A comparison of jaw relation recording methods

A COMPARISON RAYMOND

OF JAW

C. WALKER,

MAJOR,

USAF Hospital Keesler (ATC),

RELATION

RECORDING

METHODS

USAF (DC) Keesler Air Force Base, Miss.

BELIEVE that as a result of swallowing, the mandible assumes its most retruded position, which they contend is centric relation. Other dentists maintain that as a result of swallowing, the mandible assumes an ideal physiologic position which is not necessarily the most retruded position; this “ideal” position they call centric relation. These conflicting concepts have led to confusion in thinking and communication about centric relation. The purpose of this study was to investigate the problem by comparing two methods of recording centric relation : the physiologic (or swallowing) method and the graphic (or needlepoint tracing) method.

S

OME DENTISTS

MATERIALS

AND METHODS

In a graphic method, an extraoral stylus* is joined to the upper occlusion rim and adjusted to contact a flat metal surface attached to the lower occlusion rim at the vertical relation of occlusion. This relation is maintained by an intraoral central bearing device. As the mandible is moved to both the extreme right and left positions, the stylus scribes a tracing similar to a Gothic arch. The jaws are considered to be in centric relation when the stylus is at the apex of the tracing (Fig. 10 j . The physiologic method utilizes the repeated act of swallowing to register centric relation. To obtain this record, I used metal studs (Fig. 1) embedded in the lower occlusion rim. The studs were opposed by soft wax in the upper occlusion rim (Fig. 5). I designed a special analyzing instrument similar to those used by Posseltl and Sear? for registering positions of the lower jaw in order to compare the registrations of these methods (Fig. 2). This instrument measures the differences between various relations of the mandible to the maxillae as recorded at five points in space, The intercondylar shaft has adjustable pins through its axis to indicate positions on vertically placed lateral grid plates (sagittal plane j (Fig. 2, A and B) . An adjustable pin (Fig, 3) is inserted into the labial flange of the upper occlusion rim to indicate positions on a vertically placed frontal grid plate (frontal plane) (Fig. 2, C) , A posterior, horizontally placed grid plate is located at the center of the intercondylar shaft to indicate lateral shift (Fig. 2, 0). An anterior, horizontally placed grid plate Condensed from a thesis presented in partial fulfillment of the requirements for the degree of Master of Science at the Ohio State University, College of Dentistry. The views expressed are those of the author and in no way reflect the views of any cornponent of the United States Air Force. Wanbery’s Check-Bite Appliance. 685

686

J. Pros. Den. July-August, 1962

WALKER

is located beneath the incisal pin to indicate anteroposterior differences (horizontal plane) (Fig. 2, E). The results were measured at millimeter grids : two oriented in the sagittal plane, two in the horizontal plane, and one in the frontal plane. PROCEDURE

Three criteria were used to select 21 edentulous subjects. The residual ridges had to be as nearly ideal as possible, and the subjects had to be both willing and able to cooperate. A case history was recorded for each subject with particular emphasis upon the cause, sequence, and time of the loss of teeth. A record was made as to whether a dental prosthesis had been worn and for what length of time. Senior dental students at the Ohio State University, College of Dentistry, who were constructing dentures for these patients, made the impressions and casts for the subjects.* As soon as the casts were completed, I duplicated them, and on the duplicate casts, I constructed cold-curing acrylic resin bases in flasks by the compression method (Fig. ‘4). I formed hard baseplate wax occlusion rims on the resin bases and shaped the rims to be as similar to the outline form of the finished dentures as possible (Fig. 5). I was careful to provide ample space for the normal movement of the tongue during swallowing.4 The vertical relation of occlusion was established, and the necessary interocclusal distance was provided.5 Then, I embedded pyramid-shaped metal studs in the occlusal surfaces of the lower rim in the first molar region on both sides. Only the pyramids of the studs projected above the surface. I removed a section of the hard wax on the occlusal surface of the upper occlusion rim opposing these pyramids and replaced the hard wax with a very soft wax.+ An adequate interocclusal clearance at the rest position was provided (Fig. 5).

