Im 70 years old ive just started dribbling from my mouth can you give me any reasons why?

I'm 70 in August and have the same problem. I might be reading or watching tv and realize I'm dribbling. Asked my dentist today and he said its part of aging. He said a worse problem is those that age and saliva dries up -- it causes severe dental problems (cavaties), so maybe we are better off. Did you get an answer from anyone that made good sense? I would like to know what the responses were also.