Jaw relations in cd/ dental courses

JAW RELATION IN
COMPLETE
DENTURE
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

Introduction
Jaw relations are defined as any one of the
many relations of the mandible to the maxillae
Maxillomandibular relationship is defined as
any spatial relationship of the maxillae to the
mandible; any one of the infinite relationships of
the mandible to the maxilla.

TRIMMING THE UPPER RECORD BLOCK
When trimming the rim there are four main
considerations and they must be taken in the order given.
Labial fullness: The lip is normally supported by the
alveolar process and teeth which, at this stage, are
represented by the base and rim of the record block.
Therefore, the labial surface must be cut back or added to
until a natural and pleasing position of the upper lip is
obtained.

2. The height of occlusal rim: It should be trimmed vertically until
it represents the amount of anterior teeth intended to show below
the lip at rest. The average adult shows approximately 3mm of
upper central incisors when the lips are just parted, but there are
many variations from this amount which should be accepted as a
guide rather than a rule
A greater length of tooth than normal may be shown if the patient
has:
a. A short upper lip
b. Superior protrusion
c. An Angle’s Class II malocclusion of natural teeth
And less will be shown:
a. With a long upper lip
b. In most old people, owing to attrition of natural teeth and
some loss of tone of the orbicularis oris musclewww.indiandentalacademy.com

3. Anterior plane: Generally the plane to which the anterior
teeth should be set, and to which the rim must be trimmed, is
parallel to an imaginary line joining the pupils of the eyes or a
line at right angles to the midsagittal plane of the face.

4. The anteroposterior plane: This plane indicates the
position of occlusal surfaces of the posterior teeth and is
obtained in conjunction with the anterior plane. The rim is
trimmed parallel to Ala-tragus line (an imaginary line
running from the external auditary meatus or tragus of the
ear to the lower border of ala of the nose). It has been found
from the study of many cases that the occlusal plane of
natural teeth is usually parallel to this line
Thus when the rim has been trimmed to these planes
it indicates the place of orientation for setting the artificial
teeth.

GUIDELINES
1. The centre line or midline
In the normal natural dentition, the upper central
incisors have their mesial surfaces in contact with an
imaginary vertical line which bisects the face and, for
esthetic reasons, it is desirable that the artificial substitutes
should occupy the same position. Few human faces are
symmetrical. Therefore there can be no hard and fast rule
for determining the centre line, which thus depends on the
artistic judgement of the prosthodontist.

The following aids are suggested as a help in deciding
where to mark a vertical line on the labial surface of the
upper rim
• Where it is crossed by an imaginary line from the centre of
the brows to the centre of the chin.
• Immediately below the centre of the philtrum
• Immediately below the centre of the labial tubercle
• At the bisection of the line from one corner to the other
corner of the mouth, when the lips are relaxed.
• Where it is crossed by a line at right angles to the
interpupillary line from a point midway between the pupils
when the patient is looking directly forwards.
• Midway between the angles of the mouth when the patient
is smiling. www.indiandentalacademy.com

2. High lip line
This is a line just in contact with the lower border
of the upper lip when it is raised as high as possible
unaided, as in smiling or laughing. It is marked on the
labial surface of the rim and indicates the amount of
denture which may be seen under normal conditions, and
thus assists in determining the length of tooth needed.
3. Canine lines
These mark the corners of the mouth when the lips
are relaxed and are supposed to coincide with the tips of
the upper canine teeth but are only accurate to within 3 or
4 mm. These lines give some indication of the width to be
taken up by the six anterior teeth from tip to tip of the
canines.

TRIMMING THE LOWER RECORD BLOCK
Having trimmed and marked the upper block, all
that now requires to be done is to trim the lower block so
that when it occludes evenly with the upper, the mandible
will be separated from the maxilla by the same distance
that it was when the natural teeth were in occlusion. The
location of the occlusal plane posteriorly will ultimately be
determined by the height of the mandibular anterior teeth
and anterior 2/3 rd of retromolar pads. After recording
the tentative occlusal vertical relation and the centric
relation position, the maxillary occlusion rims are
oriented to the opening axis of the jaws with the help of
the face bow.

