Our Doctors

All professionals at ADA Adult Medicine Clinic maintain the highest levels of accreditation and pursue ongoing education to stay abreast of the latest trends in the medical field. Read on to learn more about our staff's experience and training.

Gary L. Paddack, M.D.

Gary L. Paddack, M.D., practicing general Internal Medicine, graduated from the University of Texas Medical School at Houston, board certified with the American Board of Internal Medicine since 1980. 


Bruce W. Dennis, M.D.

Dr. Dennis moved to Ada Oklahoma in 1995 after completing his residency in Internal Medicine at the University of Oklahoma.  He is a graduate of Norman High School, Abilene Christian University, and OU College of Medicine.  He has been married to his wife Sheri since 1988 and together they have four children.  Dr. Dennis is an outdoorsman and enjoys ranching, hunting and fishing.  He is an elder for Fittstown Church of Christ and has done relief work in Haiti since 2000.  


Joshua Corley, PA-C, MPAS

Joshua D. Corley, P.A. -C, Master of Health Science as Physician Associate Degree from the University of Oklahoma Health Science Center, Bachelor of Science in Biology from East Central University, certified in BLS, ACLS.



Mona J. Nickerson, MSN, APRN, FNP-C

Mona J. Nickerson, MSN, APRN, FNP-C graduated from the University of Oklahoma Health Science Center with her Bachelor of Science in Nursing in 2009, and from the Nurse Practitioner Program in 2014. She is a Certified Medical Examiner through the Department of Transportation and also certified in the American Academy of Nurse Practitioners and Basic Life Support


Tiffany Wilson, PA-C

Tiffany Wilson, PA-C, graduated from Texas Tech University Health Science Center with a Master Degree in Physician Assistant studies, certified in NCCPA, ACLS, BLS.


Michel Cosby

Bio Coming Soon.


Sheila Miller, APRN-FNP-C

Sheila Miller, APRN, Masters degree in Advanced Practice Nursing (Family Practice) from Maryville University in Missouri, Master of Science from the University of Oklahoma 2011, certified in ACLS, BLS. Sheila joined the practice in May of 2016. She is a certified family nurse practitioner through the American Academy of Nurse Practitioners. She worked as a registered nurse in the areas of psychiatric mental health, home health and Long-Term Care. She served Active Duty, in the United States Army from 1992-1996. Sheila has been married to her husband, Shane, for 15 years. They have two sons, two daughters, and two granddaughters.


Mandy Waters, APRN-CNP

Mandy Waters, APRN-CNP, graduated from Maryville University with a Master of Science in Nursing-FNP,  Bachelor of Science in Nursing, from East Central University, certified in ACLS, BLS, PALS, and TNCC. Mandy is married to Jerod Waters and they have two daughters who keep them busy with a lot of activities and sports. Mandy has lived in this area most of her life and enjoys caring for patients in her hometown.


Aleicia Mack, D.O.
Cardiovascular Diseases and Non-Invasive Cardiology

Bio Coming Soon.


George Madden, M.D.
Invasive Cardiology

Bio Coming Soon.