The anterior point of reference /certified fixed orthodontic courses by Indian dental academy

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 Two major objectives

1.restoration of the occlusion.
2.control of the form and position of the teeth.
Neglect in positioning the maxillary cast can result in:
1. additional and unnecessary record making.
2. un natural appearance in the final prosthesis.
3. damage to the supporting tissues.


Posterior points of reference
1) Bergstrom point—A point 10
mm anterior to the center of the
spherical insert for the external
auditory meatus & 7 mm below
the FH plane.Beck stated that it
lies close to hinge axis.

2)Beyron –A point 13 mm
anterior to the posterior margin
of the tragus of ear on a line

from the center of the tragus to
the outer canthus of the eye

 If the maxillary cast is positioned without the correct

maxillae-hinge axis relationship, deflective tooth
contacts occur.
 Deflective contacts contribute to

1. periodontal trauma.
2. muscle spasm.
3.TMJ pain
4. loss of supporting edentulous tissues.


 THE ANTERIOR POINT OF REFERENCE

Selection of the anterior point of reference determines
which plane in the head will become the plane of
reference when the prosthesis is being fabricated.
The act of affixing a maxillary cast to an articulator
relates the cast to the articulator’s hinge axis, to the
vertical axes, to the condylar determinants, to the
anterior guidance, and to the mean plane of
articulator.


 The selection of the (anterior) points of reference is
useful so that different maxillary casts of the same
patient can be positioned in the articulator in the
same relative position.
 When three points are used the position can be
repeated, and also reduce time with complicated time
consuming recording techniques such as
pantographic tracings to repeat the records each time
the technique calls for a new casts. For this reason it
is important to identify the mark permanently or be
able to repetitively measure a anterior
reference, point as well as the posterior points of
reference.

SELECTION OF ANTERIOR POINT OF REFERENCE
 Orbitale : In the skull

orbitale is the lowest point on
the infraorbital rim. On a
patient it can be palpated
through overlying skin. One
orbitale and the two
posterior points that
determine the horizontal axis
is defined as the axis - orbital
plane.
 This plane can be transferred
to articulator with the help
of an orbital pointer on the
face bow or by raising the
facebow itself to the level of
the orbitale.


 Advantage:

1. it is easy to locate and mark the orbitale.
2. the concept is easy to teach and understand.
 Disadvantage:

Relating the maxilla to the axis-orbitale plane will
slightly lower the maxillary cast anteriorly from
the position that would be established if the
Frankfort horizontal plane were used.


 Orbitale minus 7mm :

The Frankfort ' s horizontal
plane passes through the
poria and one orbitale
because these points are
(skull) bony landmarks.
Sicher recommends using
the mid point of the external
auditory meatus as the
posterior cranial landmark.
This land mark lies 7mm
superior to the axis and
recommends compensation
by making anterior point of
reference 7mm below the
orbitale or positioning the
orbitale pointer 7mm above
in the articulator to the
orbitale indicator.

 Nasion minus 23mm :

According to Sicher another
skull landmark the Nasion
can be used as the anterior
reference point. The nasion
guide or positioner which
relates to the deepest part of
the midline depression just
below the level of
eyebrows, as used in whipmix articulator the quick
mount face bow is designed
so that it moves in and out
but not up and down from
its attachments to the cross
bar.

 . The cross bar is located

approximately 23mm
below the nasion. When
the face bow is positioned
the cross bar will at the
level of the orbitale. The
disadvantages of using this
kind of face bow is that
this technique depends
upon the large nasion
guide, the morphologic
characteristics of the
nasion notch and the
variance of the nasionorbitale measurements
from 23mm in the patient.

 Incisal edge plus articulator midpoint to
articulator axishorizontal plane distance.

Guichet - Emphasized that a logical
position for the casts in the articulator would be
one which would position the plane of occlusion
near the mid horizontal plane of the articulator.
In accordance with this concept, the distance from
the mid horizontal plane to the articulator’s axishorizontal plane is measured. The same distance
is measured onto the patients from the existing
incisal edges or planned occlusal plane and then
transfer is done.

 Alae of the Nose : The

occlusal plane actually
parallels the horizontal
plane which was concluded
by Augsburger in review of
literature that the occlusal
plane parallels the
camper's line with minor
variations. Knowing this
we can transfer camper’s
plane from the patient to
the articulator by using
either right or left ala as
the anterior reference
point.

 Importance of selection of anterior reference point:

 A planned choice of anterior reference point will allow the

dentist and auxiliaries to visualize the anterior teeth and
occlusion in the articulator in the same frame of
reference that would in patient i.e. as if patient standing in
normal postural position with eyes looking straight ahead.
 Mounting the maxillary cast relative to the FHP will
accomplish this objective.


 The dentist may wish to initially establish the
restored occlusal plane parallel to the horizontal in

order to better control the occlusal plane in its
final position.
 The objective is to achieve a natural appearance in
the occlusal plane. Mounting the cast relative to
camper’s line best meet this objective.


 The dentist may wish to establish a baseline for

comparison between patients, or for the same
patient at different periods of time. This is possible
only through the use of a three-point mounting
that is constant from one patient to another or for
the same patient.


 If the camper’s line-

horizontal reference
plane is used, raise the
back of the articulator to
achieve the effect of the
Frankfort horizontal
plane mounting.


 If the Frankfort

horizontal plane
reference is used, raise
the anterior of the
articulator to achieve the
effect of paralleling the
occlusal plane and
Camper’s line with the
horizontal.


 The hinge line, the

interpupillary line, and a
transverse line across the
occlusal surfaces are
three common frontal
view reference lines.
 Hinge line being better
seen in the articulator.
The latter two are
observed in the patient.


SUMMARY:
Three points in space determine the position of the
maxillary cast in an articulator. The dentist most
frequently concerned with selecting the two posterior
reference points.
Improper selection of anterior reference point affect the
development of occlusion and esthetics.
Five commonly used anterior points of reference and the
reasons for the use of each have been discussed.


The anterior point of reference /certified fixed orthodontic courses by Indian dental academy

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