ORIENTATION RELATIONS
Orientation relations are those that orient the
mandible to the cranium in such a way that when the
mandible is kept in its most posterior unstrained position,
the mandible can rotate in the sagittal plane around an
imaginary transverse axis passing through or near the
condyles

THE FACE BOW
A caliper like instrument used to record the spatial
relationship of the maxillary arch to some anatomic
reference point or points and then transfer this relationship
to an articulator; it orients the dental cast in the same
relationship to the opening axis of the articulator.
Types of Face bow:
There are two types of face bows.
1. KINEMATIC face bow
2. ARBITRARY face bow -Facial type
-Earpiece type

KINEMATIC FACE BOW
The Kinematic face bow is initially used to accurately
locate the hinge axis. It is attached to a clutch, which in turn
attaches to the mandibular teeth. As the mandible makes
opening and closing movements the condylar styli move in an
arc. Their position is adjusted until they exhibit pure rotation
and not translation, when the mandible is opened and closed.
The points of rotation are marked on the skin and this
determines the true hinge axis. The mandibular clutch is
removed and the face bow is attached to the maxillary arch. The
true rotation points are again used to orient the tips of the
condylar styli . www.indiandentalacademy.com

ARBITRARY FACE BOW
The arbitrary type of face bow is so called because it uses
arbitrarily located marks on the skin at the condyle points as
the hinge axis position.
1. Facia type: In the facia type the condyle rods are positioned
on a line extending from the outer canthus of the eye to the
superior inferior center of the tragus and approximately
13mm anterior to the distal edge of the tragus of the ear.This
locates the condyle rods within 5mm. of the true center of the
opening axis of the jaws.www.indiandentalacademy.com

2. Ear piece type: the earpiece face bow is designed to fit
into the external auditory meatuses. Here also the fork is
attached to the maxillary occlusion rim. The whip mix,
Hanau earpiece and Denar slide matic face bow are
equipped with plastic earpieces at the condylar ends of the
bow. When an earpiece face bow is removed, it is attached
to the articulator by orienting “centering holes” in the
earpieces on the side of the condylar housings of the
articulator. With the denar slidematic face bow, the
anterior portion of the apparatus is removed from the bow
proper and supported in the articulator by a special jig,
which replaces the incisal guide table.

Indications for Face Bow Use
When the disharmonies in occlusion resulting from failure to use
the face bow are analyzed, it can be concluded that the face bow
should be used when.
1. Cusp form teeth are used
2. Balanced occlusion in the centric positions is desired
3 A definite cusp fossa or cusp tip to cusp incline relation is
desired.
4. When interocclusal check records are used for verification of jaw
positions.
5 When the occlusal vertical dimension is subject of change, and
alterations of tooth occlusal surfaces are necessary to accommodate
the change
6 To diagnose existing occlusion in-patient’s mouth.

VERTICAL JAW RELATIONS
Introduction:
A vertical jaw relation is defined as the distance between
two selected points, one on the maxillae and one on the
mandible. That is, they are established by the amount of
separation of the two jaws in a vertical direction under
specified conditions.
The physiologic rest position of the mandible as related
to the maxillae and the relations of the mandible to the
maxillae when the teeth are in occlusion are the two dimensions
of jaw separation of primary concern in complete denture
prosthesis prosthesis constructions.www.indiandentalacademy.com

CLASSIFICATIONS:
The methods for determining the vertical
maxillomandibular relations can be grouped roughly into
two categories.
1. The mechanical methods
2. The Physiologic methods
The use of esthetics as a guide combines both the
mechanical and physiologic approaches to the problem.

MECHANICAL METHOD:
1. Ridge relations
a) Distance of incisive papilla from mandibular incisors:
The incisive papilla is used to measure the patients’
vertical relation since it is a stable landmark and is changed
little by resorption of the residual alveolar ridge. The
distance of the incisive papilla from the incisal edge of the
mandibular incisors is about 4 mm. in the natural dentition.
The incisal edge of the maxillary central incisor is an
average of 6mm. below the incisive papilla. So the average
vertical overlap of the opposing central incisor is about 2
mm. the disadvantage of this method is the absence of lower
teeth and so is only useful in the treatment of single
dentures. www.indiandentalacademy.com

b) Parallelism of the ridges: Paralleling of the ridges, plus a
5 degree opening in the posterior region as suggested by
sears, often gives a clue to the correct amount of jaw
separation. This theory if used alone, is not reliable;
because many patients present such marked resorption that
the use of this rule would generally close the vertical
relation. But when considered with other observations, it
may be of value. However, in most patients the teeth are
lost at irregular intervals and the residual ridges are no
longer parallel

