Facebow and Articulator PDF

Definition: It is a caliper like device. Definition: The face-bow is a caliper-like instrument used to orient the maxillary cast on the articulator so that it has the same relationship to the opening axis of the jaws. Orientation of the maxillary cast on the articulator so that it has t...

Definition: It is a caliper like device. Definition: The face-bow is a caliper-like instrument used to orient the maxillary cast on the articulator so that it has the same relationship to the opening axis of the jaws. Orientation of the maxillary cast on the articulator so that it has the same relationship to the opening axis of the jaws The terminal hinge axis (horizontal axis, transverse axis, inter-condylar axis) is an imaginary line around which the mandible rotates. This rotation averages about 12° or ranges between 10-25mm of incisal opening, and occurs in centric relation. It is assumed that the movement of the condyle during this early opening is pure rotation around this axis Pure rotatiours around the hinge axis till 10-25 mm of incisal separation Used to: 1- Record the relationship between the maxilla & the rotational axis (hinge axis) of the mandible. 2- Transfer the relation from the patient to the articulator. Accurately mounting the maxillary cast to articulator MANDIBULAR FACE BOW MAXILLARY FACE BOW I- Mandibular face bow or kinematic face bow: (Hinge axis face bow) Consists of: 1- U-shaped bow. 2-A clamp: attaches the bow to the mandibular occ.block. (fits under the chin and fixes the lower occlusion block in place). 3-Universal joint: attaches the clamp to the bow. 4-Two pointed condylar rods: attached to the bow. 5-Two Screws: adjust the position of the condylar rods. kinematic face bow Uses: v1- Locate the exact terminal hinge axis before using of maxillary face bow: –The patient is asked to open and close his mouth while in the most retruded position. – Each condylar rod will draw an arc on the paper attached to the skin. –The position of the condylar rods is adjusted toward the center of these arcs. –With further repetition, the size of the arcs drawn will progressively decrease, until the rods rotate in a point. –This point represents the terminal hinge axis of the condyles and is usually termed the "Still point". v 2- Record the centric relation. II- Maxillary face bow: Ø It consists of a U-shaped bow & a bite fork which is attached to the bow by a universal joint and a clamp. Ø A graduated condylar rod & a clamp at each end of the bow(posterior reference point) ØAnterior reference point (to fixed cranial third point reference ) II- Maxillary face bow (Arbitrary face-bow): A. Arbitrary face-bow Based on average location of the hinge axis They are a widely used type of face bow. It is used to record the relation of the maxilla to the hinge axis and transferring this relation to the articulator infra orbital pointer nasion pointer Methods of inter-condylar distance equilibration. (A) Calibrated condylar rod. (B) Anterior lock for a spring bow. (C) Slidematic facebow  Uses: 1- Determine the relationship between the maxilla and the hinge axis (open axis or axis of rotation) of the mandible 2- Transfer this relation to the open axis of the articulator ( To mount the upper cast ).  Definition: v It is a mechanical device that represents the T.M.J. & jaw members. v To which the maxillary & mandibular casts are attached  to simulate different mandibular movements. vThe primary function is to act as the patient in the absence of the patient. USES of an articulator: 1) To diagnose dental occlusal conditions in both the natural and artificial dentitions; 2) To plan dental procedure as they relate natural and artificial teeth to each other. 3) To aid in the fabrication of dental restorations and lost dental parts. 4) To correct and modify completed restorations. USES of an articulator: 5)Mounting dental casts for diagnosis and treatment planning. 6) Arrangement of artificial teeth. 7) Teaching and studying occlusion and mandibular movements.  Mounting the casts A laboratory procedure of attaching the maxillary and/or the mandibular cast to an articulator.  Advantages: 1- Better Visualization of occlusion  lingual aspect. 2- No need for Patient cooperation. 3- Decrease chair time and patient appointment. 4- The patient’s saliva, tongue and cheek are not factors when using an articulator.  Requirements 1. Able to open and close in hinge motion. 2. Preserve VDO (incisal pen). 3. Rigid , accurate and of non corrosive materials. 4. guidance adjustment should be able to move freely and be accurately secured. 5. Minimal weight , not bulky and stable on the bench. Classification of Articulators according to the records accepted : 1- Simple hinge articulators. 2- Mean value or fixed condylar path articulators. 3-Adjustable condylar path articulators: A-Semi adjustable articulators. B-Fully adjustable articulators. 1- Simple hinge articulators (plain line): vIt consists of an upper and lower members held at a certain distance by a screw which acts at the back. v The screw can increase or decrease the distance between the two members. e.g. Gariot's a. 1- Simple hinge articulators (plain line): vIt can open and close on a hinge movement. (Permitting only the hinge like movement) but cannot move in protrusive or lateral direction. vRecords accepted:  Centric occluding relation.  : e.g. ELMAHDY, Gysi simplex articulator v The articulators have upper and lower members, joined posteriorly by two condylar pillars. v Terminated with joints representing the temporo-mandibular joints. vThe condylar path is fixed at an average angle range from 30°- 40° to the horizontal plane. vThe lateral condylar angle is fixed at angle ranges from (12 - 20°). Movement allowed: Opening and closing Protrusion at a set angle Records accepted: 1- Bonwill triangle or face bow record  mounting the upper cast. 2- Centric occluding relation  mounting the lower cast.  BONWILL 1854 In Gysi articulator, the upper cast is mounted according to Bonwill triangle which is four 4” inch (4 inches ( nearly 10 cm.)) equilateral triangle extending posteriorly from one condyle to the other and joining the lower incisor's contact point anteriorly.  3- Adjustable articulators: This class of articulators differ from fixed condylar path articulators in that they can accept eccentric records used to adjust the condylar guidance. According to eccentric records accepted by these types of articulators, they are classified into: a. semi-adjustable. b. fully adjustable groups. 3- Adjustable articulators: a- Semi-adjustable articulator: e.g. Hanau (Model H) articulator Records accepted: vBonwill triangle or face bow record  mounting the upper cast. v Centric occluding relation  mounting the lower cast. vProtrusive record  adjust the horizontal condylar path. vHanau’s formula: used to  adjust lateral condylar guidance L = H/8 + 12 Where: L = Lateral condylar path. H = Horizontal condylar path. Movement allowed: Opening and closing Protrusion at an adjustable angle Lateral movement an adjustable angle  Non- Arcon Arcon “Non-Arcon articulator ” Non- An Arcon articulator is one in Arcon articulators, the condyles are which the condyles are attached attached to the upper member. to the lower member as they are in nature. Arcon articulator b- Fully-adjustable articulator: vBoth horizontal and lateral inclinations are adjusted  according to the records obtained from the patient. e.g. Hanau kinoscope. Records accepted: 1-Bonwill triangle or face bow record  mounting the upper cast. 2-Centric occluding relation  mounting the lower cast. 3-Protrusive record  adjust the horizontal condylar path inclination. 4-Right lateral record  adjust the left lateral condylar path inclination. 5-Left lateral record  adjust the right lateral condylar path inclination.