The Complete Handbook of Dental Floss

Chapter 1: Understanding Dental Floss

Dental floss is a thin, flexible strand or tape—typically between 0.5 and 3.0 millimeters in diameter—designed to remove plaque, food debris, and biofilm from the interproximal spaces between teeth. It is the primary mechanical tool for cleaning areas that a toothbrush cannot reach, and it remains the clinical standard for interproximal oral hygiene despite nearly a century of competing products.

To understand why floss matters and why it has persisted as a tool despite countless alternatives, you must first understand the anatomy it addresses. The interproximal space—the space between two adjacent teeth—has a specific geometry. The contact point between teeth (the place where their surfaces touch) sits approximately 5 to 6 millimeters below the occlusal surface (the top of the tooth, where chewing occurs). Below that contact point, the embrasure space widens as you move toward the gingival margin (the edge of the gum). The tooth surfaces facing the interproximal space are curved and concave, not flat. A toothbrush bristle, even a tapered one, is typically 0.2 millimeters in diameter at its tip. It cannot physically enter the tight embrasure space beneath the contact point.

Plaque—a sticky biofilm of bacteria and their metabolic byproducts—accumulates in this space rapidly. Within hours of brushing, bacteria begin colonizing the interproximal area. Within days, if left undisturbed, plaque hardens into calculus (tartar), which a toothbrush cannot remove. This is not a matter of technique or force. The brush simply cannot reach there. Floss can. A strand of floss, being