INTRODUCTION Articulating anything is like carving statue. On building a statue, a sculptor does not keep on adding clay to his subjects, actually he keeps chiselling among at the unessential until the truth is revealed without obstructions. That is the articulator, though an important mechanical entity in itself, is meaningless unless that, occlusion functions in the mouth in harmony with biologic factors that regulate the mandibular activity of the patient. If it were practical to do so, the patient’s mouth would be the best articulator. I would like to say, “Begin with, the end in mind:. As is glossary of prosthodontic terms, articulator is defined as a mechanical instrument that represents the TMJ and jaws to which maxillary and mandibular casts may be attached to simulate some or all mandibular movements. HISTORY : There have been a series of articulators that have been introduced if we glance at the past; the numbers are many and the dentist becomes confused as to which one to choose. Philip pfaff was the person who introduced the earliest known articulators. In 1756, he introduced the ‘ Slab articulator’. In this, the distal end of the mandibular cast was extended and grooved, into these extensions, maxillary casts were fitted. The first mechanical articulator was introduced by J.B. Garriot. In 1805, he introduced ‘Garriot Hinge Joint Articulator’. It consisted of hinges with a set screw in the posterior, against a metal plate to serve as a vertical stop. In 1830, Howarth & Ladmore, produced a most common method for relating casts with the help of plaster index. (also called as “Plaster articulators”). It consisted of two nested metal boxes which were held in position and the hinge movement was controlled with elastics. The casts were secured in place, with twins or elastics.
Another similar device was the spring field articulators, consisted of two hinged metal boxes with each box having metal mounting pins for securing the casts with plaster. The first improvement made to the simple hinge articulator was a tongue-in-groove (sliding) mechanism for changing the antero-posterior position of the upper member. The planeline articulator and the Moffitt represent devices with lower members designed to imitate the condyle, coronoid process and ramus of mandible. Initially, liberal amounts of soft crude wax was used to make impressions and, at the same time, record a bite which was known as “mush bite” and the centric relation record with this procedure was just plain luck. In 1840, James Cameron of Philadelphia, produced his unique “Pole stand” design. This articulator had features that allowed both the upper and lower members to be arbitrarely adjusted. “Springs” have been incorporated in to articulators since 1850’s. The most highly adjustable hinge articulator award could be given to two devices, the Oehlecker, 1878, and the Moffitt, 1898. Henrich Oehlecker of Hamburg, Germany, designed an articulator much like that of microscope stage with fine adjustment controls for 3 planes of movement. On the other hand John W. Moffitt, of Philadelphia, included numerous closely spaced vertical and horizontal holes for making small adjustments. In 1876, George Davidson of Lambeth, England added a new dimension to the term “adaptable” when he patented a articulator with a ball and socket (universal) joint on the upper member, it also had rod and sleeve mechanism for both vertical and horizontal adjustments. Bonwill, was the first to use springs as a mechanism for holding the individual condylar elements in centric position while allowing protrusive and lateral movements to occur.
In 1864, Bonwill introduced the dental profession to theory of tooth guided (balanced ) occlusion along with the anatomical articulators. This articulator could not guide but it could follow. In 1889, Luce of Germany described the forward and downward movements. in 1895, Kelly R.Bragg, of Shelbenia invented a device which combined the articulator and vulcanizing flasks, and by using special impression trays to transfer the casts directly to the flasks made it unnecessary to remove the casts from articulator until processing. Evens, Hayes, and Bonwill (1899) are the early examples of articulator with “Vertical stop”. In 1899, Grittman introduced an articulator with : 1) Fixed condylar paths : this was modified by George B.Snow as the “New century articulator” in 1906 which was later modified. 2) Incisal pin. 3) Posterior extension to prevent tipping were included in it. In 1902, Kerr Brothers introduced the KERR Articulator with : 1) Fixed protrusive and lateral movements. 2) Hinge in the same plane as occlusal planes In 1910, ACME articulator was introduced which was elaboration of George. B. Snow. 1) It is available in 3 models to accommodate 3 ranges of intercondylar distance. 2) The condylar paths are adjustable straight paths. 3) The incisal guide pins rests on changeable guide. 4) Benett movement is provided. Gysi introduced “Adaptable” articulator in 1912. It had only fixed 45degree incisal guide table. Gysi continued the exact incisal guide design in his “Simplex” articulator, an “average value” version of the “Adaptable”. He suggested
that the slope of “Simplex” incisal table could be altered with use of metal plate and modelling plastic. In 1916, Rupert E. Hall deviced “Alligator”. It had a “Single rotation centre”. It was the first articulator which included an incisal guide table with adjustable lateral wings. In 1917, Hall deviced “Dental Occluding Frame” which had adjustable, curved condylar paths, including settings for Balkwill-Bennett angle, and a mechanism for adjusting the intercondylar distance. It also included a horizontal incisal table with adjustable lateral wings and a triangular guiding edge on each lateral wing that could be set to follow “Gothic arch” tracing. In 1918, Hall patented the “Automatic anatomic” articulator based on his “Conical” theory of occlusion. It has been generally accepted that Gysi coined the term “Gothic arch” to describe the character of incisor point movement in horizontal plane. Gysi was the first investigator to design and study the incisal pin and guide assembly and to report its significance for reproducing mandibular movements. The BERGSTROM articulator is an arcon instrument. This term has been coined by Bergstrom, the term comes from first two letters of articulator and the first three letters of condyle, the original Hanau had many similar features. The STEPHAN Articulator : Developed in 1921 and was similar in design to Garriot Hinge articulator except that it has : 1) Fixed condylar inclination. 2) Allows for arbitrary lateral movement. Useful in fabrication of small restorations and for prosthesis repair. They can be used for complete dentures when non-cusp teeth are indicated.
