CHOLESTEROL CRYSTALS AS AN ETIOLOGIC FACTOR IN NON-RESOLVING CHRONIC INFLAMMATION - AN EXPERIMENTAL-STUDY IN GUINEA-PIGS

The presence of cholesterol crystals has been suggested to be a factor interfering with periapical healing after conventional endodontic tre atment. This investigation addresses the role of cholesterol crystals in impairing healing by studying the tissue response to the crystals, which Here implanted in animals. Purl cholesterol crystals, prepared t o a mushy form, were placed in Teflon(R) cages that were implanted sub cutaneously in guinea pigs. The cage-contents were retrieved after 2, 4 and 32 wk of implantation and processed for light and electron micro scopy. The cages revealed delicate connective tissue that grew in thro ugh perforations on the cage-wall. The crystals were densely surrounde d by numerous macrophages and multinucleated giant cells, forming a we ll-circumscribed area of tissue reaction. The cells, however, were una ble to eliminate the crystals during an observation period of 8 months . The congregation of macrophages and giant cells, known to be major s ources of apical inflammatory and bone resorptive mediators, suggest t hat accumulation of cholesterol crystals can be a factor in the failur e of certain apical periodontitis lesions to resolve after conventiona l root-filling therapy.