Guides
Biological Width (Supracrestal Tissue Attachment) Explained
Quick answer
Biological width is the band of gum tissue, about 2 mm deep, that attaches to a tooth just above the bone. Since the 2017 World Workshop on periodontal classification, it has formally been called the supracrestal tissue attachment.2 Crown and veneer margins that invade it cause chronic gum inflammation.
What the tissue consists of
Classic measurements describe two layers above the bone crest:
- Connective tissue attachment: about 1 mm.
- Junctional epithelium: about 1 mm.1
Above these sits the gingival sulcus, a shallow groove typically under 1 mm deep in health. This is why clinicians often work to a guideline of around 3 mm from the bone crest to a restoration margin.
Why it matters for crowns and veneers
When a margin is placed too deep, the body treats it as an irritant. The result is persistent inflammation, bleeding on brushing and, over time, either:
- gum recession, typically in thin gum tissue, which can expose the margin or a metal collar; or
- bone loss with a deepening pocket, typically in thicker tissue.
The safest margins are at the gum line or slightly above it. Where a margin must be hidden, it should extend no more than about 0.5 mm into the sulcus.
Gum contouring and crown lengthening
Removing gum tissue alone (gingivectomy, often with a laser) works only when there is excess soft tissue above a normal bone level. If the planned gum margin would sit too close to the bone, the tissue grows back or stays inflamed. Surgical crown lengthening, which also recontours the bone, is then needed, followed by 8–12 weeks of healing before final restorations. The clinician measures the bone level beforehand by probing under anaesthetic (bone sounding).
Papillae between teeth
When the distance from the contact point between two teeth to the bone crest is 5 mm or less, the papilla fills the space in almost all cases.3 As the distance increases, dark triangles become more likely.
Around implants
Implants develop a similar soft tissue seal, typically slightly taller, at about 3–4 mm. The same principles apply to implant crown margins and abutment design. See our guide to implant positioning rules.
Related guides
Zirconia crowns · Porcelain crowns · Hollywood smile · Implant positioning rules
References
- Gargiulo AW, Wentz FM, Orban B. Dimensions and relations of the dentogingival junction in humans. J Periodontol. 1961;32(3):261–267. PubMed
- Jepsen S, Caton JG, Albandar JM, et al. Periodontal manifestations of systemic diseases and developmental and acquired conditions: consensus report of workgroup 3 of the 2017 World Workshop. J Clin Periodontol. 2018;45(Suppl 20):S219–S229. PubMed
- Tarnow DP, Magner AW, Fletcher P. The effect of the distance from the contact point to the crest of bone on the presence or absence of the interproximal dental papilla. J Periodontol. 1992;63(12):995–996. PubMed