DENTAL INSTRUMENTATION

The History of Articulators: A CriticalHistory of Articulators Based on“Geometric” Theories of MandibularMovement. Part IV: Needles, Wadsworth,and a Look at Some Who FollowedEdgar N. Starcke, DDS

AS WAS discussed in Part III of this series, JohnNeedles was an early and enthusiastic propo-

nent of the Monson “spherical” theory. In August1921, Needles read a paper before the NationalSociety of Denture Prosthetists in Milwaukee, thepurpose of which was “to demonstrate the correct-ness of the theory that the teeth in normal occlu-sion lie upon the surface of a sphere as advocated byGeorge S. Monson or more generally that the twosides lie upon the surface of concentric spheres.”1

But even by this time, Needles was beginning toquestion Monson’s theory in its purist form. “If thistheory is true,” Needles said, “there is a transverseaxis through the head of the condyles about whichthe opening and closing motion takes place.”1 Nee-dles’ first articulator embodied this idea—that is, auniversal joint (“balancer”) design with an incisalguidance mechanism.2

By the following year, Needles’ beliefs hadchanged significantly. In August 1922, he read asecond paper before the National Society of Den-ture Prosthetists in Los Angeles. He prefaced hisremarks with the statement that “any theory mustbe subject to constant change and modification,disregarding those portions which are shown to beuntrue and incorporating those facts which thefuture develops.” Offering his present views onsome of the facts and theories of mandibular move-ment, Needles announced that “further study andexperiments have convinced me that some of myformer views are untenable.”3 Presumably, the onlyconcept relating to the Monson theory that Needlesretained in practice was the spherically contouredocclusion rims that he created for the “Needles

chew-in” method of recording jaw relations. Hissecond articulator was an adjustable condylar guideinstrument that incorporated his unique incisalguide (gothic arch) control mechanism. His “chew-in” technique was used to adjust the articulatorcontrols (Fig 1).4

Having reviewed these events, it is interesting tonote that Needles was apparently one to keep all ofhis bases covered. In 1957, Needles patented whathe described as an “improved form” of his 1921articulator5 because, as he stated, “a device of thischaracter . . . found extensive use in the dental pro-fession.” Needles claimed that this articulator (Fig2) would be “more easily susceptible of use by adentist or dental assistant who lacks the high de-gree of skill which has been required heretofore forthe successful use of previous articulators.”5

It was also in 1921 that Rudolph L Hanaustepped into the ring and struck a blow for “back tobasics.” In a paper read before the National Societyof Denture Prosthetists in Milwaukee, Hanau asked

Copyright © 2003 by The American College of Prosthodontists1059-941X/03/1201-0011$30.00/0doi:10.1053/jpro.2003.10

Figure 1. John Needles’ second articulator, 1922 (notpatented). Needles believed that this instrument pro-vided perfect adaptation with correct adjustment of thecondylar slopes. (Reprinted from Nichols, p 165.4)

51Journal of Prosthodontics, Vol 12, No 1 (March), 2003: pp 51-62

what he considered the “capital” question: “Is itpermissible to use a non-adjustable mechanismbased on averages, or should we have an adjustableapparatus to comply with the anatomical conditionsand with the technical selections?”6 He introducedhis Hanau “model C” articulator (Fig 3) and pre-sented his recent investigations into mandibularmovement, explaining that his conclusions were

“from the viewpoint of dental engineering.” * Hanaubelieved that the Hall and Monson theories weremisinterpretations of masticatory movements asapplied to articulators and said that he had come tothe “final conclusion” that it was absolutely neces-sary to adjust an articulator to comply with “givenindividual requirements.”6 Hanau’s presentationwas well received, but was certainly no knockoutpunch. His articulator, although based on generally

*The “model C” was the third version of this articulator andwas the only one offered for sale to the profession. Hanauapplied for a patent on the first version, the “model A” articu-lator, in February 1921. The patent was not issued until June1926.

Figure 2. Needles’ improved and simplified version ofhis 1921 articulator. Needles claimed that his first modelwas very successful but difficult to use. This was anattempt to provide a simpler model for the less-skilleddentist. (Reprinted from the 1957 US Patent.5)

Figure 3. The Hanau model “C” articulator. This was Hanau’s third design and the only one offered commercially. Itwas never patented. (Reprinted from a commercial advertisement in Dental Summary 1921;41:547.)

