Yet another post on supra and subgingival calculus

Today as I stared at an extracted upper 8 covered in subgingival calculus, I mused on the difficulties of non surgical periodontal therapy. Removal of bioburden to the periodontal tissues is one of the long standing main aims of the treatment of periodontal disease. I don't dread treating perio but what puts me off is how difficult it is to do it well. I believe that if you are doing something you should do it right but perio is one of those tricky fields where things are stacked against you...

• Subgingival anatomy is hard. On the extracted tooth I held there was a multitude of anatomy unrecognised on simple 2D films. There was tight furcations between narrow roots, the interproximal root surfaces were concave and sloped upwards towards a very bulbous CEJ. I would imagine that I would spend quite a bit of time cleaning around this anatomy on the extracted tooth (and this is out of the mouth!)
• Of course the tightest spots are usually interproximal where the gingiva and neighbouring tooth are often in the way. Periodontal treatment would be so easy if the patient had no teeth to make things difficult.
• As far as I can tell, the texture of supragingival and subgingivalcalculus have very different structure and textures. 
• Supragingival calculus is readily visible, chalky white and crumbles easily. A bit like scooping an ANZAC biscuit out of its wrapper, you can break it up and chip it off in pieces. There is often a microscopically thin film left behind after you chip the main bulk off which can be seen on a dry tooth and can be easily removed with a hand scaler. Leaving this rough surface surely will accelerate the regrowth of calculus
• Subgingival calculus by contrast is like scraping off wet bread superglued to the kitchen bench... with a toothpick. It is far thinner due to the less varied microbes involved in its construction (more pathogenic, less structural and less cooperative) and the narrow space to grow in the subgingival environment. Therefore one area of calculus is "less connected" to its neighbour and chipping large chunks off is less likely. It is also somhow simultaneously weaker and tougher. It seems to be less brittle than supragingival calculus in that scraping against it will remove the surface layer and burnish the calculus but it seems to attach to the tooth much stronger than supragingival calculus. Possibly this is due to the difference in mineral composition in GCF and saliva?
• Subgingival also tends to be dark due to exposure to blood products and pigment producing bacteria such as P. gingivalis. This also happens to be obscured in the dark subgingival environment and in blood.

Perio is one of those fields that has fairly straightforward concepts but has been made very complicated due to intense research into the minutia of pathogenesis and aetiology. If we go back to first principles, its treatment is fairly straightforward. The importance of addressing modifying factors such as smoking and diabetes cannot be separated from addressing modifying factors by clearing calculus and instructing hygiene. However, the removal of calculus will always have its own clinical challenges that must be overcome by persistence and education. I will continue to study the teeth I extract and note patterns as to where calculus removal has failed and pay a keener eye to root surface anatomy in an attempt to improve my skills at negotiating them.