A guide drill is a round-shaped or pointed drill used to mark the site of an osteotomy by making an initial entry into cortical bone. An osteotomy is a procedure that involves the removal and/or reshaping of existing bone. Osteotomies can be performed at many locations throughout the body, but in dentistry, it is often used to correct bone issues in the mandible. An osteotomy can also be performed to correct the placement of an ill-fitting implant or prosthesis. Prior to the reshaping or removal of bone, a guide drill is used to create a small hole in the bone at the surgical site. This serves to identify the location of the procedure but also prevents the splitting of the bone due to a more aggressive drilling or cutting approach. Without the use of guide drills, bone cracking and splitting has been frequently reported resulting in damage to the bone that would have held the implant.