Facebow 1

part 1 of facebow

1. FACEBOW BY: DR PALAK MISHRA MDS FIRST YEAR

2. CONTENTS PART -I Face-bow: Definition History and Evolution Value of Facebow Indications Types of Facebow Conclusion References PART- II Face Bow registration Face bow transfer and mounting on articulator Jaw relation in CAD CAM denture Conclusion References

3. DEFINITION Acc to GPT-9: An instrument used to record the spatial relationship of the maxillary arch to some anatomic reference point or points and then transfer this relationship to an articulator; it orients the dental cast in the same relationship to the opening axis of the articulator; customarily the anatomic references are the mandibular transverse horizontal axis and one other selected anterior reference point. 3

4. REVIEW OF LITERATURE Williams G.A. Bonwill (1860): determined the distance from the center of each condyle to the median incisal point and the lower teeth as 10 cm . Used this standard for mounting his casts in the articulator. Disadvantage : He did not mention at what level below the condylar mechanism the occlusal plane should be situated. 4

5. Francis H. Balkwill (1866): He demonstrated an apparatus to measure the angle formed by the occlusal plane of lower teeth & the plane passing through the condyles & incisal plane of lower teeth . Angle varied 22 degrees to 30 degrees. (approx 3.5cm) Also determined approx. distance from each condyle to the front of the gums. 5 Richmond S. Hayes (1880): He constructed an apparatus called Caliper with median incisal point localized in relation to the two condyles.

6. According to Prothero , Thomas L.Gilmer was the first to suggest the principle of a face bow in a paper presented at a meeting of the Illinois State Dental Society in 1882. Luce 1889 Introduced photographic method to reproduce the movements of mandible and to specifically trace the individual condylar pathways. Used 3 points : the condyle , the angle and symphysis to record the movements. 6

7. William E Walker (1890): He invented Facial Clinometer used to obtain the relative position of the lower cast in relation to the condylar mechanism. Disadvantage: Bulky and complicated George K Bagby (1894): He fabricated a device that determined the distance from the midline of the anterior occlusal rims to one of the condyles . Gysi (1895): He constructed an instrument for registering the condylar path & used as face bow also. 7

8. George B Snow (1899): He constructed simple instrument which has become prototype for all the face bows constructed in present days. Since the introduction of Snows apparatus, no fundamental changes have been made in the face bow design 8

9. Stansberry (1928): He was dubious about the value of face bow and adjustable articulators. He thought that since an opening movement about the hinge axis took the teeth out of contact the use of these instruments was ineffective except for the arrangement of the teeth in centric occlusion. Mclean (1937) He stated that the hinge portion of the joint is the great equalizer for disharmonies between the gnatho -dynamic factors of occlusion. When occlusion is synthesized on articulator without accurate hinge axis orientation, there may be minor cuspal conflicts, which must be removed by selective spot grinding. 9

10. Kurth LE, Feinstein IK (1951): With aid of articulator and working model, they demonstrated that more than one point may serve as a hinge axis and concluded that an infinite number of points exist which may serve as hinge points. Craddock and Symmons (1952): They considered that the accurate determination of the hinge axis was only of academic interest since it would never be found to be more than a few millimeters distance form the assumed center in the condyle itself. Sloane (1952): He stated “the mandibular axis is not a theoretical assumption, but a definite demonstrable biomechanical fact. It is an axis upon which the mandible rotates in an opening and closing function when comfortably, not forcibly retruded . 10

11. Bandrup-Morgsen (1953) : They discussed the theory and history of face bows. They quoted the work of Beyron who had demonstrated that the axis of movement of the mandible did not always pass through the centers of the condyles. They concluded that complicated forms of registration were rarely necessary for practical work. Lazarri (1955) gave application of Hanau model ”c” facebow . Sicher (1956) He stated “the hinge position or terminal hinge position is that position of the mandible from which or in which pure hinge movement of a variable wide range is possible” 11

12. Robert.G.Schallhorn (1957): He studied the arbitrary center and kinematic center of the mandibular condyle for face bow mountings. He concluded that using the arbitrary axis for face bow mountings on a semiadjustable articulator is justified. He said that, in over 95% of the subjects the kinematic center lies within a radius of 5 mm from the arbitrary center. Brekke (1959) In reference to a single intercondylar transverse axis, he stated “unfortunately this optimum condition does not prevail in mandibular apparatus, which is symmetric in shape and size, and has its condyloid process joined at the symphysis, with no connection directly at the condyles. 12

