Shock Doctor vs SISU: Which Mouthguard for Boxing?

The short answer

For a first sparring mouthguard, buy the Shock Doctor Gel Max. A thick, triple-layer boil-and-bite guard with a gel-fit liner is the conventional choice for a reason: there is more material between your teeth and the impact, and "more material" is the entire mechanism a mouthguard works by. Buy the SISU Max instead if bulk is the thing stopping you from wearing a guard at all — a thin guard you actually wear beats a thick one in your bag — or if you have braces. Treat the SISU Aero as a bag-work and light drilling guard, not a sparring one.

What actually differs

Thickness is the whole argument

A mouthguard works by putting a compressible layer between the teeth, spreading the load of an impact across the whole arch, and stopping the lower jaw slamming into the upper. All three of those depend on material. More material does more of each, which is why the thick-guard tradition exists and why every governing body that mandates a mouthpiece for competition is mandating a real one — USA Boxing requires a mouthpiece for all competition bouts under Rule 39.

SISU's counter-argument is that a perforated, closely-moulded thin guard distributes force through the arch rather than relying on bulk, and that a guard you are comfortable wearing is better than one you leave out. Both of those are reasonable. What we will not do is tell you a 1.6 mm guard protects the same as a full-thickness one in a hard round, because nothing published supports that.

Our position: start thick. If you genuinely cannot train with a thick guard — gagging, cannot breathe through combinations, cannot speak to a coach — then a 2.4 mm SISU Max is a sensible answer, and far better than training without one.

Fitting: boil-and-bite versus remouldable

Shock Doctor's Gel Max is a classic boil-and-bite: soften it in hot water, bite in, suck the air out, shape the edges with your fingers, then cool it in cold water. The gel-fit liner makes the mould more forgiving than a plain thermoplastic guard. You get essentially one good attempt, with maybe one rescue.

SISU's guards remould repeatedly — the company publishes up to twenty times — which is the single most underrated feature in this comparison. A first mould that ends up crooked, too high on the gum, or too loose at the back is not a wasted purchase; you reheat it and do it again. For a teenager whose mouth is still changing, or for anyone who has botched a boil-and-bite before, that matters a lot.

Either way, the fitting determines most of the protection. A guard that is loose enough to fall out, or moulded so the back teeth do not sit in it, is not doing its job. Our step-by-step fitting guide covers the process and the three most common ways it goes wrong.

Breathing, talking and the practical side

This is where SISU wins outright and it is not a trivial advantage. A thin perforated guard lets you answer a coach, count rounds out loud and breathe through your mouth during hard work without taking it out. A thick guard does not, and the habit of popping a guard out between rounds to speak is how people end up sparring with it in their glove.

The flip side is that a thin guard is easy to forget you are wearing, which is fine right up until someone lands a clean shot. Decide what you are protecting against before you optimise for comfort.

Braces

SISU's guards are listed as braces-compatible, and the remoulding matters here because orthodontic work changes the shape of your mouth repeatedly over a year or two. The Shock Doctor Gel Max is not the braces model — Shock Doctor makes dedicated braces guards with an instant pop-in fit and no boiling, in upper-only and upper-and-lower versions, which are the right product if you are in treatment.

Do not boil-and-bite a standard guard onto braces: it can lock onto the brackets and it is not designed to protect the soft tissue that braces cut. The full picture is in best mouthguard for boxing with braces.

Durability and replacement

Both wear out, and the usual signs are the same: visible thinning at the back teeth, tears at the edges, a guard that no longer stays put without being held by clenching, or any deformation that stops it seating. A thin guard reaches that point sooner than a thick one, simply because there is less material to lose.

Rinse it after every session, keep it in a vented case rather than a gym bag, and never leave it in a hot car — heat deforms every thermoplastic guard, including the ones that are supposed to be remoulded deliberately.

If neither suits

Two other directions are worth knowing about. A self-fit guard with an internal fitting aid — the OPRO Gold Level, for example — gets closer to a custom fit than a standard boil-and-bite without a dentist visit. And a genuinely custom guard made from a dental impression is the best protection available and costs accordingly. We weigh that up in boil-and-bite vs custom mouthguard, and the full field is in best mouthguard for boxing.