A new system for the removal of supragingival and subgingival plaque and calculus was studied. The system involves two motor driven handpieces. One handpiece works with curettes and hoes (Perioplaner) and the other works with diamond-layered instruments (Periopolisher). In the first part of this study the loss of root substance was measured as a consequence of treatment by these motor-driven instruments. These results were compared with those using classical hand curettes and rotating diamonds (Perio-Set). In the literature there is still debate over whether it is necessary to remove not only plaque and calculus but also cementum which may contain endotoxin or may even be infected. Whatever opinion one may have, it must be known how much root substance is lost by using a particular scaling instrument. This study has shown that the use of the Perioplaner and Periopolisher results in about the same loss of root substance as the use of hand instruments. In the second part of this study, first clinical experiences with these instruments are reported.