Articulation

Theories of articulation, basic provisions. Apparatus, reproducing the movements of the mandible. Principles of the articulators.

Anatomical setting teeth on glass. Setting teeth spherical surface. Setting individual teeth in occlusion curves.

 

     Definition of terms “articulation”and “occlusion” causes to many disagreements and discussions between dentists for many years. Concept “articulation” come from general anatomy, where it means  “joint, conjugation”. Full and correct definition of an articulation gives A.J.Katts (1931). He said that “articulation” it is different positions and mandible movements as concept in relation to top which are carried out by means of masseters and under CNS control.

 

 

Articulation – is a mutual relation of dentitions during mandible movements. 

Occlusion –  it is closing of dentitions in whole or separate groups of teeth throughout larger or smaller to an interval of time. Thus, the occlusion can be surveyed as the articulation special case. The forward occlusion is closing of dentitions during time moving out a mandible forward. The lateral occlusion is closing of dentitions during mandible shift aside. Distinguish three kinds of an occlusion: forward, lateral and central. Forward occlusion – it is closing of dentitions during time of moving out forward a mandible, lateral occlusion – closing of dentitions during mandible shift aside, definition of the central occlusion as initial and final moment of an articulation.

 

 

There is also a definition of the central occlusion as initial and final moment articulations (G.Myller). It is offered to define the central occlusion in case of an orthognathic occlusion as closing of teeth which are characterized at least by such four signs:

 1. Each top or bottom tooth is closed with two antagonists: top – with the bottom teeth (with the same and that behind), bottom – with an  upper teeth (with the same and that ahead). Exception  are an upper teeth of wisdom and the bottom central incisors which have only on one antagonist. 2. Middle lines between the top and bottom central teeth is continuation each other and located in one sagittal plane. 3. The top face-to-face teeth blocks bottom almost for 1/3 lengths of a crown of tooth (1,5-3 mm). 4. The top first molar, being closed with two bottom molar, blocks approximately 2/3 first molar and 1/3 the second. The bucco-medial hill of the top first molar gets in locking cleft between buccal hills of the bottom first molar.

 

 

 

Vertical movements answer not only for opening, but to closing of a mouth and are carried out thanks to a serial relaxation and reduction of muscles which lower and lift a mandible. Mandible lowering is carried out during active reduction of mylohyoid muscle, geniohyoid muscle, under condition of bracing of a sublingual bone by muscles which are more low from it. During mouth opening simultaneously with rotation of a mandible round an axis which passes through mandible heads in a cross-section direction, the last slip on a clivus of an articulate hill downwards and forward. During the maximum opening of a mouth of a head of a mandible settle down on a first line of an articulate hillock, in that case in different departments of a joint. If to part a way which there has taken place a mandible head rather to a clivus of an articulate hill (articulate a way) on separate pieces each piece will be answered with the curve. Thus, all way passed by any point, located, for example, on mental pleading, will describe not a correct curve, and a broken line which will consist of many curves.

      Sagittal movements of a mandible. Mandible movements forward are carried out by bilateral reduction of the lateral pterygoid muscles fixed on the one hand in fossas of pterygoid processes, from another – on a forward surface of a head of a mandible an articulate disk. Mandible movement forward can be parted on two phases. In the first phase the disk together with a mandible head slips on a surface of an articulate hill. In the second phase its hinged movement joins head sliding round own cross-section axis. The distance which there takes place a head of a mandible during mandible movement forward, has the name of a sagittal articulate way. It is characterized by the allocated angle – an angle of a sagittal articulate way.

      Lateral movements of a mandible. Lateral motions of a mandible result from reduction of a pterygoid muscle on the one hand. During jaw movement the right lateral pterygoid muscle to the left is reduced. In that case the head on the one hand rotates about the axis which goes almost upright downwards through a mandible branch. Simultaneously the head on the other hand together with a disk slips on a surface of an articulate hill. If the mandible moves, for example, to the right on the left side its head moves downwards and forward and from the right rotates round a vertical axis. Angle of a lateral articulate way. The mandible head on the party where the muscle was reduced, moves downwards, forward and (slightly) to the middle. Thus it overcomes a way at an angle to a sagittal line of the joint ways. Lateral movements are characterized by certain changes and occlusal contacts of teeth. As the mandible is constantly displaced that to the right to the left, teeth describes at this time curves which are crossed at an obtuse angle. The further from a mandible head there is a tooth, the the angle is more. The angle which is formed in a place of crossing of incisors, is the most obtusive. This angle is called as an angle of the lateral incisor ways, or a Gothic angle. It defines amplitude of lateral motions of incisors and equals 100-110 °. The great interest is caused by changes of mutual relation of chewing teeth during jaw lateral motions. During jaw lateral motions two parties distinguish: working and balancing. On the working party teeth faces the hills with the same name, and on balancing – heteronymic, that is buccal bottom hills face the top palatal.

