A comparative analysis of conflicting factors in the selection of the occlusal pattern for edentulous patients

A COMPARATIVE ANALYSIS OF CONFLICTING FACTORS IN THE SELECTION OF THE OCCLUSAL PATTERN FOR EDENTULOUS PATIENTS SAMUEL FRIEDMAN, D.D.S.” New York University,

C

College of Dentistry,

New York, N.Y.

ONTROVERSY AND CONFUSION still persist in the selection of the occlusal pattern

for edentulous patients. Controversy, devoid of emotion and prejudice but based upon fact, contributes to knowledge and progress. Current concepts and opinions are predicated, generally, upon the study and interpretation of such basic factors as the chewing stroke, chewing efficiency, masticatory and nonmasticatory movements, jaw relations, balanced and nonbalanced occlusion, the hinge axis, lateral and protrusive records, anatomic and nonanatomic teeth, porcelain and acrylic resin teeth, the coefficient of friction, the articulator, condyle migrations and the neuromuscular mechanism. POSITION OF THE TEETH

According to studies by Wright, Swartz, and Godwin,l masticatory function starts in the first molar area. On the basis of this finding, they declared it essential to position the mandibular first molar tooth analogous to its location in the natural dentition ; namely, 1.0 to 2.0 mm. helow the top of the retromolar pad. During mastication, the medial fibers of the buccinator muscle, in conjunction with the tongue on one side and with the occlusal surfaces of the upper and lower teeth above and below, assist in the formation of a mechanical trough which retains the bolus of food on the occlusal table. In denture construction, the importance of an occlusal plane or an occlusal level that is in harmonious relationship with the inward bellying of the buccinator muscle and the dorsum of the tongue when in the rest position is apparent (Fig. 1) . The nature of ridge resorption, according to Wright and his associates,2 dictates the setting of the posterior teeth in relation to the center of the stress-bearing area, and not necessarily over the center of the residual ridge. The antserior teeth are positioned at the anterior border of the residual ridge or the anterior border of the stress-bearing area. 1Vhen so set, there will be little or no labial flare of the denture base. This arrangement, it seems, would require modification in the presence of tense, taut lips, scar tissue around the lips, and in atrophy of the lips due to aging. Pound” observetl that, in natural tlentitions, the mandibular posterior lingual Read before the Greater New York Academy of Prosthodontics in Port Washington, N.Y. *Associate Professor of Denture Prosthesis.

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cusps were generally located within xii area Ixmlcrctl ln. t\vo lines that could Ijc’ traced from the m&al surface of the cuspid to the l~ucc:~l arid lingual aspects of the retromolar pad. He suggested that this position be repreduced in artificial dentures, that is, the lower lingual cusps should be slightly huccal to a line drawn from the mesial surface of the cuspid to the lingual aspect of the rctroniolar pad. In the neuromuscular concept, the arch form or arch position is established through the functional action of the tongue and cheeks. ‘Disparity in muscular power, however, between these two forces casts a doubt on the validity of this procedure, It is common practice to set the lower posterior teeth so that a perpendicular dropped either through the buccal cusp or through the central fossa bisects the crest of the ridge. The buccolingual position should not be lingual to the mylohyoid ridge.

Fig. l.--The level of the occlusal the normal tongue position.

plane is established

in a harmonious

relationship

with

DeVan” wrote, “In setting up the teeth the thought of ‘centralization’ and not the crest of the underlying ridge should be the guide. Centralization in setup implies the arrangement of teeth (that contact) as near to the center of gravity of the base plane as the tongue will tolerate.” In any arrangement of teeth, there must be no encroachment upon the tongue position or interference with tongue function. Undue constriction of the dental arch may induce a retracted tongue position. Since ridge resorption and disparity in the ridge relation dictate an almost constant need for compromise, sound clinical judgment must prevail. THE CHEWING

STROKE

Investigation and interpretation of the chewing stroke have kindled varying concepts of prosthetic occlusion. The chewing stroke has been described as elliptical or teardrop in shape. Is there lateral movement at or near the termination of the stroke ? Do the teeth contact in mastication? Is there movement to the opposite terminal lateral position on the nonworking side ? Stansbery5 asserted that the lateral masticatory range was 3.0 mm. in the first molar region. On that assumption, lateral “checkbites” were recorded with the

