Discussion.
The migration of inflammatory cells into the peritoneal cavity of mice has been used to evaluate inflammatory response caused by endodontic materials (Silva et al. 1997) and calcium hydroxide dressings (Nelson Filho et al.1999). In this study, the solutions did not cause a significant increase in neutrophils or mononuclear cells in the peritoneal cavity at 4 and 24 h (P > 0.05). However, at 48-168 h, the 0.5% sodium hypochlorite solution caused a greater increase in the number of neutrophils in the peritoneal cavity (P < 0.05). This response is probably due to tissue irritation caused by the capacity of sodium hypochlorite to dissolve organic tissue (Grossman & Meiman 1941, Gordon et al. 1981), and is increased at higher concentrations. Yesilsoy et al. (1995) and Spangberg (1973) reported the irritating effect of sodium hypochlorite, particularly at high concentrations. Leonardo et al. (1984) observed periapical and apical tissue irritation after biomechanical preparation of dog’s teeth using 4% sodium hypochlorite solution.
Two percent chlorhexidine solution has a wide spectrum of antibacterial effect as well as prolonged residual effect (Jeansonne & White 1994,White et al. 1997, Leonardo et al.1999), suggesting its use as an irrigating solution in infected root canals. This solution has also shown to be non-irritating to tissue. The use of 2% chlorhexidine as a periodontal irrigant did not cause obvious toxic effect son gingival tissue (Loe&Schiott1970, Southard et al.1989).
At all experimental periods, chlorhexidine was statistically similar to the control group (P > 0.05). The absence of oedema observed by protein leakage suggested no significant tissue damage, indicating biocompatibility of chlorhexidine (Yesilsoy et al.1995).
Jimenes-Rubio et al. (1997) reported that5.25%sodium hypochlorite and 1% glutaraldehyde significantly decreased macrophage adhesion capacity, an important factor during inflammation. Segura et al. (1999) observed that0.12%chlorhexidine solution inhibited macrophage adherence, however, at lower intensity than 5.25% sodium hypochlorite.
Although chlorhexidine had better biological results compared to sodium hypochlorite, it does not dissolve tissue or inactivate bacterial LPS. Therefore its use has been recommended as an alternative to sodium hypochlorite in patients who are allergic to hypochlorite or in teeth with incomplete roots (Jeansonne & White 1994). Fuss & Trope (1996) have recommended its use in crestal perforations because a biocompatible medicament is essential to prevent inflammatory response in proximity to the epithelial attachment. It can also be used for final irrigation due to its broad spectrum of antimicrobial activity (Delany et al. 1982, Ohara et al. 1993, Jeansonne &White1994).

References.

Ayhan H, Sultan N, Cirak M, Ruhi MZ, Bodur H (1999) Antimicrobial   effects of various endodontic irrigants on selected microorganisms. International   Endodontic Journal 32, 99-102.
Bystrom A, Sundqvist G (1983) Bacteriologic evaluation of the 0.5% sodium   hypochlorite in endodontic therapy. Oral Surgery OralMedicine Oral Pathology   55, 307-12 .
Delany GM, Patterson SS, Miller MS, Newton CW (1982) The effect of chlorhexidine   gluconate irrigation on the root canal flora of freshly extracted necrotic teeth.   Oral Surgery Oral Medicine Oral Pathology 53, 518-23.
Faccioli LH, Souza GEP, Cunha FQ, Poole S, Ferreira SH (1990) Recombinant   interleukin-1and tumor necrosis factor induce neutrophil migration in vivo by   indirect mechanisms. Agents and Actions 30, 344-9.
Fuss Z, Trope M (1996) Root perforations: classification and treatment choices   based on prognostic factors. Endodontics and Dental Traumatology 12, 255-64.
Gordon TM, Damato D, Christner P (1981) Solvent effect of various dilutions   of sodium hypochlorite on vital and necrotic tissue. Journal of Endodontics   7, 466-9.
Grossman LT, Meiman BW (1941) Solution of pulp tissue by chemical agents.   Journal of the American Dental Association 28, 2 23-5.
Jeansonne MJ, White RR (1994) A comparison of 2.0% chlorhexidine gluconate   and 5.25% sodium hypochlorite as antimicrobial endodontic irrigants. Journal   of Endodontics 20, 276-8.
