Boar vs Horsehair Toothbrush: The Difference Is Bristle Diameter

That measurement is the thickness of a single bristle. The boar bristles on our brush run roughly 80–150 microns across. The horsehair runs roughly 50–80. Horsehair is, in round terms, about half the diameter of boar. Everything a bristle does in your mouth — how hard it pushes, how much it flexes, how much scrub you feel — follows from that number. Nothing else about these two brushes differs in a way you would notice.

A bristle is a cantilever. Push it against a tooth and it bends; the thinner it is, the more it bends for the same pressure. A thicker bristle stays straighter, so more of your hand pressure arrives at the tooth surface as scrubbing. A finer one gives way earlier, so more of that pressure is absorbed by the bristle flexing rather than delivered into your gum margin. This is why the horsehair brush feels gentler and, to some people, feels like it is doing less. It is doing less — to your gums. Whether it is doing less to your plaque is a separate question, and the answer is mostly no.

Both bristles share the property that matters most against nylon: a naturally tapered tip. Hair grows thinner toward its end. Nylon filament is extruded at a constant diameter and then cut to length, which leaves a blunt circular face with a cut edge. That edge is what abrades tissue, and it is present on nylon brushes at every firmness rating, including the ones sold as soft. Neither of our brushes has a cut tip, because neither bristle was cut to make the tip.

This is the question people actually want answered, and it is worth being precise rather than reassuring. A systematic review by Ranzan, Muniz and Rösing looked at whether bristle stiffness and tip shape drive soft-tissue damage during brushing, and found that softer bristles tend to be the safer choice for gum tissue. What it did not find is a large cleaning penalty for going softer. Within the narrow range these two brushes occupy, softness costs you very little and protects tissue that does not grow back.

Not as far as the one controlled trial we can find is concerned — and it goes against the natural bristle. Arai and colleagues (1977) compared natural pig bristle against nylon in twelve adults and measured disclosed plaque: nylon removed 59.6% against 42.3% for the natural bristle, a difference that reached statistical significance. It is a small, unblinded study from 1977, published in Japanese, and nobody appears to have repeated it in the half-century since — so it is thin evidence rather than a settled answer. But it is the evidence that exists, and we would rather hand you a result that does not flatter us than pretend the question is open. What is better supported is that softer bristles are the safer choice for gum tissue (Ranzan, Muniz and Rösing, 2019), and that how you brush matters more than what the bristles are made of.

So the honest summary is that both clean adequately, the difference between them in plaque terms is small, and the difference in how much they abrade your gums is real. If you are choosing on cleaning power alone, you are optimising the variable that matters least.

The plainest version of the rule: boar is our soft, horsehair is our extra soft. If nobody has ever told you to brush more gently, boar is the one most people get on with. If a dentist has mentioned recession, sensitivity, or brushing pressure — or if you press hard without meaning to — take the horsehair and stop thinking about it.

Both handles are uncoated moso bamboo. No polyurethane lacquer, no paraffin wax, no sealant — which matters because a coating is a petroleum film sitting against your lips twice a day, and because uncoated bamboo keeps its own antimicrobial behaviour rather than having it sealed under a finish. Both handles darken slightly with use. That is tannin oxidation in the wood, not decay, and it is the single most common thing people write to us about.

Both heads are pressure-fitted. Each tuft is compressed into a hole drilled slightly smaller than the tuft, and the bamboo grips it by friction alone. There is no epoxy, no polyurethane, no hot-melt adhesive — which is what holds the bristles into the large majority of bamboo brushes on the market, and which is almost never disclosed anywhere on the packaging or the product page. If you want to test that claim, pick up any bamboo brush and try to find out what is holding its bristles in. The answer is rarely printed anywhere.

Both are fully compostable — handle in about six months in soil, bristles in twelve to eighteen. Neither sheds microplastics, because there is no polymer in either to shed. Both are 19cm and about 12g. Both should be replaced every two to three months, on the same schedule a dentist would give you for any brush. If you are working through the rest of the bathroom shelf on the same logic, our guide to oral care chemicals covers what else is worth checking.

Natural hair holds water. Both brushes need to dry upright between uses, and a sealed plastic travel case is the worst possible place to keep one. This is a genuine practical difference from nylon, which does not care. It is one step, but it is a step, and if you will not do it you will be happier with something synthetic.

Both bristles are animal-derived. Boar bristle is a by-product of pig farming and horsehair is tail hair; neither is vegan, and no amount of framing makes them so. If that rules them out for you, it rules them out, and we would rather say it here than have you find out at the end of a product page. There is also natural variation between batches — hair is not extruded to a tolerance — so bristle colour and stiffness shift slightly from brush to brush.

And a new natural-bristle brush sheds the odd loose bristle in its first few uses. That is normal for pressure-fitted hair and settles quickly. It is the second most common thing people write to us about, which is why it is in this article rather than buried in a returns policy.