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J. Pros. Den. Jan.-Feb., 1964

needle point at a distance of 6.0 mm. from the apex of the Gothic arch (needle point ) tracing. Jankelsons declared the teeth do not contact in mastication; and that there is no evidence of eccentric balance during eating nor is there any evidence of protrusive balance in incision. According to Schuyler,7 “It has been shown conclusively that the cycle of mastication does not alway terminate at centric position but that the lower buccal cusps may pass beyond centric position and terminate on the balancing inclines of the opposing upper teeth.” (Fig. 2.)

Fig. 2.-The cycle of mastication. C, The path of the lower buccal cusp point starting from the rest position and first contacting the working incline of the opposing upper tooth, passing through centric position on to the balancing incline, and then returning to the rest position. A and B, Contacting tooth surfaces during the mastication of a bolus of food. A, At the point of first contact. B, At the completion of the cycle of mastication as they appear in a normally balanced occlusion. At the position of first contact, the inclines of the anterior and the posterior teeth on the working side touch simultaneously, broadly distributing the stress. The buccal cusp has passed through centric occlusion on to the balancing incline in its cycle, the muscles of mastication being contracted unilaterally on the working side. The limited number of contacting posterior teeth on that side would be severely traumatized, while the teeth on the opposite side take little if any of the stress. Note that the working incline is nearly parallel to the cycle of mastication, while the balancing incline is nearly at right angle to the closing path. (From Schuyler, J. PROS.DEN. 11:709, 1961.)

Yurkstas and Emerson8 have shown in studies with artificial dentures that in chewing food the balancing side made contact almost 100 per cent of the time and the working side about 70 per cent of the time. The investigations of Anderson and Picton,” Brewer and Hudson,lO Woelfel, Hickey, and Allisonll and others, likewise, fail to support Jankelson’s findings. FACTORS IN MASTICATORY

CONTACTS

The frequency of tooth contacts in mastication is influenced by a variety of factors : (1) The size and character of the bolus. (2) The degree of cuspal coordi-

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nation. In a smooth, well-functioning and coordinated occlusion, the greater efficiency of the chewing apparatus would influence the frequency of tooth contacts. (3) The vigor of chewing or the magnitude of the forces employed. (4) The occlusal pattern. In the natural dentition, sharp cusp formation would be more effective than teeth worn down through attrition. With dentures, the type of anatomic or nonanatomic tooth would influence the frequency of contact. (5) The health of the temporomandibular joints. With painful or diseased joints, the pain or anticipation of pain or discomfort would affect the amount of force exerted by the patient and, consequently, the likelihood of tooth contacts. (6) The health of the periodontium. With a diseased periodontium and a lowered threshold of pain, the fear of discomfort would restrain the patient from exercising the maximum power potential and thus adversely affect the frequency of tooth contacts. (7) The health and character of the supporting structures. With dentures, a patient possessed of a favorable healthy foundation, and the sense of security and freedom from discomfort that they provide, would be encouraged to chew more vigorously. (8) The degree of retention and stability of the dentures. With more stable and retentive dentures, the patient is less fearful of their loosening and dislodgement. The increased confidence encourages more forceful chewing. On the basis of his findings, JankelsonO does not balance dentures in the eccentric positions. He sets nonanatomic teeth to a reverse occlusal curve. THE

