Classification of articulators

Awni Rihani, D.D.S., M.Sc.* Emory University School of Dentistry, Atlanta, Ga.

Ah 1 e arge number of articulators and their wide range of adjustments makes classification difficult.

However, a review of the literature reveals many types of classifications that have been proposed.

Gillis’ divided articulators into two classes: (1) the adaptable or adjustable type and (2) the average or fixed type. Boucher’ classified articulators as nonad- justable or adjustable. He also subdivided the adjust- able type into two groups: (1) a two-dimensional instrument and (2) a three-dimensional instru- ment.

Kingery stated in Anthony’s textbook3 that for descriptive purposes articulators may be classified into two general groups: (1) simple articulators and (2) adjustable or adaptable articulators.

Based on the design of articulators, another clas- sification was devised by Beck.’ He divided articula- tors into three categories: (1) the suspension instru- ment, (2) the axis instrument, and (3) the tripod instrument.

Weinberg’, 6 adopted a different classification based on the concept associated with each articula- tor. In his opinion, there are four types of articula- tors: (1) arbitrary (Monson spherical theory), (2) positional (Stansbery tripod concept), (3) semiad- justable (Hanau H concept), and (4) fully adjustable (Hanau Kinescope concept, Gysi Trubyte concept, and McCollum concept).

Posselt7 classified articulators as plain line, mean value, and adjustable.

Sharry8 classified articulators as simple, hinge- type, fixed-guides type, and adjustable.

Heartwell and Rahn: emphasizing the role of pantographs in record registration, divided articula- tors into two classes: (1) instruments that will receive and reproduce pantographs and graphic tracings and (2) instruments that will not receive panto-

*Colonel Jordanian Army and consultant in Prosthetic Dentistry for the King Hussein Medical Center in Amman, Jordan. Currently Senior Resident in Removable Prostbodontics.

graphs, which are subdivided into four types: (a) hinge type, (b) arbitrary, (c) adjustable, and (d) instruments designed and used for complete denture construction.

Thomas,” attempting to simplify the classification of articulators, devised a new classification based on the type of records used. He divided articulators into three types: (1) arbitrary (not adjustable), (2) posi- tional (axis and nonaxis types, static records), and (3) functional (axis and nonaxis types, functional records).

These classifications have added confusion and made visualizing the relationships and differences between the groups difficult. The capability of adjustment is the point at which these articulators differ. Therefore, classifications should be based on adjustment capabilities.

REQUIREMENTS OF ARTICULATORS

Articulators have different adjustments, and some have more than others. To make any classification easy to visualize, and to avoid confusion because of these sophisticated adjustments, the requirements of an acceptable articulator must be defined. In pros- thetic dentistry the necessity of registering the following records is generally accepted: (1) face-bow record, (2) centric jaw relation record, (3) protrusive record, (4) lateral records, and (5) intercondylar distance record.

The intercondylar distance record is necessary so that the articulator can accept lateral records.” When the Gothic arch tracing (needlepoint tracing) is used, it can be followed precisely,‘” and an accurate hinge axis transfer can be accomplished.‘” When the intercondylar width can be adjusted to the individual patient, the articulator will adjust to more interocclusal jaw relation records.“’ This variable intercondylar distance affects the cusp paths. The greater the intercondylar distance, the more distal are the working and balancing cusp paths on the mandibular teeth and the more mesial they are on

344 MARCH 1960 VOLUME 43 NUMBER 3 002%3913/80/030344 + 04$00.40/00 1980 The C. V. Mosby Co.

CLASSIFICATION OF ARTICULATORS

Table I. Classification of articulators

Fully adjustable articulators Semiadjustable articulators Nonadjustable articulators

Can accept all the following five records: 1. Face-bow record 2. Centric jaw relation record 3. Protrusive record 4. Lateral records 5. Intercondylar distance record Examples: Hanau Kinescope, 1923; McCollum Gna-

thoscope, 1935; Granger Gnatholator, 1950; Stuarticulator, 1955; Ney-Depietro, 1962; Hanau 130-27, 1953; Simulator, 1968; Den- ar D4-A, 1968

Can accept all the following three rec- Can accept one or two of the following three ords: records:

1. Face-bow record 2. Centric jaw relation record 3. Protrusive record

1. Face-bow record 2. Centric jaw relation record 3. Protrusive record

Examples: Snow Acme, 1910; Gysi Adaptable,

1910; Hanau H, 1922; .Wadsworth, 1924; Gysi Trubyte, 1926; House, 1927; Dentatus, 1944; Bergstrom Ar- con, 1950; Hanau 130-28, 1963; Whip-Mix, 1968

Examples: Gariot, 1805; Evans, 1840; barn door hinge,

1858; Bonwill, 1858; Walker, 1896; Grit- man, 1899; Snow, 1906; Gysi Simplex, 1912; Monson, 1918; Stansbery, 1929; Phil- lips Occlusoscope, 1931; Kile Dentograph, 1945; Transograph, 1952; Pankey-Mann, 1955

the maxillary teeth. Conversely, the lesser the inter- condylar distance, the more mesial are the working and balancing cusp paths on the mandibular teeth and the more distal they are on the maxillary teeth.‘”

Some dentists believe that the ideal articulator must be adjusted to accommodate immediate Bennett shift and the Fischer angle and that it must accept pantograph tracings. These are points which need further discussion before any classification is adopted.

