Hello, You can experience oral discomfort from sinusitis. If congested with difficulty breathing, you may tend to breath through your mouth and dry out your tissue. Dry gums can be sore. Post nasal drip can also cause discomfort. Acidic liquid can again bother the gums. It will take time for your inflammation to subside. You are taking a potent drug which tells me you had a great deal Of inflammation. Many patients only require an antibiotic to treat sinusitis. Steroids have many side effects. Sore gums are not a major side effect but may be possible. Make sure you have ruled out an allergic reaction. Keep up with good oral hygiene and make sure to rinse your mouth. Warm saltwater rinses may offer you some relief. Keep well hydrated and be sure to keep a healthy diet without any vitamin deficiencies. If your oral symptoms continue or worsen see your doctor to rule out a yeast infection or other type of oral Imbalance of bacteria that may require additional treatment. Be sure to give your dentist a full medical history concerning your recent treatment and your dentist will be glad to provide needed treatment for your gums. I am glad you have a dental visit planned. I hope you will be feeling better shortly.