Periodontal Probes Compared: PCP 12, UNC 15, WHO Probe, Nabers
The periodontal probe is the most important diagnostic instrument in periodontics. It is used to measure probing depths, provoke bleeding and detect furcations. Probes differ mainly in their scale and the shape of the tip. If you do not know the markings, it is easy to misread measurements. This guide compares the common periodontal probes PCP 12, UNC 15, WHO probe, Williams and Nabers, explains the recommended probing force and gives a brief overview of PSI and PBI.
Key points at a glance
- The PCP 12 has coloured markings at 3, 6, 9 and 12 mm.
- The UNC 15 is marked in 1 mm steps up to 15 mm, with dark bands at 5, 10 and 15 mm.
- The WHO probe has a ball of 0.5 mm diameter and a coloured band between 3.5 and 5.5 mm. It is used for the PSI.
- The Williams probe is marked at 1, 2, 3, 5, 7, 8, 9 and 10 mm; 4 and 6 mm are missing.
- The Nabers probe is curved and is used to examine furcations.
- Probing is done with a light force of about 0.2 to 0.25 N (roughly 20 to 25 g).
What is a periodontal probe used for?
The periodontal probe measures the distance from the gingival margin to the base of the pocket, the so-called probing depth. Measurements are taken at several sites per tooth, usually six: mesial, central and distal, each on the buccal and oral side. The probe also shows whether there is bleeding on probing and detects calculus, overhanging restoration margins and furcations.
Periodontal probes are blunt and have a scale. This distinguishes them from pointed explorers, which are used to detect carious lesions and restoration margins. Many manufacturers combine both in double-ended instruments, for example as a combination instrument with UNC 15 probe.
The main probe types
PCP 12
The PCP 12 has coloured marking bands at 3, 6, 9 and 12 mm. The wide bands are easy to read in the sulcus; values in between are estimated. The probe is widely used in Europe. In our shop you will find the PCP 12 periodontal probe without ball.
UNC 15
The UNC 15 (University of North Carolina) is marked at every millimetre from 1 to 15 mm. Darker bands at 5, 10 and 15 mm make counting easier. The fine graduation is suitable for precise charting and for deep pockets. One example is the UNC 15 periodontal probe with 1–15 graduation.
WHO probe
The WHO probe was developed for epidemiological surveys (CPITN) and is used today for the Periodontal Screening Index (PSI). Its characteristic feature is a ball of 0.5 mm diameter at the tip. It allows gentle probing and the detection of calculus and restoration margins. A coloured, usually black band marks the area between 3.5 and 5.5 mm. Additional markings at 8.5 and 11.5 mm are common. The PCP-11.5-B probe, for example, is marked with this 3.5 – 5.5 – 8.5 – 11.5 mm graduation.
Williams probe
The Williams probe is a classic probe with markings at 1, 2, 3, 5, 7, 8, 9 and 10 mm. The markings at 4 and 6 mm are deliberately omitted. This makes it easier to recognise the position on the scale, but values at 4 and 6 mm have to be read between the markings.
Nabers probe
The Nabers probe is curved and has a blunt end. It is used to detect whether and how far a furcation, the area between the roots of multi-rooted teeth, is open horizontally. Many versions are colour-coded with markings at 3, 6, 9 and 12 mm. In our shop this includes the double-ended PQ2N Nabers instrument.
Comparison table: periodontal probes
| Probe | Markings | Tip | Typical use |
|---|---|---|---|
| PCP 12 | 3 – 6 – 9 – 12 mm (colour bands) | Rounded | Probing depths, quick reading |
| UNC 15 | 1 to 15 mm, every millimetre; bands at 5, 10, 15 mm | Rounded | Detailed periodontal charting, deep pockets |
| WHO probe | Band 3.5 – 5.5 mm, often further marks at 8.5 and 11.5 mm | Ball 0.5 mm | PSI / CPITN, screening |
| Williams | 1 – 2 – 3 – 5 – 7 – 8 – 9 – 10 mm | Rounded | Probing depths |
| Nabers | Often 3 – 6 – 9 – 12 mm or unmarked | Curved, blunt | Furcation assessment |
The information describes the common standard versions. Some manufacturers offer different markings. Always check the scale in the product description.
Probing correctly: force and technique
Probing force directly affects the measurement. With more pressure the probe penetrates deeper and the value is higher; with too little pressure the pocket is underestimated. A light force of about 0.2 to 0.25 N is recommended, which corresponds to roughly 20 to 25 grams. For implants, plastic probes and a force of no more than 0.25 N are often recommended.
- Guide the probe parallel to the tooth axis and in small steps around the tooth (“walking”).
- Measure at six sites per tooth and record the deepest value at each site.
- Use the same probe type throughout a practice whenever possible. Different diameters and scales make it harder to compare findings.
Calculus, severe inflammation, restoration margins and limited mouth opening can also affect the measurement.
Basics: PSI and PBI
Periodontal Screening Index (PSI)
For the PSI, the dentition is divided into sextants. Each tooth is probed with the WHO probe, and the highest code is recorded for each sextant:
- Code 0: Band fully visible, no bleeding, no calculus, no defective restoration margins.
- Code 1: Band fully visible, bleeding on probing.
- Code 2: Band fully visible, calculus or defective restoration margins.
- Code 3: Band partly visible, probing depth 3.5 to 5.5 mm.
- Code 4: Band no longer visible, probing depth over 5.5 mm.
An additional asterisk marks abnormalities such as furcation involvement, increased tooth mobility or recession.
Papillary Bleeding Index (PBI)
For the PBI, the interdental area is probed with a blunt periodontal probe and light pressure. Bleeding at the papilla is scored from grade 0 (no bleeding) to 4 (heavy bleeding, blood flows over the tooth or gingiva). The index is mainly used to document the degree of inflammation and to monitor patient compliance.
You will find further probes in the probes and dilators category and the complete range in the periodontics category. Which curettes are used after charting is explained in our guides Gracey curettes and Scaler or curette?.
Frequently asked questions
Which periodontal probe is the best?
That depends on the purpose. The WHO probe is used for the PSI. For detailed periodontal charting, many practices prefer the UNC 15 with millimetre graduation, others the PCP 12 with easy-to-read colour bands.
What does PCP 12 mean?
PCP 12 refers to a periodontal probe with markings at 3, 6, 9 and 12 mm. The 3 mm intervals are shown by coloured bands.
Why does the WHO probe have a ball?
The ball with a diameter of 0.5 mm makes probing gentler and makes it easier to detect calculus and restoration margins.
What force should be used for probing?
A light force of about 0.2 to 0.25 N, roughly 20 to 25 grams. Too much pressure leads to higher readings.
What is a Nabers probe used for?
To examine furcations on multi-rooted teeth. The curved shape reaches the area between the roots that a straight probe cannot assess.