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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...

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This study evaluated in vitro the antibacterial activity of 4 root canal filling materials for primary teeth -zinc oxide and eugenol cement (ZOE), Calen paste thickened with zinc oxide (Calen/ZO), Sealapex sealer and EndoREZ sealer -against 5 bacterial strains commonly found in endodontic infections (Kocuria rhizophila, Enterococcus faecalis, Streptococcus mutans, Escherichia coli and Staphylococcus aureus) using the agar diffusion test (agar-well technique). Calen paste, 1% chlorhexidine digluconate (CHX) and distilled water served as controls. Seven wells per dish were made at equidistant points and immediately filled with the test and control materials. After incubation of the plates at 37 o C for 24 h, the diameter of the zones of bacterial growth inhibition produced around the wells was measured (in mm) with a digital caliper under reflected light. Data were analyzed statistically by analysis of variance and Tukey's post-hoc test (α=0.05). There were statistically significant differences (p<0.0001) among the zones of bacterial growth inhibition produced by the different materials against all target microorganisms. K. rhizophila was inhibited more effectively (p<0.05) by ZOE, while Calen/ZO had its highest antibacterial activity against E. faecalis (p<0.05). S. mutans was inhibited by Calen/ZO, Sealapex and ZOE in the same intensity (p>0.05). E. coli was inhibited more effectively (p<0.05) by ZOE, followed by Calen/ZO and Sealapex. Calen/ZO and ZOE were equally effective (p>0.05) against S. aureus, while Sealapex had the lowest antibacterial efficacy (p<0.05) against this microorganism. EndoREZ presented antibacterial activity only against K. rhizophila and S. aureus. The Calen paste and Calen/ZO produced larger zones of inhibition than 1% CHX when the marker microorganism was E faecalis. In conclusion, the in vitro antibacterial activity of the 4 root canal filling materials for primary teeth against bacterial strains commonly found in endodontic infections can be presented in a decreasing order of efficacy as follows: ZOE>Calen/ZO>Sealapex>EndoREZ.

Aiming to assess the presence of selected anaerobic microorganisms in root canals of human teeth with chronic apical periodontitis. 25 central and lateral upper incisors presenting with radiographic evidence of chronic apical periodontitis were studied. The pulp chamber was opened under aseptic conditions and samples of the root canal content were collected with sterile absorbent paper points, which were placed and dispersed in test tubes containing reduced transport medium RTT. Aliquots were dried on glass slides and stained by indirect immunofluorescence for detection of Actinomyces viscosus, Fusobacterium nucleatum, Porphyromonas gingivalis and Prevotella intermedia. The results showed a positive indirect immunofluorescence reaction in 24 of the 25 samples. Fourteen were positive for the specie Actinomyces viscosus, 12 for Prevotella intermedia, 10 for Fusobacterium nucleatum and 4 for Porphyromonas gingivalis. A semiquantitative assay was easily implemented for assessment of degree of infection by the organisms in individual cases.

The aim of this study was to evaluate, histopathologically, the effectiveness of mechanical preparation of root canals using different irrigating solutions in dog teeth filled with LPS after pulpectomy. A total of 120 root canals of 6 mongrel dogs were filled with a solution of LPS after pulpectomy. The irrigating solutions used were saline, 1, 2.5, and 5% sodium hypochlorite, and 2% chlorhexidine. No irrigation was used in the control group. The animals were sacrificed after 60 days and the teeth were fixed and demineralized. Subsequently, serial 6-µm sections were stained with hematoxylin and eosin and Mallory's trichrome for histopathological analysis and Brown-Brenn for verification of bacterial contamination. Analysis showed that the inflammatory infiltrate was statistically less intense in the groups in which the root canals were irrigated with 5% sodium hypochlorite and 2% chlorhexidine. However, none of the irrigating solutions completely inactivated the harmful effects of LPS. Mechanical preparation associated with different irrigating solutions did not completely inactivate LPS.

ABSTRACThis study evaluated the biocompatibility of mineral trioxide aggregate (MTA) after direct capping of exposed pulp tissue in dog's teeth. Class I cavities were prepared in 26 teeth from 3 adult dogs. MTA was applied over the exposed pulp in 13 teeth and paste of calcium hydroxide plus distilled water (control) was applied in the remaining 13 teeth. After 90 days, the animals were killed; the maxilla and mandible were dissected and sectioned to obtain individual roots. The samples were processed histologically. The pulp and periapical response observed with the use of MTA was similar to that of calcium hydroxide paste. In all specimens, there was a dentin bridge obliterating the exposure, an intact odontoblastic layer, no inflammatory cells, normal connective pulp tissue, normal apical and periapical regions and no bone tissue changes. Similar to calcium hydroxide, MTA presented excellent response when used for direct pulp capping. Uniterms: Dental pulp capping; Calcium hydroxide; Mineral trioxide aggregate. objetivo deste trabalho foi avaliar a biocompatibilidade do agregado de trióxido mineral (MTA), após proteção pulpar direta em dentes de cães. Foram preparadas cavidades de Classe I, em 26 dentes de 3 cães adultos. O MTA foi aplicado sobre 13 dentes e a pasta de hidróxido de cálcio (grupo controle) foi aplicada sobre os 13 dentes remanescentes. Após 90 dias, os animais foram mortos, a maxila e a mandíbula foram dissecadas e os dentes foram seccionados para obtenção de raízes individualizadas. Os espécimes foram processados histologicamente. A resposta do tecido pulpar e periapical foi semelhante para o MTA e o hidróxido de cálcio. Em todos os espécimes havia ponte de dentina obliterando o local da exposição pulpar, camada odontoblástica íntegra, ausência de células inflamatórias, tecido pulpar normal, e ausência de alterações na região periapical e óssea. Da mesma maneira que o hidróxido de cálcio, o MTA apresentou excelente biocompatibilidade quando usado para proteção pulpar direta. Unitermos: Capeamento da polpa dentária; Hidróxido de cálcio; Agregado de trióxido mineral.

New knowledge of the structure and biological activity of endotoxins (LPS) has revolutionized concepts concerning their mechanisms of action and forms of inactivation. Since the 1980's, technological advances in microbiological culture and identification have shown that anaerobic microorganisms, especially Gram-negative, predominate in root canals of teeth with pulp necrosis and radiographically visible chronic periapical lesions. Gram-negative bacteria not only have different factors of virulence and generate sub-products that are toxic to apical and periapical tissues, as also contain endotoxin (LPS) on their cell wall. This is especially important because endotoxin is released during multiplication or bacterial death, causing a series of biological effects that lead to an inflammatory reaction and resorption of mineralized tissues. Thus, due to the role of endotoxin in the pathogenesis of periapical lesions, we reviewed the literature concerning the biological activity of endotoxin and the relevance of its inactivation during treatment of teeth with pulp necrosis and chronic periapical lesion.