Functional occiusal forces under anesthesia

J. De Boever, L.D.S., D.M.D.,* W. D. McCall, Ph.D.,** S. Holden, M.S.,*** and M. M. Ash, D.D.S., M.S.**** University of Michigan, School of Dentistry, Ann Arbor, Mich., and Gent State University, Belgium

lh e sensory afferent receptors in the periodontal ligaments, oral mucosa, and temporomandibular joints, along with the muscle receptors, have all been implicated in chewing, swallowing, and jaw reflexes. However, their relative roles remain controversial.

Reports on the influence of anesthesia on thresh- olds and static bite force “load to tooth” threshold have shown an increase by about one third in the axial direction and nearly double in lateral direc- tions.‘, * Other studies have demonstrated a decrease in the exerted static force correlated to the degree of anesthesia administered.3, 4 It has also been observed that the decrease in exerted force after anesthesia of the mandible was twice that after anesthesia of the maxill8~.~ Eichne? did not observe any significant change in chewing forces after anesthesia. Studies by Schaerer, Legault, and ZandeP have indicated that the influence of anesthesia of the mucosa and temporomandibular joints does not impair chewing and that the relationship between tooth contact and muscle activity is altered for voluntary events. Other studies in which the teeth were mechanically stimu- lated did not demonstrate change in the electromyo- graphic (EMG) reaction recorded after anesthesia.“-” In other experiments, however, a different EMG response has been reported.8-”

MATERIALS AND METIKH)S

For two subjects, one man (age 32) and one woman (age 52), an eight-channel force transmitter was constructed and built into a partial denture that

Supported by USPHS Grant NIDR DE 02731-05. *Associate Professor, Department of Pmsthodontics, Gent State

University.

**Associate Professor, Department of Oral Medicine, University of Buffalo, Buffalo, N. Y.

***Associate Professor, Department of Dental Hygiene, Universi-

ty of Michigan. ****Professor and Chairman, Department of Occlusion, Univer-

sity of Michigan.

az OCTOBER1978 VOLUME40 NlJMISER4

was fixed into the mouth with two small screws. The subjects did not show any obvious signs of trauma from occlusion or functional disturbances of the stomatognathic system. Both subjects were misting one molar in the lower right dental arch. Details of the transmitter, the recording system, and the data analysis have been reported earlier.12 Right minia- ture strain gauges were embedded 1.5 mm under the occlusal surface, four under the cusps and four in the fossae. Their resistance varied linearly with the applied force. Each strain gauge was connected to the transmitter.

Special attention was given to the form of the transmitter fixed partial denture to insure normal function of the muscles. Both subjects had a second removable, nontransmitter fixed partial denture similar in shape to the experimental one for use between recording sessions. The subject ~was seated upright in a dental chair in a shielded room.

Subcutaneous platinum hook electrodes’3 were attached above the right and left masseter muscle, the anterior part of the temporal muscle on the side of the transmitter partial denture, and above the suprahyoid muscles.

The electrodes were separated by 3 mm, at an angle to the length and over the be&of the muscles. An ear clip was used as a ground electrode.

The eight force channels and the electromyo- graphic channels were recorded simultaneously on the 16-channel polygraph with a paper speed of 50 mm/set. The EMG channels were calibrated at 50 V/cm. After an electromyographic recording with

the everyday (nontransmitter) fixed partial denture, a complete series of recordings was made with the experimental transmitter fixed partial denture prior to anesthesia to verify the operation of the transmft- ter and establish a baseline for comparison after anesthesia.

The following events were recorded after anesthe- sia was complete:

0022-3913/78/100402 + 07$00.70/O 0 1978 The C. V. Mosby Co.

OCCLUSAL FORCES UNDER ANESTHESIA

Table I. Temporal parameters. Number of chewing strokes required (events 5 to 8) to masticate and swallow the standardized food, duration of each event, and the chewing frequency

Event

4 5 6 7 8 9 10 11 12 13 14

Subject I N

T F

Subject II

N T

F

15 19 17 21 24 15 15 15 15 1.5 15

16.00 18.50 19.00 17.50 23.00 15.75 17.25 14.00 16.50 21.50 18.50

0.93 1.02 0.89 1.20 1.04 0.95 0.87 1.07 0.90 0.6" 0.81

12 14 11 13 15 15 15 15 15 15

23.00 26.50 19.00 21.00 34.00 34.00 30.00 31.00 19.00 25.00

0.52 0.53 0.57 0.61 0.44 0.44 0.50 0.48 0.78 0.60

Legend: N = Number of strokes. T = Duration.

