For the estimation of the errors in implant positioning due to the properties of the metal sleeve/osteotomy drill combination, four parameters are necessary: (1) sleeve length, (2) clearance (space between the bur and the sleeve), (3) implant length, and (4) offset (distance of the lip of the metal sleeve to the neck of the implant) (Figs. 1 and 2).

Definitions

1. Basic size: the nominal size of the metal sleeve and the osteotomy drill given by the manufacturer.
2. Sleeve length: the total length of the metal sleeve inserted into the surgical guide, including any lip protruding on the occlusal surface of the guide.
3. Offset: the distance between the neck of the implant and the occlusal surface of the lip of the metal sleeve.
4. Clearance: the difference between the inner diameter of the metal sleeve and the diameter of the osteotomy bur.
5. Implant length: the nominal length of the implant from the neck to the apex.
6. Total length: the sum of implant length and offset.
7. Error at the apex: the Euclidian distance between the apex of the implant at the planned position and the apex at the more extreme position permissible by the sleeve/drill combination (measured from the central implant axis).
8. Error at the neck: the Euclidian distance between the neck of the implant at the planned position and the neck of the implant at the more extreme position permissible by the sleeve/drill combination (measured from the central implant axis).
9. Deviation: the angle in degrees between the central axis of the implant on the planned position and the same axis on the most extreme permissible position.
10. Vertical error at the apex: the distance of the final position of the apex of the implant to the horizontal plane where the point of the planned position of the implant is included.