Verticle jaw rel challenge to dentist/dental courses

Verticle jaw rel challenge
to dentist
www.indiandentalacademy.com
INDIAN DENTAL ACADEMY
LEADER IN CONTINUING Education

• It is common to hear
a wide variety of opinion
as to where vertical dimension
should be…
and
how to determine this position???

• A crucial and debated aspect of CD
construction is the determination of
maxillo-mandibular relations especially
VDO.
Reasons…..

Variety of methods available.
Methods are subjective rather than
objective.
None is documented to be ideal and
perfect.
Lacunae in every method.
No objective method is universally
accepted

• VARIOUS METHODS:
• Mechanical
Pre- extraction records
• Profile radiographs
• Casts of teeth in occlusion
• Facial measurements

Ridge relation
• Distance from the incisive papilla
• Parallelism of ridges

• Physiological:
Physiological rest position
Swallowing phenomenon
Phonetics
Closing forces
Tactile sense
Patient reported sense of comfort

• Wright recommended the use of pre-
extraction records/old photographs of
patients in determining and
establishing VDO .

• Boos determined VDO by measuring
maximum biting force

Shpuntoff demonstrated that the
muscles controlling the mandible
become tense when any type of
mechanical recording device is
placed in mouth. Registration of
mandibular position made under
such circumstances would reflect
the strain induced.

• Silverman used closest speaking space
to determine VDO.

• Swerdlow believed that phonetic
methods were consistently more
reliable than the swallowing technique
for determination of interocclusal
distance.

• Shanahan used “ physiological
method” of swallowing for
determining VDO and centric
relation.

• Physiologic rest position- main
starting point used to measure VDO
• VDR = VDO + IOG

• But the concept is unreliable for 2
reasons:
1.The rest position is not constant and
continuously changes, and so it is not a logical
baseline from which to measure the fixed
dimension at maximum intercuspation.
2.The interocclusal freeway space is highly
variable from one patient to another, and so
there are no set dimensional relationships that
could be used to find VDO even if the rest
position could be determined with consistent
accuracy. www.indiandentalacademy.com

• CONTROVERSY???

• CONCEPT OF CONSTANCY OF
REST POSITION:
Gillis (1941)
“mandibular rest position is not
artificially established. The
interocclusal clearance averages
about 3mm as measured at central
incisors and doesn't vary greatly
between different individuals”
He defined rest position from which
all mandibular movements begin
and to which they returnwww.indiandentalacademy.com

Niswonger postulated that rest
position remains constant throughout
life.
Thompson (1954):
“He stated “ the rest vertical dimension
established by mandible in its rest
position is greater than VDO and is
constant in most instances regardless
of the status of dentition” .

CONCEPT OF VARIABILITY OF REST
POSITION

Loeff (1950):
• Stressed that muscle tone rather than
muscle length controls rest position
and muscle tone can and does vary e.g
muscle tone can be increased by
exercise and decreased by rest.

Atwood (1950):
• Performed a longitudinal radiographic
analysis of face height before and after
extraction in 42 subjects. He demonstrated
variability within a sitting, between
different sittings and readings with and
without dentures.
• When opposing occlusal contacts were
removed there was a decrease in VDR. The
degree of variability depended on relative
values of and complete interplay of 30
influential factors

Duncan and Williams (1959):
• Used lateral cephalometric
measurement to study rest position
as a guide in prosthetic treatment. A
general decrease in height of face
with mandible in rest position was
observed on removal of occlusal
contacts.
• They concluded that rest position is a
poor guide for establishing the
vertical dimension of occlusion.

Perry (1956), Garvick (1962):
• Studied EMG activity of facial muscle
and also formed the concept of
postural range.
• Clinically recorded rest position is
usually 2-3 mm below intercuspal
position, doesn't correspond to that
recorded in EMG activity.
• EMG rest position is several
millimeters lower than in the clinical
rest position.

• Moreover certain measurements of
vertical dimension and EMG study have
shown that many slow changes in
vertical dimension can occur without
change in electrical activities of the
muscle involved.
• Thus, these research works favor the
concept of postural rest position as a
range of positions rather than a single
and absolute one.

• Shephard and Shephard reported that
the rest position of edentulous
mandible tended to vary even over a
short span of time following
cephalometric examination.
• Garnick and Ramrjord demonstrated
a variation of 1.5mm in rest position
in 13 of 20 subjects from start to
finish of their experimental period(45
mints).

Thompson and Kendrick:
demonstrated a significant change in
both vertical dimensions within 1
year in all of their 71 participants.

• Balance of forces:
• At any given point of time a balance
between active and passive forces
determine rest position of mandible.

• Passive forces:
Elasticity of muscle fibers and
connective tissue elements
Emotions
Posture
Gravity
Elastic property of capsule and
ligament of TMJ

• Active forces:
 Continuous low grade motor activity in muscles.
Elevators show more such activity due to activation
of stretch reflex and increased motor unit activity of
mandible increases due to insertion of lower denture
when mandible tends to drop and elevator muscles
are stretched.
 Changes in head and neck position
 External factors (emotions, drugs)
 VDR decrease by - adrenaline, caffeine
 VDR increase by - barbiturates and during sleep

• This raises question against reliability
of rest position in establishing VDO.
• Still it is universally believed that
when used properly mandibular rest
position may help establish a
satisfactory esthetic and functional
VDO especially in edentulous patients.

• CONCLUSION:
• There is no universally accepted
method of determining VDO.
• There seem to be no significant
advantages of one technique but it is
the end result that matters.
• It should be satisfactory to the dentist
and patient from esthetic point of view
and not induce degenerative changes
from a functional standpoint.

• Finding a reliable method to
determine appropriate jaw relations
has always been a goal of researchers
in the field of CD Prosthodontics.
• However, there has been a decline in
scientific work in this aspect of
prosthetic dentistry. This may be in
part due to changing scenario with
more clinicians preferring to practice
implantology and ultra conservative
restorative dentistry.

• However, in developing countries like
India, much of Prosthodontic practice
entails construction of complete
denture.
• Thus, basic concepts like vertical
dimension still need to be
developed and studied….

Verticle jaw rel challenge to dentist/dental courses

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