Functional occlusal forces under anesthesia

Functional

occiusal forces under anesthesia

J. De Boever, L.D.S., D.M.D.,* M. M. Ash, D.D.S., M.S.**** University

of Michigan,

W. D. McCall,

School of Dentistry,

Ph.D.,**

Ann Arbor,

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 thresholds 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 directions.‘, * Other studies have demonstrated a decrease in the exerted static force correlated to the degree of anesthesiaadministered.3, 4It has also been observed that the decreasein exerted force after anesthesiaof 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 muscleactivity is altered for voluntary events. Other studies in which the teeth were mechanically stimulated did not demonstrate change in the electromyographic (EMG) reaction recorded after anesthesia.“-” In other experiments, however, a different EMG responsehas 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, University of Michigan. ****Professor and Chairman, Department of Occlusion, University of Michigan.

az

OCTOBER1978

VOLUME40

NlJMISER4

Mich.,

S. Holden,

M.S.,***

and

and Gent State University,

Belgium

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 miniature strain gaugeswere embedded 1.5 mm under the occlusal surface, four under the cuspsand 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 ~wasseated 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 electromyographic 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 seriesof recordings was made with the experimental transmitter fixed partial denture prior to anesthesiato verify the operation of the transmftter and establish a baseline for comparison after anesthesia. The following events were recorded after anesthesia 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

Subject N

Legend:

Event

5

6

7

8

9

10

11

12

13

14

15 16.00 0.93

19 18.50 1.02

17 19.00 0.89

21 17.50 1.20

24 23.00 1.04

15 15.75 0.95

15 17.25 0.87

15 14.00 1.07

15 16.50 0.90

1.5 21.50 0.6"

15 18.50 0.81

12 23.00 0.52

14 26.50 0.53

11 19.00 0.57

13 21.00 0.61

15 34.00 0.44

15 34.00 0.44

15 30.00 0.50

15 31.00 0.48

15 19.00 0.78

15 25.00 0.60

I

T F Subject N T F

4

II

N T F No.

= Number of strokes. = Duration. = Frequency. 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 mandible. Event No. 5-Chewing bread on the left side. Event No. 6-Chewing bread on the fixed partial denture side. 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 intercuspal position. Event No. 14-Tapping the teeth with the mandible 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 ratories, Inc., New York, N. Y.

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1:20,000,

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Cook-Waite

Labo-

dose was tested, and if necessary, additional local anesthetic was administered. The experiments started assoon as the anesthesiawas complete in the upper and the lower jaw. In each subject the events were repeated several times. The EMG traces were interpreted by visual examination for determination of the electrical activity at rest, chewing frequency, contraction pattern, synchronization of contractions, and possible hyperactivity. 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 casesthe 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.

403

v;m~ 2. iv+ 2 ... i 0” i.-.-LL 1 2 3 4 5 6 7 8 3

1G

DE BOEVER

ET Ai

11

ii

12

!!

: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).

/ w

l

l

d

5

.4

.6

.8

NORMAL

1.0

CHEWING

1.2

1.4

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.

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 anesthesia). RESULTS Although positioning

I i.2-I

?5-

LL

6

-&

I

1

2

3

U

5

6

7

8

9101112131~15

CHEWING STROKE Fig. 2. Force in pounds exerted on each of eight straingauges in chewing a paraffin tablet under local anesthesia (subject I).

the subjects reported some difficulty in food on the anesthetized side (particularly 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, disappeared after a few minutes. The number of chewing strokes necessary to masticate the food, the total duration, and the chewing frequency (number of strokes divided by the duration) are given in Table I. The frequency data plot in Fig. 1 also compares anesthe-tizedchewing to the chewing frequency without anesthesia. For the great majority of events the chewing frequency was less for a particular food when that food was chewed with the jaw anesthetized. 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

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NUb4BER

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OCCLUSAL

FORCES

UNDER

ANESTHESIA

1

2

3

tl

s

6

7

8

CHANNEL NUMBER

CHRNNEL 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).

.

f

* : 123’45678

123(15678

CHANNEL DUMBER

CHANNEL NUMBER

Fig. 6. A, Average force in s&ject II exerted on eight different sites (channelnumbers)of the occlusalsurfaceduring all chew&g events with anesthesia(lozoerhistogram) and without anesthesia(tipper kistogram). B, Average force in subject II exerted on eight different sites (channel 14).

numbers)

of the occlusal surface during

the peak force was fessthan 3.5 pounds in 95% of the chewing strokes. For subject II the force was lessthan 5.0 pounds in 95% of the strokes. Statistical analysis comparirig events with anesthesia to events without anesthesiais summarized in Tables II and III. Significant differences were observed

The given

for 16 of the 20 events.