Dynamic occlusion is sometimes called an articulation in former Soviet republics. Further in this paper we will use the term dynamic occlusion rather then articulation.

Occlusion is the relationship between the maxillary (upper) and mandibular (lower) teeth when they approach each other, as occurs during chewing or at rest. In other words occlusion simply means the contact between teeth. Contacts between the teeth when the mandible is closed and stationary may be defined as the static occlusion. Contacts between teeth when the mandible is moving relative to the maxilla as the dynamic occlusion.

Anatomic Considerations:

The mandible articulates with the skull at the tempromandibular joint. The condyle of the mandible fits into the mandibular fossa on the underside of the temporal bone, thus the name tempromandibular joint.

It is a synovial joint but differs from most synovial joints in that the articular surfaces of the bony components are covered with dense fibrous connective tissue, instead of hyaline cartilage. In addition, the TMJ has a fibrous articular disc, to which muscle fibers are attached. This disc divides the joint into two compartments, upper and lower, thereby giving the mandible a wide range of movement.

The possible movement of the lower compartment is a simple hinge movement, while that in the upper is a sliding movement. The mandible during its function moves in all the three planes of space (horizontal, frontal, and sagittal).

 

The sagittal, frontal, and horizontal planes of reference.

 

Mandibular movements can be classified as masticatory and non masticatory. The masticatory movements are necessary for introduction, grasping, crushing, grinding of food, and swallowing. The non masticatory movements include the movements used in speech, wetting the lips, as well as, habitual or abnormal movements such as bruxing, clenching or tapping of teeth together. The time spent each day for the non masticatory movements exceeds the time used in masticatory movements.

The mandible rotates in each of the three planes of space around centers of rotation (axes).

 

 

. Transverse axis. B. Sagittal axis C. Vertical axis.

Muscles:

Because the muscles that move the mandible are under voluntary control, these muscles can be directed to move the mandible in various directions.

There are powerful muscles, which elevate and rotate the mandible so that the opposing teeth may occlude for mastication.

Muscles of Mastication:

The muscles of mastication include the temporalis, masseter, and internal and external pterygoids. The first three of these are elevators. The fourth is a guiding muscle.

 

 

TEMPORALIS M.

 

 

The muscles of mastication when contracting are capable of applying a force over 400 Ib. between opposing molar teeth. This is very greatly reduced when artificial dentures are fitted because the mucous membrane cannot stand such pressure, a of 30 Ib never having been recorded.

The muscles of mastication develop their greatest power within a short range of normal vertical dimension

 

 

Besides the elevators (muscles of mastication), there are muscles of depression, that act to depress the mandible.

These muscles are the supra-hyoid muscles (diagastric, geniohy-oid, mylohyoid, and stylohyoid).

 

 

Muscles of depression.

 

shows the individual action of all the previously mentioned muscles.

 

 

 

 

Muscles of mastication.

 

Ligaments:

They act as passive devices to limit and restrict the mandibular movements.

Ligaments.

 

Ligaments

Basic Mandibular Movements

Mandibular movements are complex iature. Many different mandibular movements occur during function and parafunction. The dentist must understand the factors that regulate motion of the jaws. These include contact of the opposing teeth, the anatomy and physiology of the TMJ, the axes around which the mandible rotates the action of the muscles, ligaments, and the neuromuscular integration of all these factors. The dentist must relate an understanding of mandibular movements to their clinical application in the treatment of patients, particularly the edentulous.

Mandibular movements are usually classified according to the main direction of movement. The starting position is the habitual intercuspal position. From this pos -tion the mandible can: Open and close, move forwards (protrusive), move backwards (retrusive) and move sideways (laterally)

Habitual Intercuspal Position, is the complete intercuspation of the opposing teeth, independent of the condylar position.

1.     Opening and closing: (depression and elevation of the mandible):

The relation of the head of the condyle to the fossa

a-when the mouth is open, b – when the mouth is closed.

      This movement starts from the intercuspal position to the maximum opening position. At the beginning of the opening movement, there is a rotation in the lower compartment of the TMJ, with further opening a gliding movement occurs in the upper compartment. The condyles usually start to translate immediately when the teeth are separated from the intercuspal position. The first few millimeters of opening can be considered as a hinge movement. This movement is mainly produced by gravity and the contraction of the anterior belly of the digastric muscle.

For the closing movement, the mandible moves from the maximum opening position with a reverse movement back to the intercuspal position. Closing is brought about by the contraction of the masseter and the internal pterygoid muscles.

