In implantology, countersinking means:

# In implantology, "countersinking" refers to the process of:
A. Flaring or enlarging the coronal end of the osteotomy
B. Reversing the engine to remove the implant
C. Placing the implant in a counterclockwise rotation
D. Torquing the abutment to place

The correct answer is A. Flaring or enlarging the coronal end of the osteotomy.

As one of the final steps in the creation of the osteotomy to receive the implant body, a special bur is activated and inserted into the occlusal end of the osteotomy in order to increase the diameter of the opening slightly or to otherwise shape it. This step is referred to as "countersinking." Countersinking the implant osteotomy is called for by some manufacturers to compensate for very dense cortical bone or to prepare the bone for a particular implant shape (e.g., a flared implant shape at the coronal end).

Another of the final steps in the creation of the osteotomy is to place a threaded bur into the osteotomy so as to create a spiral groove on the wall of the osteotomy. This groove is placed so as to receive and guide the threads on the side of the implant during surgical placement and thus minimize the torque required and to minimize heat. This process of creating the groove on the inside of the osteotomy wall is referred to as "tapping" the osteotomy.

All of the burs used to create the osteotomy are used at relatively slow speeds (r.p.m.) to prevent injury to the bone, especially overheating of the bone. Also, water or saline irrigation is used to cool the burs and the bone during drilling.