Hanan Model M. Kinoscope : Rudolf L. Hanau, in 1923 developed Kinoscope which has double condylar posts on each sides, each one for horizontal and lateral condylar guidance. Hanau model H110 and modified H110 was later developed in 1922 and 1927 respectively. In 1928, Gysi patented “Trubyte” articulator which had incisal table with guiding lateral edges that could be set to follow incisor point “gothic arch” tracings. It was the first articulator with an adjustable incisal guide assembly. It had 100 lateral wings called as “FISCHER ANGLE”. Between 1922 and 1927, Needles and Milus .M. House developed House-Needles incisal guidance system for dental articulators. Stansberry tripod : Before 1929, articulators could not accept all the positional records. In this instrument, maxillary cast is mounted in an arbitrary position, later the mandibular cast is mounted with centric relation in plaster. The articulator reproduce positions, not movements. HANAU CROWN AND BRIDGE ARTICULATORS : Small articulator with a posterior pin and cam guidance mechanism can be set to simulate working and balancing side excursion of 150. It can be set for left & right quadrant or for anterior restorations. Fixed protrusive movement is 300. From 1940, Stephan Articulator : Modified in 1940 with fixed condylar path of 300. It is same as 1921 model except the upper and lower mounting arms are longer. Stephan articulator model P : Additional features are incisal pin and a vertical height adjustment. Another version includes a fixed 100 incisal guidance.
TRANSOGRAPH BY PAGE : Presented in 1952. It is a split axis instrument designed to allow each condylar axis to function independent of the other. He did not believe in the common hinge axis, that is why he split it in to two. THE DENTOGRAPH : Designed by KILE in 1955 was primarily used for complete denture construction. The vertical dimension of occlusion is established by use of carborandum and plaster occlusal rims developed in a generated path by the Patterson method. THE DUPLIFUNCTIONAL ARTICULATOR : Designed by Irish & presented in 1965. Primarily for use in complete denture construction. It has 2 main purposes, first it records each patient mandibular movements and then without further convertive procedures serves a 3D tripod type of articulator upon which dentures may be constructed and then occlusion balanced. McCollum developed a mandibular movement records and an articulator Gnathoscope in 1939. THE STUART ARTICULATOR : The stuart gnathologic computers was designed by C.E Stuart in 1955 (GNATHOSCOPE) Gnathology is defined as a science that deals with masticatory apparatus as a whole including morphology, anatomy, histology, physiology, pathology and therapeutics. Features : 1.
The upper frame carries all cams that direct the rotations and
slidings of the condylar elements and the fossae. 2.
The lower frame carries the condylar elements and simulate
mandible. 3.
The intercondylar distances is adjustable to each patient.
4.
The fossa cup can be adjusted.
5.
The plastic eminence can be altered according to that of the
patient if the protrusive and lateral path difference is there. 6.
The operating parts are devoid of set screws.
7.
The side shift (Bennett) and its timings is cut in to lateral
wings. The instrument will receive pantograms made in the 3 planes. It also records the amount and character of movements in one plane and relation to other planes. TRUBYTE SIMPLEX : The new simplex uses average movements : 1) The condylar guides are inclined at 300. 2) Bennett movement of 7.50. 3) The incisal guide table adjusts from 0-300
A mounting jig which doubles to level the occlusal plane is used for arbitrary mounting of upper cast. Alternatively a plane orientation jig positions the lower cast first and it is used for positioning the gothic arch transfer – useful in complete denture construction. NEY ARTICULATOR : It was designed by Dr. D. Pietro in 1960 and was an arcon instrument. 1.
This is the first articulator to have condylar housings that contained adjustable rear, medial and top walls in one assembly.
2.
Intercondylar distance is adjustable. HANAU H2 : Discussed later in detail DENTATUS: This is another adjustable articulator designed in 1944 in Sweden. The condylar elements are attached to upper member and the condylar path is straight. Bennett angle is calibrated to 400.
Inter condylar distance is fixed.
This recieves hinge axis face bow transfer.
Its features are similar to Hanau Model H. MODIFIED DENTATUS ARO : With movable arms that holds the cast. HANAU 130-21 : Discussed later WHIP MIX : Discussed later THE SIMULATOR ARTICULATOR : It was designed by Ernest Granger. It was set with a conventional pantograph. A minigraph could be used when full mouth pantographic tracings is not feasible. It consisted of only two anterior recording plates which were related to casts mounted to the hinge axis. Tracings of protrusive and lateral movements were made. Its Bennett guide can be set by adjustment only and cannot be customized. PANADENT ARTICULATORS DENAR D4A DENAR D5A DENAR MARK II TMJ ARTICULATORS CYBERHOBY ARTICULATOR. PARTS OF ARTICULATOR The articulator is programmed to produce a motion that is determinant of the occlusal anatomy being developed. The motion produced by the instrument is dictated by the settings of these control areas, the two condylar and incisal guide control.
This is clinically significant in that it encourages the treatment sequences to be accomplished according to the dentist or patient desires rather than be dictated by instrument limitations. 1. Posterior control areas ( condylar controls) : These control areas are adjusted according to patient’s TMJ characteristics and can be identified by a pantograph. 2. Anterior control areas (incisal guide control) : This control area is of equal importance as the posterior control area. In existing occlusions it is adjusted in consideration of the vertical and horizontal overlap of anterior teeth. In edentulous mouth, the vertical and horizontal overlap of anterior teeth is determined by esthetic and phonetic measurements. 3. Centric occlusal position of the mounted casts in proper orientation of the control areas is a must. CLASSIFICATION OF ARTICULATORS I. Articulators based on theories of occlusion : 1) BONWILL’S THEORY OF OCCLUSION : It proposed that the teeth move in relation to each other as guided by the condylar controls and the incisal point. It was also known as the theory of the equilateral triangle in which there was a 4 inch (10cm) distance between condyle and between each condyle and the incisal point. It was designed by W.G.A. Bonwill Since condylar guidances were not adjustable, movement in horizontal plane is only permitted (eccentric position) 2) CONICAL THEORY OF OCCLUSION : This proposed that the lower teeth move over the surfaces of the upper teeth as over the surface of cone, with a generating angle of 450 and with the central axis of cone tipped at 450 angle to the occlusal plane eg. Hall automatic articulator designed by R.E. Hall.
