The Evolution of Articulators – Part II

Abstract Articulators are instruments that aimed to reproduce the range of jaw movements. The first instrument designs were attempts to duplicate anatomic relations or reproduce functional movements of the anatomy. They were able to preserve centric position only. More sophisticated articulating instruments evolved as more was learned about the anatomy, mandibular movements, and mechanical principles. Over time, interest for articulators progressed. Articulators became adjustable, and they attempted to reproduce jaw movements of each patient by reproducing the anatomy of temporomandibular joints (TMJ’s) and related structures. Part I of the article has discussed evolution of articulators beginning from the 18th century till 1940. A history of articulators from 1940 till today is discussed in the present article.

In continuation on the history of articulators part I, where the evolution of articulators beginning from the 16 th century was described, the current article discusses the historical aspect of articulators since 1940.
Articulators introduced since 1940 range from the type that maintains a prescribed position, to fully adjustable articulators [1]. By the turn of the 20th century, several investigators have examined the nature of mandibular movements. Therefore, development of articulators has reflected newly discovered or rediscovered principles [2]. Historically, some aspects of jaw movements have been easy to duplicate mechanically on an articulator (hinge movement, relation of the casts to the hinge and inclination of the condylar path). Consequently these features appeared first on the instruments. Other movements have been more difficult to reproduce mechanically, such as Bennett movement in three dimensions, the timing of the Bennett movement, the exact curvature of the condylar path and intercondylar distance. The problems involved in duplicating these movements have been solved by modern instrument design. Through the history, some articulators have been modified and some have not been accepted by the profession and disapeared.
The current article has aimed to describe articulators introduced into the dental practice since 1940 till the present.
An electronic search was performed across the three databases (Science Direct, PubMed and Google Scholar) for relevant citations. Keywords such as articulators, history, and early articulators were used alone or in combination for the search. The option of "related articles" was also utilized. Finally, a search of review articles was performed and the most relevant papers pertaining to the history of articulators were selected.

The Modified Stephen Articulator
The Stephen articulator (Figure 1), as modified in 1940, is a simple hinge joint articulator that has fixed condylar path of 30 degrees. It is similar in design to the 1921 model, except that the upper and lower mounting arms on this model are longer. An adjustable setscrew in the posterior region holds the upper and lower members in the fixed vertical position [1].

The Stephen Articulator Model P
The additional features of the Stephen articulator Model P are incisal pin and vertical height adjustment. Another  [1] Slika 1. Modifikovani artikulator Stephen [1] version of this articulator was manufactured to include a fixed 10 degree incisal guidance [1].

The Fournet Articulator
The Fournet articulator ( Figure 2) was developed around 1940 and distributed by the Dentists' Supply Co. of New York. The Fournet articulator is one-dimension articulator that has no lateral movement. The maxillary cast is positioned horizontally by (1) the two maxillary central incisors, which are oriented aesthetically and rest on Spee curve template anteriorly, and (2) the Cook mounting jig, which fits into the depth of the hamular notch and orients the casts posteriorly [1].

The Johnson-Oglesby Articulators
The Johnson-Oglesby articulator was developed around 1950. It is small, nonadjustable, flexible articulator. The Johnson-Oglesby instrument had limited use, and restorations produced using it sometimes required major adjustments intraorally [1].

The Coble Articulator
The Coble articulator was developed around 1950. by Lucian G. Coble. The Coble articulator maintains centric relation and vertical dimension but does not allow functional movements. It is a hinge articulator in which the maxillary cast is mounted with a mounting jig that corresponds to the occlusal plane. The mandibular cast is positioned with an interocclusal record [1].

The Galetti Articulator
The Galetti articulator ( Figure 3) was first manufactured about 1950. in Italy. It was advertised in this country in the early 1960's and distributed by John O. Luongo. In this articulator, each cast was held mechanically without plaster by two fixed posts anteriorly and one adjustable post posteriorly to each member. The upper member was adjustable by an extendable arm and a universal ball-andsocket joint to achieve the desired relationship of the maxillary to the mandibular cast, which permitted rapid cast mounting. This articulator had fixed condylar path and a vertical stop that was in the posterior region. It did not accept a face-bow [1].

The Pankey-Mann Articulator
The Pankey-Mann articulator ( Figure 4) was developed in 1955. by Lindsey De Pankey and Arvin W. Mann. This articulator consists of a base that holds a platform for the mandibular cast and a vertical post containing two movable assemblies. The first assembly was made up of a horizontal rod that supports the face bow frame and also has centers of rotation for measuring and cutting calibres. A second movable assembly hold the mounted maxillary cast. By using the Pankey-Mann face bow to mount the mandibular cast, and cutting dividers to establish an oc-clusal plane in the mandibular teeth based on the spherical theory, the entire occlusal plane was engineered before tooth preparation is initiated [1].