2. Forward movement: (Protrusion of the mandible):

The condyles together with their articular discs move as one unit downwards and forwards along the glenoid fossa and the articular eminence. The path travelled by the condyles in the protrusive movement is termed the sagittal condylar path. It forms an angle with the horizontal plane (occlusal plane) termed the sagittal condylar angle. It varies in individuals and also in the same individual from the left to the right sides. It ranges between 30°-40°. Protrusive movements are brought about by the contraction of the external pterygoid muscles on each side.

When the mandible moves forward to an edge to edge position a separation occurs distally between the distal arches or occlusion rims. This distal separation of teeth is the result of the forward and downward glide of the condyle on the articular eminence. This phenomenon is called Christensen phenomenon

 

3. Backward movement: (Retrusion of the mandible):

The retrusive movement of the mandible takes place by similar movements as the protrusive ones, but in the reverse direction i.e. upward and backward along the same inclination.

Starting from the intercuspal position, this movement is brought about by the contraction of the temporalis muscles.

Iatural dentition the mandible can move backwards to a slight extent. This most retruded position of the mandible is a strained position. It can be obtained by active conscious contraction of the retractors of the mandible (posterior fibers of the temporalis) or passively by the operator pressing on the symphysis menti when the patient is relaxed completely.

4. Sideways movement : (lateral)

The right and left lateral movements of the mandible from the intercuspal position and back again to the same position are asymmetric. When the mandible moves towards the right side, the condyle on this side rotates mainly with a very slight bodily lateral translation (Bennett movement). The condyle on the left side moves forward, downward and medially. The side towards which the movement occurs, is called the working side (w), the other side is called the non working, or the balancing side.

 

In summary protrusive movements are used in the grasping and incision of food, while the right and left lateral excursions are used for the reduction of fibrous, as well as, other types of bulky food. A combination of- all these movements appears to be the most effective in the trituration of food.

Mandibular movements are influenced by both incisal and condylar guidances as are other teeth dictations. The incisal guidance is the path performed by the forward glide of the incisal point from the habitual intercuspal position towards the edge to edge position. Although the incisal path is curved like the condylar path, for practical purposes it is considered straight. It is the path taken by the incisal edges of the lower incisors on the palatal surface of the upper incisors till the edge to edge position.

Significance of studying mandibular movements:

1.  Designing, selection, and adjustment of articulator.

2.  Developing tooth form for dental restorations.

3.  Understanding the basic principles of occlusion.

4.  Diagnosis and treatment of TMJ disturbances.

Articulators

Introduction

Functions

Advantages

Requirements

Classification

Class I Simple holding instrument

Class II Mean value articulator

Class III Adjustable condylar path articulator

Semi adjustable Fully adjustable

Introduction

The information obtained from the cast, occlusal rims and bases may be termed static information, but, the mouth is a dynamic system, therefore, some means should be available in the laboratory for converting static information into a dynamic form. This is done by mounting the cast on an instrument called an articulator.

An articulator is a mechanical instrument that represents the tempromandibular joints and jaws, to which maxillary and mandibular casts may be attached to simulate some or all mandibular movements.

 

Unlike the oral mechanism, the upper arm of the articulator moves and not the lower.

 

The articulator is so designed for ease of handling. Therefore, it will be seen that mandibular movements are translated into movements on the articulator shown in the following table:

 

Functions:

1.  The primary function of the articulator is to act as a patient in the absence of the patient.

2.  Articulators can simulate, but they cannot duplicate, all the possible mandibular movements.

3.  Mounting dental casts for diagnosis and treatment planning.

4.  Fabrication of occlusal surfaces for dental restoration.

5.  Arrangement of artificial teeth for complete and removable partial dentures.

It is often said that the mouth is the best articulator as the final test for a dental restoration is the occlusal

harmony obtained when the restoration is placed in the patient’s mouth. However it is mechanically impossible to perform intraorally many of the procedures involved in complete denture construction.

Advantages:

1.  Visualization of the patient’s occlusion especially from the lingual side.

2.  Patient cooperation is not a factor once the appropriate inter occlusal records are obtained from the patient.

3.  Considerable chair time and patient appointment time is saved.

4.  The patient’s saliva, tongue, and cheeks are not factors when using an articulator.

Requirements:

Minimal articulator requirements:

1.  The articulator must accurately maintain the correct horizontal and vertical relationship of the patient’s casts.

2.  The casts must be easily removed and attached to the articulator without losing their correct relationship.

3.  The articulator should have an incisal guide pin with a positive stop to preserve the patient’s vertical dimension.

4.  The articulator should be able to open and close in a hinge like fashion.

5.  The construction should be accurate, rigid, and of non corrosive material.

6.  The moving parts should resist wear. The adjustment should be able to move freely and be definitely secured. The articulator should be stable on the laboratory bench and not too bulky and heavy.

