2. ARTICULATORS AND FACE BOW

3. Overview Introduction. Define the articulator. Discuss the requirements of an articulator. Classify different types of articulators. Define face bow. Discuss functions and different types of face bow. Discuss technique of use of face bow. Mounting

5. Articulator: A mechanical instrument that represents the temporomandibular joints and jaws, to which maxillary and mandibular casts may be attached to simulate some or all mandibular movements.

6. The articulator helps to maintain the desired maxillomandibular relationship of the casts during tooth arrangement. Thus, it makes it possible to arrange teeth in the absence of the patient.

7. Requirements of an articulator: 1. Accurately maintain centric position. 2. Provide a positive anterior vertical stop (incisal pin). 3. Should open and close in a hinge-like movement. 4. Should allow protrusive and lateral movement.

8. 5. The construction of the articulator should be accurate, rigid, and of non-corrosive material. 6. Moving parts should resist wear. 7. Should be able to receive face- bow transfer record.

9. Extra-requirements 8. Should have an adjustable horizontal and lateral condylar angle. 9. Should have an adjustable inter- condylar width of the condylar elements. 10. It should have a mechanism to accept a third point reference from a face-bow transfer record. 11. It should have an adjustable incisal guide table.

10. 1. Mounting dental casts for diagnosis and treatment planning. 2. Arrangement of artificial teeth. 3. Teaching and studying mandibular movements. Uses of an articulator:

11. Classifications of different types of articulators: Class I: a.Simple-Holding instrument. b.Simple-Hinge. Class II: Fixed condylar path (mean-value) articulators. Class III: Adjustable articulators: a.Semi-Adjustable. b.Fully-Adjustable.

12. Class I: Simple-Holding instrument. Simple-Hinge. Class I: Simple-Holding instrument. Simple-Hinge.

13. a.Simple-Holding instrument: A simple holding instrument capable of accepting a single interocclusal record (centric relation). A- Plaster slab articulator : (Relator): o Formed by extending plaster index from the rear of the cast. o The casts were keyed to each other by means of their indices.

14. b.Simple-Hinge or Plane-Line articulators This articulator produces the simple opening and closing movements of the TMJ. It consists of two bows united by a hinge and a posterior screw that can raise or lower the distance between the bows. Its use can be improved by the use of plaster pumice blocks where the patient grinds the lower rim against the upper until an even gliding contact is produced.

15. Class II: Fixed condylar path (mean-value) articulators. Class II: Fixed condylar path (mean-value) articulators.

16. Fixed condylar path (mean-value) articulator

18. Instrument that have two jaw members, joined by two joints representing TMJ. these articulators permit horizontal as well as vertical motion. It has fixed horizontal condylar guidance of 30º – 40º degrees from horizontal relation. It has fixed incisal guidance. It has fixed inter- condylar distance.

19. Adjustable articulators: a.Semi-Adjustable. b.Fully-Adjustable.

20. Adjustable Articulators a. semi-adjustable. b. fully adjustable groups. 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:

21. a. Semi-adjustable condylar path articulator: Semi adjustable articulators are designed to be adjusted so that the articulator movements will simulate the jaw movements of the patient.

22. This type of articulator can accept the following records: 1. Face bow (arbitrary) record to mount the upper cast. 2. Centric relation record to mount the lower cast. 3. Protrusive record, to adjust the articulator's horizontal guidance, that correspond to the patient's horizontal condylar path inclination. 4. The lateral condylar guidance is adjusted according to Hanau’s formula: L = H/8 + 12 a. Semi-adjustable condylar path articulator:

23. The condyle travels in a curved path in horizontal and lateral mandibular movements.(a) This is reproduced in semi-adjustable articulators as a straight path. (b) They have adjustable horizontal condylar guides while the lateral condylar path (angle) is calculated from the Hanau’s formula: L = H/8 + 12 a. Semi-adjustable condylar path articulator: L:lateral condylar angle H: horizontal condylar angle

24. a. Semi-adjustable condylar path articulator: Ex: Hanau model H articulator

25. b. Fully-adjustable articulators This type of articulator can accept the following records: 1. Face bow record to mount the upper cast. 2. Centric relation record to mount the lower cast. 3. Protrusive record, to adjust the articulator's horizontal guidance, that correspond to the patient's horizontal condylar path inclination. 4. Right lateral record to adjust the left condylar guidance. 5. Left lateral record to adjust the right lateral condylar guidance.