2. Measurement of former dentures
Measurements are made between the borders of the
maxillary and mandibular dentures by means of a boley
gauge and corresponding alterations can be made in the
new denture to compensate the occlusal wear.
3. Pre-extraction records
It is frequently possible to see the patient before he
or she becomes edentulous. In such cases one can usually
establish the occlusal position, record it in some manner
and transfer this record to the edentulous situation. This is
a relatively easy procedure and can be accomplished in
several ways www.indiandentalacademy.com

a) Profile radiograph: the exposure of a full lateral
radiograph is made with the teeth in occlusion, and after
extraction trial plates are made to an apparently correct
vertical relation. They are inserted, the patient closes on them
and another radiograph is taken. The two films are compared
and necessary adjustment is made to bring the mandible in
correct position as in the initial film. The image should have
approximately 1:1 ratio to the patient. Disadvantages include
inaccuracy due to enlargement of the image, it is time
consuming and it may result in too frequent exposure to
radiation.

b) Profile Photographs
Profile photographs are made and enlarged to life size.
The photographs should be made with the teeth in maximum
occlusion. Measurements of anatomic landmarks on the
photograph are compared with measurements of the face,
using the same landmarks. These measurements can be
compared when the records are made and again when the
artificial teeth are tried in. Disadvantage of this method is
that the angulation of the photograph might differ with the
patients posture.

c) Willis gauge.This instrument is used for recording vertical
height before extraction. The arm is placed in contact with the
base of the nose, and the arm is moved along the slide till it
lightly but firmly touches the lower border of the chin. It is
locked in position by the screw. The distance on the scale is
recorded on the patients’ chart. It is not an accurate method as
there may be verifications is applying pressure.
d)Articulated casts.These are of practical value in the
assessment of the vertical relation. Measurements can be made
of the casts in occlusion and relatively stable points.

4) POST EXTRACTION METHODS:
a) Niswonger’s methods suggested a method for
determining the vertical dimension that is commonly used
today. The patient is seated so that the Ala-Tragal line is
parallel with the floor. Two markings are made, one on the
upper lip below the nasal septum other in the most
prominent part of the chin. The patient is told to swallow
and relax. The distance between the marks is recorded.
Subsequently, the occlusion rims are constructed so that
when they occlude, the measured distance is 1/8 inch less
than the original measurement.

This 1/8-inch average freeway space falls within 2-4
mm. This method has the disadvantage that the marks move
with the skin and sometimes it is difficult to obtain two
constant measurements of the rest position. However, when
combined with other observations this technique is reasonably
reliable.
b) Willis method: Willis believed that the distance from the
pupils of the eye to the rima oris should be equal to the
distance from the base of the nose to the inferior border of the
chin, when the occlusion rims are in contact.
c) Concepts of equal thirds: Some observers suggested that
the face can be divided into equal thirds, the forehead, the nose
and lips and chin. This concept is of little practical value since
the points of measurements are vague.www.indiandentalacademy.com

d) Silverman’s closest speaking space measures the
vertical relation in phonetic method, must not be confused
with freeway space. The freeway space establishes vertical
relation when the muscles involved are at minimal tonic
contraction and the mandible is in its rest position. The closest
speaking space measures the vertical relation when the
mandible and the muscles involved are in physiologic function
of speech. The occlusion rims are placed in the mouth and the
height is adjusted until a minimum of space exists when the
patient pronounces the letter “S”. It may vary from 1 to 10
mm, but the 2mm average will generally prevent an increase in
vertical relation.

Electromyography Rest position of the mandible can be
determined by means of electromyography, which would
record the minimal activity of the muscles. All muscles show
greater activity in other positions than in rest position.
Electromyography is not a practical method of determining
vertical relations in the dental office because
The equipment is too expensive
The operator should have considerable knowledge and
experience in the field of muscle physiology before he can
attempt to interpret the tracings
Lastly, it is indicated that a five electrode reference
arrangement is needed in order to minimize the errorwww.indiandentalacademy.com

Physiologic methods:
1. Physiologic rest position Registration of the jaws in physiologic
rest position gives an indication to a relatively correct vertical
relation when used with other methods. After the insertion of the
occlusion rims into the patients’ mouth, the patient is asked to
swallow and let the jaws to relax. Then the lips are carefully parted
to see how much space is present between the occlusion rims. The
patients must allow the prosthodontist to separate the lips without
moving the jaws or lips.
This interocclusal rest space should be between 2-4 mm. when
viewed in the premolar region. The interarch space and rest
position can be measured by indelible dots or adhesive tapes on the
face. If the difference is greater than 4 mm. the occlusal vertical
relation would be considered too small. If the occlusal vertical
relation is less than 2 mm. the occlusal vertical relation would be
assumed to be great. www.indiandentalacademy.com

2) Phonetics speech is used as an aid in determining the
vertical relation. The patient is asked to repeat the letter ‘M’
until he is aware of the contacting of the lips. The patient is
asked to stop all jaw movements when the lips touch and the
distance between the two points of reference are measured.
The production of the h, s and j sounds bring the anterior
teeth very close together when correctly placed the lower
incisors are moved forward to a position nearly directly
under the upper central incisor and almost touching them.
If the distance is too large, a vertical relation of occlusion
that is too small may have been established. If the anterior
teeth touch when these sounds are made, the vertical relation
of occlusion is probably too great.

