Denar Mark II - Immediate and Progressive Side Shift Adjustment; Defining Side Shift Components

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It should be noted that unlike most
semi-adjustable articulators the Denar
®
Mark II Semi-adjustable Articulator has
the capability of more accurately simu-
lating the mandibular side shift (Bennett
Shift) by more accurately simulating the
component condylar movements: the
immediate side shift and the progressive
shift. The immediate side shift is
expressed in units of tenths of a millime-
ter (fig. 29A). The progressive side shift
is expressed in degrees (fig. 29B).
The immediate side shift of the mandible
has primary influence on the width of
the central groove of posterior teeth.The
progressive side shift has its principal
influence on the balancing inclines of
posterior cusps on the orbiting side and
on the direction of the ridges and
grooves of posterior teeth, primarily on
the orbiting side.
Figure 30 illustrates the protrusive, orbit-
ing and rotating path records of the right
and left temporomandibular joints of 50
patients (100 TMJ records). 1 The X and
Y axes are calibrated in increments of 1
millimeter. You will note that the orbiting
path is divided essentially into two com-
ponents: immediate side shift and pro-
gressive side shift. Furthermore with few
exceptions once the immediate side
shift has occurred the progressive side
shift records are approximately parallel
to each other and are inclined approxi-
mately five to seven degrees to the
sagittal plane. The biggest variable is
the immediate side shift component of
the orbiting path.
Points A, B and C on one orbiting path
represent three different condylar posi-
tions at which lateral checkbite position-
al records may be taken on one patient.
It should be noted that if an articulator
possessing a progressive side shift and
not an immediate side shift adjustment
were set to each of the three condylar
positions A, B and C as shown in fig. 30.
It would produce three different progres-
sive side shift inclinations correspon-
ding to the three dotted lines in figure 30
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all of which inclinations would be
wrong. On the other hand, if an articula-
tor possessing a progressive as well as
an immediate side shift adjustment
IV. THE IMMEDIATE AND PROGRESSIVE SIDE
SHIFT ADJUSTMENT (Bennett Shift)
fig. 29
1. Lundeen, Harry C. and Wirth, Carl G.: Condylar Movement Patterns Engraved in Plastic Blocks,
J. Prothet. Dent. December 1973.
Pages 870-875.