I?&. during

l,Pyramid-shaped swallowing.

metal

studs

(enlarged)

permit

an interocclusal

record

to

be made

The subject was not told the purpose of the experiment but was encouraged to be at ease. He was seated in a comfortable upright position as free as possible from distracting influences. His head was not supported. The occlusion rims were inserted into the subject’s mouth along with a small piece of hard candy to stimulate salivation. The subject was told to imagine that the occlusion rims were his own teeth and to suck, not chew, the candy. After the *Impressions and casts were tTrubyte Equalizing Wax.

made

in accordance

with

principles

of Boucher.8

Volume 13 Number 4

COMPARISON

OF JAW

RELATION

Fig. 2 .-The indicator pins of the analyzed respective grids: (A and B) lateral grid plates; grid plate; (E) anterior horizontal grid plate.

RECORDING

instrument (C) frontal

METHODS

are grid

687

set at the zero points of their plates; (DJ posterior horizontal

subject had swallowed several times, I removed the occlusion rims and inspected the indentations made in the soft wax. Sometimes it was necessary to trim, reshape, or reposition the soft wax to secure clear indentations of only the pyramids (Fig. 6) .6 This procedure was continued until I was sure the subject had repeatedly swallowed in a normal, unstrained manner. Normal swallowing has been described as being associated with an uninterrupted motion of the hyoid bone.7-Q After removing the occlusion rims from the mouth and chilling them in cool water, I keyed them together so that the metal pyramid studs were precisely seated in their indentations. This relationship was maintained by metal struts that were attached to the lateral surfaces of the occlusion rims by sticky wax (Fig. 7). The occlusion rims were centered in the instrument and mounted with the occlusal plane parallel to the base. The indicator pins were set at zero (Fig. 8 j . Next, I attached the tracing device to the occlusion rims and adjusted the central bearing screw to maintain the same degree of jaw separation as used in the physiologic method (Fig. 9).

lary

Fig. S.-The adjustable occlusion rim.

indicator

pin

(enlarged)

attaches

to the

labial

aspect

of the

maxil-

688

J. Pros. Den. July-August, 1962

WALKER

I reinserted the occlusion rims into the subject’s mouth and directed him to register a needlepoint tracing upon the recording plate. After a sharp apex was developed on the tracing plate, I instructed the subject to hold the lower jaw with minimal pressure in the position where the stylus was at the apex of the tracing. Fig.

4.

Fig.

5.

Fig.

6.

Fig.

7.

Fig. 4.-The acrylic resin bases are made of cold-curing resin. Fig. B.-The occlusion rims have an external form similar to that of a complete denture. The metal studs are embedded in the mandibular occlusion rims, and soft wax is embedded in the maxillary occlusion rims. Fig. B.-Indentations are made in the soft wax of the upper occlusion rim by the metal studs. Fig. 7.-The occlusion rims are held together by metal struts and sticky wax.

Fig.

8.

Fig. 8 .-A registration made by the swallowing method with the indicator pins set at zero. Fig. 9.-The tracing device is attached to the occlusion used for the swallowing method.

Fig. is mounted

9. in the analyzing

instru-

ment

rims

at the same

vertical

relation

as

;;l;tle;

‘4”

COMPARISON

OF JAW

RELATION

RECORDING

6X9

METHODS

Then I injected fast-setting plaster into the molar region on either side of the mouth (Fig. 10). Next, I withdrew the intercondylar pins from the lateral grid zero holes so that the upper member of the analyzing device was free. I seated the occlusion rims with their new relationship upon the previous plaster mounting oi the lower member of the analyzing device (Fig. 11). Finally, I seated the free upper member of the analyzing device together with the plaster mounting made previously on the upper occlusion rim and observed and recorded the differences between the two methods at the five grid plates (Fig. 12). RESULTS

The graphic method for registering centric relation did not locate the mandible in the same position as did the swallowing method. By the graphic method, the

Fig. recorded

lO.-The centric

occlusion relation.

rims

and

the attached

tracing

mandible was determined to be in a more posterior it was by the swallowing method.

