Chews and general chewing will help with general gum health - does your dog get many? Diet will also play a role - what sort of diet is your dog on?
Dental Sticks in my opinion are a waste of money, they are very high in sugar and full of rubbish, they don’t do a lot to teeth as they are fairly soft plus not in mouth long enough to work. You are better off getting a stagbar / fish skin treats (sea Jerky) or raw meaty bones, Also it is good to get your dog used to having its teeth brushed. Might also be worth going to vet to have his teeth checked .
They last at least 3 hours with my dogs as they have the large size ones, K9 still as a dental stick laying around from yesterday, plus all 6 dogs have pearly white teeth x