Dentaltown January 2025 - 33

Understanding anterior
guidance and the rationale
to overbite selection
According to The Glossary of Prosthodontic
Terms, anterior guidance
is defined as " the fabrication of a
relationship of the anterior teeth
preventing posterior tooth contact in
all eccentric mandibular movements. "
Interferences are defined as " any tooth
contact that interferes with or hinders
harmonious mandibular movement;
an undesirable tooth contact. " If a
patient has occlusal interferences into
closure, meaning that the teeth are
not contacting simultaneously into
closure, then these contacts are also
interferences leaving closure. To further
explain this-anterior guidance is
immediate disclusion of the posterior
teeth in all excursions. If interferences
into closure are present, these teeth
will prevent the patient from having
anterior guidance. There will be simultaneous
anterior and posterior contacts
present in excursive movements.
When back teeth touch, the elevator
muscles contraction force increases. If
the anterior teeth only are in contact,
then the elevator muscle contraction
rate decreases.8
Developing anterior
guidance has also been termed a
" mutually protected occlusion. " This
means that the anterior and posterior
protect one another in function,
with the disclusion in all eccentric
movements on the anterior teeth only
to protect/prevent load increases on
posterior teeth in these movements.
Lateral contacts on posterior teeth
can be particularly damaging during
parafunction.9, 10, 11, 12
D'Amico was the first to publish
canine guidance as a rationale for
parafunctional protection in 1958.13
Stuart later further classified the benefit
to anterior guidance in eccentric
movements14
as a method to control/
mitigate parafunction. Anterior guidance
is a night guard or a protective
method that the patient cannot take
out of their mouth. It is built-in protection.
This is particularly important in
reconstruction on a patient because
studies and publications have shown
that there is poor compliance in
patients wearing nighttime appliances
(10)15
. Because of these factors, we
want our final rehabilitation design
to have an anterior guidance occlusal
scheme16,17,18,19
.
Overbite plays a role in anterior
guidance in that the steeper the bite,
the longer the anterior teeth remain
in contact during parafunction.
Likewise, the greater the possibility
of causing premature contacts on the
anterior teeth during function. These
premature contacts in the anterior
zone during function are called interferences
to the envelope of function. It
is thus wise to reduce the overbite to
prevent these issues from occurring.
(For more information on occlusion,
please visit dentaltown.com and CE
course " Understanding Occlusion. " )
STEP
4
Choose the new
CEJ-CEJ measurement
(new overbite)
In the previous steps, we
have established
that
we are going
Fig. 9
to lengthen this patient's
maxillary central to 10
mm. The new chosen
mandibular central
incisor length is 8 mm.
We can now determine
JANUARY 2025 | 33 | DENTALTOWN.COM
how much overbite we want in the
new designed occlusion. Although
we would not recommend a 0 mm
overbite, the purpose of this example
is to understand the applied measurements.
If we provided a 0 mm overbite,
the patient's new CEJ-CEJ position
would have to be 18 mm. The patient's
preoperative overbite was measured
to be 3 mm. If we applied this overbite
to the patient's new designed VDO, the
final CEJ-CEJ measurement would be
15 mm (Fig. 9).
The patients preoperative CEJ-CEJ
measurement was 11 mm. Since the
final desired vertical dimension is a
CEJ-CEJ measurement of 15 mm, we
need to increase the VDO by 4 mm to
achieve the desired final restorative
lengths of the teeth.
STEP
5
Taking the bite
To review, when designing
a new occlusion, we want
the final end result to provide
anterior guidance. In
order to establish anterior
guidance, we must have an
interference-free occlusion going into
closure. The bite record we want to
take to provide this occlusal scheme
is a centric relation bite record. The
traditional centric relation bite recording
is taken with the teeth just out of
occlusion.20
However, when restoring
at an increased vertical dimension we
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Dentaltown January 2025

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