Fig. Fig. Il.-The plaster mounting. Fig. 12.-The rim.

are

relation

11.

registration upper

device

member

fixed

by

the

graphic

of the analyzing

method

instrument

at the

than

12.

is semated on the is seated

plaster

to the maxillae

Fig. made

with

previously

on the maxillary

made occluslor~

J. Pros. July-August,

WALKER

Den. 1962

The pattern of variations between the two methods, as recorded on the grids, is shown in Fig. 13. The zero point of each grid represents the registration by the swallowing method. The other points represent the variations, using the swallowing relation as a reference. The pattern of the graphic method registrations appears to indicate a more anterior relation than the swallowing method demonstrates. This is because the upper member of the instrument has moved rather than the lower member, as would occur in the subject’s mouth. So, while it appears that the indicator pins have moved forward, in effect, the mandibular element has moved backward, carrying the grid with it. Thus, the pattern of registrations for the swallowing method was forward and below that of the graphic method. Grid registrations for the two methods did not coincide in any instance. A few of the swallowing registrations were behind and above the graphic registration; This could have been caused by an error introduced by the displacement of the basal seat mucosa during one or the other methods of registration. These registrations were included in the statistical analysis.

A.

B.

c.

D.

E.

Fig. 13.-The pattern of registrations indicates that the graphic registrations were further posterior than the swallowing records. The arrows orient the grids in the anterior direction. A, Left lateral vertical grid. B, Right lateral vertical grid. C, Anterior horizontal grid. D, Posterior horizontal grid. E, Anterior vertical grid.

STATISTICAL

ANALYSIS

A statistical analysis* of the data indicated that there was a significant difference in the results obtained by the two methods of recording centric relation. Changes in nine different jaw measurements on each of 21 subjects are recorded in Table I. The results of the computations are seen in Table II. The statistic t is used to test the hypothesis p = 0, i.e., that there is no change in the measurement. Small values of t are consistent with ‘the hypothesis ; large values of t imply that a change has occurred. To be considered significantly large in this experiment, t should exceed 1.72. If t exceeds this value, there is only a 5 per cent chance that the inference of change is wrong. Too few subjects were tested to make a correlation between the case histories and the results. However, this is worthy of further investigation. DISCUSSION

from

Niswonger lo stated that during the act of swallowing, the mandible travels rest position to centric relation and back to rest. SwensorP wrote that

*Carried

out by the Statistical

Laboratory

of the Ohio

State University.

E%Kt?”

COMPARISON

OF JAW

RELATION

RECORDING

METHODS

691

swallowing usually brings the mandible to a retruded position and is an aid in securing this relation. Boucher12 agreed that the mandible does tend to move to the position of centric relation and to the level of occlusion when swallowing occurs. On the other hand, Posselt13 claimed the mandible never moves to the hinge position during swallowing. Other investigators have demonstrated a close association between swallowing and centric relation by use of motion pictures,9 serial roentgenography,i4 cephalometry,s cinefluorography,15 and electromyography.la Still others have concurred. 17-26Some dentists have used the act of swallowing to locate centric relation for the construction of dentures.27-20 Unfortunately, all who agree that swallowing has a correlation with centric relation do not agree on the exact location of the mandible in centric relation. These writers have been divided loosely into two schools of thought. One group describes its concepts as “physiologic” and refers to the other group as “mechanistic.” The description of “mechanistic” is unjust, for it implies the use of mechanics to the exclusion of the physiologic factors involved. It is more correct to say that one group places greater emphasis on certain factors controlling mandibular positions and movements than the other. The members of the mechanistic group believe that the retruded relation of the mandible is an essential part of the envelope of jaw movement involved in a functioning occlusion. 11*30-32They maintain that the most retruded relation of the mandible to the maxillae must be recorded after the vertical relation of occlusion is established. They call this retruded position of the mandible centric relation. They say that centric relation is a border position at which a posterior terminal hinge axis through the condyles controls the arc of mandibular closure to centric occlusion.33-3” They propose many methods for locating centric relation. All methods have both merit and fault. However, the graphic, or needlepoint, method is probably the one used most.3s Some authors33s37 in the mechanistic school define centric relation in terms of the terminal hinge axis and believe an attempt to locate it without finding the hinge axis or rotational center of the mandible is unscientific. It seems unreasonable to define centric relation by a selected, specific method for recording it. The method of location is less important than the fact of its location. Many of these dentists recognize that the mandible in some patients may assume a habitual position which is not the most retruded position. They provide for this habitual position in their occlusal plans.3R-42 The advocates of the “physiologic” concept believe the neuromusculature is the dominating factor in mandibular movements and positions.20-26 They contend that centric relation is determined by reflexes learned in infancy and retained after the teeth are lost. They maintain that centric relation is not the most retruded relation of the mandible to the maxillae, but an intermediate relation in which the joints, muscles, teeth, and supporting structures are in equilibrium. They believe this intermediate position to be the optimal starting point from which the occlusal pattern should be established. They contend that the most retruded position is a strained position and that it should be ignored in building occlusions.14~21~43 The! question the mechanistic concept of some that a precise axis through the condyles