Gysi’” stated, “Every known means of registering Bennett movement is either so cumbersome or inac- curate as to be inefficient; the errors that might result from differences in the inclination of this movement are smaller than the unavoidable errors made during impression making and flasking, there- fore, we need not trouble ourselves provided the articulator allows an average movement of 15 degrees Bennett.” Some might say that this state- ment is outdated and that the modern pantograph (e.g., Denar) can follow this movement and can be set on the articulator.

Watt” studied the reproducibility of articulator settings from graphic records. He found that the high probabilit); of error in the use of this type of instrument made it unacceptable as a means of diagnosing occlusal disturbances.

Winstanley’” investigated the reproducibility of articulator settings obtained from graphic records using the Denar pantograph and Denar articulator. He found that some of the adjustments were unreli- able and concluded that the reproducibility was not quite to the extent one would hope for. In fact, it is not only the incapability of the articulator to repro-

duce some of the movements, but also the possibility of weight of the recording apparatus which alters the normal position and movements of the mandible.“’

In describing the Case articulator, Gibbs and Derda’” reported, “Either pantographic tracings or lateral interocclusal records can be used to set the Bennett movement on this articulator. However, because of the complexity and risk of error inherent in these methods, the authors feel that standard Bennett movement settings are preferable for most patients.”

With regard to Fischer angle, Gysi believed (as did Hanau) that this angle could be omitted from the articulator because its effect on the occlusal surfaces of the teeth is negligible. With a 3 mm cusp, the maximum error is approximately 0.1 mm at the second molar balancing cusp height.“’

NEW CLASSIFICATION SYSTEM

Articulators which accept the pantograph and reproduce the immediate Bennet shift and Fischer angle are preferred by some operators who are familiar with them. However, they should not be classified in a separate group; this might add more confusion. Classification should take into considera- tion how to transfer records made on the patient to the articulator and how to adjust the articulator to accept these records.

In treating patients with occlusal disturbances, and in making fixed partial dentures, the five records mentioned previously need to be recorded. If the articulator is designed so that it can be adjusted to accept all five records, it should be classified as a fulb adjustable articulator regardless of any other charac- teristics it may have.

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RIHANI

Fig. 1. Nonadjustable Gysi Simplex articulator.

Fig. 2. Semiadjustable Dentatus articulator.

In complete denture construction, it is acceptable to register three records. They are (1) the facebow, (2) the centric jaw relation, and (3) the protrusive record.

All articulators which are designed so that they can be adjusted to accept these three records are classified as semiadjustable articulators. If the articula- tor is not designed to be adjusted to accept each of these three records, it should be classified as a nonadjustable articulator, whatever other characteris- tics it has.

Fig. 3. Fully adjustable Hanau 130-21 articulator.

CLASSIFICATION OF ARTICULATORS USING THE NEW SYSTEM

To demonstrate this simplified classification system, I have classified some of the old and new articulators used in dentistry. The classification is given in Table I.

Nonadjustable articulators

Gariot, 1805; Evans, 1840; barn door hinge, 1858; Bonwill, 1858; Walker, 1896 (has adjustable condylar guidance, but does not accept the facebow record); Gritman, 1899; Snow, 1906; Gysi Simplex, 1912 (Fig. 1); Monson, 1918; Stansbery, 1929 (based on the tripod theory, where there is no condylar control); Philips Occlusoscope, 1931 (based on the tripod theory also, and does not accept the face-bow record); Kile Dentograph, 1945 (based on the prin- ciple of the tripod); Transograph, 1952 (contains two face-bows, upper and lower, connected to each other; there is no condylar guidance); and Pankey-Mann, 1955 (based on the spherical theory using special face-bow to mount the mandibular cast).

Semiadjustable articulators

Snow Acme, 1910; Gysi Adaptable, 1910 (does not accept lateral records); Hanau H, 1922, Wadsworth, 1924; Gysi Trubyte, 1926 (does not accept the intercondylar distance record); House, 1927 (does not accept the intercondylar distance record, satisfies Bonwill principles); Dentatus, 1944 (Fig. 2); Berg-

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CLASSIFICATION OF ARTICULATORS

strom Arcon, 1950; Hanau 130-28, 1963; and Whip- Mix, 1968.

Fully adjustable articulators

Hanau Kinescope, 1923; McCollum Gnatho- scope, 1935; Granger Gnatholator, 1950; Stuartartic- ulator, 1955; Ney-Depietro, 1962; Hanau 130-2 1, 1963 (Fig. 3); Simulator, 1968; and Denar D4-A, 1968.

SUMMARY

A simple classification in familiar terms with definite, clear characteristics can be adopted. This classification system is based on the number of records used and the adjustments necessary for the articulator to accept these records.

The classification divides the articulators into nonadjustable, semiadjustable, and fully adjustable articulators (Table I).

I would like to thank Dr. Francis W. Shaffer, Chairman,

Department of Removable Prosthodontics, and Dr. Kenneth A.

Turner, Associate Professor, Department of Crown and Bridge,

Emory University School of Dentistry, for their advice and

encouragement.

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Anthony, L. P.: The American Text Book of Prosthetic

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Beck, H. 0.: Choosing the articulator. J Am Dent Assoc

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pantograph and articulator. J PROSTHET DENT 38:660,

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Re,tmnt requests to: DR. AWNI RIHANI P. 0. Box 3036 AMMAN, JORDAN

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