I adopted Max 2 months ago and am getting him out of his habit of chewing stones, he has obviously had this habit for a while as he has broken teeth, how can i look after his teeth?
Dogs are like humans in that they have 2 sets of teeth in their lifetime and they lose their baby teeth at around 5-6 months old. So they need to be looked after as well as possible to last their whole life. Broken teeth are only are big problem if the pulp of the teeth are exposed because it provides bacteria in the mouth access to the blood circulation. This can lead to infections anywhere in the body. A check by your vet should be able to let you know if the degree of damage is serious and appropriate treatment if necessary.
General dental hygiene for dogs is important. Brushing their teeth with just a regular toothbrush is the best way to remove plaque. Toothpaste is not necessary as it is the physical brushing that is important, but if you want to use some make sure it is safe for dogs because they can't spit it out! To be effective it needs to be done at least once a day.
An alternative is to give dogs big raw meaty bones to chew on. I like to give my dog cannon (or shin) bones to chew on as these are too big for him to swallow, but once he's removed the meat I take it off him. You want them pulling the meat off the bones but not actually chewing and breaking the bones.
There are chew toys and other treats that work well too.
Your vet can scale and polish your pets teeth too, but needs to be done under a general anaesthetic. If teeth are rotten they may be to be removed. This sounds extreme but diseased teeth are just as painful for our pets as they are for us, and they do amazingly well without them! Some vets may even be able to perform more specialised procedures such as root canals.