J. Pros. July-August,

WALKER

692 TABLE I.

Den. 1962

DIFFERENCES BETWEEN GRAPHIC AND SWALLOWING METHODS (MEASURED TO 0.1 MM.)

=

cF 2

-2 Y I !z @; ?& ;zg 5;; 2.0 0.2 1.0 2:

2.5 1.0

: -0.5 -1.0 8 t 0 1.5 0 1.5 1.5 1.0

-2 ii 2 E 2s;; $S$ J& f4SN arz UdO zea 2.0 1.0 1.0 1.0 -1.0 1.0 8 0.9 3: -Y 0 0:8 -1.0 1.2 1.5 -0.5 1.0 1.5 1.0

2.0 2: 1.0 -1.0 2.0 0 ::: -0.2 0 1.0 i -1.0 2.0 0.5 0.5 1.5 1.5 0.1

2.0 0.3 2.0 2.0 0 1.0

2.0 a.0, 2:o 0.5

0.2

:4 0:s

4.2 0.5 -0.5 0.8 -1.0 2.2 0.5 -0.5

: 0 0.1

82 -0.3 0.8 -0.5 2.0 1.0 -0.2 2.0 1.9 1.1

8:: 0.5

A:: : 0.1

ii.5

x -2.0 0.2 -1.0 -0.4

i.2

-8

: 0

Fl 0

-I

TABLE II.

::: 0.5

8 0 0.1

2:

: 1.0

0.8 0.2

8

5 1:o 8::

RESULTS OF STATISTICAL ANALYSIS OF 21 PATIENTS

IDENTIFICATION Left lateral vertical grid (horizontal difference) Left lateral vertical grid (vertical difference) Right lateral vertical grid (horizontal difference) Right lateral vertical grid (vertical difference) Anterior horizontal grid (anterior difference) Posterior horizontal grid (anterior difference) Posterior horizontal grid (difference to the left) Posterior horizontal grid (difference to the right) Anterior vertical grid (vertical difference)

MEAN 0.5762 0.4952 0.709.5 0.5857 1.0048 0.6619 iE2 0: 1810

-

S.D.

t

0.9104 0.8941

2.90 2.54

EE 0: 8273 0.5912 0.1209

ii:;; 5.57 5.13 1.98 2.22 1.12

X: :2:

The value of t at the 5 per cent level is 1.72.

controls mandibular movements. They cite the excellent function which continues after surgical removal of the condyles.14144 It is my opinion that the mandible does not necessarily assumethe position of centric relation during the function of mastication. However, the fact that a patient

