Nickel-titanium instruments cannot easily be precurved, and require straight line access to the root canal orifice. The use of ultrasonic tips to refine the access cavity has already been described. Nickel-titanium orifice shapers have replaced Gates-Glidden drills, and may be used sequentially from the largest to the smallest sizes. These remain centred in the canal and will flare the canal walls to approximately halfway down the canal. Their use may be restricted in narrow or curved canals. They are used with a very light apical pressure, often described as the pencil-lead pressure, ie that which would break the lead when using a propelling pencil. Each instrument should be used for no more than 5 10 seconds at a time before removing from the canal,
cleaning, irrigating and adding lubricant.
cleaning, irrigating and adding lubricant.