How soft plaque becomes stone
Plaque is a soft bacterial film that forms on teeth within hours. If it is not removed, minerals in your saliva — mainly calcium and phosphate — precipitate into it. Within roughly 24 to 72 hours the film begins hardening, and over one to two weeks it becomes fully mineralised calculus, commonly called tartar.
The clinically important consequence is mechanical, not chemical: calculus has a rough, porous surface that plaque adheres to far more readily than smooth enamel does. So calculus is not just old plaque sitting there — it is a permanent plaque magnet bonded to your tooth. That is the mechanism by which it drives gingivitis and then periodontitis.
Supragingival vs. subgingival — two different problems
| Above the gumline | Below the gumline | |
|---|---|---|
| Colour | Whitish to yellow-brown | Dark brown to black (blood pigments) |
| Common site | Behind lower front teeth, outer upper molars | Inside periodontal pockets |
| Visible to you? | Usually yes | No — needs probing or radiographs |
| Main damage | Gum inflammation, staining, odour | Bone loss |
| Removal | Routine scaling | Deep cleaning, often with anaesthetic |
Why it always appears in the same places
Calculus concentrates where saliva ducts empty, because that is where the mineral supply is richest:
- The inner surface of the lower front teeth — directly opposite the submandibular and sublingual ducts. This is the number-one site in almost everyone, and it is also the surface most people brush least. See tooth anatomy for orientation on tooth surfaces.
- The outer surface of the upper molars — next to the parotid duct openings.
- Crowded or overlapping teeth, where a brush physically cannot pass.
- Around orthodontic brackets and under poorly fitting crown margins.
What actually removes it — and what does not
Only mechanical professional removal works. Specifically:
- Ultrasonic scaling — high-frequency vibration fractures the deposit off the tooth surface. This is the standard method.
- Hand instrumentation for fine finishing and root surfaces.
Things that do not remove calculus, despite marketing claims: whitening toothpaste, charcoal powder, mouthwash, oil pulling, baking soda, "tartar control" formulations (these slow new formation; they do not remove existing deposits), and at-home ultrasonic devices sold online — which mostly polish the surface while leaving the subgingival portion untouched.
Frequency and what to expect
Most people need professional scaling every six to twelve months, but the correct interval is individual — it depends on how fast you mineralise plaque, which varies several-fold between people. Heavy formers, orthodontic patients, smokers, and anyone with treated gum disease generally need three-to-four-month intervals.
Expect mild sensitivity and slightly more visible gaps for a week or two afterwards. Both are normal: the deposit was insulating the tooth and propping up swollen gum tissue. Fees for non-covered scaling are published on our English price list.