Complementary response to inflammation
Chemical reaction with Interleukin and Prostaglandin

Mechanisms
Periapical cysts develop due to an inflammatory stimulus in 3 stages:
Initial stage: Epithelial cells from the rests of Malassez at the apex of the roots of a non-vital tooth (one where the nerve and blood supply in the tooth have degenerated and no longer exist) become stimulated due to the bodys inflammatory response to bacterial endotoxins infecting the pulp or as a direct response to necrotic pulp tissue, therefore re-entering the growth phase. Bacterial byproducts then are able to seep into the periapical region through the infected pulp. Cyst development stage:  Epithelial cells form strands and are attracted to the area which contains exposed connective tissue and foreign substances. Several strands from each rest converge and surround the abscess or foreign body. Cyst growth stage: Fluid flows into the cavity where the forming cyst is growing due to the increased osmolality of the cavity in relation to surrounding serum in capillaries. Pressure and size increase.The definitive mechanism by which cysts grow is under debate; several theories exist. Biomechanical theory
Pressure and concentration differences between the cystic cavity and the growth surroundings influence fluid movement into the cyst, causing size increase. Biochemical theories
a. Collagenase (breakdown of collagen) in the jaw bone leads to bone degeneration, providing room for cysts to develop. Substances released by the bodys immune system as a result of the connective tissue breakdown, such as cytokines and growth factors, contribute to the mobilization and proliferation of epithelial cells in the area. b.
A third patient had been referred to by L. Emmett Holt, Jr. and Rustin McIntosh in a textbook of pediatrics (Holt and McIntosh, 1933) and was included in full in the paper by Ellis and Van Creveld (1940).McCusick et al. (1964) followed up with a study of its incidence in the Amish population. He observed the largest pedigree so far, in an inbred religious isolate, the Old Order Amish, in Lancaster County, Pennsylvania. Almost as many persons were known in this one kindred as had been reported in all the medical literature up to that time. Nomenclature
Six-fingered dwarfism (digital integer deficiency) was an alternative designation used for this condition when it was being studied in the Amish and may have served a useful function in defining this then little known condition for the medical profession, as well as the lay public. The term, however, has been found offensive by some because of the reference to the polydactyly, which is seen as a freakish label. For this reason, six-fingered dwarfism has been removed as an alternative name for this entry. This leaves Ellis–Van Creveld syndrome with its initialism, EVC, as the only satisfactory designation. Chondroectodermal dysplasia and mesoectodermal dysplasia do not well define the entity and are not satisfactory for general usage, either medical or otherwise. References
External links
 Media related to Ellis–van Creveld syndrome at Wikimedia Commons