If dentures are to be fabricated with balanced occlusion, additional requirements are necessary:

1.  The articulator should accept a face bow transfer.

2.  The condylar guides should allow right lateral, left lateral, and protrusive movements.

3.  The incisal guidance should be adjustable.

Classification:

Articulators are classified according to the instrument capability and record acceptance into:

Class I:

Simple holding instruments:

Instruments in this class accept a single inter-occlusal record (centric relation) vertical motion may or may not be possible. The first articulator was a plaster slab articulator followed by a simple hinge articulator.

A. Plaster slab articulator: (Rrelator)

It was formed by extending plaster index from the rear of the casts. The casts were keyed to each other by means of their indices.

Plaster slab articulator

 

B. Simple hinge articulator: (Plane line).

 

A simple hinge articulator

Diagram to show the essential features of the simple hinge articulator. A, Hinge; B, Upper bow; C, Vertical stop mechanism; D, Lower bow.

This articulator produces the simple opening and closing movements of the TMJ. It consists of two bows united by a hinge and a posterior screw adjustment that can raise or lower the distance between the bows. Wear may take place at the hinge, introducing a lateral deflection. Some articulators incorporate means for adjustment to accommodate wear, and those devoid of this adjustment should be discarded once wear develops in the hinge.

The upper arm of the articulator should be parallel to the lower arm when the casts have been mounted. The casts are trimmed to allow for this.

The vertical dimension adjusting screw at the rear of the articulator is adjusted to allow the upper arm to lie parallel to the lower arm.

After mounting, the locking nut is tightened to prevent movement of the adjusting screw.

This type of articulator establishes static oral information and takes no account of the dynamic environment of the oral cavity. Its usefulness can be improved by the use of plaster pumice blocks where the patient grinds the lower rim against the upper until an even gliding contact is produced. Thus, shaping the surfaces of the rims to correspond with the path taken by the mandible in movement and then the teeth are arranged according to this path.

Class II:  

Mean value articulators.

Essential features of the mean value articulator. A, Condylar guidance mechanism; B, Upper bow; C, Incisal guide pin; D, Incisal guide plate; E, Lower bow.

 

The Gysi articulator. a, Upper bow; b, Lower bow; c, Condylar hinge; d, Movable incisal table; e, Mdline indicator;

 

These articulators have two jaw members, joined by two joints representing the TMJ. These articulators are capable of eccentric movement, but the condylar path here is fixed at a certain angle, which is the average for many patients. It ranges from 30°-40° from the horizontal. The incisal guidance may be fixed to an average or may be adjustable.

This type of articulator can be used with or without face bow record. The upper cast can be mounted either by face bow record or according to an average making use of the Bonwill triangle. On a dried mandible, if three lines are drawn to join both condyles and the tips of the lower central incisors, they will form a triangle. On the average, it is an equilateral triangle having 4 inch or nearly 10 cm sides.

Bonwill triangle makes an angle with the occlusal plane with an average of 15 degree called Bolkwill angle. This type of articulator has a pointer (Incisal indicator pin) attached to the incisal pin that locates the tips of the central incisors. This pointer is used during mounting to orient the cast to the opening axis of the articulator. It touches the midline of the occlusion rim labially and helps to orient the cast in relation to Bonwill triangle.

Unlike the oral mechanism the upper arm of the articulator moves and not the lower. It is so designed for ease of handling .Gysi and Mahdy articulators are representatives of this type.

Class III:  

Adjustable condylar path articulator.

This class of articulators differs from the fixed condylar path articulators in that they can accept eccentric records that are used to adjust the condylar guidance of the articulator.

According to the eccentric records accepted by these types of articulators, they are classified into :

 

Semi and fully adjustable condylar path articulator

 

Essential features of the adjustable articulator. A, Adjustable condylar mechanism; B, Upper bow; C. Incisal guide pin; D, Adjustable incisal guide plate; E, lower bow.

 

Hanau Articulator

A. Semi adjustable condylar path articulator:

This type of articulator can accept the following records:

1.  Face bow record to mount the upper cast.

2.  Centric occluding relation record to mount the lower cast.

3.  Protrusive record, to adjust the articulator’s horizontal guidance, that correspond to the patient’s horizontal condylar path inclination.

The lateral condylar guidance is adjusted according to the Hanau’s formula:

L = H/8+12

L: The lateral condylar inclination.

H: The horizontal condylar inclination.

An example of this type is Hanau model H articulator.

