Radiographic Evaluation of the Effect of Endotoxin (LPS) Plus Calcium Hydroxide on Apical and Periapical Tissues of Dogs

Abstract

The aim of this study was the radiographic evaluation of the apical and periapical region of dog teeth submitted to intracanal bacterial endotoxin (lipopolysaccharide, LPS), associated or not with calcium hydroxide. After removal of the pulp, 60 premolars were divided into four groups and were filled with bacterial endotoxin (group 1), bacterial endotoxin plus calcium hydroxide (group 2), saline solution (group 3), or periapical lesions were induced with no treatment (group 4), for a period of 30 days. Similar periapical lesions were observed in groups 1 and 4. The lamina dura was intact in groups 2 and 3. Bacterial endotoxin (LPS) caused radiographically visible periapical lesions, but when associated with calcium hydroxide, this endotoxin was detoxified.A fundamental role in the cause and maintenance of periapical lesions has been attributed to the bacterial endotoxin, lipopolysaccharide (LPS) (1-3). When released during bacterial multiplication or death, this endotoxin, composed of lipopolysaccharides, causes a series of important biological effects, which lead to an inflammatory reaction (4) and periapical bone resorption (2).During the past 20 yr, a high prevalence of Gram-negative anaerobic microorganisms (5, 6) and the chemical structure of bacterial endotoxin commonly found in root canals with radiographically visible periapical lesions has been reported (7). The types of microorganisms and the level of intracanal endotoxin have also been correlated with specific clinical findings (1, 8). However, little research has evaluated the effect on periapical tissues of the inoculation of endotoxin into root canals (9 -12).The medical and dental literature have emphasized research attempting to obtain a medication that could inactivate bacterial endotoxin: examples are caustic soda (9), formocresol (13), 1.2% chlorhexidine (14), and sodium hypochlorite (15). Use of most of these products is limited due to their lack of efficiency or high toxicity, which causes undesirable effects when in contact with tissue.During in vitro research, Safavi and Nichols (16,17), Barthel et al. (3), and Olsen et al. (18) modified the concept of intracanal dressings, showing that calcium hydroxide hydrolyzes lipid A, which is the toxic part of endotoxin. Recently, we reported the histopathological finding of inactivation of the toxic effects of bacterial endotoxin by calcium hydroxide, in vivo (19). However, there are no in vivo radiographic reports of this inactivation. Thus, the purpose of this study was to evaluate radiographically the effect of endotoxin and endotoxin plus calcium hydroxide on the apical and periapical region in dogs. MATERIAL AND METHODSThe methods used for this radiographic study were similar to those used for the histopathologic evaluation of the effect of endotoxin plus calcium hydroxide (19). In a laminar air flow, 100 mg of Escherichia coli endotoxin (lipopolysaccharide B, E. coli 055:B5-Lipid A, 9.2%; Difco, Bacto, Detroit, MI) was suspended in 10 ml of phosphate buffered saline. Half of the 10-mg/ml su...

Diffusion ability of endotoxin through dentinal tubules

“…In this study, the endotoxin used was from Escherichia coli, since it is the standard endotoxin used in most of the studies 2,13,22 . Chemically, endotoxins are lipopolysaccharides that consist of three different parts: a non-polar lipid component, called lipid A, the core oligosaccharide and a heteropolysaccharide representing the surface antigen (O-antigen).…”

“…Some studies suggested that endotoxins are the main etiologic factor involved in the pathogenesis of the periapical inflammation, including bone resorption 17,26 . The effects of endotoxin on the periapical tissues of animals (monkeys, dogs and cats) are bone loss, and resorptive and inflammatory reactions in all experimental teeth 13,17,22 . Khabbaz et al…”

Role of endotoxin in the etiology of periapical lesions: molecular mechanisms involved in endotoxin's recognition and cell activation

“…This stimulates the synthesis and release of cytokines that activate osteoclasts, such as IL-1 and TNF, as previously described, and also stimulates the release of prostaglandin E2, which also has an influence on these cells 8,31 .…”

Uso de barreras apicales y apexificación en endodoncia

“…La mayoría de estas técnicas implican la eliminación del tejido necrótico seguido del desbridamiento del conducto y la colocación de un medicamento (30,31).…”

“…El mejor ejemplo en la demostración de su efecto es su acción sobre el lipopolisacárido (LPS) bacteriano. El Ca(OH) 2 altera químicamente al LPS, afectando sus diversas propiedades biológicas (30,31).…”