Figure 4. Dayton Campbell’s incisal guide attachmentapplied to the Gysi Simplex articulator. This modified theSimplex with bilateral incisal angles of 45 degrees and ahorizontal protrusive path. (Reprinted from Campbell, p206.10)

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accepted theory, proved to be impractical because itwas functionally complicated and cumbersome tohandle. Like Needles’ first articulator, it had a typeof “universal joint” mechanism, but it also embod-

ied many other adjustment features. Hanau recom-mended a technique that used a wax “check-bite”procedure and orientation of the casts with theSnow facebow. Obviously, by this time, neither thefacebow nor the adjusting articulator controls with“check bites” were exactly new ideas. So, althoughHanau’s concepts had merit, his “model C” articu-lator was not accepted by the profession.

A review of geometric theories of mandibularmovement would not be complete without notingDayton Dunbar Campbell’s viewpoint on the sub-ject. During this period, Campbell attempted to sellthe profession on the “floating condyle” theory.Campbell argued that for an articulator to accu-rately reproduce mandibular movements, a cuspheight of 45 degrees should be used as the guidancecontrol, and condylar guidance should be ignored.7

Apparently, Campbell adopted a component of Ru-pert Hall’s conical theory—the idea that the max-

Figure 5. Dayton Campbell’s “barn door hinge” articulator.This device could be the origin of the association of barn doorhinges with his name. (Reprinted from Campbell, p 223.11)

Figure 6. (A) Frank Wadsworth’s first articulator, 1919. The unique feature is the incisal guide table. The adjustablelateral wings (19 and 20) have 3 surfaces (plane, concave, and convex) on which the incisal pin can traverse. (Reprintedfrom the 1919 US patent.6) (B) A detail of the condylar mechanism. The condylar guides are fixed at about 45 degrees,and movement of condylar pins is restricted by springs. The only possible adjustment of the “temporal mandibulararticulation” device is to change the position of the condylar pins with the thumbscrew. Incidentally, this model did notfeature the 3 surface incisal guide table. (From the collection of Waterpik Technologies, Ft. Collins, CO.)

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illary first bicuspid (at 45 degrees) would producethe greatest efficiency in mastication8 In 1919,Campbell patented a device9 for modifying certainpopular contemporary articulators with a fixed in-cisal guide of 45 degrees; Figure 4 shows this deviceapplied to a Gysi Simplex articulator.

The device was also used to modify the Kerrarticulator and the Snow “Acme” articulator.Campbell rejected Monson and Hall’s ideas thatthe mandible moved around a fixed rotation center,instead holding that multiple centers exist. He

claimed that satisfactory dentures could be easilymade with either of their articulators because ofthe universal joint features.10 To demonstrate thesimplicity with which the mechanism of the univer-sal joint can be applied, Campbell fabricated anarticulator (after Hall’s “Automatic Anatomic” de-sign) using 2 barn door hinges, the bottoms of twocuring flasks, a cabinet door hinge for the incisalguide table,and a bolt for the incisal pin (Fig 5).He constructed a set of complete dentures usingthis device, hen mounted the completed den-

Figure 7. (A) The Wadsworth articulator, c. 1924 (not patented). Wadsworth’s best-known model, this featured thenew “centering plate” for projecting the occlusal curves, an intercondylar distance-adjustment mechanism, and a curvedcondylar path. (Reprinted from Thomson, p 113.16) (B, C, D, and E) A series of drawings depicting the procedure fordetermining the “Wadsworth triangle” and projecting the basic or compensating curve using dividers. (B) Measuringthe length of the mandible from the median incisor point to the condylar rod. (C and D) Determining the apex of theWadsworth triangle by scribing arcs from the medial incisor point and from the condyle. (E) Projecting the basic orcompensating curve on the occlusion rims. (Reprinted from Thomson, p 113.16)

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tures on both the Hall and Monson articulators.“The masticatory movements were the same,” hesaid, “since these movements are pre-determinedby the cusps.”11 Could this paper, presented to theOhio State Dental Society in December 1920, ex-plain why Dayton Dunbar Campbell’s name is fre-quently associated with the “barn door hinge”?