B. Fully adjustable condylar path articulators:

This type of articulators accept the following records:

1.  Face bow record to mount the upper cast.

2.  Centric occluding relation record to mount the lower cast.

3.  Protrusive record, to adjust the articulator’s horizontal condylar guidance which corresponds to the patient’s horizontal condylar path inclination.

4.  Right lateral record, to adjust the right lateral condylar guidance.

5.  Left lateral record, to adjust the left lateral condylar guidance. House, Phillips, and Hanau ki-noscope are representative of this type of articulators.

Another classification depends1 on the location of the condyle whether in the upper or lower member of the articulator.

 

Arcon articulator:

 

 

An acron articulator has condylar guidance similar to that in the skull.

In this type of articulator the condyles are. located on the lower member of the articulator and the condylar guidances are on the upper member. In this manner the condyles move in a relationship to their condylar guidance similar to the way the natural condyle moves in relation to the glenoid fossa.

The name is derived from the first letters of the expression articulator and condylar. (Arcon)

Non Arcon articulator:

Articulators of this type have the condyles on the upper member of the articulator and the condylar guidance on the lower member.For complete denture

construction there is no difference between the two types.

CLASSIFICATION OF ARTICULATORS. 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 thecondylar controls and the incisal point.It was also known as the theory of the equilateral triangle in which therewas a 4 inch (10cm) distance between condyle and between each condyleand the incisal point.It was designed by W.G.A. BonwillSince 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 theupper teeth as over the surface of cone, with a generating angle of 450 andwith 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 thisarticulator.

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). Thecenter of the sphere is located in the region of the glabella, and the surfaceof 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 maxillo-mandibular relationship from the patient to the articulator.1.Inter occlusal records2.Graphic records3.

Hinge axis recods.

Some articulators are designed for use with only one record where asothers 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 positionalrelationship 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 mandibleshould 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 dentureocclusion at the University of Michigan in 1972).

Class I :

Simple holding instruments capable of accepting a single staticrelationship.Vertical motion is possible, only for convenience. Eg. Slabarticulator, hinge joint articulator, barn door hinge.

Class II :

Instruments that permit horizontal as well as vertical motion but donot 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 usingengraving methods . eg. Howarth articulator, Dentograph.

Class III :

Instruments that simulate condylar pathways using average or mechanicalequivalents 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 useequivalents for the rest of motion. Eg. Hanau model H, DentatusBergstrom.

B)Instruments that accept static lateral, protrusive registrations and useequivalents 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 registrationsengraved by the patient . Eg. TMJ articulator.B)Instruments that have condylar paths that can be angled andcustomized either by selection from a variety of curvatures or bymodification 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 ineach of 3 planes. They are capable of reproducing the timing of the sideshift 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 hingemovement, 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 elementguidance by mean of averages, positional records of mini recorder systems.

Type 4 (Special) :

This type is designed to be used primarily for completedentures.

Examples :Class I :

Mccollum Gnathoscope.Granger Gnathoscope.Hanau KinoscopeCosmexStuart Gnathologic computer TMJ stenographicDenar D5A

Class II (Type 1) :

Barn Door hinge Stephen

Bonwill

Type 2 :

MonsonHandy IIThe Correlator TransographThe Gnathic relator Verticulator 

Type 3 :

HouseDentatusHanau (several models)WhipmixDenar – mark II and OmnimodelTMJ – mechanical fossa & molded fossa models.

Panadent

Type 4 :

Stransberry tripodKile dentographIrish Dupli – functional

CLASSIFICATION BY VARIOUS AUTHORSV. 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 spatialrelationship and occlusal arrangement of artificial teeth, so maynot 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 noncorrosive material.-The patient casts must be easily removable and attachable to thearticulator without loosing their correct horizontal and verticalrelationship.-The design should be such that there is adequate distance betweenthe upper and lower members and that vision is not obscured fromrear.-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 bowtransfer 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 theteeth similar to those in the mouth.

Other uses :

a)To diagnose dental occlusal conditions in both natural andartificial dentitions eg. If patient has TMJ problem. b)To plan dental procedures that involve positions, contours andrelationships of both natural and artificial teeth as they relate toeach other.c)To aid in fabrication of dental restorations and lost dental parts.d)To correct and modify completed restorations eg. In castedcrown.e)Can be helpful in teaching and studying of occlusion andmandibular movements.

ADVANTAGES :

It is often said that, “The patient’s mouth is the best articulator”. Thevery fact that the final test for a dental restoration is the occlusal harmonyobtained when the restortion is placed in the patient’s mouth. But stillmechanical 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 theappropriate interocclusal records are obtained from the patient.3.The refinement of complete denture occlusion in the mouth isextremely difficult because of shifting denture bases and resiliency of the supporting tissues. After obtaining interocclusal records, thecomplete denture occlusion can be refined outside the mouth on anarticulators.4.Chair time and patient appointment time is required when utilizingthe mouth as an articulator.5.More procedures can be delegated to auxillary personnel whenutilizing an articulator for development of the patients occlusion.

