May 13, 2026

Veterinary Dental Charting: The Triadan System

Q: What is the Triadan system?

The modified Triadan system assigns each tooth a three-digit number. The first digit identifies the quadrant (1–4 permanent, 5–8 deciduous); the next two identify the tooth, counted from the midline.

Q: How do feline and canine Triadan numbers differ?

Cats are missing the 105/205/305/405 (first premolars) and the 305/405 area is condensed. Numbering still follows the same rule of fours from the midline, you just skip the absent positions.

Q: Do I have to chart every tooth on every dental?

Yes for any COHAT — a complete dental chart with probing depths, mobility, furcation, and findings is the standard of care and your legal record of what you did.

Veterinary dental chart with modified Triadan tooth numbering beside dental scaler tools in a clinic — A complete Triadan dental chart is your record of the COHAT — and your defense in a board review.

The modified Triadan system is the universal language of veterinary dentistry. Once you know the rule of fours, you can name every tooth in a dog, cat, or rabbit without a chart at your elbow.

The Rule of Fours

First digit = quadrant. 1 = upper right, 2 = upper left, 3 = lower left, 4 = lower right (permanent). 5–8 mirror that for deciduous.
Last two digits = position from midline. 01 is always the central incisor, 04 the canine, 08 the first molar in dogs.
Mnemonic: canines are always *04, first molars are always *09 (upper) or *09 (lower in dog).

Cat Exception

Cats lack 105/205 and 305/405 (first premolars). Skip the number — don't renumber the arcade. A "missing" 105 charted as PE (previously extracted) tells the next vet something a renumber would hide.

Canine Quadrant Reference

Upper right (1xx)    |    Upper left (2xx)
101 102 103 104 105 106 107 108 109 110
                     midline
401 402 403 404 405 406 407 408 409 410 411
Lower right (4xx)    |    Lower left (3xx)

Lower arcade carries an extra molar (411 / 311) in dogs — easy to miss when charting on the fly.

What a Complete Dental Chart Includes

Per-tooth probing depths (≥4 mm in dogs, ≥1 mm in cats = abnormal)
Mobility grade (M0–M3) and furcation exposure (F1–F3)
Gingival recession and gingival index
TR (tooth resorption) stage in cats, with type when radiographs allow
Extractions performed, with technique and any complications
Full-mouth dental radiograph confirmation

Three Common Charting Mistakes

"Right side" vs "patient's right" — always chart from the patient's perspective.
Charting findings only on diseased teeth. WNL teeth need to be marked WNL, or you can't prove you looked.
Writing "extracted 307" without the technique, suture, and recovery note. The Plan section is where boards live.

Let the Chart Fill Itself

Chartling's species-aware AI recognizes Triadan callouts ("probing 6 on the distal of 208 with grade 2 mobility") and drops them into the dental chart in real time — no clicking through arcades.

Frequently Asked Questions

What is the Triadan system?

A three-digit numbering scheme: quadrant first, then tooth position from the midline. Permanent quadrants are 1–4, deciduous are 5–8.

How do feline and canine Triadan numbers differ?

Cats are missing first premolars (105/205) and have a condensed lower arcade. You skip the absent positions — never renumber.

Do I have to chart every tooth on every dental?

For a COHAT, yes — probing depths, mobility, furcation, and findings on every tooth are the standard of care.

Dental Charts That Write Themselves

Chartling listens to your probing callouts and drops them into the right Triadan slot.

Try Chartling — No credit card required

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