Toothbrush

A home-made brush is a teaching object. Do not put it in your mouth — natural bristle and untreated wood harbour bacteria and cannot be sanitised. All the tests below use a model, not teeth.

Wadsworth claims "separating the bunches of bristles more than in the common brush" to give elasticity and let them enter between the teeth. Spacing is the claim, not softness.

Glue a curved row of wooden beads or dowel offcuts to a base, leaving 1 mm gaps. Coat them with a thin layer of coloured modelling clay to stand in for plaque.

Use any stiff flat-headed brush and ten strokes. Photograph the result. The tops are clean and the gaps are untouched — that is the failure being fixed.

Cut a hardwood strip about 170 × 15 × 8 mm. Long enough to reach the back molars without the hand blocking the mouth.

Shape the head into a shallow arc in plan view, following the curve of a dental arch. Hold it against your model — the arc should match.

Carve a shallow lengthwise hollow into the face that will carry the bristles. This is what lets the tufts wrap the oval of a tooth instead of touching its crown only.

Taper the back of the head to a slim rounded section. Wadsworth wants it to slip between the cheek muscle and the molars — a thick head simply will not go there.

Drill 2 mm holes in two staggered rows with generous gaps between them. Resist the urge to pack them — the spacing is the invention.

Fold a small bundle of natural or nylon bristle over a fine wire staple and pull it tightly into each hole. Each tuft should stand upright and independent.

Cut the tufts nearest the tip shorter, and angle them so they project past the end of the head. The patent specifies this — it is how you reach behind the last molar.

Ten strokes with your brush on a freshly coated model, photographed the same way as step 4. Compare how much clay is removed from between the beads.

Push one tuft onto a bead and watch it spread around the curve. Now push a tuft in a densely packed brush — its neighbours hold it rigid. Space is what allows flex.

Wet the bristles and leave the brush lying flat. Natural bristle stays damp for hours because it is hollow — note that, because it is the reason the material had to change.

The patent. US 18,653, "Tooth-Brush", granted 17 November 1857 to H. Nichols Wadsworth. Application and grant share a date, so only the grant is cited.

⚠ This is the first American toothbrush patent, not the first toothbrush, and the difference matters. Bristle toothbrushes were made in China by the fifteenth century using hog bristle set into bone or bamboo, and mass production in Europe dates from William Addis in England around 1780 — the standard account has him drilling a bone with holes and tufting it with bristle while in prison. Wadsworth's contribution is a shaped brush: curved to the arch, concave to the tooth, wedged at the back, and above all spaced rather than packed. Everything he claims is about geometry.

Why spacing beats density. The instinct is that more bristle cleans more, and it is wrong. Bristles clean by bending around a surface and dragging across it; a bristle that cannot bend simply presses. In a dense block, each filament is braced by its neighbours, so the whole head behaves like a stiff pad and rides over the tops of the teeth. Separated tufts are free to splay, so they follow the curve of the enamel and enter the interdental gaps where decay actually starts. Step 13 shows this directly, and it is why modern brush heads still use discrete tufts with visible gaps rather than a continuous field.

The material was the unsolved half. Wadsworth had only animal hair — usually hog bristle, which is hollow, absorbs water, dries slowly, holds bacteria, softens unpredictably and falls out. Step 14 demonstrates the problem in one night. It was not fixed until 1938, when DuPont's nylon gave a solid, non-absorbent, uniformly stiff filament that could be cut to a controlled length and rounded at the tip. Nylon is arguably a bigger improvement to toothbrushing than any change in head shape, and it came eighty years after this patent.

Brushing was not yet a habit. Regular daily toothbrushing did not become normal in the United States until the mid-twentieth century, pushed hard by army hygiene training during the Second World War. A patent in 1857 is therefore for a minority product; the Roman tooth powders elsewhere in this collection served a population that mostly cleaned teeth with cloth, twigs and abrasive powders, if at all. The object arrived long before the practice.