Which type of shank offers negligible tactile sensation?

The extra rigid shank provides negligible tactile sensation because it is designed to be very stiff and resistant to bending. This rigidity allows the instrument to apply greater force when scaling or performing other dental procedures but compromises the ability to feel subtle changes in tissue or surface texture. The lack of flexibility means that the clinician may not be able to detect a slight calculus deposit or variations in the surface of the tooth as effectively as with a more flexible shank.

In contrast, shanks that are moderately flexible, rugged, or flexible allow for some movement and bend under pressure, enhancing tactile sensitivity and providing feedback to the clinician. This tactile feedback is vital for accurately assessing the condition of the teeth and surrounding tissues, while extra rigid shanks prioritize strength over sensitivity.