F = Frequency.

Event No. 4-Lateral gliding movements of the mandible.

5-Chewing bread on the left side.

6-Chewing bread on the fixecl partial denture side. 7-Chewing peanuts on’the left side.

8-Chewing peanuts on the fixed partial denture side.

g-chewing gum on the left side.

IO-Chewing gum on the fixed partial denture side. 1 l-Chewing wax on the left side.

12-Chewing wax on the fixed partial denture side.

13-Tapping the teeth in the intercuspal position. 14-Tapping the teeth with the mandible actively retruded.

Event No. l-Swallowing saliva. Event No. 2-Swallowing water. Event No. 4-Lateral gliding movements of the

Event No. 5-Chewing bread on the left side. Event No. 6-Chewing bread on the fixed partial

denture side.

mandible.

Event No. ‘I-Chewing peanuts on the left side. Event No. 8-Chewing peanuts on the fixed

partial denture side. Event No. g-chewing gum on the left side. Event No. lo-chewing gum on the fixed partial

denture side. Event No. 11-Chewing wax on the left side. Event No. 12-Chewing wax on the fixed partial

denture side. Event No. 13-Tapping the teeth in the intercus-

pal position. Event No. 14-Tapping the teeth with the mandi-

ble actively retruded. The upper and lower jaws on the side of the

experimental fixed partial denture were anesthetized with mepivacaine HCL. * The effectiveness of the

*Garbocaine HCL 2%, Neo-Cobefrin 1:20,000, Cook-Waite Labo-

ratories, Inc., New York, N. Y.

dose was tested, and if necessary, additional local anesthetic was administered. The experiments

In each subject the events were repeated several

started as soon as the anesthesia was complete in the

times. The EMG traces were interpreted by visual examination for determination of the electrical activ-

upper and the lower jaw.

ity at rest, chewing frequency, contraction pattern, synchronization of contractions, and possible hyper- activity.

The force data from the polygraph were measured by an electronic digitizer, which recorded the data on computer cards. For each event the first 15 chewing strokes were measured. In some cases the subject used less than 15 chewing strokes b&ore swallowing. All of the force recordings were taken, including the first few strokes, which were sometimes irregular and abnormal. The results were plotted and analyzed statistically.

The statistics were computed from an analysis of variance program which required a “balanced design,” i.e., missing data could not be tolerated. Since some of the data had missing channels they were deleted. As a consequence, means pllesented in various tables for the same event may not be identical.

THE JOURNAL OF PBOSTHETIC DENTSTRY 403

DE BOEVER ET Ai

/ w d

l l

5 .4 .6 .8 1.0 1.2 1.4

NORMAL CHEWING FREQUENCY

Fig. 1. Scatter diagram of chewing frequency. For each chewing event the abscissa is determined by the chewing frequency without anesthesia and the ordinate by the frequency with anesthesia. Open circles, Subject I. Filled circles, Subject II.

i.2- I

-I

?5- 6 LL

-&

I 1 2 3 U 5 6 7 8 9101112131~15

CHEWING STROKE

Fig. 2. Force in pounds exerted on each of eight strain- gauges in chewing a paraffin tablet under local anesthesia (subject I).

v;m~ 2. iv+ 2 0”

. . . i i.-.--

LL 1 2 3 4 5 6 7 8 3 1G 11 12 ! ! ii :li

LYEWING STROKE

Fig. 3. Average force exerted on the occlusal surface in each of the first 15 chewing strokes during chtiing of wax (subject I).

CHRNNEL NUMBER Fig. 4. Average force of 15 chewing strokes exerted in eight different sites of the occlusal surface during chewing of paraffin (black columns represent without anesthe- sia).

RESULTS

Although the subjects reported some difficulty in

positioning food on the anesthetized side (particular- ly peanuts), the electromyograms were normal

except for the first few chewing strokes, which showed a prolonged activity in the elevator muscles

and a pronounced increase in the activity of the suprahyoid muscles. These changes, however, disap-

peared after a few minutes. The number of chewing strokes necessary to masti-

cate the food, the total duration, and the chewing frequency (number of strokes divided by the dura- tion) are given in Table I.

