Discomfort can vary after root planing, but one can expect it to be tender afterward since it's usually in a deeper region under the gums. The teeth themselves can become a bit more sensitive to temperature, and bleeding might occur for a little while.
Over-the-counter painkillers such as Tylenol or Ibuprofen work very well to alleviate discomfort. Brushing and flossing can be done more gently to avoid aggravating any bruised or tender gum areas. Your dentist may recommend salt water or chlorhexidine rinses.
Generally, though, as health returns to your gums, sensitivity and soreness tend to resolve. Remember, though, if diagnosed with periodontal disease, you did not get there overnight, and we cannot treat it overnight. If you are faithful with your home care, it usually will resolve. Successful treatment is 70% what you do at home to treat the disease and 30% when you come in for treatments. Left alone, it will only get worse. If you go through the non-surgical therapy and do not continue with the maintenance therapy, the disease will return.