Biomedical Engineering Reference
In-Depth Information
FIGURE 15.19
Human tooth clamping device.
The clamping device is located onto the tooth to be machined and allows the tooth to be machined
by incorporating a wire-driven driving mechanism that attaches itself onto the clamp so that the
dental bur can rotate at the appropriate cutting speed.
Figure 15.20
shows the driving mechanism
attached to the clamping device and a tooth. The driving mechanism is attached to the air-operated
hand piece that provides the power to drive the mechanism, clamp, and dental bur.
Figure 15.21
shows the construction of the full assembly that allows machining of the tooth materials to take place.
The bur was rotated at 20,000-30,000 rpm, with a feed rate of between 0.2 and 0.5 mm rev
1
with-
out water-cooling. The uncoated and coated dental burs were compared with sintered diamond burs
machining acrylic teeth, and borosilicate glass was used to simulate the machining of porcelain teeth.
The flank wear of the dental burs was estimated from SEM.
15.4.5
Performance Testing
Figure 15.22
shows a SEM of a conventional polycrystalline diamond (PCD) sintered bur. The dia-
mond particles are imbedded to surface with a suitable binder matrix material, in this case nickel.
Typically the surface is inhomogeneous and sizes of particles range from 50 to 200 μm causing con-
siderable variation in the cutting performance of the tool.
An important factor that could affect the final performance of the dental bur is the adhesive tough-
ness of the diamond on the substrates. Endler et al.
[52]
and Polini et al.
[73]
have developed a new
method for the quantitative evaluation of the adhesive toughness of diamond films onto Co-cemented