Teeth with 450 cusps were necessary for constructing dentures on this articulator. 3) SPHERICAL THEORY OF OCCLUSION : It proposes that the lower teeth moves over the surface of the upper teeth as over the surface of sphere with a diameter of 8 inches (20cm). The center of the sphere is located in the region of the glabella, and the surface of the sphere passes through the glenoid fossae along the articular eminences or concentric with them. Proposed by G.S. MONSON in 1918. The draw back of this classification is that provision was not made for variation from the theoretical relationship that occur in different persons. II. Articulators based on the types of records used for their adjustment: Three general classes of records are used for transferring maxillomandibular relationship from the patient to the articulator. 1. Inter occlusal records 2. Graphic records 3. Hinge axis recods.
Some articulators are designed for use with only one record where as others can use two or three types of records in combination. 1. Inter Occlusal Record Adjustment : These records can be made in wax, pop, zinc oxide eugenol paste or cold-curing acrylic resin. These records is of only one positional relationship of the lower jaw to upper jaw. 2. Graphic record adjustment : Since the graphic records consists of records of the extreme border positions of mandibular movement, the articulator must be capable of producing these curved movements provided the graphic records are correct. These records are difficult and unreliable in edentulous patients.
3. Hinge Axis location for adjusting articulator : The correct location of the opening and closing axis of the mandible should be made, if not the correct adjustment of these instrument is not possible. III. Articulator classification based on the instruments function : (At International Prosthodontic workshop on complete denture occlusion at the University of Michigan in 1972). Class I : Simple holding instruments capable of accepting a single static relationship. Vertical motion is possible, only for convenience. Eg. Slab articulator, hinge joint articulator, barn door hinge. Class II : Instruments that permit horizontal as well as vertical motion but do not orient the motion to TMJ via a face bow transfer. A) Eccentric motion permitted is based on average or arbitrary value e.g. Gysi simplex articulator, Grittman. B) Eccentric motion permitted is based on theories of arbitrary motion. Eg. Monson maxillomandibular articulator. C) Eccentric motion permitted is determined by the patient using engraving methods . eg. Howarth articulator, Dentograph. Class III : Instruments that simulate condylar pathways using average or mechanical equivalents for all or part of the motion. Allows joint orientation of the cats via face bow transfer – Hanumate. A) Instruments that accept a static protrusive regstration and use equivalents for the rest of motion. Eg. Hanau model H, Dentatus Bergstrom.
B) Instruments that accept static lateral, protrusive registrations and use equivalents for the rest of motion e.g Trubyte articulator, Ney, Kinoscope, Hanau 130-21, Panadent & Stansberry tripod. Class IV : Instruments that will accept 3 dimensional dynamic registrations. These allow for joint orientation of casts via a face bow transfer. A) The cams representing the condylar paths are formed by registrations engraved by the patient . Eg. TMJ articulator. B) Instruments that have condylar paths that can be angled and customized either by selection from a variety of curvatures or by modification or both eg. Denar D4A, Denar 5A (current & simulator.). IV. Classification according to Heartwell : Class I : These are instruments that receive and reproduce stereograms (pantograms). Can be adjusted to permit individual condylar movement in each of 3 planes. They are capable of reproducing the timing of the side shift of the a orbiting (balancing) side & its direction of the rotating (working) side . Class II : They do not receive the stereograms. Type 1 (Hinge) : This type is capable of opening and closing in a hinge movement, a few limited non-adjustable excursive like movements. Type 2 (Arbitrary ). This is designed to adapt to specific theories of occlusion or is oriented to a specific technique. Type 3 (Average): This type is designed to provide condylar element guidance by mean of averages, positional records of mini recorder systems. Type 4 (Special) : This type is designed to be used primarily for complete dentures.
Examples : Class I : Mccollum Gnathoscope. Granger Gnathoscope. Hanau Kinoscope Cosmex Stuart Gnathologic computer TMJ stenographic Denar D5A Class II (Type 1) : Barn Door hinge
Stephens
Garriot
Crescent
Gysi
Trubyte Simplex
Acme
Twinstage occluder
Bonwill Type 2 : Monson Handy II The Correlator Transograph The Gnathic relator Verticulator Type 3 : House Dentatus Hanau (several models) Whipmix Denar – mark II and Omnimodel TMJ – mechanical fossa & molded fossa models.
Panadent Type 4 : Stransberry tripod Kile dentograph Irish Dupli – functional CLASSIFICATION BY VARIOUS AUTHORS V. Gillis (1926), Boucher (1934) and Kingery (1934) Classification – Adjustable and Non adjustable. VI. Beck’s (1962) - Suspension instrument - The axis - The tripod. VII. Posselt’s (1968) - Plain line. - Mean Value - Adjustable VIII. Thomas (1973) - Arbitrary - Positional - Functional IX. Riliani (1980) - Fully adjustable - Semi – adjustable - Non – adjustable. X. Weinberg (1963) - Arbitrary - Positional - Semi-adjustable - Fully adjustable.
XI. Sharry (1974) - Simple - Hinge type - Fixed guide type - Adjustable POSSELT’S CLASSIFICATION 1) Plain line or simple hinge. 2) Mean value types with fixed condylar path and incisal inclines. 3) Adjustable types. In 1) and 2) no control mechanisms are there to adjust. - Only interocclusal centric relation can be recorded. - They
lack
individualized
information
concerning
spatial
relationship and occlusal arrangement of artificial teeth, so may not resemble patient actual jaw movements. Adjustable articulators : Semi adjustable. Fully adjustable. Semi adjustable : Posterior control mechanisms set by
interocclusal
positional records e.g. Hanau, Dentatus. Fully adjustable : Use 3 dimensional pantographs to guide the setting of posterior control mechanisms e.g. Denar. REQUIREMENTS - It should hold casts in correct horizontal relationship. - It should hold casts in correct vertical relationship. - It should provide a positive anterior vertical stop (incisal pin) - It should accept a face bow transfer record utilizing anterior reference point. - It should open and close in a hinge movement. - It should allow protrusive and lateral jaw motion.
