I have a 13 year old Samoyed and have found the following regimen to be successful.
a) I add the Zymox water additive to his water bowl every AM and PM when I refill his bowl. I really noticed a difference in his breath which became noticeable worse when he turned 11 yrs old. This made a surprising positive difference.
b) 2-3 times a week I try to brush his teeth with Drs. Foster & Smith's Tartar Control toothpaste. I must admit sometimes I only do it once a week or when really busy twice a month but I use an old Sonicare electric toothbrush and recycle our used brushheads to brush his teeth. I pay particular attention to the gum line.
c) Once or twice a week after brushing his teeth, I treat his mouth with a rinse containing 1% Chlorhexidine . Use a spray, sponge or dip a toothbrush in the solution and apply to gums and teeth. I like to use the Petrodex 16 oz Water Additive because it's more affordable even though it's not marketed to be used in this manner. Other alternatives are Drs.Fosters & Smith Dental Cleanser Spray or Solution 8 oz and CET .12% Chlorhexidine Rinse 8 oz..
d) If any plaque or calculus forms I use a dental tool and carefully & gently scrape it off then rinse with .1% Chlorhexidine.
I developed this regimen over the past 12 years adding and adjusted it as products and needs evolved. During this time I've only had my dog's teeth cleaned by my veterinarian twice (@ 2yrs and 8yrs old). At 13 yrs old his teeth & gums are healthy and his breath fresh as long as maintained as outlined above. Removed 2 of his small front teeth @ age 8 yrs but that was due to never brushing them--hadn't thought it necessary. Two missing teeth and a large vet bill, I know better now and ALL his teeth get brushed. My veterinarian told me it is unnecessary to brush the inside of the teeth because the saliva rinses them so I haven't-- so far it seems fine.