In case of abutments and cavities preparation, as well as restoration materials finishing, the most utilized system in the dental office is based on rotating instruments use. There are, however, precise limits within which a rotating instrument cannot be used; functions may be limited or potentially dangerous due to limited control application. In all these cases it is appropriate to accompany the use of rotating instruments with complimentary oscillating systems that reduce the risk of potential iatrogenic  injury, improving significantly the quality of the surfaces being worked on.
The principle of action of oscillating files is based on the mechanical transformation of a rotating motion into a reciprocal stroke movement in the contra-angle.

Contra-Angle, Ref. WG-69 LT *
Ejector, Ref. 053
Spray canal cleaner needle, Ref. 054

* Contra-Angle without light:
Ref. WG-69 A