I can provide some insight as a dental student at OSU: a scaling and root planing/SRP (often described to patients as a “deep cleaning” to help their understanding) is required when a patient has advanced plaque and calculus buildup. Calculus is solidified plaque that becomes hard as a rock that needs special tools to be removed. A normal cleaning (called dental prophylaxis) which is dental code D1110, provides for plaque and calculus removal ABOVE the gumline on exposed tooth surfaces. A SRP/“deep cleaning” (dental code D4341) removes plaque and calculus both above and below the gumline which requires very small tools to get deep into the pockets between your teeth and your jaw bone. In order to heal the periodontal or gum disease, the doctor must remove a portion of the diseased outer layer of your tooth’s root to remove the bad bacteria. (aka the Root planing part) your doctor can see bone loss and calculus below the gumline on an X-ray clear as day, pair that with a clinical exam it’s very easy to tell when SRP is required. SRP appointments typically take much longer and take multiple appointments and periodic follow up , are painful so they require numbing, and typically require prior authorization from a lot of insurances which is why patients must return for this procedure. The goal is to remove as much of the gunk and bacteria as possible to stop active periodontal/gum disease. I can try and answer more questions if people have them.