The incidence of epithelium in periapical granulomas and the mechanism of cavitation in apical dental cysts in man

Experimental evidence supports the abscess theory of development of radicular cysts

“…But, none of the control cages that received only epithelial cells showed the development of cyst-like pathology, an observation that would with limitations discredit the theory of central epithelial necrosis. (10,11) This means that the establishment and proliferation of epithelium was more successful in trial cages, probably due to the influence inflammatory mediators and growth factors released during the inflammation (16,18,19) as a consequence of the bacterial inoculation. Our additional, limited data (not included here) showed that pure cultures of Actinomyces israelii or a mixture Porphyromonas endodontalis and…”

“…(1,5) Many authors attempted to explain the pathogenesis of apical cysts. (7)(8)(9)(10)(11)(12)(13)(14) The formation of the cysts has been described as taking place in three stages. (15) During the first phase the dormant epithelial cell-rests proliferate, probably under the influence of inflammatory cytokines and growth factors (16)(17)(18)(19) that are released by various cells residing in the apical lesion.…”

“…There have been two long-standing concepts regarding the formation of the cyst cavity. (1) The concept of central necrosis (10,11) of the epithelium assumes that the central cells of the epithelial mass get removed from their source of nutrition and undergo death and degeneration. The products in turn attract neutrophilic granulocytes into the necrotic area.…”

“…Such micro cavities containing degenerating epithelial cells, infiltrating leukocytes and tissue exudates coalesce to form the cyst cavity lined by stratified squamous epithelium. (2) The abscess theory (28) rests on the assumption that the proliferating epithelium surrounds an acute inflammatory focus (abscess) or necrosed connective tissue segment (11) because of the innate nature of epithelial cells to cover exposed connective tissue surfaces. Recently it has been suggested (17) that the proliferating epithelial strands may merge three-dimensionally, 'trapping' islands of inflamed connective tissue that degenerates due to a "loss of blood supply" to form eventually the cyst cavity.…”

“…Although the epithelial tissue has no vasculature, the inflamed periapical connective tissue, except for abscessed/necrotized areas, is well vascularized. It is quite unlikely that an area of inflamed but vital periapical soft connective tissue would be strangulated (17) or thrombosed (11) to death by the proliferating epithelium.…”