The effect of instrumentation with two different file types, each with 2.5% NaOCl irrigation on the microhardness of root dentin.

The aim of this study was to measure root-dentin microhardness after instrumentation with two types of files and using irrigation with 2.5% sodium hypochlorite. Thirty roots were instrumented with irrigation: 10 roots had the pulp extirpated only; 10 roots were instrumented with stainless steel files, and 10 roots were instrumented with rotary nickel-titanium (NiTi) files. Additionally, five roots were extirpated only without irrigation and served as a control. The roots were sliced and root-dentin microhardness was determined at depths of 500 microm and 1000 microm from the pulp-dentin interface. Significant differences were found between the microhardness at 500 microm and 1000 microm (p < 0.001) in all groups. Instrumentation with NiTi rotary files affected dentin microhardness significantly to a lesser extent.