Residual antibacterial activity of chlorhexidine digluconate and camphorated p-monochlorophenol in calcium hydroxide-based root canal dressings

Abstract

The purpose of this study was to evaluate the residual antibacterial activity of several calcium hydroxide [Ca(OH)2]-based pastes, placed in root canals of dogs' teeth with induced chronic periapical lesions. Root canals were instrumented with the ProFile rotary system and filled with 4 pastes: G1 (n=16): Ca(OH)2 paste + anesthetic solution; G2 (n=20): Calen® paste + camphorated p-monochlorophenol (CMCP); G3 (n=18): Calen®; and G4 (n=18): Ca(OH)2 paste + 2% chlorhexidine digluconate. After 21 days, the pastes were removed with size 60 K-files and placed on Petri plates with agar inoculated with Micrococcus luteus ATCC 9341. Pastes that were not placed into root canals served as control. After pre-diffusion, incubation and optimization, the inhibition zones of bacterial growth were measured and analyzed by Mann-Whitney U test at 5% significance level. All pastes showed residual antibacterial activity. The control samples had larger halos (p<0.05). The mean residual antibacterial activity halos in G1, G2, G3 and G4 were 7.6; 10.4; 17.7 and 21.4 mm, respectively. The zones of bacterial growth of G4 were significantly larger than those of G1 and G2 (p<0.05). In conclusion, regardless of the vehicle and antiseptic, all Ca(OH)2-based pastes showed different degrees of measurable residual antibacterial activity. Furthermore, unlike CMCP, chlorhexidine increased significantly the antibacterial activity of Ca(OH)2.

Translated abstract

Este estudo objetivou mensurar a atividade anti-bacteriana residual de várias pastas à base de hidróxido de cálcio [Ca(OH)2], após permanecerem em canais radiculares de cães com lesões periapicais crônicas induzidas. Os canais radiculares foram instrumentados com o sistema Profile e preenchidos com quatro diferentes pastas: G1-Ca(OH)2 p.a./solução anestésica (n=16), G2-Calen®/PMCC (n=20), G3-Calen® (n=18) e G4-Ca(OH)2 p.a./solução de digluconato de clorexidina a 2% (n=18). Transcorridos 21 dias, amostras foram recuperadas dos canais radiculares com limas Kerr #60 e colocadas em placas de Petri com ágar semeado com Micrococcus luteus ATCC 9341. Pastas não aplicadas nos canais radiculares serviram como controle. Após pré-difusão, incubação e otimização, as zonas de inibição do crescimento bacteriano foram mensuradas e analisadas pelo teste de Mann-Whitney (a<0.05). Verificou-se que todas as pastas apresentaram ação antibacteriana residual, com maiores halos para as amostras-controles. As médias dos halos de inibição para G1, G2, G3 e G4 foram 7,6; 10,4; 17,7 e 21,4 mm, respectivamente. Os halos de inibição de G4 foram significativamente superiores as de G1 e G2 (p<0.05). Portanto, independentemente do veículo, todas as pastas à base de Ca(OH)2 determinaram, em diferentes magnitudes, atividade anti-bacteriana residual mensurável. Ademais, diferentemente do PMCC, a solução de digluconato de clorexidina a 2% ampliou significativamente, a atividade anti-bacteriana residual do hidróxido de cálcio.