6.The patient’s saliva, tongue & cheeks are not factors when using anarticulator.

LIMITATIONS :

An articulator is a mechanical instrument made of metal.

The articulator is subject to error in tolling and errors resultingfrom 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 whounderstands the construction and purpose, the anatomy of the joints,their movements and the neuromuscular system, precision andaccuracy in registering jaw relations and the sensitivity of theinstrument to record these.

SELECTION OF AN ARTICULATOR FOR COMPLETE DENTURE.

The large number of different designs of articulator are availablewhich leave the dentist quite confused as to which one to choose. Thechoice 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, thena simple hinge articulator can be selected.If denture teeth are to have cross arch and cross tooth balancedocclusion, then minimum requirement is semi adjustable e.g. Hanau or Whipmix.If complete control of occlusion is desired, a completely adjustable, 3dimensional articulator is selected. These complicated articulators posesome problems for use in making complete dentures because of the

resiliency of the soft tissues of the basal seat on which recording bases mustrest.As the resiliency permits some movement of the bases in relation tothe bone, the records made are not necessarily records of the true pathmovement of the bone.According to clinical experience and testing, recommendation of theHanau model 130 – 28 and Whip mix articulators is made on the NorthAmerican continent.

According to a survey in U.S dental schools:

Out of 81 articulators, 67 were arcon design.

Commonly used articulators were Whip mix, Hanau 158, Hanau H-2and 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 ARCONArcon 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 beendiscussed by Beck (1956) and by Weinberg (1963) among others. Weinbergconcluded that the arcon and non arcon type produce the same guidance.Beck states that the constant relation of occlusal plane and arcon guidesexists 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’sarcon articulator & overdentures fabricated in Hanau H.

Advantages of Arcon :

Since the relationship of the condyles and condylar guidances issimilar as that of glenoid fossa in skull, visualization and understanding of condylar movement is easier.

Arcon V/s Non Arcon :

The term was coined by Bergstrom.

In “Arcon” principle mechanical feature is the attachment of theequivalent condylar guides to the upper member of the articulator.

The term condylar will be applied to the instruments whoseequivalent condylar guides are attached to lower member of theinstrument.

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 wherecondylar joint distance is adjustable)3)The symphyseal angle is about 135 degrees.4)The incisal guide table is in the same relative position, and adjustablein A-P direction.

The feature incorporated in Bergstrom arcon articulator which varyfrom 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 toupper member of arcon instrument and has convex curvature of 0.022mm.

3)The Bennett angle is fixed at 15 degrees

CONCLUSION

1)By fixing condylar guide to upper member of arcon articulator, andthe shaft axis to lower member, a constant relationship exists betweenthe 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 protrusiveinterocclusal record since few factors influence the setting of guide paths.3)In condylar articulator, setting of condylar inclinations by a protrusiveinterocclusal record is influenced by variety of factors like magnitudeof 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 jointdistance 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 occursduring 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 itsexcursion down one path to a movement in which it gradually movessideways as it goes down the path; this relation of side shift lateralexcursion 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 customgroove 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 duringlateral 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 theorbiting condyle.

2) Immediate side shift :

Mandibular side shift in which orbitingcondyle moves essentially straight medially as it leaves centricrelation.

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 theorbiting condyles as it leaves centric relation.

4) Disturbed side shift 

Mandibular side shift in which the greatest rateof side shift is distributed throughout the first 4 mm of forwardmovement of the orbiting condyle as it leaves centric relation.

Applications of simple hinge

Permit only a simple hinge opening around a horizontal axiswhose distance from the casts is orbitarily determined and less thanthe 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 anapproximation of true mandibular movements are acceptable when adequateanterior guidance is present. When guidance is reduced, it becomes morecritical to use an instrument which mirrors the movements more exactly sothat the occlusal anatomy may be reproduced in the laboratory to createintercuspal position, contacts yet disclude in other positions.If restorations are made on semi adjustable articulators, the occlusaladjustment needed in lateral excursion becomes progressively lessacceptable. 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 opposingteeth in complex cases, with minimal anterior guidance or group functions.They enable the cusps and grooves to be positioned correctly with respect tothe direction of lateral and protrusive movements and will greatly reduce theamount of occlusal adjustment required when restorations are tried in themouth.

