What is a periapical true cyst? Causes, diagnosis & treatment in 3D A periapical true cyst is a completely enclosed, fluid-filled cavity that forms at the tip of a tooth root due to chronic infection and inflammation in the root canal system. Unlike a periapical pocket cyst, which remains connected to the root canal, a true cyst is entirely separated from the root, making it less likely to heal on its own. 🔬 How does it form? Bacteria from an untreated or failed root canal infection stimulate e