Therapy: crown preparation - the use of rotary, crown preparation instruments, in combination with sonically-vibrated tips of similar form, is the perfect protocol for successful crown preparations. Features: • Excellent overview during the preparation. • Direct view and control during use of magnifying spectacles and operating microscopes • Fast preparation and removal of old root fillings • Easier discovery of the canals • Extension of sclerosed canals • Preparation of a straight access to the canals without weakening of crowns • Removal of hard root filling materials, cements and pins • Avoids perforation and stepping • Spray cooling