The Contributions ofFrank M. Wadsworth

Figure 6A shows patent drawings for Frank Wads-worth’s first effort in articulator design.12 Duringthis period, Wadsworth had expressed little con-cern over the emerging “geometric” theory contro-versy, regarding incisal control as the primary fac-tor in reproducing mandibular movement in anarticulator. In the patent letter, he explained thatthe main object of his invention was “to provide ina dental device means for establishing the cuspplanes [inclines] in partial dentures.”12 His otherobjectives were to provide the means to reproducethe action in and adjust the parts of “the devicerepresenting the temporal mandibular articula-tion.”12 This claim is surprising, considering thathis articulator is a fixed condylar guide design (Fig6B). Wadsworth’s unique incisal guide mechanismis noteworthy because he designed the lateral guideplates with 3 distinct surface contour variations:plane line, concave, and convex.

Although a proponent of Monson’s “spherical”theory, Frank Wadsworth soon discovered the fal-

lacy of designing an articulator based on bilateralsymmetry of the condyles. Wadsworth’s second andthird articulators (c. 1921 and 1924) were verysimilar in design and embodied his ideas for mod-ifying the Monson theory to reflect the individualrequirements of the patient. Both were nonarconadjustable condylar guide instruments (Fig 7A). Thecondyle mechanism generally resembled the con-temporary Hanau “model H” except for a slightlycurved condylar path. Wadsworth also included theadjustable intercondylar distance feature in thesearticulators. Like his first articulator, his secondarticulator had an incisal guide assembly with afixed horizontal protrusive path, but simplified bylateral guide plates with only 1 (plane line) surface.In addition, Wadsworth introduced the concept ofthe “third point of reference” by adapting his “T-attachment” to the Snow facebow when mountingthe casts in the articulator.13 † The vertical positionof the casts was determined by applying the “T-attachment” to the “naso-optic-condylar” triangle.The intercondylar distance was determined whenthe facebow was adjusted to the patient by measur-ing the distance between the condylar rods andsubtracting ½ inch from each side.14

Wadsworth’s innovation for the purpose of ac-commodating condylar asymmetry was to applywhat he called the “centering plate” to project

†Wadsworth later designed his own facebow based onGeorge Snow’s principles.

Figure 8. Using dividers with a knife tip for trimmingocclusion rims. (Reprinted from Nichols, p 173.4)

Figure 9. Rupert Hall’s illustration of the Monson-Wadsworth curve (a-a) and a “practical” curve (b-b) ap-plied to mounted edentulous casts, demonstrating why hebelieved that the Monson-Wadsworth curve was neitherbasic nor practical. Did Hall consider the curve that wasprojected in his conical theory to be practical? (Reprintedfrom Hall, p 26.8)

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occlusal curves (Fig 7A). Monson, of course, was thefirst to project the occlusal curve (also known as“Christensen’s curve”) from a common center of asphere by means of dividers. But Wadsworth wasthe first to establish an individual center for eachcondyle using the centering plate and dividers.14

Originally, the centering plate was round and hadrecessed areas on both sides. The recesses werefilled flush with modeling compound for determin-ing the apex of Wadsworth’s variable equilateraltriangle.15

The procedure for applying the centering plateto determine the curve of occlusion is diagrammat-ically illustrated in Hamish Thomson’s text16 (Fig7B, C, D, and E). Wadsworth himself15 describedthe Wadsworth triangle as essentially the Bonwilltriangle but with the size determined according tothe requirements of each individual. The length of

the mandible is determined with the dividers bymeasuring the distance from the condyle to themedian incisor point on the occlusion rims. Thisthen becomes the base of the triangle on that side.With this fixed length, 1 divider tip is placed on thecondyle rod, and the other tip is made to scribe anarc on the centering plate. The dividers are thenrotated from the median incisor point, with theother point likewise scribing an arc on the centeringplate. The point of intersection is the apex of theWadsworth triangle and the center of a sphere. Byplacing 1 point of the dividers at this center, theother point can be used to scribe the “basic” or“compensating ” curve on the lower occlusion rimfrom the median incisor point extending posteriorlytoward the condyle. Figure 8 illustrates how thespecial dividers are used to trim the lower occlusionrim.15 Wadsworth further refined the occlusal curveand thereby adjusted the inclination of the condylarguides by applying the functionally generated path

