They are passively manipulated to their most apical position. It must be emphasized repeatedly that judicious force control is required at all time with these instruments. Nickel-titanium instruments must be introduced into the canal with a pressure no greater than that which would break a sharp lead pencil and must never be left to linger in the canal for any period of time at a constant position. The protocol for using the Quantec variable tapers can be accomplished in many cases using only five instruments. In simpler cases fewer instruments may be used and in more complex cases more may be used.
Every case has to be evaluated individually.
The enlargement of the coronal and middle thirds of the root canal space in conjunction with the surveying phase of canal preparation creates a pathway to the apical constriction. As the larger tapers eliminate coronal obstructions, the succeeding smaller tapers used in sequence will automatically and passively drift closer towards the apical constriction. The constriction should never be altered intentionally either spatially or in size or shape. Shaping of the canal is merely a vehicle for sodium hypochlorite and EDTA solutions to penetrate to the full length of the canal where it will dissolve organic tissue and decrease the bacterial contaminants. The mechanical objectives of root canal preparation is illustrated where the canal is prepared as a gradually tapering funnel where the apical constriction is left unaltered in its original size and spatial position.