Articulators and Face Bow PDF

# ARTICULATORS: ## Definition: - Mechanical device representing TMJ and jaws where: Maxillary & mandibular casts are attached at vertical and horizontal relations to simulate some or all mandibular movements used for construction of denture & other fixed restorations. * Vertical relation: vertica...

# ARTICULATORS: ## Definition: - Mechanical device representing TMJ and jaws where: Maxillary & mandibular casts are attached at vertical and horizontal relations to simulate some or all mandibular movements used for construction of denture & other fixed restorations. * Vertical relation: vertical dimension at jaw relation (detected first). * Horizontal relation: centric relation (detected second). ## Aim: - Transfer head of patient outside where ? ## Functions/Purpose/Uses: 1. Act as a patient in the absence of a patient. 2. Simulate, not duplicate, mandibular movements. 3. Arrangement of artificial teeth. 4. Evaluate possibility of achieving balanced occlusion or non-balanced occlusion. 5. Study occlusion & mandibular movement on computer/virtual/plasterless/digital articulators. 6. Mount cast for diagnosis & remount to correct prematurities. 7. Fabrication of occlusal planes for other dental restorations. 8. Correction & refinement of occlusal planes. 9. Hold both casts in a fixed predetermined relation (V.D). ## Advantages: 1. Better visualize occlusion from lingual side (help in setting teeth). 2. Patient saliva, cheeks, tongue & resiliency of mucosa are not a factor. 3. Patient cooperation is not a factor (once we obtained the records). 4. Lower chair time & appointments of the patient. ## Requirements of Articulators: - Necessary to fabricate dentures in centric position. ### Minimal (Basic) Requirements: 1. Open & close in a hinge-like fashion. 2. Maintain correct vertical & horizontal relations. 3. Casts are easily attached and removed (mount & demount & remount). 4. Should have incisal vertical post (incisal guid pin) with a positive stop to maintain the vertical dimension. 5. Has spaces (upper & lower to allow the plaster of mounting). 6. Must resist the wear (moving parts). 7. Must be rigid (non-moving parts). 8. Stable in a laboratory bench. ### Additional Requirements: * To achieve balanced occlusion. * Accept more records. * Increase the cost. 1. Accept face bow transfer. 2. Allow lateral & protrusive movements (accept lateral & protrusive records). 3. Adjustable incisal guidance. 4. Adjustable for Bennett movement. * Fully Adjustable articulator - It accepts 5 records so it's the highest type. ## Limitations of Articulator: 1. Show errors in construction/manufacturing (plastic/metal). 2. Not exactly simulate inter-border & functional movements except highly adjustable. 3. Just maintain the relation (not indicate the errors in jaw relation or occlusion). 4. Not accurate reproduction of hinge axis. 5. Maxilla is movable in the articulator while it's the opposite in a patient's mouth. ## Types of Articulators: * We classify the articulators according to: 1. Acceptance of records. 2. Fabrication. ### Classification According to Acceptance of Records: (According to adjustability of condylar guidance/condylar movements). The (5) records we make are: 1. **Face Bow Record:** explained later. 2. **Centric Inter-Occlusal Record**: "Centric record" detects the relation between maxilla & mandible. 3. **Protrusive Record:** detects horizontal condylar path/angle (we get it by Christensen's phenomena). 4. **Lateral Record (left & right):** detects lateral condylar angle/path (space of balanced side in lower lateral movement). The Classification: * **Class I: Simple (Simple Holding Instrument)/{Non-Adjustable}:** * **Class II: Mean Value/Average value/Fixed Condylar Guidance:** * **Class III: Adjustable Articulators:** * Semi-adjustable * Fully Adjustable ### Class I: Simple Holding Instrument/Non-Adjustable: 1. **Plaster Slab Articulator (Relator/Cast holder) by Philip "1756":** **Description**: Formed by extending plaster of the base of the cast at the rear of the cast. Keyed to each other by indices (projections & depression). **Movement**: Not allow movement in hinge movement (just holding) & maintain relation only. **Records**: Accept centric inter occlusal record only. **Note:** * It's not considered as an articulator, it's just a relator as it just relates inter occlusal record. * All articulators are relators, but not all relators are articulators. 