Figure 10. The Ralph articulator, 1930. After the verti-cal position of the maxillary rim is initially determinedwith a facebow (18), the gauge (58) is moved downvertically in a 4-inch arc to locate the horizontal positionof the mesial incisal point (24). The carving tool (77) issuspended from the gauge at (79), whereby the blade(81) is used for carving the curve of the occlusion rims.(Reprinted from the 1930 US Patent.19)

Figure 11. The Chott articulator, 1935. The maxillaryand mandibular rims are shaped to conform to arcsrepresenting the “curve of Spee.” The templates aresupported by 3 adjustable spring-loaded rods for placingthe rims in the proper position. (Reprinted from the 1935US patent.20)

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method described by A.H. Paterson of Baltimore inthe 1920s.17 This technique was later modified andpopularized by F.S. Meyer.18

Frank Wadsworth’s untimely death in April 1925brought an end to a promising career and to hisindefatigable efforts in the development of a systemfor complete denture construction. Without his ad-vocacy, the Wadsworth system could not have beensustained, even with the support and financial back-ing of the S.S. White Company.

By 1930, Rupert Hall, who had abandoned hisconical theory for his tripod concept and the 3-di-mensional articulator, had become an outspokencritic of Wadsworth. “Neither Monson’s nor Wads-worth’s curves,” he stated, “are basic, as projected,because it is not possible to apply these curves in allcases . . . the relation of the ridges to these curvesdoes not permit placement of the teeth . . . .”8 Hallillustrated this point diagrammatically by compar-ing the Monson-Wadsworth curve and a “practical”curve as applied to mounted edentulous casts (Fig9). Line a-a represents the Monson or Wadsworth

curve that often intersects the posterior region ofthe maxilla. Line b-b represents a curve that takesthe relationship of the ridges into practical consid-eration.

Some Other Novel Devices ReflectingGeometric Principles

In 1930, Edward D. Ralph of Long Island, NewYork, in an attempt to emulate the methods ofNeedles and Wadsworth, patented an articulator(Fig 10) that featured a combined gauge (58) fordetermining the horizontal position (mesial incisalpoint) of the maxillary wax rim and a carving tool(75, 77) with an adjustable blade (81) for cuttingthe occlusal surface of the maxillary wax rim toconform to the “curve of Spee.”19 Ralph pointed outthat the centers of the curves of Spee for both theright and left sides are determined individuallybecause they rarely coincide, that is, the pointwhere gauge and the carving tool are joined (79).These centers (ie, the apices of the “Bonwill trian-

Figure 12. The Fournet “Dual Check” articulator, 1942. The (A) maxillary and (B) mandibular spherical templates areused for determining the curve of the occlusion rims, as a guide for setting the teeth and for “grinding in” the occlusionto predetermined arcs. (From the collection of the University of Texas at Houston Dental Branch.)

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gles”) are found to be at a point equidistant fromthe mesioincisal point on the wax rim and thecondyle (79). The carving tool is suspended fromthese centers. Initially, the vertical position of themaxillary rim is determined by a Snow-type face-bow and is supported by 4 adjustable spring-loaded“yielding plungers.” (66, 67)

In 1935, Edward L. Chott of Chicago received apatent20 for his “Dental Aligning and Testing De-vice” and articulator (Fig 11). Chott described hisarticulator as a “Stephan-type” that was “wellknown to the profession.”20 The testing device wasa triangular-shaped template with a “curvaturesimilar to that of a sphere having a 4-inch radius”for setting the occlusal curves for either the man-dibular or maxillary denture teeth.20 The templatewas adjusted horizontally and vertically by means of3 spring-loaded rods (or were they “yielding plung-ers?”).

