimeter markings, used to measure the depth of the gingival sulcus or periodontal pocket, the position of the gingival margin, bleeding on probing, and furcation involvement. Probes are made of stainless steel, titanium or plastic (plastic probes are often preferred around implants).
Types of periodontal probe and their markings
| Probe | Markings | Best for |
|---|---|---|
| UNC-15 | Every millimeter from 1 to 15, with dark bands at 5, 10 and 15 mm | Full-mouth charting where you want exact readings, especially deeper pockets |
| Williams | 1, 2, 3, 5, 7, 8, 9 and 10 mm (no marks at 4 and 6 mm) | General probing; the gaps make the 3–5 and 5–7 mm zones easy to see |
| Marquis | Color-coded bands, commonly at 3, 6, 9 and 12 mm | Quick visual readings in 3 mm increments |
| WHO / CPI | 0.5 mm ball tip with a colored band from 3.5 to 5.5 mm (some versions add 8.5 and 11.5 mm marks) | Screening (CPI, PSR or BPE); the ball tip reduces the risk of over-probing |
| Nabers | Curved working end, often with 3 mm color-coded bands | Detecting and classifying furcation involvement on multi-rooted teeth |
Marking patterns vary slightly between manufacturers, so check the probe your practice uses – and use the same type for every chart so results stay comparable.
UNC-15 vs. Williams probe
Both are tapered probes used for everyday charting. The UNC-15 has a mark at every millimeter, which makes exact readings easier and covers pockets up to 15 mm. The Williams probe stops at 10 mm and skips the 4 and 6 mm marks, so clinicians estimate those values between bands. Many hygienists prefer the UNC-15 for comprehensive periodontal charting for that reason.
How to probe: step-by-step technique
- Use a light, consistent force. Guidance usually falls between about 10 and 25 grams (often cited as 0.25 N) – enough to blanch a fingernail without discomfort. Heavier force pushes the probe through inflamed tissue and overstates depth.
- Insert gently to the base of the sulcus until you feel resistance.
- Keep the probe parallel to the long axis of the tooth. Tilting it away from the tooth gives falsely shallow readings.
- Walk the probe. Move it in small up-and-down steps of about 1 mm around the tooth without removing it from the sulcus.
- Angle slightly into the col interproximally. At the mesial and distal, tilt the probe just under the contact point so you measure the interdental area, keeping the shank as close to vertical as possible.
- Record the deepest reading at each of six sites: distofacial, facial, mesiofacial, distolingual, lingual and mesiolingual.
- Note bleeding within about 10–30 seconds of probing, along with suppuration.
- Record the gingival margin relative to the CEJ so you can calculate clinical attachment level.
Common probing errors
- Too much force – overstates pocket depth, especially in inflamed tissue.
- Poor angulation – understates depth, particularly interproximally.
- Subgingival calculus – can stop the probe early and understate depth.
- Skipping sites – leaves gaps that make the chart unreliable and hide progression.
- Remembering numbers and entering them later – leads to transcription errors when the hygienist charts alone.
Probing and charting without an assistant
The traditional approach to full-mouth probing takes two people: one probes and calls out numbers, the other types them into the chart. Hygienists working alone switch between the probe and the keyboard, or hold numbers in memory – which is slow and error-prone. Voice charting removes that trade-off: the hygienist keeps both hands on the instruments and speaks each reading as they probe. Read more about perio charting without an assistant.
Keep both hands on the probe
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.
What to do with the numbers
Probing depths only become meaningful alongside the rest of the chart. See what gum pocket depth numbers mean, how to calculate CAL and record furcation and mobility, and how those numbers feed into periodontal staging and grading. For the full process, start with our perio charting guide.
Frequently asked questions
What are the markings on a UNC-15 probe?
A UNC-15 probe is marked at every millimeter from 1 to 15 mm, with dark bands at 5, 10 and 15 mm.
What are the markings on a Williams probe?
A Williams probe is marked at 1, 2, 3, 5, 7, 8, 9 and 10 mm. There are no marks at 4 and 6 mm.
How much force should you use when probing?
Use a light, consistent force – guidance usually falls between about 10 and 25 grams, often cited as 0.25 N. Too much force overstates pocket depth, especially in inflamed tissue.
How many sites do you probe per tooth?
Six: distofacial, facial, mesiofacial, distolingual, lingual and mesiolingual. Record the deepest reading at each site.
Which probe is used for furcations?
A curved Nabers probe is used to detect and classify furcation involvement on multi-rooted teeth.
Shelly Mendoza is a results-driven executive with 25+ years in the dental industry. Starting as a dental assistant, she brings deep clinical and operational insight to every leadership role. She has led multi-site DSO operations, implemented scalable systems, and earned multiple President’s Club honors. Shelly is passionate about workflow solutions that boost team efficiency and elevate the patient experience.