- The moving parts should move freely and be accurately machined. - The non-moving parts should be a rigid construction made of non corrosive material. - The patient casts must be easily removable and attachable to the articulator without loosing their correct horizontal and vertical relationship. - The design should be such that there is adequate distance between the upper and lower members and that vision is not obscured from rear. - The articulator should be stable on laboratory bench and not too bulky and heavy. ADDITIONAL REQUIREMENTS : - Adjustable horizontal and lateral condylar guide elements. - The condylar elements as a part of lower frame and condylar guides as a part of upper frame. - A mechanism to accept a third reference point from a face bow transfer record. - A terminal hinge position locking device. - Removable mounting plates that can be repositioned accurately. - An adjustable incisal guide table. - Adjustable intercondylar width of the condylar elements. USES : Primary Purpose : • To hold opposing casts in a predetermined fixed relationship. • To open and close. • To produce border and intra-border diagnostic sliding motions of the teeth similar to those in the mouth.
Other uses : a) To diagnose dental occlusal conditions in both natural and artificial dentitions eg. If patient has TMJ problem. b) To plan dental procedures that involve positions, contours and relationships of both natural and artificial teeth as they relate to each other. c) To aid in fabrication of dental restorations and lost dental parts. d) To correct and modify completed restorations eg. In casted crown. e) Can be helpful in teaching and studying of occlusion and mandibular movements. ADVANTAGES : It is often said that, “The patient’s mouth is the best articulator”. The very fact that the final test for a dental restoration is the occlusal harmony obtained when the restortion is placed in the patient’s mouth. But still mechanical articulators have many advantages over the mouth. 1. Properly mounted casts allow the operator to better visualize the patient’s occlusion, especially from lingual view. 2. Patient co-operation is not a factor when using an articulator once the appropriate interocclusal records are obtained from the patient. 3. The refinement of complete denture occlusion in the mouth is extremely difficult because of shifting denture bases and resiliency of the supporting tissues. After obtaining interocclusal records, the complete denture occlusion can be refined outside the mouth on an articulators. 4. Chair time and patient appointment time is required when utilizing the mouth as an articulator. 5. More procedures can be delegated to auxillary personnel when utilizing an articulator for development of the patients occlusion.
6. The patient’s saliva, tongue & cheeks are not factors when using an articulator. LIMITATIONS :
An articulator is a mechanical instrument made of metal.
The articulator is subject to error in tolling and errors resulting
from metal fatigue and wear.
It is unlikely for any articulator to duplicate condylar
movements in the TMJ.
The movements simulated are empty mouth sliding motions,
not functional movements. Effectiveness of an articulator depends on : The person who understands the construction and purpose, the anatomy of the joints, their movements and the neuromuscular system, precision and accuracy in registering jaw relations and the sensitivity of the instrument to record these. SELECTION OF AN ARTICULATOR FOR COMPLETE DENTURE. The large number of different designs of articulator are available which leave the dentist quite confused as to which one to choose. The choice of the articulators should be made according to the best intercuspal position required for the patient. If occlusion contacts are to be perfected in centric relation only, then a simple hinge articulator can be selected. If denture teeth are to have cross arch and cross tooth balanced occlusion, then minimum requirement is semi adjustable e.g. Hanau or Whipmix. If complete control of occlusion is desired, a completely adjustable, 3 dimensional articulator is selected. These complicated articulators pose some problems for use in making complete dentures because of the
resiliency of the soft tissues of the basal seat on which recording bases must rest. As the resiliency permits some movement of the bases in relation to the bone, the records made are not necessarily records of the true path movement of the bone. According to clinical experience and testing, recommendation of the Hanau model 130 – 28 and Whip mix articulators is made on the North American continent. According to a survey in U.S dental schools (JPD 1985 Vol. 54, Pg 296) : • Out of 81 articulators, 67 were arcon design. • Commonly used articulators were Whip mix, Hanau 158, Hanau H-2 and Denar mark II. • Most common in fixed prosthodontics were Whip mix (16) and Denar mark II (1) & in RPD were Hanau 158(14) and Hanau 96 H-2 (13). ARCON V/S NON ARCON Arcon type : Instrument with condyles in the lower member and condylar guides on the upper member i.e. lower member is movable. Non Acron : Condylar on upper member and condylar guidance on lower member. The relative merits of arcon and non arcon instrument have been discussed by Beck (1956) and by Weinberg (1963) among others. Weinberg concluded that the arcon and non arcon type produce the same guidance. Beck states that the constant relation of occlusal plane and arcon guides exists at any position of the upper member and thus duplication of mandibular movement is more accurate in arcon type. For complete denture construction, it makes little difference whether the instrument is arcon or non arcon, so Beck was not able to demonstrate
any superiority in clinical evaluation of dentures fabricated in Bergstrom’s arcon articulator & overdentures fabricated in Hanau H. Advantages of Arcon : Since the relationship of the condyles and condylar guidances is similar as that of glenoid fossa in skull, visualization and understanding of condylar movement is easier. Arcon V/s Non Arcon : (JPD 1956 (6) Pg. 239) • The term was coined by Bergstrom. • In “Arcon” principle mechanical feature is the attachment of the equivalent condylar guides to the upper member of the articulator. • The term condylar will be applied to the instruments whose equivalent condylar guides are attached to lower member of the instrument. Following are feature of arcon articulator which resemble those of condylar type : 1) The shaft axis of each instrument represents a line passing through or near the condyles. 2) The joint distance and the orientation of the casts are those of Bonwill’s equilateral triangle (except in those articulators where condylar joint distance is adjustable) 3) The symphyseal angle is about 135 degrees. 4) The incisal guide table is in the same relative position, and adjustable in A-P direction. The feature incorporated in Bergstrom arcon articulator which vary from most condylar types are : 1) A face bow registration which employs F-H plane is used. 2) The axis equivalent guide, which is adjustable from 0-900, is fixed to
upper member of arcon instrument and has convex curvature of 0.022 mm.
