Aim. To evaluate the antibacterial activity of four endodontic sealers on Enterococcus faecalis by a direct contact test. Material and Methods. Enterococcus faecalis was used as a test organism. Direct contact test which is based on measuring the effect of close contact between test bacteria and tested material on the kinetics of bacterial growth was performed to overcome the disadvantages of agar diffusion test. The sealers tested were zinc oxide eugenol-based sealer, glass-ionomer-based sealer, polydimethyl-siloxane-based sealer, and urethane dimethacrylate resin-based sealer. Data was collected by recording the optical density with the help of a spectrophotometer. Results. The sealers exhibited different inhibitory effects. The results obtained were subjected to statistical analysis by Kruskal Wallis analysis of variance and Dunn's multiple comparison test. Group comparison showed very highly significant difference between the groups. Conclusion. Zinc oxide eugenol-based sealer was the most effective and urethane dimethacrylate resin-based sealer was the least effective against Enterococcus faecalis, whereas glass-ionomer-based and polydimethyl-siloxane-based sealers were effective only for a short period. Inhibition of the bacterial growth is related to the direct contact of the microorganism with the sealer.

Olibanum and its resin and carbohydrate fractions were evaluated as rate controlling matrix materials in tablets for controlled release of diclofenac. Diclofenac matrix tablets were formulated employing olibanum and its resin and carbohydrate fractions in different concentrations and the tablets were evaluated for various tablet characters including drug release kinetics and mechanism. Olibanum and its resin component exhibited excellent retarding effect on drug release from the matrix tablets even at very low concentrations, 1 and 2% w/w in the formula. Diclofenac matrix tablets formulated employing olibanum and its resin component provided slow and controlled release of diclofenac over more than 24 h. Drug release from the matrix tablets was by Fickian diffusion and followed first order kinetics. Diclofenac release from some of the formulated tablets was comparable to that of Voveran SR tablets.

Olibanum resin was evaluated as microencapsulating agent and to prepare resin coated microcapsules. Olibanum resin coated microcapsules of indomethacin were prepared by an industrially feasible emulsification-solvent evaporation method and the microcapsules were investigated. The resin-coated microcapsules are spherical, discrete, free-flowing and multinucleate monolithic type. Microencapsulation efficiency was in the range 99-112 %. Indomethacin release from the resin-coated microcapsules was slow over 24 h and depended on core: coat ratio, wall thickness and size of the microcapsules. Drug release was by fickian diffusion mechanism. Good linear relationships were observed between wall thickness of microcapsules and release rate (K 1 ) and T 50 values. Resin coated microcapsules exhibited good controlled release characteristic and were found suitable for once a day oral controlled release products.

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