The study aimed to evaluate intracanal irrigation procedures in eradicating bacteria from surface, shallow and deep layers of root dentine using extracted human teeth. Artificial bacterial smear layer was successfully produced by rubbing a mixture of dental plaque and artificially decalcified dentine or carious dentine on root canal walls. The reservoir holes were 3.5 mm in depth, 1 mm in diameter prepared 1.5 mm apart and parallel to the root canals on the decrowned planes, in which five separate bacterial species were placed (Actinomyces israelii, Fusobacterium nucleatum, Propionibacterium acnes, Streptococcus mutans and Streptococcus sanguis). Bacterial eradication after irrigation of the prepared canals was determined by bacterial recovery (i) from the root canal surfaces and shallow layers where bacteria were smeared artificially and (ii) from deeper layers of root canal dentine reservoir holes. Ultrasonic irrigation with 5.5% and 12% NaOCl eradicated bacteria from artificial smear layer (P < 0.0001), whilst 12% NaOCl irrigation with a syringe was insufficient. Ultrasonic irrigation with water or 15% EDTA-failed to eradicate bacteria from smeared surfaces. Ultrasonic irrigation with 12% NaOCl killed A. israelii, F. nucleatum, P. acnes, S. mutans, and S. sanguis placed in reservoir channels, although for F. nucleatum, a very small number of bacteria remained in five samples out of 12. Ultrasonic irrigation with less concentrated NaOCl failed to eliminate bacteria completely from reservoir channels in most samples. Ultrasonic irrigation with 12% NaOCl appeared to eliminate bacteria efficiently from surface, shallow and deep layers of root dentine.
We bonded a glass ionomer cement (GIC) containing various amounts of incorporated tannin-fluoride preparation (HY agent) to bovine dentin and investigated the effect of the ratio of incorporated preparations and the changes in bond strength over time. HY agent was incorporated into the powder at 0% (HY0), 1.5% (HY1.5), 5.0% (HY5), and 10.0% (HY10) by weight. The shear bond strength and percent of the cohesive failure were measured. Similar tests were performed on samples where diammine silver fluoride was applied to the dentin prior to placing the cement. It was found that the bond strength on the first day was increased by incorporating 1.5% of the HY agent in the GIC. The combined use of diammine silver fluoride increased the bond strength of the GIC.
We investigated the fluorine uptake in various layers of bovine dentin treated with glass ionomer cement (GIC) where a tannin-fluoride preparation (HY agent) was incorporated in the cement powder at ratios of 0 % (HY 0), 1.5% (HY 1.5), 5% (HY 5), and 10% (HY 10) by weight. The crystallinity of the dentin treated with the HY 0 and HY 10 cements was also investigated.The higher the ratio of incorporated HY agent, the deeper the penetration of fluorine in the dentin, and the greater the amount of fluorine taken up that bonded with the apatite.Compared with total fluorine uptake, more time is needed for fluorine to form a stable bond with apatite.It is also suggested that the crystallinity of dentin is enhanced when exposed to GIC containing the HY agent.
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