Thermal changes observed at implant sites during internal and external irrigation

In the preparation of osseointegrated dental implant sites, the use of bone drilling with conventional external irrigation has been shown to be thermally non-injurious to bovine bone, when employed as a model for dental implantology. The use of internal irrigation drilling systems is promoted on the basis of improved delivery of coolant to the bone/drill interface, which should subsequently improve local debridement and cooling, and therefore reduce thermal insults to the bone. The aim of this bovine model study was to compare the temperatures that were generated with external and internal irrigation systems during bone preparation for dental implants. A constant drill load of 1.7 kg was applied throughout the drilling procedures via a drilling rig. The burs that were used for both irrigation methods were a 2 mm twist drill for cutting the channel and a 3.25 mm drill for trephining this channel. The principal recorded parameter was the change in temperature generated via the drilling procedure. The 2 mm twist drills produced a maximum change in temperature of only 3.0 degrees C and 3.1 degrees C for the internal and external irrigation systems, respectively. Maximum changes for the 3.25 mm drills were 1.34 degrees C and 1.62 degrees C, respectively. Using the t-test, no statistical benefit was observed for one irrigant delivery system over the other. The clinical benefit of using the more expensive internal irrigation systems is therefore deemed unjustifiable, on the grounds that these systems do not appear to reduce the thermal challenge to the bone over and above that of simple flood irrigation.