• Umaporn Vimonkittipong D.D.S.
• Sunphat Namano D.D.S., M.Sc., Diplomate, Thai Board of Prosthodontic Dentistry
• Sittichai Tudsri B.Sc., D.D.S., M.D., B.P.A., Diplomate, Thai Board of Oral and Maxillofacial Surgery

Objective To study the concentration of chromium and nickel residues in bone occurred after using
repeated implant drill set burs (The first, tenth and twentieth round of drilling)

Materials and methods This study used 11 bovine mandibles. Each mandible was cut into 21 bone
blocks with the size of 8 x 8 x 12 cubic millimeters. One bone block was randomly selected to be as
control. The other 20 bone blocks were also randomly selected in drilling process. One set of drill was
used for one mandible. Each set of drill consisted of: 2-millimeter tapered tip bur (Replace Select
Nobel Biocare), 3-millimeter tapered bur (Replace Select Nobel Biocare) and 3.7-millimeter reamer
bur (The implant research project). Drilling was performed on each bone block by using various
diameters of drill burs from small to large diameter. Drilling force, rotation speed, and depth of drilling
were controlled in drilling process. Chromium and nickel residues in bone were detected by graphite
furnace atomic absorption spectrometer in the controlled bone block, the first drilled bone block,
the tenth drilled bone block and the twentieth drilled bone block. Data were analyzed by Kruskal-
Wallis, with predetermined significant level of 0.05.

Results Residual chromium and nickel were found the most in bone when the drills were used in the
twentieth round and found the least when the drills were used in the first round. Residual chromium in
bone from the first round drills was significantly less than that of the tenth and the twentieth round
drills. However, residual nickel in bone was significantly different between the first round drills and
the twentieth round drills

Conclusion The study of chromium and nickel residues in bone found that using repeated drill set
bur following this research can cause chromium and nickel residues in bone. Residual chromium and
nickel were found the most when used in the twentieth round and were significantly greater than that
of the new ones.

(CU Dent J. 2011;34:99-108)