ARTICULATORS INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
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Basic Out Line Need for articulators Definition, classification, parts, advantages, disadvantages of articulators Definition, classification, parts, advantages, disadvantages and purpose of face bow transfer Mean-value articulator, parts, measurements. www.indiandentalacademy.com
ARTICULATORS Articulator is defined as, "A mechanical device which represents the temporomandibular joints and the jaw members to which maxillary and mandibular casts may be attached to simulate jaw movements" GPT Uses of an Articulator •To diagnose the state of occlusion in both the natural and artificial dentitions. •To plan dental procedures based on the relationship between opposing natural and artificial teeth.. •To aid in the fabrication of restorations and prosthodontic replacements. . •To correct and modify completed restorations. •To arrange artificial teeth. www.indiandentalacademy.com
Requirements of an Articulator Minimal Requirements . It should hold casts in the correct horizontal relationship. . It should hold casts in the correct vertical relationship. . The casts should be easily removable and re attachable. . It should provide a positive anterior vertical stop (Incisal pin). . It should accept face足bow transfer record using an anterior reference point. . It should open and close in a hinge movement. . It should be made of non足corrosive and rigid materials that resist wear and tear. . It should not be, bulky or heavy. . There should be adequate space present between the upper and lower members. . The moving parts should move freely without any friction. . The non足moving parts should be of a rigid construction. www.indiandentalacademy.com
Additional Requirements •The condylar guides should allow protrusive and lateral jaw motion. •The condylar guide should be adjustable in a horizontal direction. •The articulator should be adjustable to accept and alter the •Bennett movement. •The incisal guide table should be customizable
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Advantages of Articulators . Properly足mounted casts allow the operator to visualize the patient's occlusion, especially from the lingual view. . Patient cooperation is not a factor when using an articulator once the appropriate inter足occlusal records are obtained from the patient. . The refinement of complete denture occlusion in the mouth is extremely difficult because of shifting denture bases and resiliency of the supporting tissues. This difficulty is elimi足nated when articulators are used. . Reduced chair time . The patient's saliva, tongue and cheeks are not factors when using an articulator.
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Limitations of an Articulator . An articulator may be made of metal or plastic. Metal articulators show errors in tooling (manufacture) or errors resulting from metal fatigue. . The articulator may not exactly simulate the intraborder and functional movements of the mandible. . Errors in jaw relation procedures are repro足duced as errors in the denture occlusion. Arti足culators do not have any provision to indicate or correct these errors. www.indiandentalacademy.com
Classification Several classifications of articulators were pro足posed. The most popular methods of classifying articulators are: . Based on the theories of occlusion. . Based on the type of inter足occlusal record used. . Based on the ability to simulate jaw movements. . Based on the adjustability of the articulator.
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Articulators Based on Theories of Occlusion Bonwill theory articulators According to the Bonwill's theory of occlusion the teeth move in relation to each other as guided by the condylar and the incisal guidances. Bonwill's theory is also known as the Theory of equilateral triangle according to which, an equilateral triangle is formed between the two condyles and the incisal point. Theore足tically, the dimension of the equilateral triangle is 4 inches Bonwill articulators allow lateral movement and permit the movement of the mechanism (joint) only in the horizontal plane. www.indiandentalacademy.com
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Conical theory articulators. The conical theory of occlusion proposed that the lower teeth move over the surfaces of the upper teeth as over the surface of a cone, generating an angle of 45Âdegrees with the central axis of the cone tipped 45° to the occlusal plane. The Hall automatic articulator designed by RE Hall follows the conical theory of occlusion. www.indiandentalacademy.com
RE HALL ARTICULATOR BASED ON CONICAL THEORY
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Spherical theory articulators ď Ž
The spherical theory of occlusion proposed that lower teeth move over the surface of upper teeth as over a surface of sphere with a diameter of 8 inches
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The centre of the sphere was located in region of glabella. The surface of sphere passed through the glenoid fossa and along with the articulating eminences.
The
articulator
devised
by
C.S.
Monson operatedwww.indiandentalacademy.com on the spherical theory of occlusion
ARTICULATOR BASED ON SPHERICAL THEORY
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Disadvantages of articulators based on theory of occlusion These articulators are based on theo-retical concepts. There is no provision for varia-tions from the theoretical relationships that occur in different persons.
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Articulators Based on the Type of Record Used for Their Adjustment Articulators are specifically designed to accept different jaw relation records. Based on the type of record accepted by the articulator, they are classified as: Interocclusal record adjustment Most articulators are adjusted by some kind of interocclusal records. These records are made of base plate wax, Plaster of Paris, zinc oxide eugenol paste or cold cure acrylic resin. www.indiandentalacademy.com
Graphic record adjustment ď Ž
Graphic records consist of records of the extreme border
positions
of
mandibular
movements.
These articulators are capable of accurately reproducing
the
border
mandible.
The
face
apparatus
(pantograph
movements
bow can
and be
of
the
Jaw-writing attached
to
transfer the records)
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Hinge-axis location for adjusting articulators: A transographic record can be used to record the accurate
location of the hinge www.indiandentalacademy.com
articulator.
axis
in
an
Based on the instrument's capability, intent, recording procedure and record acceptance. Class I: These are simple articulators capable of accepting a single static registration. Only vertical motion is possible. These articulators are used in cases where a tentative jaw relation is done, e.g. Slab articulator, Barn door articulator. Class II: These articulators permit horizontal and vertical movements but they do not orient the movement to TMJ with a facebow. •Type A: Limited eccentric motion is possible based on the average values. E.g.: MeanValue articulator •Type B: Limited eccentric motion is possible based on theories of arbitrary motion. E.g.: Monson's articulator, Hall articulator. •Type C: Limited eccentric motion is possible based on engraving www.indiandentalacademy.com
records obtained from the patient. E.g.: House's articulator.
