23- Facebow mounting (transfer) on a semi-adjustable articulator

Part 1: Components of Face bow & Semi-adjustable Articulator
Components of Face bow:
• Adjustable bow (arch) with screws to control inter-condylar distance.
• In some semi-adjustable articulators the inter-condylar distance is fixed to an average and can't be changed.
• Two ear pieces inserted in both external auditory meatus used as posterior points of reference.
• Nasion relator used as an anterior 3rd point of reference.
• There are 2 types of bite forks: (Dentulous or Edentulous)
• The edentulous fork used here attached just 2 mm below the occlusal plane
• The fork rod should be in the same line with the mid-line of the face and the mid-line oriented on the occlusal rims.
Components of the semi-adjustable articulator
• Upper member - Lower member - Hinge - 2 vertical posts - Mounting rings - Vertical guide post - Incisal pin - Incisal guide table (Plane or adjustable).
• Adjustable horizontal condylar inclination and adjustable Bennett angle.
• Accessories
1. Campers table: used for mounting of the upper cast instead of face bow.
2. Adjustable incisal guide table: Used to adjust both protrusive & lateral incisal guidance.
3. Fork support: Stabilize the bite fork during mounting of the upper cast.
4. Dentulous bite fork: Used in registering the cranio-maxillary orientation for dentate patients.
5. Elastic band: Used to maintain the vertical dimension of the articulator by holding both members firm during the setting of the mounting plaster.
Part 2: Mounting of the upper cast using face bow record
• Remove the Nasion relator from the face bow.
• Remove the vertical guide post from the articulator.
• Apply the face bow to the articulator by insert the ear pieces holes into the condylar pins (rods) then tight all face bow screws.
• Close the upper member to rest on the horizontal metallic plate of the face bow.
• The elastic band may be used to firmly hold the face bow in relationship to the articulator during the mounting procedure.
• Fork support applied to stabilize the bite fork.
• Apply the upper cast over the upper record block. Be sure that there is sufficient space for mounting plaster or trim the base of the cast.
• Scoring of the cast base is important in order to relate it again, if it is detached from the mounting plaster.
• Put a thin layer of Vaseline on the mounting rings. This will facilitate its removal from the mounting plaster after finishing the case.
• Scoring of the casts.
• Mix a small amount of plaster and apply it over the upper cast and some on the upper mounting ring.
• Close the upper member again and remove the excess plaster then wait until setting of the mounting plaster.
• Remove any excess plaster or add plaster to any deficient area.
• After setting of the mounting plaster you can now remove the fork support and the face bow from the articulator.
• Loosen the face bow screws then remove the ear pieces from the condylar rods.
• Attach the vertical guide post to the articulator so that the upper member parallel to the lower one.
• Remove the occlusal rim from the bite fork and seal it to the upper cast.
• The incisal pin is pointed to the mid-line and parallel to the occlusal plane.
• The magnetic mounting ring can be easily removed from articulator. This facilitate the setting procedure of artificial teeth away from the articulator.
Part 3: Mounting of the lower cast using centric relation record
• Seal the lower occlusal rim to the lower cast properly.
• Then seal the upper occlusal rim with the lower occlusal rim.
• Heals of the occlusal rims or the casts must not touch posteriorly.
• Mix a small amount of plaster to mount the lower cast to the articulator.
• Close the lower member over the mounting plaster, remove the excess plaster and add it to any deficient areas.
• The vertical post must touch the incisal guide table during and after setting of the mounting plaster.
• Elastic band used to hold both articulator members together to maintain the V.D.O. during and after the setting of the mounting plaster.
• After setting of the mounting plaster removes the elastic band. Now the articulator is ready for setting of the artificial teeth.
• The posterior lock of the articulator is used to limit the articulator movement to simple hinge opening like (Mean value articulator).
• Don't forget to tight the screw fixing the vertical post to maintain the vertical dimension of occlusion during setting of artificial teeth.