Why do thin biotypes receede?

Thin gingival biotypes are notorious for their fragility and predisposition to recession. When examining the blood supply to the gingiva it reveals some interesting points. Blood supply to the gingiva occurs mainly through the periosteum however the papillae have a more rich and varied supply. It receives blood flow from the periosteum, periodontal ligament, surrounding tissue and crestal bone. When viewing the crestal bone through a microscope you will notice small arterioles exiting at the crest to supply the soft tissue. Incidentally this is the site that allows intraosseous infiltration without drilling into the bone. Blood supply is the most important consideration when handling soft tissue and techniques about handling and flap design all take this into consideration.

Many people when viewed on a CBCT will show inadequate buccal bone coverage with severe dehisence almost to the apex of the tooth. The buccal of a tooth is also the site with the least keratinised and attached tissue. This can be seen after giving LA as the attached tissue will be located at the edge of the "LA bubble". This also explains why most recession defects are on the buccal of a tooth. Thick biotypes have a significant thickness of tissue in a buccolingual dimension. There is plenty of blood supply to the surface tissue from the underlying tissues. This is not the case in thin biotypes as their fragile nature means that the surface tissue is supplied directly by the periosteum. In cases of inflammation i.e toothbrush abrasion or cord packing, thick biotypes will be damaged but have sufficient blood supply to heal and recover and the tissue will simply grow back however, in thin biotypes this inflammation will result in the necrosis of the marginal gingiva and as there is no supporting bone, the periodontal complex will shrink back towards the biologic width resulting in recession. The only thing that will stop this recession is the height of bone which is quite far apically in some cases.