The frequency data plot in Fig. 1 also compares anesthe-tized chewing to the chewing frequency with- out anesthesia. For the great majority of events the chewing frequency was less for a particular food when that food was chewed with the jaw anesthe- tized.

The data of the force channels were platted out. Representative examples of the many force curves and histograms are given in Figs. 2 to 6. For subject I

OCTOBER 1978 VOLUME 40 NUb4BER 4

OCCLUSAL FORCES UNDER ANESTHESIA

1 2 3 tl s 6 7 8

CHRNNEL NUMBER CHANNEL NUMBER Fig. 5. A, Average force in subject I exerted on eight different sites of the occlus~1 surface during al1 chewing events with anesthesia {!o@er kistagrsm) and without anesthesia (upp~u kis~~~u~~. B, Average force in subject I exerted on eight difFe=nt sites of the occiusal surface (channel numbers) during voluntary movements (events 4, 13, and 14).

123’45678

CHANNEL DUMBER

. f

* : 123(15678

CHANNEL NUMBER

Fig. 6. A, Average force in s&ject II exerted on eight different sites (channel numbers) of the occlusal surface during all chew&g events with anesthesia (lozoer histogram) and without anesthesia (tipper kistogram). B, Average force in subject II exerted on eight different sites (channel numbers) of the occlusal surface during voluntary movements (events 4, 13, and 14).

the peak force was fess than 3.5 pounds in 95% of the chewing strokes. For subject II the force was less than 5.0 pounds in 95% of the strokes.

Statistical analysis comparirig events with anes- thesia to events without anesthesia is summarized in Tables II and III. Significant differences were observed for 16 of the 20 events.

The data obtained for unilateral chewing are given in Tables IV and V. This is a comparison of

anesthetized working side (events 6, 8, IO, and 12) with anesthetized nonworking side (events 5, 7, 9, and 11). The forces exerted while chewing unilater- ally on the anesthetized side were si~~~~ly b&h- er than the forces exerted when chewing an the other side for five of the six pairs of events, In ana~~i~~ the influence of anesthesia on the position of force application over the occlusal surface, the force data obtained during chewing and in voluntary events (4,

THE JOURNAL OF PROSTHETK DENTISTRY 405

DE BOWER ET AL

Table II. Average force (pounds) in each event exerted on the occlusal surface (subject 1)

Event*

Average force 4 5 6 7 8 9 10 11 12 13 14

Without ant%- 2.35 0.601 1.03 0.555 2.32 0.407 0.706 0.501 2.21 0.989 0.983 thesia

With anes- 0.448 0.708 1.11 0.963 1.10 0.584 2.95 1.05 1.06 0.890 1.39

thesia

P .OOli NSS NS .CQl ,001 ,001 ,001 SO1 ,001 NS ,001

*See Table I for key to events. tHighly significant difference.

$30 significant difference.

Table III. Average force (pounds) in each event exerted on the occlusal surface (subject II)

Event*

Average force

4 5 6 7 8 9 11 13 14

Without 0.193 0.583 0.769 1.20 .2.27 0.935 0.585 0.553 0.661

anesthesia

With anes- 1.00 2.53 2.07 1.78 2.39 1.56 2.10 0.960 0.274 thesia

P .001t .OOl .OOl .CKJl NSS .001 .ool ,001 ,001

*See Table I for key to events. tHighly significant difference.

$No significant difference.

13, and 14) were plotted against the channel number.

In subject I the differences in the side of force application under normal (upper histogram) and anes- thetized conditions (lower histogram) are subtle, in chewing (Fig. 5, A) and in other events (Fig. 5, B).

are in agreement with those of SchPrer and asso- ciates.5 Except for a few strokes, the chewing pattern was coordinated and synchronized. However, the EMG amplitude did not decrease significantly.

The highest forces were exerted under the buccal, supporting cusps and in the central fossa.

For subject II (Fig. 6, A and B), the side of force application shifted toward the side of the occlusal surface represented by the marked increase of chan- nel 1 (mesial fossa of the lower molar).

Force. It has been shown in a study’” that without anesthesia the maximum forces during chewing seldom exceed 10 to 15 pounds. The forces varied from subject to subject and with diikrent kinds of food. The diff&rences between maximum and mini- mum values were highest in the nonfunctional voluntary movements (other than mastication and swallowing).