3). Facial expression the experienced prosthodontist learns
the advantage of recognizing the relaxed facial expression
when the jaws are at rest. In normally related jaws the lips
will be even anteroposteriorly and in slight contact. The lips
of a patient with a retruded mandible will not be even; the
lower lip will be distal to the upper and not in contact. In the
case of protruded mandible, the lips will not be evenly related
anteroposteriorly and the lower lip will be anterior to the
upper lip and not in contact. The skin around the eyes and
over the chin will be relaxed. Relaxation around the nares
reflects unobstructed breathing.

4) Swallowing threshold The position of the mandible at the
beginning of the swallowing act has been used as a guide to the
vertical relation. The theory behind the method is that when a
person swallows, the teeth come together with very light contact
at the beginning of the swallowing cycle. If denture occlusion is
continuously missing during swallowing the occlusal vertical
relation may be insufficient. The technique involves building a
cone of soft wax on the lower denture base so that it contacts the
upper occlusion rim with the jaws too wide open. The flow of
saliva is stimulated and the repeated action of swallowing will
gradually reduce the height of wax cone to allow the mandible to
reach the level of occlusal vertical relation. The length of time
this action is carried out and relative softness of the wax cone will
affect the results. It is difficult to find consistency in the final
vertical positioning of the mandible by this method.

5) Tactile sense The patient’s tactile sense is used as a
guide to the determination of the occlusal vertical relation.
The occlusion rims are inserted into the patients’ mouth
and he is instructed to open and close until the rims contact.
The patient is asked if the rims appear to touch too soon,
whether the jaws seem to close too far before they touch, or
if the height feels just right. This method is not very
effective with senile patients or those who have impaired
neuromuscular coordination’s.

Effects of Increased vertical Relation
1) Discomfort to the patient
2) Trauma: by the jamming effect of the teeth coming into
contact sooner than expected may cause not only discomfort
but also pain owing to the brusing of the mucous membrane by
these sudden and frequent blows.
3) Loss of freeway space: which may be lead to
a) Muscular fatigue of any one or group of muscles of
mastication
b) Trauma caused by the constant pressure on the mucous
membrane and
c) Annoyance from the inability to find a comfortable
resting position. www.indiandentalacademy.com

4) Clicking teeth: the tongue which has become accustomed
to the presence of teeth in certain fixed positions and during
speech helps to produce sounds without the teeth coming into
contact. When there is increase in vertical height opposing
cusps frequently meet each other, producing an embracing
clicking or clattering sound. This effect is also produced
during eating.
5) Appearance: the face has an elongated appearance since
at rest the lips are parted and closing them together will
produce an expression of strain
6) Bone residual alveolar ridge undergoes rapid resorption

Effects of decreased vertical relation
1) Inefficiency – which is due to the fact that the pressure
with which it is possible to exert with the teeth in contact
decreases considerably with over closure because the muscles
of mastication act from attachments, which have been
brought close together.
2) Cheek biting: In some cases where there is a loss of
muscular tone, as well as reduced vertical height, the flabby
cheek tends to become trapped between the teeth and bitten
during mastication.

3) Appearance: the general effect of over closure on facial
expression is of increased age. There is close approximation
of nose to chin, the soft tissues sag and fall in and the lines
on the face are deepened. The lips loose their fullness and
the vermilion borders are reduced to approximate a line.
4) Angular cheilitis: Reduced vertical relation results in a
crease at the corners of the mouth beyond the vermilion
border and the deep fold thus formed becomes bathed in
saliva, thus leading to infection and soreness.
5) Pain in the TMJ’s: Trauma in the region of the
temporomandibular fossa may be attributed to a reduced
vertical relation with symptoms like obscure pains,
discomfort, clicking sounds, headaches and neuralgia.www.indiandentalacademy.com

6) Costen’s syndrome: is stated to be the result of prolonged
over closure if it is suspected that these various pathologic
conditions are due to a reduced interarch distance, the
dentures should be considered as treatment dentures. The
vertical relation of occlusion should be built up gradually in
successive sets of dentures. Complete restoration of the
original occlusal vertical relation in one set of dentures would
likely result in a failure because patients will not be able to
accommodate themselves to this great changes in so short a
period of time.