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 bycondylar guide to occlusal plane in average individual. Anterior part of theupper member is supported by incisal guide rod through upper and incisalguide table on lower. The angle of incisal guidance is about 100 to 150

.For mounting, according to Bonwill concept, an incisal guidance rodand 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 completedenture 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 guidancemechanism and horizontal condylar guide can be adjusted from – 40to + 80 degrees (Horizontal condylar inclination set by protrusiverecords)4.The (lateral guidance side shift) adjustments can be adjustedfrom 0-20 degrees.This was calculated by Hanau in formulaL = H/8 + 12L = Lateral condylar angle in degrees.H = Horizontal condylar inclination in degreesThe derivative for this equation are not known and so the validity isquestionable since large changes in the horizontal condylar inclination angle will result in only a few degrees change in the sideshift 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 controlsattached 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 toreceive 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 isadjustable both in sagittal and frontal planes (Single sagittal, right andleft 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 bowtransfer.

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 bymeans 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 pinwhich 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 isadjusted by lateral interocclusal records.

Horizontal inclinations are set as in H2.

If adjustable axis face bow is to be used, then the articulator must beequipped with extendible condylar shafts as in H2.

HANAU WIDE VUE (Models 183 & 184) :

The Hanau wide VUE I and Hanau Wide VUE II are newestarticulators.

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 allowsupper member to be removed. Wide VUE II has condylar retainersto avoid accidental separation of upper member.

A micrometer protrusive – retrusive condylar adjustment isavailable which is accurate to 0.05 inch.

Horizontal condylar angle is adjustable from –20 to +60 degrees andside shift angle adjustment is from 0 – 30 degrees (same as H2). Thestraight incisal guide pin or with adjustable foot is available.

The straight pin has dual ends – chiesel and spherical and extendsabove the upper member to act as a third point stability wheninverting the articulator for mandibular cast mounting.

3 incisal guide tables are available: mechanical, flat and pantacrylictable.

HANAU RADIAL SHIFT (MODEL 166):

First produced in 1981.

Arcon, intercondylar distance is 110mm, right and left centriclatches, 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 curvedimmediate side shift (radial shift) with adjustable progressiveBennett angle of 0-60 degrees.

The radial shift adjustment has 3mm radius and allows up to3mm of radial shift.

The condylar guidance is adjustable horizontally and has acurved superior wall with 0.75 inch radius.

A straight incisal guide pin or an incisal guide table withadjustable foot is available –mechanical, flat and pantacrylictable are available.

THE 130 UNIVERSITY SERIES130-21 MODEL:

Arcon, used for occlusal corrections.

Intercondylar width adjustment from 94-150mm.

Split vertical and lateral compound axis permits adjustmentfrom -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 byloosening 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, lateraladjustment 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 theBennett guides, horizontal condylar guides and an adjustable posterior wall which can be adjusted to the position of theworking side condyle in lateral movement. When adjusted, thewall contacts and forms a guiding position for the working sidecondyle further, the posterior wall combines to compensate for the lack of an intercondylar distance on the articulator. Theangle is called the

Compensating angle.

Casts may be removed from the articulator and returned to their original position with disposable mounting hinges. Thearticulator can be locked in centric relation position when castsare 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 withfedility, the use of such in FPD treatment my result in restorations withocclusal 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 introducedwith modification of the condylar mechanism by incorporating the curvedcomponent of movement to the immediate side shift.This permits the working condylar element to follow a curved path asit shifts laterally.

Study:

It has been reported that semi-adjustable articulators do not acceptlateral interocclusal records from all patients. The Hanau model 194 wasintroduced to develop occlusion with minimal error. This study investigatedthe acceptability of lateral interocclusal records. 60 lateral interocclusalrecords were made for 30 edentulous subjects and the acceptability of therecords was evaluated by use of the split cast mounting procedure. Out of 60records, 52 records (87%) were accepted by this articulator.

Different Studies:

Whip mix: 40 out of 50Hanau 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 andeasily 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) andL(124mm) by means of removable condylar guidance spacers alongthe 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 meansof spring latch assembly.

MODEL 8300:

This reflects the work of Lundun with Lee and others.

The condylar guides have ¾” curved superior walls and amedial wall, immediate side shift adjustment from 0-4mm witha progressive angle of 6 degrees.

Condylar locking pin is there and condylar elements are fixedat 110mm.

MODEL 8340:

The model 8340 has been modified and the casts are interchangeable between articulators through a special fixture called as “accumount” withwhich a special mounting plate table is precisely attached to the lower frame. The relationship is then checked to verify precise alignment betweenupper 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 occlusionor where osseus defect exists in the maxilla.

MADEL 9000:

Similar to 8800 except the lower frame is ½” taller to provide morespace 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 helpsin 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 thecondylar elements of the lower frame by either removing or addingappropriate amount of spacers on the shaft of condylar guides.