Volume Number

12 4

COMPARISON

OF JAW

RELATION

RECORDING

METHODS

693

can and may bring the teeth together in the most retruded position warrants provision for it in the occlusal plan. The definition of centric relation should not be alt’ered to agree with selected, specific concepts of the way in which the mandible operates. Rather, centric relation should remain a static, anatomic, repeatable reference position to which all other mandibular positions may be related, both for the planning and construction of occlusions and for communicating ideas concerning them. The unreliability of the neuromusculature for determining mandibular positions repeatedly has been demonstrated by Atwood.45 SicheF has explained that the learned neural patterns of the dentulous patient need constant relearning, and with the loss of the teeth, these patterns begin to fade. Although he doubted that the most posterior position of the mandible is a functional position, he agreed with others that an edentulous patient may learn to use this position. In so doing, the patient is aided by a new set of proprioceptixe signals initiated by the unique tension of the capsular ligament. I found that the needlepoint tracing method registered a more retruded position of the mandible than the swallowing method in most instances. It is my opinion that the act of swallowing is unreliable for determining the position of centric relation according to the definition: “Centric relation is the most posterior relation of the mandible to the maxillae at the established vertical relation.” Swallowing could be important in determining the location of possible habitual mandibular eccentric positions. However, in using these habitual positions as the basis of an occlusal plan, there may be a danger of perpetuating a pathologic relation, since most patients who require dental prosthesis have had debilitated occlusion. SUMMARY

ANmD

CONCLUSIONS

The importance of universal acceptance and understanding of centric relation is necessary for the clear conveyance of ideas. Centric relation is the most posterior relation of the mandible to the maxillae at the established vertical relation. The act of swallowing was shown to be unreliable for the registration of centric relation according to this definition. However, swallowing may be of value in the determination of possible habitual positions of the mandible. REFERENCES

Posselt. U. : An Analyzer for Mandibular Positions, J. PROS. DEN. 7 :368-374, 1957. Sears, V. H. : Mandibular Condyle Migrations as Influenced by Tooth Occlusions, J.A.D.A. 45:179-192, 1952. Boucher, C. 0. : Impressions for Complete Dentures, J.A.D.A. 30:14-25, 1943. :: Rushmer. R. F.. and Hendron. T. A.: The Act of Derrlutition. A Cinefluorograuhic Studv. - _ J. Appl. Physiol. 3:622, ‘1951. 5. Kaires. A. K. : Palatal Pressures of the Tongue in Phonetics and Deglutition, J. PROS. DEN 7:305-317, 1957. 6. Lytle, R. B.: Complete Denture Construction Based on a Study of the Deformation of the Underlying Soft Tissues, J. PROS. DEN. 9:539-551, 1959. 7. Mosher, A. P.: X-ray Study of the Movements of the Tongue, Epiglottis and Hyoid Bone in Swallowing, Laryngoscope 37:235, 1927. 8. Bodine, T. A.: A Study of Vertical and Centric Relations by Means of Cranial Roentgen010~. T. PROS. DEN. 9:769-774. 1959. 9. Syrop, H. M.: Motion Picture Studies of the Mechanism of Mastication and Swallowing. J.A.D.A. 46:495-504, 1953.

2:

J. Pros. Den. July-August, 1962

WALKER

694 10. Niswo;yi5L i: 14. 15. 16. :87:

E.: The Rest Position of the Mandible and the Centric Relation, J.A.D.A. ‘2-1582, 1934. Swenson,rM. G. -_ : Comolete _-.-- --.- -Dentures, -~~ ed. 3, St. Louis, 1953, The C. V. Mosby Company. Boucher, C. 0. : Thro&h the E,yes of the Editor, J. PROS. DEN. 5:294, 1955. Posselt. U.: Occhr sal Relationshins in Deglutition, Compendium of the American Equilibration Socie :ty, 1959. Sheppard, I. M., J:scobson, H. G., Zaino, C., and Poppel, M. H.: Dynamics of Occlusion, J.A.D.A. 58 :77-g4 1q5q Jankelson.., R -., mn, ,,&ran;‘&-M., and Hendron, J. A.: Physiology of the Stomatognathic Sl rstem, J.A.D.A. 46:375-386, 1953. Shpung 8, H., and Shpuntoff, W. : A Study of Physiologic Rest Position and Centric Position by Electromyography, J. PROS. DEN. 6:621-628, 1956. Rix, R. E. : Deglutition and the Teeth, D. Rec. 66:103-108, 1946. Perry, H. T., and Harris, S. C.: The Role of the Neuromuscular System in Functional Activity of the Mandible, J.A.D.A. 48 :66.5-673. 1954. Jankelson, B. : Physiology of Hl~man Denta 1 Occlusion, J.A.D.A. 50:664&O, 1955. Naele. -.-u--z R. - IT. : Temooroma rndibular Function, J. PROS. DEN. 6:350-358, 1956. Shanahan, T. E. f : Physiologic Vertical Dimension and Centric Relation, J. PROS. DEN. “_

% 21:

6:741-747

_--.-.-.