3) The Bennett angle is fixed at 15 degrees CONCLUSION 1) By fixing condylar guide to upper member of arcon articulator, and the shaft axis to lower member, a constant relationship exists between the occlusal plane and the arcon guides of the instrument at any position of upper member, making the reproduction of mandibular movement more accurate. 2) This occlusal plane and arcon guide relationship has been proved of definite value in setting the arcon paths of instrument by a protrusive interocclusal record since few factors influence the setting of guide paths. 3) In condylar articulator, setting of condylar inclinations by a protrusive interocclusal record is influenced by variety of factors like magnitude of protrusive movement, inclination of incisal guide, position of incisal guide etc. 4) In lateral movement there is an error in both arcon and condylar articulator when the joint distance of the skull does not equal the joint distance of instrument used. BENNETT MOVEMENT Definition : Condylar movements of the working side in a horizontal plane. Mandibular Side Shift : Bodily side shift of the mandible that occurs during lateral jaw movements. It varies from patient to patient, from one side to the other in the same patient. It can vary from a direct lateral movement before it starts its excursion down one path to a movement in which it gradually moves sideways as it goes down the path; this relation of side shift lateral excursion is called Timing of the Bennett movement. As some variations
are seen in Bennett movement, the exact path of travel must be recorded & duplicated on an articulator if non interfering cusps have to be designed. Importance : The Bennett movement primarily determines the height and position of the cusps, which in turn effect the depth of fossa, and a custom groove to allow for a passage of cusps without lateral interference. CLASSIFICATION OF MANDIBULAR SIDE SHIFT Mandibular side shift : Bodily side shift of the mandible that occurs during lateral jaw movement. 1) Progressive side shift : Mandibular side shift that occurs at a rate or
amount which is directly proportional to the forward movement of the orbiting condyle. 2) Immediate side shift : Mandibular side shift in which orbiting
condyle moves essentially straight medially as it leaves centric relation. 3) Early side shift : Mandibular side shift in which the greatest rate of
side shift occurs early in the first 4 mm of forward movement of the orbiting condyles as it leaves centric relation. 4) Disturbed side shift : Mandibular side shift in which the greatest rate
of side shift is distributed throughout the first 4 mm of forward movement of the orbiting condyle as it leaves centric relation. Applications of simple hinge •
Permit only a simple hinge opening around a horizontal axis
whose distance from the casts is orbitarily determined and less than the distance between patient TMJ’s and teeth. •
Cannot simulate mandibular movements or positions outside
patient’s mouth and are inadequate for occlusal diagnosis. •
Can observe static relationships.
•
Restoration may have to be adjusted in the mouth.
Applications and limitations of semi adjustable articulators They are widely used in diagnosis and treatment in complete denture prosthodontics, FPD and RPD. Their limitations in providing only an approximation of true mandibular movements are acceptable when adequate anterior guidance is present. When guidance is reduced, it becomes more critical to use an instrument which mirrors the movements more exactly so that the occlusal anatomy may be reproduced in the laboratory to create intercuspal position, contacts yet disclude in other positions. If restorations are made on semi adjustable articulators, the occlusal adjustment needed in lateral excursion becomes progressively less acceptable. Also, a positive error may be eliminated by guidance. Where as, a negative one may requires the restoration to be remade. Applications of fully adjustable Fully adjustable articulators are indicated when restoring opposing teeth in complex cases, with minimal anterior guidance or group functions. They enable the cusps and grooves to be positioned correctly with respect to the direction of lateral and protrusive movements and will greatly reduce the amount of occlusal adjustment required when restorations are tried in the mouth. AVERAGE VALUE ARTICULATOR : Here simple hinge is replace by a mechanism which allows the upper member to be moved upward and backward relative to lower. This path of movement is at same inclination on either side, about 300 angle is made by condylar guide to occlusal plane in average individual. Anterior part of the upper member is supported by incisal guide rod through upper and incisal guide table on lower. The angle of incisal guidance is about 100 to 150. For mounting, according to Bonwill concept, an incisal guidance rod and an horizontal bar through two pillars is included. This can be used for routine complete denture construction.
HANAU ARTICULATORS Hanau Model H. (Arcon) : It was designed in 1923 by Rudolf .L. Hanau originally for complete denture construction. 1.
Condylar guidance were on an axle and were part of upper
frame (Arcon) 2.
Intercondylar distance is fixed at 110 mm. 3.
Condylar elements functioned in a slot type guidance
mechanism and horizontal condylar guide can be adjusted from – 40 to + 80 degrees (Horizontal condylar inclination set by protrusive records) 4.
The (lateral guidance side shift) adjustments can be adjusted
from 0-20 degrees. This was calculated by Hanau in formula L = H/8 + 12 L = Lateral condylar angle in degrees. H = Horizontal condylar inclination in degrees The derivative for this equation are not known and so the validity is questionable since large changes in the horizontal condylar inclination angle will result in only a few degrees change in the side shift angle. 5. Also accepts a face bow transfer. 6. Universal incisal guide table was not there. HANAU H2 (MODEL 96) (Non Arcon) : • It is a condylar or non arcon type with the condylar guidance controls attached to lower member of articulator. • The original features of Hanau H have been retained and additions, auditory pins have been added to the condylar guidance mechanism to receive an ear piece face bow.
•
The lateral adjustment for side shift has been increased from 0-300.
• Intercondylar distance is fixed at 110 mm. Incisal guide table is adjustable both in sagittal and frontal planes (Single sagittal, right and left frontal). HANAU ARCON H2 : (MODEL 158) • Introduced by Hanau in 1977. • Same as Hanau H2 except that is arcon. • Fixed intercondylar distance – 110 mm and accepts a face bow transfer. • Adjustable horizontal condylar guidance and Bennett controls. • Standard incisal guide table as in H2. • The upper and lower members are attached to each other by means of the condyles and their guidance’s. • It can be used with fascia face bow, an ear piece or twirl bow. • The face bow can be aligned to the Frankfort horizontal plane by means of an orbital pointer. Without an orbital pointer, the incisal plane is adjusted so that it is in level with the notch on the incisal pin which is 47 mm below the horizontal condylar plane or 54 mm below the Frankfort horizontal plane. • The Bennett angulation is either calculated by Hanau’s equation or is adjusted by lateral interocclusal records. • Horizontal inclinations are set as in H2. • If adjustable axis face bow is to be used, then the articulator must be equipped with extendible condylar shafts as in H2. HANAU WIDE VUE (Models 183 & 184) : • The Hanau wide VUE I and Hanau Wide VUE II are newest articulators. • Arcon and fixed intercondylar distance 110 mm.
