It's a study about the principal clearing techniques, with a selection of materials and phases of execution. The purpose was to obtain transparency of mineralized structure together with preservation of pulpal contents. From this research a technique has been extracted and positively tested, with great results: a) tridimensional control of alterations pointed out in anatomy after canal preparation; b) measurement of pulpal debris size after instrumentation; c) identification of instruments dark zone; d) measurement of the empty-cleansing capacity of root canal system and the defence from eventual self-made errors, as a result of particular operating techniques, whose comparison is accessible by methodology.