I am currently undergoing treatment for periodontal disease. I began noticing the gums receding from the teeth after about a week of using an interdental brush (around the lower left and right central/lateral incisors and canines), which my dentist recommended. Could the interdental brush have caused this?

Dear Sir/Madam! The use of an interdental brush certainly did not cause the gum recession. The advice was appropriate; use probably began somewhat too late, so the recession is a consequence of reduced gingival edema that had persisted because of ongoing inflammation. The inflammation is most often caused by the accumulation of bacterial plaque. Have a nice day!