REVERSE

CURVE

Boswell12 studied the chewing stroke and related his observations to the occlusal pattern (Fig. 3). He contended that, owing to the nature of the chewing stroke, greater tipping forces were exerted on the lower denture with the spherical and flat patterns of occlusion. These forces, he asserted, were not only unfavorable and destructive to the underlying supporting structures but also tended to draw the lower denture against the sensitive tissues of the mylohyoid ridge. In his opinion, the reverse pattern, through its concentration of masticatory forces upon the more tolerant tissues of the mandible outside the ridge crest, afforded greater patient comfort and increased stabilization of the lower denture. This stabilization is admittedly attained at the expense of the upper denture which, not infrequently, is the less stable denture. The occlusal curve is reversed in the second molar region in order to achieve balance, as suggested by Pleasure.13 Moses14 wrote, “If we arrange the teeth in ‘an anti-Monson fashion, the direction of force will tend to stabilize the lower denture. There is, of course, the danger that the pressure might be of an oblique character and might tend to destroy ridges. At present your essayist is undecided whether destruction of the ridges is greater in the Monson type of setup or in the anti-Monson type. He has been equally successful in destroying ridges with both methods.” With the reverse curve, the lower teeth are shorn of buccal cusps which, in addition to their normal functional role in chewing, also provide better retention for the holus of food upon the occlusal table. Hickey, Woelfel, Allison, and BoucherlS made a study of the effects of various occlusal schemes on the muscular activity of edentulous patients. They state, “The reverse occlusal scheme required the greatest closing muscle activity during the

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chewing of carrots and peanuts. . . . Increased muscle contractions from the closing muscles during mastication could produced increased forces directed toward the supporting structures of the completed dentures. Such increased forces are not thought to be desirable.” Proponents 16,17of the Avery curve claim it is physiologic. Some advocates assert that those natural dentitions that have survived the longest, generally, exhibit this type of wear. They point to the type of occlusal wear seen among primitives and Eskimos to support their viewpoint. On the other hand, O’Rourke and Minor18 state, “The early loss of natural occlusal form in the teeth of primitives and in the teeth of many civilized people is not a normal involutionary process associated with aging. It is pathologic. . . . It is well to keep in mind that life expectancy among primitives is quite short compared to that of civilized man. It is quite probable that if primitives had a longer life expectancy, many of them would be without their natural teeth.”

DEN.

THE

Fig. 3.-The 1:316, 1951).

CONDYLE

direction

of

force

with

different

occlusal

patterns.

(From

Boswell,

J.

Paos.

PATH

The merit and reliability of recording the condyle path have been questioned by Kurth I9 Craddock 2o Owen 21 and others. To test the immutability of constancy of the co;dyle path, l&rth mabe four tracings of mandibular movement under varied conditions in a patient with natural dentition. The first tracing was made with the patient gliding upon the inclined planes of the natural teeth, and the others, by using a central bearing point functioning successively against flat, convex, and cocave plates with the teeth out of contact. Since all four tracings appeared to be different. Kurthl” contended the condyle path was not constant and there was no value in recording it. Trapozzanoz2 questioned Kurth’s interpretation. He drew a common base line to these tracings and declared the mean path to be almost identical in all cases (Fig. 4). The distortions in the tracings could have been the result of the mandible rotating to a greater or lesser degree as the central bearing point functioned against the variously shaped contacting surfaces. Moreover, the necessarily eccentric position of the central bearing point might be responsible for these distortions.

.\ccordiiig to l’osselt,2’i “It 1~5 Len ~1~0~11tllat sagittal condyle tracings al-( identical regardless of whether intraoral guidances arc flat or curved or when gliding nlvvements are carried out with tooth to tooth ro~itact.”

KurthI” performed similar experiments to check the validity of lateral checkbites (interocclusal records). \Vorking with the tripod, he found he could obtain different lateral “checkbites” for the same individual if he changed the plate, against which the central bearing point functioned, from a flat one to a concave one. The value and reliability of lateral “checkbites” were therefore questioned. The character of lateral movement varies at different heights. Lateral interocclusal records are accurate at the point of occlusal contact. Practically, the use of a central bearing point may introduce inaccuracies because its necessarily eccentric position may induce a tipping or shunting of the bases with a resultant failure to equalize the pressure. With plaster interocclusal records, it may be difficult for the patient not only to maintain the position recorded for the time required for the plaster to set but also to exercise the same degree of biting pressure every time.

TOOTH COMTACT

Fig. 4.-The mean average path of the condyle Trapozzano, J. PROS.DEN. 5: 775, 1955).

FLAT

tracings

PLANE

obtained

by Kurth.

