Surgical Preparation of the Bone - Drill Technique

Palatal Incision is very effective in the anterior maxilla and when there is concern that buccal dehiscence around the neck of the implant may result. Palatal Incision is very effective in the anterior maxilla and when there is concern that buccal dehiscence around the neck of the implant may result.It is essential not to allow the bone to be heated above 47°C during preparation of the site as this will cause bone cell death and prevent osseointegration. This problem may be avoided by:

•  Using sharp drills
•  Employing an incremental drilling procedure with increasing diameter drills
•  Avoidance of excessive speed (no more than 3,000 rpm) and pressure on the drills - ensuring that the drill is withdrawn from the site frequently to allow the bone 'swarf' to clear. This is particularly important in dense/hard bone.
• Using copious sterile saline irrigation. This can be delivered from a sterile infusion bag in a pressure cuff or a peristaltic pump. The drills can be adequately cooled by spraying the external surface of the drill. However, some systems use internally irrigated drills.

A typical sequence of drilling and implant insertion is shown in figure . Preparation of the sites commences with penetration of the outer cortex with a small round bur (Figure) followed by twist drills (Figure 15.5b to15.5e) of increasing sizesThe drills are marked to indicate the corresponding lengths of implants. The spacing and angulation of the implant sites are checked carefully with direction indicators throughout the drilling sequence, in relation to the stent and the opposing jaw/dentition.The angulations should be checked from different viewpoints (eg buccal and occlusal) as it is very easy to make errors when viewing from a single aspect.

Drilling sequence using initial drills at speeds of 2000 rpm.

a) Initial guided drill is used to start hole ("osteotomy")

b) 2 mm drill is drilled to the full depth of the site

c) Pilot drill is used to enlarge the site from 2 mm to 3 mm

d) 3 mm drill is used to complete the preparation to full depth

e) Final drilling at 2000 rpm; a counter-sink is used

f)The implant is inserted at 25 rpm

g) The final cover-screw is placed in position

The diameter of the last drill to be used is generally slightly smaller than that of the implant. This provides for good initial stability of the fixture (dental implant). In very dense bone it may be necessary to Tap ("thread") the bone to ensure ease of implant insertion.