13. Christiansen RL (1959): He studied the rationale of face bow in maxillary cast mounting and concluded that it is advantageous to simulate on the articulator the anatomic relationship of the residual ridges to the condyles for more harmoniously occluding complete dentures. Weinberg (1961): He evaluated the face bow mounting and stated that a deviations from the hinge axis of 5mm will result in an anteroposterior displacement error of 0.2 mm at the second molar. Lucia VO (1964): He described the technique for recording centric relation with help of anterior programming device. 13

14. Teteruck and Lundeen (1966): He evaluated the accuracy of the earpiece face bow and concluded that only 33% of the conventional axis locations were within 6 mm of true hinge axis as compared to 56.4% located by ear face- bow. They also recommended the use of earpiece bow for its accuracy, speed of handling, and simplicity of orienting the maxillary cast. Trapazazano , Lazzari (1967) They concluded that, since multiple condylar hinge axis points were located, the high degree of infallibility attributed to hinge axis points may be seriously questioned. 14

15. Thorp, Smith, and Nicholis (1978): They evaluated the use of face bow in complete denture occlusion. Their study revealed very small differences between a hinge axis face bow Hanau 132-sm face bow, and whip mix ear- bow. Neol D.Wilkie (1979) He analyzed and discussed five commonly used anterior points of reference for a face bow transfer. He said that not utilizing a third point of reference may result in an unnatural appearance in the final prosthesis and even damage to the supporting tissue. He suggests the use of the axis– oribitale plane because of the ease of making and locating orbitale and therefore the concept is easy to teach and understand. 15

16. VALUE OF THE FACEBOW A.D. Gritman gave the statement : the implement devised by Prof. Snow as a bow of metal that reaches around the face. The face-bow is also a convenient instrument for supporting the casts while they are being attached to the articulator” : hence the term “FACEBOW” Failure to use facebow can lead to errors in occlusion of denture. In cases of cusp teeth used, or if interocclusal record are made with the teeth out of contact so the vertical separation of the casts or dentures must be reduced on the articulator, the facebow record is essential. 16

17. Allows more accurate arc of closure on the articulator. An integral part in analyzing and studying the occlusion of natural teeth and also in fabrication of CD and other prosthodontic restorations. Desirable to make a inter- occlusal record at a minimum increased VD of occlusion even with a face bow record. 17

18. INDICATIONS Under following conditions: When cusp form teeth are used. Balanced occlusion in eccentric position is desired. A definite cusp fossa or cusp tip to marginal ridge is desired. Interocclusal check record are used for verification of jaw position. The occlusal VD is subject to change and the alterations of tooth occlusal surfaces are necessary to accommodate the change. When there is significant error in anteroposterior , lateral and vertical relations. 18

19. Accurate mounting of casts in the articulator, both in relation to the position of condyles and to certain points on the head. Other indications include full mouth rehabilitation, diagnostic mountings, gnathological studies, occlusal corrections after denture processing. 19

20. TYPES OF FACEBOW 20

21. ARBITRARY FACE BOW The hinge axis is approximately located in this type of face bow . It is commonly used for complete denture construction . This type of face bows generally locate the true Hinge axis within a range of 5mm. Uses arbitrary or approximate points on the face as the posterior points and condylar rods are positioned on these point . As the located hinge axis is arbitrary, occlusal discrepancies produced in the dentures should be corrected by minor occlusal adjustments during insertion. 21

22. FASCIA TYPE The fascia type of face bow utilizes approximate points on the skin over the temporomandibular region as the posterior reference points . These points are located by measuring from certain anatomical landmarks on the face. The hinge axis or the posterior reference point is 13mm anterior to the external auditory meatus and the anterior reference point is the orbitale . 22

23. The facebow has a pointer that can be positioned to the posterior reference point. Disadvantage: As the face bow is placed on the skin which is movable there is a tendency for the condylar rods to displace. Also requires an assistant to hold the face bow in place. 23

