I’m putting my “vet assistant” hat on to answer this.
All of these dental sprays and dental chews are made for you…not your dog. Unless it’s a spray to help prevent infection–like chlorhex or something after an extraction. But once a dog has enough tartar and calculus built up, you can’t scrub it off with a tooth brush and you certainly can’t spray or chew it away.
The tool that we use during a dental to get off major calc looks kind of like a nut cracker. This stuff comes off in chunks. Then you scale the teeth with an ultrasonic scaler–just like at your dentist. Then you tackles the finer areas with a hand scaler–just like at your dentist. Most humans get their teeth cleaned frequently enough and do a good enough job at daily brush and floss that they don’t need major scaling but for some, it’s a matter of genetics and it’s just part of the deal for them. Similarly, some pets have issues no matter what you do.
All that said, the ONLY way to decrease the need for dental cleanings (genetics and soft food aside) is to stay on top of daily brushing to physically remove what you can. Most people can’t/won’t do that. Hell, I don’t do it. But buying a spray is not likely to help at all. If you’re going to get all up in your dog’s business daily to use a spray, then commit to brushing instead. It will actually help.
My two cents.
Now…I’ve also been really blessed with dogs with great genes who really haven’t needed frequent cleanings. I had a dog (just passed this fall) who I used to ask about every time “Is he ready for a dental!!!” Because I could NOT trim his nails to save my life. And sadly (actually great), he really never “needed” a cleaning. Not in 13 years. He go one once because we needed to knock him out to do rads and I asked that it be done, but the vet didn’t think it was quite necessary yet. Sigh.
But I’ve had patients at various clinics who needed them every 4-6 mos by age 3. A lot of it is genes. Smaller breeds especially seem to have dentition issues that require more attention.
But the spray? No. I wouldn’t waste my money or my time applying it if it were free. Sorry!