Search

The difficulty of eliminating Enterococcus faecalis and other bacteria infecting dental root canals makes it desirable to develop formulations capable of sustained release of antibiotics within the canal. With this function in view, in this work we compared the mechanical, drug release and biocompatibility properties of amoxicillin-loaded collagen (CL) and CL complexed with poly[(methyl vinyl ether)-co-(maleic anhydride)] (PVMMA), with or without glutaraldehyde (GTA) or the natural product genipin (GN) as cross-linker. Collagen was not denatured by complexation with PVMMA. Only CL-PVMMA-GN sponges did not disintegrate during 7 days exposure to cell culture medium (un-cross-linked CL disintegrated within 24 h and un-cross-linked CL-PVMMA within 4 days), and CL-PVMMA-GN sponges also exhibited the most appropriate combination of mechanical properties (hardness, modulus of deformability and plasticity). CL-PVMMA-GN sponges absorbed aqueous medium faster than other cross-linked formulations, but their maximum uptake was less; and drug release from CL-PVMMA-GN sponges tended to be faster than from any other, except un-cross-linked CL-PVMMA, maximum release taking about 4 days. No formulation significantly altered the viability of L929 fibroblast-like mouse connective tissue cells, but cells growing on sponges showed signs of non-adherence. It is concluded that genipin-cross-linked CL-PVMMA sponges merit further investigation as antibiotics vehicles and aids to tissue regeneration in the dental root canal. [ABSTRACT FROM AUTHOR]

Aim To evaluate the corrosion resistance of nickel–titanium (NiTi) endodontic rotary instruments immersed in 5.25% sodium hypochlorite (NaOCl) solution. Methodology The corrosion performance of NiTi instruments (S1 25 mm, ProTaper Dentsplay Maillefer, Ballaigues, Switzerland) was evaluated using commercial 5.25% NaOCl solution (pH = 12.3), and the same solution partially neutralized adding H2SO4 to reach pH = 10.1. Electrochemical measurements were carried out using a potentiostat equipped with a five-channel zero resistance ammeter (ZRA) for galvanic current measurements. The instruments were sectioned into three parts (cutting part, noncutting part and shank) and degreased with acetone and rinsing with demineralized water prior to being immersed in NaOCl solution for testing. Each set of the three parts constituted one ‘virtual’ instrument through the ZRA, giving access to the galvanic currents that circulate between the three parts. Nine instruments were employed to check the reproducibility of the electrochemical measurements. Results The corrosion potential (Ecorr) of the NiTi alloy reached the passive domain in approximately 20 s of immersion in the solution having a pH 10.1. After this initial period the potential remained steady, indicating that stable passivation was achieved. However, at pH 12.3 no stationary state was achieved even after 6000 s of immersion time. Thus, the alloy was not stable in this medium from a corrosion point of view. Conclusions The corrosion resistance of NiTi alloy was enhanced by lowering the pH of NaOCl solution to 10.1, which allows the system to reach the stability domain of the passivating species TiO2 and NiO2. [ABSTRACT FROM AUTHOR]