1Wh

22. Movers. R. :E.‘; ‘SomF- Physiologic PROS. DEN.

I-*---

6:183-194

Considerations

of Centric and Other Jaw Relations, J.

1956.

Holic, R. : Centric Registration in Full Denture Construction, J.A.D.A. 36:2%-301! 1948. Bar, U., and Brill, N.: Modern Concepts of Reflexes and Registrations to Obtain Centric Occlusion and Centric Relation in Prosthetic Dentistry, D. Abst. 4:7, 1959. Articulation, 25. Naylor, J. G. : Role of the External Pterygoid Muscles in Temporomandibular J. PROS. DEN. 10:1037-1050. 1960. 26. Silverman, S. I.: Denture Prosthesis and the Functional Anatomy of the Maxillofacial Structtn .es. T. PROS. DEN. 6:305-331, 1956. Hughes.--I G. A.. aua Reeli. C. P.: WI lat Is Centric Relation? J. PROS. DEN. 11:16-22,1961. -- --I E: Shana ha42 T.52 J. : The Individual Occlusal Curvature and Occlusion, J. PROS. DEN. 8:2302

Jamieson,‘C. H:: A Modern Concept of Complete Dentures, J. PROS. DEN. 6:582-592, 1956. 5;: Trapozzano, V. R. : Analysis of Current Concepts of Occlusion, J. PROS. DEN. 5 :764-782, 1955. Relationship of Centric Relation, J. PROS. DEN. 31. Kingery, R. H.: The Maxillomandibular 9:922-926,

1959.

Boucher, C. 0. : Occlusion in Prosthodontics, J. PROS. DEN. 3:633-656, 1953. ii. Granger, E. R. : Centric Relation, J. Pros. DEN. 2:160-171, 1952. The Transverse Hinge Axis : Real or Imaginary, J. PROS. DEN. 34: Weinberg L5f.:

9:775-

35. Kurth,3i2’E,5$

1:327-

Feinstein, I. K. : The Hinge Axis of the Mandible,

J. PROS. DEN.

36. Academy ‘of Denture Prosthetics : Principles, Concepts, and Practices in Prosthodontics. A Progress Report, J. PROS. DEN. 9:528-538, 1959. 37. Lauritzen, A. G.: Function, Prime Object of Restorative Dentistry; a Definite Procedur; to Obtain It,. J. Distract of Columbia D. Sot. 32:19-28, 1957. Boos, R. H. : Physrologic Denture Technique, J. PROS. DEN. 6:726-740, 1956. i! Trapozzano, V. R. : Occlusal Records, J. PROS. DEN. 5:325-332, 1955. 40: Schuyler, C. H.: Principles Employed in Full Denture Prosthesis Which May Be Applied in Other Fields of Dentistry! J.A.D.A. 16:2045-2054, 1929. Sears, V. H. : Centric and Eccentric Occlusions, J. PROS. DEN. 10:1029-1036, 1960. E: Kurth, L. E. : Methods of Obtaining Vertical Dimension and Centric Relation : A Practical Evaluation of Various Methods, J.A.D.A. 59:669-673,.1959. 43. Moyersbc. E.: Proceedings of the Socrety of Oral Physrology and Occlusion, Nov. 13, A,.,.,.

44. Boucher, L. J.: Limiting Factors in Posterior Movements of Mandibular Condyles, J. PROS. DEN. 11:23-25,1%1. 45. Atwood, D. A.: A Cephalometric Study of the Clinical Rest Position of the Mandible. I. The Variability of the Clinical Rest Position Following the Removal of Occlusal Contacts, J. PROS: DEN. $:504-519, 1956. 46. Sicher6;. YTIZ Brologrc Srgmficance of Hinge Axis Determination, J. PROS. DEN. 6:616I . USAF HOSPITAL KFXSLER (ATC) KEESLER

AIR FORCE BASE, MISS.