(Modified

from

As a result of his observations, Kurthl” disregards incisal and condylar controls, ignores eccentric balance, and employs nonanatomic teeth set with a reverse curve. Pantographing mandibular movements more accurately record the lateral and protrusive paths, but this procedure entails the use of special equipment and a complex articulator. THE

HINGE

AXIS

The hinge axis, the method of locating it, and the procedure for transferring the record to a suitable instrument are the cause of frequent debates.

36

FRIEDMAN

Fig. 5.-This figure indicates the importance of obtaining centric records as close to the desired occlusal position as possible without cusp interference. It also shows the great discrepancy in the arc of closure if the centric relation record has been obtained several millimeters open from the normal occlusal contact position and the exact axis not obtained. (From Schuyler, J. PROS.DEN. 3:778, 1953.)

Trapozzano and Lazzari2” reported that in 57.2 per cent of the subjects investigated, more than one condylar hinge axis point was located on either one of both sides. These findings, in their opinion, made the high degree of infallibility attributed to hinge axis points seriously questionable. Koski25 stated, “Mechanical constructions based on the hypothesis of a fixed axis are unsound. The great variability of mandibular movements and the location of the axis hardly can be reproduced by a man-made mechanical device.” Lauritzen and Bodner26 studied the extent of variation in positions of actual hinge axis points from arbitrarily marked hinge axis points. These findings revealed only 33 per cent of the actual hinge axis points to be within a 5.0 mm. radius of the arbitrary point. It was concluded, therefore, that the accurate location of the true hinge axis points should be determined. The greater accuracy of the kinematic axis is unquestioned. In complete denture prosthesis, however, tissue resiliency and the difficulty of stabilizing the lower recording base favors the choice of the arbitrary axis. Opinions vary on the choice of the arbitrary axis. In Beck’s27 investigation, the Bergstrom point, which is measured 10 mm. anteriorly from the center of a sphere inserted into the meatus and recorded on a line 7 mm. below the Frankfort horizontal plane, came closest to the kinematic axis.

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For the correct arc of closure, it is important, and especially so when utilizing the arbitrary axis, that the wax interocclusal record be of a minimum thickness (Fig. 5). In some techniques, the vertical dimension of occlusion (the vertical relation) and the centric relation are recorded by a swallowing procedure. With this method there is no assurance against overclosure. BrewerZ8 reports gross inconsistency in the vertical dimension so obtained. Downs,2g however, claims favorable results in using Shanahan’s30 technique. Since the mandibular position in swallowing may be forward of the posterior terminal hinge position, the true centric relation may not have been recorded. Failure to incorporate the true centric relation in the occlusion will produce an anteroposterior churning of the dentures that will traumatize the underlying support, jeopardize retention and stability, and interfere with mastication. Young31 stated, “Personally in over forty years I have had only one patient who had to use an acquired centric relation, thus so-called true centric relation is necessary in all instances unless nonanatomic teeth are used.” THE

GOTHIC

ARCH

Although the Gothic arch (needle point) tracing is a valuable aid, its infallibility and accuracy are frequently mentioned and as constituting the best available means of ascertaining the centric relation. Granger32 stated, “. . . the apex of the Gothic arch is not a reliable guide to centric relation. . . . It was shown that rarely does the Gothic arch present a sharp apex. It does, however, have one value. It can be used to trace the movement of the center of rotation across the fossa in lateral excursion. In order to do that accurately, it is necessary to have two Gothic arch tracings, one on each side of the mandible.” Hughes and Regli 33 observed that a sharp Gothic arch (needle point) tracing may be obtained with the condyles in more than one location in the glenoid fossae. When using a central bearing point for patients with prognathic or orthognathic occlusions, it is difficult, if not impossible, to secure equalization of pressure. THE

CENTRIC

RELATION

RECORD

Wax interocclusal records, as suggested by Schuyler34 are my procedure of choice for recording centric relation. The interocclusal record should be of minimum thickness, present shallow, uniform indentations without perforations of the wax (Fig. 6). THE

COEFFICIENT

OF FRICTION

A pattern of occlusion is suggested wherein porcelain teeth are set up in the upper denture and acrylic resin teeth in the lower denture. The advantage claimed is that the coefficient of friction is greater between two similar substances than two dissimilar materials, thus the use of the different materials reduces the amount of wear. Although some ensuing amount of wear must occur with a consequent