24. EAR PIECE TYPE It uses the external auditory meatus as an arbitrary reference point which is aligned with ear pieces similar to those on a stethoscope. Accurate relationship for most diagnostic and restorative procedures. Posterior reference point is EXTERNAL AUDITORY MEATUS and anterior reference point is ORBITALE . The earpiece engage into the posterior reference point. 24

25. Advantage: Simple to use. Do not require measurements on face. As accurate as other face bows. It provides an average anatomic dimension between the external auditory meatus and horizontal axis of mandible. Disadvantage : Regardless of which arbitrary position is chosen an error of 0.2 mm from the axis can be expected. When coupled with the use of a thick inter occlusal record made at an increased vertical dimension. This factor can lead to considerable inaccuracy. 25

26. Articulators whose programming make use of arbitrary Ear bow type face bows feature an artificial correction whereby the position of the bow, which should be placed behind the actual hinge axis, is moved forward by about 11-13 mm, or rather by the average distance between the acoustic meatus and the terminal hinge axis. Further classified into- Spring Bow Twirl Bow Slidematic Whipmix quick mount 26

27. SPRING BOW (HANAU’S FACE BOW) It is an earpiece face bow made of spring steel and simply springs open and close to various head widths. Most commonly used face bow. This instrument is designed to orient the occlusal plane to the Frankfort horizontal plane by means for a third point of reference. It is indicated in cases when it is critical to precisely reproduce the exact opening and closing movement of the patient to the articulator. 27

28. ADVANTAGES : The one piece design of bow eliminates the moving parts and maintenance problems encountered with other models. Easy and efficient to use. Sterilazable parts. Direct/indirect mounting capability . DISADVANTAGE : Expensive Rarely indicated for routine articulators with prosthodontic procedures. Inability to measure inter condylar distance. Extensive chair side assistance is required. 28

29. TWIRL BOW It is an earpiece type of face bow. Allows the maxillary arch to be transferred to the articulator without physically attaching the face-bow to the articulator. Relates the maxillary arch to FH plane. 29

30. SLIDEMATIC FACE BOW Type of ear piece Face bow. Used with Denar articulator. It has an electronic device that gives reading denoting one half of the intercondylar distance. 30

31. The Slidematic face-bow uses the external auditory meatus for determining the arbitrary hinge axis location. A built-in reference pointer aligns the face-bow with the horizontal reference plane. The anterior reference point is marked on the patient's right side using the Denar reference Plane Locator. 31

32. WHIP MIX FACE BOW Ear piece type of face bow. It has a built in hinge axis locator. Automatically locates the hinge axis when the ear pieces are placed in the external auditory meatus. Has a nasion relator assembly with a plastic nose piece. 32

33. It is indicated when it is critical to precisely reproduce the exact opening and closing movement of the patient to the articulator. DISADVANTAGE: Extensive chair side. Expensive Rarely indicated for routine articulators with prosthodontic procedures. 33

34. KINEMATIC FACE BOW It is used to determine and locate the exact hinge axis points. Hinge axis of the mandible can be determined by a clutch i.e., a segmented impression tray like device attached onto the mandibular teeth with a suitable rigid material such as impression plaster. 34

35. INDICATION : When it is critical to precisely reproduce the exact opening and closing movement of the patient to the articulator . DRAW BACKS : Extensive chair side. Expensive Rarely indicated for routine articulators with prosthodontic procedures. 35

36. VIRTUAL FACEBOW The Virtual Facebow has been developed as an advancement of open-source tablet application that provides an alternative option to the conventional facebow for the mounting of maxillary casts to an articulator. The Virtual Facebow implements several design features that helps to minimize errors, provides accurate mounting and reinforces the anatomical considerations associated with articulators. The Virtual Facebow is an effective, efficient and accessible digital companion to dental diagnoses and treatment planning. Praveen P , Ragavendra Jayesh ; Facebow European Journal Of Molecular & Clinical Medicine Issn 2515-8260 Volume 7, Issue 4, 2020

37. To support proper mounting of patient casts, a face bow, which aligns the maxilla to relative cranial planes, can be utilized. The virtual facebow was developed to locate the maxillary digital cast of the patient in a cranial coordinate system. The Virtual Facebow has been developed as a digital substitute to the conventional facebow to address the shortcomings Praveen P , Ragavendra Jayesh ; Facebow European Journal Of Molecular & Clinical Medicine Issn 2515-8260 Volume 7, Issue 4, 2020

