Plavix is a blood thinner and I didn't know it affected pressure? Anyway, dental cleaning can produce a tiny amount of gum bleeding and will not produce any problems. I have my teeth cleaned every 6 months and it soon stops bleeding. The problems come if you need a tooth removed. Flycaster is correct, your dentists should always have a list of current medication.
Tell the dentist you take Plavix. If it's a problem with the procedure, he/she will tell you, but I wouldn't quit taking it with talking first to your heart doc.