The Stuart Articulator
The Stuart articulator ( Figure 5) was developed by Charles E. Stuart in 1955. It was a fully adjustable articulator. The upper member of the articulator had two sets of cams posteriorly on each side that guide truncated spheres located on the lower member. The movable outer cam and sphere on each side controlled all condylar movements except the angle and timing of the Bennett movement, which were controlled by the inner cam and sphere. The articulator settings were programmed using pantographic tracings from the patient [1].  [1] Slika 2. Artikulator Fournet [1] Figure 3. The Galetti Articulator [1] Slika 3. Artikulator Galetti [1] The Hanau Model H2 Series The Hanau Model 96 H2 came out in 1958. The principal feature of this articulator was an increased distance between the upper and lower members from 95 mm to approximately 110 mm. In addition, the orbital indicator was added to the upper member. The H2-XPR, which is one of the models of the H2 series, was introduced in 1958. It had features identical to those of other models in this series, but in addition, it had extendable condylar shafts and retrusive-protrusive adjustment in the condylar element. Some other models of the H2 series are: Model H2-O, with orbital indicator attachment; Model H2-X, with extendable condylar shafts; Model H2-PR, with calibrated adjustments to protrude or retrude condylar balls up to 3 mm.
An adaptation of the Hanau Model H110 articulator, which uses a 0.75 inch lucite shim to increase the condylar post height, was described by Elinchbaugh. He also described the fabrication of a 0.75 inch lucite orbital point guide plane that provided an anterior point of reference level with the condylar axis. This adaptation made the Model H is equivalent to some models of the H2 series [1].

The Dentatus ARL Articulator
The Dentatus ARL articulator ( Figure 6) was first manufactured by A.B.Dentatus of Stockholm, Sweden in 1958. It was a semiadjustable, shaft type articulator with a straight condylar path and a fixed intercondylar distance. In mechanical principle and design it was similar to the Hanau H2 articulator. An adjustable positioning mechanism on the upper member allowed the use of a block that standardizes upper member to lower member, and transfer of casts from one to another articulator while the same relationship was maintained. The Dentatus ARL was a rigid, durable instrument with a curved incisal guide pin. Extendable condylar shafts enabled receiving a hinge axis face-bow. The Bennett movement was calculated from the Hanau's formula, and rotating the condylar post up to 40   [1] Slika 5. Artikulator Stuart [1] Figure 6. The Dentatus Articulator [1] Slika 6. Artikulator Dentatus [1] degrees regulated it. As with the Hanau articulators, the size of Bennett movement was controlable, but not the timing or direction [1].

The Improved New Simplex Articulator
The Improved New Simplex Articulator (Figure 7) was distributed by the Dentists' Supply Co. of New York in 1960. This is an updated version of the Gysi Simplex articulator. It used average movements. The condylar inclination was 30 degrees, with a Bennett movement of 7.5 degrees. The incisal guide table was adjustable from 0 to 30 degrees to accommodate various amounts of vertical overlap of the teeth for each patient. It had model-locking pins to secure the maxillary and mandibular casts in place. A mounting jig, which doubles as an occlusal plane table, was used for arbitrarily mounting the maxillary cast [1].

The Verticulator
The Verticulator was developed by William Windish in 1960. The Verticulator consisted of two rigid members that separate and close only linearly in vertical dimension. It had a positive stop that locked in its closed position. Another model was introduced in 1962, which was able to accept full arch casts [1].

The Ney Articulator
The Ney articulator ( Figure 8) was designed by Anthony J. De Pietro in 1962. It is an arcon instrument with no locking device between the upper and lower members for centric position. The condylar elements can be set to varying intercondylar distances. When the metal condylar elements do not follow or duplicate pantographic tracings, more precise duplication is possible with custom ground plastic inserts. A plastic incisal guide table, or a metal incisal guide table that has a provision for making a region of freedom centric position can be used [1].

The Hanau Model 130-21 Articulator
The Hanau University Series or Model 130-21 articulator was designed to be a split-axis instrument. It had a central locking device and a mechanism to keep upper and lower members together. It was adjustable in varying intercondylar distances. The condylar paths and Bennett guide paths were straight. The Bennett guide paths that are located near midline did not allow for immediate side shift. It would accept all positional records but could not duplicate pantographic tracings. The incisal guide pin was designed to compensate for changes in vertical dimension. It was self tripoding in an inverted position [1].

The Whip-Mix Articulator
The Whip-Mix articulator was developed by Charles E. Stuart in 1964. This was a semiadjustable arcon articulator that had three intercondylar adjustments: small, medium and large. These were selected by means of the accompa-nying Quick Mount face-bow that uses the external auditory meatus as a posterior landmark. This face-bow had a nasion anterior guide for establishing an anterior point of reference for maxillary cast positioning. The condylar element of the Whip-Mix articulator was adjustable about the vertical and horizontal axis but not the sagittal axis; hence it could not be set to all positional records. The condylar and Bennett guide paths were straight. There was no provision for timing in the Bennett movement. There was no centric position-locking device, and the upper and lower members could not be attached mechanically [1].