In about 1935, Sidney C. Fournet of New Or-leans introduced his philosophy for constructingcomplete dentures. His method focused on an im-pression technique21 and a novel approach to estab-lishing denture occlusal curves using the Fournet“Dual Check” articulator.22 The “Dual Check,” pat-ented in 1942, was a simple-hinge instrument withspherical templates mounted on vertical axles. Itwas intended for mounting casts, setting teeth, andgrinding the teeth to conform to arcs of selectedradii (Fig 12). The device incorporated a convextemplate for setting the mandibular teeth and aconcave template for setting the maxillary teeth.The templates were converted into grinding devicesby applying sandpaper discs to the surfaces androtating them by turning the hand-crank. Or, asSidney Fournet himself put it, “the invention con-templates the provision of a novel dental articulator

Figure 13. The P-M instrument, 1960. This is a photo-graph of the original Pankey-Mann instrument manufac-tured by Jelenko (Armonk, NY). It was used primarily fordetermining the mandibular occlusal curve. (From thecollection of the University of Texas at Houston DentalBranch.)

Figure 14. From the patent drawings of the P-M instru-ment. This device was designed to develop the mandib-ular occlusion to conform to Monson’s spherical princi-ples. To relate the occlusal plane to the fixed axis ofrotation (132), a mandibular facebow (117) and dividers(128) were used to secure the mandibular cast on theadjustable stage (28) (Reprinted from the 1960 USPatent.14)

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which comprehends opposed model mounts whichare relatively adjustable toward and away from oneanother, one of such mounts being journalled in afixed bearing whereby it can be rotated and saidmount also having attachment means for a spher-ically surfaced grinding element of predeterminedradius.”22 What else can be said?

In the late 1950s, Lindsey D. Pankey and ArvinW. Mann of Florida introduced their philosophy forthe oral rehabilitation of natural dentition23,24

along with their technique and articulator (P-MInstrument)25 (Fig 13). The original Pankey-Mannsystem was based on a combination of Monson’sspherical theory and F.S. Meyer’s functionally gen-erated path (“chew-in”) technique. The treatmentobjective was to achieve bilateral balance in allmandibular excursions, an idea that apparently hadits origins in the concept of complete denture oc-clusion.26

The Pankey-Mann system comprised 2 basic re-storative phases. The first phase involved restora-

tion of the mandibular posterior teeth as near aspossible to the “ideal” 4-inch-radius sphere. For thisphase, a mandibular facebow and dividers wereused to position the mandibular cast and project anarc from a fixed point to construct a template forrestoring the mandibular teeth (Fig 14). The sec-ond phase involved restoring the maxillary poste-rior teeth to the occlusal curve established in themandibular arch using Meyer’s functional “chew-in” procedure but using anterior tooth guidanceduring the procedure.27

The Pankey-Mann system began to evolve underthe influence of Clyde Schuyler,28-30 who introducedseveral concepts that became integral componentsof the system. Balancing side contacts, known to bedestructive to natural dentition, were eliminated.Much more importance was placed on incisal guid-ance, and the idea was introduced that instead of aprecise static point of contact in centric occlusion,there exists a limited area of contact. Thus theterms “long centric” and “freedom in centric” be-

Figure 15. (A) A Hanau “University Series” 130-1 articulator with the Broaderick Occlusal Plane Analyzer and theSchuyler incisal table as might have been used in the P-M S procedures. (From the collection of the University of TexasDental Branch.) (B) A schematic drawing of the Hanau incisal table with Schuyler’s adjustable center post to providea limited horizontal “freedom in centric” occlusion. (Reprinted from Schuyler, p 1022.30)

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came part of the vernacular. Later, 1 of the Hanaumodel “H” series or “University” series articulatorsand a basic Hanau facebow were adopted for thePankey-Mann-Schuyler system (Fig 15A). Accessoriesfor the Hanau articulator included the Schuylerincisal table, featuring a horizontal surface of free-dom by way of an adjustable center post, and theBroaderick occlusal plane analyzer mounted on theupper member and used to locate the commonrotational center from which to scribe occlusalcurves (Fig 15B).

In the last 50 years, numerous articulators havebeen produced (both patented and nonpatented)designed primarily for constructing dentures ac-cording to a geometric principle. Three interestingexamples are instruments designed by Morris Be-resin (1953), Robert M. McMorris (1956), and Ber-nard Jankelson (1960s).

