Inactivation of root canal medicaments by dentine, hydroxylapatite and bovine serum albumin

Aim This study examined and compared the inhibition of the antibacterial ef fect of saturated calcium hydroxide solution, chlorhexidine acetate and iod ine potassium iodide by dentine, hydroxylapatite and bovine serum albumin. Methodology Enterococcus faecalis strain A197A prepared to a suspension of 3 x 10(8) cells per mi in 0.5% peptone water was used. Fifty muL of saturat ed calcium hydroxide solution, 0.05% chlorhexidine acetate or 0.2/0.4% iodi ne potassium iodide were incubated at 37 degreesC with 28 mg dentine powder (DP), hydroxylapatite (HA) or bovine serum albumin (BSA) in 50 muL water f or 1 h before adding 50 muL of the bacterial suspension. Samples for bacter ial culturing were taken from the suspension 1 and 24 h after adding the ba cteria. In further experiments, the amount of dentine was stepwise reduced from 28 mg 150 muL(-1) to 2.8 mg 150 muL(-1). Results Calcium hydroxide was totally inactivated by the presence of 28 mg of DP, HA or BSA. Chlorhexidine (0.05%) was strongly inhibited by BSA and s lowed down by dentine. However, HA had little or no inhibitory effect on ch lorhexidine. The antibacterial effect of 0.2/0.4% on iodine potassium iodid e on E. faecalis was totally inhibited by dentine (28 mg), but was practica lly unaffected by HA or BSA. A stepwise reduction of dentine from 28 mg 150 muL(-1) to 2.8 mg 150 muL(-1) was followed by a similar reduction of the i nhibition of the antibacterial activity of chlorhexidine. Iodine potassium iodide was not inhibited at all with dentine amounts less than 28 mg. Howev er, the effect of saturated calcium hydroxide solution was totally eliminat ed by dentine, in all four concentrations. Conclusion Inhibition by dentine of the antibacterial activity of calcium h ydroxide, chlorhexidine and iodine potassium iodide occurs by different mec hanisms. Different components of dentine may he responsible for the inhibit ion of these three medicaments. Calcium hydroxide was particularly sensitiv e to inhibition by both inorganic and organic compounds.