Back pain is a leading cause of disability in America. A recent article in Orthopaedic Physical Therapy Journal, Vol. 26, No. 4, 2014), discussed back pain commonly seen in dentistry related to static postures. This picture provides a good visual of how even a slight change in posture can affect disc pressure, which can have a huge affect over time. More often Dentists are employing anterior (front) support devices which they lean into while working. This support will allow the back muscles to relax and takes pressure off the disc. The ideal seated posture is leaning back, into a chair back support, so your hip to back angle is 110 degrees.
Static Muscle Activity and Back Pain in Dentistry. Orthopaedic Physical Therapy Practice. Vol 26, No 4, 2014.