2. **Simple Hinge Articulator (plane line)/Non-adjustable: "Gariot 1805"**: **Description**: Consists of 2 bows/metal frame united by screw posteriorly. The 2 bows are parallel even after mounting. * Screw holds two frames in a fixed vertical position. * It's used for Tor or V.D & detecting space (upper & lower). * Can adjust vertical dimension during the try-in of denture. * If found that vertical dimension is low or high by (1-2mm) as condyle rotate without translate within (1-2mm) at initial opening. * If wear occurs at screw (deffelction) so must be discarded. **Movement**: Allow open & close movement (vertical movement) in hinge-like fashion. **Records Accepted:** * **Occlusal Rim may be formed from:** 1. Centric inter occlusal record only. 2. Wax 3. Molding compound. 4. Plaster & pumice occlusion rim. * **Non-balanced occlusion:** 1. **Centric occlusion:** teeth in contact. 2. **Eccentric occlusion:** teeth not in contact. 3. **In natural teeth:** Condyle (incisal guide) 4. **In case of denture:** well developed ridge (for denture stability, eccentric occlusion) 5. **Balanced occlusion:** * Centric occlusion: teeth in contact. * Eccentric occlusion: teeth in contact. 6. **In case of flat ridge & thin mucosa to give denture stability during movement.** > **For denture stability during movement, we need to make plaster & pumice occlusal rim to set the teeth on the curve.** ## Class II: Mean Value/Average value/Fixed Condylar Guidance: **Description**: As in Bohrewells Triangle. * **Inter-condylar distance:** (10cm "4inch") * **Sagittal condylar guidance:** (30°) Average [30:33] * **Incisal guidance:** (10°) [10:15] **Movement:** * Allow opening & closing (vertical movement). * But limited (average) & not adjusted. * Eccentric (protrusive & lateral movements)/ not orient motion of TMJ (disadvantage). ## Class III: (Adjustable Articulator): **Description**: Curved forward and straight laterally. 1. **Semi-adjustable:** * Has adjustable condylar guidance curved forward (for protrusive record) but straight laterally. * Has adjustable incisal guidance. * Has adjustable condylar guidance curved forward (for protrusive record) but straight laterally. * Examples of semi-adjustable articulators: Whip mix articulator (Arcon)/Hanaue (Non-Arcon) 2. **Fully-adjustable**: * Has condylar guidance curved forward & lateral (can be in all directions). * Has adjustable Incisal guidance. * Examples of fully adjustable articulators: Denar articulator - All arcon types/Stewart articulator. **Movements:** 1. **Open & close** 2. **Eccentric movements:** Lateral/Protrusive 3. **Face Bow (upper cast)** 4. **Centric Record (inter occlusal record)** 5. **Protrusive Record** 6. **Lateral Record (Right/Left records)** **Records:** * **All records except lateral record:** 1. **Face Bow record** (upper cast). 2. **Centric (inter occlusal record)** 3. **Protrusive record.** (wax in the Christensen's phenomena) > We calculate the lateral condylar angle from: **Hanau equation:** L = H+12 (but can laterally move). * **Distance (condyles (inter-condylar distance))**: * Is not adjusted but fixed. **Disadvantage:** * **Note:** Can adjust the inter-condylar distance. **Hanau Quotient/Law of Articulation**: * We aim with both of them to get balanced occlusion. **CGXIGO-PXCHX.C.C** * **Another Classification to articulators according to position of condylar element (ball) and condylar shaft (groove):** > More simulating to the patient. ### Arcon (articulating condyle): * Condyle - upper member (fixed) * Shaft (groove) - lower member (moves) **Good simulation of patient (simulator)** * **Lower member moves (can study mandibular moves)** * **Constant relation () occlusal plane & condyle inclination**. * **Used for implants & fixed restorations (Accurate).** ### Non-arcon (non-articulating condyle): * Condyle - upper member (moves) * Shaft (groove) - lower member. (fixed) * **The reverse of the patient.** * **Upper member moves.** * **No constant relation.** * **Used for complete denture/RPD** **Easy control during teeth setting (moves)** ## Face Bow Record: **A-Maxillary Face Bow (Arbitrary):** * Each articulator has its specific face bow (Caliper-like device has U-shaped frame). * 2- condylar rods placed on condyle arbitrary anterior to tragus of the ear (11-13) mm beyond's point (100% of accuracy). * **Infraorbital pointer (3rd point of refrance)** - Give arbitrary hinge axis. * Bite fork placed in labial surface of occlusion rim, parallel to occlusal plane. * **Infraorbital pointer** placed at infra-orbital notch (or nose) as the third point of refrance. > 50: Condylar rods related to "condylar guidance" in articulaltor. * **Bite fork used to** mount upper cast. * **Infra orbital pointer** - 3rd point of refrance (each articulator has its own one). **Function:** * Used for cranio-maxillary orientation. **Transfer relation between maxilla and terminal hinge axis (arbitary) of patient with cranium where cranium is fixed to articulator (some of mean value/Adjustable).