J. Pros. Den. Jan..Feb., 1961

FRIEDMAN

38

Fig. 6.-The wax interocclusal uniform indentations.

record should have a minimum

thickness

and present shallow,

reduction in efficiency, this arrangement would seem to be of advantage in immediate complete upper and lower dentures, because of the relative ease in adjusting the occlusal table in the event of rapid, premature, or uneven settling of the bases. BALANCED

AND NONBALANCED

OCCLUSION

The neutrocentric concept35 repudiates any possibility of eccentric balance. Nonanatomic teeth are set to a flat pattern of occlusion. All inclines of all teeth of all forms and arrangements are rejected. In transographics, the need for eccentric balancing contacts is ignored since balancing contacts are considered to be outside of the functional range. Sears3s wrote, “Whatever validity there may be to the argument of ‘enter bolus, exit balance’ carefully conducted tests show that dentures can be made more satisfactory by balancing the occlusion in all functional jaw relations.” Sears37 has stressed the need for mandibular equilibration prior to occlusal equilibration in patients manifesting temporomandibular joint disturbances generally caused by faulty denture construction, incorrect centric occlusion, or settling of dentures. IDEALS OF OCCLUSION

Schuyler3s published certain ideals of occlusion. A procedure that basically conforms to these criteria should render very adequate service. The thirty-three degree tooth modified to the patiellt’s individual functional requirements will fulfill these objectives in most patients. In the study of the influence of occlusal schemes on muscular activity, Hickey and his associates3Q state, “The reduced activity of the anatomic occlusion during the mastication of peanuts and carrots occurs because the anatomic tooth simply penetrates and breaks up the food with less force than the nonanatomic or semianatomic occlusions.”

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Ilouclieri” statd, “Cusp tretli lmbvitlc ;I rcsistaiicc to the rot&u of deiiturcs iti relation to each other and in relation to the 1)ases \\-liich flat cusp teeth do plot. The intertligitating cusps on the working side l)royide 1leutralizing inclilie plaii~ contacts kvhich tend to prevent rotation of the tlenturc 1~~s. T’ressure on x l&ncing ramp or inclines tends to make the lower denture rotate to the distal on tlic balancing side and tends to rotate the upper denture to the mesial on the balancing side.” Should the upper molar contact the lower second molar in the eccentric positions prior to anterior contact the lower denture might be dislodged. THE

SEMI-ADJUSTABLE

ARTICULATOR

In setting the articulator controls, a zero, or near zero, incisal guidance is preferred for most patients. In cases in nhich esthetic requirements and adequate tooth visibility are prime consiclerations, a steeper incisal guidance is indicated and, at times, to the point of sacrificing protrusive balance. Lateral balance can be achieved by a slight shortening of the upper and lower cuspids and/or suitable horizontal overlap. The condylar guidance is furnished by the patient’s interocclusal wax record. Regarding eccentric records, SearsJ1 wrote, “Our most important eccentric record is that of the mandible in protrusion. We can make all of the necessary articulator adjustments with it. To obtain the greatest precision for adjusting an articulator, it would be necessary to make right and left relation records to set the left and right condylar elements independently of their settings for protrusion. But for practical purposes in denture construction the right condyle follows the same downward and forward path during left lateral relation as it does during protrusion even though the two paths are not actually indentical.” Schuyler42 states, “In my experience I have never known an arbitrary horizontal Bennett movement as is common to most of our semiadjustable articulating instruments to have caused a functional disturbance in the temporomandibular joint.” According to Beck, 43 the possibility of incorporating multiple errors also exists with articulators of complex designs due to the increased number of measurements and adjustments used in such instruments. SELECTIVE

GRINDING

All dentures, after processing and prior to separation from their casts, are returned to their original mountings on the instrument for the elimination of prematurities (interceptive or deflective occlusal contacts) in the centric and eccentric positions. Upon insertion, a new centric r?lation record is made and the occlusion is rechecked on the instrument. The selective grinding44 is carried out in accordance with Schuyler’s38 technique. Schuyler 46 also suggests advancing the mandibular member of the instrument by using a strip of tinfoil, 0.5 to 0.75 mm. thick, between the condylar element and its stop in order to provide greater comfort and anteroposterior freedom in the occlusion. The dentures are finished at this advanced position and then milled-in to the first position. Payne4s suggests opening lip the central fossae of the anatomic lower posterior

