Periodontal Probe Markings & Types Guide – UNC-15, Williams, Nabers & WHO Explained
Periodontal probes are the measuring instruments of periodontics — calibrated tips used to record pocket depths, attachment levels, bleeding on probing, and furcation involvement. But not all probes read the same way: marking patterns differ between designs, and choosing the wrong probe (or misreading its bands) leads to inconsistent charting. This guide explains the major periodontal probe types, their marking systems, and when to use each — with a comparison chart for quick reference. Note that German manufacturers often catalog these patterns under different names — the UNC-15 is Helmut Zepf's North Carolina CNC, and the Marquis marking system appears as CPG 12; the chart links each pattern to its ZEPF equivalent.
Periodontal Probe Marking Systems: Comparison Chart
| Probe Type | Markings (mm) | Tip Design | Primary Use |
|---|---|---|---|
| UNC-15 (ZEPF: North Carolina CNC) | Every millimeter to 15; color bands at 4–5, 9–10, and 14–15 | Straight, thin, round | Precise full-mouth charting; research standard |
| Williams | 1, 2, 3, 5, 7, 8, 9, 10 (4 and 6 omitted to reduce misreading) | Straight, round | General pocket depth measurement; the classic teaching probe |
| Michigan-O (ZEPF equivalent: Contrast Insert #1, 3/6/8/11) | 3, 6, 8 (ZEPF pattern adds 11) | Straight, fine, round | Quick screening with a slim tip |
| Marquis (ZEPF: CPG 12) | Alternating color bands every 3 mm (3, 6, 9, 12) | Straight, round | Rapid visual screening by band |
| WHO / CPITN (ZEPF: CP 11.5) | 0.5 mm ball tip; black band from 3.5–5.5 mm (some versions add 8.5 and 11.5) | Ball-ended | BPE / PSR screening; gentle on tissue |
| PSI Screening (ZEPF: CPN 22) | 2, 4, 6, 8, 10, 12 | Straight, round | Periodontal Screening Index recording at 2 mm intervals |
| Nabers | Color-coded, typically at 3, 6, 9, 12 | Curved | Furcation involvement classification (Grades I–III) |
How to Read a Periodontal Probe
Insert the probe parallel to the long axis of the tooth with light pressure (approximately 10–25 g) until resistance is met at the base of the sulcus or pocket. Read the measurement at the gingival margin, rounding up to the nearest marking. Record six sites per tooth: mesio-buccal, buccal, disto-buccal, and the corresponding lingual sites. Pocket depths of 1–3 mm are generally healthy; 4 mm and beyond warrants closer periodontal evaluation. Consistency matters more than any single reading — which is why practices standardize on one probe design across all operatories.
Choosing the Right Probe
For full periodontal charting: the UNC-15 is the modern standard — every-millimeter markings leave no interpolation. Zepf's North Carolina CNC line covers it in fixed-handle, interchangeable-insert, titanium, and TOUCHGRIP versions. For fast screening: Marquis-pattern (CPG 12) or WHO ball-end probes let you flag pockets by color band at a glance. For furcations: the curved Nabers probe is purpose-built for classifying furcation involvement on multi-rooted teeth and has no substitute. For gingival graft and recession measurement: a dedicated periodontometer such as the Kahn Probe is designed for soft tissue measurement in mucogingival procedures.
Helmut Zepf Periodontal Probes
Our ZEPF Periodontal Probe Collection covers the marking systems above in German surgical stainless steel, with laser-etched calibrations that survive repeated autoclave cycles without fading — a common failure point on printed-band probes. Several handle systems accept interchangeable probe inserts, letting you replace a worn tip without replacing the instrument. Browse the full periodontal probe collection or the complete ZEPF Hygiene Instrument Collection for the surrounding armamentarium, including Gracey curettes and sickle scalers. Exploring the maxillary antrum rather than the sulcus? See the Antrum & Surgical Probe Collection.
Care and Sterilization
Probes are precision-calibrated instruments: avoid ultrasonic baskets that allow tip-to-tip contact, inspect calibration bands during reprocessing, and retire probes with bent or worn tips — a 0.5 mm bend at the tip is a 0.5 mm charting error on every patient. Full reprocessing parameters are in our Instrument Reprocessing & Sterilization Guide. For terminology, see the Hygiene Instrument Glossary.
Frequently Asked Questions
What do the markings on a perio probe mean?
The markings are millimeter calibrations used to measure pocket depth from the gingival margin to the base of the sulcus. Different probe designs mark different intervals — the UNC-15 marks every millimeter, the Williams skips 4 and 6, and the Marquis uses 3 mm color bands.
What is the difference between a UNC-15 and a Williams probe?
The UNC-15 is marked at every millimeter to 15 mm with color bands at 5, 10, and 15 for orientation. The Williams probe marks 1, 2, 3, 5, 7, 8, 9, and 10, deliberately omitting 4 and 6 so adjacent lines are easier to distinguish.
Is the North Carolina CNC probe the same as a UNC-15?
Yes. UNC stands for University of North Carolina — German manufacturers including Helmut Zepf catalog the same 1–15 mm every-millimeter pattern as "North Carolina" or "CNC."
What is a Nabers probe used for?
The Nabers probe is a curved, color-coded probe designed to enter and measure furcation areas between the roots of multi-rooted teeth, used to classify furcation involvement from Grade I to Grade III.
How much pressure should be used when probing?
Approximately 10–25 grams of force — commonly described as the pressure that blanches a fingernail without causing discomfort. Excessive force penetrates the junctional epithelium and overstates pocket depth.
