Page 67 - CEREC Q4|2012

quarter 2 | 2013 | cerecdoctors.com | 63
Brad Dorsch | Cincinnati
Kent nailed that one.
That's the exact reason.
Kevin Potts
Kent – Thanks for pointing those areas out. I just
recently tried to start experimenting with the
auto margin. But it doesn't seem anywhere near as good as
manual most of the time. I will switch back just to eliminate
that from being a potential problem.
Unfortunately, I have had this problem even when I used
manual mode. And in the case I showed here, the margin
was open, not just short.
Since I used to not have this problem with my lab-fabri-
cated e.max crowns. I can only assume that there is some-
thing that I am not doing good enough to keep a milled
crown happy. Please don't take this as my feelings of dismay
with CEREC. I just need to get much better, and FAST!
So, if anyone would like to chime in and give their two
cents, I am ready and happy to take any and all criticisms.
Honesty helps, even if someone feels that the prep is just no
good or needs significant refinement.
— Kevin "Thick-Skinned" Potts
Steve Nielsen | Shelley, Idaho
[In response to Brad Dorsch] Agree. Good job Kent.
Brent R. Browning | Houston
"Porsche" polish those axial walls and gingival
margins! Your lab routinely masks unforeseen
rough areas. CEREC acquisition sees it as it is!
Doug Sakurai | Santa Ana, Calif.
Are you moving the sprue location before you
mill?
Kevin Potts
I did move the sprue to the buccal or lingual on
that. I never leave those interproximal on e.max.
So, Porsche polish the prep. How does everyone like to
refine their margins here? I am trying to use a size 8 round
carbide at 10k rpm. Suggestions for otherwise? I used to
do everything with the coarse diamond including the
margins, back in the lab days, now I am trying more and
more ways to refine margins since I am seeing the crap
I am scanning.
Suggestions/help?
Douglas Lin | Hercules, Calif.
I see this quite often and it really has dampened
my enthusiasm for the one-visit crown. I have
yet to read anything that resolves the issue for me. These
are some of possible causes I have read:
1. Camera needs calibration. Tried this and didn't resolve
the problem.
2. Prepping above height of contour. Eliminated this and
didn't completely resolve the problem.
3. Margination. Tried over-extending the margin. Didn't
resolve it.
4. Glaze on the margin from not seating the crown
completely on the putty before baking. Checked this and
still have the same issues.
5. Binding. Checked this as well and didn't resolve it.
It doesn't happen every time, so it's very frustrating
because that makes it hard to diagnose. I have Bluecam and
MCXL. I would say this started happening a lot more since
I upgraded to MCXL and doing a lot more e.max.
Mike Skramstad (Faculty) | Edina, Minn.
Douglas – Try the 12 burs instead of the 12S and
see if you have better luck.
Kurt Kwiatkowski | Grafton, Wisc.
I had that problem when I first started doing
CEREC. I was prepping above the level of the
gingiva by 1-2mminareas on the facial and lingual. I found—
and granted, I've done about 100 CEREC crowns somy data
pool is small — that my margins looked like that because of
margination issues. For some reason, the Omnicam doesn't
seem to like to stay right on that 90-degree angle. Either it
marginates in giving you a ledge, or it swings down, giving
you jagged lines that look like little shark teeth.
Now I prep just above the gingiva, unless there is a huge
wall of enamel I want to save. If that's the case, then I will
marginate the best I can, and then bulk out the margins in
the parameters.