Some dogs are genetically prone to gingivitis and tooth loss. I am currently dealing with my 9yr old Maltese, on Monday he goes in for more teeth to be pulled.
Generally if the breath really smells bad, its the bacteria getting under the gums causing inflammation. The gums will then begin to recede. (According to my vet, some dogs develop more mouth bacteria than others, no matter how much you brush the teeth.) Eventually gingivitis leads to tooth loss. You should let your vet know if your dog has any loose teeth now or in the future.
All you can do is brush his teeth well every day, use tartar sprays on his teeth. Have your vet clean the teeth once a year. Have your vet remove any loose teeth as there is infection under these teeth.
I started brushing my dogs teeth when he was 3 months old, and still he has raging gingivitis. I am going to start my dog on Colidal Silver spray on his teeth after Monday, he still has some of his teeth left, I am hoping to save these.