- American Dental Association
- Louisiana Dental Association
- Northeast Louisiana Dental Association
- Academy of General Dentistry
- Academy of Laser Dentistry
- Dental Organization for Conscious Sedation (DOCS)
Dr. Johnston and his wife, Tami, have been married since 1985 and have one son and one daughter: Jerry and Holly Taylor. In his spare time, he enjoys playing golf, running, reading, and spending time with his family.