بسم الله الرحمن الرحيم Articulator

Articulators: defined as a mechanical instrument that represents the tempromandibular joints and jaws to which the maxillary and mandibular casts may be attached to simulate some or all mandibualr movements.

To aid in fabrication of dental restorations and lost dental parts. Objectives: It should hold opposing casts in predetermined fixed relationship. It should open and close. It should be able to produce border and intra border movements of the teeth similar to those in the mouth. It should develop a prosthesis that will be harmonious in the oral cavity. Uses: Mounting of dental casts for diagnosis, treatment planning and patient education. To plan dental procedures that involve positions, contours and relationships of both natural and artificial teeth as they relate to each other. To aid in fabrication of dental restorations and lost dental parts. To arrange artificial teeth for complete and removable partial dentures. To correct and modify completed restorations.

Requirements of an articulators Minimal articulator requirements: It must be accurately maintain the correct horizontal and vertical relationships of patient casts. The patient casts must be easily removable and attachable to the articulator. It should have an incisal guide pin with a positive stop that should be adjustable and calibrated. It should accept a face bow transfer. It should be able to open and close in a hinge like fashion. The construction of articulator should be accurate, rigid and of a non corrosive material. The design of articulator should be such that there is adequate distance between the upper and lower members. It should be stable on the laboratory bench and not too bulky and heavy. |

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Additional Articulator Requirements These are required in cases of denture fabricated with balanced occlusion: The condylar guides should allow lateral and protrusive movements. Condylar guides should be adjustable horizontally. The articulator should have provisions for adjustment of Bennett movement. The incisal guide table should be customizable.

Classification: Based on the instruments function Class – I – Simple holding instruments capable of accepting a single static registration. Vertical motion is possible but only for convenience. Example: Hinge Articulator

Class-II Instruments that permit horizontal as well as vertical motion but do not orient the motion to the temporomandibular joint via a face bow transfer. 1. Class -II A Eccentric motion permitted is based on average or arbitrary values E.g. Grittman articulator. 2. Class - II B Eccentric motion permitted is based on theories of arbitrary motion E.g. maxilla mandibular instrument (Monson's Instrument) - Based on Monson's spherical theory of occlusion. 3. Class - II C Eccentric motion permitted is determined by the patient using engraving methods E.g. House articulator.

CLASS - III Instruments that simulate condylar pathways by using average or mechanical equivalents for all or parts of the motion. These instruments allow for joint orientation of the casts via a face bow transfer. For example: Instruments that accept a static protrusive registration and use equivalents for the rest of the motion. E.g. Hanau model H

CLASS -IV Instruments that will accept three dimensional dynamic registrations. These instruments allow for joint orientation of casts via face bow transfer. 1. Class - IV A The condylar paths are formed by registrations engraved by the patient. These instruments do not allow for discriminating capability. E.g. TMJ instrument by Kenneth Swanson. 2. Class - IV B Instruments that have condylar paths that can be angled and customized either by selection from a variety of curvatures, by modifications or both E.g. Denar articulator (D4A)

BASED ON THEORIES OF OCCLUSION 1. Bonwills Theory of Occlusion According to this theory, teeth move in relation to each other as guided by the condylar control and the incisal point. It is also known as the theory of equilateral triangle. E.g. Bonwills articulator. 2. Conical Theory of Occlusion According to this theory, lower teeth move over the surfaces of upper teeth as over the surface of a cone. E.g. Hall automatic articulator. 3. Spherical Theory of Occlusion According to this theory, teeth move over the surface of the upper teeth as over the surface of a sphere with a diameter of 8 inches. The centre of the sphere is located in the region of the glabella and the surface of the sphere passes through the glenoid fossa along the articulating eminences or concentric with them. E.g. Monson's maxilla mandibular instrument.

BASED ON PLANE OF REFERENCE 1. Campers Plane A plane established by the inferior border of the right or left ala of the nose and the superior border of the tragus of both ears. E.g. Kavo articulator. 2. F H Plane (Frankfort Horizontal plane) A plane established by the lowest point in the margin of the right or left bony orbit and the highest point in the margin of the right or left bony auditory meatus. E.g. Hanau articulator, dentatus articulator.

PARTS OF MEAN VALUE ARTICULATOR A. Upper member • It is a triangular frame (equilateral triangle) with base of triangle placed posteriorly and apex anteriorly. Each side of triangle measures about 110 mm. Parts: Condylar elements: Two condylar elements are present-one on either side of base of triangle posteriorly. They articulate with condylar guidance of the lower member. Vertical rod: It determines the anterior height of articulator. It should rest on center of incisal guide table during articulation. Thumb screw: Helps in fixing vertical rod to upper member. Incisal pin: It guides in placement of anterior teeth during teeth arrangement. Incisal edge of maxillary central incisors at the midline should touch the tip of pin during articulation. Retentive pin: Helps in retention of casts to the articulator.

PARTS OF MEAN VALUE ARTICULATOR (continued:) B. Lower member • It is a 'L' shaped frame with a horizontal and vertical arm. Parts: Horizontal arm: It is triangular in shape and corresponds to the upper- member. a. Incisal guide table-present at the apex of the horizontal arm anteriorly. It helps in establishing the incisal guidance by maintaining incisal guide angle. b. Retentive pin-helps in retention of casts to articulator. Vertical arm: It is triangular in shape and connects upper member to the lower member. a. Condylar guidance slots - present on the upper portion of both vertical arms. They guide the movement of condylar elements. b. Horizontal rod - it is present in vertical arm lower member. It should coincide with the plane of occlusion while articulation. c. Stabilizing rod.

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