The graft does not die of hypoxia. It dies of distance.

A thick free gingival graft going white in the middle of a denuded root is not a mystery. It is a diffusion problem. You already knew that at the chair. We just keep giving the corpse the wrong cause of death.

I want that to sound slightly rude. It is meant to.

We talk as if grafts die of hypoxia. They do not, or not first. Zhao and colleagues (2017) held dermal fibroblasts at 1% oxygen for forty-eight hours and did not get extra death. The instructive experiment is older and sharper. Deschepper (2011) kept mesenchymal stromal cells alive for twelve days in near-anoxia — if glucose was still in the medium. Withdraw the glucose and they were dead by day three. Plasmatic imbibition works because it delivers glucose and hauls lactate, not because it delivers much oxygen. That is the sentence I want on a surgical tray.

Caveat, because I will not pretend an in-vitro anoxia timeline is an oral fibroblast. Those cells were not harvested from a palatal graft. The direction still holds. Distance from a perfused face is the variable you can still change after the harvest.

Diffusion has a length. Oxygen in tissue is classically a hundred and fifty to two hundred micrometres — Thomlinson and Gray, from tumour cords, still the number everyone borrows. Plasmatic nutrition reaches further: about one to one and a half millimetres from a vascularized edge. A cell within roughly 1.5 mm of a perfused surface will likely survive the forty-eight to ninety-six hours before inosculation. A cell two or three millimetres from every perfused face will not wait for vessels. The middle of a thick exposed graft is that cell. Colour is the report.

The timeline is not folklore. Plasmatic imbibition occupies the first forty-eight to seventy-two hours. Inosculation around day two to four. Functional perfusion around day seven. Complete revascularization of a covered connective-tissue graft around day fourteen. Guiha (2001), in dogs, showed three sources: the periodontal plexus, the supraperiosteal bed, and the overlying flap. Burkhardt and Lang (2005) did the human angiography: about 8% of the graft perfused immediately, 44–53% by day three, 64–85% by day seven, microsurgery sitting at the high end of those ranges. Those are named papers. They are not a device output.

A covered CTG is a sandwich. Two faces roughly double the viable thickness ceiling — about three millimetres of dense lamina propria, if both faces are actually perfused. A thick exposed free gingival graft has one face. That is why the same millimetre count is a different surgery. Fat and gland from a deep harvest die in about twenty-four hours (Eto 2012). Dense superficial lamina propria is the survivor (Harris 2003; Bertl 2015). Millimetres of fat are not millimetres of graft. If you harvest deep because a textbook said thick, you have added a corpse to the middle of a living sheet.

Flap thickness is the second nutrient organ. Hwang and Wang (2006); Baldi (1999) — flaps thicker than 0.8 mm do better, and the number is about perfusion of the covering tissue, not about padding. Tension kills the same capillaries you were counting on (Pini-Prato 2000). A thin, stretched cover is one perfused face pretending to be two.

A papilla aside, because colleagues keep asking and I will not answer with a photograph. Tarnow (1992): the papilla is almost always present when the bone-to-contact distance is five millimetres or less; at six millimetres it is there about 56% of the time. Reconstructing a six-millimetre site is a coin flip plus a graft unless you also move the contact. Papilla reconstruction is the least predictable mucogingival procedure (Patel 2024). Do not claim complete fill. Do not send me a named patient's before-and-after as if geometry had been repealed.

This is educational. It is not a certified thickness, not a CE-marked harvest protocol, not a number you owe a manufacturer. The magnitudes come from the papers named above. The teaching point is distance and glucose. A graft survives on what still reaches it. The rest of the volume is a rumour until a vessel arrives.