XYZ, S.,RE:  ABC,Dear Dr. XYZ,On your kind referral, I had the pleasure of meeting and consulting with ABC on MM/DD/YYYY for evaluation regarding extraction of his mandibular left second molar tooth #18. 
XYZ , S.,RE : ABC , Dear Dr. XYZ , On your kind referral , I had the pleasure of meeting and consulting with ABC on MM / DD / YYYY for evaluation regarding extraction of his mandibular left second molar tooth # 18 .