26. The following records are needed for mounting the casts on fully adjustable articulators: 1. A maxillary face bow record to mount the upper cast. 2. Centric occluding relation record to mount the lower cast. 3. Protrusive record to adjust the horizontal condylar path inclination. 4. Right lateral record to adjust the left lateral condylar path inclination. 5. Left lateral record to adjust the right condylar path inclination.

27. Another classification of articulators which depends on location of the condyle: A.Arcon articulators. B.Non-Arcon articulators.

28. ‘Arcon and Non-Arcon articulators’ The term ‘ARCON’ was derived from the words ARticulator and CONdyle.

29. An Arcon articulator is one in which the condyles are attached to the lower member as they are in nature. Arcon articulator

30. Eg: Whipmix condylar analogs.

31. “Non-Arcon articulator ” Non-Arcon articulators, the condyles are attached to the upper member.

32. E.g.: Hanau-H series Dentatus This articulator is the reverse of the TMJ. E.g.: Hanau-H series Dentatus This articulator is the reverse of the TMJ. “Non-Arcon articulator ”

33. Face bow 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.

34. Orientation of the maxillary cast on the articulator so that it has the same relationship to the opening axis of the jaws

36. Types of face bow A. Maxillary (Arbitrary) Face Bow:  Facial type.  Earpiece type. B. Kinematic Face Bow (Hinge Axis Face Bow).

37. 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

38. This face bow takes its name from the fact that it rests upon the face Facial -bow Types:

39. Facial -bow

40. Ear-bow This type of face bows uses the external auditory meatus as an arbitrary reference point which is aligned with ear pieces. Types:

41. Technique of use of face bow: 1. Seat the patient. 2. Adjust record blocks. 3. Locate the condyles (arbitrary by palpation).

42. Locating the ‘arbitrary’ Hinge Axis.

43. Average distance (11-13 mm) between the acoustic meatus and the terminal hinge axis (measured on an imaginary line from inner canthus of the eye and tragus of the ear).

44. 4.Center the face-bow on the patient’s face.

45. 5.Index (2 mm V-shape grooves) is made in the occlusal surface of the upper occlusal rim. 6.Separating medium application. 7.Adjust lower occlusal rim height and Prepare the fork.

46. Ear-bow is fitted to the external auditory meatus

47. 8.Heat the fork and embed it to the occlusal plane.

48. The fork is centered and parallel to occlusal plane

49. 9. Allow the patient to close against the lower wax rim to stabilize the record base.

50. 10. The face-bow is centered on the patient’s face, and tighten the thumb screws. 11. Release condylar indicator and remove the whole assembly. 12. Remove the skin pencil marks from the patient’s face.

51. The whole assembly including the upper and lower rims are transferred to the articulator. The condylar rods of the facebow are locked to the hinge axis extension on the articulator. Then, mounting procedure is started.

52. A laboratory procedure of attaching the maxillary and/or the mandibular cast to an articulator. Mounting the casts

53. 1.Indices are cut in The working casts for laboratory remount. 2.The face bow is used to record the relation of the maxilla to the hinge axis and orient the maxillary cast to the opening axis of the articulator in the same way as the maxilla is related to the condylar axis.

54. 14. The upper cast is then placed accurately in the trial denture base and attached to the mounting ring of the articulator with plaster. The face-bow is removed after the setting of plaster.

56. The mandibular cast is oriented to the lower member which represents the mandible by a relating the lower cast to the upper cast through a centric interocclusal record.

57. - Adjusting the Horizontal Condylar Guidance. It is adjusted by a protrusive record. - Adjusting the lateral condylar guidance (0 degrees to 30 degrees) L = H/8+12. - Adjustable Incisal guide table (0 degrees to 20 degrees) adjustments

58. Hassaballa M.: Clinical complete denture prosthodontics. KSU, 2 nd ed, 2010. The Glossary of Prosthodontic Terms: J.Prosthet. Dent. 2005 Jul;94(1):10-92. George A. Zarb et al.: Prosthodontic Treatment for Edentulous Patients: Complete Dentures and Implant- Supported Prostheses. Mosby; 12 th edition (2003).

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