38. RECENT ADVANCES :KAVO ARCUS FACEBOW A fully functional 3-dimensional computerized pantographic registration system to capture both, static and dynamic occlusal records for articulator programming and diagnostic set-ups. Accuracy and repeatability are unsurpassed, with all records permanently archived 38

39. CLINICAL ADVANTAGES : Full mouth Reconstruction: Cosmetic and Implant . Diagnostic Wax-ups that are gnathologically correct . Articulator programming for TMJ derangements and functional disorders Splint therapy set-up . Orthognathic surgical treatment planning. 39

40. There are more advanced techniques that make use of ultrasonic arcs, connected to computers with graphical representations and parameter calculations for programming the articulator. 40

41. KINEMATIC VS ARBITARY KINEMATIC ARBITARY Locates hinge axis physiologically with exceptional accuracy Use of arbitary points to locate hinge axis Bite fork is attached to mandibular arch Attached to maxillary occlusal rims Require specific equipments Doesn’t require elaborate equipments, easy and quick Require skill and time consuming Practically more acceptable Detemine orientation relation and centric relation together Only determine orientation of maxilla Require stable record bases No attachment to mandible so exceptionally stable record base not required 41

42. TYPES OF HINGE AXIS FACE BOW There are true hinge axis bows which record both hinge axis and transfer of hinge axis to articulator in one instrument i.e. TMJ INSTRUMENT FACEBOW. Also a technique of recording hinge axis with hinge axis locator and after obtaining the hinge axis points. Transfer of hinge axis is done with hinge axis transfer bow. Both technique are acceptable. Latter is more precise and rationale. 42

43. HANAU MODEL C FACEBOW Adjusted to a point on the face i.e. 13 mm forward from the external auditory meatus on a line from the top of the tragus of the ear to the corner of the eye(outer canthus of the eye). Without clamping the condylar rods, the dentist must center the device so that equal readings are obtained on both sides, and the wing nut of the clamp is tightened to hold the facebow in place on the occlusal fork. 43

44. PARTS OF FACE BOW U shaped frame Condylar rods Bite fork Locking device Third Reference Point 44

45. U shaped arm Represents the plane of the cranium It forms the main frame of the face bow. All other components are attached to this frame. It extends from the region of TMJ on one side to the other side without contacting the face. 45

46. Bite fork Represents the plane of the maxilla. “U ” shaped plate, which is attached to the occlusal rims, while recording the orientation relation. It is attached to the frame with the help of a rod called the stem . The bite fork should be inserted 3mm below occlusal surface within occlusal rim 46

47. Condylar rods/ Ear piece Two small metallic rods on either side of the free end of the U shaped frame that Contact the skin over the TMJ. They are used to locate the hinge axis and transfer it to the articulator. Some face bows have ear piece that fit into the external auditory meatus instead of Condylar rods. 47

48. Locking device 48 Attaches the bite fork to the U-shaped frame Supports the facebow , occlusal rims & the cast during articulation. Consists of transfer rod and a tranverse rod. U shaped frame is attached to the vertical transfer rod

49. Third Reference Point 49 It is used to orient the face bow assembly to a anatomical reference point on the face along with the two condylar reference points. It varies in the different face bows, example orbital pointer- orbitale , Nose piece – Nasion etc.

50. PLANE OF ORIENTATION The maxillary cast in the articulator is the baseline from which all occlusal relationships start . Therefore it should be positioned in the space by identifying the three points of which two points are located posterior to maxillae and one point located anterior to it. The posterior points are referred to as the posterior points of reference and the anterior one is known as anterior point of reference . The spatial plane formed by joining the anterior and posterior reference points is called plane of orientation. 50

51. The horizontal plane is established on the face of the patient by 1 anterior and 2 posterior points, from which measurements of the posterior anatomic determinants of occlusion and mandibular motion are made. 51

52. ARBITRARY LOCATION OF HINGE AXIS POINT (POSTERIOR POINT OF REFERENCE): 52

53. Beyron’s point- It is located 13 mm anterior to the posterior margin of the tragus of the ear on a line from the center of the tragus to the outer canthus of the eye . 53 Shafiullah RS, Ravichandran M, Sundar MK, Kamakshi V. Posterior Reference Points: A Simplified Classification. J Sci Dent 2019;9(1):9–12.

