My brother gets his teeth scaled and polished four times a year. is there any detrimental effects of it on teeth?

No: People who have periodontal disease need to have their teeth cleaned 4 times a year. There is also a genetic component to periodontal disease. If your brother has it you should also be checked. Hopefully you are having periodontal charting to follow your gum health. Ask your dentist to be sure.

No: Usually, getting your teeth professionally cleaned twice a year is enough, but in some cases, like gum disease, you need to have the scaling done 4 times a year to help keep the disease under control.

Usually not: But there are some reports of a heavy-handed hygienist over many years of treatment, that can damage the root surfaces of the teeth.