There are four separate groups of teeth; incisors, canines, premolars and molars. Each has a distinctive function. The first, incisors, are the smallest teeth used mainly for scraping bones and picking things up. A dog grooms himself by using these teeth to nibble and remove unwanted irritants.
There are twelve incisors, six upper and six lower.
Secondly, canines, commonly known as fangs, are what a dog uses to grab a hold of, sometimes another animal, a bone or a toy. There are four of these, two upper and two lower on the outside of the incisors.
Then there are premolars which are used in chewing. As you will notice, your dog takes the bone or toy from you with his incisors and then moves it around to the side where he will start chewing on it. These were what wild dogs used to rip meat from the bone with. There are sixteen of them, four upper and four lower, behind their canine teeth.
Lastly, there are the molars. These back teeth break down large food like bones or hard biscuits. There are ten of these, two upper each side and three lower each side.
Although canine teeth do not normally decay, they are likely to have gum disease as they age. This can progress into gingivitis, and other periodontal diseases if their teeth are not cleaned.
This is more likely if the dog eats wet food.
There are doggy toothpastes, gels and sprays easily available nowadays to prevent oral ill-health. Your vet can assess the condition of the dog's teeth and recommend appropriate action. Brushing the teeth last thing at night is a good habit to develop. It's best not to have him drink either soon before or after the cleaning.
Putting a little gel or toothpaste on your finger and allowing him to smell and taste it will allow him to relax. Then swipe all the teeth quickly and gently. The gel, spray or toothpaste acts with his saliva to break down the tartar. This may take some time, weeks even, before you feel comfortable introducing the toothbrush. Start with one or two at a time. Be consistent, patient, and praise often.