Cristiane da Costa

Effect of Nitrogen Ion Implantation on the Flexibility of Rotary Nickel-Titanium Instruments

INTRODUCTION The aim of this study was to assess the effect of nitrogen ion implantation on the flexibility of rotary nickel-titanium (NiTi) instruments as measured by the load required to bend implanted and nonimplanted instruments at a 30° angle. METHODS Thirty K3 files, size #40, 0.02 taper and 25-mm length, were allocated into 2 groups as follows: group A, 15 files exposed to nitrogen ion implantation at a dose of 2.5 × 10(17) ions/cm(2), voltage 200 KeV, current density 1 μA/cm(2), temperature 130°C, and vacuum conditions of 10 × 10(-6) mm Hg for 6 hours; and group B, 15 nonimplanted files. One extra file was used for process control. All instruments were subjected to bend testing on a modified troptometer, with measurement of the load required for flexure to an angle of 30°. The Mann-Whitney U test was used for statistical analysis. Findings with P <.05 were considered significant. RESULTS The mean load required to bend instruments at a 30° angle was 376.26 g for implanted instruments and 383.78 g for nonimplanted instruments. The difference was not statistically significant. CONCLUSIONS Our findings show that nitrogen ion implantation has no appreciable effect on the flexibility of NiTi instruments.

Dental pulp vascular permeability changes induced by dental bleaching

Aiming to compare the effect of different light sou rces for dental bleaching on vascular permeability of dental pulps, forty-eight incisors were used. The bleaching agent (35 % hydrogen peroxide) was activated by halogen light; LED (Light Emitting Diode) or LED, followed by laser ph ototherapy (LPT) ( λ= 780 nm; 3 J/cm 2 ). After the bleaching procedures, the animals received an intra-arterial dye injection and one hour later were sacrificed. T he teeth were diaphanized and photographed. The amount of blue st ain content of each dental pulp was quantified usin g a computer imaging program. The data was statisticall y compared (p ≤ 0.05). The results showed a significant higher (p ≤ 0.01) dye content in the groups bleached with halo gen light, compared with the control, LED and LED p LPT groups. Thus, tooth bleaching activated by LED or LED plus LPT induces lesser resulted in increase d vascular permeability than halogen light.