40

J. Pros. Den. Jan..Feb., 1963

FRIEDMAN

teeth and grinding down the tips of the buccal cusps of both upper and lower teeth in order to unlock the mesiodistal interference. The slight widening of the central fossae compensates for any minor changes in the vertical dimension that may subsequently occur with dentures resting on a resilient foundation without introducing cuspal disharmonies and allows for an!’ minor advanced mandibular position in swallowing. In some tecniques, the elimination of prematurities (deflective occlusal contacts) after processing is carried out directly in the mouth and with or without a controlled device such as an intraoral bearing device. Shanahan’s”? technique involves the use of thirty gauge wax for the detection and elimination of centric and eccentric deflective occlusal contacts carried out directly in the mouth.

Fig. 7.-Hardy’s

Vitallium

occlusal inserts.

Even with the utmost care and precision, any complete grinding technique performed entirely in the mouth incurs the risk and possibility of grinding the teeth out of occlusion. In an evaluation of the mouth as an articulator, Swenson48 stated, “The mouth does not afford visibility to properly position and examine the teeth; the resiliency of the tissue precludes constant equalization of pressure in various denture positions; the denture bases shift under incline plane stress without the operator being aware of it, whereas on a stone cast this cannot happen ; the temporomandibular joint can be malpositioned since no repeated checks are possible ; and lastly, an exact centric [relation record] can be obtained and transferred to the articulator which assures an exact and correct starting point for each movement. This correct starting point, in the mouth is not controllable.” SUMMARY

AND CONCLUSIONS

The occlusal plane should be in a harmonious

relationship

with the tongue

s%E-r Y

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41

position and function. The occlusal level should be more or less parallel to the mean foundation plane. In the so-called average or normal relationship with normal contours and favorable denture space, the greater efficiency of cusp teeth is preferred and in the manner previously described. Hickey, Boucher, and Woelfellg state, “No data have shown that anatomic teeth cause more soreness or ridge resorption than other pose terior tooth forms.” Moses,50 in his investigations of the skulls of animals and humans, uncovered a law which states, “Under normal conditions a natural posterior tooth inclines in the direction of the ridge opposing it.” In conformity with this law and for greater stabilization of the lower denture, a reverse pattern of occlusion is desirable where the maxillary arch is uniformly broader than the mandible. Nonanatomic teeth are used except in the second molar region where the curve is reversed in order to achieve a balanced occlusion. In the presence of a narrow maxillary arch and a broader mandible, the Avery curve is contraindicated. The nonanatomic teeth of choice are Hardy’s ‘C:itallium occlusal inserts for the upper denture (Fig. 7), and for the lower denture, a nonanatomic tooth, such as the Rational* is used. A balanced occlusion can be obtained by correctly inclining the lower second molar or through the use of a balancing ramp (Figs. 8 to 13). Nonanatomic teeth are preferred under the following circumstances : (1) in abnormal closure patterns, whether they be the result of muscle imbalance, trauma, pathosis, neuromuscular disturbances of lack of neuromuscular coordination, not uncommon among the aged ; (2) in marked horizontal tissue mobility almost devoid of any firm ridge foundation ; (3) in the presence of posterior, extremely yielding displaceable mucosa ; and (4) in multilated, tortuous ridges combined with an excessive denture space. In these patients, the objective is to render the forces more nearly vertical

Fig. 8. Fig. Fig.

Fig. 9.

S.-Centric occlusion. 9.-Protrusive occlusion.

*The Dentists

Supply Company of New York, York, Pennsylvania.

FRIEDMAN

Fig. 10. Fig. lO.-Right Fig. Il.-Right

Fig. 11.

working occlusion. balancing occlusion.

Fig. 13.