54. Gysi’s point- It is located 10 mm anterior to the posterior margin of the tragus of the ear on a line from the center of the tragus to the outer canthus of the eye. Shafiullah RS, Ravichandran M, Sundar MK, Kamakshi V. Posterior Reference Points: A Simplified Classification. J Sci Dent 2019;9(1):9–12.

55. Bergstrom’s point- Located 10 mm anterior to the posterior margin of the tragus on a line parallel to and 7 mm below the Frankfort horizontal plane . 55 Shafiullah RS, Ravichandran M, Sundar MK, Kamakshi V. Posterior Reference Points: A Simplified Classification. J Sci Dent 2019;9(1):9–12.

56. Teteruck and Lundeen’s point- It is located 13 mm anterior to the base of the tragus on cantho-tragal line Experimental arbitrary axis point- It is placed 10 mm anterior to the superior border of the tragus on Camper’s line. External auditory meatus - On an average the external auditory meatus is 6 to 6.5 mm posterior and 2.5mm superior to the actual hinge axis point

57. Prothero's point : A line drawn from top of Richey condylar marker (placed in the external auditory meatus) to the outer canthus of eye. A point 13mm anterior to Richey condylar marker to this line is used as the arbitrary reference point. Weinberg's point: This is a point 11-13mm anterior to the reference line drawn from the middle and the posterior border of the tragus of ear to the corner of eye. 57 Shafiullah RS, Ravichandran M, Sundar MK, Kamakshi V. Posterior Reference Points: A Simplified Classification. J Sci Dent 2019;9(1):9–12.

58. Lauritzen and Bodner's point : A point 13mm anterior to the tragus on the tragus-canthus line . 58 Shafiullah RS, Ravichandran M, Sundar MK, Kamakshi V. Posterior Reference Points: A Simplified Classification. J Sci Dent 2019;9(1):9–12.

59. Swenson point: Described arbitrary location of the condyles as 11mm anterior to the meatus of ear on reference line from top of the meatus to the corner of eye. P.craddock and Symmon's point: A point 1cm anterior along a line drawn from the upper free margin of the tragus of ear to corner of eye.

60. ANTERIOR POINT OF REFERENCE 60

61. Orbitale - L owest point on the infraorbital rim, palpated through tissue and skin . O ne orbit and 2 posterior points determine the Axis-Orbital plane . It is used because of ease of location and the concept is easy to teach and understand. 61 REMOVABLE PROSTHODONTICS The anterior point of reference Noel D. Wilkie

62. CLINICAL IMPLICATIONS OF “ORBITALE” Orbitale and the two posterior landmarks defining the plane are transferred from the patient to the articulator with the face‑bow. The articulator must have an orbital indicator guide. Relating the maxillae to this plane will slightly lower the maxillary cast from the position that would be established if the Frankfort horizontal plane were used. 62

63. Practically, the axis‑orbital plane is used because of the ease of locating the marking orbitale and because the concept is easy to teach and understand. Orbitale is transferred from the patient to this guide by means of the orbital pointer on the anterior cross arm of the face‑bow 63

64. Orbitale minus 7 mm- F-H plane : porion-orbitale P orion is a fixed point on the skull it is considered as a posterior landmark . This posterior landmark on an average lies 7mm superior to the horizontal axis. 64 REMOVABLE PROSTHODONTICS The anterior point of reference Noel D. Wilkie

65. The recommended compensation for this discrepancy is to mark the anterior point of reference 7mm below orbitale on the patient or to position the orbital pointer 7mm above the orbital indicator of the articulator. 65

66. NASION MINUS 23MM- The nasion guide, or positioner , of the quick mount face bow designed to be used with the whip mix articulator fits into the depression . The crossbar is located 23mm below the midpoint of the nasion positioner . 66

67. When the face-bow is positioned anteriorly by the nasion guide, the crossbar will be in the approximate region of orbitale . The face-bow crossbar and not the nasion guide is the actual anterior reference point locator. During the face-bow transfer, the crossbar of the face-bow supports the upper frame of the Whip- Mix articulator. The inferior surface of the frame is in the same plane as the articulator’s hinge points. 67

