The effect of Nitrous Oxide Psychosedation on
Pantographic Tracings. A preliminary study
Kamal Fareed, BDS,
MS
Department of Restorative Dental Sciences, College of
Dentistry, King Saud University, P.O.Box60169,
Riyadh 11545, Saudi Arabia.
The form and reproducibility of pantographic tracings under the
influence of relaxant drugs and in patients with muscle dysfunction and TMJ disorders,
tend to emphasize the dominance of the neuromuscular factors. The purpose of
this study was to demonstrate the effect of nitrous oxide induced
psychosedation, on the reproducibility of pantographic tracings of border
movements of the mandible. This study included four male subjects (with no
signs and symptoms of muscular dysfunction and temporomandibular joint
problems). Operator guided border tracings were recorded using the Denar
pantograph. Three sets of tracings were recorded: (1) three tracings prior to
sedation (Tracing I); (2) one tracing prior to sedation and two after sedation
(Tracing II); (3) three tracings after psychosedation (Tracing III). The
coincidence of tracings I, II, and 111 were statistically analyzed applying the
chi-square (X2)
analysis. There was a significant difference in the coincidence of tracings
between Tracings 1 and II (X2 = 14.892). There was no significant difference
in the coincidence of tracings between Tracings I and III (X2 = 1.338). This suggests that nitrous oxide
psychosedation produces a centrally induced relaxation of the musculature, by
possibly eliminating the extraneous anxiety producing factors.
The architecture of
the temporomandibular joints (TMJ), the ligaments, and the neuromusculature of the
masticatory system, constitutes the basis for
border movements. There is a lack of general agreement with regard to the
extent to which each of these dictates function.1,6
The reproducibility of
pantographic tracings appears to suggest the fixed ligamentous and bony
elements as the primary factors.1,6,7Studies demonstrating a definitive change on both
the form and reproducibility of the tracings, under the influence of relaxant
drugs8-11 and in patients with muscle dysfunction and
TMJ disorders,12-16 tend to emphasize the dominance of the
neuromuscular factors.
Studies have used
syccinylcholine and curare, muscle
relaxants which interfere
with basic neuromuscular
physiology1, 8,
9 and valium, orally and
intravenously, where the degree of sedation cannot be titrated from individual
to individual.10-11
Also, the
reproducibility of pantographic trac ings of the mandible involves not only
considerable skill by the operator, but also the need for patient cooperation.
The latter, in itself, is a limitation since the elaborate pantographic
equipment used could also induce a stressful situation in the patient.Nitrous
oxide psychosedation creates an envi ronment in both patient and operator,
where the elements producing anxiety are greatly suppres sed. It is the oldest gaseous anesthesia in use
today. The exact mechanism by which it exerts its effect is currently
unknown.17
The degree of sedation
can be controlled by the use of nitrous oxide psychosedation and this would
eliminate the extraneous anxiety producing fac tors, allowing for centrally
induced relaxation of the musculature without the loss of conscious ness.18. This
investigation evaluates the effect of nitrous oxide psychosedation on the
reproducibility of pantographic tracings.
Four male subjects
were selected for the study to possess:
1. Class I occlusal relationship and freedom from of
any signs, or symptoms, of TMJ problems or muscular dysfunction.
2. Sufficient natural teeth to facilitate the
cementation and retention of the clutches.
3. No undue resistance to operator-guided mandibular
border movements.
4. No recent history of upper respiratory tract
infection.
The subjects had a
normal night's sleep, and were asked to avoid any stimulants.
Operator-guided border
tracings were recorded using the Denar pantograph (Denar Corp.Anaheim, Calif.,
USA). Clutches
were fabricated according to the manufacturer's instructions and adapted to the
teeth. The pantographic procedure produces six sets of tracings recorded on six
tables of the pantograph which have pressure-sensitive paper.
Three sets of
operator-guided border tracings were recorded prior to sedation (Tracing I).
Then the recording papers were replaced, and one set of operator-guided border
tracing was recorded prior to sedation. The subjects were then psychosedated
with nitrous oxide, and two more operator-guided border tracings were recorded
on the same paper. Therefore, these recording papers had one tracing prior to
sedation and two after sedation (Tracing II) These recording papers were again
replaced, and then three sets of operator-guided border tracings were recorded
with the subjects psychosedated for at least five minutes (Tracing 111).
In order to evaluate
the sets of tracings for the four subjects accurately, the tracings were
enlarged to twice their size, using a photocopying machine. The laterotrusive
and mediotrusive border tracings were then evaluated for coincidence from
centric relation positions using a magnifying lens. If there were more than one
line present on a tracing being evaluated, it was considered to be
non-coincident. If there was a line greater than 0.5 mm width, it was
considered to be two lines and, therefore, non-coincident.
The coincidence of
tracings I, II, and III to com pare the non-sedated and the psychosedated
states for all the subjects, were studied.
Psychosedation
Technique
The procedure was
first explained to the sub jects. The nose mark was adjusted to ensure the
participants' comfort. A flow of oxygen, 100% at 7 liters/minute was maintained
for one minute.