Fig. 12. Fig. l2.-Left Fig. IS.-Left

working occlusion. balancing occlusion.

to the ridges, to control possible tipping, tilting, skidding, or horizontal shifting of the denture bases due to eccentric cusp incline contacts in mandibular closure. The use of a mandibular cast gold base will aid in the realization of the objective. My final thought is best expressed in the words of John Milton : “There is no learned man but will confess he hath much profited by reading controversies; his senses awakened, his judgment sharpened, and the truth which he holds more firmly established. In logic they teach that contraries laid together more evidently appear; and controversy being permitted, falsehood will appear more false and truth more true.” REFERENCES 1. Wright,

C. R., Concept, 2. Wright, C. R., Concept,

Swartz, W. Ann Arbor, Swartz, W. Ann Arbor,

H., and Godwin, Mich., 1961, The H., and Godwin, Mich., 1961, The

W. C.: Mandibular Denture Overbeck Co., pp. 18-23. W. C.: Mandibular Denture Overbeck Co., pp. 31-36.

Stability;

A New

Stability;

A New

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3. Pound,

E.: Recapturing Esthetic Tooth Position in the Edentulous Patient, J.A.D.A. 55:189-190, 1957. 4. DeVan, M. M.: An Analysis of Stress Counteraction on the Part of Alveolar Bone \\‘ith a View to its Preservation. Dental Cosmos 77:169. 1935. I.5 Stan&cry, C. J.: Guidance Manual for the Tripod Technic, 1952, pp. 8-9. (Published privately.) B., Hoffman, G. M., and Hendron, J. A. : The Physiology of the Stomatognathic 6. Jankelson, System, J.A.D.A. 46:375-386,. 1953. to Traumatic Occlusion, J. PROS. DES. 11:708-715, 7. Schuyler, C. H.: Factors Contributmg 1961 __-..

8. Yurkstas, A. A., and Emerson, W. H. : A Study of Tooth Contact During Mastication With Artificial Dentures, J. PROS. DEN. 4:168-174, 1954. 9. Anderson, D. J.. and Picton, D. C. A.: Tooth Contact During Chewing, J. D. lies. 36: 21-26, 1957. of Miniaturized Electronic Devices to the 10. Brewer, A. i\., and Hudson, D. C.: Application Study of Tooth Contact in Complete Dentures. J. PROS. DF.x. 11:62-72, 1961. 11. Woelfel, J. B., Hickey, J. C., and Allison, M. L.: Effect of Posterior Tooth Form on Jaw and Denture Movement, J. PROS. DEN. 12:922-939. 1962. Occlusion in Relation to Complete Dentures, J. PKOS. DEN. 12. Boswell, J. V.: Practical 1:307-321,1951. Problem in Mechanics, J.A.D.A. 24:1303-1318, 13. Pleasure, M. ‘4. : Prosthetic Occlusioll--A 1937. J. PROS. DEX. 2:343, 1952. 14. Moses, C. H. : Studies in Articulation, 15. Hickey. J. C., Woelfel, J. B, Allison. M. L.. and Boucher, C. 0.: Influence of Occlusal Schemes on the Muscular Activity of Edentulous Patients, J. PROS. DEX. 13:444451, 1963. Jaw Relations and Occlusion of Complete Dentures, J. 16. Shanallan, T. E. J.: Physiolocic PROS. DEN. 5:319-324,.1955. 17. ShanaF4; T’.& J. : The Individual Occlusal Curvature and Occlusion, J. PROS. DEN. 8 :234edited by L. M. S. Minor, St. Louis, 1951, The C. V. 18. O’Rourke: J. T:: In Oral Physiology, Mosby Co., p. 87. Kurth, L. E. : Balanced Occlusion, J. PROS. DEN. 4:150-167, 1954. 2:: Craddock, F. W.: The Accuracy and Practical Value of Records of Condyle Path Inclination, J.A.D.A. 38:697-709, 1949. 36:284-290, 21. Owen, ltZ.8B.: The Condyle Path: Its Limited Value in Occlusion, J.A.D.A. 22. TrapozzzFi9yj 23. Possel;oy.;

R.: An Analysis $ysioIogy

of Current

of Occlusion

Concepts of Occlusion,

and Rehabilitation,

Philadelphia,

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