Cats are not good at showing that their mouth hurts. There is no wince and no limp, and the usual first sign is somebody noticing the smell across a room — which is a long way downstream of where anybody would like to start.

PlaqueOff is a powder, not a paste or a brush. ProDen make it from a specially selected seaweed of the Ascophyllum nodosum family, harvested from the seas of Norway and Iceland, and they hold a patent pending on the systemic use of that seaweed for the reduction of plaque and calculus. The routine is one thing: sprinkle it over the cat's ordinary food once a day with the supplied scoop, wet or dry. ProDen report that in trials conducted in Sweden results were seen between 3 and 8 weeks. It is free from artificial colours, preservatives, gluten and sugar, and the tub is 40G.

• 40G tub with a scoop supplied
• Seaweed of the Ascophyllum nodosum family, harvested off Norway and Iceland
• Sprinkled over ordinary food once a day, wet or dry
• Free from artificial colours, preservatives, gluten and sugar
• ProDen report results between 3 and 8 weeks in Swedish trials
• Store in a cool, dry place

One warning on the label reaches us cut off. ProDen's own text says it is "not recommended for animals undergoing treatment for hy…" and the rest of that word has not been supplied to us. We are not going to guess at the end of a word on a health product, so read the tub itself before you start, and speak to your vet first if your cat is on any medication at all. Worth saying plainly too: this is a daily supplement, not a descaling. Calculus already on the teeth is a job for a vet.

Who it's for: owners of a cat that will not tolerate a toothbrush, which is very nearly all of them, and who want something that goes in with the food and asks nothing of the cat.