DiSCUSSION

Chewing frequency. EichneP reported that chewing frequency increased under anesthesia. In this study the opposite phenomenon was observed. In the voluntary tapping movements (event 13) the frequency stayed the same in one subject and increased in the other. This would suggest that peripheral sensory mechanisms are important to the timing of the central involuntary chewing pattern generator, as has been postuiated by Dellow and Lund.‘”

In the present study, the forces exerted on the side of the fixed partial denture were found to be greater than the forces on the side without the fixed partial denture. The fact that a day-to-day variation has been observedI was taken into account in analyzing and computing the results of this study. Therefore the observed statistically significant variations in occlusal force under anesthesia are due to the-anes- thesis itself and not to variations in function.

Electromyography. The EMG results of this study

Schgerer and associates5 have reperted that simi- lar tooth contact patterns were found with and- without anesthesia during chewing but not for light tapping movements. The results of this study

406 OCTOBER 1~8 VOLUME 40 NUMBER 4

OCCLUSALFORCESUNDERANESTHESlA

Table IV. Analysis of average force (pounds) Table V. Analysis of average force (pounds) exerted on the occlusal surface in chewing exerted on the occlusal surface in chewing bilaterally (subject I) unilaterally (subject II)

Event* Event*

Signifi- cance of

5 6t 7 St 9 1Of 11 12f differencet

Signilkance of

5 6t 7 St dilfemncet

Average force 0.79 1.07 .OOI$

exerted 0.96 1.02 .oso Oil 0.58 2.90 .OOl

occlusal 1.04 1.06 WI surface

*See Table I for key to events. TChewing on the anesthetized fixed partial denture side.

$Highiy significant difference.

~Significant difference.

I/Not significant difference.

differed for the two subjects. With subject I the side of force application on the occlusal surface was similar with or without anesthesia in chewing and voluntary tapping, corresponding to an unvaried contact pattern between the upper and lower jaw.

With subject II, in all events the side of force application changed in a way corresponding to changes in tooth contact between antagonists.

The amount of force exerted under anesthesia was, in all the chewing events except two, the same (subject I, chewing bread; subject II, chewing pea- nuts on the fixed partial denture side} or higher (11 events).

In the six voluntary movements of the two subjects the exerted force was unvaried in one, lower in two, and higher in three events. This more pronounced variability is probably due to the more important influence of higher brain centers in voluntary move- ments.

In subject I the forces exerted by chewing on the anesthetized fixed partial denture side were signifi- cantly higher than those exerted by chewing on the other side. In subject II the changes occurred in both directions. This phenomenon also occurred in chew- ing without anesthesia for these two subjects.‘* Therefore it is not possible to attribute these differ- ences to anesthesia.

The differences with other studies5 may result from the difference in anesthetizing the temporo- mandibular joint and from the small samples used in both studies.

Role of receptors. Joint receptors have been shown to influence muscle activity, muscle position, and movement of the mandible.‘6-‘8 After anesthesia

Average force

exerted on

occlusal

2.54 2.07 .m$ 1.75 2.46 .001

surface

*See Table I for key to events.

TChewing on the anesthetized fixed partial denture side. $Highly significant difference.

of the temporomandibular joints, perception de- creased and maximum mandibular opening in- creased.‘“. 2o However, the influence of these joint receptors on normal chewing and swallowing has not been shown,5 and their influence on chewing force has not been studied.

It has been reported that the chewing frequency and the site of tooth contact in swallowing did not change after joint anesthesia. The swaliowing reflex and the movement of the mandible and the hyoid bone also did not change.2’ Therefore it seems that the role of the receptors in the periodontal ligaments and oral mucosa may be of greater importance in the regulation of functional forces. As already men- tioned, the results of the studies on the respective roles of the peripheral receptors are controversial. Most of the studies have investigated the possible inhibiting role of the peripheral receptors. However, it has also been suggested that the afferent impulses from the receptors in the periodontal ligament may have not only an inhibiting but also a positive path-generating influence on the chewing mecha- nism.” This can explain the fact that under the influence of anesthesia significant differences in occlusal force occurred (Tables I and II), but in different directions.

The results of this study would suggest a signifi- cant role of the mucosa and ligament receptors in the regulation of the functional forces. It is, however, still doubtful that they play a fundamental role in the regulation of the chewing frequency and chewing pattern.