Jimenes-Rubio A, Segura JJ, Llamas R, Jimenes-Planas A, Gerrero JM, Calvo JR   (1997) In vitro study of the effect of sodium hypochlorite and glutaraldehyde   on substrate adherence capacity of macrophages. Journal of Endodontics 23,   562-4.
Komorowski R, Grad H, Wu XY, Friedman S (2000) Antimicrobial substantivity   of chlorhexidine-treated bovine root dentin. Journal of Endodontics 26,   315-7.
Leonardo MR (1998) Preparo biomecanico dos canais radiculares. Definicao,   conceito, finalidades, importancia, recursos para sua aplicacao e meios quimicos   (solucao irrigadora). In: Leonardo MR, Leal JM, eds. Endodontia Tratamento   de Canais Radiculares, 3rd edn. Sao Paulo: Medica Panamericana, pp. 333-58.
Leonardo MR, Almeida WA, Ito IY, Silva LAB (1994) Radiographic andmicrobiologic   evaluationof posttreatment apical and periapical repair of root canals of dog's   teethwith experimentally induced chronic lesion. Oral Surgery Oral Medicine   Oral Pathology 78, 2 32-8.
Leonardo MR, Almeida WA, Silva LAB, Utrilla LS (1995) Histopathological observations   of periapical repair in teeth with radiolucent areas submitted to two different   methods of root canal treatment. Journal of Endodontics 21, 137-41.
Leonardo MR, Lia RCC, Esberard RM, Benatti Neto C (1984) Immediate root canal   filling: the use of cytophylactic substances and noncytotoxic solutions.   Journal of Endodontics 10, 1-8.
Leonardo MR, Tanomaru Filho M, Silva LAB, Nelson Filho N, Bonifacio KC, Ito   IY (1999) In vivo antimicrobial activity of 2% chlorhexidine used as a root   canal irrigating solution. Journal of Endodontics 25, 167-71.
Loe H, Schiott CR (1970) The effect of mouth rinses and topical application   of chlorhexidine on the development of dental plaque and gingivites in man.   Journal of Periodontology Research 5, 79-83.
Nelson Filho P, Silva LAB, Leonardo MR, Utrilla LS, Figueiredo F (1999) Connective   tissue responses to calcium hydroxide based root canal medicaments. International   Endodontic Journal 32,303-11.
Ohara P,Torabinejad M, Kettering JD (1993) Antibacterial effects of various   endodontic irrigants on selected anaerobic bacteria. Endodontics and Dental   Traumatology 9, 95-100.
Segura JJ, Rubio AJ, Gerrero JM, Calvo JR (1999) Comparative effects of two   endodontic irrigants, chlorhexidine digluconate and sodium hypochlorite, on   macrophage adhesion to plastic surfaces. Journal of Endodontics 25, 2 43-6.
Silva LAB, Leonardo MR, Faccioli LH, Figueiredo F (1997) Inflammatory response   to calcium hydroxide based root canal sealers. Journal of Endodontics 23,86-90.
Sjogren U, Figdor D, Persson S, Sundqvist G (1997) Influence of infectionat   the time of root filling on the outcome of endodontic treatment of teeth with   apical periodontitis. International Endodontic Journal 30, 2 97-306.
Southard SR, Drisko CL, Killoy WJ, Cobb CM, Tira DE (1989) The effect of   2% chlorhexidine digluconate irrigation on clinical parameters and the level   of Bacteroides gingivalis in periodontal pockets. Journal of Periodontology   60, 302-9.
Spangberg L (1973) Biologic effects of dental materials. Part III. Toxicity   and antimicrobial effect of endodontic antisseptics in vitro. Oral Surgery   Oral Medicine Oral Pathology 36, 856-71.
White RR, Hays GL, Janer LR (1997) Residual antimicrobial activity after   canal irrigation with chlorhexidine. Journal of Endodontics 23, 2 29-31.
Yesilsoy C, Whitaker E, Cleveland D, Phillips E, Trope M (1995) Antimicrobial   and toxic effects of established and potential root canal irrigants. Journal   of Endodontics 21, 513-5.