• Difference is that Hanau wide VUE I has a closed condylar track and Hanau wide VUE II has an open condylar track which allows upper member to be removed. Wide VUE II has condylar retainers to avoid accidental separation of upper member. • A micrometer protrusive – retrusive condylar adjustment is available which is accurate to 0.05 inch. • Horizontal condylar angle is adjustable from –20 to +60 degrees and side shift angle adjustment is from 0 – 30 degrees (same as H2). The straight incisal guide pin or with adjustable foot is available. • The straight pin has dual ends – chiesel and spherical and extends above the upper member to act as a third point stability when inverting the articulator for mandibular cast mounting. • 3 incisal guide tables are available: mechanical, flat and pantacrylic table. HANAU RADIAL SHIFT (MODEL 166): • First produced in 1981. • Arcon, intercondylar distance is 110mm, right and left centric latches, upper member can be removed for waxing. • Can be used with fascia, ear piece face bow and twirl bow. • The condylar guidance is designed to incorporate a curved immediate side shift (radial shift) with adjustable progressive Bennett angle of 0-60 degrees. •
The radial shift adjustment has 3mm radius and allows up to 3mm of radial shift.
• The condylar guidance is adjustable horizontally and has a curved superior wall with 0.75 inch radius.
• A straight incisal guide pin or an incisal guide table with adjustable foot is available –mechanical, flat and pantacrylic table are available. THE 130 UNIVERSITY SERIES 130-21 MODEL: • Arcon, used for occlusal corrections. • Intercondylar width adjustment from 94-150mm. • Split vertical and lateral compound axis permits adjustment from -30 to +30 degrees in both planes. • Lateral condylar angle is adjustable from 0-40 degrees. • Upper member may be separated from the lower member by loosening a retention lock. 130-22 MODEL: • Non-arcon used for the restoration of natural teeth . • Variable intercondylar width settings of 94-150 mm. • Upper and lower members can be separated. 130-28 MODEL: •
Arcon checkbite articulator.
• For standard fixed and removable prasthodontic situations. • Intercondylar adjustment is 94-150mm. • Condylar inclination adjustment of 0-60 degrees, lateral adjustment of 0-40 degrees. 130-30 MODEL: • Only addition of a special retrusive –progressive condylar adjustment. HANAU MATE –165: (Average articulator) • Fixed intercondylar width –110mm. • 30 degrees fixed horizontal condylar inclination.
• 15 degrees fixed progressive side shift angle (Bennett). • 10 degrees protrusive and lateral incial guide table. Advantages: • Upper frame can be separated by loosening two locks. • Receives most average face bows. • Casts can be mounted without mounting plates. • Excellent lingual visibility. XP-51 ARTICULATOR (JPD 1975 VOL 33, Pg 158): • Every patient has a different intercondylar distance which is to be compensated by the articulator. • The Hanau XP-51 is arcon type with fixed distance of 90mm between the condylar posts. • The articulator is adjustable to lateral interocclusal records. •
The adjustable guides with in the condylar housing are the Bennett guides, horizontal condylar guides and an adjustable posterior wall which can be adjusted to the position of the working side condyle in lateral movement. When adjusted, the wall contacts and forms a guiding position for the working side condyle further, the posterior wall combines to compensate for the lack of an intercondylar distance on the articulator. The angle is called the Compensating angle.
• Casts may be removed from the articulator and returned to their original position with disposable mounting hinges. The articulator can be locked in centric relation position when casts are mounted and this remains constant even after changes of the posterior wall of the condylar guidance.
TELEDINE HANAU (MODEL 194) TPD 1995 VOL-74: As semi-adjustable instruments do not accept lateral records with fedility, the use of such in FPD treatment my result in restorations with occlusal errors in patient with immediate side shifts. For same reason semi-adjustable instruments produce errors in balanced occlusion when used for complete dentures. Features: The Hanau modular articulator system 194 was recently introduced with modification of the condylar mechanism by incorporating the curved component of movement to the immediate side shift. This permits the working condylar element to follow a curved path as it shifts laterally. Study: It has been reported that semi-adjustable articulators do not accept lateral interocclusal records from all patients. The Hanau model 194 was introduced to develop occlusion with minimal error. This study investigated the acceptability of lateral interocclusal records. 60 lateral interocclusal records were made for 30 edentulous subjects and the acceptability of the records was evaluated by use of the split cast mounting procedure. Out of 60 records, 52 records (87%) were accepted by this articulator. Different Studies: Whip mix: 40 out of 50 Hanau 4-2: 39 out of 56. WHIP MIX ARTICULATORS The whip mix articulator and quick mount face bow were introduced by Dr. Charles Stuart in 1963. His main objective was: (1) Aid in the teaching of principles of occlusion, for better diagnosis of the occlusion of natural teeth.
(2) To
provide
simplified
instrument
for
fabrication
of
prosthodontic restorations. Advantages: (1) The whip mix articulator and face bow permit the user to quickly and easily mount casts. (2) The registrations are simple to make, takes less time and because of this it has led to world wide acceptance. Normal Features: (1) Intercondylar distance is adjustable S(96mm) , M(110mm) and L(124mm) by means of removable condylar guidance spacers along the instrument’s horizontal axis. (2) Horizontal condylar inclinations are set by means of lateral or protrusive interocclusal records. (3) Amount of Bennett movement is set by lateral interocclusal records. (4) The upper and lower members are mechanically attached by means of spring latch assembly. MODEL 8300: • This reflects the work of Lundun with Lee and others. • The condylar guides have ¾” curved superior walls and a medial wall, immediate side shift adjustment from 0-4mm with a progressive angle of 6 degrees. • Condylar locking pin is there and condylar elements are fixed at 110mm. MODEL 8340: The model 8340 has been modified and the casts are interchangeable between articulators through a special fixture called as “accumount” with which a special mounting plate table is precisely attached to the lower frame. The relationship is then checked to verify precise alignment between upper and lower frames.