The Beresin articulator was essentially a hinge-type instrument with a unique feature for adjusting

the relationship of the mounted casts. In the patentletter,31 Beresin explains that for his articulator to“simulate with substantial accuracy the arcuatemovement of the mandible . . . the [maxillary andmandibular] elements of the articulator must con-form generally both in structure and in function tothe maxilla and mandible of the human jaw” (Fig16). Therefore, the “upper bow, corresponding to

Figure 16. The Beresin articulator, 1953. The supportrods (104, 100) for the maxillary template and cast holderremain fixed while the adjusting mechanism (52, 54, 62)for the mandibular template and cast holder provides the“functional masticatory movements”—protrusive, retru-sive, and lateral. It can be locked in any desired position.(Reprinted from the 1953 US patent.31)

Figure 17. The McMorris articulator, 1956. This deviceis a “balancer”-type articulator with a mechanism forplasterless mounting. The maxillary cast holder featuresa dual universal joint arrangement (22, 27) with verti-cal (13) and horizontal (18) adjustment capability. (Re-printed from the 1956 US patent.32)

Figure 18. The Jankelson “Terminus Precis” articula-tor, late 1960s. This is essentially a simple hinge devicewith a clear template set to a predetermined curve.(Reprinted from Comito, p 9.33)

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the human maxilla is fixed . . . and the [lower bow]corresponding to the mandible has substantially themovements as are provided by the temporomandib-ular joint . . . i.e., lateral, protrusive-retrusive, andvertical.” Beresin also pointed out that “con-centric spheres of the same radius are the onlycurved surfaces which are capable of [maintain-ing] . . . continuous contact.” Accordingly, the max-illary and mandibular templates permit the “artic-ulation of artificial denture having occlusal surfaceswhich conform to concentric spherical surfaces ofthe same radius, i.e., 31⁄2 to 6 inches.”31

In 1956, Robert McMorris received a patent32 foran articulator that was essentially of the “balancer”type (Fig 17). The maxillary cast holder was at-tached to a universal joint mechanism suspendedfrom a standard that could be adjusted verticallyand horizontally. The mandibular cast holder wasfixed but could be swiveled on its base and adjustedvertically. Both cast holders provided for plasterlessmounting.

In the late 1960s, Bernard Jankelson produced adevice that he called the “Terminus Precis” articu-lator, which he claimed reproduced precise regis-trations obtained by using the “Myo-Monitor” (Fig18). According to Comito,33 the Terminus Precisprovides accuracy for the construction of completedentures as well as in full mouth rehabilitation. Itsolidly holds the vertical height and centric positionwith its unique “double-stop” mechanism. More-over, the occlusal template is also a multipurpose,transparent guide for “see-through” mounting ofthe casts.

. . . And the Tune Lingers OnWilliam Bonwill, Carl Christensen, and GeorgeMonson have unquestionably had a lasting influ-ence on the dental profession’s understanding ofmandibular movement and on the design and use ofarticulators that reflect geometric principles. Eventoday, numerous examples can be cited of dentureteeth and articulator manufacturers offering spher-ical solutions to denture occlusion, either as anintegral part of their basic technique or as analternative method, using accessories to their artic-ulator. At the present time, as an accessory of thePROTAR articulator system, KaVo EWL provides acurved template with a radius of 125 mm for settingdenture teeth (Fig 19). As a part of the IvoclarBiogenic prosthetic technique, the Ortho Plane An-alyzer can be used to fabricate functional occlusionrims (Fig 20).

(More on the History of Articulators in a futureissue of the Journal of Prosthodontics.)

Figure 19. KaVo EWL Protar articulator system curvedocclusal template for complete denture construction.(Reprinted from KaVo EWL, Fig. 5434)

Figure 20. Ivoclar Ortho Plane analyzer (biogenic prosthetic technique). (A) Lateral view. (B) Anterior view. Thistemplate is used to form the occlusion rims and as a guide for setting denture teeth to a predetermined “curve of Spee.”(Reprinted from Ivoclar North America, Figures 7&8.35)

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25. Mann AW, Pankey LD: Articulator With Means to EstablishMandibular Occlusal Fnction. US Patent No 2,930,127.March 9, 1960

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27. Meyer FS: Can the plain line articulator meet all the de-mands of balanced and functional occlusion in all restorativeworks? J Colo Dent Assoc 1938;17:6-16

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