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Figure 24: Here I am using the 856-016 bur to do the occlusal
reduction on the bicuspid. I use the bigger 856-025 bur on molars,
but it is a little too big to use on bicuspids without accidentally
nicking the adjacent teeth. You could also use a football bur to
do this reduction (the convex shape of the bur will give you some
“bonus” reduction).
Figure 25: The 856-025 bur does a great job on the facial surface of
anterior teeth as well. You can see that I already finished the facial
reduction on tooth #10 as I reduce tooth #9 here. Notice how dark
the staining is on tooth #10 compared to tooth #8. Tooth #9 is right
in the middle in terms of shade because we have removed about
half of the enamel. You can already see that the margin looks good
on tooth #10 — that’s the beauty of the round bur.
Figure 26: I use the 379-023 football bur (Axis Dental) to reduce
the lingual surfaces of the anterior teeth. The convex shape of
the bur helps to prepare a concave shape that will allow room
for the incisal edges of the lower anteriors. Unlike other allceramic
materials that require at least 1 mm of reduction, we
can reduce just 0.6 mm on the lingual for a BruxZir crown.
I have a 0.6 mm depth cutter in my bur kit to measure this precisely.
Figure 27: Toward the end of the prep sequence, I like to start
rounding things over, especially the junctions of the facial surfaces
and the incisal edges. I also try to avoid leaving sharp corners on
the mesial and distal corners of the incisal edges. While BruxZir
crowns are strong enough to be placed on these sharp angles,
CAD/CAM mills are not able to replicate those sharp angles with
their round burs.
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