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this triangle is determined by the Balk-
will Angle (the angle between the occlusal
planeandthearmoftheBonwillTriangle).
These average articulator values (arm,
base, Balkwill Angle, sagittal and Bennet
Angle) stay relatively consistent when
we have an established occlusal plane
and accurate tooth contacts (deter-
mined by buccal bite articulation).
Nowthat the theory of the virtual artic-
ulator has been established, let us look
at a clinical case. This patient needed a
full-coverage crown on tooth #14 and
a partial-coverage inlay/onlay on tooth
#15. In order for the virtual articulator to
perform adequately and ideally, we must
image properly. This includes recording
both the upper and lower arches at least
to the contralateral canine. If this is not
done, full guidance cannot be established.
In the cases in which canine guidance is
not present, one must consider recording
the full archof thecase toensureaccuracy
of the dynamic jawmovements.
After developing the 3-D model, the
occlusal plane and model orientation must
first be established (Fig. 6). Again, this
involves lining up the mandibular incisors
with the distal-buccal cusps of the first
molars. After drawing the margins and
verifying the insertion axis, we get initial
Biogeneric proposals. The proposals are
greatly improved, largely the result of the
new Model Axis step (Fig. 7). The static
occlusal contacts can now be checked and
adjusted as necessary (Fig. 8). In software
versions prior to V4.2, we had no dynamic
occlusion andwould havemilled the resto-
rations. However, with virtual articulation,
we can locate areas of dynamic interfer-
ence (Fig. 9) and adjust as necessary. To
activate the articulator function, you click
on “Articulation” in the Side Bar located on
the right. This will enable multiple func-
tions to analyze how the jaw movements
affect the designed restoration.
the occlusal plane. The traditional way of
constructing this plane is by using three
points on themandible (incisive points and
the two distal buccal cusps of the second
molars). CERECV4.2 has a newstep in the
Model Phasecalled theModelAxis (Fig. 4).
Thispositioningof themodelnotonlygives
us the ability to set the correct model axis,
but also teaches the software dental orien-
tations (buccal, lingual, mesial, distal).
This orientation and axis is critical in
determining the initial Biogeneric proposal
of the restoration. In the past, the insertion
axis was present for these functions. This
step is still present, but has less to do with
proposals andmore to dowithminimizing
potential undercuts and optimizing fit.
The last piece to the puzzle is how the
software estimates the position of the
condyles. This is done by the use of the
Bonwill Triangle. This equilateral triangle
relates the mandibular incisors to the
condylar centers (Fig. 5). The height of
Fig. 1: Average articulation values
Fig. 2: Bite record
Fig. 3: Contact points
Fig. 4: Model axis
Fig. 5: Bonwill triangle
Fig. 6: Model orientation
Fig. 7: Initial proposal
Fig. 8: Static occlusal contacts
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