** * **Close & open on the same hinge axis of the patient on the articulator.** * **Record 3D location of maxilla with 3 points (2 condyles + Infraorbital point).** **Method**: 1. **Bite fork** is attached to upper record block 2mm above occlusal plane, then seated in patient mouth and stabilized by assistance of patient hand (disadvantage). 2. **Condylar rods applied to position of condyle** (arbitary) has equal degree on both sides by calculating the average (bite fork already in centric relation). 3. **Adjust the 3rd point of refrance/Indicator to its position** (Orbital or nasion). **Transfer face bow to articulator which accepts face bow record (Adjustable / some mean value) where:** * **Condylar rods** condylar guidance (Shaft / groove). * **Infra orbital pointer** Each Articulator has its own position. **Adjust position of bite fork with upper occlusion rim then mount upper cast (supported during mounting by anything under it).** **Have 2 types according to the position of condylar rods on patient:** 1. **Conventional (Faisa) face bow:** * We place condylar rods in ear, related to the external auditory meatus which the condyle is anterior to it by 5mm (arbitary). * The line () the 2 external auditory meatus is parallel to inter condylar distance / hinge axis. * **Advantages** 1. Accurate (because it is fixed). 2. Simple / most common. 3. Fixed location. * **Disadvantages:** 1. Arbitrary. 2. May lead to 0.2mm error in occlusion. > **We use ear piece/ Ear face bow to overcome the arbitrary hinge axis.** 2. **Mandibular face bow:** * **Condyle rod (placed at condyle) - condyle rod (attached to lower R.B)** * **Bite fork (attached to lower record) - ask patient to open and close (20-25mm) 50** **Function:** * Detect position of the condyle in terminal hinge axis (in centric relation) actual HA. * Aid in centric record. **Method:** 1. **Condyle rod placed at condyle at first.** 2. **Bite fork attached to lower record:** Ask patient to open and close (20-25 mm) so the condyle rotates without translate, then decrease the open gradually so the condylar tracing will draw smaller and smaller circles & curves. * **Till end with a point. ** * **This point refers to the actual position of the patient's condyle. ** * **And the line between the 2 points at each side is the actual terminal hinge axis.** > We used mandibular face bow to overcome the arbitrary hinge axis and get the actual hinge axis of the patient. **Disadvantage of mandibular face bow:** * Expensive and time consuming. * Need cooperation from patient. ## Types of face bow according to 3rd point of refrance: 1. **Infraorbital pointer:** applied to the lower margin of the orbit. 2. **Nasion:** applied to nasion position in face. ### Protrosive Record: * Set anterior teeth according to esthetics & phonetics. * Move protrosion till edge to edge. * Apply wax in the space (PC/HC/SC path). * Posterior are spaced (Christensen's phenomena). * Adjust horizontal condylar guidance at the same relation & close the screw. ### Lateral Record: * Set the teeth according to phonetics & esthetics. * Move Lateral (right/left) so the balanced side is spaced. * Adjust Lateral condylar guidance & close the screw. * We take the average value of the both Right/Left. ## Representation (Lateral condylar path) ## Classification of Articulators: * **According to records:** * Class I: Relator * Class II: Mean value * Class III: Semi-adjustable * **According to location of condylar element:** * Arcon * Non-Arcon * **According to theories of occlusion:** * Bonwill theory * Cone theory * Monson's sphere ### Class I: Simple Hinge. ### Class II: Mean Value ### Class III: Semi-adjustable ### Class III: Fully Adjustable ## Theories of Occlusion: * They are non-balanced occlusion * 1. **Bonwill Theory (Bonwill Articulator):** * Setting teeth within Bonwill triangle so the occlusion will be inside the A on the occlusal plane. * This articulator permits lateral movement. 2. **Cone Theory (Hall Articulator):** * Lower teeth move over the upper teeth as over the surface of the cone, generating an angle of 45° (occlusal plane) with the central axis of the cone. 3. **Monson Sphere (Monson Articulator):** * It's combination of both: Curve of Spee (when viewed from sagittal) & curve of Wilson (when viewed from frontal). * The sphere of Monson has it's center in the glabella. **Disadvantages of Articulators based on Theory:** 1. They are based on theoretical concepts. 2. Variations between different patients.