Evaluation of smear layer: a comparison of automated image analysis versus expert observers

Consistent and reproducible evaluation techniques of the smear layer in root canals in scanning electron microscopy studies are needed when comparing various instruments and techniques. In this study, the performance of 3 experienced blinded evaluators applying the Hulsmann technique was compared with a digital analysis method. Smear layer in the apical third of root canals of 35 freshly extracted teeth prepared by using nickel-titanium rotary instruments, Er:YAG and Er,Cr:YSGG lasers was scored on coded images. There was good agreement between the digital analysis method and the different evaluators (kappa analysis) across the range of the Hulsmann scores. Image analysis might be useful for evaluating the degree of smear layer removal in endodontic research.