MODEL 8800: This provides an additional ½” space to mount the maxillary cast. This is more suitable in situations with extremely steep plane of occlusion or where osseus defect exists in the maxilla. MADEL 9000: Similar to 8800 except the lower frame is ½” taller to provide more space for mounting the mandibular cast. MODEL 9800: Combines the upper frame of model 8800 with the lower frame of model 9000 to provide the greatest distance between the upper and lower frames. These models can have condylar locking screws which can be positioned against condylar elements to permit only hinge action and helps in mounting procedures. Models with this feature are designated as 8500 A, 8800 A, 9000 A and 9800 A. DIFFERENT MODELS : 8500 : • Original model. • The condylar elements on the lower frame are adjustable to 3 positions. • Intercondylar distance can be adjusted between 96 mm, 110 mm, and 124 mm. • The condylar guides in the upper frame are aligned with the condylar elements of the lower frame by either removing or adding appropriate amount of spacers on the shaft of condylar guides. • The condylar guides can be adjusted fro 0-70 degrees horizontal condylar inclination. The medial walls are adjustable from 0-45 degrees to progressive side shift, posterior walls are straight.
• Guide table: The articulator is available either with an adjustable mechanical guide table or a flat or a dimpled plastic incisal guide table. PANADENT ARTICULATORS • Panadent system is the latest approach to dental instrumentation and is based on the work of Lee and others. • The panadent articulator was introduced in 1978 by Robert Lee and current models were introduced in 1983. • It is an arcon with fixed intercondylar distance 110 mm. • It utilizes interchangeable preformed curved analog fossae for condylar pathway which were developed from research which demonstrated that the lateral condylar pathways were quite similar in curvature except for steepness of the horizontal condylar inclinations and the amount of immediate side shift. • The progressive side shift varied from 5-7 degrees generally with an average of 6 degrees. • Fossae analogs are available with average lateral pathways and immediate side shifts from 0.5 – 2.5 mm. • Lateral interocclusal records or the Axi-path recorder are utilized to determine the amount of side shift and the steepness of the horizontal condylar inclination. • The latest modification is Dynalink panalock mechanical latch which keeps the upper and lower articulator frames joined together, yet permits an opening movement of 180 degrees. This linking mechanism can be disengaged when separation of upper and lower frames is desired.
• 3 models are available SL, PSL & PCL. The later two models are machined to with in0.01 mm accuracy that permits the interchanging of mounted casts between different articulators. • PSL model has a less complicated straight incisal guide pin as does the SL model. • Both a plastic and an adjustable metal incisal guide table are available with all 3 models. Selection of and Analog : • Quick analyzer tracing exraoral device is used to determine condylar path inclination. The analyzer is used to plot the condylar pathways and register the amount of side shift, then appropriate analog are selected and inserted in the articulator. The analog fossae is then rotated to duplicate the slope of pathways. • Different analogs can be mixed for each side if different amount of side shift is present. • The analogs and their angulation can be determined with positional lateral records. TMJ ARTICULATORS • They were designed by Kennath Swanson and introduced in 1965. • It allows condylar inclinations adjustment from 10 – 55 degrees and progressive side shift adjustment of 0-35 degrees. • The superior wall has a 3 degrees slant which produce ‘FISHER ANGLE’ when the mediotrusive pathway portion is steeper than the protrusive pathway. • The incisal guide pin is curved with both a plastic and an adjustable mechanical incisal table. • A mechanical guidance fossa accessory is available and can be easily inserted in the articular fossa housing.
• A series of 5 pre made fossae analogs are available with curvilinear superior surfaces based on average from an analysis. Hinge opening of the locking device is 115 degrees. • Each set contains pairs of fossae with inclinations of 28,35,40, 45 and 50 degrees in different colours for easy identification. Each analog has a 0.5 mm pre current side shift with a 7 degree progressive angle. Additional side shift can be created. A simplex mandibular movement indicator is available to record the condylar pathway inclination and the amount of side shift. • Selection of analogs is made from the recordings. • Custom analog fossae are formed from intraoral stereographic tracings and is called as stereographix. • Blank fossae boxes are filled with acrylic resin and curvilinear guidance paths and side shift are produced. • The articulator has a spring latch to return upper frame to centric relation position. • Mini-articulator : Smaller version, the intercondylar distance is limited from 110-150 mm and has straight incisal guide pin. All other features are same. • Advantages : TMJ articulators have the capabilities to meet the instrumentation needs for al types of prosthodontic procedures. Pair of adaptors is available for use of ear bows. DENAR ARTICULATORS DENAR – D5A: In 1968 Dr. Miles Guichet introduced the Denar 4A articulator and recording system. The current model is D5A, which is refined model of original model.
Features : • Adjustments to the guidance surface are possible in 3 planes of space. • The side shift adjustment is in the medial wall and has provision for both immediate and progressive settings. • A pre current insert is available for the medial wall and nylon or acrylic resin inserts are available for the superior wall. • An adjustable metal incisal table and a custom incisal plat form are available. Adjusting the foot of the incisal pin, allows movement in the articulator to develop an area of occlusion in centric relation. • The incisal platform can be used to hold self-curing acrylic resin adjusting the horizontal and vertical overlap of the anterior teeth. • Denar reference plane locater and marker is useful for locating the anatomical landmarks, posterior and anterior reference points. • Pantronic – A digital recorder is available in which the condylar guidance settings are automatically determined. • Advantage – Saves time and effort needed to manually transfer the recording and to program the articulator. DENAR MARK II : • Introduced in 1975 and developed to satisfy the undergraduate needs of education for a simpler arcon articulator. • Condylar elements are fixed at 110 mm intercondylar distance. Adjustable intercondylar distance (110 – 120 mm) is also available. • The horizontal condylar inclinations can be adjusted from 0 – 60 degrees. • Has an immediate side shift (Bennett) adjustment of 0 – 4mm plus progressive shift adjustment of 0 –15 degrees.