Class III: These articulators permit horizontal and vertical movements. They do accept facebow transfer but this facility is limited. They cannot allow total customization of condylar pathways. These instruments simulate condylar pathways by using average or mechanical equivalents for the whole or part of the condylar motion. •Type A: They accept a static protrusive registration, and they use equivalents for other types of motion. E.g:Hanau H, Hanau II Bergstrom articulator. •Type B: They accept static lateral protrusive registration, and they use equivalents for other types of motion. E.g.: Panadent, Trubite ,Hanau university series. www.indiandentalacademy.com
Class IV; These articulators accept threedimensional dynamic registrations. They are capable of accurately reproducing the condylar pathways for each patient. They allow point orientation of the casts using a face-bow transfer.
Type A: The condylar path is determined by the engraving registrations
produced by the
patients. This path cannot be modified. E.g.: TMJ articulator.
Type B: They are similar to type A but they allow angulations and customization of the condylar path.
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Based on the Adjustability of the Articulator . Non足adjustable . Semi足adjustable . Fully足adjustable Non足adjustable articulators. They can open and close in a fixed horizontal axis. They have a fixed condylar path along which the condylar ball can be moved to simulate lateral and protrusive jaw movement. The incisal guide pins ride on an inclined plate in a fixed inclination. www.indiandentalacademy.com
Semi足adjustable articulators They have adjustable horizontal condylar paths, adjustable lateral condylar paths, adjustable incisal guide tables and adjustable intercondylar distances. The degree and ease of these adjust足ments differ. There are two types of semi足adjustable articulators: . Arcon articulators . Non足arcon articulators. www.indiandentalacademy.com
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Arcon articulators (Fig. 10.6) the term 'arcon' was derived by Bergstrom from the words articulator and condyle. E.g. Hanau University series and Whip-mix articulators.
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The condylar element is attached to the lower member of the articulator and the condylar guidance is attached to the upper member. This articulator resembles the temporomandibular joint. (Here, the condylar guidance is the mechanical analog of the glenoid fossa).
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Advantages of arcon articulators; The face-bow transfer, occlusal plane and the relationship of the opposing casts are preserved when the www.indiandentalacademy.com articulator is opened and closed.
HANAU SEMI ADJUSTABLE ARTICULATOR
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Non足arcon articulators .These articulators have the condylar elements attached to the upper
member. the condylar guidance is attached to the lower
member. This articulator is the reverse of the temporomandibular joint. Example; Hanau H series, Fully Adjustable Articulators They are capable of being adjusted to follow the mandibular movement in all directions. These articulators have numerous adjustable readings, which can be customized for each patient. They do not have condylar guidance instead they have receptacles in which acrylic dough can be contoured to form a customized condylar and incisal guidance. They are not commonly used due to their www.indiandentalacademy.com
complexity. E.g. Stuart instrument. Gnathoscope
FULLY ADJUSTABLE ARTICULATOR
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Mean Value Articulator It is a non足adjustable articulator. This articulator is designed using fixed dimensions, which are derived from the average distance between the incisal and condylar guidance of the population The condylar guidance (equivalent of glenoid fossa) is attached to the lower member and the condylar element (equivalent of the mandibular condyle) is attached to the upper member, hence, it is a non足arcon articulator.
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Upper member It is a triangular frame with the base of the triangle placed posteriorly. The apex of the triangle contains a provision to accom足modate the vertical rod (incisal pin). The vertical rod can be locked in position within the upper member with the help of a thumbscrew. Two condylar elements are seen projecting on either side of the base of the triangle. They arti足 culate with the condylar guidance of the lower member. The maxillary cast is attached to the upper member during articulation . www.indiandentalacademy.com
UPPER MEMBER OF MEAN VALUE ARTICULATOR
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Lower member It is a 'L' shaped frame with a horizontal and a vertical arm. The horizontal arm is triangular in shape. The apex of the triangle of the horizontal arm contains the incisal guide table. The vertical arm is rectangular containing the condylar guidance slot at the upper portion
A fixed metal bar (horizontal bar) is present in the vertical arm of the lower member. The plane of occlusion should coincide with this horizontal www.indiandentalacademy.com bar during articulation
Incisal guide table or anterior guidance of the articulator Incisal guide Table is defined as, "That part of the articulator which maintains the incisal guide angle" 足 GPT. The incisal guide table gives the incisal guidance of the articulator. The incisal guide table can be described as a very short cylinder whose upper surface is concave. The vertical rod should rest on the centre of the incisal guide table during articulation. The depth of the concavity is designed to have a slope equal to the average incisal guide angle The incisal guide angle is fixed and non足 customizable. www.indiandentalacademy.com
INCISAL GUIDE TABLE
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Condylar guidance; It is represented by a slot (condylar track) located on the upper part of the vertical arm of the lower member. The slot is inclined at an angle equal to the average inclination of the condylar guidance in the population. The condylar element of the upper member passes through this track. A spring is mounted within this track (condylar guidance) to stabilize the condylar elements and hold them in their posterior most position (centric relation) when no www.indiandentalacademy.com movements are made. This condylar guidance
Vertical rod or incisal pin It helps to keep a fixed distance between the upper and lower members at the anterior end. The vertical rod has a pointed tip, which should rest on the center of the incisal guide table during articulation. At the midpoint of the vertical rod a hole is provided to fit the incisal guide pin. The tip of the incisal guide pin is the anterior reference point in this articulator. The incisal edge of the maxil足lary incisors at the midline of the occlusal rim should touch the tip of the incisal pin during articulation The upper flat surface of the vertical rod should always be locked flush with the superior surface of the upper member.www.indiandentalacademy.com
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