Nitrous oxide was then
administered at 1 liter/ minute, and oxygen was reduced by 1 liter/minute till
a baseline of the following was achieved.The subjects were asked to report the
onset of any of the following symptoms: A warm feeling, a comfortable glow
through the body, pleasant sen sations, tingling of the fingers, toes or lips,
floating and buzzing sensations, and heaviness of the limbs. The patients were
monitored for the following signs: respiration, eye movements, skin color, and
unusual body movements. The subjects were not allowed to fall asleep.
The
procedure lasted for a maximum of twenty minutes.
For the
four subjects, 48 sets of tracing were evaluated for Tracings I, II, and III,
respectively.
The
tracings were evaluated in the following categories:
1. Tracings I vs. Tracings II (Table I).
2. Tracings I vs. Tracings III (Table II).
The data
were statistically analyzed applying the chi-square (X2) analysis with 1 degree of
free dom.19
The
chi-square analysis showed the following:
1. There was a significant difference in the
coincidence of the tracings between Tracings I and II.
2. There
was no significant difference in the coincidence of the tracings between Tracings I and III.
Four normal subjects
were tested in this prelimi nary study demonstrating an effect of nitrous
oxide psychosedation on pantographic tracings. The results suggest that the use
of nitrous oxide seda tion, Tracing II, probably increased the anxiety of the
patients and disturbed the neuromuscular bal ance. Therefore, the tracings
were not reproduci-ble when compared to Tracing I. After a period of time and
when the psychosedation base-line was achieved, Tracings III were reproducible
when compared to Tracings I.
While establishing
that the architecture of the TMJ, the ligaments, and the neuromuscular com
plex constitute the basis for border movements, the literature also reveals
lack of general agreement with regard to the extent to which each of these dic
tate the function.
Pantographic tracings
of mandibular border movements have been shown to be reproducible in subjects
with normal muscle and TMJ function. This has been the parameter used in
various studies, using different forms of sedation, on the effect of
neuromuscular factors.8-11
Posselt1 made tracings of the posterior border movement
on three conscious subjects. After plac ing these subjects under general
anesthesia and curare, he traced the border movements. He found no change in
the position of these movements, and concluded that the ligaments were
responsible for limiting the posterior border movements of the condyles.
Boucher and Jacoby8 studied tracings in an experiment similar to
Posselt. They found that the patients, under anesthesia and curare, could be
moved farther posteriorly than the conscious post erior border position. They
concluded that the muscles were responsible for limiting posterior bor der
movements of the mandible.
McMillen9 conducted a study similar to Posselt and
Boucher and Jacoby, except that succinyl-
choline chloride (Anectine) was used to produce complete muscle flaccidity and
an extraoral pan tograph was used. Operator-guided tracings were recorded. In
all ten subjects recorded, wider lateral border movements were recorded when
the mus cles were made flaccid. Posterior mandibular dis placement was
slight. He concluded that the mus cles, ligaments, and the bony structures all
share the role of limiting mandibular movement.
Dedmon and Scandrett10 studied the effects of intravenous diazepam on
pantographic tracings. The dose used was 15 to 20 mg. They found no widening of
the tracings after the medication. No clinical advantages, or benefits,
resulted from diazepam pre- medication.
Jackson11 studied the effect of administering Val ium (2 mg), orally on
the reproducibility of pantog raphic
tracings of three subjects. There was a signif icant difference in the
reproducibility between the medicated and non-medicated subjects. The per
centage coincidence of border tracings increases significantly, when the
patient is pantographed while under the influence of medication. No signif
icant difference in the reproducibility of border tracings relative to time (1,
1 1/2, 2 and 2 1/2
hours), after medication was recorded. He also concluded that the
neuromusculature appears to
be the overriding factor governing border move ments.
Other studies have
shown that the reproducibil ity of pantographic tracings improves after the
insertion of occlusal splints and with occlusal therapy. These studies suggest
that border move ments and muscle dysfunction may be interre lated.12-14
Pantographic border
movement tracings have also been used in studies involving patients with TMJ
problems and muscular dysfunctions. These studies demonstrate that patients,
with such prob lems, are characterized by low reproducibility of the
pantographic tracings. They also show that the reproducibility is improved when
the dysfunction symptoms were improved.15-16
Anxiety is considered
to be an important factorin patients with muscle dysfunction and TMJ prob
lems. Nitrous oxide and pantographic procedures could be used to assess the
role of the anxiety fac tors associated with these disorders.
Pantography is a
procedure often used during extensive restorative procedures. It is
imperative to have the neuromusculature in a relaxed state to obtain
reproducible tracings for each patient. Nitr ous oxide psychosedation offers a
safe and easy mode of complimenting the efficacy of such a pro cedure, simply
because the psychosedation facility is included in most dental operatories, and
mastery in this technique involves no great effort.
From this preliminary study, the following can be concluded:
1. The neuromusculature is a significant factor in
governing border movements.
2. Nitrous oxide psychosedation produces a centrally
induced relaxation of the muscula ture, when the baseline is properly
achieved, by possibly eliminating the extraneous anxiety producing factors.
3. The effect of nitrous oxide and pantographic procedures on patients,
with muscle dys function and TMJ problems, needs to be studied.
The
author would like to express his gratitude to Dr. Paul Salins, formerly
Assistant Professor, Biomedical Dental
Sciences Department, College
of Dentistry, King Saud University, for administering the
nitrous oxide. This study was supported by the College of Dentistry Research
Center with a Grant No. 1021.
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