Dr. Johnston was born in Vestavia Hills, Alabama, and moved to the Dunwoody area in middle school. He graduated from Dunwoody High School (1978) and the University of Georgia (UGA) where he received a Bachelor of Science in Biology (1978-1982). At UGA, he was involved in many activities including Phi Gamma Delta Fraternity and Student Judiciary. In 1982, he entered the Medical College of Georgia in Augusta, and received his Doctoral in Dental Medicine (D.M.D.) in 1986. After dental school, Dr. Johnston continued his education at the University of Alabama at Birmingham (UAB). He completed a Hospital Dentistry Residency where he received a certificate in Hospital/General Practice Dentistry. In 1988, Dr. Johnston was a Research Assistant for the Department of Oral and Maxillofacial Surgery under the direction of the Chairman of the Department; and during the same year, he was a Clinical Instructor for the UAB Department of Restorative Dentistry. In 1991, he completed his three year residency program and received his Masters of Science and his Certificate in Orthodontics from the UAB School of Dentistry.

In 1991, Dr. Johnston moved back to Atlanta and opened his orthodontic practice in Marietta. In 1999, he moved his office to the current location on Woodlawn Drive. He was very instrumental in the development and design of this office. He wanted the office to have a pleasant and fun atmosphere for both patients and their families. In 2001, Dr. Johnston earned his Board Certification from the American Board of Orthodontics. In order to receive this certification, an orthodontist must complete an intensive case presentation and examination. Approximately 23% of the orthodontists in the United States are Board Certified.

Dr. Johnston is committed to furthering the future of Orthodontics with his involvement in several dental councils and organizations. He is the Past President of the Georgia Association of Orthodontists (1999), and past Editor of the Southern Association of Orthodontists News (SAO News) (2000-2002), the official publication for the 11 southern states . He is presently a Board Director of the Georgia Association of Orthodontists Educational Foundation (1999-current) and a past Delegate-at-Large for the American Association of Orthodontists (2000-2003) representing Georgia, Florida and North Carolina. Presently, he is on the Executive Committee for the SAO. Dr. Johnston is a member of the American Association of Orthodontists, the Southern Association of Orthodontists, the Georgia Association of Orthodontists, the American Dental Association, the Georgia Dental Association, the Hinman Dental Society, the College of Diplomates of the American Board of Orthodontics. He is a fellow in the Pierre Fauchard Academy and the American College of Dentists.

Dr. Johnston is very active in the local community. He is currently a Partner in Education for Sope Creek Elementary School (1998-current), Dodgen Middle School (1993-current), and Dickerson Middle School (2004-present). He is involved with his church and has participated dental mission trips to Peru, Mexico, and Honduras. He is involved with an "inner-city" ministry called Eagle's Nest. In the past, he has been a volunteer with "Rainbows" (an international organization designed to assist children and adults who have experienced loss of a loved one from death or divorce), in many capacities including being a member of the Executive Council. He has also been involved in the Rotary Club of East Cobb, Cobb Chamber of Commerce, and Citizens Advisory Committee for several Cobb County Schools.

Dr. Johnston enjoys many hobbies which including golfing, hunting, fishing, jogging, boating, and visiting the North Georgia Mountains with his family.

Dr. Johnston resides in East Cobb with his wife (Helene), three daughters, (Taylor, Chandler and Bailey), their newest arrival and son (Watts), their two Labrador Retrievers (Smokey and Caesar), and cat (Raja).