HORIZONTAL JAW RELATIONS

Introduction
Horizontal jaw relations are those that are established
anteroposteriorly and mediolaterally, and so are classified as,
1.Centric relations
2.Eccentric relations: which include the
(a) Protrusive and
(b) Left and right lateral movements.

Centric relation
Centric relation is defined as a maxillomandibular
relationship in which the condyles articulate with the
thinnest avascular portion of their respective disks with
the complex in the anterior superior position against the
shapes of articular eminences. This position is
independent of tooth contact. This position is discernible
when mandible is directed superiorly and anteriorly and
restricted to a purely rotatary movement about a
transverse horizontal axis.

SIGNIFICANCE OF CENTRIC RELATION
1. This position is more definite than the vertical relation and is
independent of the presence or absence of teeth.
2. It is recordable and reproducible over a period of time
3. Centric relation serves as a reference relation for establishing
an occlusion
4. When centric relation and centric occlusion of natural teeth do
not coincide the periodontal structures around the natural teeth
are endangered.

5) When centric relation and centric occlusion of artificial
teeth do not coincide there is instability of dentures and the
patient will be subjected to pain and discomfort
6) Errors in mounting the casts on the articulator can be
detected, when the centric relation is used as the horizontal
reference position.
7) An accurate centric relation record properly orients the
lower cast to the opening axis of the articulator and the
mandible
8) Accurately recorded centric relation when transferred to
the articulator permits proper adjustments of the condylar
guidance for the control of eccentric movements of the
instrument. www.indiandentalacademy.com

The various methods used for recording centric relation may
be classified as
1.      Functional methods
a)     Needle – Hose method
b)     Patterson’s method
c)     Meyer’s method
2.      Excursive methods (graphic method)
a)     Intra oral tracing
b)     Extra oral tracing
3.    Tactile or interocclusal check records
4.     erminal hinge axis method

Functional methods:
1. Needles House method They used compound occlusion rims
with four metal styli placed in the maxillary rim. When the
mandible moves with the styli contacting the mandibular rim,
they cut four diamond shaped tracings.  The tracings incorporate
the movements in 3 planes and records are placed on a suitable
articulator to receive and duplicate the record.
2. Pattersons method This method uses wax occlusion rims.  A
trench is made in the mandibular rim and a mixture of half
plaster and half carborundum paste is placed in the trench.  The
mandibular movements generate compensating curves in the
plaster and carborundum. When the paste is reduced to the
predetermined vertical height of occlusion, the patient is
instructed to retrude the mandible and the occlusion rims are
joined together with metal staples

3. Meyers used soft wax on the occlusion rims to establish a
generated path. Tinfoil was placed over the wax and
lubricated. The patient performed the functional movement
to produce a wax path. A plaster index was made of the wax
path and the teeth were set to the plaster index.

Excursive methods
The most common form of excursive recordings is the
Gothic arch tracing. This may be employed intra orally or
extraorally.

Intra oral tracers:
The Intraoral arrow point tracer
combines a central bearing and tracing device.  It has pointed
screw in bearing and a tracing device mounted on the
maxillary rim and a plate mounted on the mandibular rim.
The plate is covered with a marking substance.  The central
bearing pin is connected to the proper vertical relation and
when the rims are in place, the patient is instructed to
perform lateral and protrusive movements. As these
movements are performed, the Gothic arch form is traced on
the plate.

Extra Oral tracing :
The extraoral tracer is always combined with
an intra oral bearing device to ensure equalization of
pressure on the bases. A needlepoint tracing made on a
tracing table coated with carbon or wax is used to indicate
the relative position of the upper and lower jaws in the
horizontal plane. These tracings are shaped like a Gothic
arch and so are sometimes referred to as Gothic arch
tracings. They are also known as arrow point tracing.

Conclusion
All the above factors should be essentially considered
by the prosthodontist during Jaw relation procedures to
relate its useful clinical application in the healthy service of
the edentulous patients.
Since there is no precise scientific method of
determining the correct vertical relations, the registration of
vertical relation depends upon the clinical experience and
judgment of the prosthodontist – an art rather than a science.
It is obvious that the skill of the prosthodontist and
the cooperation of the patient are probably the most
important factors in securing an accurate centric relation
records. www.indiandentalacademy.com

Jaw relations in cd/ dental courses

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