CONCLUSION

Due to the limited number of subjects in this and other similar studies investigating the role of periph- eral afferent stimuli in chewing, swallowing, and

THEJOURNALOFI'ROSTHETKDENTISTRY

voluntary movements, definite conclusions cannot be drawn. However, it is obvious that the forces exerted under anesthesia are, in most functional movements, different from those exerted under normal conditions. There is some indication that the receptors in the mucosa and periodontal ligaments may influence the exerted funcational forces in a way depending upon the state of the dentition, the threshold of the receptors in the individual subject, and the kind of food.

Other physiologic parameters of the chewing mechanism on the muscle activity, such as the frequency and the position of the force application, seem to be less, if at all, influenced by the peripheral afferent stimuli.

REFERENCES

1.

2.

3.

4.

5.

6.

7.

8.

9.

SchrLider, H.: Lehrbuch der technischen Zahnheilhmde.

Berlin, 1927, H. Meusser, pp 249-309. Cifed & O’Rourke, J. T.: Oral Physiology. St. Louis, 1951, The C. V. Mosby

Company, p 104.

Adler, P.: Sensibility of teeth to loads applied in different directions. J Dent Res Z&279, 1947.

Czeche, F.: Die Bedeutung sensibler afferenzen fur die WiIik~riiche Einstellung des Kaudrucks. Med Diss Halie,

1968.

Arnold, K.: Die Erfassung funktioneller Veranderungen im orofacialen System nach operativen Eingriffen. Med Diss

Nalle, 1972. Eichner, K.: Aufschltisse ilber den Kauvorgang durch elek- tronische Kaukraftmessungen, Deutsche Zahnlrztl Z

19:415, 1964.

Schaefer, P., Legault, J. V., and Zander, H. A.: Mastication under anesthesia. &Ielv Odont Acta 10:130, 1966.

Hannam, A. G., Matthews, B., and Yemm, R.: Receptors

involved in the response of the niasseter muscle to tooth

contact in man. Arch Oral Biol 15:17, 1970. Matthews, B., and Yemm, R.: A silent period in the masseter

electromyogram following tooth contact in subjects wearing full dentures. Arch Oral Bioi 15:53I, 1969.

Beaudteau, D. E., Daugherty, W. F., and Masland, W. S.:

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

DE BOEVER ET AL

Two types of motor pause in masticatory muacies. Am .J

Physiot 21&16, 1969.

G&in, C. J., and Munro, P. R.: EIect~myography of the jaw closing muscles in the open-close-clench cycle in man.

Arch Oral Biol l&141, 1969. Munro, R. R., and Griffin, C. S.: Electromyography of the

jaw jerk recorded from the masseter and the anterior temporalis muscles in man. Arch Oral Biol 16:59, 1969.

McCali, W. D., De Boever, J., and Ash, M. M.: An

eleetromy~aphic and telemetric system for study of func-

tional occlusal forces. J PR~STHET DENT (In press.]

Ablgren, J.: An inter-cutaneous needle electrode for kinesio- logic EMG studies. Acta Odontol Stand 25:15, 1967.

De Boever, J., McCall, W. D., Holden, S., and Ash, M. M.:

Functional occlusal forces: An electromyographic and tele-

metric inv~tigation. J PROSTHET DENT (In press.) Deliow, P. G., and Lund, S. P.: Evidence for central timing

of rhythmical mastication. J Physiol 2f.5: i, 197 1.

Klineberg, I., Greenfield, B. E., and Wyke, B. D.: Contribu- tions to the reflex control of mastication from mechanorecep-

tars in the temporomandibular joint capsule. Dent Praetit

21:73, 1970.

Thitander, B: Innervation of the tempommand~bular joint capsule in man. Trans R Sch Dent Stockj Umea 7:1,

1961.

Kawamura, Y., Majima, T., and Kate, I.: Physiologic role of

deep mechanoreceptors in temporomandibular joint cap sule. J Osaka Univ Dent Sot 7:63, 1967.

Lamson, L. E., and Thilander, B.: Mandibular positioning

The effect of pressure on the joint capsule. ‘Acta Nemo1 Stand 28:337, 1964.

Posselt, U., and Thilander, B.: Influence of the innervation

of the temporomandibular joint capsule on mandibular border movements. Acta Odontol Stand 23:601, 1965.

Ingervall, B., Bratt, C. M., Q&son, G. E., Helkimo, M., and

Lantz, B.: Positions and movements of mandible and hyoid

bone during swallowing. A c~ner~o~aphic study of swal- lowing with and without anesthesia of the temporomandibu-

lar joints. Acta Odontol Stand 29~549, 1971.

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