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

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voluntary

movements

(events 4, 13, and

working side (events 6, 8, IO, and 12) with anesthetized nonworking side (events 5, 7, 9, and 11). The forces exerted while chewing unilaterally on the anesthetized side were si~~~~ly b&her than the forces exerted when chewing an the other sidefor 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, anesthetized

405

DE BOWER

Table II. Average force (pounds)

ET AL

in each event exerted on the occlusal surface (subject 1) Event*

Average force

4

Without ant%thesia With anesthesia P

5

6

7

2.35

0.601

1.03

0.555

0.448

0.708

1.11

0.963

NSS

NS

.CQl

.OOli

8

9

10

11

12

13

14

2.32

0.407

0.706

0.501

2.21

0.989

0.983

1.10

0.584

2.95

1.05

1.06

0.890

1.39

,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 Without anesthesia With anesthesia P

4

5

6

0.193

0.583

1.00

2.53

.001t

.OOl

7

8

0.769

1.20

.2.27

2.07

1.78

.OOl

.CKJl

9

11

13

14

0.935

0.585

0.553

0.661

2.39

1.56

2.10

0.960

0.274

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 anesthetized conditions (lower histogram) are subtle, in chewing (Fig. 5, A) and in other events (Fig. 5, B). The highest forces were exerted under the buccal, supporting cuspsand 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 channel 1 (mesial fossaof the lower molar). 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 mechanismsare important to the timing of the central involuntary chewing pattern generator, as has been postuiated by Dellow and Lund.‘” Electromyography. The EMG results of this study 406

are in agreement with those of SchPrer and associates.5Except for a few strokes, the chewing pattern was coordinated and synchronized. However, the EMG amplitude did not decreasesignificantly. 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 minimum values were highest in the nonfunctional voluntary movements (other than mastication and swallowing). 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 anesthesiaare due to the-anesthesis itself and not to variations in function. Schgerer and associates5have reperted that similar tooth contact patterns were found with andwithout anesthesiaduring chewing but not for light tapping movements. The results of this study OCTOBER

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OCCLUSALFORCESUNDERANESTHESlA

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

Table IV. Analysis of average force (pounds) exerted on the occlusal surface in chewing bilaterally

(subject I)

Event*

Event*

Signilkance

Significance of 5 Average force exerted Oil

6t

7

St

9

0.79 1.07

.OOI$ .oso .OOl WI

0.96 1.02 0.58 2.90 1.04 1.06

occlusal surface *See Table I for key to events. TChewing on the anesthetized fixed $Highiy significant difference. ~Significant difference. I/Not significant difference.

of

1Of 11 12f differencet

partial

denture

side.

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 changesin tooth contact between antagonists. The amount of force exerted under anesthesiawas, in all the chewing events except two, the same (subject I, chewing bread; subject II, chewing peanuts 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 movements. In subject I the forces exerted by chewing on the anesthetized fixed partial denture side were significantly higher than those exerted by chewing on the other side. In subject II the changesoccurred in both directions. This phenomenon also occurred in chewing without anesthesia for these two subjects.‘* Therefore it is not possible to attribute these differencesto anesthesia. The differences with other studies5 may result from the difference in anesthetizing the temporomandibular joint and from the small samplesused 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 THEJOURNALOFI'ROSTHETKDENTISTRY

5 Average force exerted on occlusal surface

2.54

6t

7

St

dilfemncet

1.75

2.46

.m$ .001

2.07

*See Table I for key to events. TChewing on the anesthetized fixed $Highly significant difference.

partial

denture

side.

of the temporomandibular joints, perception decreased and maximum mandibular opening increased.‘“. 2oHowever, 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 seemsthat 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 mentioned, 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 suggestedthat 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 mechanism.” 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 significant role of the mucosaand 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 peripheral afferent stimuli in chewing, swallowing, and

DE BOEVER

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.

10.

11.

12.

13. 14.

15. 16.

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 elektronische 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.:

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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 functional occlusal forces. J PR~STHET DENT (In press.] Ablgren, J.: An inter-cutaneous needle electrode for kinesiologic 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 telemetric 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.: Contributions to the reflex control of mastication from mechanoreceptars 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 swallowing with and without anesthesia of the temporomandibular joints. Acta Odontol Stand 29~549, 1971.

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