68. INCISAL EDGE PLUS ARTICULATOR MIDPOINT TO ARTICULATOR AXIS-HORIZONTAL PLANE DISTANCE- Guichet has emphasized that a logical position for the casts in the articulator would be one which would position the plane of occlusion near the mid horizontal plane of the articulator . This technique does not relate the Frankfort plane or the axis orbital plane parallel to the horizontal plane. 68

69. In this, the distance from the articulator’s mid-horizontal plane to the articulator’s axis- horizontal plane is measured. This same distance is measured above the planned incisal edges on the patient, and its uppermost point is marked as the anterior point of reference on the face. 69

70. ALAE OF NOSE According to proponants of this point, occlusal plane parallels the Camper’s plane . So as a anterior point of reference ,right or left alae of nose is considered. 70

71. Advantages of anterior reference point Determines which plane in the head will become the plane of reference. Determines the level at which the casts are mounted. To establish a baseline for comparative studies between patient. Can visualize anterior teeth & occlusion in the articulator in the same frame of reference. 71

72. CONCLUSION Failure to use the facebow leads to error in occlusion. Despite lot of controversies in facebow usage, Hinge axis location and establishing the plane of orientation is an important component for recording mandibular movement. Facebow , a caliper like device, should accurately capture the hinge axis and transfer to the articulator whenever required. Face bow record helps in securing anteroposterior positioning of cast in relation to condyles . It also helps in achieving the exact anteroposterior or vertical positioning of cast in relation to condyles . The virtual facebow is a recent advancement technique developed to overcome the problem of transferring data from the patient simulation to the virtual articulators. The virtual technique can align digital casts directly onto the virtual articulator. This virtual facebow was developed to locate the maxillary digital cast of the patient in a cranial coordinate system.

73. REFERENCES Zarb G, Bolender CL, Carlsson GE. Boucher’s prosthodontic treatment for edentulous patients, ed 11th. St Louis, USA, CV Mosby Co. 1997. Heartwell CM, Rahn AO. Syllabus of complete dentures. Lea & Febiger ; 1986. Winkler S, editor. Essentials of complete denture prosthodontics . Year Book Medical Pub; 1988. Shillingburg HT, Hobo S, Whitsett LD, Jacobi R, Brackett SE. Fundamentals of fixed prosthodontics . Quintessence Publishing Company; 1997 Jan. Winstanley RB. The hinge‐axis: a review of the literature. Journal of oral rehabilitation. 1985 Mar;12(2):135-59. Kalavathy K, Ananthraj A, Premanth K, Kumar CS. Face bow a caliper-Review article. SRM Journal of Research in Dental Sciences. 2011 Jan 1;2(1):37. Craddock FW, Symmons HF. Evaluation of the face-bow. The Journal of Prosthetic Dentistry. 1952 Sep 1;2(5):633-42. Getz, E.H. et al. Application of a geometric principle for locating the mandibular hinge axis through the use of a double recording stylus. J Prosthet Dent 60:553-559, 1988 Schalhorn , R. G. A study of the arbitrary center and kinematic center of rotation for facebow mounting. J Prosthet Dent 7: 162-169, 1957. Shafiullah RS, Ravichandran M, Sundar MK, Kamakshi V. Posterior Reference Points: A Simplified Classification. J Sci Dent 2019;9(1):9–12. Farias‐Neto A, Dias AH, de Miranda BF, de Oliveira AR. Face‐bow transfer in prosthodontics : a systematic review of the literature. Journal of oral rehabilitation. 2013 Sep;40(9):686-92. Singh S, Rehan S, Palaskar J, Mittal S. Hinge axis-location, clinical use and controversies. Journal of Research in Dentistry. 2017 Oct 3;4(6):158-61. Kanazawa M, Iwaki M, Arakida T, Minakuchi S. Digital impression and jaw relation record for the fabrication of CAD/CAM custom tray. Journal of prosthodontic research. 2018;62(4):509-13. Praveen P , Ragavendra Jayesh ; Facebow European Journal Of Molecular & Clinical Medicine Issn 2515-8260 Volume 7, Issue 4, 2020