The condylar guides can be adjusted fro 0-70 degrees horizontalcondylar inclination. The medial walls are adjustable from 0-45degrees to progressive side shift, posterior walls are straight.

Guide table: The articulator is available either with an adjustablemechanical guide table or a flat or a dimpled plastic incisal guidetable.

PANADENT ARTICULATORS

Panadent system is the latest approach to dental instrumentation andis based on the work of Lee and others.

The panadent articulator was introduced in 1978 by Robert Lee andcurrent 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 whichdemonstrated that the lateral condylar pathways were quite similar incurvature except for steepness of the horizontal condylar inclinationsand the amount of immediate side shift.

The progressive side shift varied from 5-7 degrees generally with anaverage of 6 degrees.

Fossae analogs are available with average lateral pathways andimmediate side shifts from 0.5 – 2.5 mm.

Lateral interocclusal records or the Axi-path recorder are utilized todetermine the amount of side shift and the steepness of the horizontalcondylar inclination.

The latest modification is Dynalink panalock mechanical latch whichkeeps the upper and lower articulator frames joined together, yet permits an opening movement of 180 degrees. This linkingmechanism can be disengaged when separation of upper and lower frames is desired.

3 models are available SL, PSL & PCL. The later two models aremachined to with in0.01 mm accuracy that permits the interchangingof mounted casts between different articulators.

PSL model has a less complicated straight incisal guide pin as doesthe SL model.

Both a plastic and an adjustable metal incisal guide table are availablewith 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 pathwaysand register the amount of side shift, then appropriate analog areselected and inserted in the articulator. The analog fossae is thenrotated 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 positionallateral records.

The NEW Hanau Ulti-Mate is extremely lightweight, can tilt back on the bench at a 45° angle, and has unique magnetized fossae.  This economically priced articulator was designed for simplicity and efficiency with a fixed Bennett angle of 15° and fixed 30°Protrusive angle, with a curved linear path. 

Features & Benefits:

• Protrusive Angle Fixed at 30 Degrees & Built-In Bennett Angle of 15 Degrees – Designed to work with average patient population.

• Unique Magnetized Fossae – For instant positioning of condyle to hinge position.

• Innovative Centric Lock Pins – Relate the upper member to hinge axis access.

• Ability to tilt the instrument back at a 45 degree angle – For hands free, table-top viewing.  Great for removable Technicians.

• Removable Upper Member – Permits greater accessibility.

• Lightweight and Durable – Easy to handle and clean!

• Optional: Disposable mounting plates available in quantities of 10, 50 or 100/ package. Inquire for pricing.

• Compatible with the Hanau Spring Bow

HANAU-MATEｮ articulator is a non-adjustable, arcon-type instrument which is ideal for laboratories and teaching facilities interested in a low-cost, easy-to-use average-type articulator for single crown and minimal unit bridge fabrications.

·         Non-adjustable (fixed), Arcon-Type Articulator.

·         Built-in average Bennett Angle of 15 degrees to more closely simulate the human anatomy. This will permit fabrication of teeth to more exacting cusp to fossa relationships than possible with plain line articulators. Helps attain better fit and reduced chair time.

·         Removable upper member to speed wax ups. Two locks are easily loosened to separate the maxillary part of the articulator. The locks return the case to “centric” position.

·         he clinician will feel a well-balanced, smooth motion when moving the case through lateral and protrusive movements to achieve the proper occlusion.

·         Excellent Lingual Visibility. Free, open access from the rear to observe the occlusion.

·         The condylar guidance has a 30 degree inclination and lateral excursions are possible to 15 degrees.

• Semi-Adjustable, Arcon-type modular articulator. 

• Complex computer-machined, Radial Shift curvatures are already carved into the fossae. They guide the casts forward, downward and inward simultaneously much like the motion found iatural anatomy. 

• The Modular Articulator permits you to select guidances which will help you achieve optimum cusp/fossae harmony.

• The feature of the curved 19mm (3/4″) radius simulates average anatomical movements. 

• Two different types of incisal guides are available: One for use with fast setting acrylic; the other guide is adjustable anteriorly/posteriorly and laterally.

• Precision machining allows transfer of casts from one Modular Articulator to another. 

• Positive Centric achieved with our new Snap Latch Lock. 

The following Modular Articulators are equipped with Adjustable Incisal Guides; Dual-End Incisal Pins on a Fixed Width Frame measuring 110mm between Condyles. They are equipped with Track Locks (Positive Centric Latches) which may be adjusted to a closed position to prevent upper and lower frames from separating accidentally. Condylar Inclinations may be adjusted from 0 degrees to 90 degrees.