The Simulator
The Simulator (Figure 9) was developed by Ernest R. Granger in 1968. It was a fully adjustable articulator that could be set from pantographic tracings, positional records and other tracings. There were curved condylar paths, but the unique feature of this articulator was the condylar path that rotates inwardly, a broken axis and a mechanical timing element that combine to reproduce mechanically the Bennett movement and Fischer's angle. The Simulator had condylar path locks that could be re- Figure 7. The Improved New Simplex Articulator [1] Slika 7. Poboljšani novi prosti artikulator [1] Figure 8. The Ney Articulator [1] Slika 8. Artikulator Ney [1]

Recent Advances SAM
The company was founded in 1971 by Heinz Mack, a practising dentist, in Munich, Germany. Their anatomically correct and skull related articulator system became known and identified as SAM (School Articulator Munich). These are basically arcon type of articulators. SAM developed a wide variety of articulator models, including SAM SE, SAM 2P, SAM 2PX and SAM 3. These articulators provide accurate functional simulation of mandibular movements [2,3].

The Artex Articulator
This articulator was developed by GIRRBACH DENTAL GMBH Company and was listed in the FDA on 24 th May, 1995. The ARTEX CN, which was the base model, is a non-arcon type average value articulator. The ARTEX CT is partially adjustable average-value articulator in non-Arcon design. Then came the ARTEX CP, which was partially adjustable average-value articulator with super smooth condyle track guide in Arcon design. The latest model was the ARTEX CR, which was fully adjustable average-value articulator in Arcon design. It provides comprehensive adjustment possibilities to reproduce the patient's clearance and movement dynamics [4].

The Protar Articulator
Developed by the KaVo Company during the begining of this century, the PROTAR articulators ( Figure 10) offer good precision, they are cost effective and provide superior handling. Four models are available-the PROTAR, the PROTAR 3, the PROTAR 5, the PROTAR 7, and the latest model is the PROTAR 9. The PROTAR is 6.4" H x 6.6" W x 8" D and weighs 2.5 lbs. The Protar 3 has an upper member with curved sagittal and pre-set condylar guidance paths, a 45° horizontal condylar inclination, and a 15° fixed Bennett angle. The PROTAR 5 has an upper member identical to the one in the Protar 3 with the exception that it has an adjustable Bennett angle and an adjustable horizontal condylar inclination. The PROTAR leased so that the upper member could be separated from the lower member. The incisal guide pin was curved [1].

The Denar Model D4A Articulator
The Denar Model D4A articulator was developed by Niles Guichet in 1963. This articulator was programmed from tracings made with a pneumatically controlled pantograph of the same company, the Denar Corp of Anaheim, California. It was a fully adjustable instrument that used interchangeable condylar guidances that could be adjusted. It had a definite centric lock and had accommodations to hold the casts in an open position. The curved incisal pin assembly could rest on a mechanical or plastic incisal guide table [1].

The Dentatus ARO Articulator
The Dentatus ARO articulator was manufactured by A.B. Dentatus in 1971. It had all the features of Dentatus ARL plus the unique feature of a movable arm that holds the mandibular cast. The universal joint and the locking device that attaches the movable arm to the base allowed repositioning of the mandibular cast without remounting. The gauge block was used to center the lower member to the upper member, but once the mandibular cast has been repositioned, the articulator or casts could not be interchanged without the aid of centric relation records [1].

The Panadent Articulators
The Panadent System is the latest approach to dental instrumentation. The Panadent System was based on the premise that it was possible to classify individual condylar movements into groups based on the amount of precurrent side shift. A series of statistically selected three-dimensional analogs of condylar axis motion was developed. The Panadent articulator was introduced in 1978. The current models were introduced in 1983. The major modification in the latest models was the Dynalink Panalock mechanical latch. This mechanism keeps the upper and lower articular frames joined together, yet permits an opening movement of 180 degrees [1]. Figure 10. The Protar Articulator [5] Slika 10. Artikulator Protar [1] Figure 9. The Simulator [1] Slika 9. Simulator [1] 7 has an upper member with adjustable sagittal angle and horizontal condylar paths as well as immediate sideshift and retrusion with an adjustable shift angle. The PROTAR 9 has an upper member identical to that of the Protar 7 with adjustable protrusion, distraction, and retrusion [5].

The Virtual Articulators
The latest breakthrough in the world of articulators was the introduction of the VIRTUAL articulators in 2003. This system not only simulates the temporo-mandibular joint movements in the modelling software by viewing it on the computer screen, but is also the only system that allows the dental technician to take the measurements of his/her own articulator, to scan it and to add these data to the software database. The articulator dimensions are faithfully saved in the software so as to be able to virtually articulate the models.

CONCLUSION
The large number and great range in complexity of modern articulators can mislead the dentist into thinking that the choice of a suitable instrument is difficult. However, the choice is greatly simplified if one considers what records can be obtained accurately, what the instrument will be required to do, and the fact that articulator technology is not a substitute for a biological understanding of the masticatory system [6]. An emerging understanding of the neurophysiology of mandibular movements and the influence of several morphological and behavioural considerations led to the notion that each patient is his or her own best articulator. Also, the success or failure of the final restoration is more dependent on the operator of the articulator than on the articulator itself [7].
The Late Carl O Boucher summed up the articulator controversy by stating, "It must be recognized that the person operating the instrument is more important than the instrument. If dentists understand articulators and their deficiencies, they can compensate for their inherent inadequacies".