Those small dark gaps that can appear between teeth near the gumline — dentists call them “black triangles” — are one of the most common smile concerns we hear about, and one of the most satisfying to fix. At Kentfield Dental, Dr. Soroush Ghaffarpour (“Dr. G”) closes black triangles using the Bioclear Matrix System, a modern, minimally invasive technique that rebuilds smooth, natural-looking contact between teeth without drilling away healthy tooth structure. For many Marin patients it’s a conservative, tooth-preserving alternative to veneers or crowns — often completed comfortably, frequently without any anesthetic, in our Kentfield office.
What is a black triangle, and what closes it?
A black triangle — known clinically as an open gingival embrasure — is the small triangular gap that can open up between two teeth just below the contact point, near the gumline. They tend to show up after gum recession or bone loss, with naturally triangular-shaped teeth or a thin gum biotype, after orthodontic treatment shifts teeth, or simply with age. Beyond the cosmetic concern, they can trap food and be hard to keep clean.
Black triangle closure rebuilds the missing contact between the teeth so the dark space disappears. We use the Bioclear Matrix System, which wraps the teeth in anatomically shaped clear matrices and injection-molds warmed, tooth-colored composite around them to create smooth, gap-free, naturally contoured edges that support the gum and are easy to floss. Because it adds to the tooth rather than cutting it down, it’s a conservative approach — in many cases no drilling and no anesthetic are needed.
How we close black triangles with Bioclear
Bioclear is a different approach from traditional bonding, and the technique is what makes the result last and look natural. Dr. G starts by thoroughly cleaning the tooth surfaces — a gentle aluminum-trihydroxide polish that removes the invisible biofilm so the composite bonds reliably. Next, ultra-thin, curved clear matrices are placed and tucked slightly below the gumline to shape the new contour. Warmed, color-matched composite is then injection-molded around the tooth, flowing into the space to build a smooth, convex emergence that gently fills the triangle and supports the gum papilla. Finally, everything is shaped and polished to a high, stain-resistant shine. The result blends seamlessly with your own enamel, and because the contours are smooth and closed, the area is actually easier to keep clean than the open gap was.
- Bioclear Matrix System — anatomic clear matrices designed specifically to close black triangles
- Biofilm removal first, so the composite bonds reliably and lasts
- Heated, injection-molded composite for a seamless, gap-free, natural contour
- Usually no drilling and often no anesthetic — healthy tooth is preserved
- High-shine polishing for a smooth, stain-resistant, easy-to-floss result
Why patients choose us for this
Minimally invasive
Black triangle closure adds composite to the tooth rather than grinding it down — so healthy enamel is preserved, and treatment is often done without anesthetic.
Natural, seamless look
Warmed, color-matched composite is shaped to blend with your own teeth, filling the dark gap with a smooth, natural contour.
Easier to keep clean
Closing the open space and supporting the gum creates a smooth surface that’s simpler to floss than the food-trapping triangle it replaces.
Tooth-preserving alternative
For the right case, Bioclear can address black triangles without the tooth reduction that veneers or crowns require.
Durable and stain-resistant
Polished Bioclear composite is strong and smooth, holding its shine well with routine care and regular checkups.
Often a single visit
Many black triangle cases can be completed comfortably in one appointment in our Kentfield office, with little to no downtime.
What to expect
Consultation & assessment
Dr. G examines your teeth and gums, identifies why the black triangles formed, and confirms whether Bioclear closure is the right fit — addressing any gum health concerns first.
Cleaning & preparation
The tooth surfaces are gently cleaned to remove biofilm so the composite bonds reliably. In most cases there’s no drilling and no anesthetic needed.
Injection-molding the contour
Clear anatomic matrices are placed and warmed, color-matched composite is injection-molded around the teeth to fill the gap with a smooth, natural shape that supports the gum.
Shaping, polishing & review
Dr. G refines the contours and polishes everything to a stain-resistant shine, then checks your bite and shows you how to floss and care for the area.
Is black triangle closure right for you?
Black triangle closure is often a good option if dark gaps near your gumline bother you cosmetically or trap food, and your gums and teeth are otherwise healthy. Because black triangles can be tied to underlying gum or bone issues, Dr. G will first look at why the space is there — if active gum disease or significant recession is involved, that’s addressed first so your result is healthy and lasting. The best way to know is a quick consultation, where Dr. G can assess your teeth and tell you honestly whether Bioclear, or a different approach, will serve you best.
- You have one or more dark gaps between your teeth near the gumline
- Food gets caught in the spaces or they’re hard to keep clean
- Your teeth shifted after braces or Invisalign and left small triangles
- You’d prefer a conservative option that preserves your natural teeth
- Your gums are healthy, or any gum issues are being treated first
Frequently asked questions
Black triangles — open gingival embrasures — form when the gum no longer fills the space below the point where two teeth touch. Common reasons include gum recession or bone loss, naturally triangular tooth shapes, a thin gum biotype, tooth movement after orthodontics, and aging. Dr. G will identify the cause before treating.
Bioclear uses specially shaped clear matrices and warmed, injection-molded composite to rebuild smooth, gap-free contact between the teeth. Unlike older bonding, it wraps the tooth and is placed slightly below the gumline, creating a natural contour that supports the gum and resists staining.
Most patients find it very comfortable. Because Bioclear adds composite rather than drilling the tooth, treatment can often be done without any anesthetic. There’s typically little to no downtime afterward.
Veneers usually require removing some healthy enamel and are made in a lab, while Bioclear black triangle closure is minimally invasive, preserves your natural tooth, and is completed directly in the office. For black triangles specifically, Bioclear is often the more conservative choice — though Dr. G will tell you honestly if veneers would suit your goals better.
Polished Bioclear composite is durable and stain-resistant, and results can last for years with good home care and regular checkups. Like any dental work, longevity depends on your habits and oral health; small touch-ups are straightforward if ever needed.
Gum health comes first. If active gum disease or significant recession is present, Dr. G will address that before closing the triangles, so the result is built on a healthy foundation. In some cases a different or combined approach is recommended — we’ll always be straightforward about what will serve you best.
Cost depends on how many teeth are involved and the details of your case. Please call us at (415) 456-5402 and we’ll be glad to talk through your situation and what to expect.