Major factors in the pathogenesis of cyst formation:
Proliferation of epithelial lining and fibrous capsule
Apical periodontitis → resorption of alveolar bone via immune-inflammatory process
Inflammtory cytokines and growth factors released in apical periodontitis can stimulate epithelial cell rests of Malassez (remnants of Hertwig's epithelial root sheath)
Basal cells of the epithelial cell rests of Malassez are stimulated to proliferate and form the cyst
Hydrostatic pressure of cyst fluid
Cyst fluid (inflammortary exudate and necrotic cellular debris) contains straw-coloured fluid containing cholesterol cystals with protein content >5g/dL
∴ osmostic tension can cause cysts to expand in balloon like fashion
Expansion tends to occur in pathway of least resistance therefore tend to be less destructive
Hydrostatic pressure within cysts is ~70cm of water (higher than the capillary blood pressure)
Resorption of surrounding bone
Cyst tissues have been shown to release bone-resorbing factors (prostaglandin E2 and E3) and collagenases
It is not fully clear what affect these have on cyst growth
Stratified squamous epithelium (non-keratinised) - except when near maxillary sinus where there is respiratory epithelium (pseudostratified ciliated columnar epithelium)
Varying thickness
Lacks well defined basal cell layer (may be missing)
Hyaline bodies and mucous cells may be present ∵ of metaplasia