• The posterior fossae wall is inclined posteriorly 25 degrees to allow backward movement of rotating condyle as it shift outward during lateral side shift. • Straight rear wall is a option. • Features : Positive locking mechanism to hold the two members, permit 85 degrees of hinge movement. • All Denar articulators except Omni can be standardized to 0.001” of accuracy to each other by means of a field inspection gauge. OMNI • Arcon instrument. • Meet the requirement of both fixed and removable prosthodontics. • Has interchangeable open and closed track fossae. • When articulator is equipped with the open fossae, which are identical to Mark II fossae and a positive centric latch, it is called the Omni Mark. • When closed screws are utilized it is called as Omin Track. Features : • Fixed intercondylar distance of 110 mm. • Slidematic, ear piece and fascia face bows can be used . • Can be used with any Denar incisal pin – mechanical or plastic incisal table. • Omni Mark and Omni Track are adjusted with excursive interocclusal records. • Omni mark fossae are adjusted as Mark II. • Omni track has horizontal condylar inclination and progressive side shift adjustments but no immediate side shift adjustments. • Disadvantages : Cannot be standardized with the field inspection gauge.
Cyberhoby fully adjustable articulator : The cyberhoby computer pantograph developed by Hobo and Takayama in 1983 is one of the electronic pantographs that measures protrusive and right and left eccentric movements by means of a small optoelectronic sensor fixed to maxilla. The sensor used in the computer pantograph is light weight and easily used in patients since the condylar path data is computed for transferring the measurement, apparatus is not necessary with the computer pantograph system. MAINTENANCE : • Avoid getting wax or stone in the screw holes • Tighten screws but not too tightly. • It is always better to use a carrying case when the articulator is carried to and from the lab. Dropping the articulator may result in bent or broken parts which may effect the articulator’s ability to accurately reproduce a patient mandibular movements. • Using caustic stone, failure to remove excess stone or not keeping the articulator clean may result in corrosion of articulator surfaces. • A thin film of lubricant as in Whip mix- Whip mix lubri plate should be applied to the surfaces upon which the condylar elements move to provide a smooth action of these parts.
CONCLUSION: Numerous articulators are available for the
fabrication of dental
restorations. Some are very simple in design with limited movements, while others are very complex with numerous attachments and adjustments. There is a considerable controversy as to which articulator is ‘best’ for a particular dental procedure. Often, this controversy becomes quite emotional, to the point where strong allegiances to a particular instrument and its recommended technique are developed. Yet, the success or failure of final restoration is more dependent on the operator of the articulator than on articulator itself. 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.” So for conventional complete dentures, mean value articulator can be used. In complex cases, where balancing is required, anatomical articulators should be used. In RPD, semi-adjustable articulators are preferred. In FPD, use of simple hinge articulators may lead to occlusal discrepancies in the final restoration which has to be corrected later in mouth, so it is time consuming, so semi-adjustable articulators are preferred. Fully adjustable articulators are indicated when all the four quadrants are involved or in cases of full mouth rehabilitation when there is an abnormal deviation of mandible.
LIST OF REFERENCES: (1) Articulators-Charles.M. Heartwell (2) Relating the patient to articulator-Boucher-11TH Edition
(3) Essentials of complete denture prosthodontics-Sheldon winkler-2nd
edition. (4) Dental laboratory procedures: Fixed partial dentures – Vol II - Eissman, Rudd, Morrow. (5) A colour atlas of occlusion and malocclusion-A.P. Howat, N. J. Capp, N.V.J. Barrett;Ch.2 (6) Complete denture prosthodontics- John. J. Sharry. III edition (7) Osseointegration and occlusal rehabilitation-Hobo, Ichida, Garcia: I Edition. (8) History of Articulators – Journal of Prosthodontics Vol. 10 (1) Pg. 5260. (9) History of articulators – Journal of Prosthodontics Vol. 10(2) Pg 113121 (10) History of Articulators – Journal of Prosthodontics Vol . 10(3) Pg. 170-180.
(11) Does One articulator meet the needs of both fix and removable prosthodontics, JPD 1998, Vol. 54, Pg. 296. (12) A new semi-adjustable aticulator- JPD 1975, Vol. 33, Pg. 158. (13) Study of Acceptibility of lateral records by Whip Mix articulator, JPD 1977, Vol. 38, Pg. 22. (14) Modification of a Semi-adjustable articulator to accept the patient’s inter condylar width JPD 1982, Vol. 48, Pg. 385. (15) The Significance of articulator capability Part II, the prevalence of immediate side shift, JPD 1979, Vol. 42, Pg. 255. (16) Complete dentures using TMJ articulators, JPD, 1979, Vol. 41, Pg. 497. (17) Principles of articulation, DCNA, Vol – 23, Pg. 199. (18) Study of the acceptability of lateral interocclusal records by a modular articulator, JPD 1995, Vol. 74, Pg. 408 – 411. (19) Investigations of Arcon Instrument JPD 1956, Vol. 6, Pg. 359. (20) Glossary of Prosthodontic terms-VII Edition. (21) Contemporary Prosthodontics – Stephen F. Rosensteil-II Edition. (22) Fundamental of Fixed Prosthodontics – Shillingberg – III Edition.
ARTICULATORS (1) Introduction (2) History (3) Parts of articulator (4) Classification (5) Requirements (6) Uses (7) Advantages (8) Limitations (9) Selection of an articulator for complete denture (10) Arcon v/s Non-Arcon (11) Applications of simple hinge articulator (12) Applications of semi-adjustable articulator (13) Applications of fully adjustable articulator (14) Mean value articulator (15) Hanau articulator (16) Whip-mix articulator (17) Panadent articulator (18) TMJ articulator (19) Denar articulator (20) Omni articulator
Anatomical Articulators
(21) Cyberhoby fully adjustable articulator (22) Maintenance of articulators (23) Conclusion (24) List of references
